Hydrogen Fuel Delivery System

Abstract

The hydrogen fuel delivery system (300) includes a fuel line (312) having an inlet (315) and an outlet (316), a liquid fuel pump (307) configured to provide a flow of liquid hydrogen fuel from a hydrogen fuel storage tank (308) to the fuel line inlet (315), a heat exchanger (306) having first and second fluid paths (313, 314), the fuel line (312) passing through the first fluid path (313), and a preheater line (317) having an inlet (318) connected to the fuel line (312) between the fuel line inlet (315) and the heat exchanger (306), for preheating the fuel. The system includes a first control valve (301) and a burner (305) between a preheater line inlet (318) and a heat exchanger (306), a preheater line (317) passing through a second fluid path (314) of the heat exchanger (306) toward a preheater line outlet (319), a second control valve (302) in a fuel line (312) between the heat exchanger (306) and the fuel line outlet (316), a first temperature sensor (321) configured to measure a first fuel temperature (T1) in the fuel line (312) between the heat exchanger (306) and the second control valve (302), and an input target temperature (T1) compared to the first fuel temperature (T1). Target and a control system (400) configured to provide a first control signal (CV1) that controls operation of the first control valve (301) in response to the fuel flow rate (mbfuel) through the preheater line (317) and in response to a measure of fuel flow rate (mbfuel) through the preheater line (317).

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to a hydrogen fuel delivery system and a method of operating a hydrogen fuel delivery system. [Background technology]

[0002] The use of hydrogen as an alternative to liquid hydrocarbon fuels for aircraft propulsion presents technical challenges. Given the low density of hydrogen in gaseous form, storing significant quantities requires storage at high pressure at ambient temperature or at low pressure in liquid form at cryogenic temperatures. For aircraft applications, cryogenic storage is a more practical solution given the ability to store larger quantities at low pressure and with reduced overall weight and volume. Providing a supply of gaseous fuel to generate energy, whether in a gas turbine or fuel cell, requires that the liquid fuel supply be heated from a cryogenic temperature prior to being reacted or ignited. Therefore, additional and differently configured features and control systems are required to control the supply of hydrogen fuel compared to those used for traditional liquid hydrocarbon fuels such as kerosene. Summary of the Invention [Means for solving the problem]

[0003] According to a first aspect, there is provided an aircraft hydrogen fuel delivery system, comprising: a fuel line having an inlet and an outlet; a liquid fuel pump configured to provide a flow of liquid hydrogen fuel from the hydrogen fuel storage tank to the fuel line inlet; a heat exchanger having first and second fluid paths, the fuel line passing through the first fluid path; a preheater line having an inlet connected to the fuel line between the fuel line inlet and a heat exchanger, the preheater line including a first control valve and a burner between the preheater line inlet and the heat exchanger, the preheater line passing through a second fluid path of the heat exchanger to a preheater line outlet; a second control valve in the fuel line between the heat exchanger and the fuel line outlet; a first temperature sensor configured to measure a first fuel temperature in the fuel line between the heat exchanger and the second control valve; and a control system configured to provide a first control signal that controls operation of the first control valve in response to an input target temperature compared to the first fuel temperature and in response to a measure of fuel flow rate through the preheater line. The fuel delivery system a first pressure sensor configured to measure a first fuel pressure in the preheater line between the preheater line inlet and the first control valve; a second pressure sensor configured to measure a second fuel pressure in the preheater line between the first control valve and the burner; a first temperature sensor configured to measure a first fuel temperature in the preheater line between the preheater line inlet and the first control valve; The control system is configured to derive a measure of fuel flow rate from the first and second fuel pressures and the second fuel temperature.

[0004] The control system may include a first lookup table configured to output a measure of fuel flow rate in response to the first and second fuel pressures, the first fuel temperature, and the first control signal.

[0005] The fuel delivery system may include a mass flow meter configured to measure the mass flow rate of the fluid in the preheater line and provide a measure of the fuel flow rate to the control system.

[0006] The control system may include a first control loop and a second control loop, the first control loop configured to receive a measure of fuel flow rate and an output from the second control loop and output a first control signal, and the second control loop configured to receive an input target temperature and a first fuel temperature and provide an output to the first control loop.

[0007] The first control loop may be configured to determine a first difference between the measure of fuel flow and the output of the second control loop and provide a first control signal.

[0008] The second control loop may be configured to determine a second difference between the first fuel temperature and the input target temperature and provide an output to the first control loop.

[0009] The fuel delivery system may further include an electric heater in the preheater line between the preheater line inlet and the burner, the electric heater configured to receive a heater current to heat the fuel in the preheater line. The electric heater may be between the preheater line inlet and the first control valve. The control system may be configured to control the heater current in response to a measure of the fuel flow rate. The control system may include a second lookup table configured to receive the measure of the fuel flow rate and output the heater current.

