Multi-modal combined power cycle system and method for helium-cooled internal reheat duct air

Abstract

The application discloses a kind of helium cooling inner channel air multi-modal combined power cycle system and method, system can carry out the conversion of 4 kinds of working modes by adjustable geometry, especially in turbine ram switching mode, helium is as closed quasi-brayton cycle working substance, by cooling and heating to the air of inner channel air compressor front air, significantly reduce the power consumption of turbine mode compressor, improve the thrust of mode conversion process;At the same time, helium is as intermediate medium and transmits the heat of inner channel air to outer channel air, improves the thrust of outer channel air.The turbine ram combined engine of the present application compared with the conventional jet precooling improves the thrust of mode conversion process, will not affect the oxygen content of compressor inlet flow, the total pressure loss of flow is small, can improve the pressure ratio of compressor under turbine ram switching mode, improve the working environment of engine, solve the "thrust gap" problem when working mode switches, realize the working requirement of wide speed range.

Description

Technical Field

[0001] This invention relates to the aerospace field, and more particularly to a helium-cooled multimodal combined power cycle system and method for duct air. Background Technology

[0002] With the continuous advancement of aviation technology, humanity has begun to pursue increasingly higher Mach numbers. The future mission requirements for long endurance, high maneuverability, wide speed range, and low fuel consumption have spurred the advanced design of turbojet-ramjet combined cycle aero engines. However, existing aero-turbine engines suffer from a problem at high altitudes and high Mach numbers: limited compressor flow capacity due to the temperature resistance of the compression system inlet, resulting in engine flow restriction and consequently, thrust reduction. On the other hand, ramjet engines require more stringent inflow conditions to improve their power performance, similarly leading to a significant thrust drop when transitioning from turbine mode to ramjet mode. Introducing a cooling process for the high-temperature inflow into the turbine engine can suppress temperature rise during compression, increase the overall pressure ratio, increase inlet flow, and improve engine thrust, thereby improving the engine's thermodynamic cycle. Among these technologies, jet precooling (MIPCC), which involves adding a coolant spray device before the compressor or fan, has potential technological advantages and application prospects. Using liquid water as a coolant, it mixes with the surrounding high-temperature air to form a gas-liquid two-phase flow, which affects the flow field characteristics inside the compressor, thereby effectively improving the thrust performance of the turbine engine at high altitude and high speed and expanding the original flight envelope.

[0003] While jet precooling technology can effectively address the adverse effects of high-temperature stagnation caused by high-speed airflow, the injection of cooling media reduces the oxygen content in the compressor inlet during high-altitude, high-speed flight. This typically necessitates the use of a liquid oxygen storage device to replenish the oxidizer, thus lowering the aircraft's thrust-to-weight ratio. Furthermore, this approach suffers from reduced specific impulse, increased engine length, increased total pressure loss in the inlet, distortion of the total inlet temperature, and a large required volume of cooling media. To ensure the reliable and stable operation of components such as the compressor, researchers both domestically and internationally have been dedicated to developing and improving cooling technologies to reduce compressor power consumption. However, achieving the desired results has been challenging, posing a significant challenge to the stable operation of cold-end components in aero-engines. Therefore, taking measures to reduce the compressor inlet temperature of aero-engines and improve the combined engine operating environment to address the "thrust gap" problem during mode transitions is of great significance. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to address the deficiencies mentioned in the background art by providing a helium-cooled multimodal combined power cycle system for internal air.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0006] A multimodal combined power cycle system for cooling the air inside the helium-cooled duct includes an intake duct, a front fan, a rear fan, a first heat exchanger, a second heat exchanger, a third heat exchanger, a low-pressure compressor, a high-pressure compressor, a main combustion chamber, a kerosene storage tank, a kerosene pump, a high-pressure turbine, a medium-pressure turbine, a low-pressure turbine, a helium storage tank, a helium compressor, a helium turbine, an afterburner, an outer bypass nozzle, an inner bypass nozzle, and valves one through eleven.

