Carbon dioxide-to-Brayton cooling and power cogeneration system and method coupled with fuel latent heat

Abstract

The present invention discloses a carbon dioxide variable Brayton combined cooling and power generation system and method for coupling fuel latent heat, which includes a working fluid pump, a preheater, a recuperator, a wall heat exchanger, an expander, a generator, a cooler, a condenser, a compressor, a throttle valve, a fuel pump, a fuel turbine and a fuel storage tank; the condenser is one or two in series; the throttle valve is arranged on the pipeline connecting the fuel inlet of the condenser and the fuel outlet of the fuel storage tank, and is used to throttle and depressurize the fuel from the fuel storage tank to make the fuel reach the gas-liquid two-phase state, and the number of throttle valves is the same as and corresponds one by one to the number of condensers. The present invention uses the latent heat of the fuel to reduce the temperature of CO2 below the critical temperature, constructs a carbon dioxide variable Brayton combined cooling and power generation system to cool the high-temperature wall surface in a hypersonic vehicle, and uses the high-temperature heat load for power generation.

Description

Technical Field

[0001] The invention relates to the technical field of wall thermal protection, and in particular to a carbon dioxide-to-Brayton cooling and power cogeneration system and method coupled with fuel latent heat. Background Art

[0002] In the field of aircraft thermal protection technology, the fuselage and engine of the aircraft are heated by the high-temperature incoming flow during flight and generate a large amount of aerodynamic heat. The wall temperature is extremely high under the aerodynamic heating effect, which has a serious impact on the operation of the internal system of the aircraft. It is necessary to develop efficient wall cooling technology.

[0003] In addition, long flight time and reusability have become important technical directions for the development of future aircraft, which also puts higher requirements on the power generation capacity of aircraft. The development of efficient aircraft combined cooling and power supply systems has become one of the important contents of future aircraft development.

[0004] At present, fuel is the only available and limited cold source in aircraft. When fuel is used as a coolant, there is a temperature upper limit, that is, when the fuel temperature exceeds about 700°C, it is easy to cause coking and carbon deposition, which will block the wall cooling channel and weaken the cooling effect. In addition, the fuel is stored at room temperature in the tank, and the storage temperature is generally 293K. Therefore, the sensible heat of the fuel is limited. When the sensible heat of the fuel is used as the cold source heat sink in the aircraft combined cooling and power supply system, as the temperature of the aircraft wall increases, the fuel flow required for cooling the wall gradually increases, and even exceeds the fuel flow required for aircraft propulsion, resulting in a mass penalty. When the aircraft is in a high temperature environment, the storage temperature of the fuel in the tank rises, which further reduces the sensible heat sink of the fuel, and even makes it impossible to condense CO2, resulting in the problem of condensation difficulty in the combined cooling and power supply system based on the thermodynamic cycle.

[0005] CO2 has the characteristics of high density, large specific heat capacity and high thermal conductivity in the near-critical region. Using CO2 as the circulating working fluid in the combined cooling and power system and lowering the CO2 temperature to below the critical temperature is beneficial to reducing the system compression work and system volume.

[0006] The patent specification with publication number CN 115539216 A discloses a hypersonic vehicle integrated thermal management system based on the Brayton cycle, which uses fuel and carbon dioxide as coolants. The fuel absorbs the heat load of the equipment and then exchanges heat with the high-temperature carbon dioxide, and the heated fuel exchanges heat with the low-temperature carbon dioxide. The patented technology uses a regenerator to help improve the thermal efficiency of the cycle. Compared with the direct heat exchange of high and low temperature carbon dioxide in the traditional regenerator, the use of fuel as an intermediate medium reduces the temperature difference between the cold and hot fluids in the regenerator and avoids the pinch point problem in the regenerator.

[0007] The latent heat of vaporization of fuel is larger than the sensible heat. Considering that fuel is the only available cold source in the aircraft combined cooling and power system, and the storage temperature has a great influence on the condensation of CO2, using the latent heat of fuel after throttling as the cold source of the CO2 combined cooling and power system can reduce the initial temperature of the fuel and obtain a large amount of latent heat of vaporization, so that the fuel can condense CO2 to below the critical temperature, solving the problem of condensation difficulty in the aircraft combined cooling and power system and improving the thermal efficiency and power generation capacity of the system. Summary of the invention

[0008] In view of the above-mentioned technical problems and the shortcomings in the field, the present invention provides a carbon dioxide to Brayton combined cooling and power supply system and method coupled with fuel latent heat, which utilizes the latent heat of fuel to reduce the temperature of CO2 to below the critical temperature, constructs a CO2 to Brayton combined cooling and power supply system, and is used to cool the high-temperature wall surface in the hypersonic aircraft, and utilize the high-temperature heat load to generate electricity, thereby solving the combined cooling and power supply needs of the aircraft and the problem of difficulty in condensing the CO2 combined cooling and power supply system under limited fuel heat sink.

