Combined cycle refrigeration system suitable for all-electric aircraft and method of operation thereof

Abstract

This invention discloses a combined cycle refrigeration system and its operating method suitable for all-electric aircraft, belonging to the field of environmental control for all-electric aircraft, and meeting the environmental control requirements of all-electric aircraft in many ways. The system is driven by onboard electrical power and consists of a combination of a vapor compression refrigeration cycle, an air expansion refrigeration cycle, and a liquid cooling cycle. The onboard motor drives the vapor compression refrigeration cycle to replace ram gas as the cold source, while an electric compressor compresses ambient air as the high-pressure air source required for the air expansion refrigeration cycle. The liquid cooling cycle and the air expansion refrigeration cycle are used to cool and regulate the equipment compartment and cockpit respectively. Simultaneously, the cockpit return air is mixed with ambient bleed air to participate in the air expansion refrigeration, forming a closed loop, effectively reducing the bleed air volume requirement.

Description

Technical Field

[0001] This invention belongs to the field of environmental control for all-electric aircraft, and specifically relates to a combined cycle refrigeration system suitable for all-electric aircraft and its working method. Background Technology

[0002] All-electric aircraft represent a trend in modern aircraft development, aiming to achieve centralized control of aircraft energy, overall system optimization design, and integrated equipment management. Currently, traditional aircraft utilize a combination of electrical, hydraulic, pneumatic, and mechanical energy, each with its own independent and complex system structure. This results in redundancy in energy distribution, conversion, and application, increased aircraft structural weight, and a need for further improvement in energy utilization efficiency.

[0003] Currently, aircraft environmental control systems generally use engine bleed air as a high-pressure gas source. After being cooled by multi-stage heat exchangers and turbine expansion, the air is then introduced into the cabin for cooling. In this common environmental control scheme, the direct cooling of the engine bleed air by the heat exchangers results in energy loss from the high-temperature, high-pressure gas, and the use of engine bleed air also degrades the performance of the power system. Therefore, the efficiency of this system is generally low. Especially during hypersonic flight, the temperature of the ram air, which serves as the cooling medium for this system, increases dramatically, and it loses its cooling capacity. More-electric aircraft represent a transitional stage in the development of all-electric aircraft. However, current more-electric aircraft have not yet achieved unified, efficient, and reliable power distribution and management, and their environmental control systems do not consider the hypersonic environmental control requirements that gradually emerge with increasing aircraft speed. They also suffer from the limitation that ram air cannot be used as a cooling source during hypersonic flight. Summary of the Invention

[0004] This invention provides a combined cyclic refrigeration system and its working method suitable for all-electric aircraft. It adopts a combination of airborne evaporation cycle, air expansion refrigeration cycle, and liquid cooling cycle. It proposes a combined cyclic refrigeration system for all-electric aircraft that require hypersonic flight, which can adapt to different cabin environmental control requirements and achieve efficient system operation.

[0005] To achieve the above objectives, the present invention adopts the following technical solution:

[0006] A combined cycle refrigeration system suitable for all-electric aircraft includes a vapor compression refrigeration cycle system, an air expansion refrigeration cycle system, and a liquid cooling cycle system; the vapor compression refrigeration cycle system is the cold source; the air expansion refrigeration cycle system meets the cabin environment refrigeration requirements, and the liquid cooling cycle system meets the equipment compartment environment refrigeration requirements; the vapor compression refrigeration cycle system uses two evaporators connected in series, and the two evaporators are respectively connected to the air expansion refrigeration cycle system and the liquid cooling cycle system to sequentially meet the refrigeration needs of the cabin and the equipment compartment.

[0007] The vapor compression refrigeration cycle system includes a first motor, a compressor, a condenser, an expansion valve, a first evaporator, and a second evaporator. The first motor drives the compressor. The compressor, condenser, expansion valve, first evaporator, and second evaporator are connected in series according to the direction of refrigerant flow. The first evaporator exchanges heat with the medium in the air expansion refrigeration cycle system, and the second evaporator exchanges heat with the medium in the liquid cooling cycle system. The refrigerant is compressed by the compressor and then cooled into a liquid by the condenser, releasing heat to the fuel. The fuel is heated and then sent to the combustion chamber to recover heat.