[0007] The main combustion chamber includes a fuel inlet, an air inlet, and a gas outlet, which are used for the initial combustion of fuel entering from its fuel inlet and air entering from its air inlet, generating gas which is then discharged from its gas outlet.

[0008] The afterburner includes a fuel inlet, an air inlet, and a gas outlet, for mixing and burning fuel entering from its fuel inlet and air entering from its air inlet to generate gas, which is then discharged from its gas outlet.

[0009] The air intake inlet is connected to the outside air, and the outlet is connected to the inlet of the front fan;

[0010] The outlet of the front fan is connected to one end of the first valve, one end of the second valve, one end of the third valve, and one end of the eleventh valve, respectively.

[0011] The other end of the first valve is connected to the inlet of the rear fan; the outlet of the rear fan is connected to one end of the seventh valve and one end of the eighth valve, respectively.

[0012] The inlet of the hot side channel of the second heat exchanger is connected to the other end of the seventh valve, the outlet of the hot side channel is connected to one end of the fourth valve, the inlet of the cold side channel is connected to one end of the fifth valve, and the outlet of the cold side channel is connected to the inlet of the hot side channel of the first heat exchanger and one end of the sixth valve, respectively.

[0013] The inlet of the hot side channel of the third heat exchanger is connected to the other end of the fourth valve and the other end of the eighth valve, respectively. The outlet of the hot side channel is connected to the inlet of the low-pressure compressor and the other end of the eleventh valve, respectively. The inlet of the cold side channel is connected to the outlet of the helium compressor, respectively. The outlet of the cold side channel is connected to the other end of the fifth valve and the other end of the sixth valve, respectively.

[0014] The outlet of the hot side passage of the first heat exchanger is connected to the inlet of the helium turbine, the inlet of the cold side passage is connected to the other end of the second valve, and the outlet of the cold side passage is connected to the inlet of the outer bypass nozzle; the outlet of the outer bypass nozzle is connected to the outside.

[0015] The inlet of the helium compressor is connected to the outlet of the helium storage tank; the inlet of the helium storage tank is connected to the outlet of the helium turbine.

[0016] The inlet of the kerosene pump is connected to the outlet of the kerosene storage tank, and the outlet of the kerosene pump is connected to one end of the ninth valve and one end of the tenth valve, respectively.

[0017] The outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor;

[0018] The air inlet of the main combustion chamber is connected to the outlet of the high-pressure compressor, the gas outlet is connected to the inlet of the high-pressure turbine, and the fuel inlet is connected to the other end of the ninth valve.

[0019] The inlet of the intermediate-pressure turbine is connected to the outlet of the high-pressure turbine, and the outlet of the intermediate-pressure turbine is connected to the inlet of the low-pressure turbine.

[0020] The air inlet of the afterburner is connected to the other end of the third valve, the fuel inlet is connected to the other end of the tenth valve, and the gas outlet is connected to the outlet of the low-pressure turbine and the inlet of the internal nozzle, respectively.

[0021] The outlet of the inner nozzle is connected to the outside.

[0022] This invention also discloses a method for operating a helium-cooled multimodal combined power cycle system for internal air cooling, comprising the following operating methods:

[0023] When the aircraft is in takeoff acceleration: valves 9 and 11 are opened, and valves 1, 2, 3, 4, 5, 6, 7, 8, and 10 are closed; air enters the engine intake duct, is compressed by the front fan, and the pressurized air enters the main combustion chamber to mix and burn with fuel. The resulting high-temperature, high-pressure gas is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine to expand and do work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan to compress air; the gas after doing work is discharged through the internal nozzle, generating thrust;

[0024] When the aircraft is in low-speed flight: valves 1, 2, 6, 8, and 9 are open, while valves 3, 4, 5, 7, 10, and 11 are closed. Air enters the engine intake duct and is compressed by the front fan. The compressed air is then divided into two paths: one path enters the first heat exchanger to exchange heat with high-temperature helium, and the air is discharged through the outer bypass nozzle, generating thrust; the other path enters the rear fan and is compressed. The compressed air enters the third heat exchanger to exchange heat with low-temperature helium, and then sequentially enters the low-pressure compressor and high-pressure compressor for further compression. The compressed air enters the main combustion chamber and mixes with fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the inner nozzle, generating thrust.