[0010] The control system may further include a third lookup table configured to receive the measure of pump speed of the liquid fuel pump, the pressure of the fuel at the pump output, the first temperature, and the target temperature, and to provide a feedforward control signal to the first control loop.

[0011] According to a second aspect, there is provided an aircraft propulsion system, the aircraft propulsion system comprising: a hydrogen fuel storage tank; a fuel delivery system according to a first aspect; Gas turbine engines and Equipped with The fuel line outlet is connected to provide a supply of hydrogen fuel to a combustor of the gas turbine engine.

[0012] According to a third aspect, there is provided an aircraft comprising the aircraft propulsion system of the second aspect.

[0013] According to a fourth aspect, there is provided a method of operating an aircraft hydrogen fuel delivery system, the aircraft hydrogen fuel delivery system comprising: a fuel line having an inlet and an outlet; a liquid fuel pump configured to provide a flow of liquid hydrogen fuel from the hydrogen fuel storage tank to the fuel line inlet; a heat exchanger having first and second fluid paths, the fuel line passing through the first fluid path; a preheater line having an inlet connected to the fuel line between the fuel line inlet and a heat exchanger, the preheater line including a first control valve and a burner between the preheater line inlet and the heat exchanger, the preheater line passing through a second fluid path of the heat exchanger to a preheater line outlet; a second control valve in the fuel line between the heat exchanger and the fuel line outlet; a first temperature sensor configured to measure a first fuel temperature in the fuel line between the heat exchanger and the second control valve; Control system and Equipped with The control system provides a first control signal that controls operation of the first control valve in response to the input target temperature compared to the first fuel temperature and in response to a measure of fuel flow rate through the preheater line.

[0014] The fuel delivery system a first pressure sensor configured to measure a first fuel pressure in the preheater line between the preheater line inlet and the first control valve; a second pressure sensor configured to measure a second fuel pressure in the preheater line between the first control valve and the burner; a first temperature sensor configured to measure a first fuel temperature in the preheater line between the preheater line inlet and the first control valve; The control system derives a measure of fuel flow rate from the first and second fuel pressures and the second fuel temperature.

[0015] The control system may include a first lookup table that outputs a measure of fuel flow rate as a function of the first and second fuel pressures, the first fuel temperature, and the first control signal.

[0016] The fuel delivery system may further comprise a mass flow meter configured to measure the mass flow rate of the fluid in the preheater line and provide a measure of the fuel flow rate to the control system.

[0017] The control system may include a first control loop and a second control loop, the first control loop receiving a measure of fuel flow rate and an output from the second control loop and outputting a first control signal, and the second control loop receiving an input target temperature and a first fuel temperature and providing an output to the first control loop.

[0018] The first control loop may determine a first difference between the measure of fuel flow and the output of the second control loop and provide a first control signal.

[0019] The second control loop may determine a second difference between the first fuel temperature and the input target temperature and provide an output to the first control loop.

[0020] The fuel delivery system may further include an electric heater in the preheater line between the preheater line inlet and the burner, the electric heater receiving a heater current to heat the fuel in the preheater line. The electric heater may be between the preheater line inlet and the first control valve. The control system may control the heater current in response to a measure of fuel flow. The control system may include a second lookup table that receives the measure of fuel flow and outputs the heater current.

[0021] The control system may further include a third lookup table that receives the measure of pump speed of the liquid fuel pump, the pressure of the fuel at the pump output, the first temperature, and the target, and provides a feedforward control signal to the first control loop.

[0022] Embodiments are described below by way of example only and with reference to the accompanying drawings which are purely schematic and not to scale. [Brief explanation of the drawings]

[0023] [Figure 1] 1 is a schematic diagram of an exemplary hydrogen-fueled passenger aircraft equipped with a hydrogen-fueled turbofan engine; [Figure 2] FIG. 2 is a schematic diagram showing the flow of hydrogen fuel from a storage tank to a turbofan engine. [Figure 3] 1 is a schematic diagram of an exemplary hydrogen fuel delivery system. [Figure 4] FIG. 4 is a schematic diagram of an exemplary control system for the hydrogen fuel delivery system of FIG. 3. [Figure 5] FIG. 1 is a schematic diagram of an exemplary fuel pump speed control system. [Figure 6] FIG. 1 is a schematic diagram of an exemplary fuel valve control system. [Figure 7] FIG. 4 is a schematic diagram of an alternative exemplary control system for the hydrogen fuel delivery system of FIG. 3. [Figure 8] FIG. 1 is a schematic diagram of an exemplary engine electronic controller (EEC). [Figure 9] FIG. 4 is a schematic diagram illustrating the relationship between fuel pump speed and engine speed demand. [Figure 10] FIG. 2 is a schematic diagram of an exemplary burner air inlet valve control system. DETAILED DESCRIPTION OF THE INVENTION

[0024] A hydrogen-powered passenger aircraft is shown in Figure 1. In this example, passenger aircraft 101 is a substantially conventional tube-and-wing twin-jet configuration having a center fuselage 102 and substantially identical underwing mounted turbofan engines 103. Turbofan engines 103 may be, for example, geared turbofan engines.

