• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    The invention relates to a fuel metering circuit (1) for a turbomachine comprising: - a metering device (6), - a pump (4), - a regulation valve (5) configured to return an excess fuel flow delivered at the doser (6) to the pump (4) as a function of a difference in fuel pressure across the metering device (6), - a diaphragm (8) and - a volume flow meter (9), the diaphragm (8) and the volume flowmeter (9) being connected in parallel with the metering device (6), downstream of the regulating valve (5), in order to determine a density of the fuel flowing in the metering circuit (1).
    公开号:FR3069021A1
    申请号:FR1756706
    申请日:2017-07-13
    公开日:2019-01-18
    发明作者:Loic Pora；Arnaud Bernard Clement Thomas Joudareff
    申请人:Safran Aircraft Engines SAS；
    IPC主号:
    专利说明:

    FIELD OF THE INVENTION
    The invention relates to a fuel metering circuit of a turbomachine, and a metering method which can be implemented by such a circuit.
    TECHNOLOGICAL BACKGROUND
    A turbomachine conventionally comprises a fuel metering circuit comprising a fuel metering device, delivering to the combustion chamber of the turbomachine a flow of fuel adapted to the operating regime of the turbomachine.
    The metering circuit also includes (in the case of turbojet engines fitted to airplanes with fuel tanks integrated into the aircraft - vs aircraft architectures equipped with turbomachines other than turbojet engines and having an integrated tank) a pump which takes the fuel from the fuel tank of the turbomachine, to route it to the metering device, as well as a regulating valve which makes it possible to recirculate towards the pump an excess fuel flow rate supplied to the metering device.
    Each operating regime of the turbomachine imposes a corresponding mass flow of fuel which must be delivered by the metering device. With reference to FIG. 1, the density of different types of fuels has been represented (each curve numbered 1 to 4 corresponding to a different fuel, curve numbered 5 corresponds to an example of dimensioning of the engine) as a function of the temperature. It appears from this figure that the density of a fuel can vary significantly, in particular depending on the type of fuel used (more or less volatile fuels) and the temperature of the fuel. Currently, the metering units are controlled from control laws which link a desired target mass flow rate to a position of the metering unit, for fixed conditions of temperature and type of fuel.
    Consequently, these control laws do not make it possible to take account of the variability of the fuel density in the control of the metering device and therefore to precisely adapt the mass flow metered to the density of the fuel to obtain the target mass flow.
    In addition, it is not possible to know precisely the mass flow delivered by the metering device because the flow meters used to know the quantity of fuel delivered by the metering device are volume flow meters, the mass flow meters not having sufficient reactivity to provide a reliable information adapted at all times to the engine speed of the turbomachine.
    This results in a significant imprecision, of the order of 12%, on the mass flow delivered by the metering device to the fuel combustion chamber.
    It is possible to calculate the part of the imprecision in the flow delivered by the metering device, which results from the ignorance of the density of the fuel by the following formula (A) expressing the delivered flow:
    Wf = K. S. J p. AP (A)
    With:
    - Wf the mass flow injected by the metering device in kg / h p the fuel density in kg / L
    - K a constant, and
    - S the opening section of a doser slot in mm 2
    The impact of density on the injected flow is as follows:
    dWf 1 dp
    Wf ~
    A density varying from 700 to 900 kg / m 3 creates an imprecision on the mass flow injected between -6.4 and 6.1%, compared to a law calculated with an average density of 803 kg / m 3 .
    However, this imprecision impacts the dimensioning of the turbomachine.
    In particular, a significant change in the speed of the turbomachine, for example from a high speed speed to an idle speed or vice versa, causes an abrupt variation in the flow rate delivered to the combustion chamber. This variation is effected in less time than the variation of the speed of rotation of the turbomachine. Operating tolerances, called pumping and shutdown margins, must therefore be defined so that the turbomachine continues to operate despite a delivered flow rate different from the just need necessary for operation and adapted to its current rotation speed, these tolerances being obtained by oversizing the turbomachine.
    Due to the large imprecision in the flow rate delivered by the metering device, the tolerances as well as the oversizing of the turbomachine must be even greater.
    Some solutions have been proposed including the use of a temperature sensor, combined with a computer correcting the metering control according to compensation laws established according to the density or the temperature of the fuel.
    However, this solution only corrects part of the temperature differences, by adding other sources of uncertainty related to the drafting of the law.