[0025] When the aircraft is in turbo-ramjet switching mode, valves 1, 2, 4, 5, 7, and 9 are opened, while valves 3, 6, 8, 10, and 11 are closed. Air enters the engine intake duct and is compressed by the front fan. The compressed air is then divided into two paths: one path enters the first heat exchanger for heat exchange with high-temperature helium, and the air is discharged through the outer bypass nozzle, generating thrust; the other path enters the rear fan for compression. The compressed air then sequentially enters the second and third heat exchangers for heat exchange with low-temperature helium. The compressed air then sequentially enters the low-pressure compressor and high-pressure compressor for further compression. The compressed air enters the main combustion chamber and mixes with fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the inner nozzle, generating thrust.

[0026] When the aircraft is in high-speed flight: open the third and tenth valves, and close the first, second, fourth, fifth, sixth, seventh, eighth, ninth, and eleventh valves; the engine intake air enters the intake duct, is compressed by the front fan, and the pressurized air directly enters the afterburner to mix and burn with the fuel. The generated high-temperature and high-pressure gas is discharged through the internal nozzle to generate thrust.

[0027] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0028] This invention, through its adjustable geometry, enables the switching between takeoff, acceleration, and high-speed flight operating modes, meeting the needs of aircraft in different states. In the first heat exchanger of this invention, helium and air undergo gas-to-gas heat exchange, resulting in a relatively high heat transfer coefficient. By introducing an intermediate closed-loop helium cycle, the drawbacks of direct heat exchange between the two bypass ducts, such as small air heat sink and large pressure loss of the outer bypass air, which lead to low heat transfer efficiency, are avoided. Furthermore, the increased temperature of the outer bypass air can further enhance the thrust of the outer bypass nozzle.

[0029] This invention has four operating states. When Ma is below 0.8, the third heat exchanger, second heat exchanger, and afterburner are not activated: valves 9 and 11 are open, and valves 1, 2, 3, 4, 5, 6, 7, 8, and 10 are closed. The bypass duct and helium circulation are not activated; air enters the main combustion chamber of the inner duct and mixes with fuel for combustion. The generated high-temperature gas expands, performs work, and is then discharged through the inner duct nozzle. When Ma is between 0.8 and 1.3, the second heat exchanger and afterburner are not activated: valves 1, 2, 6, 8, and 9 are open, and valves 3, 4, 5, 7, 10, and 11 are closed. Helium exchanges heat with the air in the inner duct through the third heat exchanger, moderately cooling the air in the inner duct. Then, it exchanges heat with the air in the outer bypass duct through the first heat exchanger, raising the temperature of the outer bypass duct air. Subsequently, it enters the helium turbine, expands, and performs work, driving the helium compressor, and finally enters the helium storage tank, completing the helium cycle. When Ma is 1.3~3.5, the afterburner is not activated: valves 1, 2, 4, 5, 7, and 9 are open, while valves 3, 6, 8, 10, and 11 are closed. Helium exchanges heat with the air in the inner duct through the third and second heat exchangers, and then transfers heat to the air in the outer bypass duct through the first heat exchanger. It then enters the helium turbine to expand and do work, driving the helium compressor, and finally enters the helium storage tank, completing the helium cycle. When Ma is 3.5~5, the first, second, and third heat exchangers are not activated: valves 1, 2, 4, 5, 6, 7, 8, 9, and 11 are closed. The core engine is in fan mode, and the helium cycle is not activated. The afterburner is activated, and high-temperature air directly enters the afterburner to mix and burn with the fuel, then is discharged through the inner nozzle. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the present invention;