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

[0010] A carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat, comprising a working fluid pump, a preheater, a regenerator, a wall heat exchanger, an expander, a generator, a cooler, a condenser, a compressor, a throttle valve, a fuel pump, a fuel turbine and a fuel storage tank; the condenser is one or two connected in series; the throttle valve is arranged on a pipeline connecting the fuel inlet of the condenser and the fuel outlet of the fuel storage tank, and is used to throttle and reduce the pressure of the fuel from the fuel storage tank so that the fuel reaches a gas-liquid two-phase state, and the number of the throttle valves is consistent with the number of the condensers and corresponds one to one;

[0011] The working fluid pump, the preheater, the regenerator, the wall heat exchanger, the expander, the regenerator, the cooler, and the condenser are sequentially connected to form a carbon dioxide circulation loop;

[0012] The fuel storage tank, the throttle valve, the condenser, the compressor, and the wall heat exchanger are sequentially connected to form a first fuel pipeline;

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

[0014] 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.

[0015] The working medium of the carbon dioxide-to-Brayton combined cooling and power supply system coupled with fuel latent heat of the present invention is CO2; the fuel in the fuel storage tank is split at the outlet of the storage tank and connected to the throttle valve and the fuel pump respectively; a part of the fuel is throttled and depressurized through the throttle valve, and the other part of the fuel is pressurized through the fuel pump; the throttle valve is connected to the condenser, and the fuel absorbs the condensation heat load of CO2 in the condenser using latent heat, and then enters the compressor; the fuel pump is connected to the cooler, and the fuel exchanges heat with CO2 in the cooler, and then enters the preheater to re-input part of the heat into the CO2 at the outlet of the working fluid pump, and the fuel at the outlet of the preheater and the fuel at the outlet of the compressor enter the wall heat exchanger as coolants for the high-temperature wall to absorb the heat load of the high-temperature wall; the temperature and pressure of CO2 at the inlet of the working fluid pump are both lower than the critical point (critical temperature 304K, critical pressure 7.38MPa); the outlet of the working fluid pump is connected to the carbon dioxide inlet of the preheater, which is used to input the heat of the high-temperature fuel into CO2; the preheater carbon dioxide The carbon outlet is connected to the high-pressure side inlet of the regenerator; the high-pressure side outlet of the regenerator is connected to the inlet of the wall heat exchanger; CO2 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 outlet of the wall heat exchanger is connected to the inlet of the expander for converting CO2 into heat and work; the generator and the expander can be selected to be coaxial or non-coaxially connected according to the specific spatial layout of the system to convert the output work of the expander into electrical energy; the expander outlet is connected to the low-pressure side inlet of the regenerator for inputting the heat of CO2 at the expander outlet into the CO2 on the high-pressure side of the regenerator; the low-pressure side outlet of the regenerator is connected to the cooler and the condenser in sequence; the throttle valve is connected to the fuel storage tank for throttling and reducing the pressure of a part of the fuel from the fuel storage tank so that the fuel reaches a gas-liquid two-phase state; the fuel pump is used to pressurize another part of the fuel from the fuel storage tank to above the critical point pressure and then discharge it; the CO2 in the condenser exchanges heat with the fuel at the outlet of the throttle valve, and the CO2 is condensed using the latent heat of fuel vaporization and enters the working fluid pump. The fuel outlet of the condenser is connected to the compressor, and the fuel pressure is increased to a supercritical state through the compressor, but it is still lower than the fuel pressure flowing out of the preheater; the fuel in the cooler absorbs the heat load of CO2 and its temperature rises, and enters the preheater to input part of the heat into the CO2 in the preheater; the fuel flowing out of the preheater enters the wall heat exchanger, absorbs heat and heats up, and then enters the fuel turbine for heat-to-work conversion; the fuel flowing out of the compressor enters the wall heat exchanger, absorbs heat and heats up, and then directly enters the combustion chamber for combustion propulsion.

[0016] In a preferred example, in the carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat, the condenser and the throttle valve are both one.

[0017] In a preferred example, in the carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat, there are two condensers and two throttle valves, and the first fuel pipeline is branched before the two throttle valves and merges at the fuel outlets of the two condensers.

[0018] In a preferred example, in the carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat, the fuel from the fuel storage tank reaches a temperature lower than the CO2 condensation temperature after being throttled by the throttle valve, and then reaches a saturated gas phase state or a superheated gas state at the fuel outlet of the condenser after absorbing heat in the condenser; the fuel at the compressor outlet reaches a supercritical state;

[0019] The fuel from the fuel storage tank reaches a supercritical state at the fuel pump outlet; the fuel pressure at the fuel pump outlet is higher than the fuel pressure at the compressor outlet to avoid excessive load on the compressor.