    SUMMARY OF THE INVENTION
    The purpose of the invention is to overcome the drawbacks of the prior art by proposing a fuel metering system having increased precision on the metered flow rate compared to the prior art.
    For this, the invention proposes a fuel metering circuit for a turbomachine comprising:
    - a dispenser,
    - a pump configured to circulate a fuel flow to the metering device,
    - a regulating valve configured to return an excess flow of fuel delivered to the metering unit towards the pump according to a difference in fuel pressure at the terminals of the metering unit,
    - a diaphragm and
    - a volume flow meter configured to determine the volume flow of fuel passing through the diaphragm.
    The diaphragm and the volume flow meter are mounted in parallel with the metering device in a bypass duct, downstream of the regulating valve, in order to determine a density of the fuel circulating in the metering circuit.
    Some preferred but non-limiting characteristics of the dosing circuit described above are the following, taken individually or in combination:
    - the volume flow meter is mounted upstream or downstream of the diaphragm.
    - The dosing circuit further includes an electronic card configured to receive information from the volume flow meter on the volume flow of fuel and adjust a metering control setpoint taking into account the fuel density thus determined.
    - The pump includes a positive displacement pump.
    According to a second aspect, the invention also proposes a turbomachine comprising such a metering circuit.
    According to a third aspect, the invention proposes a fuel metering method implemented in a fuel metering circuit, characterized in that it comprises the following steps:
    - determine a pressure difference across the doser terminals,
    - measure a fuel volume flow using the volume flow meter,
    - calculate, from the pressure difference, the volume flow and constants related to the diaphragm, the fuel density.
    Some preferred but non-limiting characteristics of the dosing method described above are the following, taken individually or in combination:
    - The method further comprises a step during which the flow meter transmits information on the volume flow of fuel to an electronic card and the electronic card adjusts a metering control setpoint taking into account the fuel density.
    the fuel flow is controlled by recirculating a variable fuel flow to the pump using the regulating valve.
    BRIEF DESCRIPTION OF THE DRAWINGS
    Other characteristics, objects and advantages of the present invention will appear better on reading the detailed description which follows, and with regard to the appended drawings given by way of nonlimiting examples and in which:
    - Figure 1, already described, shows the variation in density of several fuels as a function of temperature.
    - Figure 2 schematically shows a metering circuit according to an embodiment of the invention.
    - Figure 3 is a flowchart illustrating steps of an exemplary embodiment of a metering method according to the invention.
    DETAILED DESCRIPTION OF AN EMBODIMENT
    Referring to Figure 2, there is shown a fuel metering circuit 1 of a turbomachine, comprising at least one combustion chamber 2 and a fuel tank 3.
    The fuel metering circuit 1 comprises a positive displacement pump 4, a metering device 6 and a so-called high-pressure dosing line supplying the dosing pump 4 to the inlet of the dosing device 6. The dosing device 6 is adapted to deliver a target mass flow to the combustion chamber 2 from an initial flow which is delivered to it by the positive displacement pump 4 via the high-pressure line.
    The dispenser 6 comprises a surface, called the opening surface of the dispenser, of variable size, which allows the liquid to flow. The flow delivered by the metering device 6 is therefore in particular a function of the opening surface.
    The opening surface of the metering device 6 is variable on the control of a servovalve, which controls the movement of a movable metering part to gradually obstruct a metering orifice or slot. A position sensor makes it possible to know the position of the moving part. The position sensor is typically an LDVT (linear variable differential transformer) sensor.
    There are different types of dispensers 6, for example with a conventional dosing slot, described in document US Pat. No. 7,526,911, or with an exponential slot, described in documents EP 1,231,368 and FR 2,825,120. exponential slot, the opening surface exponentially increases with the movement of the moving part, which allows better precision at low flow rates.
    The dosing circuit can also include a stop valve 10 or HPSOV (English acronym for High Pressure Shut-off Valve) configured to authorize or block a fuel injection into the combustion chamber.
    Optionally, the metering circuit 1 can include an electronic card 11 for controlling the metering of the fuel. For this, the electronic card can for example communicate with the metering device 6 in both directions: it can send position instructions to the metering device 6 and recover data relating to the metering device.
