Waste heat recovery system and gas-electric hybrid aero-engine

Abstract

The oil-electricity hybrid aero-engine comprises a tail nozzle and an outer duct, and further comprises a motor and an electronic cooling loop, the system comprises a thermoacoustic engine and a first thermoacoustic heat pump, the thermoacoustic engine is arranged at the tail nozzle and used for absorbing heat of tail gas at the tail nozzle, and the first thermoacoustic heat pump is arranged at the tail nozzle and used for absorbing heat of the tail gas at the outer duct. Sound power is output; the first thermo-acoustic heat pump comprises a first cold-end heat exchanger, a first heat regenerator and a first hot-end heat exchanger, the first cold-end heat exchanger is used for absorbing heat to form a low-temperature area and is used for cooling the electronic cooling loop, part of heat is transmitted to the first hot-end heat exchanger through the first heat regenerator by utilizing acoustic power, and the first hot-end heat exchanger releases heat to the outer duct. The system utilizes a thermo-acoustic energy conversion technology to enhance the cooling of electronic parts, and can also recover tail gas waste heat to convert the tail gas waste heat into heat with a higher temperature level.

Description

Technical Field

[0001] This invention relates to the field of hybrid electric aircraft engines, and more specifically to the field of thermal management. Background Technology

[0002] Hybrid electric propulsion technology is one of the important ways to reduce carbon emissions in the future aviation industry. Unlike traditional aircraft engine configurations, hybrid electric propulsion systems introduce new electric drive and energy storage systems on the basis of gas turbine engines. The different operating modes of these two energy sources lead to different thermal management requirements.

[0003] The high-temperature exhaust gases produced by the core of a gas turbine engine are released into the atmosphere through the tailpipe, resulting in significant energy waste. Meanwhile, electric motors, typically in the megawatt range, generate considerable heat during operation, and inadequate cooling not only affects their efficiency. Summary of the Invention

[0004] One object of the present invention is to provide a waste heat recovery system for hybrid electric aircraft engines.

[0005] A waste heat recovery system for achieving the above objectives is used in a hybrid electric aircraft engine. The hybrid electric aircraft engine includes a tail nozzle and an outer bypass duct, as well as an electric motor and an electronic cooling circuit. The system includes a thermoacoustic engine and a first thermoacoustic heat pump. The thermoacoustic engine is located at the tail nozzle and is used to absorb the heat of the exhaust gas at the tail nozzle and output acoustic power. The first thermoacoustic heat pump includes a first cold-end heat exchanger, a first regenerator, and a first hot-end heat exchanger. The first cold-end heat exchanger is used to absorb heat to form a low-temperature zone for cooling the electronic cooling circuit, and uses the acoustic power to transfer a portion of the heat through the first regenerator to the first hot-end heat exchanger. The first hot-end heat exchanger releases heat to the outer bypass duct.

[0006] In one or more embodiments, the hybrid electric aircraft engine further includes a combustion chamber, the combustion chamber including an inlet air heat exchanger, and the system further includes a second thermoacoustic heat pump, including a second cold-end heat exchanger, a second regenerator, and a second hot-end heat exchanger. The second cold-end heat exchanger is used to absorb heat from the tail nozzle and use the acoustic power to transfer a portion of the heat to the second hot-end heat exchanger via the second regenerator. The second hot-end heat exchanger releases heat to form a high-temperature zone for supplying heat to the inlet air heat exchanger.

[0007] In one or more embodiments, the thermoacoustic engine includes a third hot-end heat exchanger, a third regenerative heat pipe, a acoustic pipe, and a third cold-end heat exchanger. The third hot-end heat exchanger is used to absorb the heat of the exhaust gas at the tail nozzle. This heat is transferred to the third cold-end heat exchanger via the third regenerative heat pipe. The third cold-end heat exchanger is used to transfer the heat to the outer bypass duct. The third regenerative heat pipe is also used to convert this heat into acoustic power.

