Double-degree-of-freedom variable mounting angle inlet guide vane suitable for turbofan

Abstract

The invention provides a double-degree-of-freedom variable mounting angle inlet guide vane suitable for a turbofan, which comprises a main blade, an auxiliary blade A, an auxiliary blade B, a main shaft, a hollow auxiliary shaft A and a hollow auxiliary shaft B. The main blade is arranged on the main shaft, the hollow auxiliary shaft A is arranged on the auxiliary blade A, and the hollow auxiliary shaft A is sleeved at one end of the main shaft to form a first double-degree-of-freedom rotating mechanism; the hollow auxiliary shaft B is arranged on the auxiliary blade B, the hollow auxiliary shaft B is connected to the other end of the main shaft in a sleeving mode to form a second two-degree-of-freedom rotating mechanism, the main blade, the auxiliary blade A and the auxiliary blade B form the whole inlet guide blade, the circulation area is adjusted through the main blade, and the flowing direction is adjusted through the auxiliary blade A and the auxiliary blade B; therefore, the pre-rotation angle and the through-flow area required by the fan under the action of different distortion forms are regulated and controlled, and the working efficiency, the compression capacity, the stability margin and the like of the fan in contact with the distortion incoming flow can meet the working requirements of the whole compression system.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation power devices, and in particular relates to a double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan. Background Art

[0002] With the continuous development of aviation technology, the performance and stability requirements of aircraft engines are increasing day by day, and intake distortion, as one of the key factors affecting engine performance, has received extensive attention. At the same time, with the widespread application of modern advanced aircraft power systems, such as variable cycle engines, which can change the working state of the engine within a large range to adapt to the changing mission environment requirements, how to improve the working environment of variable cycle engines affected by intake distortion has gradually become a very important topic.

[0003] Intake distortion refers to the phenomenon that the inlet flow field parameters of an aircraft engine are inconsistent with its design assumptions. According to the different inlet flow field parameters, intake distortion can be divided into multiple types such as total pressure distortion, total temperature distortion, and swirl distortion. These types of distortion may appear alone or simultaneously during the actual operation of an aircraft engine, which has a complex impact on the performance and stability of the engine.

[0004] There are many reasons for intake distortion, including inlet separation caused by high-angle-of-attack or high-maneuver flight, crosswind intake, steam inhalation during takeoff of carrier-based catapult aircraft, and exhaust gas inhalation when the aircraft launches missiles. For variable-cycle engines with adjustable bypass ratio, distortion may have a greater impact under different operating conditions. These impacts will lead to changes in the inlet flow field parameters, which in turn will cause unstable operation of the aircraft engine.

[0005] The impact of intake distortion on aircraft engines is mainly manifested in the following aspects: first, it will lead to loss of compressor stability, causing forced vibration of the compressor blades, and may even cause serious problems such as stall or surge; second, intake distortion will increase the load and thermal stress of the turbine, and have a negative impact on the performance and life of the turbine; finally, intake distortion will also affect the engine's thrust, fuel consumption and other performance indicators, reducing the overall performance of the engine.

[0006] At present, the following results have been obtained in the research on the coupling effect of intake distortion and fan:

[0007] Effect of swirl distortion on fans

[0008] Frohnapfel et al. from Virginia Tech in the United States conducted an experimental study on the combined model of blade-type swirl distortion generator and fan, and found that the fan has a certain weakening effect on the upstream swirl, and the fan pressure ratio efficiency characteristic curve moves to the lower left under the influence of the swirl. Sheoran et al. conducted a numerical simulation study on the combined model of chamber-type swirl distortion generator and fan. The results showed that the forward swirl makes the fan curve move in the direction of small flow and small pressure ratio, and the reverse swirl makes the fan curve tend to the direction of large flow and large pressure ratio. Zhou Youtian et al. conducted an experimental study on the influence of the plug plate on the compressor. The results showed that swirl distortion is the main factor affecting the flow stability of the compressor. Liu Hua et al. from Nanjing University of Aeronautics and Astronautics designed a blade-type swirl distortion generator and connected it to the downstream low-speed compressor for experimental research. The study found that the rotor has a strengthening effect on the forward swirl and a weakening effect on the reverse swirl, and the swirl distortion causes the rotor to stall early.

