Low bypass ratio turbofan engine

Abstract

A low-bypass-ratio turbofan engine comprises a fan, an outer duct, a gas conveying valve, a bypass pipe, an external valve, an axial-flow type gas compressor, a combustion chamber, a turbine, an exhaust nozzle and the like. During operation after starting, the air delivery valve is opened, a part of compressed air in the outer duct is sprayed into an air inlet of the engine through the bypass pipe, the air inlet pressure is increased under the condition that surge does not occur, and through acting of the engine, the supercharge ratio and the total supercharge ratio of the fan are continuously increased; in the safe operation range of mechanical strength and high-temperature resistance of the engine, the total supercharge ratio and the thrust-weight ratio are increased compared with those of the engine without a gas transmission valve, a bypass pipe and an external valve, then the gas transmission valve is adjusted, the flow of the bypass pipe is reduced, the external valve adjusts the pressure in the bypass pipe, the engine continues to operate after the increased total supercharge ratio is kept unchanged, and the engine is safe. At the moment, the total supercharge ratio and the thrust-weight ratio are increased, but the stage number of the engine and the turbine front temperature are not changed, and the air inlet pressure is not changed.

Description

Technical Field

[0001] The invention relates to a low bypass ratio turbofan engine, belonging to the technical field of military turbofan engines. Background Art

[0002] At present, the total pressure ratio of the world's advanced military low-bypass turbofan engines, such as France's M88, Europe's EJ200, the United States' F119, F135, my country's WS15 and Russia's AL-41F, is 25-35, and the thrust-to-weight ratio is about 10. The United States proposed in the "Integrated High Performance Turbine Engine Technology" (IHPTET) and "General Economic Affordable Advanced Turbine Engine" (VAATE) programs that the thrust-to-weight ratio of the next generation of fighter turbofan engines will develop towards 15-20, and the total pressure ratio will continue to increase; while the total pressure ratio of the current advanced high-bypass turbofan engines is about 50, of which the total pressure ratio of the GE9X is The highest is 60. The British Rolls-Royce company expects that the total compression ratio of the "UltraFan" engine to be put into use after 2025 will be as high as 70. To increase the total compression ratio, the main methods at present are to increase the total number of fans, axial compressors and turbines, and to increase the temperature of the gas before the turbine. However, the first method increases weight, which is not conducive to improving the thrust-to-weight ratio. For example, high bypass ratio turbofan engines such as GE90 and GE9X have a relatively high total compression, but because the total number of fans, axial compressors and turbines is large, the thrust-to-weight ratio is not high. The second method must use high-temperature resistant and high-performance turbine blade materials, coating materials and advanced cooling technology. Although the aforementioned At present, advanced military low bypass ratio turbofan engines use new materials and technologies, such as the use of second-generation single crystal nickel-based alloy technology, the addition of rare materials such as cobalt, rhenium, and ruthenium to improve the microstructure, multi-channel high-pressure air cooling turbine blades, and "cat ear shaped hole" turbine blade cooling technology. The turbine inlet temperature has been greatly improved compared with the previous generation of military low bypass ratio turbofan engines such as Europe's RB199, the United States' F100, F110, and Russia's AL-31F. For example, the turbine inlet temperature of my country's WS15 is 1577°C, while the turbine inlet temperature of the previous generation of military low bypass ratio turbofan engines is only about 1400°C, but continuing to increase the turbine inlet temperature is very Difficult; the core engines of the US F135 and F119 military turbofan engines are the same. Although the total compression ratio of the F135 is lower than that of the F119, the F135 has increased the fan diameter and bypass ratio, which increases the air flow rate and thrust than the F119. However, due to the large fan diameter and bypass ratio of the F135, it is not conducive to high-speed flight. In addition, increasing the intake pressure can also increase the total compression ratio. During the flight of the military low bypass ratio turbofan engine, although the oncoming ram air has an impact on the fan's compression ratio and the total compression ratio, the ram air's ram ratio changes with the flight speed, and it cannot provide high ram pressure ratio compressed air at any speed during flight. Summary of the invention

[0003] The object of the present invention is to provide a low bypass ratio turbofan engine which can improve the total compression ratio and increase the thrust-to-weight ratio under the conditions that the number of engine stages, i.e. the total number of fan, axial compressor and turbine stages remains unchanged, the temperature before the turbine remains unchanged, and the intake pressure remains unchanged.