[0008] In one or more embodiments, the first thermoacoustic heat pump is a thermoacoustic refrigerator.

[0009] In one or more embodiments, the electronic cooling circuit includes an oil cooling circuit, and the low-temperature zone is used to cool the oil cooling circuit.

[0010] In one or more embodiments, the lubricating oil cooling circuit includes a lubricating oil heat exchanger, and the low-temperature zone is used to cool the lubricating oil heat exchanger.

[0011] Another object of the present invention is to provide a hybrid electric aircraft engine including the above-mentioned waste heat recovery system.

[0012] The aforementioned first thermoacoustic heat pump is a device based on thermoacoustic technology with no moving parts, resulting in high reliability. Using the first thermoacoustic heat pump, a low-temperature zone is generated through the first cold-end heat exchanger to cool the working medium in the electronic cooling circuit of the hybrid electric propulsion system, such as the lubricating oil circuit and fuel circuit, thereby reducing the temperature of the cooling medium and improving the cooling effect on the electrical components. Furthermore, the temperature of the cooling working fluid can be reduced through refrigeration, thereby reducing the size and mass of the heat exchangers for each cooling component. A second thermoacoustic heat pump can also be used to raise the exhaust gas heat to a higher temperature and deliver it to the inlet air heat exchanger, thereby preheating the combustion chamber inlet air and recovering and utilizing the exhaust gas heat, thus improving the overall energy utilization efficiency. Attached Figure Description

[0013] The above and other features, properties and advantages of the present invention will become more apparent from the following description taken in conjunction with the accompanying drawings and embodiments, wherein:

[0014] Figure 1 This is a simplified schematic diagram of an aircraft engine;

[0015] Figure 2 This is a schematic diagram of a heat pump system that recovers and utilizes waste heat from exhaust gas;

[0016] Figure 3 This is a schematic diagram of a refrigeration system that recovers and utilizes waste heat from exhaust gas. Detailed Implementation

[0017] The present invention will be further described below with reference to specific embodiments and accompanying drawings. More details are set forth in the following description in order to provide a full understanding of the present invention. However, the present invention can obviously be implemented in many other ways different from those described herein. Those skilled in the art can make similar extensions and derivations based on actual application situations without departing from the spirit of the present invention. Therefore, the scope of protection of the present invention should not be limited by the content of this specific embodiment.

[0018] It should be noted that these and other accompanying drawings are merely examples and are not drawn to scale, and should not be construed as limiting the scope of protection of the present invention.

[0019] Figure 1 The diagram shows a simplified structure of an aero-engine, including an air inlet 1, a fan 2, a booster stage 3, a compressor 4, a combustion chamber 5, a high-pressure turbine 6, a low-pressure turbine 7, a tail nozzle 8, and external components such as a core nacelle 9, a nacelle 10, and an outer bypass duct 11 nozzle.

[0020] The nacelle 10 encloses the entire engine. Airflow flows axially from left to right. Inlet 1 and fan 2 guide air into the engine; part of the air flowing through fan 2 enters the core engine for combustion, while the rest flows around the core nacelle through the bypass duct, providing most of the aircraft's thrust. The core nacelle 9 houses the core engine components; the booster stage 3 and compressor 4 further compress the air entering the core engine, pushing it to extremely high pressure to provide sufficient air and pressure for subsequent combustion. The compressed high-pressure air mixes with injected fuel in the combustion chamber 5 and ignites, producing a large amount of high-temperature, high-pressure gas. The high-pressure turbine 6 and low-pressure turbine 7 extract energy from the high-temperature, high-pressure gas to drive the compressor and fan. The bypass duct is a channel surrounding the core engine in a turbofan engine. The bypass duct nozzle 11 guides the airflow passing through the fan but not entering the core engine, thus guiding the bypass airflow. The airflow within the bypass duct, along with the core airflow, is ejected from the exhaust nozzle, generating thrust. The tail nozzle 8 is the engine's outlet section, responsible for accelerating and ejecting the high-temperature, high-pressure airflow that has passed through the engine core and / or bypass duct to generate thrust.

