Dual-fuel scramjet engine with energy gradient utilization and ammonia fuel cell power generation

Abstract

The invention provides an ammonia fuel cell power generation dual-fuel scramjet engine capable of achieving energy gradient utilization, belongs to the technical field of aircraft thermal protection and power generation, and solves the problems that a traditional airborne power generation system is difficult to use due to the high incoming flow Mach number in hypersonic flight, and coking is caused in a regeneration cooling channel of a fuel decomposition gas turbine. Ammonia and aviation kerosene generate high-temperature fuel gas in a combustion chamber of the scramjet engine to push the engine to generate thrust; high-temperature waste heat of the combustion chamber is recycled through the regeneration cooling channel, fuel is heated, a part of ammonia is decomposed, and decomposed gas drives a turbine generator to generate electric energy. According to the power generation system for gradient utilization of energy, factors such as actual use temperature and pressure are fully considered, the energy utilization efficiency is effectively improved, energy waste is reduced, and reasonable adaptation of energy is achieved, so that the power generation efficiency of the whole system is improved, and the electric energy requirement of a hypersonic aircraft is greatly met.

Description

Technical Field

[0001] The present invention belongs to the technical field of aircraft thermal protection and power generation, and in particular relates to a dual-fuel scramjet engine that generates electricity using an ammonia fuel cell with cascaded energy utilization. Background Art

[0002] Current experiments with ramjet engines rely on batteries, which have very limited power. To meet the megawatt-level power demands of future hypersonic vehicles, a suitable airborne power generation system is needed. Fuel cells, with their generally high energy efficiency, can meet the need for high-power airborne power generation. Solid oxide fuel cells (SOFCs), with their high operating temperatures and wide range of fuel sources, are highly compatible with the scramjet operating environment. Their simple structure without rotating parts also makes SOFCs feasible for airborne power generation.

[0003] SOFC is an all-solid-state medium- and high-temperature fuel cell with high energy conversion efficiency exceeding 60%, and can achieve efficiency exceeding 80% in combined heat and power generation. SOFC's outstanding advantages include its wide applicability, enabling it to generate power from a variety of fuels, including natural gas, hydrogen, and alcohols, without the need for expensive precious metal catalysts. Therefore, SOFC is a key strategic reserve technology for developed countries worldwide.

[0004] In line with global decarbonization trends, various zero-carbon aircraft powered by ammonia-fueled internal combustion engines, turbines, or fuel cells have been extensively studied. Scramjets represent the next generation of flight technology, but research in this area is still in its early stages and lacks widespread implementation.

[0005] Ammonia has a higher volumetric energy density than hydrogen, making it easier to store and transport. In addition to being a carbon-free hydrogen carrier, ammonia's decomposition to produce hydrogen has become a highly sought-after research direction in the fuel cell field. Furthermore, ammonia can absorb heat and decompose in the regenerative cooling channel to cool the engine while effectively improving the coking problem in the cooling channel. Furthermore, ammonia fuel is also suitable for SOFC. Within the operating temperature range of 700-900°C, the power generation efficiency of ammonia-fueled SOFC is close to that of hydrogen fuel. However, the application of SOFC needs to consider factors such as the actual operating temperature and pressure. Summary of the Invention