[0025] A hydrogen storage tank 104 located within the fuselage 104 for hydrogen fuel supply is connected to a core gas turbine 105 within the turbofan engine 103 via a fuel delivery system. In the example shown, the hydrogen storage tank 104 is a cryogenic hydrogen storage tank that stores hydrogen fuel in a liquid state, in the specific example at 20 K. The hydrogen fuel may be pressurized to between about 1 bar and 3 bar, for example, about 2 bar.

[0026] A schematic block diagram illustrating the flow of hydrogen fuel to a gas turbine engine is shown in FIG. 2, which illustrates an exemplary aircraft propulsion system 200. Hydrogen fuel is obtained from hydrogen storage tanks 104 by a fuel delivery system 201 and delivered to the core of a gas turbine 105. For clarity, only one of the gas turbines is shown. In this illustrated embodiment, the gas turbine 105 is a simple cycle gas turbine engine. In other embodiments, a complex cycle may be implemented with gas path fuel cooling.

[0027] 2 , the gas turbine 105 includes, in axial series, a low-pressure compressor 202, an interstage duct 203, a high-pressure compressor 204, a diffuser 205, a fuel injection system 206, a combustor 207, a high-pressure turbine 208, a low-pressure turbine 209, and a core nozzle 210. The fuel injection system 206 may be a lean direct fuel injection system. The high-pressure compressor 204 is driven by the high-pressure turbine 208 via a first shaft 211, and the low-pressure compressor 202 is driven by the low-pressure turbine 209 via a second shaft 212. In alternative examples, the gas turbine 105 may include more than two shafts.

[0028] In a geared turbofan engine, the low-pressure turbine 209 also drives a fan 213 via a reduction gearbox 214. The reduction gearbox 214 receives input drive from a second shaft 212 and provides output drive to the fan 213 via a fan shaft 215. The reduction gearbox 214 may be an epicycle gearbox, which may be in a satellite, star, or compound configuration. In a further alternative, the reduction gearbox 214 may be a countershaft type reduction gearbox or another type of reduction gearbox. It will also be appreciated that the principles disclosed herein may be applied to a direct drive type turbofan engine, i.e., there is no reduction gearbox between the low-pressure turbine 209 and the fan 213.

[0029] In operation, the fuel delivery system 201 is configured to obtain liquid hydrogen fuel from the cryogenic hydrogen storage tank 104 and provide the fuel in gaseous form to the fuel injection system 206. This requires that the amount of liquid fuel from the tank 104 be controlled, and a controlled amount of heat provided to the fuel to ensure the fuel in gaseous form is at the required temperature prior to injection into the gas turbine 105, or in an alternative arrangement, into the hydrogen fuel cell.

[0030] 3 is a block diagram illustrating an exemplary hydrogen fuel delivery system 300 in greater detail. The fuel delivery system 300 includes a cryogenic fuel storage tank 308 that provides a supply of liquid fuel to a liquid fuel pump 307. The liquid fuel pump 307 is configured to provide a flow of liquid hydrogen fuel from the cryogenic storage tank 308 to a fuel line 312. The fuel line 312 has an inlet 315 to the liquid fuel pump 307 and an outlet 316 for providing gaseous fuel to a gas turbine and / or a fuel cell.

[0031] A heat exchanger 306 having first and second fluid paths 313, 314 is provided for exchanging heat between fluids passing along the first and second fluid paths 313, 314. The fuel line 312 is heated by exchanging heat with fluid passing through the first fluid path 313 and the second fluid path 314.

[0032] A preheater line 317 has an inlet 318 connected to the fuel line 312 between the fuel line inlet 315 and the heat exchanger 306. The preheater line 317 is positioned to extract a controlled amount of fuel from the fuel line 312, which is then combusted to provide preheat to the fuel flowing through the fuel line 312. The preheater line 317 includes a first control valve 301 and a burner 305 disposed in series between the preheater line inlet 318 and the heat exchanger 306. The fuel in the preheater line 317 passes through the first control valve 301 and into the burner 305, where the fuel is combusted with air provided from an air source 311 via an air supply line 322. The air source 311 may be, for example, a compressor or a bypass of a gas turbine engine. The resulting combusted fuel passes from the discharge 323 of the burner 305 into the second fluid path 314 of the heat exchanger 306 and towards the outlet 319, which may be connected to a bypass of the gas turbine engine.

[0033] The purpose of the preheater line 317 is to regulate (within an acceptable range) the temperature T1 of the gaseous fuel entering the second control valve 302, as measured by the first temperature sensor 321. This is accomplished by controlling the amount of cryogenic fuel passing through the preheater line 317 via the first control valve 301 while maintaining the operability of the preheater and not exceeding limits.

