INTERNAL COMBUSTION ENGINE (Machine-translation by Google Translate, not legally binding)

专利摘要:
The invention relates to an internal combustion engine comprising a first Brayton cycle comprising a MIEC membrane that separates the O2 from the air so that the suction air stream is free of N 2 ; a second Brayton cycle binary combined with the first Brayton cycle and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-fuel. The second Brayton cycle transmits mechanical energy as well as thermal energy from exhaust gases to the first Brayton cycle. The first cycle of Brayton provides the second cycle of Brayton O2 compressed from the MIEC membrane. By means of the present engine, the emission of NOx into the atmosphere is prevented by the separation of N2 in the MIEC membrane. (Machine-translation by Google Translate, not legally binding)
公开号:ES2751129A1
申请号:ES201930285
申请日:2019-03-28
公开日:2020-03-30
发明作者:Martinez Francisco José Arnau；Calvo Jesús Vicente Benajes；Martinez David Catalan；Fernandez José María Desantes；Gonzalez Luis Miguel Garcia-Cuevas；Alfaro José Manuel Serra；Cruz José Ramón Serrano
申请人:Consejo Superior de Investigaciones Cientificas CSIC；Universidad Politecnica de Valencia；
IPC主号:

专利说明:

[0001]
[0002] INTERNAL COMBUSTION ENGINE.
[0003]
[0004] Field of the Invention
[0005] The present invention relates to the field of internal combustion engines, and more specifically to an internal combustion engine that burns hydrocarbons and does not emit gases harmful to health.
[0006]
[0007] Background of the Invention
[0008] MIEC membranes
[0009] Mixed ion-electronic conduction membranes (MIEC) are a type of dense ceramic membranes, in which oxygen ions diffuse from one side to the other due to the properties of the crystalline structure due to a gradient of oxygen chemical potential between the two sides of the membrane. The selectivity of these membranes is 100% for oxygen. These membranes operate at elevated temperatures (typically in the 700-1000 ° C range) with high air pressures (1-2 MPa) fed into the retention side and vacuum into the permeation side, according to Air Products & Chemicals Inc. , which has resulted in a breakthrough in the commercialization of MIEC membrane technology for pure oxygen production.
[0010] The transport of the oxygen ion is simultaneous to the transport of electrons or electronic holes (electronic carriers), so the material must have sufficient electronic conductivity under the operating conditions of the membrane. The driving force responsible for the transport of oxygen through the membrane is the difference in oxygen partial pressure between both sides of the membrane. Thus, the flow of oxygen through a membrane is determined by the temperature and the partial pressure difference of the oxygen in addition to the thickness of the membrane.
[0011] Another crucial step in the oxygen separation process in ion transport membranes is gas exchange. As mentioned, transport through the selective separation layer consists of the diffusion of oxygen ions and electronic carriers. Therefore, two surface reactions are necessary, the first in which the gaseous oxygen adsorbs and is transformed into oxygen ions on the surface of the membrane exposed to the feed gases, generally compressed air, and a second, in which the oxygen ions transform into oxygen molecular and desorb. For various reasons, these transport steps can be limiting and cause decreased permeation flow through the membrane. Among the various possible reasons, the following can be highlighted: (1) the thickness of the selective separation layer is very small, so that diffusion through the solid is much faster than gas exchange. Normally, this critical dimension is called "characteristic length" and is the quotient between the diffusion coefficient and the kinetic constant of the surface gas exchange reaction under the operating conditions and composition of gases in contact with the membrane surface. ( 2) The membrane surface does not have appreciable catalytic activity for the oxygen activation reaction. (3) The gaseous atmospheres in contact with the surface or surfaces of the membrane do not favor the adsorption / desorption of molecular oxygen and its release through the reaction O2 2 e- ^ O ^-2 In industrially relevant processes, both the permeate and the feed usually present appreciable amounts of acid gases such as CO2 and SO2, which hinder this reaction since they passivate or inactivate the surface and they compete with the adsorption and reaction centers involved in the oxygen gas exchange reaction This pernicious effect is accentuated as the operating temperature of the process is decreased, especially below 850 ° C, and when the concentration of SO2 and CO2 is increased. Especially negative is the effect of SO2 gas, since concentrations above 5 ppm produce serious effects on the permeation of oxygen through the membrane.
[0012] The oxygen partial pressure difference between both sides of the membrane can be achieved through two actions: (a) increasing the air pressure through compression stages; and / or (b) decreasing the partial pressure of oxygen in the permeate, which is possible by applying a vacuum, diluting the oxygen in the permeate by a entrainment gas stream, or consuming the oxygen in the entrainment chamber. This last option usually consists of recirculating the exhaust gases from the combustion furnace or boiler, at the same time increasing the operating temperature. Also, in line with the second option, it is possible to pass a reducing gas (generally methane or other hydrocarbons) that consumes the oxygen that penetrates through the membrane to give complete or partial combustion products and to release heat directly in contact with the membrane ceramics.
[0013] To understand MIEC membranes, 5 classification criteria are usually used based on crystal structure, phase composition, chemical composition, geometry, and dense layer configuration.
[0014] Considering its crystalline structure, MIEC membranes can be classified in perovskites, membranes derived from advanced perovskites and fluorites. Most MIEC membranes have a perovskite-like crystal structure (ABO3), where A is a large cation and B is a smaller cation. A perovskite is a crystal lattice made up of BO ⁶ octahedra with A ions located in 12 interstices. Some MIECs have a perovskite-like crystal structure, such as those of Ruddlesde-Popper (RP) with a formula of An + iBnO3n + i (n = 1, 2, 3, ...). The crystal structure of this phase is similar to that of perovskite in that a number of perovskite blocks (n) have a shared corner with the AO layer modified BO ⁶ octahedron along the c axis. Some MIECs have a fluorite structure, the typical example being CeO2 based materials.
[0015] If the membranes have only one type of crystalline phase, it is called monophasic membranes. Most perovskite membranes are monophasic, for example Lai-xSrxCoi-yFeyO3-5 (0 <x <1; 0 <y <1). If the membrane has two phases and both contribute to oxygen permeation, it is called dual phase membranes. An example is YSZ-Pd membranes, which contain a fluorite, YSZ, for the transport of oxygen ions and a metal phase, Pd, for the transport of electrons. If the membrane has two or more phases and only one contributes to oxygen permeation, this is a composite material. The inert phase is added to improve some property of the material (mechanical resistance, for example). For example, the SrCoo.8Feo.2O3-s-SrSnO3 composite comprises two perovskites where the SrSnO3 phase is inert with respect to oxygen permeation, but improves the mechanical properties of the membrane.
[0016] Early in the development of perovskite-type membranes, studies focused on those incorporating Co at the site of crystalline position B because Co-based membranes have high oxygen conductivity (for example, in Bao.5Sro .5Coo.8Feo.2O3-s). However, cobalt cations can easily be reduced to a lower valence state due to weak Co-O bonds which is unstable in reducing environments. Therefore, Co-free perovskites have been developed. For example, BaCeo.o5Feo.95O3-s exhibits lower oxygen conductivities compared to the respective Co-based perovskite, but exhibits high stabilities even in H2 at elevated temperatures.
[0017] The most common geometries are flat, tubular and hollow fiber membranes. Finally, considering the configuration of the dense layer, we speak of self-supporting when the membranes are composed of a single membrane layer that has enough thickness to support the integrity of the membrane, and asymmetric when the dense membrane layers have a porous layer that allows use smaller thicknesses since the integrity of the membrane is supported by the porous layer.
[0018] For practical use, high temperature oxygen separation membranes through ion transport are generally made up of the following components:
[0019] i. A porous support, generally made either of the same material from which the separation layer is made or of a material (ceramic or metal) compatible with the separation layer. Compatible means that it has a similar expansion profile as a function of temperature and that a reaction between both phases does not take place at high temperatures to give rise to third phases, which generally result in degradation and rupture of the membrane. The support porosity is usually between 20 and 60%, and its thickness is variable, normally below 2 mm.
[0020] ii. A non-porous layer or film is placed on the porous support, preferably with a thickness of less than 150 ^ m. This layer is made up of oxides or mixtures of oxides and allows the simultaneous transport of oxygen ions and electronic carriers through it.
[0021] iii. On the non-porous layer there is adhered a porous layer with a thickness preferably between 100 and 10 ^ m, made of a material that has mixed ionic and electronic conductivity as well as catalytic activity for the adsorption / desorption of oxygen and its dissociation and ionization . This catalytic layer allows to improve the processes of incorporation and elimination of gaseous oxygen. In some cases, there is an additional porous catalytic layer between the porous support and the non-porous separation layer that has the function of improving the gas exchange steps, especially when the porous support does not possess catalytic activity nor does it allow to carry out the transport of oxygen ions or electronic carriers. Generally, the properties of the porous support and the additional porous catalytic layer are quite similar, although the specific surface area of the porous support is generally higher.
[0022] Optionally, an additional non-porous layer (v) may also be required. This layer would be located between the non-porous layer and the porous layer, and would serve as protection for the separation layer against possible interactions or degradation reactions in contact with layer (iii) or with gases in contact with the porous layer. This additional layer must allow the transport of oxygen ions and oxygen carriers while being thermo-chemically compatible with the adjacent layers and with the gases with which it is in contact.
[0023] Oxy-fuel
[0024] Oxy-fuel consists of using a stream of high purity O2 as an oxidizer instead of air, as is done in conventional combustion processes, thus achieving higher flame temperatures with less fuel consumption and thus improving the combustion. The use of oxygen-rich oxidizers makes it possible to obtain combustion gases with a composition consisting mainly of CO2 and water vapor. The high CO2 concentration of the exhaust gases in the oxy-fuel process facilitates its potential separation (see, for example, documents US20070175411A1, US20070175411A1, US9702300B2, CN102297025A).
[0025] Silicone or polysulfone-based oxygen membranes can also be applied in air enrichment, so that the oxygen concentration is increased from 21% to higher values, usually above 24%.
[0026] Oxy-fuel aims to be one of the most economical technologies for CO2 capture, its main drawback being the high demand for O2 that it presents and the cost that obtaining it entails. The great challenge of this technology lies in the production of O2 in order to supply the high quantities required.
[0027] In membrane reactors, membranes are introduced for the following purposes: selective reagent extraction, catalyst retention, dosing of a reagent, catalyst support. All this entails increases in the efficiency of the reactions in systems limited by the thermodynamic equilibrium, avoiding secondary reactions, protecting the catalyst from possible compounds that deactivate it, etc.
[0028]
[0029] CO2 membranes
[0030] Currently there are a wide variety of materials that allow the selective passage of CO2. These materials range from advanced polymers to different types of inorganic materials. Despite this differentiation, there are combinations of these materials in the so-called mixed matrix membranes that generally consist of polymeric matrices with inorganic particles dispersed in the matrix. This type of technology provides flexibility to the capture of CO2 allowing to act before or after combustion. However, this type of materials generally presents permeability to more gases, for example, N2, O2, H2, etc. For this application it is necessary that the majority permeability is to CO2, and, additionally, that the permeability to O2 and N2 is very low. For the separation of CO2 from the rest of the gases there are various technologies:
[0031] to. CO ² separation technology using polymeric membranes There are different polymers that allow the selective separation of CO ² from a gas stream. The application of polymers to CO ² capture is economically attractive due to the low cost, ease of synthesis and processing of polymers, but they are generally limited materials due to their chemical, mechanical and thermal stability and their low permeability. A standard upper limit of 50 has been established for CO ² / N ² cross selectivity. Generally, this type of materials works at low temperatures and intermediate pressures (1 - 5 bar):
[0032] Among the different polymers available, the following should be highlighted: (i) crosslinked polyethylene oxides (XLPEO) with permeabilities of 420 barrers and selectivity for CO ² / CH ⁴ from 18 to 35 ° C (sweep = 10-10 cm3 (STP) cm / (cm2 s cmHg)), (ii) based on polyamides, such as Pebax, which has 132 barrers and CO ² / N ² selectivities of approximately 6 to 25 ° C and 3 atm, (iii) based on polyamides (PVAm) with permeabilities 41-104 GPU with CO ² / N ² selectivity in the range 100-197 at 25 ° C and 2 atm using wet mixtures of CO ² and N ² (GPU = 10-6 cm3 (STP) / (cm2scmHg)). Among others, Polaris ™ and Polyactive products are commercial examples of this technology.
[0033] It should be noted that high selectivity is required for the separation of CO ² from air, since the concentration of CO ² in air is approximately 0.035% and that of N ² is 78%.
[0034]
[0035] b. CO ² separation technology using inorganic membranes Considering apart the membranes based on molten carbonates, in the group of membranes based on inorganic materials for the separation of CO ² from gas streams are metallic membranes (based on Pd), membranes based on silica, carbon membranes and zeolite-based membranes.
[0036] The metallic membranes are based on palladium and its alloys. These materials have high H ² permeabilities. Therefore, they are mainly used for H ² separation in pre-combustion systems. These types of membranes are a mature technology for pre-combustion CO ² capture systems. However, the stability of these materials must be improved for their implementation in industrial systems.
[0037] Porous inorganic membranes (silica based membranes, zeolites, organometallic (MOF) and carbon membranes) can be applied to the separation of CO2.
[0038] Zeolites are aluminosilicates characterized by a homogeneous porous structure and a minimum channel diameter. The separation in these materials occurs by surface diffusion or molecular sieving. Three separation regimes are distinguished: (i) when the molecules have similar but different size adsorption forces, where the smaller molecules penetrate more easily; (ii) when the molecules have different adsorption forces and similar sizes, where the membrane is selective to the molecule that has higher adsorption forces; (iii) when the molecules have different sizes and adsorption forces, where the mechanism is a combination of the competitiveness between the adsorption forces and the diffusivity. In this way, the CO2 / N2 and / or CO2 / CH4 selectivities can be maximized at low temperatures by separating the gases by the third regime, or at high temperatures by the first regime. Zeolites include ZSM-5 with CO2 / N2 selectivities of 9.5 to 303 K (-263.65 ° C to 29.85 ° C) and a CO2 permeability of 3-10 ^"7 mol / (m ² sPa) and Y-type zeolites with CO2 permeabilities of 410 ^-7 mol / (m ² sPa) and selectivities of 100 and 21 for CO2 / N2 and CO2 / CH4, respectively at 303 K (29.85 ° C).
[0039] Silica-based membranes have great potential for CO2 / N2 and H2 / CO2 separation, due to their high chemical, thermal and mechanical stability in different atmospheres and conditions. The behavior of this type of membrane is highly conditioned, among other factors, to its synthesis method. The permeabilities are in the range of 310 ^-10 - 510 ^-7 mol / (m ² sPa), reaching selectivities of 60 for CO2 / N2, 325 for CO2 / CH4 and 670 for CO2 / H2 depending on the type of silica, synthesis method and conditions.
[0040] Carbon membranes, made of high carbon amorphous microporous materials, have emerged as promising materials for gas separation applications due to their thermal resistance, chemical stability in corrosive environments, high gas permeability and excellent selectivity compared to polymeric membranes. Considering the CO2 separation, these materials achieve selectivities of 100 for CO2 / CH4 with CO2 permeabilities of 2000 - 10,000 barrers, and selectivities of 10 for CO2 / N2 with CO2 permeabilities of 5 barrers.
[0041]
[0042] c. CO2 separation technology using membranes based on molten carbonates
[0043] Using materials similar to ion conduction ceramics (oxygen) electronic materials have been developed based on molten carbonates that allow the selective passage of CO2. However, these types of membranes are still far from industrial applications due to the low CO2 fluxes observed in the different works published to date.
[0044]
[0045] Alternative internal combustion engines
[0046] Alternative internal combustion engines represent the most important technology for land and marine vehicles for both heavy and passenger transport. Both its design and its auxiliary machinery (turbomachinery; fuel injection systems; additional pumps and heat exchangers) have been thoroughly optimized over the past century for various types of fuel. 4-stroke reciprocating engines lead ground transportation for their high specific power, their ability to comply with various regulations on polluting gaseous and acoustic emissions, and their low average specific consumption.
[0047] However, the need to limit CO2 emissions or even remove atmospheric CO2 and the need to improve air quality in overcrowded urban environments are pushing the technological limits of these engines with the current concepts of combustion and renewal of the load of the engines. themselves.
[0048]
[0049] Oxy-fuel in engines
[0050] Integrating an oxy-fuel system in a vehicle engine magnifies the exposed advantages (higher efficiencies and reduced emissions), but complicates the way to produce oxygen since space is limited to the dimensions of the vehicle. Considering engines that use oxygen as an oxidant, several alternatives have been proposed:
[0051] (i) Store oxygen in the vehicle. This system locates the problem of oxygen generation outside the vehicle, which only requires having space inside the vehicle for the oxygen storage system. Several studies have proposed storing oxygen in the vehicle in liquid form to reduce space (see documents CN201835947U and DE3625451A1, among others). However, this would increase the cost of oxygen and a storage system that would require low temperatures to keep oxygen in the liquid phase. Other studies have raised the idea of storing compressed oxygen in tanks inside the vehicle (US 3425402). In spite of everything, this type of solution would require generating oxygen elsewhere, so in addition to the expense of the storage system (both in the liquid phase as in the gas phase), the operating cost of oxygen should be considered. Considering all these extra costs, a priori this alternative would not be feasible and an improvement in current technology with respect to oxygen generation and storage would be necessary.
