Carbon dioxide-to-Brayton cooling and power generation system and method coupled with fuel heat sink

Abstract

The present invention discloses a carbon dioxide variable Brayton cooling and power generation system and method coupled with a fuel heat sink. The system includes a working fluid pump, a preheater, a regenerator, a wall heat exchanger, an expander, a generator, a first cooler, a second cooler, a fuel storage tank, a fuel pump, a fuel turbine, a first valve, a second valve, and a third valve. The present invention conducts active cooling and expansion work for power generation, adopts a coupling method of carbon dioxide and fuel to cool the high-temperature wall surface in a hypersonic vehicle, and utilizes the high-temperature heat load for power generation, solving the problems of insufficient thermal protection and power supply of the vehicle. The present invention makes full use of the limited fuel heat sink and the physical property change characteristics of CO2 to realize a variable Brayton cycle, improve the cooling and power generation capabilities of the CO2 Brayton system, and compared with the fuel cracking gas turbine system, this system can be applied to vehicles operating at a wider range of Mach numbers.

Description

Technical Field

[0001] The present invention relates to the field of aircraft cooling and power cogeneration, and in particular to a carbon dioxide variable Brayton cooling and power generation system and method coupled with a fuel heat sink. Background Art

[0002] In the development of hypersonic aircraft, the fuselage and combustion chamber of the engine are heated by the high-temperature flow during flight, generating a large amount of aerodynamic heat. The wall temperature rises sharply under the aerodynamic heating effect, which may cause the engine wall to burn through in severe cases, causing serious impact on the operation of the internal system of the aircraft. In addition, long flight time and reusability have become important technical directions for the development of future aircraft, and the power demand of aircraft onboard systems has also increased, which has also put forward higher requirements on the power generation capacity of the onboard power supply system. Therefore, it is necessary to develop more efficient combined cooling and power generation technology in hypersonic aircraft.

[0003] In the cooling and power generation systems of aircraft, fuel cracking gas turbine systems and closed Brayton cycle systems are currently the main technologies.

[0004] The fuel cracking gas turbine system uses fuel as the working fluid. The working capacity of fuel is lower than that of carbon dioxide (CO2). When the temperature exceeds 700°C, the fuel is prone to coking and carbon deposition, which in turn blocks the coolant channel and weakens the cooling effect. At the same time, the fuel that an aircraft can carry is limited, so the fuel cracking gas turbine system is difficult to meet the cooling and power generation requirements of the aircraft.

[0005] In the closed Brayton cycle, the working fluid is in the supercritical region and the fuel is used as the circulating cold source. CO2 has the characteristics of high density, large specific heat capacity, and high thermal conductivity in the near-critical region. Reducing the CO2 temperature to below the critical temperature is conducive to further reducing the compression work and system volume of the system, which is in line with the lightweight and compact development of the aircraft. The patent specification with the publication number CN108657442 A discloses an aircraft and a thermal protection system, using carbon dioxide as a fluid medium. The supercritical carbon dioxide is pressurized by a compressor and is divided into two streams. One stream passes through the second heat source pipeline located on the windward side of the fuselage, the turbine, the second cold source pipeline located on the leeward side of the fuselage, the second connecting pipeline and the compressor to form the second circuit, which is the Brayton cycle engine system. The other stream flows through the first heat source pipeline located at the front edge of the nose or wing, the first cold source pipeline located on the leeward side of the fuselage, the first connecting pipeline, and the compressor to form the first circuit. The Brayton cycle engine system provides pressurized supercritical CO2, thereby driving the supercritical CO2 to circulate between the heat source pipeline (high temperature zone) and the cold source pipeline (low temperature zone, normal temperature fuel), realizing heat exchange between the high temperature zone and the low temperature zone.

[0006] However, due to the limited heat sink of the fuel, the storage temperature at room temperature is generally 293K. In the traditional regenerative Brayton cycle using CO2 as the working fluid, there is a problem of difficulty in cooling CO2, and the thermal efficiency of the cycle is difficult to further improve. The output power and cooling capacity of the system per unit mass of working fluid are poor.

[0007] In the traditional regenerative Brayton system, the fuel has less remaining heat sink after absorbing the heat load of the CO2 Brayton cycle, and the cooling capacity in the high-temperature wall is reduced. Further thermal coupling of the fuel with the CO2 Brayton cycle is beneficial to improving the utilization rate of the limited fuel heat sink. Summary of the invention

[0008] The present invention provides a carbon dioxide variable Brayton cooling and power generation system and method coupled with a fuel heat sink, which performs active cooling and expansion work power generation, uses carbon dioxide and fuel coupling to cool the high-temperature wall surface in a hypersonic aircraft, and uses high-temperature heat load to generate electricity, thereby solving the problems of insufficient thermal protection of the aircraft and power supply.

