 Efficient gas turbine engine
专利摘要:
The invention relates to a highly efficient gas turbine engine. The blower of the gas turbine engine is driven from a turbine via a reduction gear, so that the blower has a lower rotational speed than the drive turbine, which provides gains efficiency. The efficient blower system is coupled to a core which has low cooling flow requirements and / or high temperature capacity, and which can have a particularly low mass for a given power. Figure 4 公开号:FR3084909A1 申请号:FR1908742 申请日:2019-07-31 公开日:2020-02-14 发明作者:Roderick M Townes；Pascal Dunning；Michael J WHITTLE 申请人:Rolls Royce PLC； IPC主号:
专利说明:
Description Title of the invention: Efficient gas turbine engine [0001] The present description relates to an efficient gas turbine engine. Aspects of the present description relate to a gas turbine having a fan driven by means of a reducer and a highly efficient engine core. The design of a gas turbine engine must take into account a number of competing factors. In general, it is desirable to minimize fuel consumption and weight. However, gas turbine engines have been used and developed for many years, and thus the underlying designs are mature. This high level of design maturity means that progress made, for example, in reducing fuel consumption and / or weight has been relatively small and progressive in recent years. It is desirable to improve the rate of development of gas turbine engines. According to one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A first turbine, a first compressor, and a first heart shaft connecting the first turbine to the first compressor; A second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation as the first heart shaft, the gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft (26) and outputs a drive to the blower so as to drive the blower at a lower speed of rotation than the first heart shaft, in which : A turbine inlet temperature (T0 tur b_in) is defined as the temperature (K) at the inlet to the turbine rotor most axially upstream in the gas turbine engine under a condition of maximum power of the gas turbine engine; A heart size is defined as [Math 1] [0012] fT0comp_out CS = Wcomp in .-------- P0comp_out [0013] where: Wcomp_in is the mass flow (kg / s) at the inlet of the engine core; T0comp_out is the stagnation temperature at the outlet to the compressor; P0comp_out is the stagnation pressure at the outlet to the compressor; and an efficiency ratio of the heart blower FC is at least 1.9 x 10 5 mkg * sPa, where the efficiency ratio of the heart blower is defined as [Math 2] [0018] ______ FC = (fan diameter). TOt ^ b - in Wcomp_in can be described as the mass flow at the inlet to the first compressor. T0comp_out can be described as the stagnation temperature at the outlet to the second compressor. P0comp_out can be described as the stagnation temperature at the outlet to the second compressor. The efficiency ratio of the TC core blower can be in a range having a lower limit of 1.9 x 10 5 , 2 x 10 5 , or 2.1 x 10 5 mkg * sPa and an upper limit 2.5 x 10 5 , 3 x 10 5 , or 3.5 x 10 5 mkg * sPa. The present inventors have found that the supply of a gas turbine engine with an efficiency ratio of the core blower in the ranges defined here - which is greater than conventional engines - can provide a turbine engine. particularly efficient. Strictly by way of example, one way of achieving such an efficiency ratio of the core blower is by the optimal use of ceramic matrix composites in a gas turbine engine having a blower which is driven from a turbine via a reduction box. The first and / or the second turbine may comprise at least one composite component with a ceramic matrix. The second turbine can include at least one ceramic matrix composite component, which can be in the range of 2% to 15% of the total mass of the second turbine. In a conventional manner, the components in a turbine section of a gas turbine engine are manufactured using a metal alloy, such as a nickel alloy. However, in order to obtain greater engine efficiency, it has been found desirable to increase the temperature of the flow of core gas entering the turbine from the combustion chamber. Typically, in operation, the temperature of the gas flowing past some of the components in the turbine is close to or above the melting point of these components. Thus, in order to guarantee that such components have a sufficient service life, they require significant cooling. Such cooling is typically provided using air from the compressor which bypasses the combustion chamber. The cooling flow which bypasses the combustion chamber results in reduced engine efficiency, because this flow is simply compressed in the compressor and then expanded through the turbine. In addition, in order to minimize the amount of cooling flow that is used, and thus minimize the impact on the efficiency of the engine, the cooling flow must be used as efficiently as possible. For example, the cooling passages used to cool such turbine components are typically complex, requiring extensive design and complex manufacturing techniques. This significantly increases the cost of the gas turbine engine. Also, the cooling system itself adds mass to the engine. Selective use of ceramic matrix composites (CMC) in its turbine can be advantageous. For example, the use of CMC may not be really appropriate in all areas. Knowing this, the inventors have derived the optimal level of use of CMC in the turbine so that it is within the ranges claimed. For example, while the thermal capacity of CMCs - which is typically greater than their metallic counterparts - may lend themselves to use in certain areas, the reduced thermal conductivity of CMCs (compared to an equivalent metallic component) means that they can not be suitable in certain other areas. Strictly by way of nonlimiting example, the hottest parts of the turbine can undergo temperatures which even exceed the capacity of the CMCs, and thus require a certain degree of cooling flow. In such a case, it may be more appropriate to use a metal rather than a CMC, due to the higher thermal conductivity of the metals potentially improving the efficiency of the cooling flow for removing heat from the component. Strictly by way of example, where it is used, the CMC can be SiC-SiC (that is to say fibers of silicon carbide in a matrix of silicon carbide). However, it should be borne in mind that any suitable CMC can be used, and indeed the turbine can comprise more than one composition of CMC (for example having different elements). Any suitable manufacturing process can be used for CMC, such as a vapor deposition process or a steam infusion process. The turbine may include stator vanes, rotor blades, sealing rings (for which it can be said that they together form a generally annular ring radially outside the rotor blades), discs rotor (on which rotor blades are provided), one or more radially inner shell elements and one or more radially outer shell elements. The turbine mass can be the total mass of all these turbine components. In arrangements including CMCs, the minimum mass of the ceramic matrix composite in the second turbine can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the total mass of the second turbine. The maximum mass of ceramic matrix composite in the second turbine can be 20%, 15%, 14%,%, 12%, 11%, 10%, 9%, 8%, 7%, 6% or 5% of the total mass of the second turbine. The mass of ceramic matrix composite in the second turbine as a percentage of the total mass of the second turbine can be in a range having any of the minimum percentages listed above as a lower limit and any maximum compatible percentage listed above as upper limit. We can say that the second turbine is axially upstream of the first turbine. The first turbine may comprise at least one composite component with a ceramic matrix. In arrangements including CMCs, the mass of ceramic matrix composite in the first and second turbines may be in the range of 1% to 15%, possibly 2% to 12%, of the total mass of the first and second turbines. In arrangements including CMCs, the minimum mass of ceramic matrix composite in the first and second turbines can be 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9% or 10% of the total mass of the first and second turbines. In arrangements including CMCs, the maximum mass of ceramic matrix composite in the first and second turbines can be 20%, 15%, 14%, 13%, 12%, 11%, 10%, 9%, 8%, 7%, 6% or 5% of the total mass of the first and second turbines. The mass of ceramic matrix composite in the first and second turbines as a percentage of the total mass of the first and second turbines can be in a range having any of the minimum percentages listed above as the lower limit and n any compatible maximum percentage listed above as an upper limit. As indicated above, the percentages of CMC used in the turbine described and claimed here are based on information on the most suitable components for which CMCs are used, taking into account, among other things, the variation of temperature across the turbine. Non-limiting examples of metallic and CMC components are provided below in the gas turbine engine. The turbine can comprise at least one row of stator blades. The most axially upstream row of stator vanes can be metallic. As a variant, the most axially upstream row of stator vanes may be in CMC. The most axially upstream row of stator vanes can be directly downstream of the combustion chamber. For example, there may be no rotor blades between the combustion chamber and the stator vanes. The terms "upstream" and "downstream" are used here in the conventional manner, that is to say with respect to the flow through the engine in normal use. Thus, for example, the compressor and the combustion chamber are in the upstream direction relative to the turbine. The turbine can include at least one row of rotor blades. The most axially upstream row of rotor blades can be metallic. Alternatively, the most axially upstream row of rotor blades may be CMC. The most axially upstream row of rotor blades can be directly downstream of the most axially upstream row of stator blades. The most axially upstream row of rotor blades and / or the most axially upstream row of stator