[0008] The air expansion refrigeration cycle system includes a three-way valve, a compressor, a second motor, a high-pressure water separator, a cooling turbine, an electric control valve, a one-way valve, a filter, and an adsorber. The three-way valve is used to mix ambient air and cabin return air before the mixture enters the compressor for compression, heating, and pressurization. It then enters the first evaporator for heat exchange and cooling. After water removal by the high-pressure water separator, the mixture expands to cabin pressure in the cooling turbine, where its temperature is further reduced before being introduced into the cabin for cooling. A portion of the gas in the cabin is discharged as exhaust gas through the electric control valve, while the remaining gas passes through the one-way valve as cabin return air. After purification and adsorption by the filter and adsorber, it mixes with the ambient air at the three-way valve and re-enters the air expansion refrigeration cycle. The ring; wherein the electrically controlled valve can adjust its opening degree according to demand, controlling the proportion of cabin return air, so that the proportion of fresh air is higher during subsonic flight and the proportion of return air is higher during hypersonic flight, so as to balance the needs of cabin comfort and the need to reduce bleed air volume during hypersonic flight; the condensate generated in the high-pressure water separator can be sprayed onto the surface of the first evaporator heat exchanger through the pipeline, which can improve the heat exchange efficiency of hot and cold fluids, while ensuring that the outlet temperature of the cooling turbine is not limited by the freezing point; the compressor-second motor-cooling turbine is a coaxial device, the cooling turbine expands and cools the high-pressure gas and inputs the generated shaft work to the compressor, while the second motor is used to supplement the work lacking by the compressor in compressing low-pressure gas into high-pressure gas;

[0009] The liquid cooling circulation system includes a circulation pump, a liquid storage tank, and an equipment compartment cooling plate. The liquid storage tank is used to store the medium, and the liquid storage tank, circulation pump, second evaporator, equipment compartment cooling plate, and liquid storage tank form a circulation loop in the order of medium flow direction.

[0010] Beneficial effects: This invention provides a combined cycle refrigeration system and its operating method suitable for all-electric aircraft, which has the following advantages compared with the prior art:

[0011] (1) In the design of an all-electric aircraft environmental control system for hypersonic flight, a combined cycle refrigeration system combining vapor compression refrigeration cycle, air expansion refrigeration cycle and liquid cooling cycle is adopted to solve the problem of low refrigeration efficiency of traditional environmental control system and realize a high-efficiency and clean environmental control system.

[0012] (2) The conventional environmental control system design scheme that uses engine compressor bleed air and ram air as a cold source has been eliminated, which is in line with the limited use of ram air during hypersonic flight, maintains engine performance, reduces power loss, and fully meets the environmental control requirements under hypersonic conditions.

[0013] (3) Combining the energy characteristics of all-electric aircraft, the compressor is driven by electric energy in the vapor compression refrigeration cycle, which becomes the power of the refrigeration system. This is in line with the energy characteristics of all-electric aircraft. Compared with ordinary environmental control systems, the phase change heat transfer efficiency of the airborne evaporation cycle is much greater than the sensible heat transfer efficiency, which increases the cooling capacity.

[0014] (4) In the air expansion refrigeration cycle, a compressor-motor-cooling turbine coaxial mechanism is established. The cooling turbine expands and cools the high-pressure gas, while recovering a portion of the high-pressure gas energy. The shaft work is input to the compressor, and electrical energy is used to compensate for the insufficient work of the compressor in compressing the gas, thus saving electrical energy consumption. Based on the use and saving of electrical energy and meeting the design requirements, the redundancy and waste of energy conversion in the traditional environmental control system are reduced, and the energy use efficiency is improved.

