Aircraft fuel oil thermal management system, control method and aircraft

Abstract

The invention discloses an aircraft fuel oil thermal management system, a control method and an aircraft. The thermal management system comprises an aircraft oil return branch, an engine oil return branch and a cascade refrigeration system. The input end of the aircraft oil return branch is connected with the output end of the aircraft heat management main path, the input end of the engine oil return branch is connected with the output end of the engine heat management main path, and the output end of the aircraft oil return branch is connected with the output end of the engine oil return branch; the cascade refrigeration system comprises a low-temperature refrigeration loop, a high-temperature refrigeration loop and an intermediate circulation loop; the first input end of the low-temperature refrigerating circuit is connected with the common end of the aircraft oil return branch and the engine oil return branch, and the first output end of the low-temperature refrigerating circuit is used for being connected with the input end of the fuel oil backflow main circuit; the first input end of the high-temperature refrigerating circuit is used for being connected with the input end of an engine oil return branch, and the first output end of the high-temperature refrigerating circuit is used for being connected with the input end of the combustion chamber. The scheme can effectively reduce the temperature of the fuel tank and improve the heat sink utilization rate of fuel.

Description

Technical Field

[0001] This application relates to the field of aviation technology, specifically to an aircraft fuel thermal management system, control method, and aircraft. Background Technology

[0002] When an aircraft is operating normally, both the aircraft and its engine generate significant heat loads. In related technologies, the aircraft primarily uses fuel as the main heat sink, that is, the fuel in the fuel tank is used to cool the aircraft and engine sequentially, and any excess fuel beyond the combustion chamber's requirements is cooled by ram air and then returned to the fuel tank.

[0003] However, to ensure adequate cooling of all aircraft subsystems, a large amount of fuel is required for cooling. On the one hand, this results in lower fuel temperatures flowing into the combustion chamber, wasting fuel heat sinks; on the other hand, the limited flow of ram air reduces fuel heat dissipation efficiency, leading to a rapid rise in fuel tank temperature and poor overall thermal management performance of the aircraft. Summary of the Invention

[0004] In view of this, this application provides an aircraft fuel thermal management system, control method and aircraft, which can effectively reduce the fuel tank temperature and improve the heat sink utilization rate of fuel.

[0005] To solve the above problems, the technical solution provided in this application is as follows: In a first aspect of this application, an aircraft fuel thermal management system is provided, comprising: an aircraft fuel return branch, an engine fuel return branch, and a cascade refrigeration system; The input end of the aircraft oil return branch is connected to the output end of the aircraft thermal management main circuit, the input end of the engine oil return branch is connected to the output end of the engine thermal management main circuit, and the output end of the aircraft oil return branch is connected to the output end of the engine oil return branch. The cascade refrigeration system includes a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The first input terminal of the cryogenic refrigeration circuit is connected to the common terminal of the aircraft fuel return branch and the engine fuel return branch, and the first output terminal of the cryogenic refrigeration circuit is used to connect to the input terminal of the fuel return main circuit. The first input terminal of the high-temperature refrigeration circuit is used to connect to the input terminal of the engine fuel return branch, and the first output terminal of the high-temperature refrigeration circuit is used to connect to the input terminal of the combustion chamber. The first input terminal of the intermediate circulation circuit is connected to the second output terminal of the cryogenic refrigeration circuit, the first output terminal of the intermediate circulation circuit is connected to the second input terminal of the cryogenic refrigeration circuit, the second input terminal of the intermediate circulation circuit is connected to the second output terminal of the high-temperature refrigeration circuit, and the second output terminal of the intermediate circulation circuit is connected to the second input terminal of the high-temperature refrigeration circuit.

[0006] In one possible implementation, the low-temperature refrigeration circuit includes a first expansion valve, a first evaporator heat exchanger, and a first compressor; the high-temperature refrigeration circuit includes a first condenser heat exchanger, a second expansion valve, and a second compressor; and the intermediate circulation circuit includes a second evaporator heat exchanger, a circulation pump, and a second condenser heat exchanger. The first end of the first evaporative heat exchanger is connected to the first end of the second condensing heat exchanger via the first compressor. The second end of the second condensing heat exchanger is connected to the second end of the first evaporative heat exchanger via the first expansion valve. The first end of the first condensing heat exchanger is connected to the first end of the second evaporative heat exchanger via the second expansion valve. The second end of the second evaporative heat exchanger is connected to the second end of the first condensing heat exchanger via the second compressor. The third end of the second evaporative heat exchanger is connected to the third end of the second condensing heat exchanger. The fourth end of the second condensing heat exchanger is connected to the fourth end of the second evaporative heat exchanger via a circulating pump.

[0007] In one possible implementation, the working medium of the low-temperature refrigeration circuit is pentafluoropropane R245fa, the working medium of the high-temperature refrigeration circuit is methanol, and the working medium of the intermediate circulation circuit is polyalphaolefin (PAO).

[0008] One possible implementation is that the aircraft thermal management circuit includes a numerical control system, an environmental control system, a booster fuel pump, and a hydraulic system. The input end of the numerical control system is used to connect to the fuel tank, and the output end of the numerical control system is connected to the input end of the hydraulic system through the environmental control system and the booster fuel pump in sequence. The output end of the hydraulic system is used to connect to the input end of the aircraft return fuel branch. The engine thermal management main circuit includes a main fuel pump and a fuel / oil heat exchanger. The output end of the hydraulic system is used to connect to the input end of the fuel / oil heat exchanger through the main fuel pump, and the output end of the fuel / oil heat exchanger is used to connect to the input end of the engine return oil branch. The fuel return bus includes a fuel / air heat exchanger. The input end of the fuel / air heat exchanger is used to connect to the first output end of the low-temperature refrigeration circuit, and the output end of the fuel / air heat exchanger is used to connect to the fuel tank.

[0009] In one possible implementation, the aircraft fuel thermal management system further includes: a controller; The controller is used to obtain the first operating parameters based on the fuel temperature limit and the lubricating oil temperature limit, and to obtain the second operating parameters based on the superheat of the condensate outlet of the working medium, the superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel. The aircraft oil return branch and engine oil return branch are controlled to operate under the first operating parameters, and the cascade refrigeration system is controlled to operate under the second operating parameters.