[0021] A hybrid electric aircraft engine is an aviation power system that combines a traditional fuel engine with electric propulsion technology. It not only provides power through fuel combustion but also utilizes electricity for auxiliary propulsion, thus reducing fuel consumption and carbon emissions. Compared to traditional engines, hybrid electric aircraft engines incorporate additional components such as an electric motor, battery system, and motor cooling circuit.

[0022] The different operating modes of the two energy sources lead to different thermal management requirements for hybrid electric aircraft engines. The high-temperature exhaust gases produced by the gas turbine engine need to be effectively cooled and dissipated, resulting in approximately 55% to 75% of the heat being lost to the atmosphere through the exhaust nozzle, causing significant energy waste. Meanwhile, the electric motor (typically in the megawatt range) generates substantial heat during operation, and its heat generation pattern differs from that of the gas turbine engine in a typical flight profile. Inadequate cooling not only affects the motor's efficiency but also poses certain safety hazards. Furthermore, as a crucial component of the hybrid electric propulsion aircraft's power system, the battery's temperature fluctuations during operation severely impact its performance, lifespan, and reliability. Additionally, if the heat generated by the battery itself during operation is not managed promptly and effectively, it may overheat, potentially leading to thermal runaway.

[0023] Therefore, although hybrid electric propulsion systems are more efficient than traditional gas turbine engines, they also face more prominent thermal management problems. High-power electronic and electrical equipment has high heat dissipation requirements and poses a great challenge to thermal management. Relying solely on traditional cooling methods such as fuel, lubricating oil, and air is insufficient to ensure the normal operation of future hybrid electric propulsion systems.

[0024] Based on this, the present invention provides a waste heat recovery system that can recover and utilize low-grade heat such as waste heat from the exhaust gas of a gas turbine engine, and cool the electronic cooling circuit, thereby improving the cooling effect of the electronic cooling circuit and improving the overall energy utilization efficiency.

[0025] Reference Figures 2-3 As shown, the waste heat recovery system includes a thermoacoustic engine 12 and a first thermoacoustic heat pump 25. Preferably, the first thermoacoustic heat pump 25 is a thermoacoustic refrigerator.

[0026] The thermoacoustic engine 12 is located at the tail nozzle 8 to absorb heat from the exhaust gas at the tail nozzle 8 and output acoustic power. The thermoacoustic engine mainly includes a third hot-end heat exchanger 13, a third regenerating pipe 14, a acoustic pipe 20, and a third cold-end heat exchanger 15. The third hot-end heat exchanger 13 absorbs heat from the tail nozzle 8, and the third cold-end heat exchanger 15 releases heat to the outer bypass duct 11, transferring the heat to the outer bypass air 22, thereby generating a temperature gradient along the axial direction in the third regenerating pipe 14, and converting part of the heat input from the third hot-end heat exchanger 13 into acoustic power 24, which is then transferred to the first thermoacoustic heat pump 25 through the acoustic pipe 20.

[0027] The third hot-end heat exchanger absorbs heat and transfers it to the working fluid, such as air or helium, generating sound waves. Preferably, the third hot-end heat exchanger employs a finned heat exchange structure or a porous media structure to increase the heat exchange area. The cold-end heat exchanger is used to dissipate heat to the outside. Preferably, the third cold-end heat exchanger can also employ a finned heat exchange structure or a porous media structure to increase the heat exchange area and improve heat dissipation efficiency.

[0028] The third regenerator 14 is located between the third hot-end heat exchanger 13 and the third cold-end heat exchanger 15, and performs reverse heat exchange during the flow of the working fluid to the hot and cold ends. Within the thermoacoustic engine regenerator, each gas particle undergoes a complete thermoacoustic dynamic cycle of compression, heat release, expansion, and heat absorption. Numerous gas particles relay heat transfer and cooperate with each other, converting the heat input from the hot-end heat exchanger into acoustic power. Heat that cannot be converted is discharged into the environment through the third cold-end heat exchanger. By utilizing thermoacoustic technology to extract part of the exhaust heat from the gas turbine engine in the hybrid electric propulsion system, and using this thermal energy to drive the thermoacoustic engine to generate acoustic power, the exhaust heat is recovered and utilized.