[0006] In light of this, to address the challenges of using traditional airborne power generation systems during hypersonic flight due to the high Mach number of the incoming airflow, as well as the problem of coking in the regenerative cooling duct of the fuel decomposition gas turbine, the present invention provides a dual-fuel scramjet engine utilizing energy cascade utilization, using ammonia fuel cells for power generation. This system uses a turbine to drive a generator and compressor, ensuring that the working fluid meets the operating environment requirements of the SOFC. The products of ammonia decomposition in the regenerative cooling duct are used to generate fuel cell power. This energy cascade power generation system fully considers factors such as actual operating temperature and pressure, effectively improving energy utilization efficiency, reducing energy waste, and achieving optimal energy adaptation, thereby increasing the overall system's power generation efficiency and significantly meeting the power needs of hypersonic vehicles.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: a dual-fuel scramjet engine that generates electricity using an ammonia fuel cell with cascaded energy utilization, comprising an ammonia fuel tank, an aviation kerosene fuel tank, a precooler, a regenerative cooling channel, an ammonia decomposition gas turbine, a compressor, a solid oxide fuel cell, and a motor. The scramjet engine includes a regenerative cooling channel, a fuel injector, an air inlet, an isolating section, a combustion chamber, and a nozzle, wherein the air inlet, isolating section, combustion chamber, and nozzle are arranged in sequence. The feed port of the precooler is connected to the fuel tank, the discharge port of the precooler and the outlet of the fuel tank are respectively connected to the regeneration cooling channel, a part of the outlet of the regeneration cooling channel is connected to the fuel injector, the fuel is injected into the combustion chamber and mixed with the compressed air in the intake duct for combustion, and the high-temperature combustion gas expands in the tail nozzle to generate thrust, and the other part is connected to the ammonia decomposition gas turbine, the ammonia decomposition gas turbine is connected to the motor, the outlet of the ammonia decomposition gas turbine is connected to the anode of the solid oxide fuel cell, the compressor is connected to the cathode of the solid oxide fuel cell, the ammonia and the cathode gas undergo an oxidation-reduction reaction to generate electrical energy.

[0008] Furthermore, the exhaust gas of the solid oxide fuel cell is returned to the combustion chamber through a fuel injector.

[0009] Furthermore, the regenerative cooling channel is a parallel pipeline with a microchannel structure, part of the pipeline is passed through ammonia, and part of the pipeline is passed through aviation kerosene. The ammonia is decomposed in the regenerative cooling channel and used as the anode working fluid of the fuel cell, and the aviation kerosene is decomposed in the regenerative cooling channel and returned to the combustion chamber for combustion.

[0010] Furthermore, the compressor takes the air after passing through the precooler so that the temperature and pressure of the air meet the working conditions for entering the cathode of the solid oxide fuel cell.

[0011] Furthermore, the operating conditions of the cathode of the solid oxide fuel cell are a temperature of 800-1000K and a pressure of 1 MPa.

[0012] Furthermore, the ammonia decomposition gas turbine takes the ammonia decomposition gas from the outlet of the regeneration cooling channel, so that the ammonia decomposition gas meets the working conditions for entering the anode of the solid oxide fuel cell.

[0013] Furthermore, the operating conditions of the solid oxide fuel cell anode are a temperature of 800-1000K and a pressure of 1 MPa.

[0014] Furthermore, the ammonia fuel in the ammonia fuel tank can be used as a cold source, and is used to cool the high-temperature air taken out from the air intake through a precooler. The cooled air is passed into the compressor to meet the working conditions of the solid oxide fuel cell, and then passed into the cathode of the solid oxide fuel cell.

[0015] Furthermore, the ammonia mixed fuel decomposed by the precooler and the jet fuel in the jet fuel tank are respectively introduced into the regeneration cooling channel to regenerate and cool the scramjet engine combustion chamber. Part of the cooled ammonia fuel is introduced into the ammonia decomposition gas turbine, the ammonia decomposition gas turbine is connected to the motor, and the outlet of the ammonia decomposition gas turbine is introduced into the solid oxide fuel cell anode.