[0010] In one possible implementation, the controller is used to obtain the first operating parameter and the second operating parameter by: The controller is used to obtain the mass flow rate of fuel flowing into the aircraft return fuel branch and the mass flow rate of fuel flowing into the engine return fuel branch through the energy conservation equation and the mass conservation equation; and to obtain the condensation pressure, evaporation pressure, circulation flow rate and maximum circulation temperature of the working medium through the thermodynamic state equation and the energy conservation equation.

[0011] In a second aspect of this application, a control method for an aircraft fuel thermal management system is provided, the system including an aircraft fuel return branch, an engine fuel return branch, and a cascade refrigeration system; The input end of the aircraft oil return branch is connected to the output end of the aircraft thermal management main circuit, the input end of the engine oil return branch is connected to the output end of the engine thermal management main circuit, and the output end of the aircraft oil return branch is connected to the output end of the engine oil return branch. Control methods include: The first operating parameters are obtained based on the fuel temperature limit and the lubricating oil temperature limit. The second operating parameters are obtained based on the superheat of the working medium's condensate outlet, the superheat of the working medium's evaporation outlet, and the fuel heat sink utilization rate. The aircraft oil return branch and the engine oil return branch are controlled to operate under the first operating parameters, and the cascade refrigeration system is controlled to operate under the second operating parameters. The cascade refrigeration system includes a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The first input terminal of the cryogenic refrigeration circuit is connected to the common terminal of the aircraft fuel return branch and the engine fuel return branch, and the first output terminal of the cryogenic refrigeration circuit is used to connect to the input terminal of the fuel return main circuit. The first input terminal of the high-temperature refrigeration circuit is used to connect to the input terminal of the engine fuel return branch, and the first output terminal of the high-temperature refrigeration circuit is used to connect to the input terminal of the combustion chamber. The first input terminal of the intermediate circulation circuit is connected to the second output terminal of the cryogenic refrigeration circuit, the first output terminal of the intermediate circulation circuit is connected to the second input terminal of the cryogenic refrigeration circuit, the second input terminal of the intermediate circulation circuit is connected to the second output terminal of the high-temperature refrigeration circuit, and the second output terminal of the intermediate circulation circuit is connected to the second input terminal of the high-temperature refrigeration circuit.

[0012] One possible implementation involves obtaining the first operating parameter and the second operating parameter, including: The mass flow rates of fuel flowing into the aircraft return fuel branch and the engine return fuel branch are obtained through the energy balance equation and the mass conservation equation; the condensation pressure, evaporation pressure, circulation flow rate, and maximum circulation temperature of the working medium are obtained through the thermodynamic state equation and the heat balance equation.

[0013] One possible implementation involves controlling the aircraft oil return branch and the engine oil return branch to operate under a first operating parameter, and controlling the cascade refrigeration system to operate under a second operating parameter, including: The proportional-integral-differential algorithm controls the aircraft oil return branch and the engine oil return branch to operate under the first operating parameters, and controls the cascade refrigeration system to operate under the second operating parameters.

[0014] In a third aspect of this application, an aircraft is provided, including any of the above-mentioned aircraft fuel thermal management systems, and further comprising: Aircraft thermal management main circuit, engine thermal management main circuit, fuel return main circuit, fuel tank and combustion chamber.

[0015] The aircraft fuel thermal management system provided in this application achieves fuel diversion through the aircraft fuel return branch and the engine fuel return branch, which can effectively increase the temperature of the fuel flowing into the engine thermal management main circuit. The cascade refrigeration system can transfer the fuel heat in the aircraft fuel return branch and the engine fuel return branch to the fuel in the combustion chamber, which can reduce the temperature of the returned fuel and increase the temperature of the fuel flowing into the combustion chamber. The heat load is consumed by the combustion of the fuel in the combustion chamber, thereby realizing the phase change precooling of the returned fuel, adjusting the heat load distribution in the aircraft fuel thermal management system, and effectively improving the heat sink utilization rate of the fuel. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of an aircraft fuel thermal management system in related technologies; Figure 2 A schematic diagram of an aircraft fuel thermal management system provided for an embodiment of this application; Figure 3 This is a schematic diagram of a cascade refrigeration system provided in an embodiment of this application; Figure 4 A schematic diagram of the operating parameters of an aircraft fuel thermal management system provided in an embodiment of this application; Figure 5 A schematic diagram illustrating the performance parameters of an aircraft fuel thermal management system provided in an embodiment of this application; Figure 6 A flowchart illustrating a control method for an aircraft fuel thermal management system provided in this application embodiment. Detailed Implementation

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, the embodiments of this application will be further described in detail below with reference to the accompanying drawings and specific implementation methods.

[0018] See Figure 1 The figure is a schematic diagram of an aircraft fuel thermal management system in related technologies.

[0019] Figure 1In the aircraft fuel thermal management system shown, fuel in the fuel tank passes sequentially through the aircraft thermal management main circuit and the engine thermal management main circuit to cool various subsystems and the engine within the aircraft. A portion of the fuel used for cooling flows to the combustion chamber for combustion, while the remainder flows back to the fuel tank. This results in a significant temperature difference between the fuel flowing into the combustion chamber and its coking temperature, leading to wasted fuel heat sinks. Furthermore, the overall increase in fuel temperature and low fuel heat dissipation efficiency cause a rapid rise in fuel tank temperature, significantly reducing the aircraft's flight time under thermal safety conditions and impacting its safety performance.

[0020] In order to improve the utilization rate of fuel heat sink and slow down the rise in fuel tank temperature, this application provides a fuel thermal management system.

[0021] See Figure 2 The figure is a schematic diagram of an aircraft fuel thermal management system provided in an embodiment of this application.

[0022] Figure 2 The aircraft fuel thermal management system provided in the illustrated embodiment includes: an aircraft oil return branch 101, an engine oil return branch 102, and a cascade refrigeration system 30.

[0023] The input end of the aircraft oil return branch 101 is connected to the output end of the aircraft thermal management main 201, the input end of the engine oil return branch 102 is connected to the output end of the engine thermal management main 202, and the output end of the aircraft oil return branch 101 is connected to the output end of the engine oil return branch 102.