[0029] The first thermoacoustic heat pump 25 is a device based on the thermoacoustic effect. The thermoacoustic effect refers to the heat transfer and temperature change that occurs when sound waves propagate through porous materials or pipes. Utilizing this principle, sound energy can be converted into heat energy or cold energy, thereby realizing the function of a heat pump or refrigeration.

[0030] After a thermoacoustic engine generates high-amplitude sound waves, these waves are transmitted through specific pipes or chambers. Within the pipes, the sound waves interact with gas molecules, causing the molecules to compress and expand. This movement of the gas molecules creates a temperature gradient, resulting in a higher temperature at one end and a lower temperature at the other. This temperature gradient allows heat to be transferred from the low-temperature region to the high-temperature region.

[0031] The first thermoacoustic heat pump 25 includes a first cold-end heat exchanger 17, a first regenerator 18, and a first hot-end heat exchanger 19. The first cold-end heat exchanger 19 is used to form a low-temperature zone to cool the electronic cooling circuit, and uses acoustic power to transfer part of the heat through the first regenerator 18 to the first hot-end heat exchanger 19. The first hot-end heat exchanger 19 releases heat to the outer duct.

[0032] The electronic cooling circuit includes an oil cooling circuit, and the low-temperature zone is used to cool the oil heat exchanger of the oil cooling circuit.

[0033] exist Figure 3In the illustrated embodiment, the third hot-end heat exchanger 13 absorbs heat from the tail nozzle 8, and the third cold-end heat exchanger 15 releases heat to the outer bypass duct 11, transferring the heat to the outer bypass air 22. This generates a temperature gradient along the axial direction within the third regenerator 14 and converts a portion of the heat input from the third hot-end heat exchanger 13 into acoustic work, which is then transmitted through the acoustic tube 20 to the first thermoacoustic heat pump 25, which functions as a thermoacoustic refrigerator. The first hot-end heat exchanger 19 releases heat to the outer bypass duct 11, transferring the heat to the outer bypass air 22. Under the action of the acoustic work 24 transmitted through the acoustic tube 20, a low-temperature zone is formed in the first cold-end heat exchanger 17, and heat is absorbed from the lubricating oil heat exchanger 28 in the lubricating oil cooling circuit 26. Before being delivered to the components requiring heat dissipation and cooling by the lubricating oil pump 27, the lubricating oil in the lubricating oil cooling circuit 26 passes through the lubricating oil heat exchanger 28, which transfers heat to the first cold end heat exchanger 17 of the thermoacoustic refrigerator, thereby reducing the temperature of the lubricating oil. Then it goes to cool the battery 29, motor controller 30, motor 31, gearbox 32, bearing cavity 33, other heat sources 34 and other components that need to be cooled.

[0034] Before acting as a cooling medium, the lubricating oil is cooled by an oil heat exchanger, thereby reducing the inlet temperature of the cooling oil in each component and simplifying heat dissipation. Under the same heat dissipation requirements, the size and weight of the heat exchangers / heat dissipation devices in each component can be reduced, thus further achieving a lightweight and compact design. Simultaneously, this process does not utilize electricity or extract engine shaft power; instead, it uses exhaust waste heat as the energy source for the refrigeration unit, thereby improving overall energy efficiency.

[0035] The cooling circuit can also be just Figure 3 In the local circuit, the working medium in the cooling circuit can also be other media besides lubricating oil, such as fuel oil, ethylene glycol-water solution, PAO (polyalphaolefin) and other cooling media.

[0036] In some embodiments, the system may further include a second thermoacoustic heat pump 16, such as Figure 2 As shown. A thermoacoustic heat pump is designed to transfer heat from a low-temperature region to a high-temperature region for heating or maintaining a high temperature; a thermoacoustic refrigerator is designed to remove heat from a low-temperature region for cooling. Both are devices based on the thermoacoustic effect.