blades may comprise one or more internal cooling passages and / or film cooling holes, for example when the blades and / or blades are metallic. Such internal cooling passages and / or film cooling holes can be provided with the cooling flow from the compressor which has bypassed the combustion chamber. A CMC component may or may not be provided with internal cooling passages and / or film cooling holes. The most axially upstream row of rotor blades in the turbine can be a part of the second turbine. The most axially upstream row of stator vanes in the turbine can be a part of the second turbine. The most axially upstream row of rotor blades in the turbine can be radially surrounded by sealing segments. Such sealing segments may include a ceramic matrix composite. In general, the sealing segments can form the radially outer limit (which can be annular and / or frustoconical) inside which the turbine blades rotate during use. The radially outer ends of the turbine blades may be adjacent to the radially inner surface of the sealing segments. The turbine may include at least two rows of stator vanes. The second most axially upstream row of stator vanes (which may be directly downstream axially from the most upstream row of rotor blades) may comprise a ceramic matrix composite. The turbine can include at least two rows of rotor blades. The second most axially upstream row of rotor blades may comprise a ceramic matrix composite. The second most axially upstream row of rotor blades in the turbine can be a part of the second turbine. The second most axially upstream row of stator vanes in the turbine may be a part of the second turbine. The second most axially upstream row of rotor blades can be radially surrounded by sealing segments made of ceramic matrix composite. The second turbine can comprise any number of rows of stator blades (for example 1, 2, 3, 4, 5 or 6), and one or more of these can comprise a matrix composite ceramic. The second turbine can include any number of rows of neighboring rotor blades and / or sealing rings (e.g. 1, 2, 3, 4, 5 or 6), and one or more of these can include a ceramic matrix composite. The most axially upstream row of stator vanes in the first turbine (which may be directly downstream of the most axially downstream row of rotor blades in the second turbine) may comprise a ceramic matrix composite . The most axially upstream row of rotor blades in the first turbine can comprise a ceramic matrix composite. The most axially upstream row of rotor blades in the first turbine can be surrounded by ceramic matrix composite sealing rings. In any aspect of this description, any (s) rotor blades, stator blades or sealing rings (that is to say a sealing part which forms at least part of the radially external flow path around a row of rotor blades) which undergo a maximum temperature at a maximum power condition to which the motor is certified (which can be commonly known as the "line condition red ”) in the range from 1300 K to 2200 K for example in a range having a lower limit of 1300 K, 1400 K or 1500 K and an upper limit of 1900 K, 2000 K, 2100 K or 2200 K - can be manufactured using a CMC. In some arrangements, most, or even all, of the rotor blades undergoing "red line" temperatures within such ranges can be fabricated using CMC. In some arrangements, most, or even all, of the stator vanes undergoing "red line" temperatures within such ranges can be fabricated using CMC. In some arrangements, most, or even all, of the sealing rings undergoing "red line" temperatures within such ranges can be fabricated using CMC. Rotor blades, stator vanes, and sealing rings that do not experience "red line" temperatures within such ranges can be fabricated using a metal, such as a nickel alloy. In one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A turbine, a combustion chamber, and a compressor, the turbine comprising a first turbine and a second turbine and the compressor comprising a first compressor and a second compressor; A first heart shaft connecting the first turbine to the first compressor; A second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation than the first heart shaft, the motor gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft and outputs a drive to the blower so as to drive the blower at a lower speed than the first heart shaft, in which: The second turbine comprises at least one composite component with a ceramic matrix; and the mass of ceramic matrix composite in the second turbine is in the range from 2% to 15% of the total mass of the second turbine. In one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A turbine, a compressor, and a combustion chamber; A fan comprising a plurality of fan blades; and a reduction gear which receives an input from at least part of the turbine and delivers at the output a drive to the blower so as to drive the blower at a lower speed of rotation than the first heart shaft, in which : The turbine comprises at least one composite component with a ceramic matrix; and the mass of ceramic matrix composite in the turbine is in the range from 1% to 15% of the total mass of the turbine, for example in the range from 2% to 15%. In one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A turbine, a combustion chamber, and a compressor, the turbine comprising a first turbine and a second turbine and the compressor comprising a first compressor and a second compressor; A first heart shaft connecting the first turbine to the first compressor; A second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation than the first heart shaft, the motor gas turbine engine further comprising: A bypass radially outside the engine core; A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft (26) and outputs a drive to the blower so as to drive the blower at a lower speed of rotation than the first heart shaft, in which : Part of the flow which enters the engine core bypasses the combustion chamber and is used as a turbine cooling flow to cool the turbine; The fan diameter is greater than 225 cm and / or the turbine inlet temperature, defined as the temperature at the inlet of the turbine rotor most axially upstream at a condition of maximum engine power gas turbine, is greater than 1800 K; and at cruising conditions, the efficiency ratio of the cooling flow to the bypass flow is less than 0.02. The cooling to bypass efficiency ratio can be in the range from 0.005 to 0.02. The bypass cooling efficiency ratio can be in a range having a lower limit of 0.005, 0.006, 0.007 or 0.008, and an upper limit of 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019 or 0, 02. The bypass cooling efficiency ratio can be defined as the ratio of the mass flow rate of the turbine cooling flow to the mass flow rate of the bypass flow at the engine. The ratio can be defined at engine cruising conditions. Such a bypass cooling efficiency ratio - which is lower than conventional engines - can provide a particularly efficient gas turbine engine. In one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A first turbine, a first compressor, and a first heart shaft connecting the first turbine to the first compressor; A second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation that the first heart tree; the gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft and outputs a drive to the fan so as to drive the fan at a lower speed than the first heart shaft, in which: The total mass of the turbine is not more than 17% of the total dry mass of the gas turbine engine. The total mass of the turbine may be the mass of the first turbine plus the mass of the second turbine, for example when there is no additional turbine in the engine. The total mass of the turbine as a percentage of the total dry mass of the gas turbine engine can be in a range having a lower limit of 7%, 8%, 9% or 10%, and an upper limit 13%, 14%, 15%, 16% or 17%. The mass of the second turbine can be at most 7%, 8% or 9% of the total dry mass of the gas turbine engine. The mass of the second turbine as a percentage of the total dry mass of the gas turbine engine can be in a range having a lower limit of 3%, 4% or 5% and an upper limit of 7%, 8% or 9%. The total dry mass of the gas turbine engine can be defined as being the mass of the entire gas turbine engine prior to the exception of fluids (such as oil and fuel) before installation on an aircraft, that is, not including installation features, such as a pylon or nacelle. The supply of a gas turbine engine with a turbine mass in the ranges defined here - which is less than conventional engines having a fan which is driven from a turbine by means of a reduction box - can provide a particularly efficient gas turbine engine. In one aspect, a gas turbine engine is provided for an aircraft comprising: an engine core comprising: A first turbine, a first compressor, and a first heart shaft connecting the first turbine to the first compressor; A second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation as the first heart shaft, the gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft and outputs a drive to the fan so as to drive the fan at a lower speed than the first heart shaft, in which: The maximum net engine thrust at sea level is at least 160 kN; and the normalized thrust is in the range from 0.25 to 0.5 kN / kg. The normalized thrust can be defined as the maximum net thrust (in kN) of the engine at sea level divided by the total mass of the turbine. The total mass of the turbine can be the total mass of the first turbine and the second turbine, for example when there is no additional turbine in the engine. The normalized thrust can be in a range having a lower limit of 0.2, 0.25 or 0.3 kN / kg and an upper limit of 0.45, 0.5 or 0.55 kN / kg. The supply of a gas turbine engine with a standard thrust in the ranges defined here - which is greater than conventional engines - can provide a particularly efficient gas turbine engine. According to one aspect, a gas turbine engine is provided for an aircraft comprising: [0105] an engine core comprising: A first turbine, a first compressor, and a first heart shaft connecting the first turbine to the first compressor; A second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation as the first heart shaft, the gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft and outputs a drive to the fan so as to drive the fan at a lower speed of rotation than the first heart shaft, in which: Part of the flow which enters the engine core bypasses the combustion chamber and is used as a turbine cooling flow to cool the turbine; A cooling flow requirement is defined as the ratio of the mass flow rate of the turbine cooling flow to the mass flow rate of the flow entering the engine core (B) at cruising conditions; A turbine inlet temperature is defined as the temperature (K) at the inlet to the turbine rotor most axially upstream in the gas turbine engine at a condition of maximum engine power at gas turbine ; and the cooling efficiency ratio, defined as the ratio between the turbine inlet temperature and the cooling flow requirement, is in the range from 8000 to 20000 K. The cooling efficiency ratio can be in a range having a lower limit of 8000, 9000 or 10 000 K, and an upper limit of 18 000, 20 000 or 22 000. The supply of a gas turbine engine with a cooling efficiency ratio within the ranges defined here - which is higher than conventional engines - can provide a particularly efficient gas turbine engine. In one aspect, a gas turbine engine is provided for an aircraft comprising: [0117] an engine core comprising a turbine, a compressor, and a heart shaft connecting the turbine to the compressor; A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the heart shaft and delivers a drive to the fan at the output so as to drive the fan at a lower speed of rotation than the heart shaft, in which: At a maximum power condition, the ratio of the turbine inlet temperature (K) to the blower speed in rpm is at least 0.7 K / rpm. The maximum power condition can correspond to the “red line” condition defined elsewhere in this document. The ratio of the turbine inlet temperature (K) to the fan speed in rpm can be in a range having a lower limit of 0.7, 0.8 or 0.9 and an upper limit 1.5, 1.6, 1.7, 1.8, 1.9 or 2. The supply of a gas turbine engine with a ratio of the turbine inlet temperature (K) to the fan speed in rpm within the ranges defined here - which is higher than conventional engines - can provide a particularly efficient gas turbine engine. In one aspect, a gas turbine engine is provided for an aircraft comprising: [0125] an engine core comprising: A first turbine, a first compressor, and a first heart shaft connecting the first turbine to the first compressor; A second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate at a higher speed of rotation as the first heart shaft, the gas turbine engine further comprising: A fan comprising a plurality of fan blades; and a reduction gear which receives an input from the first heart shaft (26) and outputs a drive to the blower so as to drive the blower at a lower speed of rotation than the first heart shaft, in which : A turbine inlet temperature (T0 turb _i n ) is defined as the temperature (K) at the inlet to the turbine rotor most axially upstream in the gas turbine engine under one condition maximum power of the gas turbine engine; A heart size is defined as [Math 3] [0132] CS = Wcomp in . fT0comp_out P0comp_out [0133] where: Wcomp_in is the mass flow rate (kg / s) at the inlet of the engine core; T0comp_out is the stagnation temperature at the outlet to the compressor; P0comp_out is the stagnation pressure at the outlet to the compressor; and [0137] a heart thrust efficiency ratio TC is at least 1.5 x 10 7 kNkg * sPa, where the heart thrust efficiency ratio is defined as [Math 4] [0138] TC = {Maximum net thrust at sea level '). Wcomp_in can be described as the mass flow at the inlet to the first compressor. T0comp_out can be described as the stagnation temperature at the outlet to the second compressor. P0comp_out can be described as the stagnation temperature at the outlet to the second compressor. The efficiency ratio of the push to the heart TC can be in a range having a lower limit of 1.5 × 10 7 , 1.6 × 10 7 , 1.7 × 10 7 , 1.8 × 10 7 , 1.9 x 10 7 or 2 x 10 7 kNkg 1 sPa and an upper limit of 3 kNkg * sPa, 3.5 x 10 7 kNkg * sPa or 4 kNkg 'sPa. The supply of a gas turbine engine with an efficiency ratio of the thrust to the heart within the ranges defined here - which is higher than conventional engines - can provide a particularly efficient gas turbine engine. The specialist will have in mind that except when mutually exclusive, a characteristic or relationship described in relation to any of the above aspects can be applied to any other aspect. In addition, except when mutually exclusive, any characteristic or relationship described here can be applied to any aspect and / or combined with any other characteristic or relationship described here. By way of nonlimiting example, any one or more of any of the following characteristics and / or relationships described here and listed below with respect to any aspect may be combined independently of any of the other characteristics or relationships and / or included in any other aspect of the invention: [0144] * the mass of ceramic matrix composite in the second turbine as a percentage of the total mass of the second turbine [0145] · the mass of ceramic matrix composite in the turbine as a whole as a percentage of the total mass of the turbine as a whole [0146] · the turbine inlet temperature [0147] * the efficiency ratio of the cooling flow to the bypass flow [0148] · the total mass of the turbine as a percentage of the total dry mass of the gas turbine engine [0149] · the standard engine thrust [0150] · the cooling efficiency ratio [0151] · the ratio of the turbine inlet temperature (K) to the blower speed in rpm [0152] * the efficiency ratio of the TC core thrust [0153] · the efficiency ratio of the core blower [0154] As used here, the temperature d turbine inlet, which may be designated TET, may be be defined as the maximum temperature at the inlet to the rotor stage most axially upstream of the turbine measured at a maximum power condition. The maximum power condition may be the maximum power condition to which the engine is certified, and may represent the maximum temperature at this location during engine operation. Such a condition is commonly referred to as a "red line" condition. Such a condition can occur, for example, under a strong thrust condition, for example at a maximum take-off condition (MTO). The TET (which can be designated the maximum TET) in use of the engine can be particularly high, for example, at least (or of the order of) any of the following: 1800 K, 1850 K, 1900 K, 1950 K, 2000 K, 2050 K or 2100 K. The maximum TET can be an included range delimited by any two of the values in the preceding sentence (i.e. the values can form upper or lower limits ). It will be borne in mind that this condition of maximum power to which the maximum TET is measured is identical to the condition such as that to which the maximum net thrust at sea level, or maximum thrust, (to which reference is made n anywhere in this document) is measured. As indicated elsewhere in this document, the present description relates to a gas turbine engine. It can be said that such a gas turbine engine comprises an engine core comprising a turbine, a combustion chamber, a compressor and a heart shaft connecting the turbine to the compressor. Such a gas turbine engine may include a fan (having fan blades) located upstream of the engine core. As indicated elsewhere in this document, the gas turbine engine may include a reduction gear which receives an input from the mandrel shaft and delivers a drive to the blower as output so as to drive the blower at a speed of lower rotation than the heart tree. The input to the reducer can be directly from the heart shaft, or indirectly from the heart shaft, for example via a spindle and / or spur gear. The heart shaft can secure the turbine and the compressor, so that the turbine and the compressor rotate at the same speed (with the blower rotating at a lower speed). The gas turbine engine as described and / or claimed here can have any suitable general architecture. For example, the gas turbine engine may have any desired number of shafts which connect turbines and compressors, for example one, two or three shafts. Strictly by way of example, the turbine connected to the heart shaft which drives the reducer can be a first turbine, the compressor connected to the heart shaft which drives the reducer can be a first compressor, and the shaft of heart that drives the reducer can be a first heart tree. The engine core can further comprise a second turbine, a second compressor, and a second heart shaft connecting the second turbine to the second compressor. The second turbine, the second compressor, and the second heart shaft can be arranged to rotate at a higher speed than the first heart shaft. In such an arrangement, the second compressor can be positioned axially downstream of the first compressor. The second compressor can be arranged to receive (for example receive directly, for example via a generally annular conduit) a flow from the first compressor. The reducer can be arranged to be driven by the heart shaft which is configured to rotate (for example in use) at the lowest speed of rotation (for example the first heart shaft in the example above). For example, the reduction gear can be arranged to be driven only by the heart shaft which is configured to rotate (for example in use) at the lowest rotational speed (for example to be only the first heart shaft , not the second heart tree, in the example above). As a variant, the reduction gear can be arranged to be driven by any or any shaft (s), for example the first and / or second shafts in the example above. The reducer is a reduction box (in that the outlet to the blower is at a lower speed of rotation than the inlet from the heart shaft). Any type of reducer can be used. For example, the reducer can be a "planetary" or "star" reducer, as described in more detail elsewhere in this document. The reduction gear can have any desired reduction ratio (defined as the speed of rotation of the input shaft divided by the speed of rotation of the output shaft), for example greater than 2.5, for example in