[0052] (ii) Generate oxygen from alternative sources to air. US 3709203 describes the generation of oxygen from a thermal decomposition of an alkali metal perchlorate, according to US 3961609A oxygen is generated by electrolysis of water, and according to US2775961A from hydrogen peroxide. However, due to the high oxygen demands that these systems need, it seems unlikely that integrating any of these solutions to a vehicle engine will be viable and competitive with respect to current technology.
[0053] (iii) Generate oxygen from the air:
[0054] to. Introducing filtering systems (US 3961609A) or PSA adsorption (WO 2005083243). This type of solution has the drawback that very large systems would be required to satisfy the oxygen demand.
[0055] b. Using membranes based on silicones or polysulfones (documents US20030024513A1, US5636619A, US5678526, US5636619, US2006 / 0042466A1, CN101526035A). However, these types of systems have been proposed to a greater extent for the enrichment of oxygen in the air than for the generation of pure oxygen, so that the membrane areas necessary to achieve an acceptable degree of purity for the process would render the process unfeasible. process.
[0056] c. Using membranes based on ceramic conductors. (c1) Using an electrochemical cell using an oxygen ion-conducting ceramic electrolyte (US 20090139497A1); however, this system would require a demand for electrical energy that should necessarily be removed from the motor, thus reducing the efficiency of the system. (c2) Using oxygen ion and electronic mixed conduction membranes (US20130247886A1) where oxygen is selectively separated from the air stream. This process requires large amounts of heat to keep the temperature around 700-1000 ° C. For this, this system uses the heat from the engine exhaust gases.
[0057]
[0058] Summary of the invention
[0059] The present invention aims to provide an internal combustion engine that provides advantages with respect to the state of the art previously described. More particularly, the present invention discloses an internal combustion engine as defined in appended claim 1, which reduces pollution by reducing, or even preventing, the emission of NOx into the atmosphere.
[0060] Additional embodiments of the motor of the present invention are disclosed in the dependent claims, providing additional advantages over the prior art.
[0061] More specifically, in its broadest aspect, the present invention discloses an internal combustion engine, of the type that sucks in atmospheric air as an oxidizer and uses hydrocarbons as a fuel, comprising:
[0062] - a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with reheating, by mixing a part of the nitrogen, which comprises a MIEC membrane that separates the O2 from the compressed air, so that the air stream sucked it is free of N2, and depleted air from the rejection of the MIEC membrane is sent directly to an exhaust gas stream avoiding its participation in a subsequent combustion, in which part of the air compressions are carried out in at least a first engine cylinder; - a second Brayton cycle with compression with intermediate cooling, binary combined with the first Brayton cycle (giving it heat) and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-combustion in at least a second cylinder of the engine, in which the second Brayton cycle transmits mechanical energy to the first Brayton cycle by coupling the at least one first cylinder with the at least a second cylinder through a crankshaft, as well as thermal energy from exhaust gases ;
[0063] wherein the first cycle of Brayton provides the second cycle of compressed Brayton O2 from the MIEC membrane;
[0064] whereby the emission of NOx into the atmosphere is avoided by the separation of N2 in the MIEC membrane.
[0065] As will be readily understood by one skilled in the art, when it is mentioned herein that an engine "comprises a first Brayton cycle", and the like, this should be interpreted as meaning that the engine "comprises means necessary to carry out a first Brayton cycle ”. In such cases, it is not intended to limit the present invention to any specific combination of media, and should It will be understood that any suitable means for carrying out said Brayton cycle (or the like) is encompassed by the present invention.
[0066] According to another aspect, the present invention also discloses an internal combustion engine operating method, of the type that sucks in atmospheric air as an oxidizer and uses hydrocarbons as fuel, the method comprising:
[0067] - a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with reheating, by mixing a part of the nitrogen, which comprises separating the O2 from the compressed air, so that the suction air stream is free of N2 , and an impoverished air coming from the rejection of the separation is sent directly to a stream of exhaust gases avoiding its participation in a subsequent combustion;
[0068] - a second Brayton cycle with compression with intermediate cooling, binary combined with the first Brayton cycle (giving it heat) and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-fuel,
[0069] in which the second Brayton cycle transmits mechanical energy as well as thermal energy from exhaust gases to the first Brayton cycle;
[0070] wherein the first Brayton cycle provides the second cycle of Brayton O2 compressed from separation;
[0071] whereby the emission of NOx into the atmosphere is avoided by the separation of N ² .
[0072] As will be described in more detail hereinafter, the present invention integrates membranes based on electronic ion and oxygen mixed ceramic conductive materials so that all the energy required for the MIEC membrane for separating O2 from the main source of residual heat (such as exhaust gases at the cylinder outlet) and takes advantage of the temperature increases offered by oxy-fuel to supply the membrane with the necessary temperature without wasting heat. It is also intended to take advantage of the high compression capacity of the cylinders of the alternative motors (up to 25 MPa) to achieve the ideal pressure conditions. High pressures are required for the following processes, which are provided in at least some of the preferred embodiments according to the present invention: maximize the partial pressure difference between air and O2 to maximize productivity of the O2 membrane; maximize the separation of atmospheric CO2 from air; and finally, compress until the CO2 is liquefied (exceed its critical pressure of 7.5 MPa).
[0073] The turbomachines of engine supercharging systems are not used in the present invention for the compression process of the air before its separation nor for the densification of CO ² (unlike US20130247886A1) due to the low compression ratios that they provide (maximum pressure less than 0.6 MPa at sea level). There are no developments of turbochargers in turbogroups for pressures above 0.6 MPa, and they are very inefficient in the vicinity of these values.
[0074] The temperature associated with air compression in turbochargers (also unlike US20130247886A1) is also not used due to the much lower efficiency of isentropic and irreversible compression processes compared to isotherms. Now, in the present invention, the compressed air is always cooled before going to the next compression stage so that the process is as isothermal (and therefore more efficient) as possible. This is done either with heat exchangers that use water to cool the air load (commonly WCAC), or with vacuum Brayton cycles that convert heat to pressure (CBV). Both CBV and WCAC remove heat from the fluid and transmit it to the environment before the next compression, which, although it seems an energy expenditure, is actually a gain that pays off in that next compression stage. It is even sought to achieve the maximum compression ratio, mechanically possible, within the cylinders of the four-stroke engine, since when the air compression process is carried out in four strokes, the air remains long in the cylinders, contributing that residence to its cooling against engine coolant. This cooling of the high pressure air makes the process closer to the isotherm and again more efficient. This innovative use of all four engine strokes, without combustion in those cylinders, is first described in this document.
[0075] The ultimate reason for the search for maximum energy efficiency in all processes is to obtain an oxy-fuel engine / propeller group that has at least some of the following characteristics: that it does not emit or emits small amounts of polluting gases; that traps the CO ² produced in the combustion and removes all or part of the atmospheric CO ² from the environment; that it is compact and light to be able to transport itself and; Lastly, that it is competitive with current internal combustion engines in terms of fuel consumption.
[0076] To achieve this last objective, the present invention describes, in some of its preferred embodiments, a completely new engine load regulation system. This prevents throttle throttle flow to regulate engine load on ignition ignition (SI) engines with oxy-fuel mixture homogeneous. This is done using turbogroups, not to supercharge the combustion cylinders (as proposed in US20130247886A1), but to supercharge the cylinders that compress the air before the membranes and use the regulation of the O2 production of the MIEC to regulate the load. Avoiding the use of the throttle eliminates the pumping losses of the premixed combustion SI motors during the regulation of their load, which is the main inefficiency of these. The second inefficiency that is avoided, with oxy-combustion, in premixed combustion SIs is the enrichment of the mixture (beyond stoichiometric dosing: A, <1) to control the temperature of the exhaust gases. This temperature control is performed in the present invention by diluting the O2-fuel mixture with the pure CO2 used to sweep the O2 side in the MIEC instead of with the fuel. The proposed arrangement of the turbogroups and the MIEC allows both the control of the O2 production rate and the control of its CO2 dilution rate to be carried out independently. This arrangement of turbomachines and membrane allows both controls to be carried out more efficiently than those described up to now in the state of the art, since pressure control is carried out by expanding the flow in the turbines; instead of inefficient pressure lamination in regulating valves (the latter is what has been proposed, for example, in US20130247886A1).
[0077] Furthermore, the present invention proposes in some of its preferred embodiments to use liquid CO2 during the combustion cycle of the alternative engine. This allows to recover a large part of the energy necessary to liquefy the CO2 in a supercritical motor cycle with this fluid that works simultaneously and conjugated with the O2 cycle. Both cycles share some of their processes, fundamentally the increase in the thermal state and the expansion of the fluid. Neither the supercritical cycle of CO2 explained here, nor the conjugated cycle of O2, with which it shares some of its processes, have been described by sources prior to the present invention.
[0078] During the liquefying of the CO2, in order to later store it and transfer it to the relevant processing centers, a percentage (of around 2% of the total mass of the transferred substance) of liquid water is produced, which must necessarily be separated from the CO2. As a further difference of the present invention with respect to document US20130247886A1, the high pressure separated water is energetically valorized expanding in a vapor state in one of the turbines. This use has the virtue, on the one hand, of emitting water in the form of steam against a liquid stream and; on the other hand, to reduce energy consumption to achieve the necessary air pressure in the O2 separation membranes.
[0079] Brief description of the drawings
[0080] The present invention will be better understood with reference to the following drawings which illustrate preferred embodiments thereof, provided by way of example, and which are not to be construed as limiting the invention in any way:
[0081] Figure 1 shows a diagram of a premixed oxy-fuel engine according to a first preferred embodiment of the present invention, with homogeneous and stoichiometric mixing, of high specific power, high efficiency, with MIEC to separate O2 from the air, without emission of harmful gases for health but with positive net CO2 emissions.
[0082] Figure 2a shows a diagram of a premixed oxy-fuel engine according to a second preferred embodiment of the present invention, with homogeneous and stoichiometric mixture, of high specific power, high efficiency, without emission of gases harmful to health, with MIEC to separate the O2 from the air, with a polymeric membrane to separate CO2 and with negative net CO2 emissions.
[0083] Figure 2b shows a diagram of a premixed oxy-fuel engine according to an alternative to the engine shown in Figure 2a, with homogeneous and stoichiometric mixture, of high specific power, high efficiency, without emission of gases harmful to health, with MIEC to separate O2 from the air, with a membrane based on molten carbonates to separate CO2 from the air and with negative net CO2 emissions.
[0084] Figure 3 shows a diagram of a diffusion oxy-fuel engine according to a third preferred embodiment of the present invention, with stratified and lean mixture, of high specific power, high efficiency, with MIEC to separate O2 from the air, without emission of gases harmful to health but with positive net CO2 emissions.
[0085] Figure 4a shows a diagram of a diffusion oxy-fuel engine according to a fourth preferred embodiment of the present invention, with stratified and lean mixture, of high specific power, high efficiency, without emission of gases harmful to health, with MIEC to separate O2 from the air, with a polymeric membrane to separate CO2 from the air and with negative net CO2 emissions.
[0086] Figure 4b shows a diagram of a diffusion oxy-fuel engine according to an alternative to the engine of figure 4a, with stratified and lean mixture, of high specific power, high efficiency, without emission of gases harmful to health, with MIEC to separate O2 from the air and a membrane based on molten carbonates to separate CO2 from the air and with negative net CO2 emissions.
[0087] Figure 5a shows a schematic of the vacuum Brayton cycle (CBV).
[0088] Figure 5b shows an idealized and calculated Brayton cycle vacuum (TsV) Ts diagram for a specific situation.
[0089] Figure 6 shows a supercritical CO2 cycle nested with the O2 Diesel cycle, corresponding to embodiment 4 of Figures 4a and 4b.
[0090] Figure 7 shows a nested O2 Diesel cycle with the intermediate cooling compression Brayton cycle corresponding to Embodiment 4 of Figures 4a and 4b.
[0091] Figure 8 shows a graph of the combustion temperature regulation for different degrees of charge and based on the EGR rate; this is for a motor according to the embodiment of figure 1.
[0092] Figure 9 shows a graph of the efficiency of the MIEC during the regulation of the combustion temperature for different degrees of load; this is for a motor according to the embodiment of figure 1.
[0093] Figure 10 shows a graph of the effective torque at full load and at partial loads for a motor according to the embodiment of figure 1.
[0094] Figure 11 shows a graph of the specific consumption at full load and at partial loads for a motor according to the embodiment of figure 1.
[0095] Figure 12 shows a graph of the effective power at full load and at partial loads for a motor according to the embodiment of figure 1.
[0096] Figure 13 shows a graph of the cycle results within the combustion cylinder for an engine according to the embodiment of Figure 1.
[0097]
[0098] Detailed description of the preferred embodiments
[0099] As mentioned above, the present invention discloses an internal combustion engine, of the type that sucks in atmospheric air as an oxidizer and uses hydrocarbons as a fuel, comprising:
[0100] - a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with reheating, by mixing a part of the nitrogen, comprising a MIEC membrane (6) that separates the O2 from the compressed air, so that the current suction air is free of N2, and depleted air from the rejection of the MIEC membrane (6) is sent directly to an exhaust gas stream avoiding its participation in a subsequent combustion, in which part of the air compressions is they make in at least a first cylinder (4), preferably two first cylinders (4), of the engine;
[0101] - a second Brayton cycle with compression with intermediate cooling, binary combined with the first Brayton cycle and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-fuel in at least a second cylinder (14), preferably two second cylinders (14), of the engine,
[0102] wherein the second Brayton cycle transmits mechanical energy to the first Brayton cycle by coupling the at least a first cylinder (4) with the at least a second cylinder (14) through a crankshaft (25), as well as energy thermal from exhaust gases;
[0103] wherein the first cycle of Brayton provides the second cycle of compressed Brayton O2 from the MIEC membrane (6);
[0104] whereby the emission of NOx into the atmosphere is avoided by the separation of N2 in the MIEC membrane (6).
[0105] According to a preferred embodiment, the net mechanical energy produced by the first Brayton cycle is used to supercharge the second Brayton cycle through a C1 compressor (10).
[0106] According to another preferred embodiment, the MIEC membrane (6) produces pure O2 separated from atmospheric air. The term "pure" (eg, applied to some gaseous stream, such as "pure O2") should not be construed herein in a strictly limiting sense. For example, in this case, the produced O2 stream may not be 100% pure, but also contain some lesser amount of CO2, for example. However, this stream of pure O2 (or substantially pure O2) has been separated from N2, so that NOx production in a subsequent oxy-fuel, and therefore the emission of said NOx into the atmosphere.
[0107] According to another preferred embodiment, the MIEC membrane (6) produces O2 diluted with CO2. The CO2 with which the O2 is diluted in this case can either be obtained from atmospheric air, or produced by combustion with hydrocarbon in the second Brayton cycle.
[0108] According to another preferred embodiment, there is always a cooling stage after each compression stage.
[0109] According to another preferred embodiment, heat is recovered from all residual sources by combining the first and second Brayton cycles by performing regenerations before each cooling.
[0110] According to another preferred embodiment, the mechanical energy produced by the second Brayton cycle is further used to compress produced CO2 to liquefy it. Said CO2 can be compressed, for example, to at least 7.5 MPa. Furthermore, the second Brayton cycle can be nested with an Otto cycle, and the engine comprises at least one additional piston (22) as well as non-return valves (a first non-return valve (33) at the inlet and a second non-return valve (19 ) downstream of it) to suck up and compress excess CO2 accumulated in engine ducts.
[0111] According to another alternative of this last preferred embodiment, the second Brayton cycle is nested with a Diesel cycle, and the exhaust stroke of the second cylinders (14) is used to compress the CO2, through the use of first and second non-return valves ( 33, 19) that allow the discharge of CO2 and the admission of substantially pure O2. This substantially pure O2 is used as stripping gas in selective CO2 separation membranes.
[0112] According to another preferred embodiment, the engine further comprises a vacuum Brayton cycle (CBV) to cool down substantially pure O2, or CO2 diluted O2, before further compression.
[0113] According to another preferred embodiment, the engine comprises a first tank (20) for storing liquefied CO2 produced. Said CO2 stored in the first tank (20) can be used to pump fuel from a second tank (27) to the second cylinders (14) of the engine, both first and second tanks (20, 27) being in the same tank separated by a flexible diaphragm (replacing the low pressure pump used in "common rail" injection systems; which are the most widespread of current compression ignition engines) and / or can be transferred to a dispenser on a network external CO2 logistics.
[0114] According to another preferred embodiment, the MIEC membrane (6) is based on crystalline ceramic materials that have mixed conduction of electronic carriers and oxygen ions.
[0115] According to another preferred embodiment, in which the engine is of the type of caused ignition (SI), turbogroups are used to supercharge the first cylinders (4) and the regulation of the production of O2 of the MIEC membrane (6) is used to regulate engine load.
[0116] According to another preferred embodiment, in which the engine is of the compression ignition (CI) type, turbogroups are used to supercharge the first cylinders (4) and the regulation of the production of O2 of the MIEC membrane (6) is used to regulate the effective compression ratio of the working fluid in the engine cycle.