[0020] In a preferred example, in the carbon dioxide-to-Brayton combined cooling and power system coupled with fuel latent heat, the flow channels of the wall heat exchanger include a flow channel using the fuel at the compressor outlet as the coolant, a flow channel using the fuel at the preheater fuel outlet as the coolant, and a flow channel using CO2 as the coolant. The three flow channels are fixedly embedded in the high-temperature wall that needs to be cooled, forming an integrated structure with the wall of the device that needs to be cooled.

[0021] Further preferably, 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 flight, and the heat of the wall surface is taken away by the fuel and CO2 in the flow channel, and the wall surface temperature is reduced, thereby achieving the purpose of cooling.

[0022] In a preferred example, in the coupled fuel latent heat carbon dioxide to Brayton cooling and power cogeneration system, the temperature of CO2 at the carbon dioxide outlet of the cooler is higher than the critical temperature (304K), and is condensed to below the critical temperature by the fuel in the condenser, and is a saturated or supercooled liquid at the carbon dioxide outlet of the condenser.

[0023] In a preferred embodiment, the temperature of the fuel in the 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.

[0024] In a preferred example, in the carbon dioxide to Brayton cooling and power cogeneration system coupled with fuel latent heat, the expander is a volumetric expander selected from a piston expander or a scroll expander.

[0025] The present invention also provides a method for converting carbon dioxide into Brayton cooling and power cogeneration by coupling the latent heat of fuel, wherein the method adopts the carbon dioxide into Brayton cooling and power cogeneration system by coupling the latent heat of fuel, wherein the condenser and the throttle valve are both one;

[0026] The carbon dioxide-to-Brayton cooling and power cogeneration method coupled with fuel latent heat comprises:

[0027] After a part of the fuel flowing out of the fuel storage tank is throttled by the throttle valve, the latent heat of the fuel is used as a low-temperature cold source for the condensation process in the CO2-to-Brayton system. The fuel absorbs the condensation heat load of CO2 in the condenser to form saturated gas, which is pressurized to a supercritical state by the compressor. The fuel at the outlet of the compressor enters the wall heat exchanger as a coolant for the high-temperature wall to absorb the heat load of the high-temperature wall, and then enters the combustion chamber for combustion propulsion.

[0028] Another part of the fuel flowing out of the fuel storage tank is pressurized to a supercritical state by the fuel pump and used as a cold source for the CO2 cooling process. It exchanges heat with CO2 in the cooler and then enters the preheater to re-input part of the heat into the CO2 flowing out of the working fluid pump. The fuel at the preheater fuel outlet enters the wall heat exchanger as a coolant for the high-temperature wall to absorb the heat load of the high-temperature wall. Then this part of the fuel enters the fuel turbine for expansion and heat-to-work conversion, thereby using the high-temperature fuel to generate electricity.

[0029] After being pressurized by the working fluid pump, CO2 absorbs heat and heats up in the preheater, regenerator and wall heat exchanger, and then enters the expander for heat-to-work conversion to output electrical energy. The CO2 at the expander outlet passes through the regenerator, cooler and condenser, is condensed and then enters the working fluid pump, completing a working cycle.

[0030] The present invention further provides a method for cogeneration of carbon dioxide to Brayton cooling and power by coupling the latent heat of fuel. The method adopts the cogeneration system of carbon dioxide to Brayton cooling and power by coupling the latent heat of fuel, wherein the condenser and the throttle valve are both two, and the first fuel pipeline is split before the two throttle valves and merges at the fuel outlets of the two condensers;

[0031] The carbon dioxide-to-Brayton cooling and power cogeneration method coupled with fuel latent heat comprises:

[0032] The fuel flowing out of the fuel storage tank is divided into three parts. One part of the fuel is throttled by the first throttle valve and its temperature is reduced to a state lower than the condensation temperature of carbon dioxide, and enters the first condenser to condense carbon dioxide to a saturated liquid state. One part of the fuel is throttled by the second throttle valve and its temperature is reduced to a state lower than the carbon dioxide outlet temperature of the second condenser, and enters the second condenser to further reduce the temperature of the saturated liquid phase carbon dioxide at the carbon dioxide outlet of the first condenser to a supercooled liquid phase state. Another part of the fuel is pressurized to a supercritical state by the fuel pump and then enters the cooler.