the range from 3 to 4, for example of the order of or at least 3, 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3 , 8, 3.9, 4.0, 4.1 or 4.2. The gear ratio can be, for example, between any two of the values in the preceding sentence. Strictly by way of example, the reducer can be a "star" reducer having a ratio in the range from 3.1 or 3.2 to 3.8. In some arrangements, the gear ratio may be outside of these ranges. In any gas turbine engine as described and / or claimed here, a combustion chamber can be provided axially downstream of the fan and the compressor (s). For example, the combustion chamber can be directly downstream of (for example at the outlet of) the second compressor, when a second compressor is supplied. As a further example, the flow at the outlet to the combustion chamber can be supplied to the inlet of the second turbine, when a second turbine is supplied. The combustion chamber can be supplied upstream from the turbine (s). The or each compressor (for example the first compressor and the second compressor as described above) can comprise any number of stages, for example of multiple stages. Each stage may include a row of rotor blades and a row of stator vanes, which may be variable stator vanes (in that their angle of incidence may be variable). The row of rotor blades and the row of stator blades can be axially offset from each other. The or each turbine (for example the first turbine and the second turbine as described above) can comprise any number of stages, for example multiple stages. Each stage may include a row of rotor blades and a row of stator vanes. The row of rotor blades and the row of stator blades can be axially offset from each other. Each fan blade can be defined as having a radial reach extending from a root (or a hub) at a radially internal location washed by gases, or 0% reach position, up to one end at a 100% reach position. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip may be less than (or in the order of) any one of: 0.4, 0.39, 0.38 0.37, 0.36, 0.35, 0.34, 0.33, 0.32, 0.31, 0.3, 0.29, 0.28, 0.27, 0.26 or 0.25. The ratio of the radius of the fan blade at the hub to the radius of the fan blade at the tip can be within an included range delimited by any two of the values in the preceding sentence (i.e. the values may form upper or lower limits). These ratios can be commonly called the ratio of the hub to the end. Both the radius at the hub and the radius at the tip can be measured at the leading edge (or axially foremost) portion of the blade. The ratio of the hub to the end refers, of course, to the gas-washed portion of the fan blade, that is, the portion radially outside of any platform. The radius of the fan can be measured between the center line of the engine and the tip of a fan blade at its leading edge. The blower diameter (which can be just twice the blower radius) can be greater than (or in the order of) any one of: 225 cm, 250 cm (roughly 100 inches), 260 cm , 270 cm (approximately 105 inches), 280 cm (approximately 110 inches), 290 cm (approximately 115 inches), 300 cm (approximately 120 inches), 310 cm, 320 cm (approximately 125 inches), 330 cm (approximately 130 inches), 340 cm (approximately 135 inches), 350 cm, 360 cm (approximately 140 inches), 370 cm (approximately 145 inches), 380 ( about 150 inches) cm, 390 cm (about 155 inches) or 400 cm. The fan diameter can be within an included range delimited by any two of the values in the preceding sentence (i.e., the values can form upper or lower limits). The speed of rotation of the fan may vary during use. Generally, the speed of rotation is lower for blowers with a larger diameter. Strictly by way of nonlimiting example, the speed of rotation of the blower at cruising conditions can be less than 2500 rpm, for example less than 2300 rpm. Strictly as an additional non-limiting example, the speed of rotation of the blower at cruising conditions for an engine having a blower diameter in the range from 250 cm to 300 cm (for example 250 cm to 280 cm) can be in the range from 1700 rpm to 2500 rpm, for example in the range from 1800 rpm to 2300 rpm, for example in the range from 1900 rpm to 2100 rpm. Strictly as an additional non-limiting example, the speed of rotation of the blower at cruising conditions for an engine having a blower diameter in the range from 320 cm to 380 cm can be in the range from 1200 rpm at 2000 rpm, for example in the range from 1300 rpm to 1800 rpm, for example in the range from 1400 rpm to 1600 rpm. In use of the gas turbine engine, the fan (with the associated fan blades) rotates about an axis of rotation. This rotation results in a displacement of the end of the fan blade with a speed U t i P. The work done by the fan blades on the flow results in an increase in enthalpy dH of the flow. A blower end load can be defined by dH / U ti p 2 , where dH is the increase in enthalpy (for example the average enthalpy increase 1-D) through the blower and U tip is the speed (transition) of the blower tip, for example at the leading edge of the blower (which can be defined as the blower tip radius at the leading edge multiplied by the angular speed). The blower end load at cruising conditions can be greater than (or in the order of) any one of: 0.28, 0.29, 0.3, 0.31, 0.32, 0, 33, 0.34, 0.35, 0.36, 0.37, 0.38, 0.39 or 0.4 (all units in this paragraph being Jkg 'K' / (ms *) 2 ). Blower tip loading can be in an included range delimited by any two of the values in the previous sentence (i.e., the values can form upper or lower limits). Gas turbine engines in accordance with the present description can have any desired bypass ratio, where the bypass ratio is defined as the ratio of the mass flow rate of the flow through the bypass duct to the mass flow rate of the flow through the heart at cruising conditions. In some arrangements the bypass ratio may be greater than (or in the order of) any of the following: 10, 10.5, 11, 11.5, 12, 12.5, 13, 13.5, 14, 14.5, 15, 15.5, 16, 16.5, or 17. The bypass ratio can be in an included range delimited by any two of the values in the preceding sentence (i.e. values may form upper or lower limits). The bypass duct can be substantially annular. The bypass duct can be radially outside the central engine. The radially outer surface of the bypass duct can be defined by a nacelle and / or a fan casing. The overall pressure ratio of a gas turbine engine as described and / or claimed here can be defined as the ratio of the stagnation pressure upstream of the blower to the stagnation pressure at the outlet of the compressor higher pressure (before entering the combustion chamber). By way of nonlimiting example, the overall pressure ratio of a gas turbine engine as described and / or claimed here while cruising can be greater than (or of the order of) any of the following: 35, 40, 45, 50, 55, 60, 65, 70, 75. The overall pressure ratio can be within an included range delimited by any two of the values in the preceding sentence (ie the values may form upper or lower limits). The specific thrust of an engine can be defined as the net thrust of the engine divided by the total mass flow through the engine. Under cruising conditions, the specific thrust of an engine described and / or claimed here may be less than (or of the order of) any of the following: 110 Nkg 's, 105 Nkg' s, 100 Nkg- * s, 95 Nkg 's, 90 Nkg' s, 85 Nkg 's or 80 Nkg' s. The specific thrust can be within an included range delimited by any two of the values in the previous sentence (i.e., the values can form upper or lower limits). Such engines can be particularly efficient compared to conventional gas turbine engines. A gas turbine engine as described and / or claimed here can have any desired maximum thrust. Strictly by way of nonlimiting example, a gas turbine as described and / or claimed here may be capable of producing a maximum thrust of at least (or of the order of) any of the following: 160 kN , 170 kN, 180 kN, 190 kN, 200 kN, 250 kN, 300 kN, 350 kN, 400 kN, 450 kN, 500 kN or 550 kN. The maximum thrust can be within an included range delimited by any two of the values in the previous sentence (i.e., the values can form upper or lower limits). The thrust referred to above may be the maximum net thrust under typical atmospheric conditions at sea level plus 15 deg C (ambient pressure 101.3 kPa, temperature 30 deg C), with the static engine. A part of the fan blade and / or of the aerodynamic profile of a fan blade described and / or claimed here can be manufactured from any suitable material or combination of materials. For example at least part of the fan blade and / or of the airfoil can be manufactured at least in part from a composite, for example a metal matrix composite and / or an organic matrix composite, such as carbon fiber. By way of additional example at least a part of the fan blade and / or of the airfoil can be manufactured at least in part from a metal, such as a metal based on titanium or a material based aluminum (such as an aluminum-lithium alloy) or a steel-based material. The fan blade can include at least two regions made using different materials. For example, the fan blade may have a protective leading edge, which can be fabricated using a material that is more able to withstand an impact (for example, by birds, ice, or other material) than the rest of the blade. Such a leading edge can, for example, be manufactured using titanium or a titanium-based alloy. Thus, strictly by way of example, the fan blade can have a carbon fiber or aluminum-based body (such as an aluminum-lithium alloy) with a titanium leading edge. A fan as described and / or claimed here may include a central part, from which the fan blades may extend, for example in a radial direction. The fan blades can be connected to the central part in any desired way. For example, each fan blade may include a fastener which can engage with a corresponding notch in the hub (or disc). Strictly by way of example, such a fastener may be in the form of a dovetail which can snap into and / or engage with a corresponding notch in the hub / disc in order to secure the blade. blower to hub / disc. As a further example, the fan blades can be integrally formed with a central part. Such an arrangement can