    The electronic card 11 can also be connected to a control unit, external to the device. The control unit is typically an electronic regulation module ECU (English acronym of engine control unit) of a FADEC (English acronym of of Full Authority Digital Engine Control), that is to say of a regulation system digital full authority which controls the variable geometries (actuators, dosers, etc.) of the aircraft. The control unit may be located within the aircraft perimeter and therefore not be dedicated solely to fuel regulation. Conversely, the electronic card 11 is preferably exclusively dedicated to metering the fuel and to the additional functions. As a variant, it is also possible to have an additional controller, in addition to the main controller which can in particular be exclusively reserved for metering. The connection between the control unit and the electronic card 11 is generally made with a connection harness.
    Only the electronic card 11 of the metering circuit 1 is connected to the aircraft control unit (by means of a single harness), the redistribution then being carried out within the metering circuit 1 by the electronic card 11 The metering circuit 1 therefore comprises a single input, coming from the control unit, destined for the electronic card 11, which declines this input into several outputs, namely in particular the metering device 6.
    The fuel metering circuit 1 further comprises a regulating valve 5, adapted to regulate the flow delivered to the metering device 6. In particular, the regulating valve 5 is adapted to return an excess flow of fuel reaching the metering unit 6 at the inlet of the positive-displacement pump 4, as a function of the pressure difference across the metering device 6. The regulating valve 5 also serves to keep the fuel pressure differential Δ entre constant between the upstream and downstream of the metering device 6.
    Typically, the regulating valve 5 comprises a movable shutter acting against the action of a calibrated spring on a predetermined value of the pressure differential ΔΡ to be maintained. The shutter is generally perforated so as to evacuate fuel on a pipe leading to the recirculation loop, according to its position of equilibrium against the action of the spring.
    An example of a control valve 5 which can be used here has been described in document FR 1655944, filed on June 27, 2016 by the Applicant.
    In order to allow precise adjustment for small openings, the metering circuit 1 also comprises a bypass duct 7 placed in parallel with the metering device 6 and comprising a diaphragm 8 of minimum flow rate and a volume flow meter 9.
    The diaphragm 8 has a fixed Sd section, adjusted during preliminary tests carried out on a bench. Typically, the diaphragm may include an orifice of fixed size and shape.
    At the terminals of the diaphragm 8 is applied a pressure difference which, as we saw above, is regulated and fixed by the regulating valve 5. This pressure difference ΔΡ is equal to the pressure difference ΔΡ at the terminals of the metering device 6, since the diaphragm is mounted in parallel with the metering device 6 in the bypass circuit 7.
    The pressure difference ΔΡ can in particular be measured by a differential sensor.
    Furthermore, the pressure drop due to the crossing of the diaphragm 8 is determined by the following formula (B):
    (B)
    Where p is the density of the fuel, ξ is the pressure drop coefficient of diaphragm 8, which is a constant,
    Q is the volume flow through the diaphragm 8 of section Sd.
    However, the pressure upstream and downstream of the diaphragm 8 is known and fixed by the regulating valve 5. It can also be measured using the differential sensor. The section of the diaphragm 8 is determined beforehand by tests carried out on a bench. The volume flow is measured using the volume flow meter 9 which is placed in series with the diaphragm 8 (upstream or downstream of the diaphragm 8, in the bypass duct 7). Finally, the pressure drop coefficient of the diaphragm 8 is a constant: therefore, the ratio is also constant.
    We deduce that, apart from measurement errors, according to formula (B), the volume flow rate Q varies exclusively as a function of the fuel density.
    The diaphragm 8 and the volume flow meter 9 placed in series in the bypass duct therefore form an online densimeter making it possible to improve the overall accuracy of the metering circuit 1.
    Where appropriate, when the metering circuit 1 comprises an electronic card 11, the measurements made by the flow meter 9 are communicated to the electronic card 11 so that the latter deduces the density of the fuel therefrom. The electronic card 11 can then adjust the control setpoint of the metering device 6 taking into account the density of the fuel.
    Alternatively, in the absence of an electronic card 11 in the metering circuit 1, the measurements made by the flow meter 9 are communicated directly to the control unit of the metering device 6.
    In order to estimate the dosing precision obtained thanks to the diaphragm 8 and the addition of the flow meter 9, it is necessary to take into account the calibration precision obtained beforehand during tests carried out on test bench and measurement inaccuracies in operation. normal.