[0024] The cascade refrigeration system 30 includes a low-temperature refrigeration circuit 301, a high-temperature refrigeration circuit 302, and an intermediate circulation circuit 303. The first input terminal of the low-temperature refrigeration circuit 301 is connected to the common terminal of the aircraft fuel return branch 101 and the engine fuel return branch 102, and the first output terminal of the low-temperature refrigeration circuit 301 is connected to the input terminal of the fuel return main 203. The first input terminal of the high-temperature refrigeration circuit 302 is connected to the input terminal of the engine fuel return branch 102, and the first output terminal of the high-temperature refrigeration circuit 302 is connected to the input terminal of the combustion chamber 17. The first input terminal of the intermediate circulation circuit 303 is connected to the second output terminal of the low-temperature refrigeration circuit 301, the first output terminal of the intermediate circulation circuit 303 is connected to the second input terminal of the low-temperature refrigeration circuit 301, the second input terminal of the intermediate circulation circuit 303 is connected to the second output terminal of the high-temperature refrigeration circuit 302, and the second output terminal of the intermediate circulation circuit 303 is connected to the second input terminal of the high-temperature refrigeration circuit 302.

[0025] Part of the fuel flowing through the aircraft thermal management main 201 flows directly into the aircraft return fuel branch 101, while the other part flows into the engine thermal management main 202. Part of the fuel flowing into the engine thermal management main 202 flows into the engine return fuel branch 102. After the aircraft return fuel branch 101 and the engine return fuel branch 102 merge, the fuel flows into the cryogenic cooling circuit 301, while the other part flows into the combustion chamber 17 via the high-temperature cooling circuit 302. The cryogenic cooling circuit 301 and the high-temperature cooling circuit 302 exchange heat through the intermediate circulation circuit 303. The cryogenic cooling circuit 301 removes heat from the fuel in the aircraft return fuel branch 101 and the engine return fuel branch 102 and transfers the heat to the high-temperature cooling circuit 302. This results in a lower fuel temperature flowing into the fuel return main 203 and a further increase in the fuel temperature flowing into the combustion chamber 17, thus ensuring both effective utilization of the fuel heat sink in the combustion chamber 17 and effective cooling of the returned fuel.

[0026] The embodiments of this application do not specifically limit the structure of the aircraft thermal management main 201, the engine thermal management main 202, and the fuel return main 203.

[0027] See also Figure 2 In one possible implementation, the aircraft thermal management bus 201 includes a numerical control system 12, an environmental control system 13, a booster fuel pump 14, and a hydraulic system 15. The input end of the numerical control system 12 is used to connect to the fuel tank 11, and the output end of the numerical control system 12 is connected to the input end of the hydraulic system 15 via the environmental control system 13 and the booster fuel pump 14 in sequence. The output end of the hydraulic system 15 is used to connect to the input end of the aircraft return fuel branch 101.

[0028] The engine thermal management main circuit 202 includes a main fuel pump 16 and a fuel / oil heat exchanger 23. The output end of the hydraulic system 15 is connected to the input end of the fuel / oil heat exchanger 23 via the main fuel pump 16. The output end of the fuel / oil heat exchanger 23 is connected to the input end of the engine return oil branch circuit 102. The fuel / oil heat exchanger 23 is used to cool the lubricating oil in the engine using the fuel in the engine thermal management main circuit 202.

[0029] The fuel return bus 203 includes a fuel / air heat exchanger 18. The input end of the fuel / air heat exchanger 18 is used to connect to the first output end of the low-temperature refrigeration circuit 301, and the output end of the fuel / air heat exchanger 18 is used to connect to the fuel tank 11.

[0030] The aircraft fuel thermal management system provided in this application embodiment achieves fuel diversion through the aircraft fuel return branch and the engine fuel return branch, which can effectively increase the temperature of the fuel flowing into the engine thermal management main circuit; the cascade refrigeration system can transfer the fuel heat in the aircraft fuel return branch and the engine fuel return branch to the fuel in the combustion chamber, which can reduce the temperature of the returned fuel and increase the temperature of the fuel flowing into the combustion chamber. The heat load is consumed by the combustion of the fuel in the combustion chamber, thereby realizing the phase change precooling of the returned fuel, adjusting the heat load distribution in the aircraft fuel thermal management system, and effectively improving the heat sink utilization rate of the fuel.

[0031] This application does not specifically limit the specific structures of the low-temperature refrigeration circuit, the high-temperature refrigeration circuit, and the intermediate circulation circuit. In one possible implementation, the cascade refrigeration system 30 provided in this application includes a low-temperature refrigeration circuit 301 comprising a first expansion valve, a first evaporator heat exchanger, and a first compressor; a high-temperature refrigeration circuit 302 comprising a first condenser heat exchanger, a second expansion valve, and a second compressor; and an intermediate circulation circuit 303 comprising a second evaporator heat exchanger, a circulation pump, and a second condenser heat exchanger.

[0032] See Figure 3 The figure is a schematic diagram of the cascade refrigeration system provided in an embodiment of this application.

[0033] The first end of the first evaporator heat exchanger 38 is connected to the first end of the second condenser heat exchanger 36 via the first compressor 39, and the second end of the second condenser heat exchanger 36 is connected to the second end of the first evaporator heat exchanger 38 via the first expansion valve 37; the first end of the first condenser heat exchanger 31 is connected to the first end of the second evaporator heat exchanger 33 via the second expansion valve 32, and the second end of the second evaporator heat exchanger 33 is connected to the second end of the first condenser heat exchanger 31 via the second compressor 34; the third end of the second evaporator heat exchanger 33 is connected to the third end of the second condenser heat exchanger 36, and the fourth end of the second condenser heat exchanger 36 is connected to the fourth end of the second evaporator heat exchanger 33 via the circulating pump 35.

[0034] This application embodiment does not specifically limit the working medium of the cryogenic refrigeration circuit, the high-temperature refrigeration circuit, and the intermediate circulation circuit. In one possible implementation, the medium of the cryogenic refrigeration circuit 301 is pentafluoropropane (R245fa), the medium of the high-temperature refrigeration circuit 302 is methanol, and the medium of the intermediate circulation circuit 303 is polyalphaolefin (PAO). Specifically, since R245fa has a critical temperature of 427.2 K and a critical pressure of 3.65 MPa, and a phase change temperature of 318.7 to 381.0 K at 0.3 to 1.5 MPa, it has advantages such as moderate critical temperature and good intermediate temperature matching, which can meet the working temperature range for secondary evaporative cooling of the fuel return main circuit 203. Therefore, the working medium of the cryogenic refrigeration circuit 301 provided in this application embodiment can be R245fa.

[0035] Since methanol has a critical temperature of 512.6 K and a critical pressure of 8.09 MPa, and a phase change temperature of 356.0~429.0 K at 0.2~1.6 MPa, it has advantages such as high critical temperature and high latent heat of phase change. Therefore, the working medium of the high-temperature refrigeration circuit 302 provided in this application embodiment can be methanol, which can apply the additional heat load generated by the fuel return circuit 203 and the first compressor 39 to the fuel flowing into the combustion chamber 17 through condensation heat exchange, and then consume it through the combustion of the fuel in the combustion chamber 17.