[0034] Burner 305 and heat exchanger 306 may be separate components connected by preheater line 317 or may optionally be integrated with first control valve 301 and / or electric heater 309.

[0035] An electric heater 309 may be provided in the preheater line 317 between the preheater line inlet 318 and the burner 305, the electric heater 309 being configured to receive a heater current I_heater to heat the fuel in the preheater line 317 prior to entering the burner 305. The electric heater 309 may be located between the first control valve 301 and the burner 305, or alternatively, may be located between the preheater line inlet 318 and the first control valve 301, as in the example of FIG. 3. An advantage of locating the electric heater 309 before rather than after the first control valve 301 is that the first control valve 301 may not need to operate at cryogenic temperatures.

[0036] A second control valve 302 is provided in the fuel line 312 between the heat exchanger 306 and the fuel line outlet 316. The second control valve 302 controls the flow of fuel, here in gaseous form, to the outlet 316 after it has been heated by passing through the heat exchanger 306. One or more other valves 304, 303 may also be provided. The first overspeed valve 303 may be a solenoid overspeed relief valve controlled by a first on / off control signal OV1. The second overspeed valve 304 may be a solenoid overspeed shutoff valve controlled by a second on / off control signal OV2. During normal operation, the first overspeed valve 303 closes and the second overspeed valve 304 opens, allowing fuel from the fuel line 312 to flow to the gas turbine or fuel cell. In the event of an engine overspeed or shaft break scenario, the pump 307 is turned off, the first overspeed valve 303 opens to allow fuel to escape from the fuel line 312, and the second overspeed valve 304 closes to stop fuel from passing to the gas turbine.

[0037] The position of each of the control valves 301, 302 may be controlled through the use of a position measuring device such as an LVDT or RVDT (Linear or Rotary Variable Differential Transformer) in combination with a motor that drives the valve to the required position. Thus, the values ​​CV1, CV2 represent the demand signal provided to each control valve 301, 302, and the position of the control valves 301, 302 is controlled by a control loop within the control valve that drives the motor to the required position.

[0038] The pump 307 may be controlled by controlling the speed of a motor that drives the pump 307, for example by receiving a signal indicative of the desired pump speed Np and outputting a current of the required current, frequency and relative phase to the coils of the electric motor that drives the pump 307.

[0039] The operation of the fuel delivery system 300 is controlled using various pressure and temperature measurements. A first pressure sensor 318 is configured to measure a first fuel pressure P1 in the preheater line 317 between the preheater line inlet 318 and the first control valve 301. The first pressure sensor 318 may be in the fuel line 312 or in the portion of the preheater line 317 between the fuel line 312 and the first control valve 301 and will typically measure the pressure of the fuel in supercritical form as it exits the liquid fuel pump 307. A second fuel pressure sensor 319 is configured to measure a second fuel pressure P2 in the preheater line 317 between the first control valve 301 and the burner 305. A first temperature sensor 320 measures a first fuel temperature T1 in the fuel line 312 between the heat exchanger 306 and the second control valve 302. A second temperature sensor 321 in the preheater line 317 between the preheater line inlet 318 and the first control valve 301 measures the temperature T2 of the fuel passing through the preheater line 317 and into the first control valve 301. The difference between the first and second fuel pressures P1 and P2, in combination with the second fuel temperature T2, may be used to determine the flow rate of the fuel through the first control valve 301. Alternatively or additionally, a mass flow meter 327 may be provided in the preheater line 317 between the preheater line inlet 318 and the first control valve 301, the mass flow meter 327 being configured to measure the mass flow rate of fluid in the preheater line 317 and provide a measure of fuel flow to a control system for operating the fuel delivery system 300, as described in further detail below.

[0040] The fuel delivery system 300 is configured to adjust the first fuel temperature T1 to a desired target temperature T1 Targert The temperature is controlled to reach or be maintained at or around that temperature.

[0041] A third pressure sensor 324 may be configured to measure a third fuel pressure P3 in the fuel line 312 between the heat exchanger 306 and the second control valve 302. A fourth pressure sensor 325 may be configured to measure a fourth fuel pressure P4 in the fuel line 312 between the second control valve 302 and the fuel line outlet 316. Knowledge of the first fuel temperature T1 and the third and fourth fuel pressures P3, P4 allows a measure of fuel flow to be determined through the second control valve, as described in further detail below.

[0042] The third temperature sensor 326 may be configured to measure the burner exhaust gas temperature T3.

[0043] The fourth temperature sensor 329 may be configured to measure the temperature T 4 of the fuel flowing in the fuel line 312 between the fuel pump 307 and the first fluid path 313 of the heat exchanger 306 .