    The accuracy of a volume flow meter 9 is around +/- 0.8% of the measurement. Depending on the flow rate measured, this possible deviation takes into account the entire temperature range. However, in the opposite case, it is possible to measure the temperature in the bypass duct 7 comprising the diaphragm 8 and the flow meter 9 and to apply a correction to the read flow, the turbine flow meters being sensitive to the viscosity of the fluid. .
    In addition, during the preliminary tests carried out on the bench, the electronics are calibrated more finely than on-board electronics. The uncertainty for the characterization (usually +/- 0.5% of the measurement) is therefore lower.
    In what follows, from a conservative point of view, we will consider an identical measurement accuracy in calibration and in operation at all temperatures combined of +/- 0.8% of the measurement.
    Likewise, a differential pressure sensor has an accuracy of + / 0.8% of full scale.
    For the balance sheet, we will consider a scale of 5 bar, i.e. an accuracy of +/- 1% for a measurement of 4 bar (classic value of regulated pressure difference).
    Considering the following formula, defining the volume flow injected:
    where: Q is the flow rate measured in L / h using the volume flow meter 9 p is the fuel density in kg / L
    S is the fuel passage section, linked to the opening of the metering device
    A is the opening of the dosing slot of the metering device 6 in mm, the impact of the pressure and the volume flow rate on the measurement of the fuel density p are determined:
    is :
    and
    All these measurement errors are random. Thus, the error on the density ε ρ will be equal to:
    The error on the flow corrected by the density y = 0.5xy obtained thanks to the diaphragm 8 and the volume flow meter 9 will therefore be -y- = ± 1.15%
    The error on the flow corrected by the pressure difference will be = ± 0.4%.
    It can be seen that in the absence of regulation, the variation in density results in a variation in flow rate from - 6.4% to + 6.1% while with regulation, the variation in flow rate will be within a range of approximately + / 1.6 %, in particular when the metering circuit 1 comprises an electronic card 11. In the absence of the electronic card 11, the variation in flow rate can be between -3% and + 3%.
    The fuel metering with the aid of such a fuel metering circuit 1 then comprises the following steps:
    - determine S1 a pressure difference across the doser 6,
    - measure S2 a volume flow rate of the fuel using the volume flow meter 9,
    - calculate S3, from the pressure difference, the volume flow and constants related to the diaphragm 8, the fuel density,
    - Determine information on the volume flow of fuel and transmit S4 this information to the electronic card 11 so that the electronic card 11 adjusts a control setpoint of the metering device 6 taking into account the density of the fuel.
    It will be noted that the fuel flow is controlled S4 by recirculating a variable fuel flow to the pump 4 by means of the regulating valve 5.
    权利要求:
    Claims (8)
    [1" id="c-fr-0001]
    1. Fuel metering circuit (1) of a turbomachine comprising:
    - a metering device (6),
    - a pump (4) configured to circulate a fuel flow to the metering device (6),
    - a regulating valve (5) configured to return an excess flow of fuel delivered to the metering device (6) towards the pump (4) according to a difference in fuel pressure at the terminals of the metering device (6),
    - a diaphragm (8) and
    - a volume flow meter (9) configured to determine the volume flow of fuel passing through the diaphragm (9), the metering circuit (1) being characterized in that the diaphragm (8) and the volume flow meter (9) are mounted in parallel of the metering device (6) in a bypass duct (7), downstream of the regulating valve (5), in order to determine a density of the fuel circulating in the metering circuit (1).
    [2" id="c-fr-0002]
    2. Metering circuit (1) according to claim 1, wherein the volume flow meter (9) is mounted upstream or downstream of the diaphragm (8).
    [3" id="c-fr-0003]
    3. Metering circuit (1) according to one of claim 1 or 2, further comprising an electronic card (11) configured to receive information from the volume flow meter (9) on the volume flow of the fuel and adjust a control setpoint. of the metering device (6) taking into account the fuel density thus determined.
    [4" id="c-fr-0004]
    4. Metering circuit (1) according to one of claims 1 to 3, wherein the pump (4) comprises a volumetric pump (4).
    [5" id="c-fr-0005]
    5. A turbomachine comprising a fuel metering circuit (1) according to one of claims 1 to 4.
    [6" id="c-fr-0006]
    6. Fuel metering method (S) implemented in a fuel metering circuit (1) according to one of claims 1 to 4, characterized in that it comprises the following steps:
    - determine (S1) a pressure difference across the doser (6),
    - measure (S2) a volume flow of fuel using the volume flow meter (9),
    - calculate (S3), from the pressure difference, the volume flow and constants related to the diaphragm (8), the fuel density.