[0009] The present invention aims to make full use of the limited fuel heat sink and the property change characteristics of CO2 to realize the variable Brayton cycle and improve the cooling capacity and output work per unit mass of working fluid in the CO2 Brayton system.

[0010] A carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink, comprising a working fluid pump, a preheater, a regenerator, a wall heat exchanger, an expander, a generator, a first cooler, a second cooler, a fuel storage tank, a fuel pump, a fuel turbine, a first valve, a second valve and a third valve;

[0011] A working fluid pump, a preheater, a regenerator, a wall heat exchanger, an expander, a regenerator, a first cooler, and a second cooler are sequentially connected to form a carbon dioxide circulation loop;

[0012] The fuel storage tank, the fuel pump, the second cooler, the first valve, the wall heat exchanger, and the fuel turbine are sequentially connected to form a first fuel pipeline;

[0013] The fuel storage tank, the fuel pump, the second cooler, the third valve, the first cooler, the preheater, the wall heat exchanger, and the fuel turbine are sequentially connected to form a second fuel pipeline;

[0014] The fuel storage tank, the fuel pump, the second valve, the first cooler, the preheater, the wall heat exchanger, and the fuel turbine are sequentially connected to form a third fuel pipeline;

[0015] The generator is connected to the expander to convert the output power of the expander into electrical energy. Specifically, the generator and the expander can be connected coaxially or coaxially according to the specific spatial layout of the system.

[0016] The present invention provides a low-temperature fuel heat sink to the system through a fuel storage tank for absorbing the heat load of the CO2 cooling process. The heated fuel is preheated in the preheater as a low-temperature heat source for CO2, and then the fuel enters the wall heat exchanger as a coolant for the high-temperature wall to absorb the high-temperature heat load; the CO2 is pressurized by a working fluid pump and absorbs heat and heats up in the preheater, the regenerator and the wall heat exchanger, and then enters the expander for heat-to-work conversion to output electrical energy. The CO2 at the outlet of the expander is cooled or even condensed through the regenerator, the first cooler and the second cooler, and then enters the working fluid pump to complete a working cycle; the output work of the expander is converted into electrical energy for supply by a generator; the fuel is used to cool or even condense the CO2 at the outlet of the low-pressure side of the regenerator through the first cooler and the second cooler; the fuel at the outlet of the wall heat exchanger is expanded and heat-to-work converted through a fuel turbine (equivalent to an expander of the fuel) to generate electricity.

[0017] In a preferred embodiment, the wall heat exchanger includes a flow channel with fuel as a coolant and a flow channel with carbon dioxide as a coolant. The two flow channels are fixedly embedded in the high-temperature wall surface that needs to be cooled, and form an integrated structure with the device wall surface that needs to be cooled. In this way, when the fuel reaches the upper temperature limit in the wall flow channel, CO2 can continue to absorb heat and heat up in the wall flow channel, thereby meeting the cooling requirements of the high-temperature wall surface.

[0018] Furthermore, the high temperature wall surface is the wall surface of the aircraft engine and / or the wall surface of the aircraft head. The high temperature wall surface is heated and heated by the high temperature incoming flow during the flight, and the heat of the high temperature wall surface is taken away by the fuel and CO2 in the wall heat exchanger, and the temperature of the high temperature wall surface is reduced, thereby achieving the purpose of cooling.

[0019] In a preferred example, the temperature of carbon dioxide at the outlet of the first cooler is higher than the critical temperature (304K), and the second cooler acts as a condenser. Carbon dioxide is condensed by the fuel in the second cooler to below the critical temperature, and is in a saturated or supercooled liquid state at the outlet of the second cooler. The purpose of this process is, on the one hand, to improve the heat exchange matching between CO2 and the fuel in the first cooler, and on the other hand, to enable CO2 to condense in the second cooler using a limited fuel heat sink, thereby reducing the compression power consumption of CO2 in the working fluid pump.

[0020] In a preferred embodiment, the expander is a volumetric expander, which can be selected from a piston expander or a scroll expander. The stable operation, compact structure and high conversion efficiency of such expanders are utilized to improve the power-to-weight ratio of the aircraft combined cooling and power supply system.

[0021] In a preferred example, the temperature and pressure of carbon dioxide at the inlet of the working fluid pump are both lower than the critical point (critical temperature 304K, critical pressure 7.38MPa), thereby reducing the effect of CO2 compression work. Specifically, the temperature can be selected to be 303K and the pressure can be the saturation pressure corresponding to the temperature.

[0022] In a preferred embodiment, the carbon dioxide outlet of the preheater is connected to the high-pressure side inlet of the regenerator, the high-pressure side outlet of the regenerator is connected to the carbon dioxide inlet of the wall heat exchanger, the expander outlet is connected to the low-pressure side inlet of the regenerator, and the low-pressure side outlet of the regenerator is connected to the carbon dioxide inlet of the first cooler;

[0023] In the regenerator, the heat of the carbon dioxide on the low-pressure side of the regenerator from the expander outlet is input into the carbon dioxide on the high-pressure side of the regenerator from the preheater.