[0044] The fifth pressure sensor 328 may be configured to measure the pressure of the fuel in the fuel line 312 at the fuel pump outlet 315 .

[0045] A third control valve 310 may be provided in the air supply line 322 to control the amount of air provided to the burner 305 and therefore through the heat exchanger 306. The third control valve 310 may be controlled using a control signal CV3 with a separate control loop that is dependent on the measured fuel flow rate through the preheater line 317. An exemplary control system for the control valve 310 is shown in FIG. 10, which is described in further detail below. Control of the third control valve 310 may be used to maintain the metal temperature of the heat exchanger 306 above freezing. An alternative arrangement is to have the outlet temperature T3 from the burner 305 be controlled at a constant value (e.g., about 1000 K) or according to a schedule (T3 Target ) The control signal CV3 provided to the valve 310 may then be set according to the appropriate schedule (T1 Target ) can be used to adjust the outlet temperature T1 of the heat exchanger 306 according to

[0046] The operation of the fuel delivery system 300 is controlled by a control system, an example of which is shown in Figure 4. The control system 400 receives first and second pressures P1, P2 and first and second fuel temperatures T1, T2 from pressure sensors 318, 319 and temperature sensors 320, 321, and calculates an input target temperature T1. Target The first control valve 301 is configured to provide a first control signal CV1 that controls the operation of the first control valve 301 depending on

[0047] The control system 400 includes a first lookup table 401 that takes as inputs the first and second fuel pressures P1, P2, the second fuel temperature T2, and the current value of a first control signal CV1 provided to the first control valve 301. The first lookup table 401 outputs a fuel flow measure mbfuel that is dependent on the inputs P1, P2, T2, and CV1, and is provided to a first control loop 402. In an alternative arrangement, the fuel flow measure mbfuel may be provided from a mass flow meter 327 in the preheater line 317 instead of the first lookup table 401. The first or inner control loop 402 takes the mbfuel input along with the output from the second or outer control loop 403 and provides a value for CV1 from the controller K1. The second control loop 403 receives the inputs T1 and T1. Target , i.e., the measured fuel temperature T1 between the heat exchanger 306 and the second control valve 302, and the target temperature T1 Target and sends T1 and T1 to the first control loop 402 from the controller K2. Target The output from controller K2 of the second control loop 403 is compared to the fuel flow measure mbfuel in the first control loop 401, and controller K1 provides an output control signal CV1 for the first control valve 301. The controllers K1, K2 in the first and second control loops 402, 403 are typically PID controllers.

[0048] The output mbfuel, if present, may be used to control the current supplied to the electric heater 309. A second lookup table 404 takes as input the mbfuel output from the first lookup table 401 (or from the mass flow meter 327) and outputs a heater current I_heater that controls the current provided to the electric heater 309. The heater current supplied will increase as the fuel flow measure increases, although this may be a non-linear relationship that the second lookup table 404 may be configured to indicate. The heater current may alternatively be controlled by switching the current between an on and off state, where the on / off duty cycle determines the average power supplied to the heater 309.

[0049] Mass flow rate through the valve

number

number

[0050] This characteristic may be calculated in real time using compressible flow equations (known to those skilled in the art) or may be stored as a value referenced through a map and lookup function in ROM. A first lookup table 401 stores relationships for applicable pressure and temperature ranges and correspondingly outputs a value for the fuel mass flow rate, mbfuel. The advantage of using a lookup table rather than a mass flow meter is that flow meters capable of measuring with the required accuracy and under the required conditions tend to be significantly more expensive than using pressure and temperature sensors in combination with a lookup table.

[0051] The first control loop 402 controls the target fuel temperature T1 set by the second control loop 403. Target The second control loop 403 is used to set the value of CV1, which sets the position of the first control valve 301 to deliver the target fuel temperature T1. The current fuel mass flow rate is estimated using the first control valve position CV1 and a mass table estimate through the measured system parameters P1, P2, and T2 (or by the mass flow meter 327 measurement, if present). Target Both control loops 402, 403 will also generally need to include anti-windup logic to ensure that both control loops operate within defined limits, such as maintaining minimum and / or maximum fuel-to-air ratios for burner system 305 derived from known requirements for factors such as lean and rich mixtures and blowout.

[0052] To provide improved transient response, feedforward inputs may be incorporated into the control system 400, as shown by the third lookup table 405 in Figure 4. The feedforward inputs are based on the pump speed Np, the input fuel pressure P5 measured by the fifth pressure sensor 328 at the fuel pump outlet 315, the first fuel temperature T1, and the target temperature T1. Target may be input into a third lookup table 405, which provides a pre-calculated value for the preburner fuel flow rate FFPrBFuel required to deliver the target temperature, taking into account the effect of the heat exchanger 306.