[0015] (5) In the vapor compression refrigeration cycle, two evaporators are connected in series to meet the refrigeration needs of the cabin and equipment compartment in turn. Through the two evaporators, the refrigerant changes from liquid to gas-liquid coexistence state and then to gas state. There is a certain degree of superheat, which avoids liquid slugging in the compressor and protects the normal operation of the equipment.

[0016] (6) In the air expansion cooling cycle, the cabin return air is mixed with the external ambient air after passing through the filter and adsorber and then re-enters the air expansion cooling cycle. A portion of the gas forms a closed loop, which reduces the demand for bleed air and reduces the dependence on ram air for high-speed flight and the drag compensation loss caused by bleed air. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of a combined cycle refrigeration system in an embodiment of the present invention;

[0018] In the diagram, 1-first motor, 2-compressor, 3-condenser, 4-expansion valve, 5-first evaporator, 6-second evaporator, 7-three-way valve, 8-compressor, 9-second motor, 10-high-pressure water separator, 11-cooling turbine, 12-electric control valve, 13-one-way valve, 14-filter, 15-adsorber, 16-circulating pump, 17-liquid storage tank, 18-equipment compartment cooling plate. Implementation

[0019] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments:

[0020] like Figure 1 As shown, a combined cycle refrigeration system suitable for all-electric aircraft is proposed. It adopts a combination of a vapor compression refrigeration cycle system, an air expansion refrigeration cycle system, and a liquid cooling cycle system. This eliminates the need for engine compressor bleed air and avoids the conventional design of using ram air as a cold source. It is designed for all-electric aircraft that perform hypersonic flight, meets the different environmental control requirements of the cockpit and equipment compartment, and gives the system the advantages of unified energy, reliability, high efficiency, and clean air.

[0021] The process of generating cooling capacity through a vapor compression refrigeration cycle driven by an electric motor:

[0022] The first motor 1, compressor 2, condenser 3, expansion valve 4, first evaporator 5, and second evaporator 6 constitute a vapor compression refrigeration cycle system. The working medium is refrigerant. The system is driven by the first motor 1 and its function is to replace the ram air to provide the cooling capacity required for cooling. The refrigerant working medium is compressed into a superheated gas in the compressor 2 driven by the first motor 1. It enters the hot side inlet of the condenser 3 and exchanges heat with the cold side fuel. After the fuel is heated, it is sent to the combustion chamber to recover some heat. The refrigerant condenses into a liquid and enters the expansion valve 4 to reduce the pressure. Then it enters the cold side inlet of the first evaporator 5 and exchanges heat with the air medium in the air expansion refrigeration cycle. The air releases heat and its temperature decreases. The refrigerant liquid becomes a gas-liquid coexistence state. Then it enters the cold side inlet of the second evaporator 6 and exchanges heat with the ethylene glycol solution in the liquid cooling cycle. The ethylene glycol solution releases heat and its temperature decreases. The refrigerant changes from a gas-liquid coexistence state to a completely gaseous state and re-enters the compressor 2 for compression, thus continuing the evaporation cycle.

[0023] Cabin environmental control process:

[0024] The air expansion and refrigeration cycle system, consisting of a three-way valve 7, compressor 8, second motor 9, high-pressure water separator 10, cooling turbine 11, electric control valve 12, one-way valve 13, filter 14, and adsorber 15, regulates the pressure and temperature inside the cabin to meet the normal operating requirements of personnel and equipment. External ambient air mixes with cabin return air through the three-way valve 7 and enters the compressor 8 driven by the second motor 9 for compression, heating, and pressurization. It then enters the first evaporator 5 for heat exchange and cooling. After water removal through the high-pressure water separator 10, it enters the cooling turbine 11, expands to cabin pressure, and is further cooled before being introduced into the cabin for cooling. The cabin air is divided into two paths: one path is discharged as exhaust gas through the electric control valve 12, and the other path serves as cabin return air, passing through the one-way valve 13, and is purified and adsorbed by the filter 14 and adsorber 15 before mixing with the external ambient air at the three-way valve 7, re-entering the air expansion and refrigeration cycle, effectively reducing the demand for external ambient air.