[0036] Since PAO has a low temperature limit of approximately 233 K and a high temperature limit of approximately 473 K, it has advantages such as a wide operating temperature range and stable physicochemical properties. It can work stably within the condensation and evaporation temperature ranges of the low temperature refrigeration circuit 301 and the high temperature refrigeration circuit 302, ensuring efficient and stable heat transfer. Therefore, the working medium of the intermediate circulation circuit 303 can be PAO.

[0037] The following is combined Figure 3 The working principle of the cascade refrigeration system 30 will be further explained.

[0038] For the cryogenic refrigeration circuit 301, R245fa flows in the cryogenic refrigeration circuit 301. The low-temperature and low-pressure gaseous R245fa is compressed and heated by the first compressor 39. Then, the high-temperature and high-pressure gaseous R245fa exchanges heat with the intermediate medium PAO and condenses into liquid R245fa. It then expands and cools down through the first expansion valve 37. Finally, the low-temperature and low-pressure liquid R245fa evaporates and cools the return fuel to complete the cycle.

[0039] For the high-temperature refrigeration circuit 302, methanol flows in the high-temperature refrigeration circuit 302. The low-temperature and low-pressure gaseous methanol is compressed and heated by the second compressor 34. Then, the high-temperature and high-pressure gaseous R245fa transfers heat to the fuel flowing into the combustion chamber 17 and condenses into liquid R245fa. It then expands and cools down through the second expansion valve 32. Finally, the low-temperature and low-pressure liquid R245fa evaporates and exchanges heat with the intermediate medium PAO to complete the cycle.

[0040] In the intermediate circulation loop 303, PAO flows through it, absorbing heat from gaseous R245fa via the second condenser heat exchanger 36 (using R245fa as the working medium), and then transferring the heat to liquid methanol via the second evaporator heat exchanger 33 (using methanol as the working medium), completing the heat coupling exchange cycle. The intermediate circulation loop 303 allows the high-temperature refrigeration loop 302 and the low-temperature refrigeration loop 301 to operate independently at their respective optimal pressures and temperatures, without interference between them, thus providing high flexibility in operation control. The intermediate circulation loop 303 is suitable for rapidly and stably adjusting the operating parameters of the cascade refrigeration system 30 in flight conditions with large temperature differences between the hot and cold ends.

[0041] In one possible implementation, the intermediate circulation loop 303 can also be achieved through an evaporator-condenser heat exchanger, which will not be described in detail here.

[0042] This application also does not specifically limit the types of the first evaporative heat exchanger, the second evaporative heat exchanger, the first condensing heat exchanger, and the second condensing heat exchanger. In one possible implementation, the first evaporative heat exchanger 38, the second evaporative heat exchanger 33, the first condensing heat exchanger 31, and the second condensing heat exchanger 36 are all shell-and-tube heat exchangers. The tube side can be a two-phase medium such as R245fa or methanol, and the shell side can be a single-phase liquid medium such as fuel oil or PAO. For example, the tube side medium of the first evaporative heat exchanger 38 is R245fa, and the shell side medium is fuel oil; the tube side medium of the second condensing heat exchanger 36 is R245fa, and the shell side medium is PAO; the tube side medium of the first condensing heat exchanger 31 is methanol, and the shell side medium is fuel oil; and the tube side medium of the second evaporative heat exchanger 33 is methanol, and the shell side medium is PAO.

[0043] Shell-and-tube heat exchangers offer advantages such as robust structure, high pressure resistance, and ease of maintenance and cleaning, making them suitable for cascade refrigeration systems involving phase change and certain pressure conditions. Arranging the two-phase media on the tube side is primarily based on the need for two-phase flow control and enhanced heat transfer. The confined space and defined flow direction within the tubes help maintain stable flow patterns during evaporation or condensation, preventing localized heat transfer deterioration due to uneven distribution in the large shell-side space. Simultaneously, higher flow velocities can be easily achieved on the tube side, enhancing convective heat transfer and reducing two-phase media stagnation. Furthermore, the high pressure requirements on the two-phase media side necessitate placing it on the stronger, easier-to-seal tube side, which aligns better with safety design principles. The large flow cross-section and low pressure drop on the shell side make it more suitable for arranging single-phase liquid media with high viscosity or large flow rates. Baffles can be used to effectively improve the turbulence and heat transfer coefficient of the single-phase media, thereby optimizing pressure loss and heat transfer efficiency.

[0044] The aircraft fuel thermal management system provided in this application includes a cascade refrigeration system comprising a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The cryogenic refrigeration circuit pre-cools the fuel return path through a phase change process; the intermediate circulation circuit ensures efficient and stable heat transfer between the cryogenic and high-temperature refrigeration circuits; and the high-temperature refrigeration circuit applies the additional heat load generated by the fuel return path and the first compressor to the fuel flowing into the combustion chamber through condensation heat exchange, which is then consumed by the combustion of the fuel in the combustion chamber, thereby achieving the effect of reducing the temperature of the return fuel and increasing the temperature of the fuel in the combustion chamber.

[0045] In one possible implementation, the aircraft fuel thermal management system provided in this application embodiment further includes a controller. The controller is configured to adjust the fuel temperature based on limits. and lubricating oil temperature limit Obtain the first operating parameters based on the superheat of the condensate outlet of the working medium. Superheat at the evaporation outlet of the working medium and fuel heat sink utilization rate Obtain the second operating parameters; control the aircraft oil return branch 101 and the engine oil return branch 102 to operate under the first operating parameters, and control the cascade refrigeration system 30 to operate under the second operating parameters.

[0046] The embodiments of this application do not specifically limit the implementation method of the controller. The controller can be an independent dedicated controller or integrated into the environmental control system or numerical control system. The controller only needs to be able to realize the aircraft fuel thermal management function.