[0009] Effect of total pressure distortion on fan

[0010] Calogeras et al. conducted a joint test of the distortion simulation board and the J85-GE-13 turbojet engine. The test results showed that the circumferential total pressure distortion had a significant deteriorating effect on the performance and stability boundary of the compressor components in the engine; the influence of radial distortion varied with the change of its spatial position. The radial total pressure distortion at the blade tip caused the stability boundary of the compressor components to move downward significantly, while the radial distortion of the hub had a limited effect on the stability boundary of the compressor components. Jahnen et al. conducted a joint test of a 5-stage high-pressure compressor and a total pressure distortion simulator, and focused on the change of the compressor near-stall point signal under the influence of distortion. The study found that the stall group started to develop from the distortion zone, expanded circumferentially to the non-distortion zone and gradually attenuated. Chen Feng et al. from the China Aerodynamics Research and Development Center conducted a joint test of the distortion net and the fan, and analyzed the dynamic signal before the fan stalled. The study found that under the condition of circumferential distortion inlet, modal waves appeared before the compressor rotating stall, and the unsteady disturbance was the strongest at the trailing edge of the distortion zone.

[0011] After fully understanding the different distortion forms, targeted improvement measures can be designed according to the different mechanisms that affect the fan performance: according to the influence mechanism of swirl distortion on the fan inlet angle of attack, the main and auxiliary blades that can change the flow direction of the incoming flow and thus reduce the fan rotor angle of attack are designed; according to the influence mechanism of total pressure distortion on the fan flow and flow velocity, the main and auxiliary blades that can control the flow area are designed. In this way, the distorted incoming flow can be adjusted through the double-degree-of-freedom installation angle adjustable guide vanes in front of the rotor. Summary of the invention

[0012] The purpose of the present invention is to improve the intake distortion of a turbofan engine, ensure that the fan has better working conditions under different distortion conditions, and provide a dual-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan;

[0013] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: a double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan, comprising: a main blade, an auxiliary blade A, an auxiliary blade B, a main shaft, a hollow auxiliary shaft A and a hollow auxiliary shaft B;

[0014] The main blade is arranged on the main shaft, the hollow secondary shaft A is arranged on the secondary blade A, and the hollow secondary shaft A is sleeved on one end of the main shaft to form a first double-degree-of-freedom rotation mechanism, the hollow secondary shaft B is arranged on the secondary blade B, and the hollow secondary shaft B is sleeved on the other end of the main shaft to form a second double-degree-of-freedom rotation mechanism, and the main blade, the secondary blade A and the secondary blade B constitute the entire inlet guide vane.

[0015] Furthermore, the blade top of the auxiliary blade A is in contact with the blade bottom of the auxiliary blade B.

[0016] Furthermore, the sum of the axial lengths of the auxiliary blade A and the auxiliary blade B is equal to the axial length of the main blade.

[0017] Furthermore, the radial length of the auxiliary blade A accounts for 25% to 30% of the total radial length of the entire inlet guide vane, and the axial length of the auxiliary blade A accounts for 40% of the axial length of the entire inlet guide vane.