[0016] Furthermore, the wall surface of the regeneration cooling channel is provided with high-energy metal powder or coated with a catalyst. Compared with the prior art, the dual-fuel scramjet engine for power generation using ammonia fuel cells with cascaded energy utilization according to the present invention has the following beneficial effects: 1. The present invention provides a system for cascaded energy utilization. This cascaded energy utilization is embodied in the following: ammonia and jet fuel generate high-temperature combustion gases in the scramjet engine combustion chamber, driving the engine to generate thrust; simultaneously, the high-temperature waste heat from the combustion chamber is recovered through a regenerative cooling channel, heating the fuel and causing a portion of the ammonia to decompose. The decomposed gas drives a turbine generator to generate electricity. Furthermore, before entering the regenerative cooling channel, the ammonia fuel passes through a precooler to cool the intake air, reducing the compressor load while increasing its own temperature, further facilitating decomposition. Subsequently, the precooled and compressed air and decomposed gas enter the solid oxide fuel cell, respectively, for electrochemical reactions to generate electricity. This is the efficient conversion of the fuel's chemical energy into electricity. Finally, the exhaust gas generated by the fuel cell is directed back to the combustion chamber for further combustion, recovering the residual energy. This effectively improves energy utilization efficiency, reduces energy waste, and achieves reasonable energy adaptation, thereby improving the power generation efficiency of the entire system and significantly meeting the power requirements of hypersonic aircraft. 2. This invention aims to reduce carbon emissions without changing the specific thrust of the scramjet engine by using a mixed fuel. Using ammonia fuel, which has a high heat sink capacity, in the regenerative cooling channels can improve the thermal protection performance of the scramjet. This is because ammonia fuel has a higher combustion temperature and heat absorption capacity, effectively absorbing and dissipating heat generated by high-temperature components, improving the system's thermal protection. Furthermore, using ammonia fuel can significantly alleviate the coking problem in the cooling channels caused by the use of hydrocarbon fuels. Hydrocarbon fuels produce deposits such as carbides during combustion, which can cause cooling channel blockage and reduce heat exchanger efficiency. Using ammonia fuel can reduce the degree of coking, reduce the risk of cooling channel blockage, and improve system reliability and maintainability. However, ammonia currently suffers from a low calorific value. To avoid the impact of using only ammonia on the specific impulse of the scramjet engine, this system uses a dual fuel of ammonia and jet fuel. This system solution effectively alleviates the coking problem in the cooling channels while meeting the thrust requirements of the hypersonic vehicle and significantly meeting the global decarbonization trend. Therefore, the combined power generation system of the ammonia / jet fuel dual-fuel scramjet engine aims to reduce carbon emissions and improve the system's thermal protection performance and reliability, thereby enhancing the system's environmental friendliness and operating efficiency by mixing fuels and using ammonia fuel.

[0017] 3. In the system of the present invention, the ammonia cooling channel in the parallel piping of the regenerative cooling channel adopts a microchannel ammonia decomposition reactor design. A microchannel ammonia decomposition reactor is a device that uses a microchannel structure to decompose ammonia. It can achieve efficient ammonia decomposition reaction within a small channel. At the same time, the compact design improves system integration and efficiency, reducing system weight and space usage.

[0018] 4. To further improve the efficiency of the ammonia decomposition reaction, high-energy metal powders or catalysts can be added to the cooling channels. These high-energy metal powders or catalysts act as catalysts, promoting the decomposition of ammonia during the reaction, thereby increasing the efficiency of the ammonia decomposition reaction. By increasing the efficiency of the ammonia decomposition reaction, the power generation efficiency of the solid oxide fuel cell can be increased. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The accompanying drawings, which constitute part of the present invention, are provided to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are provided to explain the present invention and do not constitute an undue limitation of the present invention. In the accompanying drawings: Figure 1 A schematic diagram of a dual-fuel scramjet engine using an ammonia fuel cell for power generation using cascaded energy utilization according to an embodiment of the present invention; Figure 2 This is a schematic diagram of the regenerative cooling channel structure according to an embodiment of the present invention.

[0020] Explanation of the reference numerals: 1-ammonia fuel tank, 2-jet fuel tank, 3-precooler, 4-regeneration cooling channel, 5-ammonia decomposition gas turbine, 6-compressor, 7-solid oxide fuel cell, 8-fuel injector, 9-air inlet, 10-isolation section, 11-combustion chamber, 12-tail nozzle, 13-scramjet engine, 14-air intake, 15-ammonia decomposition gas-generator, 16-jet fuel pump. DETAILED DESCRIPTION

[0021] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely explain the technical solutions in the embodiments of the present invention. It should be noted that the embodiments of the present invention and the features therein can be combined with each other in the absence of conflict, and the embodiments described are only part of the embodiments of the present invention, not all of the embodiments.