be designated a bladed disc or a bladed crown. Any suitable process can be used to make such a blading disc or such a blading ring. For example, at least part of the fan blades can be machined from a block and / or at least part of the fan blades can be connected to the hub / disc by welding, such as linear friction welding. The gas turbine engines described and / or claimed here may or may not be provided with a variable section nozzle (VAN). Such a variable section nozzle can make it possible to vary the outlet area of the bypass duct during use. The general principles of the present description can apply to engines with or without NPV. The fan of a gas turbine as described and / or claimed here can have any desired number of fan blades, for example 14, 16, 18, 20, 22, 24, or 26 blades. blower. As they are used here, the cruising conditions have the classic meaning and would be easily understood by the specialist. Thus, for a given gas turbine engine for an aircraft, the specialist would immediately recognize that cruising conditions mean the point of operation of the engine at mid-cruise for a given mission (which can be designated in the industry as "Economic mission") of an aircraft to which the gas turbine engine is designed to be attached. In this sense, mid-cruise is the point in an aircraft flight cycle at which 50% of the total fuel that is burned between the end of the climb and the start of the descent has been burned (which can be approximated by the midpoint - in terms of time and / or distance - between the end of the climb and the start of the descent, cruising conditions thus define an operating point of the gas turbine engine which provides a thrust which ensure steady-state operation (i.e. maintaining a constant altitude and a constant Mach number) at mid-cruise of an aircraft to which it is designed to be attached, taking into account the number of engines supplied on this aircraft, for example when an engine is designed to be attached to an aircraft which has two engines of the same type, at cruising conditions the engine provides half of the total thrust that would be required for operation in steady state of this aircraft at mid-cruise. In other words, for a given gas turbine engine for an aircraft, the cruising conditions are defined as the engine operating point which provides a specified thrust (required to provide - in combination with n ' any other engine on the aircraft - steady-state operation of the aircraft to which it is designed to be fixed at a given mid-cruise Mach number) at mid-cruise weather conditions (defined by the standard atmosphere according to ISO 2533 at mid-cruise altitude). For any given gas turbine engine for an aircraft, the mid-cruise thrust, atmospheric conditions and Mach number are known, and therefore the engine's point of operation at cruising conditions is clearly defined. Strictly by way of example, the forward speed at cruising condition can be any point in the range from Mach 0.7 to 0.9, for example 0.75 to 0.85, for example example 0.76 to 0.84, for example 0.77 to 0.83, for example 0.78 to 0.82, for example 0.79 to 0.81, for example of the order of Mach 0.8 , of the order of Mach 0.85 or in the range of 0.8 to 0.85. Any single speed within these ranges may be part of the cruising condition. For a certain aircraft, the cruising conditions may be outside these ranges, for example below Mach 0.7 or above Mach 0.9. Strictly by way of example, the cruising conditions can correspond to standard atmospheric conditions (according to the international standard atmosphere, ISA) at an altitude which is in the range going from 10,000 m to 15,000 m, for example in the range from 10,000 m to 12,000 m, for example in the range from 10,400 m to 11,600 m (roughly 38,000 feet), for example in the range from 10,500 m to 11,500 m, for example in the range from 10,600 m to 11,400 m, for example in the range from 10,700 m (approximately 35,000 feet) to 11,300 m, for example in the range from 10,800 m at 11,200 m, for example in the range from 10,900 m to 11,100 m, for example of the order of 11,000 m. Cruise conditions can correspond to typical atmospheric conditions at any given altitude within these ranges. Strictly by way of example, the cruising conditions may correspond to an engine operating point which provides a known required level of thrust (for example a value in the range from 30 kN to 35 kN) to a number Mach forward of 0.8 and typical atmospheric conditions (depending on the international standard atmosphere) at an altitude of 38,000 feet (11,582 m). Strictly as an additional example, the cruising conditions can correspond to an engine operating point which provides a known required level of thrust (for example a value in the range from 50 kN to 65 kN) to a Mach number ahead of 0.85 and typical atmospheric conditions (depending on the international standard atmosphere) at an altitude of 35,000 feet (10,668 m). [0181] In use, a gas turbine engine described and / or claimed here can operate under cruising conditions defined elsewhere in this document. Such cruising conditions can be determined by the cruising conditions (e.g. mid-cruise conditions) of an aircraft to which at least one (e.g. 2 or 4) gas turbine engine can be mounted in order to provide a propulsion thrust. In one aspect, an aircraft is provided comprising a gas turbine engine as described and / or claimed here. The aircraft according to this aspect is the aircraft for which the gas turbine engine was designed to be fixed. In one aspect, there is provided a method of operating a gas turbine engine as described and / or claimed here. In one aspect, there is provided a method of operating an aircraft comprising a gas turbine engine as described and / or claimed here. Embodiments will now be described by way of example only, with reference to the Figures, in which: [Fig.l] is a side sectional view of a gas turbine engine; [Fig. 2] is a side view in close section of an upstream part of a gas turbine engine; [Fig. 3] is a partially cutaway view of a reduction gear for a gas turbine engine; [Fig. 4] is a schematic view showing an enlarged view of an upstream part of the turbine of the gas turbine engine. FIG. 1 illustrates a gas turbine engine 10 having a main axis of rotation 9. The engine 10 comprises an air intake 12 and a propulsion blower 23 which generates two air flows: a core air flow A and a bypass air flow B. The gas turbine engine 10 comprises a core 11 which receives the flow of air from core A. The engine core 11 comprises, in series of axial flow, a low pressure compressor 14 (which can be designated here first compressor 14), a high pressure compressor 15 (which here can be designated second compressor), combustion equipment 16, a high pressure turbine 17 (which can be designated here second turbine), a low pressure turbine 19 (which can be designated here first turbine) and an exhaust nozzle of heart 20. A nacelle 21 surrounds the gas turbine engine 10 and defines a bypass duct 22 and a bypass exhaust nozzle 18. The flow of bypass air B flows through the bypass duct 22. The blower 23 is attached to and driven by the low pressure turbine 19 via a shaft 26 and a planetary reduction gear 30. In use, the core air flow A is accelerated and compressed by the low pressure compressor 14 and directed into the high pressure compressor 15 where additional compression takes place. The compressed air discharged from the high pressure compressor 15 is directed into the combustion equipment 16 where it is mixed with fuel and the mixture is burned. The resulting hot combustion products then expand, and thereby drive the high pressure and low pressure turbines 17, 19 before being evacuated through the nozzle 20 to provide a certain propulsion thrust. The high pressure turbine 17 drives the high pressure compressor 15 through a suitable interconnection shaft 27. The blower 23 generally provides the majority of the propulsion thrust. The planetary reducer 30 is a reduction box. An exemplary arrangement for a gas blower gas turbine engine 10 is shown in Ligure 2. The low pressure turbine 19 (see Ligure 1) drives the shaft 26, which is coupled to a planetary wheel, or planetary gear, 28 of the planetary gear arrangement 30. Radially outward from the planetary gear 28 and meshing therewith, there are a plurality of planet gears 32 which are coupled together by a planet carrier 34. The planet carrier 34 forces the satellite gears 32 to change orientation around the planetary gear 28 in synchronism while allowing each satellite gear 32 to rotate about its own axis. The planet carrier 34 is coupled via links 36 to the blower 23 in order to cause it to rotate about the motor axis 9. Radially outward and meshing with the satellite gears 32 , there is a ring or gear 38 which is coupled, via links 40, to a stationary support structure 24. It should be noted that the terms “low pressure turbine” and “low pressure compressor” as they are used here can be taken to indicate the lower pressure turbine stages and the lower pressure compressor stages (i.e. not including the blower 23) respectively and / or the turbine and compressor stages which are connected together by the interconnection shaft 26 with the lowest speed of rotation in the motor (i.e. not including the gearbox output shaft which drives the blower 23). In some literature, the "low pressure turbine" and the "low pressure compressor" referred to here may alternatively be known as "intermediate pressure turbine" and "intermediate pressure compressor". When such an alternative nomenclature is used, the blower 23 can be designated first compression stage or lower pressure compression stage. The epicyclic reducer 30 is shown by way of example in more detail in Ligure 3. Each of the planetary gear 28, the satellite gears 32 and the ring gear 38 includes teeth around its periphery to s' mesh with the other gears. However, for clarity only exemplary portions of the teeth are illustrated in Ligure 3. There are four planet gears 32 illustrated, although it will be apparent to the specialist reader that more or less planet gears 32 can be supplied within the scope of the claimed invention. Practical applications of a planetary planetary gearbox 30 