[0024] In a preferred example, the fuel pump is used to pressurize the fuel from the fuel storage tank to a pressure above a critical point and then discharge the fuel.

[0025] In a preferred example, the flow ratio of CO2 and fuel in the first cooler is 2.76, which improves the heat exchange matching between CO2 and fuel in the first cooler; the flow ratio of CO2 and fuel in the second cooler is 0.16, which can make the fuel with a storage temperature of 293K meet the condensation requirements of CO2.

[0026] In a preferred example, the temperature of the fuel in the first cooler increases after absorbing the heat load of carbon dioxide, and then part of the heat is input into the carbon dioxide in the preheater in the preheater, reducing the temperature of the fuel entering the wall heat exchanger, and improving the work capacity and cycle thermal efficiency of CO2. The present invention has found that the setting of the preheater and the heat exchange between the fuel and carbon dioxide in the preheater, although having little effect on the total heat, can significantly improve the overall work of the system, the higher the carbon dioxide temperature, the higher the system output power.

[0027] The present invention also provides a carbon dioxide-to-Brayton cooling and power generation method coupled with a fuel heat sink, using the carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink;

[0028] When the fuel temperature of the fuel storage tank is lower than the carbon dioxide condensation temperature by more than 5K, execute method 1; otherwise, execute method 2;

[0029] Method 1:

[0030] The first valve and the second valve are opened, and the third valve is closed. The second cooler acts as a condenser. Carbon dioxide is used as the working medium. The temperature and pressure of carbon dioxide at the inlet of the working fluid pump are both lower than the critical point (critical temperature 304K, critical pressure 7.38MPa), and it enters the preheater after being pressurized by the working fluid pump. The carbon dioxide outlet of the preheater is connected to the inlet of the high-pressure side of the regenerator, and the outlet of the high-pressure side of the regenerator is connected to the carbon dioxide inlet of the wall heat exchanger. Carbon dioxide acts as a coolant for the high-temperature wall and absorbs the heat load of the high-temperature wall in the wall heat exchanger. The carbon dioxide outlet of the wall heat exchanger is connected to the inlet of the expander, and the expander is used to convert carbon dioxide into heat and work. The outlet of the expander is connected to the inlet of the low-pressure side of the regenerator, and the regenerator is used to input the heat of the carbon dioxide on the low-pressure side of the regenerator from the outlet of the expander to the high-pressure side of the regenerator from the preheater. The low-pressure side outlet of the regenerator is connected to the carbon dioxide inlets of the first cooler and the second cooler in sequence; the fuel pump is used to pressurize the fuel from the fuel storage tank to above the critical pressure and then discharge it; the fuel is split at the outlet of the fuel pump and connected to the fuel inlets of the first cooler and the second cooler respectively, and the first cooler and the second cooler are used to cool and condense the carbon dioxide from the low-pressure side outlet of the regenerator respectively; the carbon dioxide in the second cooler is completely condensed by coupling with the fuel and finally enters the working fluid pump; the fuel in the first cooler absorbs the heat load of the carbon dioxide and its temperature rises, and then enters the preheater to input part of the heat into the carbon dioxide in the preheater; the fuel at the preheater fuel outlet is mixed with the fuel at the second cooler fuel outlet and then enters the wall heat exchanger, and after absorbing heat and heating up, enters the fuel turbine for heat-to-work conversion;

[0031] Method 2:

[0032] Open the third valve, close the first valve and the second valve; use carbon dioxide as the working medium; the temperature of carbon dioxide at the inlet of the working fluid pump is higher than the critical temperature and the pressure is lower than the critical pressure, and enters the preheater after being pressurized by the working fluid pump; the carbon dioxide outlet of the preheater is connected to the inlet of the high-pressure side of the regenerator, and the outlet of the high-pressure side of the regenerator is connected to the carbon dioxide inlet of the wall heat exchanger; carbon dioxide serves as a coolant for the high-temperature wall and absorbs the heat load of the high-temperature wall in the wall heat exchanger; the carbon dioxide outlet of the wall heat exchanger is connected to the inlet of the expander, and the expander is used to convert carbon dioxide into heat work; the outlet of the expander is connected to the inlet of the low-pressure side of the regenerator, and the regenerator is used to input the heat of the carbon dioxide on the low-pressure side of the regenerator from the outlet of the expander to the carbon dioxide on the high-pressure side of the regenerator from the preheater Carbon neutral; the low-pressure side outlet of the regenerator is connected to the carbon dioxide inlet of the first cooler and the second cooler in sequence; the fuel pump is used to pressurize the fuel from the fuel storage tank to above the critical pressure and then discharge it; the fuel is not diverted at the fuel pump outlet, and is connected to the fuel inlet of the second cooler and the first cooler in sequence, and the first cooler and the second cooler are both used to cool the carbon dioxide from the low-pressure side outlet of the regenerator; the carbon dioxide in the second cooler is cooled by coupling with the fuel, and finally enters the working fluid pump; the fuel in the first cooler absorbs the heat load of the carbon dioxide and its temperature rises, and then enters the preheater to input part of the heat into the carbon dioxide in the preheater; the fuel at the fuel outlet of the preheater enters the wall heat exchanger, absorbs heat and heats up, and then enters the fuel turbine for heat-to-work conversion.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. The present invention proposes a CO2 Brayton cooling and power generation system and method coupled with a fuel heat sink, which adopts a CO2 Brayton cycle to perform wall cooling and power supply in an aircraft, solves the cooling difficulty problem of the current fuel cracking gas turbine system caused by the limited fuel heat sink, and alleviates the problem of easy coking and carbon deposition of fuel during cooling of high-temperature walls.