[0117] In another aspect, the present invention discloses an internal combustion engine operating method, of the type that sucks in atmospheric air as an oxidizer and uses hydrocarbons as a fuel, the method comprising:
[0118] - a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with reheating, by mixing a part of the nitrogen, which comprises separating the O2 from the compressed air, so that the suction air stream is free of N2 , Y depleted air from the rejection of the separation is sent directly to a stream of exhaust gases, preventing its participation in subsequent combustion;
[0119] - a second Brayton cycle with compression with intermediate cooling, combined in a binary way with the first Brayton cycle and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-fuel,
[0120] in which the second Brayton cycle transmits mechanical energy as well as thermal energy from exhaust gases to the first Brayton cycle;
[0121] wherein the first Brayton cycle provides the second cycle of Brayton O2 compressed from separation;
[0122] whereby the emission of NOx into the atmosphere is avoided by the separation of N2.
[0123] According to a preferred embodiment of the method, the net mechanical energy produced by the first Brayton cycle is used to supercharge the second Brayton cycle.
[0124] According to a preferred embodiment of the method, the first Brayton cycle produces pure O2 separated from atmospheric air. Alternatively, the first Brayton cycle produces O2 diluted with CO2. In this case, the CO2 with which the O2 is diluted can be obtained from atmospheric air or can be produced by combustion with hydrocarbon in the second Brayton cycle.
[0125] According to a preferred embodiment of the method, there is always a cooling stage after each compression stage.
[0126] According to a preferred embodiment of the method, heat is recovered from all residual sources by combining the first and second Brayton cycles by regenerating before each cooling.
[0127] According to a preferred embodiment of the method, the mechanical energy produced by the second Brayton cycle is further used to compress produced CO2 until liquefied. For example, CO2 can be compressed to at least 7.5 MPa. Furthermore, the second Brayton cycle may be nested with an Otto cycle, and the method involves sucking up and compressing excess CO2 accumulated in engine ducts.
[0128] According to another alternative, the second Brayton cycle is nested with a Diesel cycle, and the method involves compressing the CO2, allowing the discharge of CO2 and the admission of substantially pure O2, the latter being used as entrainment gas in selective separation membranes of CO2.
[0129] According to a preferred embodiment, the method further comprises a vacuum Brayton cycle (CBV) for more intensive cooling of substantially pure O2, or O2 diluted with CO2, before subsequent compression.
[0130] According to a preferred embodiment, the method comprises storing produced liquefied CO2. Said liquefied CO2 can be used to pump fuel into the engine's cylinders and / or can be transferred to a supplier of an external CO2 logistics network.
[0131] A detailed description of preferred embodiments of the present invention is provided below with reference to the accompanying figures, in order to further illustrate, and not limit, the teachings disclosed by the present invention.
[0132]
[0133] Embodiment 1: Premixed Mixture Induced Ignition Engine (SI) without polluting gas emissions and without CO2 capture
[0134] Embodiment 1 is indicated for premixed (homogeneous) mixed ignition (SI) engines without CO2 capture. Embodiment 1 is based on a deflagration combustion process, with subsonic speed and without self-ignition of the mixture, for the production of net mechanical power.
[0135] The degree of load (percentage of maximum torque) of the motor is controlled by the O2 production rate in the MIEC membrane (6). This reduces pumping losses by eliminating the use of butterfly valves to throttle the air flow.
[0136] The combustion temperature is controlled by diluting the mixture of oxidizer (O2) and fuel (HxCyOz) with CO2 and H2O from the combustion itself and pre-cooling. This avoids the use of fuel for this task (standard practice in current SI).
[0137] In embodiment 1 it is not proposed to capture the CO2 emitted by the engine. But it provides an improvement in energy efficiency compared to current SI engines and eliminates emissions of polluting gases (CO, THC, PM and NOx) at source (combustion chamber) and on the MIEC membrane (6), minimizing the need post-treatment to clean the exhaust gases, which represents a considerable saving in the production cost of the engine. At present it is estimated that the post-treatment for gas cleaning is of the order of 30% of the total cost of the motor-propulsion group. Furthermore, due to oxy-combustion, it is guaranteed that emissions of polluting gases are minimized during the cold start process. This does not happen in today's engines, due to the time required to heat (activate) the large after-treatment systems required for exhaust gas cleaning.
[0138] Embodiment 1 is shown in figure 1. In embodiment 1, atmospheric air enters the engine through a filter (1) sucked by a compressor (C2) (2). Compressor C2 (2) is part of a turbogroup and is mechanically coupled to a variable geometry turbine (VGT2) (8). Compressor C2 (2) discharges air using the energy recovered by the VGT2 turbine (8) from the N2, CO2 and H2O rejected in the MIEC membrane (6); and the CO2 and H2O not recirculated to the second cylinders (14) of the engine, which circulate through the duct that comes out of a catalytic MIEC membrane (15) and converge with the duct coming from the rejection of the MIEC membrane (6). Under nominal conditions, the air at the outlet of compressor C2 (2) has a pressure and a temperature of approximately 0.4 MPa and 473 K (199.85 ° C). The air passes through a first engine water cooler with water (in English: “water-cooler of air charge”, WCAC) (3). At the outlet of the first WCAC cooler (3), the temperature drops to approximately 323 K (49.85 ° C), which makes subsequent compression in the first cylinders (4) of the engine more isothermal.
[0139] Subsequently, the air is sucked through half of the first cylinders (4) of the engine. In embodiment 1 a 4-cylinder, 4-stroke engine is depicted, whereby 2 cylinders are sucking air. The first cylinders (4) act as pumps, compressing the air to approximately 0.9 MPa and 473 K (199.85 ° C). The first cylinders (4) are preferably identical to the rest of the engine's cylinders, sharing the crankshaft (25), the camshaft and the distribution, and having the only singularity that they are not injected with fuel. Being a 4-stroke engine, the air remains 4 strokes inside the first cylinders (4), which compresses and cools with the engine's cooling water (approximately 363 K (89.85 ° C)) which contributes to making the compression more isothermal. These first cylinders (4) work as a starting system for the set of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0140] At the exit of the first cylinders (4), the air is heated in a first regenerator (23), which lowers its pressure to 0.87 MPa and raises its temperature to approximately 573 K (299.85 ° C), using the thermal energy from a stream of CO2, H2O and N2. This flow of N2, CO2 and H2O exits through the conduit (30) located downstream of the VGT2 turbine (8). This flow of N2, CO2 and H2O represents approximately 100% of the total flow of gases transferred by the engine and is found at a temperature of approximately 800 K (526.85 ° C) and a pressure of 0.1 MPa. At the exit of the first regenerator (23) the air is heated in a second regenerator (5) that lowers its pressure to 0.85 MPa and raises its temperature to approximately 673 K (399.85 ° C), using the energy O2 thermal produced by the MIEC membrane (6) and the exhaust gases used to entrain the exchanged O2 in the MIEC membrane (6) and lower the O2 partial pressure in the entrainment chamber.
[0141] At the outlet of the second regenerator (5) the air is heated again in a catalytic MIEC membrane (15) (this membrane has a catalyst that favors the complete oxidation of CO and HC to CO2 and H2O with the surrounding O2), which lowers its pressure to 0.8 MPa and raises its temperature to approximately 723 K ( 449.85 ° C), using for this the thermal energy of the exhaust gases from the combustion of the second cylinders (14). In the catalytic MIEC membrane (15) the exhaust gases transfer their heat to the air (it acts as a regenerator) and both CO and HC are oxidized until the entire gas flow is composed solely of CO2 and H2O. This reduces the need for gas cleaning after-treatment of this engine to 20%, since this exhaust gas flow represents approximately 20% of the total flow of exhaust gases transferred by the engine. After the catalytic MIEC membrane (15) air at 0.8 MPa pressure enters the MIEC membrane (6) where it reaches the working temperature of the MIEC membrane (6) (approximately 1173 K (899.85 ° C)) thanks to the heat exchange with the exhaust gases that come from the oxy-fuel process of the second cylinders (14) and that are used to sweep the O2 exchanged in the MIEC membrane (6). This flow of exhaust gases that come from the oxy-combustion process of the second cylinders (14) represents approximately 80% of the exhaust gas flow.
[0142] The rejection of the MIEC membrane (6) is fundamentally N2 at 0.8 MPa and 1173 K (899.85 ° C); it represents approximately 80% of the gas mass transferred by the system and passes through a VGT1 turbine (71) or through a control valve (72). The VGT1 turbine (71) and the control valve (72) are part of a turbogroup together with the C1 compressor (10), to which the VGT1 turbine (71) is mechanically attached. The VGT1 turbine (71) energetically valorises the rejected N2 flow from the MIEC membrane (6), recovering its energy to move compressor C1 (10). The control valve (72) regulates the flow of energy to the compressor C1 (10). Compressor C1 (10) discharges a mixture of CO2, H2O and O2 that comes from the drag output of the MIEC membrane (6). Compressor C1 (10) discharges approximately 95% of the engine's gas flow. As a consequence, the control valve (72) regulates the flow of CO2 and H2O used to dilute the O2 and, therefore, the temperature of the combustion and of the combustion exhaust gases. In conclusion, the temperature of the engine exhaust gases, at the exit of the second cylinders (14), is regulated by the control valve (72); and it is at an approximate value of 1273 K (999.85 ° C) under nominal conditions.
[0143] Normally, the control valve (72) works partially open to regulate the pressure of the compressor C1 (10). A part of the rejected N2 in the MIEC membrane (6) circulates through the VGT1 turbine (71), expanding and cooling. The other part of the rejected N2 circulates through the control valve itself (72), without cooling. This other part of the N2 mixes downstream of the VGT1 turbine (71) with the cold and expanded N2, reheating it, and consequently increasing its temperature.
[0144] After passing through the control valve (72) and / or through the turbine (71), the rejection N2 of the MIEC membrane (6) (approximately 80% of the air flow) is mixed with the CO2 and H2O that come from the second non-return valve (19) and both flows are valorized in the VGT2 variable geometry turbine (8) that is used to move the compressor C2 (2). The approximate nominal conditions of entry to the VGT2 turbine (8) are 0.3 MPa and 873 K (599.85 ° C). The variable geometry of the VGT2 turbine (8) is used to regulate the degree of load of the combustion engine. When the VGT2 turbine (8) is closed, the air flow through the MIEC membrane (6) and the working pressure in the MIEC membrane (6) increases. Therefore, the hourly production of O2 and the amount of fuel that can be injected under stoichiometric conditions increases. The reverse is true when the VGT2 turbine (8) opens. The minimum size (minimum opening) of the VGT2 turbine (8) is chosen in accordance with the displacement of the reciprocating engine to set the maximum power of the system at each engine rotation speed. The maximum opening of the VGT2 turbine (8) determines the minimum load (idle) of the reciprocating motor at each speed. The VGT2 turbine (8) can also comprise a relief valve (or WG). When the VGT2 turbine (8) or its relief valve is opened to the maximum, the energy of the compressor C2 (2) is reduced to zero, which reduces both the working pressure of the MIEC membrane and the flow of air transferred.
[0145] If it is desired to further reduce the motor load, down to zero, then the control valve (72) is opened, avoiding the VGT1 turbine (71), thereby reducing the energy of compressor C1 (10) to zero. In this case, the flow of exhaust gases (where CO2 is found) to the MIEC membrane is stopped (6). This equalizes the partial pressure of O2 on both sides of the MIEC membrane (6) and stops the flow of O2 production by leaving the engine load of this embodiment 1 empty.
[0146] At the output of the VGT2 turbine (8) the mixture of N2, CO2 and H2O at a pressure of 0.1 MPa and a temperature of approximately 800 K (526.85 ° C), is passed through the first regenerator (23) to transfer its heat to the air before discharging this mixture of gases (free of gases harmful to health) into the atmosphere.
[0147] The mixture of O2, exchanged by the MIEC membrane (6), and of CO2 and H2O, used to drag and lower the partial pressure of O2, exit through the corresponding end of the MIEC membrane (6), towards the second cylinders (14 ) combustion, sucked by compressor C1 (10). This mixture comes out at a nominal pressure and temperature of approximately 0.3 MPa and 1173 K (899.85 ° C) respectively, and accounts for approximately 105% of the air flow transferred by the motor. The heat from the mixture of CO2, H2O and O2 is recovered first in the second regenerator (5) to heat the air at the outlet of the first regenerator (23). At the outlet of the second regenerator (5) it has nominal conditions of approximately 0.25 MPa and 673 K (399.85 ° C). This current is recovered in a variable geometry turbine (VGT3) (16) at the output of the second regenerator (5) that is used to move a compressor (C3) (12) mechanically coupled to another turbogroup. The C3 compressor (12) is used to supercharge the second cylinders (14), like the turbochargers in use, using the energy recovered by the VGT3 turbine (16). The VGT3 turbine (16) closes to keep the pressure at the outlet of compressor C3 (12) constant at a nominal value of 0.6 MPa in any engine operating condition. At the outlet of the VGT3 turbine (16) the nominal flow conditions are approximately 0.1 MPa and 473 K (199.85 ° C). The oxidizing mixture continuing into the second cylinders (14) is cooled in a second WCAC cooler (9) to 323 K (49.85 ° C). Next, compressor C1 (10) is compressed to 0.3 MPa and 473 K (199.85 ° C), with the conditions of compressor C1 (10) being imposed by the control valve (72) to maintain the temperature of exhaust gases around 1273 K (999.85 ° C), as already described. After compressor C1 (10), the mixture of CO2, H2O and O2 is cooled again to 323 K (49.85 ° C) in a third WCAC cooler (11) and compressed in compressor C3 (12) to 0 , 6 MPa and 473 K (199.85 ° C). For this, the energy of the VGT3 turbine (16) is used, which regulates the pressure at the outlet of compressor C3 (12) equal to 0.6 MPa, as already described. Finally, the mixture is re-cooled in a fourth WCAC cooler (13) to 323 K (49.85 ° C) before being sucked through the second cylinders (14), which in this embodiment are 2 because they are half of those of a 4-cylinder, four-stroke engine that has been used as an example; as stated at the beginning of the description of the present embodiment.
[0148] In the second cylinders (14), an HxCyOz hydrocarbon is injected, with a fuel pump (26), into the mixture of CO2, H2O and O2 in stoichiometric proportion with the O2. In said second cylinders (14) a triggered ignition premixed combustion cycle is performed and similar to the Otto cycle. The second cylinders (14) produce energy to move the first cylinders (4) that transfer the air to the MIEC membrane (6) since they are coupled to the same crankshaft (25). The second cylinders (14) produce a surplus of net mechanical energy that is used to move the vehicle to which the motor is coupled, or the electric generator or any application that requires a supply of mechanical energy through an axle. These second cylinders (14) also function as a starting system for the set of turbomachines, to start the air flow; of O2 and the turbomachines of the cycle. For this they move, until the system is started, by a conventional starter motor used in alternative motors. Thus, both the first cylinders (4) and the second cylinders (14) function as a starting system and are moved, until the system starts, by a conventional starter motor.
[0149] The transfers of heat to water from the first (3), second (9), third (11) and fourth (13) WCAC chillers plus the heat given up in the regenerations (produced in the first (23), second (5) regenerators and in the catalytic MIEC (15)) together with the discharge to the atmosphere of the surplus exhaust gases (that is, the non-recirculated exhaust gases), through the branch (29) and the second non-return valve (19) , suppose the total transfer of heat to the cold focus necessary for the proposed thermodynamic cycle to comply with the second principle of thermodynamics and, therefore, be viable. In turn, the heat transfers in the first (3), second (9), third (11) and fourth (13) WCAC chillers and in the regenerations (produced in the first (23), second (5) and The catalytic MIEC (15)) contribute to minimizing the exergy destruction of the thermodynamic cycle due, on the one hand, to making the overall compression process of the working fluid more isothermal and, on the other, to recovering the energy of the exhaust gases for the air separation. The approach to isothermal compression and the use of regenerators to extract heat from the gases in the system bring the N2 cycle, separated from the air in the MIEC membrane (6), to a cycle with the same performance as the Carnot cycle known as the Ericsson cycle . The CO2 + H2O + O2 mix cycle can be assimilated to a closed Brayton cycle with intermediate compressions and expansions, but nested with an Otto cycle in the second cylinders (14); something not described until now in the bibliography. In essence, the quasi-closed Brayton cycle nested with the Otto cycle and binary with the N2 cycle (by sending heat to the N2 cycle it complies with the thermodynamic precepts to approach an ideal cycle of maximum efficiency, such as the Ericsson cycle) is a novel embodiment binary cycle, which meets the precepts of the other ideal cycle of maximum efficiency, that of Carnot.
[0150] Finally, as a result of the combustion of the hydrocarbon (fuel) with the oxidizing mixture (CO2, H2O, O2), a mixture of CO2, H2O, and, to a lesser extent, THC, is produced at the outlet of the second cylinders (14). burn and CO.