[0031] In the diagram, 1-Intake duct, 2-Front fan, 3-Rear fan, 4-First heat exchanger, 5-Second heat exchanger, 6-Third heat exchanger, 7-Low-pressure compressor, 8-High-pressure compressor, 9-Main combustion chamber, 10-Kerosene storage tank, 11-Kerosene pump, 12-High-pressure turbine, 13-Medium-pressure turbine, 14-Low-pressure turbine, 15-Helium storage tank, 16-Helium compressor, 17-Helium turbine, 18-Afterburner, 19-Outer bypass nozzle, 20-Inner bypass nozzle, 21-First valve, 22-Second valve, 23-Third valve, 24-Fourth valve, 25-Fifth valve, 26-Sixth valve, 27-Seventh valve, 28-Eighth valve, 29-Ninth valve, 30-Tenth valve, 31-Eleventh valve. Implementation

[0032] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings:

[0033] This invention can be implemented in many different forms and should not be considered limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully express the scope of the invention to those skilled in the art. In the drawings, components are enlarged for clarity.

[0034] It should be understood that although the terms first, second, third, etc., may be used herein to describe various elements, components, and / or parts, these elements, components, and / or parts are not limited by these terms. These terms are merely used to distinguish elements, components, and / or parts from one another. Therefore, the first element, component, and / or part discussed below may be a second element, component, or part without departing from the teachings of this invention.

[0035] like Figure 1 As shown, this invention discloses a multimodal combined power cycle system for cooling the air inside the intake duct with helium, including an intake duct, a front fan, a rear fan, a first heat exchanger, a second heat exchanger, a third heat exchanger, a low-pressure compressor, a high-pressure compressor, a main combustion chamber, a kerosene storage tank, a kerosene pump, a high-pressure turbine, a medium-pressure turbine, a low-pressure turbine, a helium storage tank, a helium compressor, a helium turbine, an afterburner, an outer bypass nozzle, an inner bypass nozzle, and first to eleventh valves;

[0036] The main combustion chamber includes a fuel inlet, an air inlet, and a gas outlet, which are used for the initial combustion of fuel entering from its fuel inlet and air entering from its air inlet, generating gas which is then discharged from its gas outlet.

[0037] The afterburner includes a fuel inlet, an air inlet, and a gas outlet, which is used to mix and burn the fuel that enters from its fuel inlet and the air that enters from its air inlet, generating gas which is then discharged from its gas outlet.

[0038] The air intake inlet is connected to the outside air, and the outlet is connected to the inlet of the front fan;

[0039] The outlet of the front fan is connected to one end of the first valve, one end of the second valve, one end of the third valve, and one end of the eleventh valve, respectively.

[0040] The other end of the first valve is connected to the inlet of the rear fan; the outlet of the rear fan is connected to one end of the seventh valve and one end of the eighth valve, respectively.

[0041] The inlet of the hot side channel of the second heat exchanger is connected to the other end of the seventh valve, the outlet of the hot side channel is connected to one end of the fourth valve, the inlet of the cold side channel is connected to one end of the fifth valve, and the outlet of the cold side channel is connected to the inlet of the hot side channel of the first heat exchanger and one end of the sixth valve, respectively.

[0042] The inlet of the hot side channel of the third heat exchanger is connected to the other end of the fourth valve and the other end of the eighth valve, respectively. The outlet of the hot side channel is connected to the inlet of the low-pressure compressor and the other end of the eleventh valve, respectively. The inlet of the cold side channel is connected to the outlet of the helium compressor, respectively. The outlet of the cold side channel is connected to the other end of the fifth valve and the other end of the sixth valve, respectively.