[0004] The present invention is implemented as follows: a low bypass ratio turbofan engine, whose structure includes a fan, an outer duct, an axial flow compressor, a combustion chamber, a turbine, and a tail nozzle. It is characterized in that there is an air supply valve in the casing of the outer duct, which is an adjustable valve, connected to a bypass pipe at the other end of the engine air inlet, and there is also an external valve on the bypass pipe, which is an overpressure relief valve, etc.

[0005] When the low bypass ratio turbofan engine adopting the above structure is running after starting, the air supply valve is opened to spray a part of the compressed air in the outer duct into the engine intake through the bypass pipe, thereby increasing the intake pressure without surging. After the engine works, the fan's pressure ratio and total pressure ratio continue to increase, and the total pressure ratio and thrust-to-weight ratio are improved within the safe operating range of the engine's mechanical strength and high temperature resistance performance compared with the case without the air supply valve, bypass pipe and external valve. Then the air supply valve is adjusted to reduce the flow of the bypass pipe, and the external valve adjusts the pressure in the bypass to keep the increased total pressure ratio unchanged and continue to operate. At this time, the total pressure ratio and thrust-to-weight ratio increase, but the number of engine stages and the temperature before the turbine remain unchanged, and the intake pressure remains unchanged. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] Figure 1 It is a structural schematic diagram of the low bypass ratio turbofan engine of the present invention. DETAILED DESCRIPTION

[0007] Refer to the attached pictures Figure 1The structure of the low bypass ratio turbofan engine described in the present invention includes a fan 1, an outer duct 2, an air supply valve 3, a bypass pipe 4, an external valve 5, an axial flow compressor 6, a combustion chamber 7, a turbine 8, a tail nozzle 9, etc.; wherein the fan 1 is a multi-stage fan, and the number of stages can be selected as needed, for example, it can be a three-stage fan, etc.; the outer duct 2 is a low bypass ratio outer duct, and the bypass ratio can be selected as needed, for example, the bypass ratio can be about 0.3 or about 0.5, etc.; the air supply valve 3 is in the casing of the outer duct 2, connected to the bypass pipe 4 at the other end of which is at the engine air inlet, and there is also an external valve 5 on the bypass pipe 4, wherein the air supply valve 3 is an adjustable valve The external valve 5 is an overpressure vent valve, which vents air outward, and its opening and closing are automatic. The number of the air supply valve 3, the bypass pipe 4 and the external valve 5 can be selected as needed, and the flow of the bypass pipe 4 after the air supply valve 3 is opened will not cause the engine intake to surge; the number of stages of the axial flow compressor 6 and the turbine 8 can be selected as needed; the combustion chamber 7, that is, the combustion chamber and the evaporative combustion chamber in the core engine, can be selected as needed; the tail nozzle 9 is after the turbine 8, for the discharge of fuel gas, which may or may not have an afterburner, and the tail nozzle 9 may be adjustable, and may have a mixer for mixing the exhaust gas of the inner and outer ducts, etc.