[0053] The fuel pump volumetric flow rate Q is proportional to the pump speed Np, and the fuel pump pressure rise is proportional to Np 2 The fuel pump 307 may comprise a single pump driven by a single electric motor, or may be multiple pumps each driven by an electric motor or alternatively from a gearbox coupled to one of the gas turbine spools. For the propulsion system to generate the required thrust over the flight envelope, the required mass flow rate for the fuel delivery system is proportional to

number

number

[0054]

number

[0055] Thereby, the fuel pump speed may be controlled to achieve the desired fuel pressure level P5 according to the engine thrust level (N1demand) requested from the aircraft by taking into account engine inlet conditions (if necessary). An example of the relationship between fuel pump pressure and N1demand is shown schematically in Figure 9. As engine thrust demand increases, the fuel pump speed increases, but the relationship is not linear and constant.

[0056] 5 shows exemplary liquid fuel pump control logic in the form of a lookup table 501 that takes as inputs an altitude ALT, a Mach number Mn, and an engine thrust demand N1demand, and provides as an output a demand signal Npdemand for the liquid fuel pump 307. The demand signal is then provided to a speed control loop for controlling the liquid fuel pump 307. The lookup table 501 incorporates a relationship between N1demand and Np, for example, as shown in FIG.

[0057] The gas control valve 302 (FIG. 3) is the main fuel metering valve for the system 300. The purpose of controlling the valve 302 is to control the amount of gaseous hydrogen entering the combustor. FIG. 6 shows a control system 600 configured to provide a control signal CV2 for the second control valve 302. The control system 600 includes a lookup table 601 and a control loop 602. The lookup table 601 takes as inputs the third and fourth fuel pressures P3, P4 from the third and fourth fuel pressure sensors 324, 325, the first fuel temperature T1 from the first temperature sensor 320, and the control signal CV2. The lookup table 601 outputs a measure of fuel flowing through the second control valve 302 and provides it to the control loop 602, which compares the measure of fuel to the fuel demand signal WFDemand and outputs a control signal CV2 for controlling the second control valve 321. The fuel demand signal may be obtained by a model such as the model described in U.S. Patent No. 5,083,277. The lookup table 601 may be replaced with compressible fluid equations known to those skilled in the art if this is advantageous to save memory space in the lookup table.

[0058] To ensure satisfactory operation of the fuel delivery system, it is important that the heat exchangers do not become iced under any conditions. For example, flight idle conditions can lead to icing if the control target is not set correctly. One way to avoid this is to set a target fuel temperature T1 depending on the flight conditions and available thrust. Target 7 shows an example control system 700 in which this is implemented by adding a fourth lookup table 706 to the control system described above in connection with FIG. 4. The output T1 from the fourth lookup table 706 Targett is obtained from the inputs, N1Demand, ALT, Mn, and T20 (defined above). A predefined output may be derived by utilizing basic heat exchanger equations (such as the Number of Transfer Units (NTU) method) to calculate the metal temperature of the heat exchanger at a given set of conditions. This approach may work well, but it cannot necessarily handle transient behavior. An alternative approach may be to use an observer (such as a Kalman filter) to estimate the current metal temperature of the heat exchanger, where the observer takes into account the thermodynamics of the heat exchanger and instead controls THxMetal (the output of the observer estimate of the metal temperature) to be above 0°C. Thus, in a general aspect, the control system 700 may be configured to maintain the first fuel temperature T1 above a minimum temperature to prevent icing of the heat exchanger 306, i.e., to maintain the heat exchanger metal temperature THxMetal above 0°C. The control system 700 may be configured to control the fuel temperature T1 based on a "Lowest-wins" criteria between T1 and the heat exchanger metal temperature THxMetal. The controller 700 may be a predictive controller that includes multiple explicit constraints on T1, THxMetal, and other temperatures within the system 700.

[0059] The control system described above may be incorporated into an engine electronic controller (EEC) 801, as shown schematically in Figure 8. The EEC 801 takes as inputs the various fuel pressures P1, P2, P3, P4, P5, temperatures T1, T2, T3, T4, pump speed Np, and valve positions CV1, CV2, CV3, and outputs control signals to a pump controller 802, a valve controller 803, and an electric heater controller 804 to operate the fuel delivery system 300.

[0060] An exemplary control system 1000 for providing the control signal CV3 to the third control valve or burner air inlet valve 310 is shown in FIG. 10. The control system 1000 includes first and second control loops 1001, 1002 and first and second lookup tables 1003, 1004. The first lookup table 1003 receives a pressure P30 from the air supply line inlet pressure sensor 330, a pressure P2 from the burner inlet pressure sensor 319, and a temperature T26 from the air supply inlet temperature sensor 331. The pressure P30 may be the pressure at the end of the HP compressor 204 (FIG. 2), and the temperature T26 may be the temperature at the inlet of the HP compressor 204 and the outlet of the LP compressor 202. These may be measured within the engine or by dedicated sensors upstream of the control valve 310. Similar to lookup table 401 of control system 400 of FIG. 4, lookup table 1001 outputs a measure of mass flow rate through control valve 310 .