[0043] The outlet of the hot side passage of the first heat exchanger is connected to the inlet of the helium turbine, the inlet of the cold side passage is connected to the other end of the second valve, and the outlet of the cold side passage is connected to the inlet of the outer bypass nozzle; the outlet of the outer bypass nozzle is connected to the outside.

[0044] The inlet of the helium compressor is connected to the outlet of the helium storage tank; the inlet of the helium storage tank is connected to the outlet of the helium turbine.

[0045] The inlet of the kerosene pump is connected to the outlet of the kerosene storage tank, and the outlet of the kerosene pump is connected to one end of the ninth valve and one end of the tenth valve, respectively.

[0046] The outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor;

[0047] The air inlet of the main combustion chamber is connected to the outlet of the high-pressure compressor, the gas outlet is connected to the inlet of the high-pressure turbine, and the fuel inlet is connected to the other end of the ninth valve.

[0048] The inlet of the intermediate-pressure turbine is connected to the outlet of the high-pressure turbine, and the outlet of the intermediate-pressure turbine is connected to the inlet of the low-pressure turbine.

[0049] The air inlet of the afterburner is connected to the other end of the third valve, the fuel inlet is connected to the other end of the tenth valve, and the gas outlet is connected to the outlet of the low-pressure turbine and the inlet of the internal nozzle, respectively.

[0050] The outlet of the inner nozzle is connected to the outside.

[0051] This invention also discloses a method for operating a helium-cooled multimodal combined dynamic system with internal duct air, comprising the following processes:

[0052] If the aircraft is in takeoff acceleration mode, with a flight speed of Mach 0~0.8: Open valves 9 and 11, and close valves 1, 2, 3, 4, 5, 6, 7, 8, and 10. Air enters the engine intake duct, is compressed by the front fan, and then enters the main combustion chamber to mix and burn with fuel. The resulting high-temperature, high-pressure gas is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the internal nozzle, generating thrust.

[0053] During takeoff acceleration, the thrust demand is high, the outer bypass duct is not open, and all thrust is generated by the inner nozzle.

[0054] If the aircraft is in low-speed flight (Ma 0.8~1.3): Open valves 1, 2, 6, 8, and 9; close valves 3, 4, 5, 7, 10, and 11. Air enters the engine intake duct and is compressed by the front fan. The compressed air is divided into two paths: one path enters the first heat exchanger to exchange heat with high-temperature helium, and the air is then discharged through the outer bypass nozzle, generating thrust; the other path enters the rear fan for compression. The compressed air enters the third heat exchanger to exchange heat with low-temperature helium, and then sequentially enters the low-pressure compressor and high-pressure compressor for further compression. The compressed air enters the main combustion chamber and mixes with fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the inner nozzle, generating thrust.

[0055] During low-speed flight, the high-pressure, low-temperature helium gas directly enters the third heat exchanger to cool the inner duct air. After absorbing heat in the third heat exchanger, the helium gas exchanges heat with the outer duct air through the first heat exchanger. Then, it enters the helium turbine to expand and do work, driving the helium compressor to compress the helium gas. The helium gas after doing work is then fed into the helium storage tank, completing the cycle.

[0056] If the aircraft is in turbo-ramjet switching mode, with a flight speed of Mach 1.3~3.5, the operating principle is the same as in takeoff acceleration mode, but due to the increased flight speed, the throat area of ​​the bypass nozzle should decrease accordingly. Open valves 1, 2, 4, 5, 7, and 9, and close valves 3, 6, 8, 10, and 11. Engine intake air enters the intake duct, is compressed by the front fan, and the compressed air is divided into two paths: one path enters the first heat exchanger for heat exchange with high-temperature helium, and the heated air is discharged through the bypass nozzle, generating thrust; the other path enters the rear fan and is compressed. The compressed air then sequentially enters the second and third heat exchangers for heat exchange with low-temperature helium. After heat exchange, the air sequentially enters the low-pressure compressor and then the high-pressure compressor, where it is compressed. The compressed air then enters the main combustion chamber and mixes with the fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, the intermediate-pressure turbine, and the low-pressure turbine for expansion and work, driving the high-pressure compressor, the low-pressure compressor, the front fan, and the rear fan, respectively, to compress the air. The gas, after performing work, is discharged through the internal nozzle, generating thrust.