[0008] When the low bypass ratio turbofan engine adopting the above structure is running after starting, the air delivery valve 3 is opened to spray a part of the compressed air in the outer duct 2 into the air intake of the engine through the bypass pipe 4, and the intake pressure is increased without surging. The remaining compressed air in the outer duct 2 still flows through the outer duct 2, and the pressure ratio and the total pressure ratio of the fan 1 are continuously increased through the work of the engine, that is, through the work of the fan 1, the axial flow compressor 6, the combustion chamber 7, and the turbine 8. The total pressure ratio and the thrust ratio are increased within the safe operating range of the engine's mechanical strength and high temperature resistance. The weight ratio is improved compared with the case without the air supply valve 3, the bypass pipe 4 and the external valve 5. Of course, the pressure ratio of the fan 1 is also improved. Then the air supply valve 3 is adjusted to reduce the flow of the bypass pipe 4, and the external valve 5 adjusts the pressure in the bypass 4. That is, when the pressure in the bypass pipe 4 exceeds the need to increase the total pressure ratio and thrust-to-weight ratio, the external valve 5 opens to release part of the air, keeping the increased total pressure ratio unchanged and continuing to run. At this time, the total pressure ratio and thrust-to-weight ratio increase, but the engine stage number and the temperature before the turbine remain unchanged, and the intake pressure remains unchanged. The process is as described above.

[0009] During the above implementation, how much the total compression ratio is improved is related to the high temperature resistance and mechanical strength of the axial flow compressor 6, especially the latter stages thereof. The higher the high temperature resistance and mechanical strength, the higher the total compression ratio after improvement. It is also related to the mechanical strength of the fan 1 and the turbine 8. The present invention can improve the total compression ratio to the limit of the engine material. During the operation after the total compression ratio is improved, compressed air flows through the bypass pipe 4, and the external valve 5 constantly adjusts the pressure in the bypass 4. The thrust-to-weight ratio of the present invention is related to the improved total compression ratio and thrust, that is, the higher the improved total compression ratio and the greater the thrust, the higher the thrust-to-weight ratio.

[0010] Current military turbofan engines are generally equipped with various probes, sensors and other measuring devices for measuring the fan outlet pressure, compressor outlet total pressure / total temperature, engine speed, fuel gas pressure and temperature. The total boost pressure, thrust, thrust-to-weight ratio, etc. can be determined based on their measured values. They can be selected as needed and are not shown in the attached figure.

[0011] The low bypass ratio turbofan engine described in the present invention can be a twin-rotor or a triple-rotor engine; it can be used for all military low bypass ratio turbofan engines such as WS10 and WS15.

[0012] The turbofan engine of the present invention has an anti-surge device, such as the air inlets of the fan 1 and the axial flow compressor 6 can be respectively installed with straightening blades, or the fan 1 is not installed with straightening blades but with wide chord blades, the compressor interstage bleed mechanism, the adjustable stator blade mechanism, etc., can be selected according to needs, and are not shown in the attached drawings.

Claims

1. A low bypass ratio turbofan engine, comprising a fan (1), an outer bypass (2), an axial flow compressor (6), a combustion chamber (7), a turbine (8), and a tail nozzle (9), wherein the engine is characterized by: In the casing of the outer duct (2), there is an air delivery valve (3), which is an adjustable valve, connected to the bypass pipe (4) at the other end of the engine air intake. In the bypass pipe (4), there is also an external valve (5), which is an overpressure relief valve. When the engine is started and running, the air delivery valve (3) is opened to spray a part of the compressed air in the outer duct (2) into the engine air intake through the bypass pipe (4), thereby increasing the intake pressure without causing surge. After the engine works, the compressed air is discharged through the fan (1), the axial flow compressor (2), and the like. The work done by the engine (6), the combustion chamber (7) and the turbine (8), the pressure ratio of the fan (1) and the total pressure ratio are continuously increased, and the total pressure ratio and the thrust-to-weight ratio are increased within the safe operating range of the engine's mechanical strength and high temperature resistance performance compared with the case where there is no air supply valve (3), bypass pipe (4) and external valve (5). Then, the air supply valve (3) is adjusted to reduce the flow rate of the bypass pipe (4), and the external valve (5) adjusts the pressure in the bypass (4) to keep the increased total pressure ratio unchanged and continue the operation of the engine.

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