[0151] The non-recirculated part of exhaust gases is bypassed by the branch (29) to be discharged at the entrance of the VGT2 turbine (8). This surplus represents approximately 20% of the exhaust gases, which are a mixture of unburned CO2, H2O, CO and total hydrocarbons (THC). Downstream of the branch (29) and upstream of the second non-return valve (19) is the catalytic MIEC membrane (15) into which the exhaust gases enter at a temperature of approximately 1273 K (999.85 ° C) and they yield their heat to 100% of the air flow that the motor raises, with which their temperature drops a lot, to approximately 623 K (349.85 ° C). At the same time, and due to the chemical reactions that take place in the catalytic MIEC membrane (15), the CO and THC are oxidized with the O2 left over from combustion to form H2O and CO2 vapor. Again, because oxy-fuel prevents the production of NOx in the second cylinders (14), the mixture of H2O and CO2 formed in the catalytic membrane (15) is free of harmful gases (without CO, without THC and without NOx) . Therefore, the mixture is discharged without any gas harmful to health.
[0152] Downstream from the catalytic MIEC membrane (15), the CO2 and H2O mixture is discharged through a second non-return valve (19) at the inlet of the VGT2 turbine (8). The second non-return valve (19) is calibrated at a pressure of approximately 0.11 MPa and serves to prevent air or N2 from entering the mixture of oxidizing gases during transitory processes. Upstream of the second non-return valve (19), a closed volume is therefore formed, separated from the atmosphere. This volume is made up of an N2-free duct circuit that acts as a system for accumulating oxidizing mixture of CO2 + H2O + O2 after the engine stops. This accumulated mixture facilitates the subsequent starting of the engine, since there is already a surplus of O2 produced by the MIEC membrane (6), which can be used to start the combustion in the second cylinders (14). The mixture of N2, CO2 and H2O is finally discharged into the atmosphere through the conduit (30) previously passing through the first regenerator (23) to extract its heat, as already described.
[0153] The rest of the non-excess exhaust gases (that is, the recirculated exhaust gases) represent approximately 80% of their flow. This non-excess mixture is sucked by compressor C1 (10), compressor C3 (12) and the second cylinders (14) themselves to pass through the MIEC membrane (6). In the MIEC membrane (6) the recirculated exhaust gases, on the one hand, fulfill the indirect function of sweeping and lowering the partial pressure of the O2 that passes through the membrane to improve the productivity of the MIEC membrane (6); on the other hand, it fulfills the direct function of reducing the proportion of O2 in the oxidizing mixture. In this way, the temperature of the combustion gases is controlled, around 1273 K (999.85 ° C), at the outlet of the second cylinders (14). In this way, at the exit of the MIEC membrane (6) the cycle is closed and the mixture returns to the entrance of the second regenerator (5) to transmit its heat to the air.
[0154] In the described process, the motor works efficiently both by keeping the dosing always close to the stoichiometric one and by regulating its load without throttling the flow, but modulating the air delivered by the C2 compressor (2) and the productivity of the membrane. O2 productivity responds instantaneously to engine accelerations as the first cylinders (4) are mechanically coupled on the same axis with the second cylinders (14). Therefore, the dynamic response of the engine does not suffer from the turbocharger-lag typical of turbocharged engines. Finally, the engine only emits a mixture of: CO2 and H2O into the atmosphere from the second non-return valve (19); and atmospheric N2, H2O and CO2 from the VGT2 turbine outlet (8). In other words, it does not emit any gas harmful to health that adversely affects the respiratory process of people and animals.
[0155]
[0156] Embodiment 2: Premixed ignition ignition (SI) engine without polluting gases and with CO2 capture produced and atmospheric CO2 removal Embodiment 2 is indicated for premixed (homogeneous) mixture ignition ignition (SI) engines with capture of atmospheric and produced CO2. Therefore, it falls within the category of engines that remove CO2 from the atmosphere (emission rate <0). Embodiment 2 is based on a deflagration combustion process, with subsonic speed and without self-ignition of the mixture, for the production of net mechanical power.
[0157] The degree of load (percentage of maximum torque) of the motor is controlled by the O2 production rate in the MIEC membrane (6). This reduces pumping losses by eliminating the use of butterfly valves to throttle the air flow.
[0158] The combustion temperature is controlled by diluting the mixture of oxidizer (O2) and fuel (HxCyOz) with CO2 and H2O from the combustion itself and pre-cooling. This avoids the use of fuel for this task (standard practice in current SI at high speed and maximum power).
[0159] Embodiment 2 proposes to capture the CO2 emitted by the engine and reduce the atmospheric CO2 content as efficiently as possible. In addition, it eliminates the emissions of polluting gases (CO, THC, PM and NOx) at the source (combustion chamber) or on the MIEC membrane, minimizing the need for post-treatment for cleaning the exhaust gases, which represents a considerable cost saving engine production. At present it is estimated that the post-treatment for gas cleaning is of the order of 30% of the total cost of the motor-propulsion group. Furthermore, due to oxy-combustion, it is guaranteed that no polluting gases are emitted during the cold start process. This does not happen in today's engines, due to the time required to heat (activate) the aftertreatment systems for exhaust gas cleaning.
[0160] Embodiment 2 has been represented in Figures 2a and 2b depending on the technology used to extract CO2 from the air stream. In embodiment 2, atmospheric air enters the engine through a filter (1) sucked by a compressor (C2) (2). The C2 compressor (2) is part of a turbogroup and is mechanically coupled to a variable geometry turbine (VGT2) (8). Compressor C2 (2) discharges air using the energy recovered by the VGT2 turbine (8) from the N2 + H2O rejected in the MIEC membrane (6) in the case of Figure 2a, or from the N2 + H2O rejected in a CO2 membrane (28) in the case of figure 2b. Under nominal conditions, the air at the outlet of compressor C2 (2) has a pressure and a temperature of approximately 0.4 MPa and 473 K (199.85 ° C). Air passes through a first engine water charge cooler (WCAC) (3). At the outlet of the first WCAC cooler (3), the temperature drops to approximately 323 K (49.85 ° C), which makes subsequent compression in the first cylinders (4) of the engine more isothermal.
[0161] In the embodiment of figure 2a the air is cleaned of CO2 in a polymeric CO2 (28) membrane with a global CO2 / N2 selectivity of around 2000 at the working temperature at the outlet of the first WCAC cooler (3). This is achieved in figure 2a thanks to the fact that the CO2 that passes through the membrane is entrained by the water vapor coming from a separator (17) that lowers the partial pressure of the atmospheric CO2 permeated in the CO2 membrane (28). In Figure 2a, atmospheric CO2 and the water used to sweep the CO2 membrane (28) are attached to the stream of O2 and products of combustion in means for carrying out a vacuum Brayton cycle (CBV) ( twenty-one). Specifically, this occurs at the outlet of a fifth WCAC cooler (31) as shown in Figure 5a, which represents the internal detail of the CBV cycle and will be explained later.
[0162] In another preferred embodiment shown in figure 2b, the air does not meet any CO2 membrane at the outlet of the first WCAC cooler (3) and, therefore, the CO2 content of the air does not change. For this other version of embodiment 2 this CO2 is collected downstream.
[0163] Subsequently, the air is sucked through the first cylinders (4) of the engine. In embodiment 2 a 5-cylinder, 4-stroke engine is depicted, and it is 2 cylinders that draw the air. The first cylinders (4) act as pumps, compressing the air to approximately 0.9 MPa and 473 K (199.85 ° C). The first cylinders (4) are preferably identical to the rest of the engine's cylinders, sharing the crankshaft (25), the camshaft and the distribution, and having the only singularity that they are not injected with fuel. Being a 4-stroke engine, the air remains 4 strokes inside the first cylinders (4), which compresses and cools with the engine's cooling water (approximately 363 K (89.85 ° C)) which contributes to making more isotherm compression. These first cylinders (4) work as a starting system for the set of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0164] At the exit of the first cylinders (4), the air is heated in a first regenerator (23), which lowers its pressure to 0.87 MPa and raises its temperature to approximately 573 K (299.85 ° C), using the thermal energy from a flow of CO2 and H2O at the outlet of an additional piston (22). At the exit of the first regenerator (23), the air is heated in a third regenerator (24), which lowers its pressure to 0.85 MPa and raises its temperature to approximately 673 K (399.85 ° C), using the energy thermal flow of N2 at a temperature of approximately 800 K (526.85 ° C) and a pressure of 0.1 MPa from the outlet of the VGT2 turbine (8).
[0165] At the exit of the third regenerator (24), the air is heated again in a catalytic MIEC membrane (15), which lowers its pressure to 0.8 MPa and raises its temperature to approximately 723 K (449.85 ° C) using for this the thermal energy of the exhaust gases from the combustion of the second cylinders (14). In the catalytic MIEC membrane (15) the exhaust gases transfer their heat to the air (it acts as a regenerator) and both CO and HC are oxidized until the entire gas flow is composed solely of CO2 and H2O. This reduces the need for gas cleaning after-treatment of this engine to 20%; since this flow of exhaust gases represents approximately 20% of the total flow of exhaust gases transferred by the engine. After the catalytic MIEC membrane (15) the air is heated again in a second regenerator (5) that lowers its pressure to 0.8 MPa and raises its temperature to approximately 873 K (599.85 ° C) using the energy O2 thermal obtained from the air through the MIEC membrane (6) and from the CO2 used to entrain the O2 that passes through the MIEC membrane (6) and lower the partial pressure of O2 in the entrainment chamber.
[0166] After the second regenerator (5), the air at 0.8 MPa and 873 K (599.85 ° C) is injected into the O2 membrane MIEC (6) where it reaches the working temperature of the MIEC membrane (6) ( approximately 1173 K (899.85 ° C)) thanks to the heat exchange with CO2 and H2O that comes from the oxy-fuel process and is used to sweep the O2 side.
[0167] In the case of the embodiment of figure 2b, the O2-depleted air, rejected in the MI2 membrane (6) of O2 enters, at approximately 1173 K (899.85 ° C) and 0.8 MPa, in a membrane of CO2 (28) (based on molten carbonates with an overall CO2 / N2 selectivity of around 2,500 at operating temperature) where CO2 is separated atmospheric N2 + H2O stream. This is achieved thanks to the fact that the CO2 is swept away by the water vapor coming from the separator (17) that lowers the partial pressure of the atmospheric CO2 permeated in the membrane. In Figure 2b, atmospheric CO2 permeate joins the mixture of O2 produced by the MIEC membrane (6) and CO2 and H2O from the combustion of the second cylinders (14) and used to sweep the MIEC membrane (6) and lower the partial pressure of the O2.
[0168] In the other version of the preferred embodiment shown in Figure 2a, the rejection of the O2 membrane MIEC (6) is not found downstream with any CO2 membrane, because the air has already been previously cleaned of CO2 in the CO2 (28), as previously explained.
[0169] The rejection of the O2 membrane MIEC (6), in the case of the embodiment of figure 2a, and the rejection of the CO2 membrane (28), in the embodiment of figure 2b, are both practically free of atmospheric CO2 and they are atmospheric N2 + H2O at 0.75 MPa and 1173 K (899.85 ° C). Each of these rejects represents approximately 80% of the air mass transferred by the system and is passed through the VGT1 turbine (71) and / or the control valve (72).
[0170] The VGT1 turbine (71) and the control valve (72) are part of a turbogroup together with the C1 compressor (10), to which the VGT1 turbine (71) is mechanically attached. The VGT1 turbine (71) energetically valorises the rejected N2 flow from the MIEC membrane (6), recovering its energy to move compressor C1 (10). The control valve (72) regulates the flow of energy to the compressor C1 (10). Compressor C1 (10) discharges the sweeping CO2 from the MIEC membrane (6), therefore it discharges a mixture of CO2, H2O and O2. Compressor C1 (10) discharges approximately 95% of the engine's gas flow. As a consequence, the control valve (72) regulates the flow of CO2 and H2O used to dilute the O2 and, therefore, the temperature of the combustion and of the combustion exhaust gases. In conclusion, the temperature of the engine exhaust gases, at the exit of the second cylinders (14), is regulated by the control valve (72); and it is at an approximate value of 1273 K (999.85 ° C) under nominal conditions.
[0171] Normally, the control valve (72) works partially open to regulate the pressure of the compressor C1 (10). A part of the rejected N2 in the MIEC membrane (6) circulates through the VGT1 turbine (71), expanding and cooling. The other part of the rejected N2 circulates through the control valve itself (72), without cooling. This other part of the N2 mixes downstream of the VGT1 turbine (71) with the cold and expanded N2, reheating it, and consequently increasing its temperature.
[0172] After passing through the control valve (72) and / or through the turbine (71) the rejection N2 + H2O of the MIEC membranes (80% of the air flow) is valued in the VGT2 (8) variable geometry used to move the C2 (2) compressor. The approximate nominal conditions of entry to the VGT2 turbine (8) are 0.3 MPa and 823 K (549.85 ° C). The variable geometry of the VGT2 turbine (8) is used to regulate the degree of load of the combustion engine. When the VGT2 turbine (8) is closed, the air flow through the MIEC membrane (6) and the working pressure in the MIEC membrane (6) increases. Therefore, the hourly production of O2 and the amount of fuel that can be injected under stoichiometric conditions increases. The reverse is true when the VGT2 turbine (8) opens. The minimum size (minimum opening) of the VGT2 turbine (8) is chosen in accordance with the displacement of the reciprocating engine to set the maximum power of the system at each engine rotation speed. The maximum opening of the VGT2 turbine (8) determines the minimum load (idle) of the reciprocating motor at each speed. The VGT2 turbine (8) can also comprise a relief valve (or WG). When the VGT2 turbine (8) or its relief valve is opened to the maximum, the energy of the compressor C2 (2) is reduced to zero, which reduces both the working pressure of the MIEC membrane and the flow of air transferred considerably.
[0173] If it is desired to further reduce the motor load to zero, then the control valve (72) is opened avoiding the VGT1 turbine (71) whereby the energy of compressor C1 (10) is reduced to zero. In this case, the flow of CO2 and H2O to the MIEC membrane is stopped (6). This equalizes the partial pressure of O2 on both sides of the MIEC membrane (6) and stops the flow of O2 production by leaving the engine load of this embodiment 2 empty.
[0174] At the output of the VGT2 turbine (8), the mixture of N2 and H2O at a pressure of 0.1 MPa and a temperature of approximately 800 K (526.85 ° C), is passed through the third regenerator (24) to yield its heat to the air before discharging this gas mixture (free of gases harmful to health) into the atmosphere.
[0175] The mixture of the O2 exchanged by the MIEC membrane (6) and the CO2 and H2O, used to sweep and lower the partial pressure of the O2 that crosses the membrane, exit through the corresponding end of the MIEC membrane (6), towards the second cylinders (14) combustion, sucked by compressor C1 (10). For the version of embodiment 2 based on molten carbonate membranes to collect atmospheric CO2 (figure 2b), it is at this point (at the exit of the MIEC membrane (6)) where said mixture (mixture of O2 exchanged by the membrane MIEC (6) and the CO2 and H2O, used to sweep and lower the partial pressure of the O2 that passes through the membrane) are mixed in turn with atmospheric CO2 and the water vapor used to sweep it. This mixture exits at a nominal pressure and temperature of approximately 0.1 MPa and 1173 K (899.85 ° C) respectively; and represents approximately 80% of the air flow transferred by the motor. The heat from the CO2, H2O and O2 mixture is recovered first in the second regenerator (5) to heat the air at the outlet of the catalytic MIEC membrane (15). At the outlet of the second regenerator (5) it has nominal conditions of approximately 0.08 MPa and 723 K (449.85 ° C).
[0176] Then the mixture flows through a means to carry out a vacuum Brayton cycle (CBV) (21). The means to carry out a vacuum Brayton cycle (CBV) (21) have the function of cooling the mixture transforming its temperature into pressure and recovering the loss of pressure caused by the second regenerator (5). The means for carrying out a vacuum Brayton cycle (CBV) (21) are composed of a VGT3 turbine (16) mechanically coupled with a C3 compressor (12) with which it forms a turbogroup. Between the VGT3 turbine outlet (16) and the C3 compressor inlet (12) there is a fifth WCAC cooler (31). For the version of embodiment 2 that is based on polymeric membranes to collect atmospheric CO2 (figure 2a), it is at the exit of the fifth WCAC cooler (31) where the O2 and CO2 of the combustion are mixed with the atmospheric CO2 and the water used to sweep it. In figure 2b atmospheric CO2 is already part of the oxidizing mixture at this point. The internal detail of the means for carrying out a vacuum Brayton cycle (CBV) (21) can be seen in figure 5a and its operating cycle in the T-s diagram of figure 5b). The mixture of CO2, H2O and O2 expands for energy recovery in the VGT3 turbine (16); it is cooled in the fifth WCAC cooler (31), suffering a slight pressure drop, and it is compressed in compressor C3 (12), mechanically coupled with the VGT3 turbine (16). At the outlet of compressor C3 (12) the mixture is colder and at more pressure than at the inlet of the VGT3 turbine (16).
[0177] The nominal conditions of the oxidizing mixture at the outlet of compressor C3 (12) are approximately 0.1 MPa and 523 K (249.85 ° C). The oxidizing mixture, which continues on its way to the second cylinders (14), is cooled in the second WCAC cooler (9) to 323 K (49.85 ° C). The compressor C1 (10) is then compressed to 0.3 MPa and 473 K (199.85 ° C), with the conditions of the compressor C1 (10) being imposed by the control valve (72) to maintain the temperature of exhaust gases around 1273 K (999.85 ° C), as already described. After compressor C1 (10) the mixture of CO2, H2O and O2 is re-cooled in the third WCAC cooler (11) to 323 K (49.85 ° C) before being sucked through the second cylinders (14). These cylinders are 2 of the 5 that has the four-stroke engine used as an example; as stated at the beginning of the description of embodiment 2.