[0047] Specifically, the controller needs to ensure that the aircraft fuel return branch 101 and the engine fuel return branch 102 meet thermal safety requirements, that is, to ensure that the temperature of the fuel entering the combustion chamber 17 is within acceptable limits. Below the fuel temperature limit (Fuel temperature limit) That is, the coking temperature of the fuel oil, and the temperature of the lubricating oil flowing out of the fuel oil / lubricating oil heat exchanger 23. Below the lubricating oil temperature limit That is, satisfying , The controller needs to ensure that the cascade refrigeration system 30 meets the thermal safety and operational efficiency targets, that is, to ensure that the methanol condensation temperature is within acceptable limits. The temperature of methanol flowing out from the first condenser heat exchanger 31 Superheat at the condensate outlet of the working medium Between ; Evaporation temperature of methanol The temperature of methanol flowing out from the second evaporator heat exchanger 33 superheat at the evaporation outlet of the working medium Between ; Condensation temperature of R245fa The temperature of R245fa flowing out of the second condenser heat exchanger 36 and the superheat of the working medium at the condenser outlet. Between ; Evaporation temperature of R245fa The superheat from the evaporation outlet of the first evaporator heat exchanger 38 to the working medium Between Fuel heat sink utilization rate satisfy .

[0048] Among them, the heat sink utilization rate of fuel The calculation method is as shown in equation (1): (1) In equation (1), This represents the temperature of the fuel flowing from fuel tank 11. This represents the temperature of the fuel entering combustion chamber 17.

[0049] The aircraft fuel thermal management system provided in this application embodiment also includes a controller. The controller is used to obtain the operating parameters of the aircraft oil return branch, the engine oil return branch, and the cascade refrigeration system based on constraints such as fuel temperature limit, lubricating oil temperature limit, superheat of the condensation outlet of the working medium, superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel, so as to enable the aircraft fuel thermal management system to achieve normal, safe and stable operation.

[0050] One possible implementation, the controller for obtaining the first operating parameter and the second operating parameter includes: the controller for obtaining the mass flow rate of fuel flowing into the aircraft return fuel branch and the mass flow rate of fuel flowing into the engine return fuel branch through the energy conservation equation and the mass conservation equation; and obtaining the condensation pressure of the working medium, the evaporation pressure of the working medium, the circulation flow rate of the working medium, and the maximum circulation temperature through the thermodynamic state equation and the energy conservation equation.

[0051] The condensation pressure of the working medium includes the condensation pressure of methanol and the condensation pressure of R245fa; the evaporation pressure of the working medium includes the evaporation pressure of methanol and the evaporation pressure of R245fa; the circulation flow rate of the working medium includes the mass flow rate of methanol in the high-temperature refrigeration circuit 302, the mass flow rate of PAO in the intermediate circulation circuit 202, and the mass flow rate of R245fa in the low-temperature refrigeration circuit 301.

[0052] According to the law of conservation of energy, the engine lubrication system in an aircraft must satisfy the following equation (2): (2) In equation (2), Represents the mass flow rate of lubricating oil in the lubrication system; This represents the heat transfer power of the fuel / oil heat exchanger 23. The total thermal load of the engine lubrication system; This represents the temperature of the lubricating oil flowing out of the fuel / oil heat exchanger 23. The corresponding enthalpy value, This represents the temperature of the lubricating oil flowing out of the oil pan. The corresponding enthalpy value, This represents the temperature of the lubricating oil returning to the oil pan. The corresponding enthalpy value.

[0053] According to the mass conservation equation, the aircraft oil return branch 101 and the engine oil return branch 102 must satisfy the following equation (3): (3) In equation (3), This represents the mass flow rate of fuel extracted by the booster fuel pump. This represents the mass flow rate of fuel pumped out by the main fuel pump. This represents the mass flow rate of fuel entering the aircraft's return fuel line. This represents the mass flow rate of fuel pumped out by the main fuel pump. This represents the mass flow rate of fuel entering the engine's return oil circuit. This represents the mass flow rate of fuel entering the combustion chamber. This represents the mass flow rate of fuel entering the fuel return bus.

[0054] According to the energy conservation equation, the aircraft oil return branch 101 and the engine oil return branch 102 must satisfy the following equation (4): (4) In equation (4), Represents the total thermal load of all aircraft subsystems. This represents the heat transfer power of the first condensing heat exchanger 31. This is the heat transfer power of the first evaporator heat exchanger 38. Represents the heat transfer power of the fuel / air heat exchanger 18; This represents the temperature of the fuel flowing out of the hydraulic system 15. The corresponding enthalpy value, This represents the temperature of the fuel flowing out of fuel tank 11. The corresponding enthalpy value, This represents the temperature of the fuel flowing out of the fuel / oil heat exchanger 23. The corresponding enthalpy value, This represents the temperature of the fuel entering combustion chamber 17. The corresponding enthalpy value, This represents the temperature of the fuel entering the fuel / air heat exchanger 18. The corresponding enthalpy value, This represents the temperature of the fuel entering the first evaporator heat exchanger 38. The corresponding enthalpy value, This represents the temperature of the fuel returning to fuel tank 11. The corresponding enthalpy value.

[0055] According to the energy conservation equation, the cascade refrigeration system 30 needs to satisfy the following equation (5): (5) In equation (5), This represents the mass flow rate of methanol in the high-temperature refrigeration circuit 302. This represents the mass flow rate of PAO in the intermediate circulation loop 303. This represents the mass flow rate of R245fa in the cryogenic refrigeration circuit 301; This represents the temperature of the methanol flowing out from the first condenser heat exchanger 31. and the condensation pressure of methanol The corresponding enthalpy value, This represents the temperature of the methanol entering the first condenser heat exchanger 31. and the condensation pressure of methanol The corresponding enthalpy value, This represents the temperature of the methanol entering the second evaporator heat exchanger 33. And the evaporation pressure of methanol The corresponding enthalpy value, This represents the temperature of the methanol flowing out from the second evaporator heat exchanger 33. and the condensation pressure of methanol The corresponding enthalpy value, This represents the temperature of R245fa flowing out from the second condenser heat exchanger 36. Condensation pressure of R245fa The corresponding enthalpy value, This represents the temperature of R245fa entering the second condenser heat exchanger 36. Condensation pressure of R245fa The corresponding enthalpy value, This represents the temperature of R245fa entering the first evaporator heat exchanger 38. Evaporation pressure of R245fa The corresponding enthalpy value, This represents the temperature of R245fa flowing out from the first evaporator heat exchanger 38. Evaporation pressure of R245fa The corresponding enthalpy value; The temperature of PAO entering the second condenser heat exchanger 36 represents The corresponding enthalpy value, This represents the temperature of PAO flowing out from the second condenser heat exchanger 36. The corresponding enthalpy value; This represents the heat transfer power of the second evaporative heat exchanger 33. This represents the heat transfer power of the second condenser heat exchanger 36.