[0037] The second thermoacoustic heat pump 16 includes a second cold-end heat exchanger 17', a second regenerator 18', and a second hot-end heat exchanger 19'. The second cold-end heat exchanger 17' is used to absorb heat from the tail nozzle 8 and uses acoustic power to transfer part of the heat to the second hot-end heat exchanger 19' via the second regenerator 18'. The second hot-end heat exchanger 19' releases heat to form a high-temperature zone for supplying heat to the inlet air heat exchanger 23 in the combustion chamber 5.

[0038] In the gas turbine engine, the duct air 21 absorbs heat through the combustion chamber inlet air heat exchanger 23 before entering the combustion chamber, thus increasing its temperature before entering the combustion chamber 5 to participate in combustion. While maintaining the same combustion chamber 5 outlet temperature, fuel consumption is reduced. In this process, no electricity is used or engine shaft power is extracted; instead, exhaust waste heat is used as the energy source for the heat pump, thereby improving overall energy efficiency.

[0039] The first and second thermoacoustic heat pumps, based on thermoacoustic technology, have no moving parts, are highly reliable, reduce oil consumption and achieve efficient thermal management, reduce waste heat emissions, and minimize negative environmental impacts.

[0040] The first thermoacoustic heat pump generates a low-temperature zone through the cold-end heat exchanger of the thermoacoustic refrigerator, which cools the working medium in the electronic cooling circuits of the hybrid electric propulsion system, such as the lubricating oil circuit and the fuel circuit, thereby reducing the temperature of the cooling medium and improving the cooling effect on the electrical components. Furthermore, the refrigeration can reduce the temperature of the cooling working fluid, thereby reducing the size and weight of the heat exchangers of each cooling component. The second thermoacoustic heat pump can also be used to raise the exhaust gas heat to a higher temperature and deliver it to the inlet air heat exchanger, thereby preheating the combustion chamber inlet air and recovering and utilizing the exhaust gas heat, thus improving the overall energy utilization efficiency.

[0041] Based on the above description of the waste heat recovery system, it can also be understood that a hybrid electric aircraft engine has better thermal management.

[0042] It should be noted that the use of terms such as "first," "second," and "third" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this application.

[0043] In the description of this application, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is usually based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this application and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this application; the directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0044] Furthermore, this application uses specific terms to describe embodiments of the application. For example, "an embodiment," "one embodiment," and / or "some embodiments" refer to a particular feature, structure, or characteristic related to at least one embodiment of the application. Therefore, it should be emphasized and noted that "an embodiment," "one embodiment," or "an alternative embodiment" mentioned twice or more in different locations in this specification do not necessarily refer to the same embodiment. In addition, certain features, structures, or characteristics in one or more embodiments of the application can be appropriately combined.

[0045] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Any variations and modifications can be made by those skilled in the art without departing from the spirit and scope of the invention. Therefore, any modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention, without departing from the scope of the invention, fall within the protection scope defined by the claims of the present invention.

Claims

1. Waste heat recovery system for a hybrid-electric aircraft engine, the hybrid-electric aircraft engine comprising a tail nozzle and an outer duct, further comprising an electric machine and an electric cooling circuit, characterized in that, The system further comprises a second thermoacoustic heat pump comprising a second cold-end heat exchanger, a second regenerator and a second hot-end heat exchanger, the second cold-end heat exchanger is configured to absorb heat from the exhaust nozzle, and the second hot-end heat exchanger is configured to release heat to form a high-temperature region for supplying heat to the inlet air heat exchanger. The thermoacoustic engine comprises a third hot-end heat exchanger, a third regenerator, an acoustic tube and a third cold-end heat exchanger, the third hot-end heat exchanger is configured to absorb heat from the exhaust nozzle, the third regenerator is configured to transfer the heat to the third cold-end heat exchanger, and the third cold-end heat exchanger is configured to transfer heat to the bypass duct, and the third regenerator is further configured to convert the heat into acoustic power. The first thermoacoustic heat pump is a thermoacoustic refrigerator. The electronic cooling circuit comprises an oil cooling circuit, and the low-temperature region is configured to cool the oil cooling circuit.