[0061] A second lookup table 1004 takes as inputs N1Demand, ALT, Mn, and T20 and calculates the input target temperature T1 Target to the second control loop 1002, which is similar to the look-up table 706 of FIG. 7 described above.

[0062] The first and second control loops 1001, 1002 operate similarly to the control loops 402, 403 described above, i.e., comparing input values ​​and providing an output control signal CV3. The second control loop 1002 compares T1 with T1Target, and controller K3 provides an input to the first control loop 1001, which compares the input with the output from the first lookup table 1003, and controller K4 provides the control signal CV3 output.

[0063] Various examples have been described, each of which includes various combinations of features. It will be recognized by those skilled in the art that any feature may be used separately or in combination with any other feature, except where expressly mutually exclusive, and therefore the disclosed subject matter extends to and includes all such combinations and subcombinations of that or more features described herein.

[0064] This application is based on and claims the benefit of priority from United Kingdom of Great Britain & Northern Ireland Patent Application No. GB2211357.5, filed on August 4, 2022, the entire contents of which are incorporated herein by reference.

Claims

1. A fuel line (312) having an inlet (315) and an outlet (316), A liquid fuel pump (307) is configured to provide a flow of liquid hydrogen fuel from the hydrogen fuel storage tank (308) to the inlet (315) of the fuel line, A heat exchanger (306) having first and second fluid paths (313, 314), wherein the fuel line (312) includes the first fluid path (313) and the heat exchanger (306), A preheater line (317) having an inlet (318) connected to the fuel line (312) between the inlet (315) of the fuel line and the heat exchanger (306), wherein a first control valve (301) and a burner (305) are provided between the inlet (318) of the preheater line and the heat exchanger (306), and the preheater line (317) includes the second fluid path (314) of the heat exchanger (306) toward the preheater line outlet (319), and the first control valve is located in the preheater line between the inlet of the preheater line and the burner, and the preheater line (317) and A first temperature sensor (321) is configured to measure the first fuel temperature (T1) in the fuel line (312) between the heat exchanger (306) and the outlet of the fuel line, The first fuel temperature (T1) and the target value of the first fuel temperature (T1) Ｔａｒｇｅｔ A control system (400) is configured to provide a control signal (CV1) that controls the operation of the first control valve (301) in accordance with a comparison with and in accordance with a measured value (mbfuel) of the fuel flow rate passing through the preheater line (317), and A hydrogen fuel delivery system (300) equipped with the following.

2. A first pressure sensor (318) is configured to measure the first fuel pressure (P1) in the preheater line (312) between the inlet (318) of the preheater line and the first control valve (301), A second pressure sensor (319) is configured to measure the second fuel pressure (P2) in the preheater line (317) between the first control valve (301) and the burner (305), The system includes a second temperature sensor (321) configured to measure the second fuel temperature (T2) in the preheater line (312) between the inlet (318) of the preheater line and the first control valve (301), The hydrogen fuel delivery system (300) according to claim 1, wherein the control system (400) is configured to derive the measured value of fuel flow rate (mbfuel) from the first and second fuel pressures (P1, P2) and the second fuel temperature (T2), and optionally comprises a first lookup table (401) configured to output the measured value of fuel flow rate (mbfuel) in accordance with the first and second fuel pressures (P1, P2), the first fuel temperature (T1), and the control signal (CV1).

3. The hydrogen fuel delivery system (300) according to claim 1, further comprising a mass flow meter (327) configured to measure the mass flow rate of the fluid in the preheater line (317) and to provide the control system (400) with a corresponding measured value (mbfuel) of the fuel flow rate through the preheater line.

4. The control system (400) comprises a first control loop (402) and a second control loop (403), wherein the first control loop (402) is configured to receive the measured value (mbfuel) of the fuel flow rate through the preheater line and the output from the second control loop (403) and to output the control signal (CV1), and the second control loop (403) is configured to receive the target value (T1) of the first fuel temperature. Ｔａｒｇｅｔ A hydrogen fuel delivery system (300) according to any one of claims 1 to 3, configured to receive the first fuel temperature (T1) and the output of the second control loop to the first control loop (402).

5. (a) The first control loop (402) is configured to determine a first difference between the measured value (mbfuel) of the fuel flow rate through the preheater line and the output of the second control loop (403), and / or to output the control signal (CV1), (b) The second control loop (403) controls the first fuel temperature (T1) and the target value (T1) of the first fuel temperature. Ｔａｒｇｅｔ The hydrogen fuel delivery system (300) according to claim 4, configured to determine a second difference between the first and second control loops and to provide the output of the second control loop to the first control loop (402).