generally include at least three planet gears 32. The epicyclic reduction gear 30 illustrated by way of example in Liguria 2 and 3 is of the planetary type, in that the planet carrier s 34 is coupled to an output shaft via links 36, with the fixed gear 38. However, any other suitable type of epicyclic reducer 30 can be used. As a further example, the planetary reduction gear 30 may be a star arrangement, in which the planet carrier 34 is kept fixed, with the toothed crown (or ring) 38 allowed to rotate. In such an arrangement, the fan 23 is driven by the ring gear 38. As another alternative example, the reduction gear 30 can be a differential reduction gear in which the gear ring 38 and the planet carrier 34 are one and the other allowed to shoot. It will be borne in mind that the arrangement shown in Figures 2 and 3 is by way of example only, and that various alternatives are within the scope of this description. Strictly by way of example, any suitable arrangement can be used to position the reduction gear 30 in the motor 10 and / or to connect the reduction gear 30 to the motor 10. As a further example, the connections (such as the connections 36, 40 on the example of Ligure 2) between the reduction gear 30 and other parts of the motor 10 (such as the input shaft 26, the output shaft and the fixed structure 24) may have n any desired degree of stiffness or flexibility. As an additional example, any suitable arrangement of bearings between rotating and stationary parts of the motor (e.g. between input and output shafts from the gearbox and fixed structures, such as the gearbox housing) may be used, and the description is not limited to the exemplary arrangement of Figure 2. For example, when the reducer 30 has a star arrangement (described above), the specialist would readily understand that the arrangement of output and support links and bearing locations would typically be different from that shown by way of example in Figure 2. Thus, the present description extends to a gas turbine engine having any arrangement of styles of reducer (for example star or planetary), support structures, arrangement of shafts entry and exit, and landing locations. Optionally, the reducer can cause additional and / or alternative components (for example the intermediate pressure compressor and / or a booster). Other gas turbine engines to which the present description can be applied may have alternative configurations. For example, such motors can have another number of compressors and / or turbines and / or another number of interconnecting shafts. As a further example, the gas turbine engine shown in Figure 1 has a split flow nozzle 18, 20 which means that the flow through the bypass 22 has its own nozzle 18 which is independent of and radially outside the main engine nozzle 20. However, this is not limiting, and any aspect of the present description can also be applied to engines in which the flow through the bypass duct 22 and the flow through the heart 11 are mixed, or combined, before (or upstream of) a single nozzle, which can be called mixed flow nozzle. Either and / or the other of the nozzles (whether mixed or divided flow) can have a fixed or variable area. While the example described relates to a turbofan engine, the description can apply, for example, to any type of gas turbine engine, such as an open rotor (in which the stage fan is not surrounded by a nacelle) or a turboprop, for example. The geometry of the gas turbine engine 10, and of the components thereof, is defined by a conventional system of axes, comprising an axial direction (which is aligned on the axis of rotation 9), a direction radial (in the bottom-up direction in Figure 1), and a circumferential direction (perpendicular to the page in the view of Figure 1). The axial, radial and circumferential directions are mutually perpendicular. Figure 4 shows a part of the turbine in more detail. In particular, Figure 4 shows a downstream part of the combustion chamber 16, the second turbine 17 (high pressure), and an upstream part of the first turbine 19 (low pressure). The high pressure turbine 17 is connected to the second heart shaft 27. The low pressure turbine 19 is connected to the first heart shaft 26. In the example illustrated, the high pressure turbine 17 comprises, in series of axial flow, a first row of stator blades 171 (the most axially upstream), a first row of rotor blades 172 (the most axially upstream), a second row of stator vanes 173 (the second most axially upstream) and a second row of rotor blades 174 (the second most axially upstream). The first row of rotor blades 172 is connected to a rotor disc 177. The second row of rotor blades 174 is connected to a rotor disc 178. The two rotor discs 177, 178 are secured one to the other by a connecting element 179. At least one of the rotor discs (in the example illustrated the first rotor disc 177) is connected to the second heart shaft 27 via an arm 271 Thus, in use, the second heart shaft 27, the rotor discs 177, 178 and the rotor blades 172, 174 all rotate together, at the same speed of rotation. The gas turbine engine 10 also includes sealing rings 175 provided radially outside the first row of rotor blades 172. The gas turbine engine 10 also includes sealing rings 176 provided radially outside the second row of rotor blades 174. The sealing segments 175, 176 form the radially outer flow boundary (which may be referred to as a radially outer annular space line) in the region of the row of respective rotor blades 172, 174, for example over the axial extent of the ends of the rotor blades 172, 174. The sealing rings 175, 176 may form a seal with the ends of the rotor blades to prevent - or at least limit - a flow passing over or beyond the tips of the rotor blades. The sealing segments 175, 176 may be abradable by the rotor blades. Thus, for example, the sealing segments 175, 176 can be abraded by the rotor blades in use so as to form an optimal seal between them. Each segment can form an annular segment or a frustoconical segment. In the example illustrated, the high-pressure turbine 17 is a two-stage high-pressure turbine, in that it comprises two stages of blades and blades, each stage comprising a row of stator blades followed by a row of rotor blades. However, it should be borne in mind that gas turbine engines 10 according to the present description can comprise a high pressure turbine with any number of stages, for example 1, 2, 3, 4, 5 or more of 5 stages of stator vanes and rotor blades. The low pressure turbine 19 is provided downstream of the high pressure turbine 17. A row most axially upstream of stator vanes 191 in the low pressure turbine 19 is supplied immediately downstream of the final row of blades. rotor 174 of the high pressure turbine 17. A row most axially upstream of rotor blades 192 in the low pressure turbine 19 is provided immediately downstream of the row most axially upstream of stator blades 191. Row 1a more axially upstream of rotor blades 192 is connected to the first heart shaft 26 via a rotor disc. In use, the rotor blades 192 of the low pressure turbine 19 drive the first heart shaft 26, which in turn drives the low pressure compressor 14, and also drives - via a reducer 30 - the blower 23. Ligure 4 shows only an upstream part of the low pressure turbine 19. However, it will be borne in mind that downstream of the illustrated part we may have provided other rows of stator blades and blades rotor. For example, the low-pressure turbine 19 can comprise 1, 2, 3, 4, 5 or more than 5 stages of stator vanes and rotor blades. The most axially upstream row of rotor blades 192 is connected to one or more (not shown) rows of rotor blades downstream via a link 199 which is connected to the disc 197 on which the rotor blades 192 are supported. At least part of the high pressure turbine 17 and / or the low pressure turbine 19 comprises a CMC in the example illustrated. Strictly by way of example, the CMC material may be silicon carbide fibers and / or a matrix of silicon carbide (SiC-SiC), although it will be appreciated that other CMCs may be used, such as an oxide-oxide (CMC Ox-Ox material), a monolithic ceramic, and / or the like. As indicated elsewhere in this document, CMCs have different properties from conventional turbine materials, such as nickel alloys. For example, CMCs typically have a lower density and are able to withstand higher temperatures than metals such as nickel alloys. The present inventors have understood that these properties may be useful in certain areas of the turbine 17, 19, but other properties - such as the lower thermal conductivity of CMCs compared to nickel alloys - mean that their use does not is not suitable in all areas of the turbine 17, 19. For example, depending on the type of engine (for example in terms of architecture and / or maximum thrust), any one or more of the first row of stator blades 171 (most axially in upstream), the first row of rotor blades 172 (the most axially upstream), the second row of stator blades 173 (the second most axially upstream), the second row of rotor blades 174 (the second the more axially upstream) and the first or second set of sealing segments 175, 176 of the high pressure turbine can be manufactured using CMCs. Components in the above list that are not made using CMCs can be made using a metal, such as a nickel alloy. Optionally, in any aspect or arrangement described and / or claimed herein and regardless of the number of stages in the high pressure turbine 17, the rotor blades of each stage in the high pressure turbine 17 may be surrounded by segments d sealing, and the sealing segments surrounding any one or more stages (e.g. all stages) can be made from CMC. Strictly by way of nonlimiting example, in the arrangement of Ligure 4, the second row of stator blades 173, the second row of rotor blades 174 and the first set of sealing segments 175 and the second set of sealing segments 176 of the high pressure turbine are manufactured using CMCs, while the first row of stator blades 171 and the first row of rotor blades 172 are manufactured using a nickel alloy. In this particular example, the temperature encountered by the first row of stator blades 171 and the first row of rotor