2. The waste heat recovery system of claim 1, wherein, The oil cooling circuit comprises an oil heat exchanger, and the low-temperature region is configured to cool the oil heat exchanger. The system further comprises a second thermoacoustic heat pump comprising a second cold-end heat exchanger, a second regenerator and a second hot-end heat exchanger, the second cold-end heat exchanger is configured to absorb heat from the exhaust nozzle, and the second hot-end heat exchanger is configured to release heat to form a high-temperature region for supplying heat to the inlet air heat exchanger.

3. The waste heat recovery system according to claim 1 or 2, characterized in that, The thermoacoustic engine comprises a third hot-end heat exchanger, a third regenerator, an acoustic tube and a third cold-end heat exchanger, the third hot-end heat exchanger is configured to absorb heat from the exhaust nozzle, the third regenerator is configured to transfer the heat to the third cold-end heat exchanger, and the third cold-end heat exchanger is configured to transfer heat to the bypass duct, and the third regenerator is further configured to convert the heat into acoustic power.

4. The waste heat recovery system of claim 1, wherein, The first thermoacoustic heat pump is a thermoacoustic refrigerator.

5. The waste heat recovery system of claim 1, wherein, The electronic cooling circuit comprises an oil cooling circuit, and the low-temperature region is configured to cool the oil cooling circuit.

6. The waste heat recovery system of claim 5, wherein, The oil cooling circuit comprises an oil heat exchanger, and the low-temperature region is configured to cool the oil heat exchanger.

7. A hybrid-electric aircraft engine, characterized in that, The system further comprises a second thermoacoustic heat pump comprising a second cold-end heat exchanger, a second regenerator and a second hot-end heat exchanger, the second cold-end heat exchanger is configured to absorb heat from the exhaust nozzle, and the second hot-end heat exchanger is configured to release heat to form a high-temperature region for supplying heat to the inlet air heat exchanger. The thermoacoustic engine comprises a third hot-end heat exchanger, a third regenerator, an acoustic tube and a third cold-end heat exchanger, the third hot-end heat exchanger is configured to absorb heat from the exhaust nozzle, the third regenerator is configured to transfer the heat to the third cold-end heat exchanger, and the third cold-end heat exchanger is configured to transfer heat to the bypass duct, and the third regenerator is further configured to convert the heat into acoustic power. The first thermoacoustic heat pump is a thermoacoustic refrigerator. The electronic cooling circuit comprises an oil cooling circuit, and the low-temperature region is configured to cool the oil cooling circuit. The oil cooling circuit comprises an oil heat exchanger, and the low-temperature region is configured to cool the oil heat exchanger. The system further comprises a second thermoacoustic heat pump comprising a second cold-end heat exchanger, a second regenerator and a second hot-end heat exchanger, the second cold-end heat exchanger is configured to absorb heat from the exhaust nozzle, and the second hot-end heat exchanger is configured to release heat to form a high-temperature region for supplying heat to the inlet air heat exchanger. The thermoacoustic engine comprises a third hot-end heat exchanger, a third regenerator, an acoustic tube and a third cold-end heat exchanger, the third hot-end heat exchanger is configured to absorb heat from the exhaust nozzle, the third regenerator is configured to transfer the heat to the third cold-end heat exchanger, and the third cold-end heat exchanger is configured to transfer heat to the bypass duct, and the third regenerator is further configured to convert the heat into acoustic power. The first thermoacoustic heat pump is a thermoacoustic refrigerator. The electronic cooling circuit comprises an oil cooling circuit, and the low-temperature region is configured to cool the oil cooling circuit. The oil cooling circuit comprises an oil heat exchanger,

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