[0022] See also Figure 1-2 This embodiment is described as follows. Figure 1 As shown, a dual-fuel scramjet engine that generates electricity using an ammonia fuel cell with energy cascade utilization includes an ammonia fuel tank 1, an aviation kerosene fuel tank 2, a precooler 3, a regenerative cooling channel 4, an ammonia decomposition gas turbine 5, a compressor 6, a solid oxide fuel cell 7, an air intake 14, a motor 15 and an aviation kerosene fuel pump 16. The scramjet engine 13 includes a regenerative cooling channel 4, a fuel injector 8, an air inlet 9, an isolating section 10, a combustion chamber 11 and a nozzle 12. The air inlet 9, the isolating section 10, the combustion chamber 11 and the nozzle 12 are arranged in sequence.

[0023] The feed port of the precooler 3 is connected to the fuel tank 1, and the discharge port of the precooler 3 is connected to the regeneration cooling channel 4. A part of the outlet of the regeneration cooling channel 4 is connected to the fuel injector 8. The fuel injector 8 injects fuel into the combustion chamber 11 and mixes it with the compressed air in the intake duct 9 to burn. The high-temperature combustion gas expands in the tail nozzle 12 to generate thrust; the other part is connected to the ammonia decomposition gas turbine 5, and the ammonia decomposition gas turbine 5 is connected to the motor 15. The outlet of the ammonia decomposition gas turbine 5 is connected to the anode of the solid oxide fuel cell 7, and undergoes an oxidation-reduction reaction with the cathode gas to generate electrical energy.

[0024] like Figure 2 As shown, the regeneration cooling channels are arranged in parallel pipes, and the outlet of the fuel tank 2 is connected to the regeneration cooling channel 4 .

[0025] The tail gas of the solid oxide fuel cell 7 returns to the combustion chamber 11 through the fuel injector 8 .

[0026] Energy is utilized in a cascade manner. Ammonia is decomposed in the regenerative cooling channel 4. The ammonia decomposition gas at the outlet of the regenerative cooling channel 4 drives the turbine 5, which enables the generator 15 to generate electricity to increase the power generation of the system; air enters the anode and cathode of the fuel cell 7 through the compressor 6 and the ammonia decomposition gas respectively to generate electricity; the exhaust gas of the fuel cell 7 returns to the combustion chamber 11 through the fuel injector 8 to be burned, and the waste heat is recovered, thereby improving the thermal efficiency of the system.

[0027] The fuel is a mixed fuel, and the fuel tank includes an ammonia fuel tank 1 and an aviation kerosene fuel tank 2. The ammonia fuel tank 1 is connected to the feed port of the precooler 3 and is used to cool the air at the air intake 14. The outlet of the precooler 3 is connected to the inlet of a part of the pipeline of the regenerative cooling channel 4. Ammonia is decomposed in the regenerative cooling channel 4 to absorb the waste heat of the combustion chamber 11, and the decomposition products at the outlet of the regenerative cooling channel 4 are passed into the anode of the fuel cell 7; the aviation kerosene fuel tank 2 is passed into a part of the pipeline of the regenerative cooling channel 4 through the aviation kerosene fuel pump 16 to cool the combustion chamber 11, and then returns to the fuel injector 8, injecting the fuel into the combustion chamber 11 to mix and burn with the compressed air in the intake duct 9, and the high-temperature combustion gas expands in the tail nozzle 12 to generate thrust.

[0028] The regeneration cooling channel 4 is a parallel pipeline with a microchannel structure. Ammonia is passed through one part of the pipeline, and aviation kerosene is passed through another part of the pipeline. The ammonia is decomposed in the regeneration cooling channel 4 and used as the anode working fluid of the fuel cell 7. The aviation kerosene is decomposed in the regeneration cooling channel 4 and returned to the combustion chamber 11 for combustion.

[0029] The compressor 6 takes the air after passing through the precooler 3 and makes the temperature and pressure of the air meet the working conditions for entering the cathode of the fuel cell 7, that is, the temperature is 800-1000K and the pressure is 1Mpa.