[0025] The condensate separated by the high-pressure water separator 10 is sprayed onto the surface of the heat exchanger of the first evaporator 5 through a pipe, which can improve the heat exchange efficiency of the hot and cold fluids, while ensuring that the outlet temperature of the cooling turbine is not limited by the freezing point, thus protecting the normal operation of the turbine. The electric control valve 12 can adjust the opening degree according to demand, controlling the proportion of cabin return air, so that the proportion of fresh air is higher during subsonic flight and the proportion of return air is higher during hypersonic flight, thereby reducing the demand for external bleed air. The one-way valve 13 ensures that the air does not flow backward. The filter 14 and the adsorber 15 purify and filter the gas to ensure clean air. The compressor 8-second motor 9-cooling turbine 11 is a coaxial device. The cooling turbine 11 expands and cools the high-pressure gas and inputs the generated shaft work to the compressor 8. At the same time, the second motor 9 is used to supplement the work that the compressor 8 lacks in compressing the low-pressure gas into high-pressure gas, thereby recovering some of the energy of the high-pressure gas and saving electrical energy.

[0026] Equipment compartment environmental control process:

[0027] The circulating pump 16, the liquid storage tank 17, and the equipment compartment cooling plate 18 constitute a liquid cooling circulation system. Its working medium is ethylene glycol solution, which is used to improve heat exchange efficiency and cool the electronic equipment in the equipment compartment. The ethylene glycol solution is stored in the liquid storage tank 17. When the electronic equipment starts to work, the circulating pump 16 starts. The ethylene glycol liquid is driven by the circulating pump 16 to exchange heat with the refrigerant in the second evaporator 6 and cool down. It absorbs heat in the equipment compartment cooling plate 18 and then enters the liquid storage tank 17 to complete the liquid cooling cycle.

[0028] The above three processes are combined through the heat transfer process of the two evaporators in the vapor compression refrigeration cycle. It combines the characteristics of vapor compression refrigeration cycle replacing ram air as a cold source, air expansion refrigeration cycle meeting cabin cooling and pressurization requirements, and liquid cooling cycle with high heat flux density and high heat transfer efficiency. It reduces resistance loss and recovers some electrical energy, realizing the efficient, reliable and clean operation of the combined refrigeration cycle.

[0029] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined cycle refrigeration system suitable for all-electric aircraft, characterized in that, The system includes a vapor compression refrigeration cycle system, an air expansion refrigeration cycle system, and a liquid cooling cycle system; the vapor compression refrigeration cycle system is the cold source; the air expansion refrigeration cycle system meets the cooling requirements of the cabin environment, and the liquid cooling cycle system meets the cooling requirements of the equipment compartment environment; the vapor compression refrigeration cycle system uses two evaporators connected in series, with the two evaporators connected to the air expansion refrigeration cycle system and the liquid cooling cycle system respectively, to sequentially meet the cooling needs of the cabin and the equipment compartment. The vapor compression refrigeration cycle system includes a first motor, a compressor, a condenser, an expansion valve, a first evaporator, and a second evaporator. The first motor is used to drive the compressor. The compressor, condenser, expansion valve, first evaporator, and second evaporator are connected in series according to the direction of refrigerant flow. The first evaporator exchanges heat with the medium in the air expansion refrigeration cycle system, and the second evaporator exchanges heat with the medium in the liquid cooling cycle system. The air expansion refrigeration cycle system includes a three-way valve, a compressor, a second motor, a high-pressure water separator, a cooling turbine, an electric control valve, a one-way valve, a filter, and an adsorber. The three-way valve is used to mix ambient air and cabin return air. The mixed gas enters the compressor for compression, heating, and pressurization, then enters the first evaporator for heat exchange and cooling. After water removal through the high-pressure water separator, it enters the cooling turbine, expands to cabin pressure, and after further temperature reduction, is introduced into the cabin for cooling. A portion of the gas in the cabin is regulated by the electric control valve and discharged as exhaust gas. The remaining gas passes through the one-way valve as cabin return air, is purified and adsorbed by the filter and adsorber, and then mixes with the ambient air at the three-way valve to re-participate in the air expansion refrigeration cycle. The electric control valve can be adjusted to control the proportion of cabin return air as needed. The compressor-second motor-cooling turbine is a coaxial device. The second motor drives the compressor, and the cooling turbine expands and cools the high-pressure gas while recovering some of the high-pressure gas energy, inputting shaft work to the compressor to reduce power consumption.