[0035] 2. The present invention proposes a CO2 variable Brayton cooling and power generation system and method coupled with a fuel heat sink, which uses fuel diversion to further reduce the CO2 temperature in the variable Brayton cycle and realize a transcritical compression process. Compared with the traditional regenerative Brayton cycle, the compression work is reduced and the heat exchange matching of the cooling process is improved.

[0036] 3. The CO2 variable Brayton cooling and power generation system and method coupled with a fuel heat sink proposed in the present invention improves the working capacity of CO2 in the expander and the available heat sink of the fuel in the combustion chamber wall by increasing the coupling between the fuel and CO2 in the preheater.

[0037] 4. The present invention proposes a CO2-Brayton cooling and power generation system and method coupled with a fuel heat sink, which uses CO2 and fuel as coolants for high-temperature walls. Since CO2 is not prone to coking and carbon deposition, it can adapt to higher wall temperatures than the fuel cracking gas turbine system, making it suitable for aircraft operating in a wider range of Mach number conditions.

[0038] 5. The CO2 variable Brayton cooling and power generation system coupled with a fuel heat sink proposed in the present invention improves the system's unit mass working fluid output power by 24.2 to 72.0% compared with the traditional regenerative Brayton system through the fuel diversion and the coupling of fuel and CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 A schematic diagram of the CO2 Brayton cooling and power generation system coupled with a fuel heat sink and its working process proposed by the present invention;

[0040] Figure 2 This is a diagram showing the temperature changes of CO2 and fuel at different wall temperatures and the corresponding unit mass flow output work changes in the CO2 variable Brayton cooling and power generation system coupled with a fuel heat sink proposed by the present invention.

[0041] Figure 3 This is a graph showing how the output work per unit mass of working fluid of the CO2 Brayton cooling and power generation system of Example 1 changes with the high-temperature wall temperature.

[0042] Figure 4 This is a graph showing how the output work per unit mass of working fluid changes with the high-temperature wall temperature in the CO2 Brayton cooling and power generation system of Example 2 after the fuel storage temperature is increased. DETAILED DESCRIPTION

[0043] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not used to limit the scope of the present invention.

[0044] The critical temperature of CO2 is about 304K, and the critical pressure is about 7.38MPa. The density and specific heat capacity of CO2 below the critical point are relatively high. Lowering the final temperature of CO2 during the cooling process can reduce the power consumption of the compression process and improve the cooling capacity of CO2 on the high-pressure side. When the traditional regenerative Brayton system uses fuel as a circulating cold source, it is difficult to reduce the temperature of CO2 to below the critical temperature, and there is a problem of condensation difficulty. The present invention overcomes this problem by coupling the fuel diversion method.

[0045] Example 1

[0046] The carbon dioxide Brayton cooling and power generation system coupled with the fuel heat sink of the present invention is used for the combustion chamber wall of the scramjet engine or the head wall of the hypersonic vehicle, and the fuel stored at 293K at room temperature is used as the circulating cold source. The fuel has the conditions to condense CO2 to below the critical temperature. Since the fuel absorbs heat to generate cracked gas containing many components, the calculation of its flow and thermodynamic characteristics is complicated, and n-decane is generally used instead. Therefore, n-decane is used instead of fuel for analysis in this embodiment.

[0047] There is a large heat exchange temperature difference between the fuel storage temperature and the condensation temperature of CO2. The second cooler 8 acts as a condenser. The fuel condenses the outlet temperature of CO2 in the second cooler 8 to a supercooled state lower than the condensation temperature.

[0048] Open the first valve 12, the second valve 13, close the third valve 14, and use Figure 1 The fuel splitting method shown cools and condenses CO2 respectively. After the temperature of CO2 is reduced in the first cooler 7, it enters the second cooler 8 and is further cooled to below the critical point, thereby realizing a variable Brayton cycle.