    [7" id="c-fr-0007]
    7. Method (S) of metering according to claim 6, further comprising a step (S4) during which the flow meter transmits information on the volume flow of fuel to an electronic card (11) and the electronic card (11) adjusts a metering control setpoint (6) taking into account the fuel density.
    [8" id="c-fr-0008]
    8. Method (S) of metering according to one of claims 6 or 7, wherein the fuel flow is controlled (S4) by recirculating a variable fuel flow to the pump (4) by means of the regulating valve (5).
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    同族专利:
    公开号 | 公开日
    RU2020106377A|2021-08-13|
    RU2020106377A3|2021-11-12|
    WO2019012238A1|2019-01-17|
    RU2763240C2|2021-12-28|
    FR3069021B1|2019-07-26|
    EP3652425A1|2020-05-20|
    US20210087980A1|2021-03-25|
    CA3069609A1|2019-01-17|
    CN111033016A|2020-04-17|
    EP3652425B1|2021-05-26|
    BR112020000625A2|2020-07-14|
    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    US4809499A|1987-03-20|1989-03-07|United Technologies Corporation|Densimeter|
    FR3022000A1|2014-06-05|2015-12-11|Snecma|FLUID TURBOMACHINE SUPPLY SYSTEM WITH LOW PRESSURE PUMP ASSEMBLY COMPRISING TWO PARALLEL PUMPS|
    US20160123860A1|2014-10-31|2016-05-05|Simmonds Precision Products, Inc.|Fuel density determination|WO2020188059A1|2019-03-19|2020-09-24|Safran Aircraft Engines|Method for monitoring the operating state of a hydromechanical unit|
    WO2021001563A1|2019-07-03|2021-01-07|Safran Aircraft Engines|Method for determining the density of fuel for metering fuel in a fuel supply circuit of an aircraft engine|FR2818690B1|2000-12-22|2003-03-21|Snecma Moteurs|TWO-LEVEL PRESSURIZATION VALVE CONTROLLED BY A FUEL DISPENSER|
    FR2825120B1|2001-05-25|2003-12-12|Snecma Moteurs|DOSER WITH 2 INTEGRATED OUTPUTS|
    US7526911B2|2006-02-03|2009-05-05|Rolls-Royce Corporation|Gas turbine engine fuel system with fuel metering valve|US20210140432A1|2019-11-08|2021-05-13|Hamilton Sundstrand Corporation|Simultaneously pumping and measuring density of aircraft fuel|
    法律状态:
    2019-01-18| PLSC| Publication of the preliminary search report|Effective date: 20190118 |
    2020-06-23| PLFP| Fee payment|Year of fee payment: 4 |
    2021-06-23| PLFP| Fee payment|Year of fee payment: 5 |
    优先权:
    申请号 | 申请日 | 专利标题
    FR1756706|2017-07-13|
    FR1756706A|FR3069021B1|2017-07-13|2017-07-13|FUEL DOSING SYSTEM AND METHOD COMPRISING VARIABILITY OF FUEL DENSITY|FR1756706A| FR3069021B1|2017-07-13|2017-07-13|FUEL DOSING SYSTEM AND METHOD COMPRISING VARIABILITY OF FUEL DENSITY|
    CA3069609A| CA3069609A1|2017-07-13|2018-07-13|Fuel metering circuit and method with compensation for fuel-density variability|
    US16/630,705| US20210087980A1|2017-07-13|2018-07-13|Fuel metering circuit and method with compensation for fuel-density variability|
    BR112020000625-4A| BR112020000625A2|2017-07-13|2018-07-13|fuel measurement circuit, turbomachinery and fuel measurement method|
    CN201880049203.6A| CN111033016A|2017-07-13|2018-07-13|Fuel metering circuit and method for compensating for fuel density variability|
    RU2020106377A| RU2763240C2|2017-07-13|2018-07-13|Fuel dosing circuit and method with compensation for fuel density variability|
    PCT/FR2018/051778| WO2019012238A1|2017-07-13|2018-07-13|Fuel metering circuit and method with compensation for fuel-density variability|
    EP18758920.5A| EP3652425B1|2017-07-13|2018-07-13|Fuel metering circuit and method with compensation for fuel-density variability|
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