blades 172 may even be higher than that which can be tolerated by CMCs. Thus, for this particular example, this means that the first row of stator blades 171 and the first row of rotor blades 172 - which are subjected to higher temperatures than the downstream components due to their proximity to the chamber outlet 16 - can benefit from the relatively high thermal conductivity of the nickel alloy so that they are cooled more efficiently by using cooling air (taken from the compressor, for example) which can be supplied to passages extending through the components. The total mass of the high pressure turbine 17 can include the masses of the stator vanes 171, 173, the rotor blades 172, 174, sealing rings 175, 176, rotor discs 177, 178, d one or more radially internal envelope elements which form the internal flow limit 220 over the axial extent of the high pressure turbine 17, and one or more radially external envelope elements which form the external flow limit 230 on the axial extent of the high pressure turbine 17. CMCs can be used in suitable parts of the low pressure turbine 19, although in some engines 10 their use in the low pressure turbine 19 may not be appropriate, and thus they cannot be used. Strictly by way of nonlimiting example, in the arrangement of Ligure 4, the most axially upstream row of stator blades 191 is manufactured using a CMC, while the most axially upstream row of blades rotor 192 is manufactured using a metal alloy (such as a nickel alloy). In this particular example, the temperature encountered by the most axially upstream row of rotor blades 192 may not be high enough to benefit from the use of CMC, although it should be borne in mind that in other motors 10 according to the present description, the most axially upstream row of rotor blades 192 and / or the associated sealing rings 193 can be fabricated using CMCs. Indeed, in certain engines, components (such as blades, blades and seals) downstream of the row most axially upstream of rotor blades 192 in the low pressure turbine 19 can be manufactured using CMCs. Any component manufactured using CMCs can also be provided with an environmental barrier coating (EBC). Such an EBC can cover at least the gas-washed surface of such components. Such an EBC can protect the CMC from environmental degradation, for example degradation due to the effects of water vapor. Such an EBC can be, for example ytterbium disilicate (Yb 2 Si 2 O 7 ), which can be applied by any suitable method, such as air plasma spraying. As indicated elsewhere in this document, CMCs have a higher temperature resistance than conventional materials, such as metal alloys. This means that selective use of CMC in the turbine may mean that certain components which should be cooled if they were made from a metal alloy do not necessarily have to be cooled because they are made from CMC and / or some components made using a CMC require less cooling than if they were made from a metal alloy. Additionally or alternatively, by the use of CMC it may be possible to expose certain components to a higher temperature than would otherwise be possible. Strictly by way of nonlimiting example, an optimization of the reuse of CMC in the engine (for example in one or more components of the turbine 17, 19 as described here) can reduce the requirement for cooling flow C , which can result in a more efficient engine core (because there is less flow bypassing the combustion chamber), which means that for a given amount of core power, the mass flow entering the core can be reduced and / or the size and / or mass of the turbine (s) 17, 19 can be reduced. Figures 1 and 4 schematically show a turbine cooling device 50. The turbine cooling device extracts the cooling flow C from the compressor 14, 15. The cooling flow C bypasses the combustion chamber 16. The cooling flow C is then distributed to the high pressure turbine 17 and possibly to the low pressure turbine 19. Although the turbine cooling apparatus 50 is shown in Figures 1 and 4 as extracting the cooling flow C from from a specific position in the high pressure compressor 15 and distributing it to a specific position in the high pressure turbine 17, it will be borne in mind that this is only for ease of schematic representation, and that the cooling flow C can be extracted from any suitable locations (e.g. multiple locations in the high pressure compressor 15 and / or the low pressure compressor sion 14) and distributed to any desired location (for example multiple locations in the high pressure turbine 17 and / or the low pressure turbine 19). A reduction in the amount of cooling flow C is desirable, because the cooling flow is not burned and thus the amount of work that can be extracted from it is lower than for the flow that passes through the combustion chamber 16. With reference to Figure 1, the gas turbine engine 10 has a bypass ratio defined as the mass flow of the flow B through the bypass duct 22 divided by the mass flow of the flow A penetrating the engine core at cruising conditions. As the bypass ratio is increased - for example to increase the efficiency of the engine - proportionally less flow A crosses the heart. This means that for a given engine size and / or to be able to withstand a given turbine inlet temperature, a higher proportion of the core flow A may have to be used as the turbine cooling flow C. In this sense , as used here, the turbine inlet temperature (TQturb_in) can be the maximum stagnation temperature measured at a position 60 in the gas flow path which is immediately upstream of the row of blades. the most axially upstream rotor 172, that is to say what is called an operational state of "red line" of the engine to which the engine is certified. A bypass cooling efficiency ratio can be defined as the ratio of the mass flow C of the turbine cooling flow to the mass flow B of the bypass flow at cruising conditions. By using the knowledge of the constraints and / or technologies described by way of example here, the efficiency ratio of bypass cooling can be optimized so that it is as described and / or claimed here. In addition or as a variant, the mass of the high pressure turbine 17 and / or of the low pressure turbine 19 can be optimized (for example reduced) compared to a conventional engine. In turn, this can reduce the mass of the high pressure turbine 17 and / or the low pressure turbine 19 as a proportion of the overall mass of the gas turbine engine 10. By using a knowledge of the constraints and / or technologies described by way of example here, the normalized thrust can be optimized. In this sense, the normalized thrust is defined as the maximum net thrust of the engine 10 at sea level divided by the total mass of the turbines 17,19 in the engine 10. The example illustrated has a high pressure turbine 17 and a turbine low pressure 19, however, it should be borne in mind that when other turbines are included in the engine the total turbine mass includes the mass of all the turbines. As indicated elsewhere in this document, the optimized use of CMC can result in a reduced requirement in terms of turbine cooling flow. Additionally or alternatively, by the use of CMC it may be possible to expose certain components to a higher temperature than would otherwise be possible. This can result in the ability to increase the turbine inlet temperature compared to motors 10 which do not include optimized use of CMC. In this sense, it has been found that higher turbine inlet temperatures are desirable from an engine efficiency point of view. Using knowledge of the constraints and / or technologies described by way of example here, the cooling efficiency ratio can be optimized. In this sense, the cooling efficiency ratio is defined as the ratio between the turbine inlet temperature (as defined elsewhere in this document) and the cooling flow requirement. The cooling flow requirement can be defined as the mass flow of the turbine cooling flow C divided by the mass flow of the flow A entering the engine core at cruising conditions. [0223] A core size CS can be defined for the gas turbine engine 10 as [Math 5] [0224] JTQcomp_out CS = Wcomp in .——------- P0comp_out [0225] where: Wcomp_in is the mass flow (kg / s) at the inlet of the motor core, that is to say the mass flow of the core flow A measured at position 70 in FIG. 1; T0comp_out is the stagnation temperature (K) at the outlet to the compressor, that is to say at the outlet of the higher pressure compressor 15, indicated by position 80 in Figure 1; P0comp_out is the stagnation pressure (Pa) at the outlet to the compressor, that is to say at the outlet of the higher pressure compressor 15, indicated by position 80 in Figure 1. The use of a knowledge of the constraints and / or technologies described by way of example here can allow an efficiency ratio of the thrust at the core TC and / or a efficiency ratio of the fan at HR heart to be optimized in order to be within the ranges described and / or claimed here, where the efficiency ratio of the thrust at the heart TC and the efficiency ratio of the fan at the heart heart are as defined above below (with TQturb_in being the turbine inlet temperature at position 60 shown in Figure 4, as described above). [0230] [Math.6] TC = (Maximum net thrust at sea level). ^^ - ^ b ~ in . [0231] [Math.7] FC = (Blower diameter). ^ TOt ^ b - in _ [0232] It will be appreciated that the knowledge and / or technology described and / or claimed herein results in a particularly efficient gas turbine engine 10. For example, the knowledge and / or technology described and / or claimed herein can provide a particularly efficient gas turbine engine 10 in which a blower 23 which is driven by a reducer 30 is supplemented by an optimized engine core. It will be understood that the invention is not limited to the embodiments described above and that various modifications and improvements can be made without departing from the concepts described here. Except in the case of mutual exclusivity, any of the characteristics and aspects may be used separately or in combination with any other characteristics and the description extends to and includes all combinations and sub-combinations of one or more several features described here.