[0030] The ammonia decomposition gas turbine 5 takes the ammonia decomposition gas from the outlet of the regeneration cooling channel 4 and makes the ammonia decomposition gas meet the temperature and pressure required to enter the anode of the fuel cell 7, namely, the temperature is 800-1000K and the pressure is 1 MPa.

[0031] The wall surface of the regeneration cooling channel 4 is provided with high-energy metal powder or coated with a layer of catalyst to increase the decomposition rate of ammonia.

[0032] The scramjet engine 13 uses aviation kerosene and ammonia as fuel, while the fuel cell 7 contains hydrogen, nitrogen, oxygen, and ammonia as working fluids. The ammonia fuel used in the scramjet engine 13 effectively alleviates the problem of coking in the cooling channels. Ammonia's larger heat sink also allows for better absorption of waste heat from the combustion chamber. Ammonia fuel is also suitable for SOFCs. Within an operating temperature range of 700-900°C, the power generation efficiency of ammonia-fueled solid oxide fuel cells approaches that of hydrogen fuel.

[0033] The solid oxide fuel cell 7 and ammonia decomposition gas generator 15 form the power generation device, while the scramjet engine 13 serves as the power plant. The fuel cell 7 meets the ever-increasing power needs of hypersonic vehicles. The solid oxide fuel cell 7's high operating temperature and wide range of fuel sources are perfectly suited to the scramjet engine's 13 operating environment. Its simple structure without rotating parts also makes the solid oxide fuel cell 7 suitable for airborne power generation.

[0034] The working principle of the dual-fuel scramjet engine using ammonia fuel cells for power generation using energy cascade utilization according to the present invention is as follows: The ammonia fuel in the ammonia fuel tank 1 can be used as a cold source and is used to cool the high-temperature air taken out from the air intake 14 through the precooler 3. The cooled air is passed into the compressor 6 to meet the working conditions of the solid oxide fuel cell 7, and then passed into the cathode of the solid oxide fuel cell 7.

[0035] The ammonia mixed fuel decomposed by the precooler and the jet fuel in the jet fuel tank 2 are respectively introduced into the regeneration cooling channel 4 to regenerate and cool the scramjet engine combustion chamber 11. Part of the cooled ammonia fuel is introduced into the ammonia decomposition gas turbine 5, which is connected to the motor 15. The outlet of the ammonia decomposition gas turbine 5 is introduced into the anode of the solid oxide fuel cell 7.

[0036] The exhaust gas of the fuel cell 7 is connected to the fuel injector 8 through a pipe and enters the combustion chamber. The remaining ammonia decomposition fuel and the jet fuel decomposition fuel are also connected to the fuel injector 8 through a pipe. The fuel enters the combustion chamber 11 through the fuel injector 8, and is mixed with the air compressed by the shock wave of the air inlet 9 and burned in the combustion chamber 11. The high-temperature combustion gas expands in the tail nozzle 12 to generate thrust. The present invention uses low-temperature fuel as a cold source to cool the air and uses mixed fuel to cool the combustion chamber, which greatly improves the problems existing in the cooling channel; after the ammonia is decomposed, part of the decomposed gas provides gaseous working fluid for the fuel cell, and the remaining decomposed gas returns to the combustion chamber for combustion, thereby improving the performance of the engine. The present invention combines multiple energy conversion technologies together, utilizing waste heat, waste gas and other resources to achieve efficient energy utilization. The fuel cell can directly convert fuel into electrical energy, and the ammonia decomposition gas-generator can generate electricity through the decomposition gas of ammonia. The cascade utilization of energy is achieved, which greatly improves the energy utilization efficiency of the entire system, reduces energy waste, achieves reasonable energy adaptation, and improves the overall power generation efficiency of the system. The embodiments of the present invention disclosed above are intended only to illustrate the present invention. The embodiments do not describe all details in detail, nor do they limit the present invention to the specific embodiments described. Numerous modifications and variations are possible based on the contents of this specification. These embodiments are selected and described in detail in this specification to better explain the principles and practical applications of the present invention, thereby enabling those skilled in the art to better understand and utilize the present invention.