[0018] Furthermore, the adjustment method of the first dual-degree-of-freedom rotation mechanism and the second dual-degree-of-freedom rotation mechanism is:

[0019] 1) When the swirl distortion is mainly located at the blade tip, keep the installation angles of the main blade and the auxiliary blade B unchanged, and rotate the auxiliary blade A 10° to 20° clockwise;

[0020] 2) When the swirl distortion mainly acts on the blade root to the middle of the blade, keep the installation angles of the main blade and the auxiliary blade A unchanged, and rotate the auxiliary blade B 5° to 10° clockwise;

[0021] 3) When total pressure distortion occurs upstream of the fan, keep the installation angles of auxiliary blades A and B unchanged, and rotate the main blades 10° to 25° clockwise to reduce the flow area;

[0022] 4) When the distorted flow field upstream of the fan is a total pressure swirl combined distortion, adjust the installation angle of the auxiliary blade A within ±10°, adjust the installation angle of the auxiliary blade B within ±5°, and adjust the installation angle of the main blade between -10° and 15°.

[0023] Beneficial effect: The present invention arranges a first dual-degree-of-freedom rotation mechanism and a second dual-degree-of-freedom rotation mechanism, so that the auxiliary blades A and the auxiliary blades B can be adjusted separately from both ends to improve the swirl distortion occurring upstream of the fan, and the flow area of ​​the fan can be adjusted by adjusting the installation angle of the main blades alone to improve the total pressure distortion occurring upstream. At the same time, the installation angles of the main blades, blades A and auxiliary blades B can be adjusted at the same time to adjust the fan flow field to improve the total pressure swirl combined distortion occurring upstream, thereby improving the distorted incoming flows with different characteristics and intensities at different positions of the fan, and ensuring that the fan has better working conditions under different distortion conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a schematic diagram of the structure of a dual-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan.

[0025] Figure 2 It is a schematic diagram of the assembly of a dual-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan.

[0026] Figure 3 It is a schematic diagram of the double-degree-of-freedom variable installation angle inlet guide vane and fan stage S2 flow surface suitable for a turbofan.

[0027] Figure 4 This is a schematic diagram of blade adjustment when the swirl distortion is mainly located at the blade tip.

[0028] Figure 5 This is a schematic diagram of blade adjustment when the swirl distortion mainly acts on the part from the root to the middle of the blade.

[0029] Figure 6 It is a schematic diagram of blade adjustment when total pressure distortion occurs upstream of the fan.

[0030] Figure 7 It is a schematic diagram of blade adjustment when the distorted flow field upstream of the fan is a total pressure swirl combined distortion.

[0031] Figure 8 It is a schematic diagram of the flow field under the action of total pressure swirl compound distortion.

[0032] In the figure: 1. main blade, 2. auxiliary blade A, 3. auxiliary blade B, 4. main shaft, 5. hollow auxiliary shaft A, 6. hollow auxiliary shaft B. DETAILED DESCRIPTION

[0033] The present invention will be further explained below in conjunction with the accompanying drawings.

[0034] like Figure 1-2As shown, the present invention provides a dual-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan, comprising: a main blade 1, an auxiliary blade A 2, an auxiliary blade B 3, a main shaft 4, a hollow auxiliary shaft A 5 and a hollow auxiliary shaft B 6;

[0035] The main blade 1 is arranged on the main shaft 4, the hollow secondary shaft A5 is arranged on the secondary blade A2, and the hollow secondary shaft A5 is sleeved on one end of the main shaft 4 to form a first double-degree-of-freedom rotation mechanism, the hollow secondary shaft B6 is arranged on the secondary blade B3, and the hollow secondary shaft B6 is sleeved on the other end of the main shaft 4 to form a second double-degree-of-freedom rotation mechanism, the blade top of the secondary blade A2 is in contact with the blade bottom of the secondary blade B3, and the secondary blade A2 and the secondary blade B3 are located on the same side, and the main blade 1, the secondary blade A2 and the secondary blade B3 constitute the entire inlet guide vane.

[0036] In this embodiment, the auxiliary blade A2 and the auxiliary blade B3 are respectively located outside the casing and the hub, and are controlled by independent actuating mechanisms. Their adjustment actions are independent of each other. In order to make the flow field in front of the fan as simple as possible, the blade shape of the entire double-degree-of-freedom variable installation angle inlet guide vane suitable for improving intake distortion of aircraft engines adopts a simple symmetrical blade shape without curvature.