[0033] After absorbing heat in the first condenser and the second condenser, the fuel reaches a saturated liquid state. The fuel flowing out of the first condenser and the second condenser is mixed and then enters the compressor to be pressurized to a supercritical pressure, and then enters the wall heat exchanger to absorb the heat load as a wall coolant. Finally, after flowing out of the fuel outlet of the wall heat exchanger, it directly enters the combustion chamber for combustion propulsion;

[0034] The fuel flowing out of the cooler has a high temperature after absorbing heat, and enters the preheater to input part of the heat into the CO2 in the preheater; the fuel outlet of the preheater is connected to the wall heat exchanger, and the fuel flowing out of the preheater absorbs heat and heats up in the wall heat exchanger, and then enters the fuel turbine for heat-to-work conversion to output electrical energy;

[0035] After being pressurized by the working fluid pump, CO2 absorbs heat and heats up in the preheater, regenerator and wall heat exchanger, and then enters the expander for heat-to-work conversion to output electrical energy. The CO2 at the expander outlet passes through the regenerator, cooler, first condenser and second condenser, and then enters the working fluid pump after being condensed, completing a working cycle.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] 1. The present invention proposes a CO2-to-Brayton cycle combined cooling and power supply system and method that couples the latent heat of fuel, utilizes the latent heat after fuel throttling to achieve the condensation of CO2, constructs a CO2-to-Brayton cycle combined cooling and power supply system, and solves the current condensation difficulty problem in the aircraft combined cooling and power supply system under the background of limited fuel heat sink.

[0038] 2. The CO2-to-Brayton cooling and power cogeneration system and method coupled with fuel latent heat proposed in the present invention adopts a fuel diversion method to improve the heat exchange matching between fuel and CO2, thereby reducing the fuel flow required for the CO2 cooling and condensation process. Compared with the CO2-to-Brayton cycle using the sensible heat of the fuel, the CO2-to-Brayton cooling and power cogeneration system coupled with fuel latent heat proposed in the present invention can increase the flow ratio of CO2 to fuel in the system from 0.15 to 1.14, and reduce the average heat exchange temperature difference of the cooling process by 106K. The efficient use of the fuel heat sink can reduce the mass penalty problem caused by carrying too much cooling fuel for the aircraft, which is in line with the lightweight and compact development of hypersonic aircraft.

[0039] The flow ratio is defined as follows:

[0040]

[0041] in, is the mass flow rate of CO2, in kg / s; q m,f is the mass flow rate of fuel, in kg / s.

[0042] 3. The CO2-to-Brayton cooling and power cogeneration system and method coupled with fuel latent heat proposed in the present invention realizes the condensation of CO2 under the background of limited fuel heat sink, reduces the compression work of CO2, and increases the further coupling between fuel and CO2 in the preheater, so that the working capacity of CO2 in the expander is improved. Under the condition of fuel storage temperature of 318K and high temperature wall temperature in the range of 950-1600K, compared with the traditional CO2 recuperation Brayton cycle, the unit mass working fluid power generation of the CO2-to-Brayton cooling and power cogeneration system coupled with fuel latent heat is increased by 1.6%-12.0%, while reducing the temperature of the fuel entering the wall heat exchanger and improving the cooling capacity of the fuel.

[0043] 4. The CO2-to-Brayton cooling and power cogeneration system and method coupled with fuel latent heat proposed in the present invention further diverts the fuel at the condenser inlet, and absorbs the CO2 heat load in the first condenser and the second condenser respectively after throttling and cooling the fuel, thereby improving the supercooling degree of CO2 at the working fluid pump inlet and optimizing the heat exchange matching of CO2 and fuel; improving the problem of large fuel flow consumption and heat exchange mismatch with CO2 in a single condenser when the CO2 supercooling degree is large; increasing the further coupling of fuel and CO2 in the preheater, so that the work capacity of CO2 in the expander is improved. Under the condition of fuel storage temperature of 318K, the high temperature wall temperature is in the range of 950-1600K. Compared with the traditional CO2 reheating Brayton cycle, the unit mass working fluid power generation of the CO2-to-Brayton cooling and power cogeneration system coupled with fuel latent heat is increased by 5.6%-21.5%, while reducing the temperature of the fuel entering the wall heat exchanger, and improving the cooling capacity of the fuel. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 The CO2-to-Brayton cooling and power cogeneration system coupled with fuel latent heat and its working process diagram of Example 1;

[0045] Figure 2 This is a flow rate ratio variation diagram of the condenser and cooler of the CO2-to-Brayton combined cooling and power system of Example 1;

[0046] Figure 3 A comparison chart of the power generation per unit mass of working fluid in the CO2-to-Brayton combined cooling and power system of Example 1;

[0047] Figure 4 This is a graph showing the change in thermal efficiency of the CO2-to-Brayton combined cooling and power system of Example 1 at different fuel storage temperatures;

[0048] Figure 5 A schematic diagram of a CO2-to-Brayton cooling and power cogeneration system and its workflow coupled with fuel latent heat in Example 2;

[0049] Figure 6 This is a comparison chart of the power generation per unit mass of working fluid in the CO2-to-Brayton combined cooling and power system of Example 2. DETAILED DESCRIPTION

[0050] 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.