[0049] The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink of this embodiment is as follows: Figure 1 As shown, it includes a working fluid pump 1, a preheater 2, a regenerator 3, a wall heat exchanger 4, an expander 5, a generator 6, a first cooler 7, a second cooler 8, a fuel storage tank 9, a fuel pump 10, a fuel turbine 11, a first valve 12, a second valve 13 and a third valve 14.

[0050] The working fluid pump 1, the preheater 2, the regenerator 3, the wall heat exchanger 4, the expander 5, the regenerator 3, the first cooler 7, and the second cooler 8 are connected in sequence to form a carbon dioxide circulation loop. Specifically, the carbon dioxide outlet of the preheater 2 is connected to the high-pressure side inlet of the regenerator 3, the high-pressure side outlet of the regenerator 3 is connected to the carbon dioxide inlet of the wall heat exchanger 4, the expander 5 outlet is connected to the low-pressure side inlet of the regenerator 3, and the low-pressure side outlet of the regenerator 3 is connected to the carbon dioxide inlet of the first cooler 7. In the regenerator 3, the heat of the carbon dioxide on the low-pressure side of the regenerator 3 from the outlet of the expander 5 is input into the carbon dioxide on the high-pressure side of the regenerator 3 from the preheater 2.

[0051] The fuel storage tank 9, the fuel pump 10, the second cooler 8, the first valve 12, the wall heat exchanger 4, and the fuel turbine 11 are sequentially connected to form a first fuel pipeline.

[0052] The fuel storage tank 9, the fuel pump 10, the second valve 13, the first cooler 7, the preheater 2, the wall heat exchanger 4, and the fuel turbine 11 are sequentially connected to form a third fuel pipeline.

[0053] The generator 6 and the expander 5 can be connected coaxially or coaxially according to the specific spatial layout of the system to convert the output work of the expander 5 into electrical energy.

[0054] In the carbon dioxide circulation loop, the carbon dioxide at the inlet of the working fluid pump 1 is in a state where both the temperature and pressure are lower than the critical point. After being pressurized by the working fluid pump 1, the carbon dioxide enters the preheater 2, and enters the high-pressure side inlet of the regenerator 3 after heat exchange with the fuel in the preheater 2 to increase the temperature. After heat exchange with the carbon dioxide on the low-pressure side of the regenerator 3 to increase the temperature, the carbon dioxide enters the wall heat exchanger 4 as a coolant to absorb the heat load of the high-temperature wall. The carbon dioxide flowing out of the wall heat exchanger 4 is in a state of high temperature and high pressure. After being reduced in pressure by the expander 5, it becomes a state of high temperature and low pressure. Then, it enters the low-pressure side of the regenerator 3 to heat the carbon dioxide on the high-pressure side of the regenerator 3. After flowing out from the low-pressure side of the regenerator 3, it enters the first cooler 7. After heat exchange with the fuel pressurized to above the critical pressure in the first cooler 7 to reduce the temperature, it enters the second cooler 8. After further heat exchange with the fuel pressurized to above the critical pressure in the second cooler 8 to reduce the temperature, it becomes a state where both the temperature and pressure are lower than the critical point, and then returns to the working fluid pump 1 for the next cycle.

[0055] In the first fuel pipeline, the fuel from the fuel storage tank 9 is pressurized to above the critical pressure by the fuel pump 10 and then enters the second cooler 8. After heat exchange with the carbon dioxide in the second cooler 8 and heating, it enters the wall heat exchanger 4 as a coolant to absorb the heat load of the high-temperature wall surface, and finally enters the fuel turbine 11 for heat-to-work conversion to output electrical energy.

[0056] In the third fuel pipeline, the fuel from the fuel storage tank 9 is pressurized to above the critical pressure by the fuel pump 10 and then enters the first cooler 7. After being heated by heat exchange with the carbon dioxide in the first cooler 7, it enters the preheater 2. After being cooled by heat exchange with the carbon dioxide in the preheater 2, it is mixed with the fuel flowing out of the second cooler 8 and enters the wall heat exchanger 4 as a coolant to absorb the heat load of the high-temperature wall surface. Finally, it enters the fuel turbine 11 for heat-to-work conversion to output electrical energy.

