Variable cycle engine

Abstract

A variable cycle engine comprises a supersonic air inlet channel and a low-bypass-ratio turbofan engine, and the rear portion of the supersonic air inlet channel is connected with an adjustable axial symmetry air inlet channel which is composed of an actuating system and an adjusting piece controlled by an adjusting machine in a sealing cover and is not connected with the turbofan engine. During operation after starting, according to the working scene of the engine, an actuating system and an adjusting machine are controlled, and the opening degree of an adjusting piece is changed, so that the area of an opening of an adjustable axial symmetry air inlet channel is increased during takeoff and subsonic flight, the air inlet bypass ratio of the engine is increased, and the engine works in a turbofan state with the maximum bypass ratio; during climbing, acceleration and supersonic flight, the area of an opening of the adjustable axial symmetry air inlet channel is reduced, the air inlet bypass ratio of the engine is reduced, the engine works in a small-bypass-ratio turbofan or near-turbojet state, the performance of the low-bypass-ratio turbofan engine under different working conditions is improved, high thrust and low oil consumption are maintained, and the structure of the engine is not changed.

Description

Technical Field

[0001] This invention relates to a variable cycle engine, belonging to the technical field of military variable cycle engines. Background Technology

[0002] The American F119 and my country's WF15 are currently the two most advanced military low-bypass turbofan engines, boasting high thrust-to-weight ratios, excellent high-altitude and high-speed performance, and the ability to cruise at supersonic speeds at high altitudes without afterburners. However, because their bypass ratios are both below 0.3, fuel consumption increases significantly during low-altitude subsonic flight, resulting in a substantial decrease in thrust. Furthermore, their thrust also decreases compared to turbojet engines during high-altitude flight. The American F135 and Russian AL-31F military turbofan engines have bypass ratios above 0.5, achieving thrusts of approximately 18-20 tons and 12.5 tons respectively during low-altitude subsonic flight. However, due to their larger bypass ratios, their thrust during climb, Thrust decreases significantly during acceleration and supersonic flight, especially at high altitudes. The American F135 has less than 8 tons of thrust, while the Russian AL-31F has only slightly more than 4 tons at an altitude of 20,000 meters. Because air density is highest at sea level and gradually decreases with altitude, the thrust of both turbofan and turbojet engines decreases at high altitudes. Furthermore, while turbofan engines are highly efficient at low-altitude subsonic flight, their efficiency drops significantly at high altitudes or supersonic speeds compared to turbojet engines. Therefore, for military turbofan engines operating in subsonic and transonic flight, a high bypass ratio is suitable for subsonic flight, allowing them to operate in turbofan mode. To increase thrust and reduce fuel consumption and noise, it is suitable to reduce the bypass ratio during climb, acceleration, and supersonic flight, operating as a low-bypass turbofan or near-turbojet engine to reduce drag and increase thrust. This means maintaining high thrust while ensuring low fuel consumption throughout almost the entire flight envelope. However, the bypass ratio and thermodynamic cycle characteristics of traditional turbofan engines are fixed; an engine can only operate in one mode and has its best performance only within a limited flight envelope. While the XA100 from GE and the XA101 from Pratt & Whitney exhibit different characteristics during operation... By adjusting the bypass ratio and airflow through adaptive fans, engines can increase the bypass ratio during takeoff and subsonic flight, operating as high-bypass turbofans, and decrease the bypass ratio during climb, acceleration, and supersonic flight, operating as low-bypass turbofans or near-turbojet engines. This improves engine performance under different operating conditions, maintaining high thrust and low fuel consumption. However, both types of engines have three bypass ducts and a series of adjustment devices, all of which change the bypass ratio and airflow internally. This not only makes the structure complex and increases the engine weight, but also keeps the frontal area unchanged, and the operation is not necessarily reliable. Summary of the Invention

[0003] The purpose of this invention is to provide a military variable cycle engine that can maintain high thrust and low fuel consumption at high and low altitudes and high and low speeds without changing the structure of a low bypass ratio turbofan engine.