[0051] Example 1

[0052] 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 lowest temperature of CO2 in the cycle can reduce the power consumption of the compression process and improve the cooling capacity of CO2 on the high-pressure side. The CO2-to-Brayton system that uses the sensible heat of the fuel to condense CO2 consumes a large amount of fuel flow in the condensation process and has high requirements for the storage temperature of the fuel. When the fuel storage temperature is higher than the CO2 condensation temperature, the fuel cannot meet the condensation requirements of the CO2-to-Brayton combined cooling and power system, that is, there is a problem of condensation difficulty.

[0053] This embodiment adopts Figure 1 In the fuel splitting method shown, since the fuel absorbs heat to generate cracked gas containing many components, the calculation of its flow and thermodynamic characteristics is complicated, n-decane is generally used instead, so in this embodiment, n-decane is used instead of fuel for analysis. CO2 is condensed by using the latent heat of the fuel, and CO2 is cooled by using the sensible heat of the fuel. When the temperature of CO2 is reduced in the cooler 7, it enters the condenser 8 and transfers the heat load to the fuel in a two-phase state, realizing a variable Brayton cycle.

[0054] A carbon dioxide-to-Brayton cooling and power system coupled with fuel latent heat, such as 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 cooler 7, a condenser 8, a compressor 12, a throttle valve 10, a fuel pump 11, a fuel turbine 13 and a fuel storage tank 9.

[0055] The throttle valve 10 is arranged on the pipeline connecting the fuel inlet of the condenser 8 and the fuel outlet of the fuel storage tank 9, and is used to throttle and reduce the pressure of the fuel from the fuel storage tank 9 so that the fuel reaches a gas-liquid two-phase state.

[0056] The working fluid pump 1, the preheater 2, the regenerator 3, the wall heat exchanger 4, the expander 5, the regenerator 3, the cooler 7, and the condenser 8 are sequentially connected to form a carbon dioxide circulation loop.

[0057] The fuel storage tank 9, the throttle valve 10, the condenser 8, the compressor 12, and the wall heat exchanger 4 are sequentially connected to form a first fuel pipeline.

[0058] The fuel storage tank 9, the fuel pump 11, the cooler 7, the preheater 2, the wall heat exchanger 4, and the fuel turbine 11 are connected in sequence to form a second fuel pipeline.

[0059] 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.

[0060] The fuel from the fuel storage tank 9 reaches a temperature lower than the condensation temperature of CO2 after being throttled by the throttle valve 10, and then reaches a saturated gas phase state or a superheated gas state at the fuel outlet of the condenser 8 after absorbing heat in the condenser 8. The fuel at the outlet of the compressor 12 reaches a supercritical state.

[0061] The fuel from the fuel storage tank 9 reaches a supercritical state at the outlet of the fuel pump 11 .

[0062] The fuel pressure at the outlet of the fuel pump 11 is higher than the fuel pressure at the outlet of the compressor 12 .

[0063] The flow channels of the wall heat exchanger 4 include a flow channel using the fuel at the outlet of the compressor 12 as a coolant, a flow channel using the fuel at the fuel outlet of the preheater 2 as a coolant, and a flow channel using CO2 as a coolant. The three flow channels are fixedly embedded in the high-temperature wall that needs to be cooled, forming an integrated structure with the wall of the device that needs to be cooled.

[0064] The high temperature wall surface may be 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 flight, and the heat of the wall surface is taken away by the fuel and CO2 in the flow channel, and the wall surface temperature is reduced, thereby achieving the purpose of cooling.

[0065] The temperature of CO2 at the carbon dioxide outlet of the cooler 7 is higher than the critical temperature, and is condensed by the fuel to below the critical temperature in the condenser 8. At the carbon dioxide outlet of the condenser 8, CO2 is in a saturated or supercooled liquid state.

[0066] The expander 5 may be a volumetric expander, and may be specifically selected from a piston expander or a scroll expander.

[0067] The method for coupling fuel latent heat with carbon dioxide to Brayton cooling and power cogeneration by using the above-mentioned fuel latent heat coupled carbon dioxide to Brayton cooling and power cogeneration system comprises:

[0068] After a part of the fuel flowing out of the fuel storage tank 9 is throttled by the throttle valve 10, the latent heat of the fuel is used as a low-temperature cold source for the condensation process in the CO2-to-Brayton system. The fuel absorbs the condensation heat load of CO2 in the condenser 8 to form a saturated gas, which is pressurized to a supercritical state by the compressor 12. The fuel at the outlet of the compressor 12 enters the wall heat exchanger 4 as a coolant for the high-temperature wall to absorb the heat load of the high-temperature wall, and then enters the combustion chamber for combustion propulsion.