[0178] In the second cylinders (14), an HxCyOz hydrocarbon is injected, with a fuel pump (26), into the oxidizing mixture of CO2, H2O and O2 in proportion stoichiometric with O2. In said second cylinders (14) a triggered ignition premixed combustion cycle is performed and similar to the Otto cycle. The second cylinders (14) produce energy to move the first cylinders (4) that transfer the air to the MIEC membrane (6) and the additional piston (22), which compresses to densify the residual CO2 and H2O, since they are all coupled in the same crankshaft (25). The second cylinders (14) also produce a surplus of net mechanical energy that is used to move the vehicle to which the motor is coupled, or the electric generator or any application that requires a supply of mechanical energy through an axle. These second cylinders (14) function as a starting system for the set of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0179] The transfers of heat to water from the first (3), second (9), third (11), fourth (13), fifth (31) and sixth (18) chillers plus the heat given up in the regenerations (produced in the regenerators first (23), second (5), third (24) and in the catalytic MIEC (15)) together with the densification and capture of the excess CO2 and H2O, suppose the total transfer of heat to the cold focus necessary for the The proposed thermodynamic cycle complies with the second principle of thermodynamics and is therefore viable. In turn, the heat transfers in the first (3), second (9), third (11), fourth (13), fifth (31) and sixth (18) WCAC coolers, and in the regenerations (produced in the regenerators first (23), second (5), third (24) and in the catalytic MIEC (15)) contribute to minimizing the exergy destruction of the thermodynamic cycle due, on the one hand, to the process of global compression of the working fluid more isothermal and on the other to recover the energy of the exhaust gases for air separation. The approach to isothermal compression and the use of regenerators to extract heat from CO2 + H2O bring the N2 cycle in the MIEC membrane (6) closer to a cycle with the same performance as the Carnot cycle known as the Ericsson cycle. The CO2 + H2O + O2 mix cycle can be assimilated to a closed Brayton cycle with intermediate compressions and expansions, but nested with an Otto cycle in the second cylinders (14); something not described until now in the bibliography. In essence, the quasi-closed Brayton cycle nested with the Otto cycle and binary with the N2 cycle (by sending heat to the N2 cycle it complies with the thermodynamic precepts to approach an ideal cycle of maximum efficiency, such as the Ericsson cycle) is a novel embodiment binary cycle; that fulfills the precepts of the other ideal cycle of maximum efficiency, that of Carnot.
[0180] As a result of the combustion of the hydrocarbon (fuel) with the oxidizing mixture (CO2, H2O, O2), at the output of the second cylinders (14) a mixture of CO2, H2O, unburned THC and CO. On the one hand, 80% of these exhaust gases are sucked by compressor C1 (10) and the second cylinders (14) themselves to pass through the MIEC membrane (6). In the MIEC membrane (6), on the one hand, it performs the function of sweeping and lowering the O2 partial pressure to improve the transport of O2 of the MIEC membrane (6); on the other hand, mixing with CO2 lowers the combustion temperature to tolerable limits for the materials of alternative internal combustion engines (MCIA). In this way, at the exit of the MIEC membrane (6) the cycle is closed and the mixture returns to the entrance of the second regenerator (5) to transmit its heat to the air. In the described process, the motor works efficiently both by keeping the dosing always close to the stoichiometric one and by regulating its load without throttling the flow, but by modulating the O2 production of the membrane. The productivity of the membrane responds instantaneously to the accelerations of the engine since the first cylinders (4) are mechanically coupled on the same axis with the second cylinders (14). Therefore, the dynamic response of the engine is not conditioned by the delay of the turbocharged MCIAs, due to the mechanical inertia of the turbogroup.
[0181] On the other hand, the remaining 20% of the exhaust gases, which are a mixture of: CO2, H2O, unburned THC and CO, is oxidized with the O2 left over from combustion in the catalytic MIEC membrane (15) to which They enter at a temperature of approximately 1273 K (999.85 ° C) and yield their heat to 100% of the air flow that the motor raises, with which their temperature drops greatly, to approximately 703 K (429.85 ° C). ). At the same time, and due to the chemical reactions that take place in the catalytic MIEC membrane (15), CO and THC are oxidized with the O2 left over from combustion to H2O and CO2 vapor, and, again, due to the Oxy-combustion prevents the production of NOx in the second cylinders (14). Therefore, the mixture is discharged without any gas harmful to health (without CO, without THC and without NOx).
[0182] Next, a first non-return valve (33) is installed to prevent backflow from the additional piston (22). The additional piston (22) is moved by the crankshaft (25) and compresses this 20% of the flow (the mentioned remaining 20% of the exhaust gases) to 7.5 MPa. The 7.5 MPa pressure is regulated by a second non-return valve (19) and its setting spring. Compression is performed almost isothermally in the four strokes of the additional piston (22), from opening the intake valve to suck the mixture of CO2 and H2O steam until opening the exhaust valve to discharge it. The mixture compressed to 7.5 MPa is discharged at a temperature of approximately 673 K (399.85 ° C), it must be kept above the 573 K (299.85 ° C) which is the saturation temperature of the water at 7.5 MPa for ensure that it remains in the gas state inside the additional piston (22).
[0183] The mixture is cooled first in the first regenerator (23) and then in the fourth WCAC cooler (13) to 473 K (199.85 ° C), whereby the H2O becomes liquid. The mass of liquid water at 7.5 MPa and 473 K (199.85 ° C) represents approximately 2% of the total mass flow rate transferred by the engine. Next, the liquid water is separated from the CO2 gas in the separator (17), which can be an inertial separator with a pressure lamination valve at the outlet. A polymeric membrane can also be used as separator (17), if the water is kept in a gaseous state. The separated water at a pressure of approximately 0.1 MPa and 473 K (199.85 ° C) is energetically recovered using it as a driving fluid in the CO2 membrane (28). Water vapor sweeps the CO2 side, lowering its partial pressure by dilution. A third non-return valve (32), which connects the H2O circuit from the combustion with the atmosphere, regulates the pressure of the water vapor, keeping it equal to the barometric pressure. Furthermore, it allows the excess water vapor generated in the successive combustions of the engine to be purged into the atmosphere.
[0184] After the H2O is removed, the excess CO2, already in high purity, is cooled in a sixth WCAC cooler (18) below its critical temperature, 303 K (29.85 ° C). Liquid CO2 passes through the second non-return valve (19) and is stored at 7.5 MPa in a first tank (20) with a controlled temperature below 303 K (29.85 ° C). When this tank is full the autonomy of the motor ends. The tank is maintained at subcritical CO2 temperatures (<303 K (29.85 ° C)) using, if necessary, a refrigeration circuit such as that produced by the vehicle's air conditioning. The tank is unloaded at the service station, exchanging for a fuel tank. Liquid CO2 can again become a hydrocarbon (as in synthetic fuels called e-Diesel, Blue-crude, etc.); be supplied as a product to the chemical industry; supplied as refrigerant fluid to the refrigeration industry or stored in controlled sinks. But it is not emitted into the atmosphere. The non-emission of CO2 into the atmosphere makes it possible to determine that the present embodiment 2 is an engine with negative net emissions since it has removed atmospheric CO2 and has not emitted the one produced in its combustion process.
[0185]
[0186] Embodiment 3: Compression Ignition (CI) Engine; of stratified mixture and combustion by diffusion; with variable effective compression ratio controlled by the production rate of O ; without polluting gas emissions and without CO capture Embodiment 3 is indicated for compression ignition (CI) engines of stratified mixture (diffusion combustion) without emission of contaminants and without capture CO2. For the production of net mechanical power, embodiment 3 is based on a diffusion combustion process, with auto-ignition by detonation of the premix and combustion rate controlled by the amount of movement of the fuel jets.
[0187] The degree of overfeeding affects the percentage of maximum torque at each speed through the effective compression ratio of the cycle. This effective compression ratio is variable and is controlled by the rate of O2 production in the MIEC membrane. This supposes a concept of reduction of size, being able to decrease the engine's displacement and bring the effective compression process of the air in turbomachines and cylinders closer to the isothermal process.
[0188] The combustion temperature is controlled by diluting the pre-cooled mixture of oxidizer (O2) and fuel (HxCyOz) with CO2 and H2O from the combustion itself. This mixture with high recirculated exhaust gas (EGR) rates also helps to increase the rate of O2 production in the O2 MIEC (6) membrane by lowering its partial pressure.
[0189] In embodiment 3, it is not proposed to capture the CO2 emitted by the engine, but to eliminate the emissions of polluting gases (CO, THC, PM and NOx) at the source (combustion chamber) or in the MIEC membrane, without the need for post-treatment for cleaning exhaust gases, which represents a considerable saving in the production cost of the engine. At present it is estimated that the post-treatment for gas cleaning is of the order of 30% of the total cost of the motor-propulsion group. Furthermore, due to oxy-combustion, it is guaranteed that no polluting gases are emitted during the cold start process. This does not happen in today's engines, due to the time required to heat (activate) the aftertreatment systems for exhaust gas cleaning.
[0190] Embodiment 3 is shown in figure 3. In embodiment 3, atmospheric air enters the engine through a filter (1) sucked by a compressor (C2) (2). The C2 compressor (2) is part of a turbogroup and is mechanically coupled to a variable geometry turbine (VGT2) (8). Compressor C2 (2) discharges air using the energy recovered by the VGT2 turbine (8) from the rejected N2 in the MIEC membrane (6). Under nominal conditions, the air at the outlet of compressor C2 (2) has a pressure and a temperature of approximately 0.4 MPa and 473 K (199.85 ° C). Air passes through a first engine water charge cooler (WCAC) (3). At the outlet of the first WCAC cooler (3), the temperature drops to approximately 323 K (49.85 ° C), which makes subsequent compression in the first cylinders (4) of the engine more isothermal.
[0191] Subsequently, air is sucked through half of the first cylinders (4) of the motor. In embodiment 3 a 4-cylinder, 4-stroke engine is depicted, whereby 2 cylinders are sucking air. The first cylinders (4) act as pumps, compressing the air to approximately 0.8 MPa and 473 K (199.85 ° C). The first cylinders (4) are preferably identical to the rest of the engine's cylinders, sharing the crankshaft (25), the camshaft and the distribution, and having the only singularity that they are not injected with fuel. Being a 4-stroke engine, the air remains 4 strokes inside the first cylinders (4), which compresses and cools with the engine's cooling water (approximately 363 K (89.85 ° C)) which contributes to making the compression more isothermal. These first cylinders (4) work as a starting system for the set of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0192] At the exit of the first cylinders (4), the air is heated in a first regenerator (23) that lowers its pressure to 0.77 MPa and raises its temperature to approximately 673 K (399.85 ° C); using for this the thermal energy of a flow of CO2, H2O and N2. This flow of N2, CO2 and H2O exits into the atmosphere through the duct (30) located downstream of the VGT2 turbine (8). This flow of N2, CO2 and H2O represents approximately 80% of the total air flow transferred by the engine and is at a temperature of approximately 800 K (526.85 ° C) and a pressure of 0.1 MPa. At the exit of the first regenerator (23), the air is heated in a second regenerator (5) that raises its temperature to approximately 973 K (699.85 ° C), using the thermal energy of the O2 produced by the MIEC membrane (6). ) and the CO2 used to sweep the MIEC membrane (6) and lower the O2 partial pressure. After the second regenerator (5) the air at 0.75 MPa pressure enters the MIEC membrane (6) where it reaches the working temperature of the MIEC membrane (6) (approximately 1223 K (949.85 ° C)) thanks the heat exchange with CO2 and H2O that comes from the oxy-fuel process and that is used to sweep the O2.
[0193] The rejection of the MIEC membrane (6) is fundamentally N2 at 0.7 MPa and 1173 K (899.85 ° C); it represents approximately 80% of the air mass transferred by the system and passes through the VGT1 turbine (71) and / or through the control valve (72). The VGT1 turbine (71) and the control valve (72) are part of a turbogroup together with the C1 compressor (10), to which the VGT1 turbine (71) is mechanically attached. The VGT1 turbine (71) energetically valorises the rejected N2 flow from the MIEC membrane (6), recovering its energy to move compressor C1 (10). The control valve (72) regulates the flow of energy to the compressor C1 (10). The C1 compressor (10) transfers the CO2 + H2O from the MIEC membrane sweep (6), therefore transfers a mixture of CO2, H2O and O2. Compressor C1 (10) discharges approximately 95% of the engine's gas flow. As a consequence, the control valve (72) regulates the flow of CO2 and H2O used to dilute the O2 and therefore the temperature of the combustion and of the combustion exhaust gases. In conclusion, the temperature of the engine exhaust gases, at the exit of the second cylinders (14), is regulated by the control valve (72); and it is at an approximate value of 1223 K (949.85 ° C) under nominal conditions.
[0194] Normally, the control valve (72) works partially open to regulate the pressure of the compressor C1 (10). A part of the rejected N2 in the MIEC membrane (6) circulates through the VGT1 turbine (71), expanding and cooling. The other part of the rejected N2 circulates through the control valve itself (72), without cooling. This other part of the N2 mixes downstream of the VGT1 turbine (71) with the cold and expanded N2, reheating it, and consequently increasing its temperature.
[0195] After passing through the control valve (72) and / or through the turbine (71), the rejection N2 of the MIEC membrane (6) (80% of the air flow) is valued in the VGT2 variable geometry turbine (8 ) used to move compressor C2 (2). The approximate nominal conditions of entry to the VGT2 turbine (8) are 0.3 MPa and 823 K (549.85 ° C). The variable geometry of the VGT2 turbine (8) is used to regulate the air flow transferred by the MIEC membrane (6) and therefore the O2 flow produced. When the VGT2 turbine (8) is closed, the air flow through the MIEC membrane (6) and the working pressure in the MIEC membrane (6) increases. Therefore, the hourly production of O2 increases (at the same rate) and the amount of fuel that could be injected under stoichiometric conditions. The reverse is true when the VGT2 turbine (8) opens. The minimum size (minimum opening) of the VGT2 turbine (8) is chosen in accordance with the displacement of the reciprocating engine to set the maximum power of the system at each engine rotation speed. The maximum opening of the VGT2 turbine (8) determines the minimum O2 flow (idle) of the reciprocating engine at each speed. The VGT2 turbine (8) can also comprise a relief valve (or WG). When the VGT2 turbine (8) or its relief valve is opened to the maximum, the energy of the compressor C2 (2) is reduced to zero, which reduces both the working pressure of the MIEC membrane and the flow of air transferred considerably.
[0196] If it is desired to further reduce the O2 flow of the engine until it drops to zero, then the control valve (72) is opened, avoiding the VGT1 turbine (71), thus reducing the energy of compressor C1 (10) to zero. This practically equalizes the partial pressure of O2 on both sides of the MIEC membrane (6) and minimizes the rate of O2 production by leaving the engine load of this embodiment 3 empty.
[0197] The control valve (72) can be said to provide regulation qualitative O2 flow acting on the production rate and the VGT2 turbine (8) provides a quantitative regulation acting on the air flow rate. Both controls provide a very wide and very fine adjustment of the effective compression ratio of the cylinder in the upper dead center of the second cylinders (14) without changing the volumetric compression ratio of the latter. This is commonly known in reciprocating engines as a variable compression ratio.
[0198] At the output of the VGT2 turbine (8) the mixture of N2, CO2 and H2O at a pressure of 0.1 MPa and a temperature of approximately 800 K (526.85 ° C), is passed through the first regenerator (23) to transfer its heat to the air before discharging this mixture of gases (free of gases harmful to health) into the atmosphere.
[0199] The mixture of the O2 produced by the MIEC membrane (6) and the CO2 and H2O, used to sweep it and lower the partial pressure of the O2, leaves through the corresponding end of the MIEC membrane (6), towards the second cylinders (14) of combustion, sucked by compressor C1 (10). This mixture exits at a nominal pressure and temperature of approximately 0.35 MPa and 1223 K (949.85 ° C) respectively; and it supposes approximately 115% of the air flow transferred by the engine. The heat from the mixture of CO2, H2O and O2 is recovered first in the second regenerator (5) to heat the air coming from the outlet of the first regenerator (23). At the exit of the second regenerator (5), the oxidizing mixture has nominal conditions of approximately 0.3 MPa and 700 K (426.85 ° C). This pressure and temperature are valued in a variable geometry turbine (VGT3) (16) that is used to move a compressor (C3) (12) with which it is mechanically coupled to another turbogroup. The C3 compressor (12) is used to supercharge the second cylinders (14), like the turbochargers in use, using the energy recovered by the VGT3 turbine (16). The VGT3 turbine (16) is regulated to maintain constant and equal to 0.6 MPa the pressure downstream of the C3 compressor (12).
[0200] Downstream of the VGT3 turbine (16) the nominal conditions at the outlet of the VGT3 turbine (16) are approximately 0.1 MPa and 473 K (199.85 ° C). At the outlet of the VGT3 turbine (16) there is a branch that discharges the excess mixture of CO2, H2O and O2 vapor into the atmosphere without any polluting gas (without CO, without THC and without NOx). This is achieved thanks to the catalysis of CO and THC to H2O and CO2 vapor that is produced in the MIEC membrane (6) and to oxy-combustion that prevents the production of NOx.