[0057] The working process of the carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink in this embodiment is as follows:

[0058] Carbon dioxide is used as the working medium; the temperature and pressure of carbon dioxide at the inlet of the working fluid pump 1 are lower than the critical point, and it enters the preheater 2 after being pressurized by the working fluid pump 1; the carbon dioxide outlet of the preheater 2 is connected to the high-pressure side inlet of the regenerator 3, and the high-pressure side outlet of the regenerator 3 is connected to the carbon dioxide inlet of the wall heat exchanger 4; carbon dioxide is used as a coolant for the high-temperature wall surface, and absorbs the heat load of the high-temperature wall surface in the wall heat exchanger 4; that is, after being discharged from the outlet of the working fluid pump 1, CO2 enters the preheater 2, the regenerator 3 and the wall heat exchanger 4 in turn to absorb heat and heat up, reaching a supercritical state of high temperature and pressure. , and then flows out from the carbon dioxide outlet of the wall heat exchanger 4, enters the expander 5 to expand and do work, and the expander 5 is used to convert carbon dioxide into heat and work; the outlet of the expander 5 is connected to the low-pressure side inlet of the regenerator 3, and CO2 is discharged from the outlet of the expander 5 and enters the regenerator 3 to transfer the heat of the high-temperature CO2 to the CO2 with a lower temperature, that is, the regenerator 3 is used to input the heat of the carbon dioxide on the low-pressure side of the regenerator 3 from the outlet of the expander 5 into the carbon dioxide on the high-pressure side of the regenerator 3 from the preheater 2; the outlet of the low-pressure side of the regenerator 3 is connected to the first cooler 7 and the second cooler The carbon dioxide inlet of the cooler 8 is connected in sequence, and the CO2 enters the first cooler 7 after the outlet temperature of the regenerator 3 is reduced, and enters the second cooler 8 after being cooled by the fuel and further condensed to below the critical temperature; the fuel pump 10 is used to pressurize the fuel from the fuel storage tank 9 to above the critical pressure and then discharge it; the fuel is split at the outlet of the fuel pump 10 and connected to the fuel inlet of the first cooler 7 and the second cooler 8 respectively, a part of the fuel enters the first cooler 7, and the other part of the fuel enters the second cooler 8, respectively, to cool the CO2; the first cooler 7 and the second cooler The two coolers 8 are used to cool and condense the carbon dioxide from the low-pressure side outlet of the regenerator 3; the carbon dioxide in the second cooler 8 is completely condensed by coupling with the fuel, and finally enters the working fluid pump 1; the fuel in the first cooler 7 absorbs the heat load of the carbon dioxide and its temperature rises, and then enters the preheater 2 to input part of the heat into the carbon dioxide in the preheater 2; the fuel at the fuel outlet of the preheater 2 is mixed with the fuel at the fuel outlet of the second cooler 8 and enters the wall heat exchanger 4, and after absorbing heat and heating, enters the fuel turbine 11 for heat-to-work conversion to output electrical energy.

[0059] The wall heat exchanger 4 includes a flow channel using fuel as a coolant and a flow channel using carbon dioxide as a coolant. The two flow channels are fixedly embedded in the high-temperature wall surface that needs to be cooled, forming an integrated structure with the wall surface of the device that needs to be cooled.

[0060] The high temperature wall surface is the wall surface of the aircraft engine and / or the wall surface of the aircraft head. During the flight, the heat of the high temperature wall surface is taken away by the fuel and CO2 through the flow channel in the wall heat exchanger 4, and the wall surface temperature is reduced, thereby achieving the purpose of cooling.

[0061] The temperature of carbon dioxide at the outlet of the first cooler 7 is higher than the critical temperature, and is condensed by the fuel to below the critical temperature in the second cooler 8 , and is in a saturated or supercooled liquid state at the outlet of the second cooler 8 .

[0062] The expander 5 may be a volumetric expander, and may be specifically selected from a piston expander or a scroll expander.

[0063] In this embodiment, the flow ratio of CO2 and fuel in the first cooler 7 is 2.76, which improves the heat exchange matching between CO2 and fuel in the first cooler 7; the flow ratio of CO2 and fuel in the second cooler 8 is 0.16, which can make the fuel with a storage temperature of 293K meet the condensation requirements of CO2.

[0064] like Figure 2 As shown in the figure, since CO2 is not susceptible to coking and carbon deposition caused by high temperature, it avoids the problem of being unable to adapt to high wall temperature when using fuel as the only coolant. Therefore, the CO2 temperature increases with the increase of high temperature wall temperature. At the same time, the output power of CO2 in the variable Brayton system is also significantly improved compared with fuel.

[0065] like Figure 3 As shown, the carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink proposed in Example 1 has an improved power generation capacity through the diversion of the fuel and the coupling with CO2 in the preheater 2, and the output work per unit mass of the working fluid is increased by 24.2% to 72.0% compared with the traditional heat recovery Brayton system.

[0066] Example 2

[0067] The method used is similar to that of Example 1. Figure 1 The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink shown is different from Example 1 in that the fuel temperature of the fuel storage tank 9 is lower than the carbon dioxide condensation temperature, but the temperature difference between the two is less than 5K, and the fuel will have a slight temperature rise after passing through the fuel pump 10, or the fuel temperature of the fuel storage tank 9 is not lower than the carbon dioxide condensation temperature, making it difficult for the second cooler 8 to act as a condenser. It is difficult for the fuel in the second cooler 8 to condense the outlet temperature of CO2 to a supercooled state below the condensation temperature, and the carbon dioxide is still in a gaseous state.