[0069] Another part of the fuel flowing out of the fuel storage tank 9 is pressurized to a supercritical state by the fuel pump 11 and serves as a cold source for the CO2 cooling process. It exchanges heat with the CO2 in the cooler 7 and then enters the preheater 2 to re-input part of the heat into the CO2 flowing out of the working fluid pump 1. The fuel at the fuel outlet of the preheater 2 enters the wall heat exchanger 4 as a coolant for the high-temperature wall to absorb the heat load of the high-temperature wall. Then, this part of the fuel enters the fuel turbine 13 for expansion and heat-to-work conversion, thereby utilizing the high-temperature fuel to generate electricity.

[0070] After being pressurized by the working fluid pump 1, CO2 absorbs heat and heats up in the preheater 2, the regenerator 3 and the wall heat exchanger 4, and then enters the expander 5 for heat-to-work conversion to output electrical energy. The CO2 at the outlet of the expander 5 passes through the regenerator 3, the cooler 7 and the condenser 8, and then enters the working fluid pump 1 after being condensed, completing a working cycle.

[0071] like Figure 2 As shown, when the storage temperature of the fuel in the storage tank increases, the fuel flow required to cool CO2 increases, and the flow ratio in the cooler 7 and the condenser 8 decreases. Compared with the CO2-to-Brayton combined cooling and power system using the sensible heat of the fuel, the CO2-to-Brayton combined cooling and power system coupled with the latent heat of the fuel proposed in this embodiment, when the fuel storage temperature increases from 293K to 298K, the flow ratio of carbon dioxide to fuel in the condenser increases from 0.15 to 1.96; as the fuel storage temperature gradually increases, the CO2-to-Brayton combined cooling and power system using the sensible heat of the fuel can no longer achieve the condensation of CO2, but the CO2-to-Brayton combined cooling and power system coupled with the latent heat of the fuel proposed in the present invention can adapt to higher fuel storage temperatures, and can achieve the condensation of CO2 within the fuel storage temperature range of 293 to 333K. The flow ratio in the condenser increases from 0.15 to 1.96 and then decreases to 1.52. Compared with the CO2-to-Brayton combined cooling and power system using the sensible heat of the fuel, it still has advantages in reducing fuel flow consumption.

[0072] like Figure 3 As shown, the CO2-to-Brayton combined cooling and power generation system coupled with fuel latent heat of Example 1 has significantly reduced compression work compared to the traditional Brayton system. By increasing the coupling process between the fuel and CO2 in the preheater, the work capacity of CO2 in the expander is improved. In the range of fuel storage temperature of 293 to 318K, the power generation capacity of the CO2-to-Brayton combined cooling and power generation system coupled with fuel latent heat proposed in this embodiment has advantages. Under the condition that the fuel storage temperature is 318K, the high-temperature wall temperature is in the range of 950 to 1600K, and the power generation per unit mass of working fluid of the system in this embodiment is increased by 1.6% to 12.0% compared with the traditional reheat Brayton system.

[0073] like Figure 4As shown, when the fuel storage temperature is between 293 and 318 K, the thermal efficiency of the CO2 variable Brayton cooling and power system coupled with the fuel latent heat of Example 1 is improved by 0.05% to 14.62% compared with the traditional regenerative Brayton system. When the fuel storage temperature increases from 293 K to 298 K, the additional compression work of the fuel causes the thermal efficiency of the variable Brayton system to decrease from 32.8% to 19.2%, but it still has an advantage over the regenerative Brayton system.

[0074] Example 2

[0075] Increasing the subcooling degree of CO2 at the inlet of the working fluid pump 1 can further reduce the compression work of CO2, but the temperature requirement of the fuel will also increase accordingly. When the subcooling degree of CO2 is large, the required temperature of the fuel after throttling is further reduced, and the heat exchange between the two-phase fuel and the supercooled liquid CO2 directly increases the fuel flow consumption and the heat exchange matching becomes worse.

[0076] In view of the fact that the degree of supercooling of CO2 is relatively large, the present invention proposes a carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to Example 2, which is similar to Example 1. Figure 4 As shown, the difference is that there are two condensers and two throttle valves, and the first fuel pipeline is divided before the two throttle valves and merged at the fuel outlets of the two condensers.

[0077] The working process is roughly similar to that of Example 1, specifically:

[0078] The fuel flowing out of the fuel storage tank 9 is divided into three parts. One part of the fuel is throttled by the first throttle valve 10 and its temperature is reduced to more than 1°C lower than the condensation temperature of carbon dioxide, and enters the first condenser 8 to condense carbon dioxide to a saturated liquid state. One part of the fuel is throttled by the second throttle valve 14 and its temperature is reduced to a temperature lower than the carbon dioxide outlet temperature of the second condenser 15, and enters the second condenser 15 to further cool the saturated liquid phase carbon dioxide at the carbon dioxide outlet of the first condenser 8 to a supercooled liquid phase state. Another part of the fuel is pressurized to a supercritical state by the fuel pump 11 and then enters the cooler 7.