[0201] The discharge is made through a second non-return valve (19) calibrated at a pressure of 0.11 MPa to prevent air or N2 from entering the mixture of oxidizing gases during the transitory processes. Upstream of the second valve backstop (19) therefore forms a closed circuit separated from the atmosphere. This volume is made up of an N2-free duct circuit that acts as a system for accumulating oxidizing mixture of CO2 + H2O + O2 after the engine stops. This accumulated mixture facilitates the subsequent starting of the engine, since there is already a surplus of O2 produced by the MIEC membrane (6), which can be used to start the combustion in the second cylinders (14).
[0202] With the branch (29) and the second non-return valve (19), the nominal pressure conditions at the outlet of the VGT3 turbine (16) are 0.11 MPa and the temperature is about 473 K (199.85 ° C). ). The non-excess mixture that continues to the second cylinders (14) is cooled in a second WCAC cooler (9) to 323 K (49.85 ° C). Next, compressor C1 (10) is compressed to 0.3 MPa and 473 K (199.85 ° C), with the conditions of compressor C1 (10) being imposed by the control valve (72) to maintain the temperature of exhaust gases around 1223 K (949.85 ° C), as already described. After compressor C1 (10) the mixture of CO2, H2O and O2 is cooled again to 323 K (49.85 ° C) in the third WCAC cooler (11) and compressed in compressor C3 (12) to 0, 6 MPa and 473 K (199.85 ° C). For this, the energy of the VGT3 turbine (16) is used, which regulates the pressure at the outlet of compressor C3 (12) equal to 0.6 MPa, as already described. Finally, the mixture is re-cooled in the fourth WCAC cooler (13) to 323 K (49.85 ° C) before being sucked through the second cylinders (14), which in this embodiment are 2 because they are half of a 4-cylinder, four-stroke engine that has been used as an example; as stated at the beginning of the description of the present embodiment 3.
[0203] In the second cylinders (14), an HxCyOz hydrocarbon is injected, with a fuel pump (26), into the oxidizing mixture of atmospheric CO2 and O2. The hydrocarbon is injected in the desired way and quantity to regulate the load of the combustion engine by diffusion and in less than stoichiometric proportion with O2. In said second cylinders (14) a diffusion combustion cycle is carried out; compression ignition and similar to the Diesel cycle that is mainly carried out by O2 and the products of combustion. That is, approximately 80% of the amount of air that enters the engine.
[0204] The second cylinders (14) produce energy to move the first cylinders (4) that transfer the air to the MIEC membrane (6) since they are coupled to the same crankshaft (25). The second cylinders (14) produce a surplus of net mechanical energy that is used to move the vehicle to which the motor is coupled, or the electric generator or any application that requires a supply of mechanical energy through an axle. These second cylinders (14) function as a starting system for the assembly of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0205] The transfers of heat to water from the first (3), second (9), third (11) and fourth (13) WCAC chillers; together with heat transfer on the MIEC membrane (6); in the second (5) and first (23) regenerators and finally the discharge into the atmosphere of the excess of oxidizing mixture, through the bifurcation (29), they suppose the total transfer of heat to the cold focus necessary for the thermodynamic cycle to comply the second principle of thermodynamics and is therefore viable. In turn, the heat transfers in the first (3), second (9), third (11) and fourth (13) WCAC coolers and in the regenerations (produced in the second (5) and first (23) regenerators) they contribute to minimizing the destruction of exergy in the thermodynamic cycle due, on the one hand, to making the overall compression process of the working fluid more isothermal and, on the other, to recovering the energy of the exhaust gases for air separation. The approach to isothermal compression and the use of regenerators to extract heat from CO2, N2 and H2O bring the N2 cycle in the MIEC membrane (6) closer to a cycle with the same performance as that of Carnot, known as the Ericsson cycle. The cycle of mixing CO2, H2O and O2 can be assimilated to a closed Brayton cycle with intermediate compressions and expansions, but nested with a Diesel cycle in the second cylinders (14); something not described until now in the bibliography. In essence, the quasi-closed Brayton cycle nested with the Diesel cycle and binary with the N2 cycle (sending heat to the N2 cycle, it complies with the thermodynamic precepts to approach an ideal cycle of maximum efficiency, such as the Ericsson cycle) is a novel embodiment binary cycle; that fulfills the precepts of the other ideal cycle of maximum efficiency, that of Carnot.
[0206] Finally, as a result of the combustion of the hydrocarbon (fuel) with the oxidizing mixture (CO2, H2O, O2), a mixture of unburned CO2, H2O, THC and CO is produced at the outlet of the second cylinders (14), which is called exhaust gas. At the exit of the second cylinders (14) this exhaust gas is at a maximum pressure and temperature of 0.6 MPa and 1223 K (949.85 ° C) respectively. The exhaust gas mixture is passed through the MIEC membrane (6) sucked by the compressor C1 (10), the compressor C3 (12) and in the last room by the second cylinders themselves (14). In the MIEC membrane (6), the exhaust gas mixture on the one hand performs the function of sweeping it: lowering the partial pressure of the O2 to improve the productivity of the MIEC membrane (6) and diluting the O2 until the combustion temperatures are compatible with the materials technology of current MCIAs. Furthermore, the exhaust gas mixture is catalyzed, reacting with O2 to convert THC and CO resulting from the combustion process into CO2 and H2O. In this way, at the exit of the MIEC membrane (6) the cycle is closed and the mixture returns to the entrance of the second regenerator (5) to transmit its heat to the air.
[0207] In the described process, the engine works optimally, regulating the effective compression ratio of the same with the VGT2 turbine (8) to the most efficient according to the degree of load and the speed of rotation of the engine. The productivity of the membrane responds instantaneously to the accelerations of the engine since the first cylinders (4) are mechanically coupled on the same axis with the second cylinders (14). Therefore, the dynamic response of the engine is not affected by the delay in the acceleration of the turbogroup, due to its mechanical inertia. Finally, the engine only emits a mixture of: CO2, H2O and O2 into the atmosphere through the branch pipe (29), through the second non-return valve (19); and atmospheric N2 + CO2 from the VGT2 turbine outlet (8). In other words, it does not emit any polluting gas that adversely affects people and animals. Both emissions are mixed in the same exhaust duct (30), which connects downstream of the second non-return valve (19) and the VGT2 turbine (8) all the engine emissions in a common exhaust.
[0208]
[0209] Embodiment 4: Compression Ignition (CI) Engine; of stratified mixture and combustion by diffusion; with variable effective compression ratio controlled by the production rate of O ; no emissions of polluting gases and with capture of CO2 produced and removal of atmospheric CO2
[0210] Embodiment 4 is indicated for compression ignition (CI) engines of stratified mixture (diffusion combustion) with capture of atmospheric CO2 and that produced by the engine itself. Therefore, it falls within the category of engines that remove CO2 from the atmosphere (emission rate <0). For the production of net mechanical power, embodiment 4 is based on a diffusion combustion process, with auto-ignition by detonation of the premix and combustion speed controlled by the amount of movement of the fuel jets (and in this case of the liquid CO2) injected.
[0211] The degree of overfeeding affects the percentage of maximum torque at each speed through the effective compression ratio of the cycle. This effective compression ratio is variable and is controlled by the rate of O2 production in the MIEC membrane. This supposes a concept of reduction of size, being able to decrease the engine's displacement and bring the effective compression process of the air in turbomachines and cylinders closer to the isothermal process.
[0212] The combustion temperature is controlled by the dilution of the mixture of oxidizer (O2) and fuel (HxCyOz) with liquid CO2 from the combustion itself and densified to supercritical conditions. Due to the large amount of CO2 required, this represents an additional innovation, since two cycles coexist in the cylinders: (i) on the one hand, a supercritical thermodynamic CO2 cycle carried out by the CO2 used to control the combustion temperature and, at the At the same time, (ii) a Diesel cycle carried out by the oxidizing O2 and its products. This has not been described so far in the published literature.
[0213] Embodiment 4 proposes to capture the CO2 emitted by the engine and reduce the atmospheric CO2 content of the air used, both in the most efficient way possible. In addition, it eliminates the emissions of polluting gases (CO, THC, PM and NOx) at the source (combustion chamber), minimizing the need for post-treatment to clean the exhaust gases, which represents a considerable saving in the cost of production of the engine . At present it is estimated that the post-treatment for gas cleaning is of the order of 30% of the total cost of the motor-propulsion group. Additionally, due to oxy-combustion, it is guaranteed that no polluting gases are emitted during the cold start process. This does not happen in today's engines, due to the time required to heat (activate) the aftertreatment systems for exhaust gas cleaning.
[0214] Embodiment 4 is shown in Figures 4a and 4b. In embodiment 4, atmospheric air enters the engine through a filter (1) sucked by a compressor (C2) (2). The C2 compressor (2) is part of a turbogroup and is mechanically coupled to a variable geometry turbine (VGT2) (8). Compressor C2 (2) discharges air using the energy recovered by the VGT2 turbine (8) from the N2 + H2O rejected in the MIEC membrane (6). Under nominal conditions, the air at the outlet of compressor C2 (2) has a pressure and a temperature of approximately 0.4 MPa and 473 K (199.85 ° C). Air passes through a first engine water charge cooler (WCAC) (3). At the outlet of the first WCAC cooler (3), the temperature drops to approximately 323 K (49.85 ° C), which makes subsequent compression in the first cylinders (4) of the engine more isothermal.
[0215] In the embodiment of figure 4a the CO2 content of the air is reduced in a polymeric CO2 membrane (28) with a global CO2 / N2 selectivity of around 2000 at the working temperature at the outlet of the first WCAC cooler (3) . This is achieved in figure 4a thanks to the fact that the CO2 is entrained by the pure O2 taken downstream of the third WCAC cooler (11) and coming from the O2 separation membrane MIEC (6). O2 lowers the partial pressure of atmospheric CO2 permeated in the drag chambers of the membrane module. In Figure 4a, the collected atmospheric CO2 and O2 used to sweep the membrane are directed towards the first valve. backstop (33) to suck through the second cylinders (14).
[0216] In a second version of this embodiment, shown in figure 4b, the CO2 from the atmospheric air is separated by means of a CO2 membrane (28) based on molten carbonates, so that at the outlet of the first WCAC cooler (3) the air does not it meets no CO2 membrane.
[0217] Subsequently, the air is sucked through half of the first cylinders (4) of the engine. In embodiment 4, a 4-cylinder, 4-stroke engine is depicted, and it is 2 cylinders that draw the air. The first cylinders (4) act as pumps, compressing the air to approximately 1.5 MPa and 473 K (199.85 ° C). The first cylinders (4) are preferably identical to the rest of the engine's cylinders, sharing the crankshaft (25), the camshaft and the distribution, and having the only singularity that they are not injected with fuel. Being a 4-stroke engine, the air remains 4 strokes inside the first cylinders (4), which compresses and cools with the engine's cooling water (approximately 363 K (89.85 ° C)) which contributes to making the compression more isothermal. These first cylinders (4) work as a starting system for the set of turbomachines, to start the air flow and the cycle turbines. To do this, they are moved, until the system starts, by a conventional starter motor used in alternative motors.
[0218] At the exit of the first cylinders (4), the air is heated in a first regenerator (23) that lowers its pressure to 1.47 MPa and raises its temperature to approximately 673 K (399.85 ° C); using for this the thermal energy of a flow of H2O and N2. This flow of N2 and H2O comes from the VGT2 turbine (8). This flow of N2 and H2O represents approximately 90% of the total flow of gases transferred by the engine and is found at a temperature of approximately 800 K (526.85 ° C) and a pressure of 0.1 MPa. At the exit of the first regenerator (23), the air is heated in a second regenerator (5), which lowers its pressure to 1.45 MPa and raises its temperature to approximately 723 K (449.85 ° C), using thermal energy for this. of the O2 produced by the MIEC membrane (6) in figure 4a. In figure 4b, the thermal energy of the O2 produced by the MIEC membrane (6) and the CO2 produced in the CO2 membrane (28) are used for this. The temperature does not rise much because O2 represents approximately 20% of the air flow.
[0219] At the exit of the second regenerator (5) the air is heated in a catalytic MIEC membrane (15) that lowers its pressure to 1.4 MPa and raises its temperature to approximately 1123 K (849.85 ° C); using for this the thermal energy of the exhaust gases from the combustion of the second cylinders (14). In the catalytic MIEC membrane (15) the exhaust gases transfer their heat to the air (acts as a regenerator) and both CO and HC (CO and HC account for less than 1% of the composition of the exhaust gases and therefore have not been explicitly reflected in Figures 4a and 4b) oxidize until the entire gas stream is composed of CO2 only and H2O. This flow of CO2 and H2O represents approximately 100% of the total flow of exhaust gases transferred by the engine at very high pressures (7.5 MPa), which greatly increases its density and reduces the size of the catalytic MIEC membrane. (15) necessary for the oxidation of gases from this engine.
[0220] Following the catalytic MIEC membrane (15), air at 1.4 MPa and 1123 K (849.85 ° C) is injected into the MIEC membrane (6) of O2 where O2 is separated.
[0221] In the case of the embodiment based on the separation of atmospheric CO2 from air by means of membranes based on molten carbonates shown in Figure 4b, the N2, H2O and atmospheric CO2, which involves the rejection of the O2 membrane MIEC (6) enters approximately 1123 K (849.85 ° C) and 1.35 MPa in the CO2 membrane (28), in this case a molten carbonate membrane with an overall CO2 / N2 selectivity of around 2,500 at the working temperature, where atmospheric CO2 is separated from the N2 + H2O stream. For this, the pure O2 produced by the MIEC membrane (6) is used as a drag current. When this O2 leaves the MIEC membrane (6) towards the second combustion cylinders (14), sucked by the 0.05 MPa vacuum generated by the C1 compressor (10), it is passed through the atmospheric CO2 side of the CO2 membrane (28). In this way O2 is used to sweep the CO2 from the CO2 membrane (28) and lower the CO2 partial pressure.
[0222] In the first version of this embodiment, where polymeric membranes are used for the separation of atmospheric CO2 from air (shown in Figure 4a), the rejection of the O2 MIEC membrane (6) is not found downstream with any CO2 membrane; since the air has already been previously treated to reduce the CO2 content in the polymeric CO2 membrane (28) of figure 4a. The rejection of the O2 membrane MIEC (6), in the case of the embodiment of figure 4a, or the rejection of the CO2 membrane (28), in the embodiment of figure 4b, are both practically free of atmospheric CO2 and, they are composed mainly of N2 + H2O at 1.35 MPa and 1123 K (849.85 ° C). These procedures for separating atmospheric CO2 from the treated air cause the described engine to remove CO2 from the atmosphere and can be considered as a negative CO2 emission rate. Indeed, the CO2 content of the N2 + H2O stream that is emitted at the output of the VGT2 turbine (8) is minimal (<1-5% of the input content in the air) and the CO2 produced in combustion is It liquefies and is captured in the system, as explained later.
[0223] Each of the rejections of the membranes, represents approximately 80% of the air mass transferred by the system and is passed through the VGT1 turbine (71) and / or through the control valve (72). The VGT1 turbine (71) and the control valve (72) are part of a turbogroup together with the C1 compressor (10), to which the VGT1 turbine (71) is mechanically attached. The VGT1 turbine (71) energetically valorises the rejected N2 flow from the MIEC membrane (6), recovering its energy to move compressor C1 (10). The control valve (72) regulates the flow of energy to the compressor C1 (10). Compressor C1 (10) discharges the pure O2 produced in the MIEC membrane (6) in the case of figure 4a. In the case of figure 4b, compressor C1 (10) discharges pure O2 produced in the MIEC (6) CO2 membrane. Therefore, it bypasses approximately 20% of the air flow and controls the vacuum to be generated on the O2 side of the MIEC membrane (6) to lower the O2 pressure and increase the productivity of the membrane. As a consequence, the control valve (72) regulates the O2 production rate and therefore the O2 mass trapped in the cycle and the maximum cycle pressure in the second cylinders (14).
[0224] Normally, the control valve (72) works partially open to regulate the pressure of the compressor C1 (10). A part of the rejected N2 in the MIEC membrane (6) circulates through the VGT1 turbine (71), expanding and cooling. The other part of the rejected N2 circulates through the control valve itself (72), without cooling. This other part of the N2 mixes downstream of the VGT1 turbine (71) with the cold and expanded N2, reheating it, and consequently increasing its temperature.
[0225] After passing through the control valve (72) and / or through the turbine (71) the rejection N2 + H2O of the MIEC membrane (6) (80% of the air flow) is valued in the VGT2 variable geometry turbine (8) which is used to move the C2 compressor (2). The approximate nominal conditions of entry to the VGT2 turbine (8) are 0.35 MPa and 823 K (549.85 ° C). The variable geometry of the VGT2 turbine (8) is used to regulate the air flow transferred by the MIEC membrane (6) and, therefore, the O2 flow produced. When the VGT2 turbine (8) is closed, the air flow through the MIEC membrane (6) and the working pressure in the MIEC membrane (6) increases. Therefore, the hourly production of O2 increases (at equal rates) and the amount of fuel that could be injected under stoichiometric conditions. The reverse is true when the VGT2 turbine (8) opens. The minimum size (minimum opening) of the VGT2 turbine (8) is chosen in accordance with the displacement of the reciprocating engine to set the maximum power of the system at each engine rotation speed. The maximum opening of the VGT2 turbine (8) determines the minimum O2 flow (idle) of the reciprocating engine at each speed. The VGT2 turbine (8) can also comprise a relief valve (or WG). When the VGT2 turbine (8) or its relief valve is fully opened, the energy of compressor C2 (2) is reduced to zero, thereby reducing both the diaphragm working pressure MIEC as the air flow rate considerably transferred.