[0068] Close the first valve 12 and the second valve 13, and open the third valve 14. The fuel only passes through the second fuel pipeline which is composed of the fuel storage tank 9, the fuel pump 10, the second cooler 8, the third valve 14, the first cooler 7, the preheater 2, the wall heat exchanger 4, and the fuel turbine 11 connected in sequence.

[0069] The storage temperature of the fuel in the fuel storage tank 9 and the condensation temperature of CO2 cannot maintain a heat exchange temperature difference of more than 5K. It is difficult to condense CO2 by using the fuel diversion method of Example 1. At this time, Example 2 closes the first valve 12 and the second valve 13, and opens the third valve 14. After the fuel is discharged from the fuel storage tank 9 through the fuel pump 10, it directly enters the second cooler 8 and the first cooler 7, and the CO2 is cooled from the temperature of the outlet of the low-pressure side of the regenerator 3 to a state where the temperature is higher than the critical temperature and the pressure is lower than the critical pressure. After the fuel absorbs the CO2 heat load in the second cooler 8 and the first cooler 7, the temperature rises, and then enters the preheater 2 to re-input part of the heat into the CO2. The rest of the process is similar to Example 1.

[0070] like Figure 4 As shown, the fuel storage temperature of Example 2 is 303K, the compression work of CO2 is increased, and the carbon dioxide Brayton cooling and power generation system coupled with the fuel heat sink proposed in Example 2 is still improved by 8.8% to 18.9% compared with the traditional heat recovery Brayton system.

[0071] In addition, it should be understood that after reading the above description of the present invention, those skilled in the art may make various changes or modifications to the present invention, and these equivalent forms also fall within the scope defined by the claims attached to this application.

Claims

1. A carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink, characterized in that: It comprises a working fluid pump (1), a preheater (2), a regenerator (3), a wall heat exchanger (4), an expander (5), a generator (6), a first cooler (7), a second cooler (8), a fuel storage tank (9), a fuel pump (10), a fuel turbine (11), a first valve (12), a second valve (13) and a third valve (14); A working fluid pump (1), a preheater (2), a regenerator (3), a wall heat exchanger (4), an expander (5), a regenerator (3), a first cooler (7), and a second cooler (8) are sequentially connected to form a carbon dioxide circulation loop; A fuel storage tank (9), a fuel pump (10), a second cooler (8), a first valve (12), a wall heat exchanger (4), and a fuel turbine (11) are sequentially connected to form a first fuel pipeline; A fuel storage tank (9), a fuel pump (10), a second cooler (8), a third valve (14), a first cooler (7), a preheater (2), a wall heat exchanger (4), and a fuel turbine (11) are sequentially connected to form a second fuel pipeline; The fuel storage tank (9), the fuel pump (10), the second valve (13), the first cooler (7), the preheater (2), the wall heat exchanger (4), and the fuel turbine (11) are sequentially connected to form a third fuel pipeline; The generator (6) is connected to the expander (5) and converts the output work of the expander (5) into electrical energy.

2. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The wall heat exchanger (4) comprises a flow channel using fuel as a coolant and a flow channel using carbon dioxide as a coolant. The two flow channels are fixedly embedded in a high-temperature wall surface that needs to be cooled, forming an integrated structure with the wall surface of the device that needs to be cooled.

3. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 2, characterized in that: The high-temperature wall surface is an aircraft engine wall surface and / or an aircraft head wall surface.

4. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The temperature of the carbon dioxide at the outlet of the first cooler (7) is higher than the critical temperature. The second cooler (8) acts as a condenser. The carbon dioxide is condensed by the fuel to below the critical temperature in the second cooler (8) and is in a saturated or supercooled liquid state at the outlet of the second cooler (8).

5. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The expander (5) is a volumetric expander selected from a piston expander or a scroll expander.

6. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The carbon dioxide at the inlet of the working fluid pump (1) is in a state where both the temperature and pressure are lower than the critical point.

7. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The carbon dioxide outlet of the preheater (2) is connected to the high-pressure side inlet of the regenerator (3), the high-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlet of the wall heat exchanger (4), the outlet of the expander (5) is connected to the low-pressure side inlet of the regenerator (3), and the low-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlet of the first cooler (7); In the regenerator (3), heat of carbon dioxide on the low-pressure side of the regenerator (3) from the outlet of the expander (5) is input into carbon dioxide on the high-pressure side of the regenerator (3) from the preheater (2).

8. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The fuel pump (10) is used to pressurize the fuel from the fuel storage tank (9) to a pressure above a critical point and then discharge the fuel.