[0004] This invention is implemented as follows: a variable cycle engine, comprising a supersonic inlet and a low-bypass turbofan engine, characterized in that the supersonic inlet is connected to an adjustable axisymmetric inlet, which is not connected to the turbofan engine and consists of adjustable vanes controlled by an actuation system and adjustment mechanism within a sealed casing; after startup and operation, according to the engine's operating scenario, the actuation system and adjustment mechanism are manipulated to change the opening degree of the adjustable vanes, so that the area of ​​the adjustable axisymmetric inlet opening increases during takeoff and subsonic flight, thereby increasing the engine's inlet bypass ratio and operating in maximum bypass ratio turbofan mode; during climb, acceleration, and supersonic flight, the area of ​​the adjustable axisymmetric inlet opening decreases, thereby decreasing the engine's inlet bypass ratio and operating in low bypass ratio turbofan or near-turbojet mode, improving the performance of the low-bypass turbofan engine under different operating conditions, maintaining high thrust and low fuel consumption, but its structure remains unchanged. Attached Figure Description

[0005] Figure 1 This is a schematic diagram of the variable cycle engine of the present invention when the intake bypass ratio is increased;

[0006] Figure 2 This is a schematic diagram of the variable cycle engine intake bypass ratio when the variable cycle engine of the present invention is smaller. Detailed Implementation

[0007] See attached document Figure 1 , 2 The variable cycle engine of the present invention includes a supersonic air intake 1, a sealing cover 2, an actuation system and adjustment mechanism 3, an adjustment plate 4, and a turbofan engine 5, etc. Figure 1 , 2These are schematic diagrams illustrating the changes in the opening area of ​​the adjustable axisymmetric air intake of the present invention, specifically when the opening area is increased or decreased. The supersonic air intake 1 can be a DSI or CARET intake, etc., selected as needed. It is subsequently connected to an adjustable axisymmetric air intake consisting of adjustable plates 4 controlled by an actuation system and adjustment mechanism 3 within a sealing cover 2. The two ends of the sealing cover 2 are connected to and sealed to the casings of the supersonic air intake 1 and the outer bypass duct of the turbofan engine 5 at both ends of the adjustable axisymmetric air intake. The actuation system and adjustment mechanism 3 can be various actuation systems and adjustment mechanisms found in currently known adjustable axisymmetric tail nozzles for fighter jets, such as hydraulically driven linkage mechanisms, etc., and there are multiple such mechanisms. The adjustment plates 4 function similarly to the fish scales in the adjustable axisymmetric tail nozzles of fighter jets. Multiple adjustment plates 4 constitute an adjustable axisymmetric air intake. The movable axisymmetric air intake channel has its axis aligned with the axis of the turbofan engine 5. The sealing between the adjusting plates 4 is the same as the sealing method between the fish scales in the adjustable axisymmetric tail nozzle of a fighter jet. Various methods can be used, such as interlocking sealing of the inner and outer adjusting plates, to ensure no air leakage during adjustment. The method can be selected as needed. The front end of the air intake channel composed of multiple adjusting plates 4 is fixedly connected to the supersonic air intake 1, while the rear end is in front of the air intake of the turbofan engine 5 but not connected to it. It is not fixed and is movable. Furthermore, the actuation system and the adjustment mechanism 3 are also connected to the adjusting plates 4. The turbofan engine 5 is a low-bypass turbofan engine. Because a bypass ratio below 0.3 results in a large decrease in thrust and an increase in fuel consumption during low-altitude subsonic flight, the bypass ratio of the turbofan engine 5 can be appropriately selected within the low-bypass ratio range of greater than 0.3 but not exceeding 1.0. Figure 1 , 2 The schematic diagram in the diagram is a cross-sectional view.

[0008] After the turbofan engine 5 with the above-described structure starts and runs, the actuation system and adjustment mechanism 3 are manipulated according to the engine's operating scenario to change the opening of the adjustment vane 4. This increases the area of ​​the adjustable axisymmetric air intake opening during takeoff and subsonic flight, making it as large as the air intake area of ​​the fan in the turbofan engine 5. At this time, the adjustable axisymmetric air intake becomes a cylindrical air intake, increasing the bypass ratio of the turbofan engine 5. It operates at maximum bypass ratio turbofan mode, resulting in high thrust and low fuel consumption. During climb, acceleration, and supersonic flight... When the adjustable axisymmetric intake opening area is reduced, the adjustable axisymmetric intake becomes a convergent intake. Although the bypass ratio of the turbofan engine 5 remains unchanged, its intake bypass ratio is reduced, the airflow of the outer bypass is reduced, and the airflow of the inner bypass is increased. When operating as a small bypass ratio turbofan or in a near-turbojet state, the wind resistance is small, the thrust is increased compared to when it is not adjusted, the decrease is small, and the fuel consumption rate is reduced. That is, high thrust and low fuel consumption are maintained, but its structure remains unchanged and its operation is reliable. The process is as described above.