权利要求:
Claims (2) [1] claims [Claim 1] Gas turbine engine (10) for an aircraft comprising: an engine core (11) comprising: a first turbine (19), a first compressor (14), and a first heart shaft (26) connecting the first turbine to the first compressor; a second turbine (17), a second compressor (15), and a second heart shaft (27) connecting the second turbine to the second compressor, the second turbine, the second compressor, and the second heart shaft being arranged to rotate a higher rotational speed than the first heart shaft, the gas turbine engine further comprising: a blower (23) comprising a plurality of blower blades; and a reduction gear (30) which receives an input from the first heart shaft (26) and outputs a drive to the blower so as to drive the blower at a lower speed of rotation than the first heart shaft, in which : a turbine inlet temperature (T0 turb _i n ) is defined as the temperature (K) at the inlet to the turbine rotor most axially upstream in the gas turbine engine at a power condition gas turbine engine maximum; a core size is defined as [Math 8] __ ... jT0comp_out CS = Wcompin .--------- P0comp_out where: Wcomp_in is the mass flow (kg / s) at the inlet of the motor core ; T0comp_out is the stagnation temperature at the outlet to the compressor; P0comp_out is the stagnation pressure at the outlet to the compressor; and an efficiency ratio of the heart blower FC is in the range from 1.9 x 10 5 mkg * sPa to 3.5 x 10 mkg * sPa, where the efficiency ratio of the heart blower is defined like [Math 9] FC = {fan diameter). ^ TOt ^ 7b - in [Claim 2] The gas turbine engine of claim 1, wherein the efficiency ratio of the core blower FC is in the range of 1.9 x 10 5 mkg * sPa to 3 x 10 5 mkg * sPa, optionally in the range from 1.9 x 10 5 mkg * sPa to 2.5 x 10 5 mkg 'sPa. [Claim 3] A gas turbine engine according to claim 1 or claim 2, wherein an efficiency ratio of the TC core thrust is at least 1.5 x 10 7 kNkg * sPa, optionally in the range of 1, 5 x 10 7 kNkg * sPa to 3.5 kNkg * sPa, possibly 1.5 x 10 7 kNkg * sPa to 3 kNkg * sPa, possibly in the range from 2 x 10 7 kNkg * sPa to 3 kNkg * sPa, where the efficiency ratio of the thrust to the heart is defined as [Math 10] TC = (maximum net thrust at sea level). ^ TOt ^ b - m [Claim 4] Gas turbine engine according to any one of the preceding claims, in which:the second turbine comprises at least one composite component with a ceramic matrix. [Claim 5] The gas turbine engine of claim 4, wherein the mass of ceramic matrix composite in the second turbine is in the range of 2% to 15% of the total mass of the second turbine, and optionally in the range of 4% to 10% of the total mass of the second turbine. [Claim 6] A gas turbine engine (10) for an aircraft according to claim 4 or claim 5, wherein:the first turbine comprises at least one composite component with a ceramic matrix; and eventually,the mass of ceramic matrix composite in the first and second turbines is in the range from 1% to 15%, possibly 2% to 12%, of the total mass of the first and second turbines. [Claim 7] Gas turbine engine (10) for an aircraft according to any one of the preceding claims, in which:the turbine comprises at least one row of stator blades (171); and the most axially upstream row of stator vanes (171) is metallic or a ceramic matrix composite. [Claim 8] Gas turbine engine (10) for an aircraft according to any one of the preceding claims, in which:the turbine comprises at least one row of rotor blades (172); and the most axially upstream row of rotor blades (172) is metallic or a ceramic matrix composite. [Claim 9] Gas turbine engine (10) according to any one of the preceding claims, in which: the turbine comprises at least one row of rotor blades (172), the most axially upstream row of rotor blades being surrounded radially by sealing segments (175); andthe sealing segments comprise a ceramic matrix composite. [Claim 10] Gas turbine engine (10) according to any one of the preceding claims, in which:the turbine comprises at least two rows of stator blades (171, 173); andthe second most axially upstream row of stator vanes (173) comprises a ceramic matrix composite. [Claim 11] Gas turbine engine (10) for an aircraft according to any one of the preceding claims, in which:the turbine comprises at least two rows of rotor blades (174); and the second most axially upstream row of rotor blades (174) comprises a ceramic matrix composite. [Claim 12] A gas turbine engine (10) for an aircraft according to claim 11, wherein:the second most axially upstream row of rotor blades is radially surrounded by sealing rings made of ceramic matrix composite. [Claim 13] The gas turbine engine of any preceding claim, wherein the most axially upstream row of stator vanes (191) in the first turbine comprises a ceramic matrix composite. [Claim 14] The gas turbine engine of any preceding claim, wherein the most axially upstream row of rotor blades (192) in the first turbine comprises a ceramic matrix composite, the gas turbine engine further comprising optionally, ceramic matrix composite sealing rings surrounding the most axially upstream row of rotor blades (192) in the first turbine. [Claim 15] Gas turbine engine according to any one of the preceding claims, in which:the turbine inlet temperature, defined as the temperature at the inlet to the most axially upstream turbine rotor at a maximum power condition of the gas turbine engine, is in the range from 1800 K to 2100 K, possibly at least 1850 K, 1900 K, 1950 K or 2000 K; and / or the maximum net thrust at sea level is in the range from 160 kN to 550 kN, possibly in the range from 160 kN to 250 kN or 300 kN to 500 kN; and / or the reduction ratio of the reduction gear is in the range from [2] 3.3 to 4; and / or the fan diameter is in the range from 225 cm to 400 cm, optionally in the range from 250 cm to 280 cm or 325 to 370 cm.
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同族专利:
公开号 | 公开日 US20200049104A1|2020-02-13| DE102019120621A1|2020-02-13| CN211819655U|2020-10-30| GB201813087D0|2018-09-26|
引用文献:
公开号 | 申请日 | 公开日 | 申请人 | 专利标题 GB2581964A|2019-03-04|2020-09-09|Rolls Royce Plc|A turbomachine for a gas turbine engine| GB201908978D0|2019-06-24|2019-08-07|Rolls Royce Plc|Gas turbine engine transfer efficiency| GB201908972D0|2019-06-24|2019-08-07|Rolls Royce Plc|Compression in a gas turbine engine|
法律状态:
2020-07-28| PLFP| Fee payment|Year of fee payment: 2 | 2021-07-26| PLFP| Fee payment|Year of fee payment: 3 | 2021-08-27| PLSC| Search report ready|Effective date: 20210827 |
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申请号 | 申请日 | 专利标题 GBGB1813087.2A|GB201813087D0|2018-08-10|2018-08-10|Efficient gas turbine engine| GB1813087.2|2018-08-10| 相关专利
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