[0057] During the turbo-ramjet switching mode, high-pressure, low-temperature helium gas sequentially enters the third and second heat exchangers, where it exchanges heat with the inner duct air in a counter-current flow. After absorbing heat, the helium gas exchanges heat with the outer bypass air through the first heat exchanger. It then enters the helium turbine to expand and do work, driving the helium compressor to compress the helium gas. The helium gas after doing work enters the helium storage tank, completing the cycle.

[0058] If the aircraft is in high-speed flight, at a speed of Mach 3.5~5: Open valves 3 and 10, and close valves 1, 2, 4, 5, 6, 7, 8, 9, and 11. Air enters the engine intake duct, is compressed by the front fan, and the pressurized air directly enters the afterburner to mix and burn with fuel. The resulting high-temperature, high-pressure combustion gas is discharged through the internal nozzle, generating thrust.

[0059] During high-speed flight, the bypass nozzle is completely closed, the core engine operates in a windmill mode, the main combustion chamber is closed, the afterburner is open, and the engine switches to turbojet mode. The high-temperature airflow, compressed by the front fan, directly enters the bypass duct, significantly increasing the gas flow capacity at high Mach numbers. Essentially, the bypass duct transforms into an internal duct. The high-temperature airflow then enters the afterburner, raising the combustion temperature and thus increasing thrust. The overall power cycle parameters are characterized by a low bypass ratio and high afterburner temperature.

[0060] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the same meaning as in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein.

[0061] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multimodal combined power cycle system for cooling internal air ducts with helium gas, characterized in that, It includes an air intake, front fan, rear fan, first heat exchanger, second heat exchanger, third heat exchanger, low-pressure compressor, high-pressure compressor, main combustion chamber, kerosene storage tank, kerosene pump, high-pressure turbine, medium-pressure turbine, low-pressure turbine, helium storage tank, helium compressor, helium turbine, afterburner, outer bypass nozzle, inner bypass nozzle, and first to eleventh valves; The main combustion chamber includes a fuel inlet, an air inlet, and a gas outlet, which are used for the initial combustion of fuel entering from its fuel inlet and air entering from its air inlet, generating gas which is then discharged from its gas outlet. The afterburner includes a fuel inlet, an air inlet, and a gas outlet, for mixing and burning fuel entering from its fuel inlet and air entering from its air inlet to generate gas, which is then discharged from its gas outlet. The air intake inlet is connected to the outside air, and the outlet is connected to the inlet of the front fan; The outlet of the front fan is connected to one end of the first valve, one end of the second valve, one end of the third valve, and one end of the eleventh valve, respectively. The other end of the first valve is connected to the inlet of the rear fan; the outlet of the rear fan is connected to one end of the seventh valve and one end of the eighth valve, respectively. The inlet of the hot side channel of the second heat exchanger is connected to the other end of the seventh valve, the outlet of the hot side channel is connected to one end of the fourth valve, the inlet of the cold side channel is connected to one end of the fifth valve, and the outlet of the cold side channel is connected to the inlet of the hot side channel of the first heat exchanger and one end of the sixth valve, respectively. The inlet of the hot side channel of the third heat exchanger is connected to the other end of the fourth valve and the other end of the eighth valve, respectively. The outlet of the hot side channel is connected to the inlet of the low-pressure compressor and the other end of the eleventh valve, respectively. The inlet of the cold side channel is connected to the outlet of the helium compressor, respectively. The outlet of the cold side channel is connected to the other end of the fifth valve and the other end of the sixth valve, respectively. The outlet of the hot side passage of the first heat exchanger is connected to the inlet of the helium turbine, the inlet of the cold side passage is connected to the other end of the second valve, and the outlet of the cold side passage is connected to the inlet of the outer bypass nozzle. The outlet of the outer nozzle is connected to the outside. The inlet of the helium compressor is connected to the outlet of the helium storage tank; the inlet of the helium storage tank is connected to the outlet of the helium turbine. The inlet of the kerosene pump is connected to the outlet of the kerosene storage tank, and the outlet of the kerosene pump is connected to one end of the ninth valve and one end of the tenth valve, respectively. The outlet of the low-pressure compressor is connected to the inlet of the high-pressure compressor; The air inlet of the main combustion chamber is connected to the outlet of the high-pressure compressor, the gas outlet is connected to the inlet of the high-pressure turbine, and the fuel inlet is connected to the other end of the ninth valve. The inlet of the intermediate-pressure turbine is connected to the outlet of the high-pressure turbine, and the outlet of the intermediate-pressure turbine is connected to the inlet of the low-pressure turbine. The air inlet of the afterburner is connected to the other end of the third valve, the fuel inlet is connected to the other end of the tenth valve, and the gas outlet is connected to the outlet of the low-pressure turbine and the inlet of the internal nozzle, respectively. The outlet of the inner nozzle is connected to the outside.