[0226] If it is desired to reduce the engine flow even further until it drops to zero, then the control valve (72) is opened, avoiding the VGT1 turbine (71), thereby reducing the energy of compressor C1 (10) to zero. This equals the partial pressure of O2 on both sides of the MIEC membrane (6) and cancels the rate of O2 production by leaving the motor load of this embodiment 4 empty.
[0227] In this way, the control valve (72) provides a qualitative regulation of the O2 flow acting on the production rate and the VGT2 turbine (8) provides a quantitative regulation acting on the transferred air flow. Both controls provide a very wide and very fine adjustment of the effective compression ratio of the cylinder in the upper dead center of the second cylinders (14) without changing the volumetric compression ratio of the latter. This is commonly known in reciprocating engines as a variable compression ratio.
[0228] At the output of the VGT2 turbine (8), the mixture of N2 and H2O at a pressure of approximately 0.1 MPa and a temperature of approximately 800 K (526.85 ° C), is passed through the first regenerator (23) to yield its heat to the air before discharging this mixture of gases (already free of gases harmful to health) into the atmosphere.
[0229] The pure O2 in the case of Figure 4a or the O2 diluted with atmospheric CO2 in the case of Figure 4b, leave the MIEC membrane (6) and the CO2 membrane (28) respectively, at a nominal pressure and temperature approximately 0.05 MPa and 1123 K (849.85 ° C) respectively. This is the oxidizing flow, which represents approximately 20% of the air flow transferred by the engine.
[0230] The heat from this oxidizing flow is first recovered in the second regenerator (5) to heat the air coming from the outlet of the first regenerator (23). At the exit of the second regenerator (5) the O2 has nominal conditions of approximately 0.048 MPa and 700 K (426.85 ° C).
[0231] Then the mixture flows through a means to carry out a vacuum Brayton cycle (CBV) (21). The means to carry out a vacuum Brayton cycle (CBV) (21) have the function of cooling the mixture transforming its temperature into pressure and recovering the loss of pressure caused by the second regenerator (5). The means for carrying out a vacuum Brayton cycle (CBV) (21) are composed of a VGT3 turbine (16) mechanically coupled with a C3 compressor (12) with which it forms a turbogroup. Between the VGT3 turbine outlet (16) and the C3 compressor inlet (12) there is a fifth WCAC cooler (31). The internal detail of the means for carrying out a vacuum Brayton cycle (CBV) (21) can be seen in figure 5a) and its operating cycle in the Ts diagram of figure 5b). The mixture of CO2, H2O and O2 is expands for energy recovery in the VGT3 turbine (16); It is cooled under constant pressure in the fifth WCAC cooler (31) and compressed in compressor C3 (12), mechanically coupled with the VGT3 turbine (16). At the outlet of compressor C3 (12) the mixture is colder and at more pressure than at the inlet of the VGT3 turbine (16).
[0232] The nominal conditions of the oxidizing mixture at the outlet of compressor C3 (12) are approximately 0.08 MPa and 473 K (199.85 ° C). The oxidizing mixture, which continues on its way to the second cylinders (14), is cooled in the second WCAC cooler (9) to 323 K (49.85 ° C). The compressor C1 (10) is then compressed to 0.25 MPa and 473 K (199.85 ° C), with the conditions of the compressor C1 (10) being imposed by the control valve (72) to maintain the rate of productivity of the MIEC membrane (6), as already described. After compressor C1 (10), the oxidizing fluid is re-cooled in the third WCAC cooler (11) to 323 K (49.85 ° C).
[0233] In the embodiment of figure 4a the oxidizing fluid is pure O2 and is used to entrain the CO2 in the polymeric CO2 membrane (28) with a CO2 / N2 selectivity of around 2000 to lower the CO2 partial pressure on this side and maximize the efficiency of the membrane to remove CO2 from the air stream. In the embodiment of figure 4b, the oxidizing fluid is already the O2 diluted with atmospheric CO2 at the outlet of the third WCAC cooler (11).
[0234] Next, the oxidizing fluid passes through a first non-return valve (33) to prevent the outflow of reflux from the second cylinders (14). After the first non-return valve (33) the mixture is sucked through the second cylinders (14), which are 2 of the 4 that the four-stroke engine used as an example has, as established at the beginning of the description of the present embodiment 4 .
[0235] In the second cylinders (14), an HxCyOz hydrocarbon is injected, with a fuel pump (26), into the oxidizing mixture O2 (together with CO2 from the air). The fuel pump (26) sucks the fuel from a second tank (27) that is separated with a flexible membrane from the first tank (20) where liquid CO2 accumulates, as will be explained later. As the hydrocarbon accumulated in the second tank (27) is consumed, the membrane reduces the volume on the hydrocarbon side and increases the volume on the CO2 side to allow the accumulation of the latter on its side of the first tank (20). The hydrocarbon sucked by the fuel pump (26) is injected into the second cylinders (14) in the desired way and quantity to regulate the load of the combustion engine by diffusion and in a proportion less than stoichiometric with O2. In said second cylinders (14) a diffusion combustion cycle is carried out; compression ignition and similar to the Diesel cycle that is mainly carried out by O2 and its products from the with bustion. Ie, ^{2 0} % of the mass that circulates through the engine.
[0236] To regulate the combustion tem perature at limits compatible with mATERIAL AND COOLING TECHNOLOGIES OF THE ALTERNATIVE ENGINES INJECTING RANGE OF QUANTITY OF CO 2 LIQUID INTO THE according to two cylinders ( ¹⁴ ). Approximately, this amount is ^{8 0} % of the back mass given by the second two cylinders ( ¹⁴ ) and is injected by the liquid CO 2 pump ( ³⁵ ) at a temperature lower than the critical (< ^{30 3} K ( ^{2 9} , ⁸⁵ ° C)) and high pressure (approximately ⁸⁰ M Pa) inside the cylinders. CO 2 is kept at sub critical temperatures (< ³⁰³ K ( ^{2 9} , ⁸⁵ ° C)) in the pump using or if necessary a refrigeration circuit such as that produced by the vehicle's air conditioning. . The injected CO 2 has been previously captured and liquefied in the previous combustion processes. CO 2 evaporates within two cylinders and expands by performing a supercritical thermodynamic cycle different from that of O2 and its products, which will be written later.
[0237] The second cylinders ( ¹⁴ ) produce energy for over the first cylinders ( ⁴ ) that transfer air for the M IE C membrane ( ⁶ ) and to compress CO 2 during the sca rg up to the sup ercritical pressure; They are all connected to the same crankshaft ( ^{2 5} ). The productivity of the diaphragm responds instantaneously to the engine's cele rations, since the first cylinders ( ⁴ ) are coupled in two ways with the second cylinders ( ¹⁴ ). Therefore, the in m amic response of the engine is not affected by the delay of the turbogroup (due to the mechanical inertia of the same) as it happens in the turbocharged engines with feed ven tio ns. The second cylinders ( ^{1 4} ) also produce a surplus of net mechanical energy used to drive the vehicle to which the engine is coupled, or the electric generator or any appli cation requiring a mechanical energy input through an axis. These two cylinders ( ¹⁴ ) operate as a starting system for the set of turbomachines, to put the flow of air and the turbines of the cycle into motion. To do this, they are moved, until the start of the system, by a conventional starter motor used in alternative motors.
[0238] Heat ascents to the water of the first ( ³ ), second ( ⁹ ), third ( ¹¹ ), fourth ( ¹³ ), fifth ( ³¹ ) and sixth ( ¹⁸ ) WCAC chillers; together with the transfer of heat in the M IE C membrane ( ⁶ ) and in the catalytic M IE C membrane ( ^{1 5} ); in the regenerators according to do ( ⁵ ) and first ( ²³ ) and finally the rest of the d enification and capture of the excess of CO 2 and H2O, sup on the total cession of heat to the cold focus It is necessary for the thermodynamic cycle to comply with the second or beginning of the thermodynamic term and therefore be viable. In turn, the heat transfers in the WCAC chillers first ( ³ ), second ( ⁹ ), third ( ¹¹ ), fourth ( ¹³ ), fifth ( ³¹ ) and sixth ( ¹⁸ ) and in the s re gen erations (produced in the second (5) and first (23) regenerators contribute to minimizing the exergy destruction of the thermodynamic cycle due, on the one hand, to making the overall compression process of the working fluid more isothermal and, on the other hand, to recovering the energy of the exhaust gases for air separation. The approach to isothermal compression and the use of second (5) and first (23) regenerators to extract heat from O2 and CO2 + H2O bring the cycle of air and N2 in the MIEC membrane (6) closer to a cycle with Equal performance to that of Carnot known as Ericsson Cycle. The O2 mix cycle can be assimilated to a supercritical CO2 cycle with intermediate compressions and expansions, but nested with a Diesel cycle in the second cylinders (14); something not described until now in the bibliography. In essence, the supercritical CO2 cycle nested with the Diesel cycle and binary with the N2 cycle (by sending heat to the N2 cycle, it complies with the thermodynamic precepts to approach an ideal cycle of maximum efficiency, such as the Ericsson cycle) is a novel embodiment of a binary cycle; that fulfills the precepts of the other ideal cycle of maximum efficiency, that of Carnot.
[0239] As a result of the combustion of the hydrocarbon (fuel) with the oxidizing mixture (atmospheric CO2 O2), a mixture of unburned CO2, H2O, THC, O2 and CO is produced at the exit of the second cylinders (14). This mixture is oxidized with the O2 left over from combustion in the catalytic MIEC membrane (15), which it enters at a temperature of approximately 1273 K (999.85 ° C) and a pressure of 7.5 MPa. The gases yield their heat to 100% of the air flow that the engine transfers, with which their temperature drops greatly, to approximately 753 K (479.85 ° C). At the same time, and due to the chemical reactions that take place in the catalytic MIEC membrane (15), the CO and THC are oxidized with the O2 left over from combustion to H2O and CO2 vapor, and, again, due to oxy-combustion. NOx production in the second cylinders (14) is avoided. As the ratio between the admitted O2 and the fuel in the second cylinders (14) is not stoichiometric, but superior as an option to regulate the load, O2 may be left over even after oxidizing the CO and THC.
[0240] The 7.5 MPa pressure is regulated by the second non-return valve (19) and its setting spring. Compression is performed instantaneously by opening the exhaust valve of the second cylinders (14) and discharging the exhaust gas mixture. Gases compressed up to 7.5 MPa must be kept above 573 K (299.85 ° C) which is the saturation temperature of water at 7.5 MPa to ensure that it remains in the gas state within the second cylinders (14).
[0241] The mixture is cooled in the fourth WCAC cooler (13) to 523 K (249.85 ° C) so that the H2O becomes liquid. The liquid water is then separated from the CO2 gas in a separator (17), which can be an inertial separator with a pressure valve. pressure lamination at the outlet. A polymeric membrane can also be used as separator (17), if the water is kept in a gaseous state. The mass of water at 7.5 MPa and 473 K (199.85 ° C) represents approximately 10% of the total flow of mass transferred by the engine. The separated water mixes with the N2 + H2O at the inlet of the VGT2 turbine (8). In this way the pressure downstream of the separator (17) is marked by the expansion in the VGT2 turbine (8). This allows the temperature and the mass of the extracted water to be valorized energetically, recovering part of its energy in the VGT2 turbine (8).
[0242] Finally, the CO2 remaining O2 is cooled in the sixth WCAC cooler (18) below 303 K (29.85 ° C) which is its critical temperature. Liquid CO2 passes through the second non-return valve (19) and is stored at 7.5 MPa in a first tank (20) with a controlled temperature below 303 K (29.85 ° C). The tank is maintained at subcritical CO2 temperatures (<303 K (29.85 ° C)) using, if necessary, a refrigeration circuit such as that produced by the vehicle's air conditioning. The O2 gas that may have accumulated in the tank is purged into the atmosphere through a fourth non-return valve (34) when the pressure in the tank exceeds 7.5 MPa. When the fuel in the second tank (27) is empty or the first tank (20) is full, whichever comes first, the autonomy of the engine ends. Both deposits are separated by a flexible membrane. The first tank (20) is discharged of CO2 in the service station, exchanging for fuel that refills the second tank (27). Liquid CO2 can again be converted to a hydrocarbon or stored in controlled sinks, but is not emitted into the atmosphere. The reduction of the CO2 content of the intake air together with the capture of the CO2 generated in the oxy-combustion processes of the fuel makes it possible to determine that the present embodiment 4 is an engine with negative net emissions since it has removed atmospheric CO2 and has not emitted the one that is produces in its combustion process.
[0243] As the liquid CO2 is injected again into the second cylinders (14), with the CO2 pump (35) and in order to keep the combustion temperatures controlled, it performs a novel thermodynamic cycle and one not described until now that has been represented in the figure 6 in the ph diagrams; T-s and p-v respectively. This cycle is energetically relevant for CO2, which represents approximately 80% of the mass contained in the cylinders. The description of the CO2 cycle is as follows:
[0244] (1) .- Station corresponding to the pump inlet. At the entrance of the CO2 pump (35) it is in thermodynamic conditions of approximately 7.5 MPa and 298 K (24.85 ° C).
[0245] (2) .- Station corresponding to the pump outlet. At the outlet of the CO2 (35) it is in thermodynamic conditions of approximately 80 MPa and 303 K (29.85 ° C). The process between stations (1) and (2) is carried out in the CO2 pump and during it the CO2 is kept in a liquid state, compressing in the pump practically isothermally. CO2 is kept at subcritical temperatures (<303 K (29.85 ° C)) during compression, using, if necessary, a refrigeration circuit such as that produced by the vehicle's air conditioning. The station (2 ') of figure 6 corresponds to the moment when the liquid CO2 leaves the nozzle of the injectors and expands to the pressure that it finds in the second cylinders (14) of approximately 20 MPa.
[0246] (3) .- Station corresponding to the end of the hydrocarbon combustion process. In station (3) the maximum temperature and the maximum cycle pressure are reached. Conditions are approximately 1800 K (1526.85 ° C) and 20 MPa. The process is carried out on the second cylinders (14). The CO2 is injected together with the hydrocarbon at the end of the compression stroke. The CO2 expands as soon as it is injected, from 80 MPa upstream of the injection nozzle, to 20 MPa of maximum pressure in the second cylinders (14). The pressure in the second cylinders (14) is kept practically constant at 20 MPa during the process between stations (2 ’) and (3) thanks to the continued injection of CO2 and despite the expansion stroke. The temperature increases to 1800 K (1526.85 ° C) thanks to the combustion of the hydrocarbon.
[0247] (4) .- Station corresponding to the end of the CO2 injection process. The process between (3) and (4) involves a slightly decreasing temperature reduction at pressure. The conditions in (4) are about 1173 K (899.85 ° C) and about 18 MPa. The temperature has decreased due to the dilution of the combustion products with the injected CO2. The pressure has decreased due to the absence of combustion and the increase in volume in the cylinder during the process between (3) and (4).
[0248] (5) .- Station corresponding to the bottom dead center of the cylinders. The process between (4) and (5) implies a continuation of the increase in volume in the cylinders without combustion and without CO2 injection. This supposes a cooling and a drop in pressure. The conditions in (5) are approximately 873 K (599.85 ° C) and 0.3 MPa. The process between (4) and (5) continues to occur in cylinders with closed valves making it an isolated system from the outside. In (5) the volumetric expansion in the cylinders ends, the exhaust valve opens and the exhaust gas discharge or exhaust process begins.
[0249] (6) .- Station corresponding to the end of the escape process. Opening the exhaust valve causes an immediate re-compression of the gas in the cylinders because the discharge area is pressurized to 7.5 MPa by the second non-return valve (19). The process between (5) and (6) assumes an instantaneous increase in pressure and temperature to approximately 7.5 MPa and 1273 K (999.85 ° C).
[0250] The cycle is closed in a cooling process at the constant pressure of 7.5 MPa in which the CO2 goes from a gas to a liquid state following the supercritical pressure line. In this closing of the cycle it returns again to station (1) in the initial conditions of 298 K (24.85 ° C) and 7.5 MPa. This cooling process takes place in part in the cylinders during the exhaust gas discharge process, under constant pressure conditions, for as long as the exhaust valve remains open. The rest of the cooling occurs in the catalytic MIEC membrane (15) and in the fourth (13) and sixth (18) WCAC coolers. Part of the liquefied CO2 mass is reinjected into the cylinders to carry out the described cycle again and the surplus CO2 accumulates in the first tank (20) until it is delivered to the appropriate collection and treatment stations.