[0079] The fuel reaches a saturated liquid state after absorbing heat in the first condenser 8 and the second condenser 15. The fuel flowing out of the first condenser 8 and the second condenser 15 is mixed and then enters the compressor 12 to be pressurized to a supercritical pressure, and then enters the wall heat exchanger 4 to absorb the heat load as a wall coolant, and finally flows out of the fuel outlet of the wall heat exchanger 4 and directly enters the combustion chamber for combustion propulsion;

[0080] The fuel flowing out of the cooler 7 has a high temperature after absorbing heat, and enters the preheater 2 to input part of the heat into the CO2 in the preheater 2; the fuel outlet of the preheater 2 is connected to the wall heat exchanger 4, and the fuel flowing out of the preheater 2 absorbs heat and heats up in the wall heat exchanger 4, and then enters the fuel turbine 13 for heat-to-work conversion to output electrical energy;

[0081] After being pressurized by the working fluid pump 1, CO2 absorbs heat and heats up in the preheater 2, the regenerator 3 and the wall heat exchanger 4, and then enters the expander 5 for heat-to-work conversion to output electrical energy. The CO2 at the outlet of the expander 5 passes through the regenerator 3, the cooler 7, the first condenser 8 and the second condenser 15, and after being condensed, enters the working fluid pump 1, completing a working cycle.

[0082] like Figure 5 As shown, the CO2-to-Brayton cooling and power cogeneration system coupled with fuel latent heat of Example 2 increases the supercooling degree of CO2 at the inlet of the working fluid pump in order to further reduce the CO2 compression work. In order to ensure the heat exchange matching of CO2 and fuel at the same time, Example 2 adds a second condenser 15 and splits the fuel again. After the split, a part of the fuel condenses CO2 into a saturated liquid state in the first condenser 8, and a part of the fuel enters the second condenser 15 to cool the CO2 from a saturated liquid state to a supercooled liquid state.

[0083] like Figure 6 As shown, after further reducing the compression work of CO2, the CO2-to-Brayton cooling and power cogeneration system coupled with the latent heat of fuel proposed in this embodiment further diverts the fuel at the condenser inlet, while improving the CO2 supercooling and optimizing the heat exchange matching between CO2 and fuel, further improving the power generation capacity of the system. Under the condition that the fuel storage temperature is 318K and the high temperature wall temperature is in the range of 950-1600K, the power generation per unit mass of the working fluid in Example 2 is increased by 5.6%-21.5% compared with the traditional regenerative Brayton system.

[0084] 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 cogeneration system coupled with fuel latent heat, characterized in that: The invention comprises a working fluid pump (1), a preheater (2), a regenerator (3), a wall heat exchanger (4), an expander (5), a generator (6), a cooler (7), a condenser, a compressor (12), a throttle valve, a fuel pump (11), a fuel turbine (13) and a fuel storage tank (9); the condenser is one or two condensers connected in series; the throttle valve is arranged on a pipeline connecting the fuel inlet of the condenser and the fuel outlet of the fuel storage tank (9), and is used to throttle and reduce the pressure of the fuel from the fuel storage tank (9) so that the fuel reaches a gas-liquid two-phase state; the number of the throttle valves is consistent with the number of the condensers and corresponds one to one; A working fluid pump (1), a preheater (2), a regenerator (3), a wall heat exchanger (4), an expander (5), a regenerator (3), a cooler (7), and the condenser are sequentially connected to form a carbon dioxide circulation loop; The fuel storage tank (9), the throttle valve, the condenser, the compressor (12), and the wall heat exchanger (4) are sequentially connected to form a first fuel pipeline; A fuel storage tank (9), a fuel pump (11), a 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 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 cogeneration system coupled with fuel latent heat according to claim 1, characterized in that: There are two condensers and two throttle valves, and the first fuel pipeline is split before the two throttle valves and merges at the fuel outlets of the two condensers.

3. The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to claim 1, characterized in that: The fuel from the fuel storage tank (9) reaches a temperature lower than the condensation temperature of CO2 after being throttled by the throttle valve, and then reaches a saturated gas phase state or a superheated gas state at the fuel outlet of the condenser after absorbing heat in the condenser; the fuel at the outlet of the compressor (12) reaches a supercritical state; The fuel from the fuel storage tank (9) reaches a supercritical state at the outlet of the fuel pump (11); the fuel pressure at the outlet of the fuel pump (11) is higher than the fuel pressure at the outlet of the compressor (12).

4. The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to claim 1, characterized in that: The flow channel of the wall heat exchanger (4) includes a flow channel using the fuel at the outlet of the compressor (12) as a coolant, a flow channel using the fuel at the fuel outlet of the preheater (2) as a coolant, and a flow channel using CO2 as a coolant. The three 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.