6. The hydrogen fuel delivery system (300) according to any one of claims 1 to 3, further comprising an electric heater (309) in the preheater line (317) between the inlet (318) of the preheater line and the burner (305), wherein the electric heater (309) is configured to receive a heater current (I_heater) to heat the fuel in the preheater line (317).

7. (a) The electric heater (309) is provided between the inlet (318) of the preheater line and the first control valve (301), and / or (b) The hydrogen fuel delivery system (300) according to claim 6, wherein the control system (400) is configured to control the heater current (I_heater) in accordance with the measured value (mbfuel) of the fuel flow rate through the preheater line, and optionally comprises a second lookup table (404) configured to receive the measured value (mbfuel) of the fuel flow rate through the preheater line and output the heater current (I_heater).

8. The control system (400) controls the measured speed (Np) of the liquid fuel pump (307), the fuel pressure (P5) at the outlet (315) of the pump, the first fuel temperature (T1), and the target value (T1) of the first fuel temperature. Ｔａｒｇｅｔ The hydrogen fuel delivery system (300) according to claim 4, further comprising a third lookup table (405) configured to receive a ) and provide a feedforward control signal (FFPrBFuel) to the first control loop (402).

9. The hydrogen fuel delivery system according to any one of claims 1 to 3, further comprising a second control valve (302) disposed in the fuel line between the heat exchanger and the outlet of the fuel line, wherein the first temperature sensor is disposed to measure the first fuel temperature (T1) in the fuel line between the heat exchanger and the second control valve.

10. A method for controlling a hydrogen fuel delivery system (300), wherein the hydrogen fuel delivery system (300) is A fuel line (312) having an inlet (315) and an outlet (316), A liquid fuel pump (307) is configured to provide a flow of liquid hydrogen fuel from the hydrogen fuel storage tank (308) to the inlet (315) of the fuel line, A heat exchanger (306) having first and second fluid paths (313, 314), wherein the fuel line (312) includes the first fluid path (313) and the heat exchanger (306), A preheater line (317) having an inlet (318) connected to the fuel line (312) between the inlet (315) of the fuel line and the heat exchanger (306), comprising a first control valve (301) and a burner (305) between the inlet (318) of the preheater line and the heat exchanger (306), and including the second fluid path (314) of the heat exchanger (306) toward the preheater line outlet (319), wherein the first control valve is located in the preheater line between the inlet and the burner, and the preheater line (317) is located between the inlet (315) of the preheater line and the burner, Equipped with, The aforementioned method, (i) Measuring the first fuel temperature (T1) in the fuel line (312) between the heat exchanger (306) and the outlet of the fuel line, (ii) The first fuel temperature (T1) and the target value (T1) of the first fuel temperature (T1) Ｔａｒｇｅｔ In accordance with a comparison with the measured value (mbfuel) of the fuel flow rate passing through the preheater line (317), a control signal (CV1) is generated to control the operation of the first control valve (301), Methods that include...

11. (a) Measuring the first fuel pressure (P1) in the preheater line (312) between the inlet (318) of the preheater line and the first control valve (301), (b) Measuring the second fuel pressure (P2) in the preheater line (317) between the first control valve (301) and the burner (305), (c) Measuring the first fuel temperature (T1) in the preheater line (312) between the inlet (318) of the preheater line and the first control valve (301), The method according to claim 10, wherein the measured value of fuel flow rate (mbfuel) is derived from the first and second fuel pressures (P1, P2) and the second fuel temperature (T2), and a first lookup table (401) that optionally outputs the measured value of fuel flow rate (mbfuel) according to the first and second fuel pressures (P1, P2), the first fuel temperature (T1), and the control signal (CV1) is used.

12. The method according to claim 10, further comprising using a mass flow meter (327) to measure the mass flow rate of the fluid in the preheater line (317) and obtaining the measured value (mbfuel) of the fuel flow rate through the preheater line.

13. In step (ii) of generating the control signal (CV1), (1) The first fuel temperature (T1) and the target value (T1) of the first fuel temperature Ｔａｒｇｅｔ Determine a first difference between ) and generate a first signal corresponding to the first difference, (2) To generate a second signal corresponding to the measured value (mbfuel) of the fuel flow rate through the preheater line, (3) To generate the control signal (CV1) by determining the second difference between the first and second signals, The method according to any one of claims 10 to 12, including the method described in that claim.

14. The hydrogen fuel delivery system (300) further comprises an electric heater (309) in the preheater line (317) between the inlet (318) of the preheater line and either the burner (305) or the first control valve, the electric heater (309) receiving a heater current (I_heater) to heat the fuel in the preheater line (317), The method includes controlling the heater current (I_heater) according to the measured value (mbfuel) of the fuel flow rate through the preheater line. The method according to any one of claims 10 to 12.

15. The hydrogen fuel delivery system includes a second control valve located in the fuel line between the outlet of the fuel line and the heat exchanger. The method includes controlling the second control valve, The method according to any one of claims 10 to 12.

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