[0056] According to the thermodynamic equation of state, the cascade refrigeration system 30 needs to satisfy the following equation (6): (6) In equation (6), and These are the adiabatic indices of methanol and R245fa, respectively.

[0057] The highest temperature of PAO in the intermediate circulation loop 303, that is, the temperature of PAO flowing out of the second condenser heat exchanger 36. Satisfy the following equation (7): (7) Heat transfer power of each heat exchanger in the aircraft fuel thermal management system The calculation method is as shown in equation (8): (8) In equation (8), For heat exchanger efficiency, This represents the maximum heat transfer power of the heat exchanger under the limitation of heat transfer temperature difference.

[0058] The transient calculation method for the mass and energy of fuel tank 11 and lubricating oil tank is as shown in equation (9): (9) In equation (9), and These are the masses of fuel tank 11 and lubricating oil tank, respectively. For the current time, This is the time step for transient calculations.

[0059] In one possible implementation, the flight operating parameters of the aircraft fuel thermal management system are shown in Table 1.

[0060] Table 1 Flight operating parameters of the aircraft fuel thermal management system

[0061] Table 1 includes durations. Mass flow rate of fuel entering the combustion chamber Total thermal load of all aircraft subsystems Thermal load of engine lubrication system And the temperature of the ram air flowing in from the external environment. For the initial state of the aircraft's fuel thermal management system, the initial temperature and initial mass of fuel tank 11 are set to 288 K and 1500 kg, respectively, and the initial temperature and initial mass of lubricating oil tank are set to 423 K and 20 kg, respectively. Furthermore, some operating parameters of the thermal management system are set to fixed values ​​under all flight conditions; specifically, the mass flow rate of fuel extracted by booster fuel pump 14... The mass flow rate of lubricating oil in the lubricating oil system is 1.5 kg / s. The mass flow rate of PAO in the intermediate circulation loop 303 is 0.732 kg / s. It is 1.0 kg / s.

[0062] In this embodiment of the application, the thermal safety and operational efficiency indicators of the aircraft fuel thermal management system are defined as follows: fuel temperature limit in five flight conditions: ground, takeoff, accelerated cruise, cruise, and landing. All are set to 421 K, the maximum lubricating oil temperature. The K values ​​are set to 447.6 K, 350.0 K, 369.1 K, 369.1 K, and 415.4 K respectively; the subcooling of the working medium at the condensation outlet is [value missing] in all flight conditions. and evaporator outlet superheat All are set to 2.5 K, fuel heat sink utilization rate All are set to 1. In addition, for the efficiency of each heat exchanger, the efficiency of fuel / air heat exchanger 18 is set to 0.55, the efficiency of fuel / lubricating oil heat exchanger 23 is set to 0.75, and the efficiency of the first evaporative heat exchanger 38, the second evaporative heat exchanger 33, the first condensing heat exchanger 31 and the second condensing heat exchanger 36 are all set to 0.95.

[0063] Transient simulation calculations of the aircraft's fuel thermal management system were conducted based on the aforementioned flight operating parameters, thermal safety indicators, and operational efficiency indicators. The cascade cooling system 30 was activated only during acceleration cruise and cruise to ensure its efficient operation, with the temperature of the fuel tank 11 as the baseline. Exceeding 333 K is used as the standard for ending thermally safe flight, and the operating parameters and performance parameters of the aircraft's fuel thermal management system can be obtained.

[0064] See Figure 4 The figure is a schematic diagram of the operating parameters of an aircraft fuel thermal management system provided in an embodiment of this application.

[0065] in, Figure 4 (a) shows some flow operation parameters of the aircraft's fuel thermal management system, with the horizontal axis... Represents time, in seconds (s); vertical axis This represents mass flow rate, measured in kilograms per second (kg / s). Figure 4 (b) shows some pressure operating parameters of the aircraft's fuel thermal management system, with the horizontal axis... t Represents time, in seconds (s); vertical axis This represents pressure, measured in megapascals (MPa). The flow rate parameter refers to the mass flow rate of fuel entering the engine return oil branch 102. Mass flow rate of methanol in high-temperature refrigeration circuit 302 The mass flow rate of R245fa in the cryogenic refrigeration circuit 301 The pressure operating parameter is the condensation pressure of methanol. Evaporation pressure of methanol Condensing pressure of R245fa Evaporation pressure of R245fa .

[0066] See Figure 5 The figure is a schematic diagram of the performance parameters of an aircraft fuel thermal management system provided in an embodiment of this application.

[0067] Figure 5 The performance parameter variations of the aircraft fuel thermal management system shown include the Coefficient of Performance (COP) of the cascade refrigeration system and the heat transfer power of the first evaporator heat exchanger 38. and fuel heat sink utilization rate .in, Figure 5 (a) Horizontal axis The left and right vertical axes represent time, while the right and left vertical axes represent the energy efficiency ratio of the cascade refrigeration system 30 and the heat transfer power of the first evaporator heat exchanger 38, respectively. , The unit is kilowatt (kW). Figure 5 (b) shows the heat sink utilization rate of fuel in a conventional aircraft fuel thermal management system and the aircraft fuel thermal management system provided in the embodiments of this application. The comparison chart, horizontal axis The vertical axes represent time, and the left and right axes represent fuel tank temperatures, respectively. and fuel heat sink utilization rate .

[0068] The parameter statistics of the aircraft fuel thermal management system are shown in Table 2.

[0069] Table 2 Parameter Statistics of Aircraft Fuel Thermal Management System

[0070] As shown in Table 2, the operating pressure ratio of the working medium compressor is reasonable, and the average COP of the cascade refrigeration system 30 is 2.32, which can provide an average heat dissipation power of 23.0 kW for the return fuel. Therefore, the embodiments of this application demonstrate high feasibility and significant effectiveness in improving the thermal safety performance of the aircraft fuel thermal management system.

[0071] Furthermore, a performance comparison of the conventional and the aircraft fuel thermal management systems provided in this embodiment of the invention is shown in Table 3.

[0072] Table 3 Performance Comparison of Aircraft Fuel Thermal Management Systems

[0073] By utilizing the aircraft fuel return branch 101, the engine fuel return branch 102, and the cascade cooling system 30, the average fuel heat sink utilization rate of this embodiment is 0.94, close to the target value of 1, representing a 2.6-fold improvement compared to traditional thermal management systems. The thermally safe flight time of this embodiment is 4757 seconds, a 37.9% improvement compared to traditional thermal management systems. Therefore, this embodiment demonstrates a significant effect in improving the thermal durability performance of the aircraft's fuel thermal management system. Improving the fuel heat sink utilization rate enhances the overall waste heat load capacity of the aircraft, improves engine combustion efficiency, reduces reliance on ram air-assisted cooling, and enhances the reliability and economy of the aircraft's fuel thermal management system.