[0251] The thermodynamic state where the process line between the thermodynamic states (4) and (5) intersects with the process line between the thermodynamic states (6) and (1) is the point (7), as reflected in the figure 6. The thermodynamic state of point (7) depends on the particular conditions of the cycle and marks the vertex of separation between the part of the cycle that produces positive net mechanical work (1,2,3,4,7,1) and the part the cycle that produces negative net mechanical work (7,5,6,7); that is, it consumes work.
[0252] Although CO2 represents approximately 80% of the mass that evolves through the cylinders, there is another approximately 20% of mass that is O2 that reacts with the fuel. The cycle carried out by O2 and its combustion products is nested with the CO2 cycle inside the second cylinders (14). As it is a cycle not previously proposed in the bibliography, it is also described in detail in figure 7. The stages of this cycle are as follows:
[0253] (a) .- Station corresponding to the thermodynamic conditions in the admission of the second cylinders (14). These conditions are located downstream of the first check valve (33). Thermodynamic conditions are approximately 0.3 MPa and 323 K (49.85 ° C). At this moment the pistons of the second cylinders (14) are in the lower dead center. The intake valve of the second cylinders (14) closes and the O2 compression process begins.
[0254] (b) .- Station corresponding to the thermodynamic conditions at the end of the compression process of the second cylinders (14). These conditions occur at the top dead center of the piston of the second cylinders (14). The conditions thermodynamics are approximately 11 MPa and 573 K (299.85 ° C). In the process between states (a) and (b) there is a polytropic compression, with heat transmission to the cylinder walls, of the O2 trapped in them (approximately 20% of the cycle mass). Under conditions (b), the fuel hydrocarbon and CO2 are injected in a liquid state.
[0255] (c) .- Station corresponding to the thermodynamic conditions at the end of the combustion process of the hydrocarbon fuel. These conditions occur after the upper dead center of the piston of the second cylinders (14). Thermodynamic conditions are approximately 200 MPa and 1800 K (1526.85 ° C). The process between (b) and (c) involves the injection of the fuel, its auto-ignition by compression and its combustion by diffusion, controlling the speed of combustion thanks to the amount of movement of the injected jets. The process between (b) and (c) also involves the injection of the liquid CO2 that will control the temperature of the combustion process and helps to keep the pressure constant and equal to the approximately 200 MPa established. These conditions coincide with those of the thermodynamic state (3) of the CO2 cycle in Figure 6. Under these conditions, both cycles (O2 and CO2) occur in unison.
[0256] (d) .- Station corresponding to the thermodynamic conditions at the end of the CO2 injection process. These conditions occur during the expansion stroke of the piston of the second cylinders (14). Thermodynamic conditions are around 1173 K (899.85 ° C) and approximately 18 MPa. These conditions coincide with those of the thermodynamic state (4) of the CO2 cycle in Figure 6. Under these conditions both cycles (O2 and CO2) occur in unison. The process between states (c) and (d) of figure 7 is identical to that described in figure 6 between states (3) and (4). The process is more or less prolonged depending on the amount of CO2 injected, which in turn depends on the final desired temperature in the combustion products and on the stability of the combustion. An ideal case, represented in figure 7 by the point (d ’), would be to extend this process to the bottom dead center of the expansion stroke. This case is ideal since it would suppose the maximum production of work in the cycle of O2 and in that of CO2.
[0257] (e) .- Station corresponding to the thermodynamic conditions at the bottom dead center of the piston stroke of the second cylinders (14). These conditions occur at the end of the expansion process in the second cylinders (14). Thermodynamic conditions are approximately 873 K (599.85 ° C) and 0.3 MPa. These conditions coincide with those of the thermodynamic state (5) of the CO2 cycle in Figure 6. Under these conditions, both cycles (O2 and CO2) occur in unison. The process between states (d) and (e) of figure 7 is identical to that described in figure 6 between states (4) and (5).
[0258] (f) .- Station corresponding to the thermodynamic conditions when the exhaust valve opens at the bottom dead center of the piston stroke of the second cylinders (14). When the exhaust valve opens, there is an instantaneous re-compression of the gas in the cylinders because the discharge area is pressurized to 7.5 MPa by the second non-return valve (19). These conditions coincide with those of the thermodynamic state (6) of the CO2 cycle in Figure 6. Under these conditions, both cycles (O2 and CO2) occur in unison. The process between states (e) and (f) of figure 7 is identical to that described in figure 6 between states (5) and (6). The process between (e) and (f) assumes an instantaneous increase in pressure and temperature to approximately 7.5 MPa and 1273 K (999.85 ° C).
[0259] (g) .- Station corresponding to the thermodynamic conditions when the combustion gas discharge is completed, at the upper dead point of the piston exhaust stroke of the second cylinders (14). In the process between station (f) and (g), the gases are also discharged from the cylinders, under constant pressure conditions, for the entire time that the exhaust valve remains open until it closes. Thermodynamic conditions are approximately 7.5 MPa and 1173 K (899.85 ° C). In these conditions both cycles (O2 and CO2) happen in unison. The process between states (f) and (g) of figure 7 coincides during a certain section at constant pressure with that described in figure 6 between states (6) and (1). At this station the O2 and CO2 cycles are separated again.
[0260] (h) .- Station corresponding to the end of the pressure drop process in the second cylinders (14), up to the intake pressure, downstream of the first non-return valve (33). This station occurs at some point in the intake stroke of the second cylinders (14). In the process between (g) and (h) the CO2 trapped in the dead volume of the combustion chamber has expanded to the conditions in which the first non-return valve (33) is opened. This process occurs with the first non-return valve (33) closed. This process is carried out only by the CO2 from the combustion of O2 and exclusive to the cycle in figure 7 and is independent of the CO2 cycle described in figure 6. The thermodynamic conditions are approximately 0.3 MPa and 773 K (499, 85 ° C).
[0261] The cycle is closed again under the thermodynamic conditions (a) of figure 7. The process between (h) and (a) occurs with the first non-return valve (33) open at essentially constant pressure and temperature and approximately 0.3 MPa and 323 K (49.85 ° C). The process between (h) and (a) consists of the admission of O2 from the intake of the cylinders and involves the entry of approximately 20% of the air mass of the system.
[0262] The thermodynamic state where the process line between the thermodynamic states (d) and (e) intersects with the process line between the thermodynamic states (f) and (g) is the point (i), as shown above in figure ⁷ . Point (i) coincides with the thermodynamic state ( ⁷ ) in figure ⁶ . The thermodynamic state of point (i) depends on the particular conditions of the cycle in figure ⁷ and marks the vertex of separation between the part of the cycle which produces positive net mechanical work (i , j, b, c, d, i) and a part of the cycle that produces negative net mechanical work (i, e, f, i); That is to say, with your work, as was rewritten in figure ⁶ . As was written earlier, point (d ') in Figure ⁷ represents an ideal situation in the cycle described in which points (f) and
[0263] they are coincident. In this case, the area (i ', f, e, i') is zero and therefore the net work produced is maximized, understood as the absolute difference between positive work and negative work. .
[0264] In the O2 cycle in figure ⁷ there is another area with its work whose vertex is the point (j). As shown in figure ⁷ , point (j) is the thermodynamic state where the process line intersects between the thermodynamic states (a) and (b) with the line of the process between the thermodynamic states (f) and (g). The thermodynamic state of the point (j) depends on the conditions that are particular to the cycle of the figure.
[0265] ⁷ and marks the vertex of separation between the part of the cycle that produces positive net mechanical work (i, j, b, c, d, i) and the other part of the cycle that produces negative net mechanical work (j, g, h, a, j); that is, with his work I do.
[0266] A theoretical pre-design modeling was carried out and various calculations were carried out at the same time, the results of which are shown in the graphs in Figures ⁸ to ¹³ attached. For the model, ideal connections between the elements and an efficiency of the aquarium turbom and constant heat exchangers are provided at all operating points.
[0267] A constant entrapped air mass and variable fuel injection rate are also used in the engine cylinders and the compressor, as well as a stoichiometric dose. The fuel considered was C8H18 (PCI ^{~ 42} MG / kg).
[0268] A maximum compression ratio of the turbocompressors was set and set at
[0269] ⁴ : ¹ , a maximum temperature of the refrigerant of ⁹⁰ ° C and a maximum temperature of the gas of e sc ape of ¹⁰⁵⁵ ° C.
[0270] As can be seen from the graphs in Figures ⁸ to ¹³ , and from the previous description, with the present invention, NO x emissions are avoided and open the possibility of cutting CO 2 instead of releasing it into the atmosphere. In addition, the load is regulated without the need for a m ripo sa valve in the intake line and high efficiency and specific power per unit of displacement are obtained. .
[0271] Although a detailed description of preferred embodiments of the present invention has been provided, it will be understood by one skilled in the art that modifications and variations may be applied thereto without thereby departing from the scope of protection defined exclusively by the appended claims.

权利要求:
Claims (37)
[1]
1. Internal combustion engine, of the type that sucks atmospheric air as an oxidizer and uses hydrocarbons as fuel, the engine comprising: - a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with overheating, by mixing a part of the nitrogen, which comprises a MIEC membrane (6) that separates the O ² from the compressed air, so that the suction air stream is free of N ² , and depleted air from the rejection of the MIEC membrane (6) is it directly sends to a stream of exhaust gases avoiding its participation in a subsequent combustion, in which part of the air compressions are carried out in at least a first cylinder (4) of the engine;
- a second Brayton cycle with compression with intermediate cooling, binary combined with the first Brayton cycle and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-combustion in at least a second cylinder (14) of the motor,
wherein the second Brayton cycle transmits mechanical energy to the first Brayton cycle by coupling the at least a first cylinder (4) with the at least a second cylinder (14) through a crankshaft (25), as well as energy thermal from exhaust gases;
in which the first cycle of Brayton provides the second cycle of Brayton O ² compressed from the MIEC membrane (6);
whereby the emission of NOx into the atmosphere is avoided by the separation of N ² in the MIEC membrane (6).
[2]
2. Engine according to claim 1, characterized in that it comprises two first cylinders (4).
[3]
3. Engine according to any of the preceding claims, characterized in that it comprises two second cylinders (14).
[4]
Motor according to any of the preceding claims, characterized in that the net mechanical energy produced by the first Brayton cycle is used to supercharge the second Brayton cycle through a C1 compressor (10).
[5]
5. Engine according to any of the preceding claims, characterized in that the MIEC membrane (6) produces pure O ² separated from atmospheric air.
[6]
6. Engine according to any of claims 1 to 4, characterized in that the MIEC membrane (6) produces O ² diluted with CO ² .
[7]
7. Engine according to claim 6, characterized in that the CO ² with which it is diluted O ² is obtained from atmospheric air.
[8]
8. Engine according to claim 6, characterized in that the CO ² with which the O ² is diluted is produced by combustion with hydrocarbon in the second Brayton cycle.
[9]
9. Engine according to any of the preceding claims, characterized in that there is always a cooling stage after each compression stage.
[10]
10. Engine according to any of the preceding claims, characterized in that heat is recovered from all residual sources by combining the first and second Brayton cycles with regenerations before each cooling.
[11]
11. Engine according to any of the preceding claims, characterized in that the mechanical energy produced by the second Brayton cycle is also used to compress the CO ² produced until liquefying it.
[12]
12. Engine according to claim 11, characterized in that the CO ² is compressed to at least 7.5 MPa.
[13]
13. Engine according to any of claims 11 and 12, wherein the second Brayton cycle is nested with an Otto cycle, characterized in that the engine comprises at least one additional piston (22) as well as first and second non-return valves ( 33, 19) at the inlet and downstream of the same to suck and compress excess CO ² accumulated in engine ducts.
[14]
14. Engine according to any of claims 11 and 12, in which the second Brayton cycle is nested with a Diesel cycle, characterized in that the exhaust stroke of the second cylinders (14) is used to compress the CO ² , by the use of first and second non-return valves (33, 19) that allow the discharge of CO ² and the admission of substantially pure O ² , the latter being used as entrainment gas in selective CO ² separation membranes.
[15]
15. Engine according to any of claims 5 or 6, characterized in that it further comprises a vacuum Brayton cycle (CBV) to cool down substantially pure O ² , or O ² diluted with CO ² , before subsequent compression .
[16]
16. Engine according to any of claims 11 to 15, characterized in that it comprises a first tank (20) for storing liquefied CO ² produced.
[17]
17. Engine according to claim 16, characterized in that the CO ² stored in the first tank (20) is used to pump fuel from a second tank (27) to the second cylinders (14) of the engine and both first and second tanks ( 20, 27) are in the same tank separated by a flexible membrane.
[18]
18. Engine according to any of claims 11 to 17, characterized in that the liquefied CO ² produced is transferred to a supplier of an external CO ² logistics network.
[19]
19. Motor according to any of the preceding claims, characterized in that the MIEC membrane (6) is based on crystalline ceramic materials that have mixed conduction of electronic carriers and oxygen ions.
[20]
20. Engine according to any of the preceding claims, the engine being the type of ignition caused (SI), characterized in that turbogroups are used to supercharge the first cylinders (4) and the regulation of the production of O ² of the membrane is used MIEC (6) to regulate the motor load.
[21]
21. Engine according to any of claims 1 to 19, the engine being of compression ignition (CI) type, characterized in that turbogroups are used to supercharge the first cylinders (4) and the regulation of the production of O ^{2 is used} of the MIEC membrane (6) to regulate the effective compression ratio of the working fluid in the engine cycle.
[22]
22. Internal combustion engine operating method, of the type that sucks in atmospheric air as an oxidizer and uses hydrocarbons as fuel, the method comprising:
- a first regenerative Brayton cycle of air compressions with intermediate cooling and nitrogen expansions with reheating, by mixing a part of the nitrogen, which comprises separating the O ² from the compressed air, so that the suction air stream is free of N ² , and an impoverished air from the rejection of the separation is sent directly to an exhaust gas stream avoiding its participation in a subsequent combustion;
- a second Brayton cycle with compression with intermediate cooling, combined in a binary way with the first Brayton cycle and nested with a cycle selected from an Otto cycle and a Diesel cycle carried out by oxy-fuel,
in which the second Brayton cycle transmits mechanical energy as well as thermal energy from exhaust gases to the first Brayton cycle;
wherein the first Brayton cycle provides the second Brayton cycle with O ² compressed from separation;
whereby the emission of NOx into the atmosphere is avoided by the separation of N2.
[23]
23. Method according to claim 22, characterized in that the net mechanical energy produced by the first Brayton cycle is used to supercharge the second Brayton cycle.
[24]
24. Method according to any of claims 22 and 23, characterized in that the first Brayton cycle produces pure O ² separated from atmospheric air.
[25]
25. Method according to any of claims 22 to 23, characterized in that the first cycle of Brayton produces O ² diluted with CO ² .
[26]
26. Method according to claim 25, characterized in that the CO ² with which the O ² is diluted is obtained from atmospheric air.
[27]
27. Method according to claim 25, characterized in that the CO ² with which the O ² is diluted is produced by combustion with hydrocarbon in the second Brayton cycle.
[28]
28. Method according to any of claims 22 to 27, characterized in that there is always a cooling stage after each compression stage.
[29]
29. Method according to any of claims 22 to 28, characterized in that heat is recovered from all residual sources by combining the first and second Brayton cycles by performing regenerations before each cooling.
[30]
30. Method according to any of claims 22 to 29, characterized in that the mechanical energy produced by the second Brayton cycle is also used to compress the CO ² produced until liquefying it.
[31]
31. The method according to claim 30, characterized in that the CO ² is compressed to at least 7.5 MPa.
[32]
32. The method according to any of claims 30 and 31, wherein the second Brayton cycle is nested with an Otto cycle, characterized in that it comprises sucking and compressing excess CO ² accumulated in engine ducts.
[33]
33. Method according to any of claims 30 and 31, in which the second Brayton cycle is nested with a Diesel cycle, characterized in that it comprises compressing CO ² , allowing the discharge of CO ² and the admission of substantially pure O ² , the latter being used as entrainment gas in selective CO ² separation membranes.
[34]
34. The method according to any of claims 24 or 25, characterized in that it further comprises a vacuum Brayton cycle (CBV) to cool down substantially pure O ² , or O ² diluted with CO ² , before subsequent compression .
[35]
35. Method according to any of claims 30 to 34, characterized in that it comprises storing liquefied CO ² produced.
[36]
36. Method according to claim 35, characterized in that it comprises using the stored CO ² to pump fuel towards the engine cylinders.
[37]
37. Method according to any of claims 30 to 36, characterized in that it comprises transferring the liquefied CO ² produced to a supplier of an external CO ² logistics network.

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优先权:

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申请号 | 申请日 | 专利标题

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ES201930285A|ES2751129B2|2019-03-28|2019-03-28|INTERNAL COMBUSTION ENGINE AND ITS OPERATION METHOD|ES201930285A| ES2751129B2|2019-03-28|2019-03-28|INTERNAL COMBUSTION ENGINE AND ITS OPERATION METHOD|

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CN202080039226.6A| CN113874618A|2019-03-28|2020-03-21|Internal combustion engine and method for operating the same|

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EP20776540.5A| EP3951159A1|2019-03-28|2020-03-21|Internal combustion engine and operating method of same|

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PCT/ES2020/070199| WO2020193833A1|2019-03-28|2020-03-21|Internal combustion engine and operating method of same|

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KR1020217035313A| KR20220011622A|2019-03-28|2020-03-21|Internal combustion engines and how they work|