[0009] During the above implementation process, when adjusting the area of ​​the adjustable axisymmetric air intake opening, it can be automatically controlled or manually controlled by the automatic control system according to its flight altitude, speed, etc., or both automatic and manual control are possible; the flight altitude and speed can be measured by relevant sensors or measuring instruments in the aircraft where the turbofan engine 5 is located; during the above implementation process, the total outlet pressure and total temperature of the compressor in the turbofan engine 5 and the turbine inlet temperature are within the safe operating range of the engine.

[0010] For example, after adopting the variable cycle engine technology of this invention, my country's WS15 military turbofan engine can increase the bypass ratio of the WS15 to any value not exceeding 1.0. During operation, by adjusting the area of ​​the adjustable axisymmetric air intake opening, the bypass ratio during air intake can be changed, allowing it to operate in maximum bypass ratio turbofan mode during low-altitude subsonic flight, resulting in increased thrust and reduced fuel consumption compared to the current WS15. During climb, acceleration, and supersonic flight, it operates in a low bypass ratio turbofan mode (less than 0.3) or near-turbojet mode, with low wind resistance and minimal thrust drop. It can cruise at high altitudes and supersonic speeds without afterburner, enabling the WS15 to maintain high thrust and low fuel consumption at both high and low altitudes and speeds.

[0011] For turbofan engines with a bypass ratio of 1.0 or higher that use supersonic inlets, such as the Russian NK-32 and other medium-bypass military turbofan engines, the variable cycle engine technology of this invention can also be used. For example, by adjusting the area of ​​the adjustable axisymmetric inlet opening, the thrust will be increased compared to when the inlet bypass ratio is reduced during climb, acceleration and supersonic flight, and the drag on the wind will be reduced, and the fuel consumption rate will be reduced.

Claims

1. A variable cycle engine, comprising a supersonic inlet (1) and a low-bypass turbofan engine (5), characterized in that the supersonic inlet (1) is connected to an adjustable axisymmetric inlet consisting of adjustable plates (4) controlled by an actuation system and adjustment mechanism (3) within a sealed casing (2), which is not connected to the low-bypass turbofan engine (5). The two ends of the sealed casing (2) are connected to and sealed to the casings of the outer bypass ducts of the supersonic inlet (1) and the low-bypass turbofan engine (5) at both ends of the adjustable axisymmetric inlet. There are multiple actuation systems and adjustment mechanisms (3). Multiple adjustable plates (4) form an axisymmetric inlet channel, the front end of which is fixedly connected to the supersonic inlet (1), and the rear end is in front of the inlet of the low-bypass turbofan engine (5) but not connected to it. It is not fixed, is movable, and the actuation system is not fixed. The system and adjustment mechanism (3) are also connected to the adjustment plate (4); when the low-bypass turbofan engine (5) is running after starting, the actuation system and adjustment mechanism (3) are manipulated according to the working scenario of the engine to change the opening of the adjustment plate (4), so that the area of ​​the adjustable axisymmetric air intake opening increases during takeoff and subsonic flight, so that the bypass ratio of the low-bypass turbofan engine (5) increases, and it works in the maximum bypass ratio turbofan state, with high thrust and low fuel consumption. During climb, acceleration and supersonic flight, the area of ​​the adjustable axisymmetric air intake opening decreases, so that the bypass ratio of the low-bypass turbofan engine (5) decreases, and it works in the low-bypass turbofan state or near turbojet state, with a small thrust drop, improving the performance of the low-bypass turbofan engine (5) in different working conditions, and maintaining high thrust and low fuel consumption.

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