[0074] In one possible implementation, in the aircraft fuel thermal management system provided in this application embodiment, the controller is used to control the aircraft fuel return branch 101 and the engine fuel return branch 102 to operate under first operating parameters, and to control the cascade refrigeration system 303 to operate under second operating parameters, including: The controller is used to control the aircraft oil return branch 101 and the engine oil return branch 102 to operate under the first operating parameters according to the proportional-integral-derivative (PID) algorithm, and to control the cascade refrigeration system 30 to operate under the second operating parameters.

[0075] The aircraft fuel thermal management system provided in this application uses a PID algorithm for controller control, which can quickly track set values ​​and eliminate steady-state errors. It has the advantages of simple control structure, convenient parameter tuning, strong adaptability, and high reliability, thereby ensuring the stable operation of the aircraft fuel return branch 101, engine fuel return branch 102 and cascade refrigeration system 30, and thus ensuring the stable operation of the aircraft fuel thermal management system.

[0076] Based on the aircraft fuel thermal management system provided in the above embodiments, this application also provides a control method for the aircraft fuel thermal management system. The aircraft fuel thermal management system includes: an aircraft fuel return branch, an engine fuel return branch, and a cascade refrigeration system. The input end of the aircraft fuel return branch is connected to the output end of the aircraft thermal management main circuit; the input end of the engine fuel return branch is connected to the output end of the engine thermal management main circuit; and the output end of the aircraft fuel return branch is connected to the output end of the engine fuel return branch. The cascade refrigeration system includes a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The first input end of the cryogenic refrigeration circuit is connected to the common end of the aircraft fuel return branch and the engine fuel return branch; the first output end of the cryogenic refrigeration circuit is used to connect to the input end of the fuel return main circuit. The first input end of the high-temperature refrigeration circuit is used to connect to the input end of the engine fuel return branch; and the first output end of the high-temperature refrigeration circuit is used to connect to the input end of the combustion chamber. The first input end of the intermediate circulation circuit is connected to the second output end of the cryogenic refrigeration circuit; the first output end of the intermediate circulation circuit is connected to the second input end of the cryogenic refrigeration circuit; the second input end of the intermediate circulation circuit is connected to the second output end of the high-temperature refrigeration circuit; and the second output end of the intermediate circulation circuit is connected to the second input end of the high-temperature refrigeration circuit.

[0077] See Figure 6 The figure is a flowchart of a control method for an aircraft fuel thermal management system provided in an embodiment of this application.

[0078] The control method includes: S601: The first operating parameter is obtained based on the fuel temperature limit and the lubricating oil temperature limit, and the second operating parameter is obtained based on the superheat of the condensate outlet of the working medium, the superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel.

[0079] For example, the controller can obtain the first operating parameter based on the fuel temperature limit and the lubricating oil temperature limit, and obtain the second operating parameter based on the superheat of the condensate outlet of the working medium, the superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel.

[0080] S602: Controls the aircraft oil return branch and engine oil return branch to operate under the first operating parameters, and controls the cascade refrigeration system to operate under the second operating parameters.

[0081] For example, the controller can control the aircraft oil return branch and the engine oil return branch to operate under the first operating parameters, and control the cascade refrigeration system to operate under the second operating parameters.

[0082] The control method for the aircraft fuel thermal management system provided in this application achieves fuel diversion through the aircraft fuel return branch and the engine fuel return branch, which can effectively increase the temperature of the fuel flowing into the engine thermal management main circuit. The cascade refrigeration system can transfer the heat of the fuel in the aircraft fuel return branch and the engine fuel return branch to the fuel in the combustion chamber. By controlling the operating parameters of the aircraft fuel return branch, the engine fuel return branch, and the cascade refrigeration system, the temperature of the recirculated fuel can be reduced and the temperature of the fuel flowing into the combustion chamber can be increased. The heat load is consumed by the combustion of the fuel in the combustion chamber, thereby achieving phase change precooling of the recirculated fuel, adjusting the heat load distribution in the aircraft fuel thermal management system, and effectively improving the heat sink utilization rate of the fuel.

[0083] One possible implementation involves obtaining the first operating parameter and the second operating parameter, including: The mass flow rates of fuel flowing into the aircraft return fuel branch and the engine return fuel branch are obtained through the energy balance equation and the mass conservation equation; the condensation pressure, evaporation pressure, circulation flow rate, and maximum circulation temperature of the working medium are obtained through the thermodynamic state equation and the heat balance equation.

[0084] One possible implementation involves controlling the aircraft oil return branch and the engine oil return branch to operate under a first operating parameter, and controlling the cascade refrigeration system to operate under a second operating parameter, including: The dual-recirculation fuel system is controlled to operate under the first operating parameters based on the proportional-integral-derivative algorithm, while the cascade refrigeration system is controlled to operate under the second operating parameters.

[0085] Based on the aircraft fuel thermal management system provided in the above embodiments, this application also provides an aircraft. The aircraft provided in this application includes any of the aircraft fuel thermal management systems provided in the above embodiments, and further includes: Aircraft thermal management main circuit, engine thermal management main circuit, fuel return main circuit, fuel tank and combustion chamber.

[0086] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0087] The above description of the disclosed embodiments enables those skilled in the art to make or use this application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An aircraft fuel thermal management system, characterized in that, include: Aircraft oil return branch, engine oil return branch, and cascade refrigeration system; The input end of the aircraft oil return branch is connected to the output end of the aircraft thermal management main circuit, the input end of the engine oil return branch is connected to the output end of the engine thermal management main circuit, and the output end of the aircraft oil return branch is connected to the output end of the engine oil return branch. The cascade refrigeration system includes a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The first input terminal of the cryogenic refrigeration circuit is connected to the common terminal of the aircraft fuel return branch and the engine fuel return branch. The first output terminal of the cryogenic refrigeration circuit is connected to the input terminal of the fuel return main circuit. The first input terminal of the high-temperature refrigeration circuit is connected to the input terminal of the engine fuel return branch. The first output terminal of the high-temperature refrigeration circuit is connected to the input terminal of the combustion chamber. The first input terminal of the intermediate circulation circuit is connected to the second output terminal of the cryogenic refrigeration circuit, and the first output terminal of the intermediate circulation circuit is connected to the second input terminal of the cryogenic refrigeration circuit. The second input terminal of the intermediate circulation circuit is connected to the second output terminal of the high-temperature refrigeration circuit, and the second output terminal of the intermediate circulation circuit is connected to the second input terminal of the high-temperature refrigeration circuit.