Claims

1. A dual-fuel scramjet engine powered by an ammonia fuel cell with cascaded energy utilization, characterized by: The scramjet engine (13) comprises an ammonia fuel tank (1), an aviation kerosene fuel tank (2), a precooler (3), a regenerative cooling channel (4), an ammonia decomposition gas turbine (5), a compressor (6), a solid oxide fuel cell (7) and a motor (15). The scramjet engine (13) comprises a regenerative cooling channel (4), a fuel injector (8), an air inlet (9), an isolation section (10), a combustion chamber (11) and a nozzle (12). The air inlet (9), the isolation section (10), the combustion chamber (11) and the nozzle (12) are arranged in sequence. The feed port of the precooler (3) is connected to the fuel tank 1, the discharge port of the precooler (3) and the outlet of the fuel tank 2 are respectively connected to the regeneration cooling channel (4), a part of the outlet of the regeneration cooling channel (4) is connected to the fuel injector (8), the fuel is injected into the combustion chamber (11) and mixed with the compressed air in the intake duct (9) for combustion, and the high-temperature combustion gas expands in the tail nozzle 12 to generate thrust, and the other part is connected to the ammonia decomposition gas turbine (5), the ammonia decomposition gas turbine (5) is connected to the motor (15), the outlet of the ammonia decomposition gas turbine (5) is connected to the anode of the solid oxide fuel cell (7), the compressor (6) is connected to the cathode of the solid oxide fuel cell (7), and the ammonia and the cathode gas undergo redox reaction to generate electrical energy.

2. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1, characterized in that: The tail gas of the solid oxide fuel cell (7) returns to the combustion chamber (11) through the fuel injector (8).

3. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1 is characterized in that: The regeneration cooling channel (4) is a parallel pipeline with a microchannel structure, with ammonia passing through one part of the pipeline and aviation kerosene passing through another part of the pipeline. The ammonia passing through the regeneration cooling channel (4) is decomposed in the regeneration cooling channel (4) and used as the anode working fluid of the solid oxide fuel cell (7). The aviation kerosene passing through the regeneration cooling channel (4) is decomposed and then returned to the combustion chamber (11) for combustion.

4. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1, characterized in that: The compressor (6) takes the air after passing through the precooler (3) so that the temperature and pressure of the air meet the working conditions for entering the cathode of the solid oxide fuel cell (7).

5. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 4 is characterized in that: The operating conditions of the cathode of the solid oxide fuel cell (7) are a temperature of 800-1000K and a pressure of 1 MPa.

6. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1, characterized in that: The ammonia decomposition gas turbine (5) takes the ammonia decomposition gas from the outlet of the regeneration cooling channel (4) so ​​that the ammonia decomposition gas meets the working conditions for entering the anode of the solid oxide fuel cell (7).

7. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 6, characterized in that: The operating conditions of the anode of the solid oxide fuel cell (7) are a temperature of 800-1000K and a pressure of 1 MPa.

8. The dual-fuel scramjet engine for power generation using ammonia fuel cells with cascaded energy utilization according to claim 1, characterized in that: The ammonia fuel in the ammonia fuel tank (1) can be used as a cold source to cool the high-temperature air taken out from the air intake 14 through the precooler (3). The cooled air is passed into the compressor (6) to meet the working conditions of the solid oxide fuel cell (7), and then passed into the cathode of the solid oxide fuel cell (7).

9. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1, characterized in that: The ammonia mixed fuel decomposed by the precooler and the jet fuel in the jet fuel tank (2) are respectively introduced into the regeneration cooling channel (4) to regenerate and cool the scramjet engine combustion chamber (11). Part of the cooled ammonia fuel is introduced into the ammonia decomposition gas turbine (5). The ammonia decomposition gas turbine (5) is connected to the motor (15). The outlet of the ammonia decomposition gas turbine (5) is introduced into the anode of the solid oxide fuel cell (7).

10. The dual-fuel scramjet engine for power generation using an ammonia fuel cell with cascaded energy utilization according to claim 1, characterized in that: The wall surface of the regeneration cooling channel (4) is provided with high-energy metal powder or coated with a catalyst.

Images