2. The combined cycle refrigeration system for all-electric aircraft according to claim 1, characterized in that, The condensate generated in the high-pressure water separator is sprayed onto the surface of the first evaporator heat exchanger through a pipe.

3. The combined cycle refrigeration system for all-electric aircraft according to claim 1, characterized in that, The liquid cooling circulation system includes a circulation pump, a liquid storage tank, and an equipment compartment cooling plate. The liquid storage tank is used to store the medium, and the liquid storage tank, circulation pump, second evaporator, equipment compartment cooling plate, and liquid storage tank form a circulation loop in the order of medium flow direction.

4. The method of operating the combined cycle refrigeration system for all-electric aircraft according to any one of claims 1-3, characterized in that, The system employs a combination of vapor compression refrigeration cycle, air expansion refrigeration cycle, and liquid cooling cycle. In the vapor compression refrigeration cycle, the compressor is driven by electricity. The refrigerant is compressed by the compressor and then enters the condenser to cool into a liquid, releasing heat to the fuel. The fuel, after heating up, is sent to the combustion chamber to recover heat. The liquid refrigerant then enters the expansion valve to expand and reduce pressure, before entering two evaporators connected in series to absorb heat. The first evaporator exchanges heat with the medium in the air expansion refrigeration cycle, while the second evaporator exchanges heat with the medium in the liquid cooling cycle. The refrigerant changes from a liquid to a gas-liquid coexistence state and then to a completely gaseous state. The refrigerant heats up, while the heat exchange medium cools down, thus meeting the cooling needs of the cabin and equipment compartment respectively. The refrigerant then re-enters the compressor to be compressed, continuing the vapor compression refrigeration cycle. In the air expansion refrigeration cycle, a coaxial mechanism of compressor-motor-cooling turbine is established. The cooling turbine expands and cools the high-pressure gas, while recovering some of the high-pressure gas energy and inputting shaft work to the compressor, reducing power consumption.

5. The method of operating the combined cycle refrigeration system for all-electric aircraft according to claim 4, characterized in that, The liquid cooling cycle specifically includes the following process: when the electronic equipment starts working, the circulation pump starts, and the medium stored in the storage tank is driven by the circulation pump to enter the second evaporator for heat exchange and cooling, and then enters the equipment compartment cooling plate to remove the heat generated by the electronic equipment. After completing the heat exchange, it enters the storage tank again to start the liquid cooling cycle again.

6. The method of operating the combined cycle refrigeration system for all-electric aircraft according to claim 4, characterized in that, The air expansion and refrigeration cycle specifically includes the following process: ambient air and cabin return air are mixed through a three-way valve, then compressed and heated by a compressor driven by a second motor, and cooled by heat exchange in the first evaporator. After water removal through a high-pressure water separation system, the air enters a cooling turbine for further temperature reduction before being introduced into the cabin for cooling. A portion of the gas in the cabin is discharged as exhaust gas through an electrically controlled valve, while the remaining gas passes through a one-way valve as cabin return air. After being purified and adsorbed by a filter and an adsorber, it mixes with the ambient air at the three-way valve and re-enters the air expansion and refrigeration cycle. The electrically controlled valve can adjust its opening degree according to demand to control the proportion of cabin return air, ensuring a higher proportion of fresh air during subsonic flight and a higher proportion of return air during hypersonic flight, effectively reducing the demand for ambient air.

Images