5. The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to claim 4, characterized in that: The high-temperature wall surface is an aircraft engine wall surface and / or an aircraft head wall surface.

6. The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to claim 1, characterized in that: The temperature of CO2 at the carbon dioxide outlet of the cooler (7) is higher than the critical temperature, and is condensed by the fuel to below the critical temperature in the condenser, and is in a saturated or supercooled liquid state at the carbon dioxide outlet of the condenser.

7. The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat according to claim 1, characterized in that: The fuel in the 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).

8. A method for cogeneration of carbon dioxide into Brayton cooling and power by coupling fuel latent heat, characterized in that: The carbon dioxide-to-Brayton cooling and power cogeneration system coupled with fuel latent heat as claimed in claim 1 is used, and both the condenser and the throttle valve are one; The carbon dioxide-to-Brayton cooling and power cogeneration method coupled with fuel latent heat comprises: A portion of the fuel flowing out of the fuel storage tank (9) is throttled by a throttle valve (10), and the latent heat of the fuel is used as a low-temperature cooling source for the condensation process in the CO2-to-Brayton system. The fuel absorbs the condensation heat load of CO2 in the condenser (8) to form a saturated gas, which is pressurized to a supercritical state by a compressor (12); the fuel at the outlet of the compressor (12) enters the wall heat exchanger (4) as a coolant for the high-temperature wall surface to absorb the heat load of the high-temperature wall surface, and then enters the combustion chamber for combustion propulsion; Another part of the fuel flowing out of the fuel storage tank (9) is pressurized to a supercritical state by the fuel pump (11) and then used as a cold source for the CO2 cooling process, and then exchanges heat with the CO2 in the cooler (7), and then enters the preheater (2) to re-input part of the heat into the CO2 flowing out of the working fluid pump (1); the fuel at the fuel outlet of the preheater (2) enters the wall heat exchanger (4) as a coolant for the high-temperature wall surface to absorb the heat load of the high-temperature wall surface, and then this part of the fuel enters the fuel turbine (13) for expansion and heat-to-work conversion, thereby using the high-temperature fuel to generate electricity; After being pressurized by the working fluid pump (1), CO2 absorbs heat and is heated in the preheater (2), the regenerator (3) and the wall heat exchanger (4), and then enters the expander (5) for heat-work conversion to output electrical energy. The CO2 at the outlet of the expander (5) passes through the regenerator (3), the cooler (7) and the condenser (8), and then enters the working fluid pump (1) after being condensed, completing a working cycle.

9. A method for cogeneration of carbon dioxide into Brayton cooling and power by coupling fuel latent heat, characterized in that: A carbon dioxide-to-Brayton cooling and power cogeneration system coupling fuel latent heat as described in claim 2; The carbon dioxide-to-Brayton cooling and power cogeneration method coupled with fuel latent heat comprises: The fuel flowing out of the fuel storage tank (9) is divided into three parts. One part of the fuel is throttled by the first throttle valve (10) and its temperature is reduced to a state lower than the condensation temperature of carbon dioxide, and enters the first condenser (8) to condense the carbon dioxide to a saturated liquid state. One part of the fuel is throttled by the second throttle valve (14) and its temperature is reduced to a state lower than the carbon dioxide outlet temperature of the second condenser (15), and enters the second condenser (15) to further reduce the temperature of the saturated liquid phase carbon dioxide at the carbon dioxide outlet of the first condenser (8) to a supercooled liquid phase state. Another part of the fuel is pressurized to a supercritical state by the fuel pump (11) and then enters the cooler (7). After absorbing heat in the first condenser (8) and the second condenser (15), the fuel reaches a saturated liquid phase state. The fuel flowing out of the first condenser (8) and the second condenser (15) is mixed and then enters the compressor (12) to be pressurized to a supercritical pressure, and then enters the wall heat exchanger (4) to absorb the heat load as a wall coolant. Finally, after flowing out of the fuel outlet of the wall heat exchanger (4), it directly enters the combustion chamber for combustion propulsion; The fuel flowing out of the cooler (7) has a relatively high temperature after absorbing heat, and enters the preheater (2) to input part of the heat into the CO2 in the preheater (2); the fuel outlet of the preheater (2) is connected to the wall heat exchanger (4), and the fuel flowing out of the preheater (2) absorbs heat and rises in temperature in the wall heat exchanger (4), and then enters the fuel turbine (13) for heat-to-work conversion to output electrical energy; After being pressurized by the working fluid pump (1), CO2 absorbs heat and increases in temperature in the preheater (2), the regenerator (3) and the wall heat exchanger (4), and then enters the expander (5) for heat-work conversion to output electrical energy. The CO2 at the outlet of the expander (5) passes through the regenerator (3), the cooler (7), the first condenser (8) and the second condenser (15), and then enters the working fluid pump (1) after being condensed, completing a working cycle.

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