2. The system according to claim 1, characterized in that, The low-temperature refrigeration circuit includes a first expansion valve, a first evaporator heat exchanger, and a first compressor; the high-temperature refrigeration circuit includes a first condenser heat exchanger, a second expansion valve, and a second compressor; and the intermediate circulation circuit includes a second evaporator heat exchanger, a circulation pump, and a second condenser heat exchanger. The first end of the first evaporative heat exchanger is connected to the first end of the second condensing heat exchanger via the first compressor, and the second end of the second condensing heat exchanger is connected to the second end of the first evaporative heat exchanger via the first expansion valve; the first end of the first condensing heat exchanger is connected to the first end of the second evaporative heat exchanger via the second expansion valve, and the second end of the second evaporative heat exchanger is connected to the second end of the first condensing heat exchanger via the second compressor; the third end of the second evaporative heat exchanger is connected to the third end of the second condensing heat exchanger, and the fourth end of the second condensing heat exchanger is connected to the fourth end of the second evaporative heat exchanger via the circulating pump.

3. The system according to claim 1, characterized in that, The working medium of the low-temperature refrigeration circuit is pentafluoropropane R245fa, the working medium of the high-temperature refrigeration circuit is methanol, and the working medium of the intermediate circulation circuit is polyalphaolefin (PAO).

4. The system according to claim 3, characterized in that, The aircraft thermal management main circuit includes a numerical control system, an environmental control system, a booster fuel pump, and a hydraulic system. The input end of the numerical control system is used to connect to the fuel tank. The output end of the numerical control system is connected to the input end of the hydraulic system via the environmental control system and the booster fuel pump. The output end of the hydraulic system is used to connect to the input end of the aircraft return fuel branch. The engine thermal management main circuit includes a main fuel pump and a fuel / oil heat exchanger. The output end of the hydraulic system is used to connect to the input end of the fuel / oil heat exchanger through the main fuel pump. The output end of the fuel / oil heat exchanger is used to connect to the input end of the engine return oil branch. The fuel return bus includes a fuel / air heat exchanger, the input end of which is used to connect to the first output end of the low-temperature refrigeration circuit, and the output end of which is used to connect to the fuel tank.

5. The system according to any one of claims 1 to 4, characterized in that, Also includes: Controller; The controller is used to obtain a first operating parameter based on the fuel temperature limit and the lubricating oil temperature limit, and to obtain a second operating parameter based on the superheat of the condensate outlet of the working medium, the superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel. The aircraft oil return branch and the engine oil return branch are controlled to operate under the first operating parameters, and the cascade refrigeration system is controlled to operate under the second operating parameters.

6. The system according to claim 5, characterized in that, The controller is used to obtain the first operating parameter and the second operating parameter, including: The controller is used to obtain the mass flow rate of fuel flowing into the aircraft return fuel branch and the mass flow rate of fuel flowing into the engine return fuel branch through the energy conservation equation and the mass conservation equation; and to obtain the condensation pressure, evaporation pressure, circulation flow rate and maximum circulation temperature of the working medium through the thermodynamic state equation and the energy conservation equation.

7. A control method for an aircraft fuel thermal management system, characterized in that, The system includes an aircraft oil return branch, an engine oil return branch, and a cascade refrigeration system. The input end of the aircraft oil return branch is connected to the output end of the aircraft thermal management main circuit, the input end of the engine oil return branch is connected to the output end of the engine thermal management main circuit, and the output end of the aircraft oil return branch is connected to the output end of the engine oil return branch. The control method includes: The first operating parameter is obtained based on the fuel temperature limit and the lubricating oil temperature limit. The second operating parameter is obtained based on the superheat of the condensate outlet of the working medium, the superheat of the evaporation outlet of the working medium, and the heat sink utilization rate of the fuel. The aircraft oil return branch and the engine oil return branch are controlled to operate under the first operating parameter, and the cascade refrigeration system is controlled to operate under the second operating parameter. The cascade refrigeration system includes a cryogenic refrigeration circuit, a high-temperature refrigeration circuit, and an intermediate circulation circuit. The first input terminal of the cryogenic refrigeration circuit is connected to the common terminal of the aircraft fuel return branch and the engine fuel return branch. The first output terminal of the cryogenic refrigeration circuit is connected to the input terminal of the fuel return main circuit. The first input terminal of the high-temperature refrigeration circuit is connected to the input terminal of the engine fuel return branch. The first output terminal of the high-temperature refrigeration circuit is connected to the input terminal of the combustion chamber. The first input terminal of the intermediate circulation circuit is connected to the second output terminal of the cryogenic refrigeration circuit, and the first output terminal of the intermediate circulation circuit is connected to the second input terminal of the cryogenic refrigeration circuit. The second input terminal of the intermediate circulation circuit is connected to the second output terminal of the high-temperature refrigeration circuit, and the second output terminal of the intermediate circulation circuit is connected to the second input terminal of the high-temperature refrigeration circuit.

8. The control method according to claim 7, characterized in that, The process of obtaining the first operating parameter and the second operating parameter includes: The mass flow rate of fuel flowing into the aircraft return fuel branch and the mass flow rate of fuel flowing into the engine return fuel branch are obtained through the energy balance equation and the mass conservation equation; the condensation pressure, evaporation pressure, circulation flow rate and maximum circulation temperature of the working medium are obtained through the thermodynamic state equation and the heat balance equation.

9. The control method according to claim 7, characterized in that, Controlling the aircraft oil return branch and the engine oil return branch to operate under the first operating parameters, and controlling the cascade refrigeration system to operate under the second operating parameters, includes: The proportional-integral-differential algorithm controls the aircraft oil return branch and the engine oil return branch to operate under the first operating parameters, and controls the cascade refrigeration system to operate under the second operating parameters.

10. An aircraft, characterized in that, The aircraft fuel thermal management system according to any one of claims 1 to 6 further includes: Aircraft thermal management main circuit, engine thermal management main circuit, fuel return main circuit, fuel tank and combustion chamber.

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