2. The helium-cooled duct air multimodal combined power cycle system according to claim 1, characterized in that, This includes the following working methods: When the aircraft is in takeoff acceleration: valves 9 and 11 are opened, and valves 1, 2, 3, 4, 5, 6, 7, 8, and 10 are closed; air enters the engine intake duct, is compressed by the front fan, and the pressurized air enters the main combustion chamber to mix and burn with fuel. The resulting high-temperature, high-pressure gas is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine to expand and do work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan to compress air; the gas after doing work is discharged through the internal nozzle, generating thrust; When the aircraft is in low-speed flight: valves 1, 2, 6, 8, and 9 are open, while valves 3, 4, 5, 7, 10, and 11 are closed. Air enters the engine intake duct and is compressed by the front fan. The compressed air is then divided into two paths: one path enters the first heat exchanger to exchange heat with high-temperature helium, and the air is discharged through the outer bypass nozzle, generating thrust; the other path enters the rear fan and is compressed. The compressed air enters the third heat exchanger to exchange heat with low-temperature helium, and then sequentially enters the low-pressure compressor and high-pressure compressor for further compression. The compressed air enters the main combustion chamber and mixes with fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the inner nozzle, generating thrust. When the aircraft is in turbo-ramjet switching mode, valves 1, 2, 4, 5, 7, and 9 are opened, while valves 3, 6, 8, 10, and 11 are closed. Air enters the engine intake duct and is compressed by the front fan. The compressed air is then divided into two paths: one path enters the first heat exchanger for heat exchange with high-temperature helium, and the air is discharged through the outer bypass nozzle, generating thrust; the other path enters the rear fan for compression. The compressed air then sequentially enters the second and third heat exchangers for heat exchange with low-temperature helium. The compressed air then sequentially enters the low-pressure compressor and high-pressure compressor for further compression. The compressed air enters the main combustion chamber and mixes with fuel for combustion. The high-temperature, high-pressure gas generated in the main combustion chamber is sequentially fed into the high-pressure turbine, intermediate-pressure turbine, and low-pressure turbine for expansion and work, driving the high-pressure compressor, low-pressure compressor, front fan, and rear fan, respectively, to compress air. The gas, after performing work, is discharged through the inner nozzle, generating thrust. When the aircraft is in high-speed flight: open the third and tenth valves, and close the first, second, fourth, fifth, sixth, seventh, eighth, ninth, and eleventh valves; the engine intake air enters the intake duct, is compressed by the front fan, and the pressurized air directly enters the afterburner to mix and burn with the fuel. The generated high-temperature and high-pressure gas is discharged through the internal nozzle to generate thrust.

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