9. The carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink according to claim 1, characterized in that: The fuel in the first cooler (7) absorbs the heat load of the carbon dioxide and its temperature rises. Then, in the preheater (2), part of the heat is input into the carbon dioxide in the preheater (2).

10. A carbon dioxide-Brayton cooling and power generation method coupled with a fuel heat sink, characterized in that: A carbon dioxide-to-Brayton cooling and power generation system coupled with a fuel heat sink as described in claim 1; When the fuel temperature of the fuel storage tank (9) is lower than the carbon dioxide condensation temperature by more than 5K, method 1 is executed; otherwise, method 2 is executed; Method 1: The first valve (12) and the second valve (13) are opened, and the third valve (14) is closed, so that the second cooler (8) functions as a condenser; carbon dioxide is used as the working medium; the temperature and pressure of the carbon dioxide at the inlet of the working medium pump (1) are both lower than the critical point, and the carbon dioxide enters the preheater (2) after being pressurized by the working medium pump (1); the carbon dioxide outlet of the preheater (2) is connected to the high-pressure side inlet of the regenerator (3), and the high-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlet of the wall heat exchanger (4); Carbon dioxide is used as a coolant for the high-temperature wall surface and absorbs the heat load of the high-temperature wall surface in the wall heat exchanger (4); the carbon dioxide outlet of the wall heat exchanger (4) is connected to the inlet of the expander (5), and the expander (5) is used to convert carbon dioxide into heat work; the outlet of the expander (5) is connected to the inlet of the low-pressure side of the regenerator (3), and the regenerator (3) is used to input the heat of the carbon dioxide on the low-pressure side of the regenerator (3) from the outlet of the expander (5) into the carbon dioxide on the high-pressure side of the regenerator (3) from the preheater (2); The low-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlets of the first cooler (7) and the second cooler (8) in sequence; the fuel pump (10) is used to pressurize the fuel from the fuel storage tank (9) to above the critical pressure and then discharge it; the fuel is split at the outlet of the fuel pump (10) and connected to the fuel inlets of the first cooler (7) and the second cooler (8) respectively, and the first cooler (7) and the second cooler (8) are used to cool and condense the carbon dioxide from the low-pressure side outlet of the regenerator (3); the carbon dioxide in the second cooler (8) is completely condensed by coupling with the fuel and finally enters the working fluid pump (1); the fuel in the first cooler (7) absorbs the heat load of the carbon dioxide and its temperature rises, and then enters the preheater (2) to input part of the heat into the carbon dioxide in the preheater (2); the fuel at the fuel outlet of the preheater (2) is mixed with the fuel at the fuel outlet of the second cooler (8) and then enters the wall heat exchanger (4), and after absorbing heat and rising in temperature, enters the fuel turbine (11) for heat-to-work conversion; Method 2: The third valve (14) is opened, and the first valve (12) and the second valve (13) are closed; carbon dioxide is used as the working medium; the temperature of the carbon dioxide at the inlet of the working medium pump (1) is higher than the critical temperature and the pressure is lower than the critical pressure, and the carbon dioxide enters the preheater (2) after being pressurized by the working medium pump (1); the carbon dioxide outlet of the preheater (2) is connected to the high-pressure side inlet of the regenerator (3), and the high-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlet of the wall heat exchanger (4); the carbon dioxide serves as a coolant for the high-temperature wall surface and absorbs the heat load of the high-temperature wall surface in the wall heat exchanger (4); the carbon dioxide outlet of the wall heat exchanger (4) is connected to the inlet of the expander (5), and the expander (5) is used to convert carbon dioxide into heat; the outlet of the expander (5) is connected to the inlet of the low-pressure side of the regenerator (3), and the regenerator (3) is used to input the heat of the carbon dioxide on the low-pressure side of the regenerator (3) from the outlet of the expander (5) to the high-pressure side of the regenerator (3) from the preheater (2) The low-pressure side outlet of the regenerator (3) is connected to the carbon dioxide inlets of the first cooler (7) and the second cooler (8) in sequence; the fuel pump (10) is used to pressurize the fuel from the fuel storage tank (9) to above the critical pressure and then discharge it; the fuel is not divided at the outlet of the fuel pump (10) and is connected to the fuel inlets of the second cooler (8) and the first cooler (7) in sequence, and the first cooler (7) and the second cooler (8) are both used to cool the carbon dioxide from the low-pressure side outlet of the regenerator (3); the carbon dioxide in the second cooler (8) is cooled by coupling with the fuel and finally enters the working fluid pump (1); the fuel in the first cooler (7) absorbs the heat load of the carbon dioxide and its temperature rises, and then enters the preheater (2) to input part of the heat into the carbon dioxide in the preheater (2); the fuel at the fuel outlet of the preheater (2) enters the wall heat exchanger (4), absorbs heat and rises in temperature, and enters the fuel turbine (11) for heat-to-work conversion.

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