[0037] Main blade design: In order to avoid using an overly complex blade shape that would complicate the flow, the main blade 1 in this solution adopts a three-dimensional blade shape without curvature.

[0038] Auxiliary blade design: The radial height of auxiliary blade A2 and auxiliary blade B3 is the radial height covered by the flow separation vortex when the fan is working under the influence of total pressure swirl compound distortion at the blade tip, such as Figure 8 As shown, it is shown that when the fan surface is subjected to the compound distortion, the separation vortex shown in the figure will appear. The axial and radial dimensions of these separation vortices can be used as the basis for determining the axial and radial sizes of the auxiliary blades. Therefore, the design is as follows: the radial length of the auxiliary blade A2 accounts for 25% to 30% of the total radial length, and the axial length of the auxiliary blade A2 accounts for 40% of the axial length of the entire inlet guide vane. The radial length of the auxiliary blade B3 accounts for 70% to 75% of the total radial length, and the axial length accounts for about 30% of the axial length of the entire inlet guide vane. This design enables the adjustable guide vane to achieve control of the flow field under the action of strong distortion, and effectively curbs the generation of flow separation vortices on the fan surface.

[0039] like Figure 3 The figure shows a schematic diagram of the inlet guide vane with a double degree of freedom and variable installation angle and the fan stage S2 flow surface, which shows the installation position of the inlet adjustable guide vane.

[0040] like Figure 4-7 As shown, the adjustment method of the first dual-degree-of-freedom rotation mechanism and the second dual-degree-of-freedom rotation mechanism is:

[0041] When the swirl distortion is mainly located at the blade tip, keep the installation angles of the main blade 1 and the auxiliary blade B 3 unchanged, and rotate the auxiliary blade A 2 10° to 20° clockwise to make the flow direction at the blade tip consistent, so as to prevent the occurrence of a local large angle of attack or even a local stall at the rotor inlet blade tip;

[0042] When the swirl distortion mainly acts on the part from the blade root to the blade center, keep the installation angles of the main blade 1 and the auxiliary blade A2 unchanged, rotate the auxiliary blade B3 by 5° to 10° clockwise to adjust the pre-swirl angle from the blade center to the blade root, so as to improve the swirl distortion from the blade center to the blade root;

[0043] When total pressure distortion occurs upstream of the fan, keep the installation angles of auxiliary blades A2 and B3 unchanged, and rotate the main blade 1 10° to 25° clockwise to reduce the flow area and improve the total pressure distortion;

[0044] When the distorted flow field upstream of the fan is a total pressure swirl combined distortion, the installation angle of the auxiliary blade A2 can be adjusted between ±10°, the installation angle of the auxiliary blade B3 can be adjusted between ±5°, and the installation angle of the main blade can be adjusted between -10° and 15°, so as to adjust the pre-swirl angle and the flow channel area to improve the total pressure swirl combined distortion.

[0045] The present invention is based on the blade inlet velocity triangle theory, and adjusts the flow field through the entire double-degree-of-freedom variable installation angle inlet guide vane suitable for the turbofan to change the angle of attack at the fan inlet, reduce flow separation, and prevent stalling. At the same time, according to the different flow separation conditions of different blade heights, the adjustable installation angle auxiliary blade A2 and auxiliary blade B3 are designed to improve the tip flow conditions, and the main blade 1 is used to adjust the flow area, so as to adjust the radial characteristics of the fan front flow field to meet the fan's required pre-rotation angle and flow area control under different distortion forms, and ensure that the fan's working efficiency, compression capacity, stability margin, etc. when contacting the distorted incoming flow can meet the working requirements of the entire compression system.

[0046] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A dual-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan, characterized in that: include: A main blade (1), an auxiliary blade A (2), an auxiliary blade B (3), a main shaft (4), a hollow auxiliary shaft A (5) and a hollow auxiliary shaft B (6); The main blade (1) is arranged on the main shaft (4), the hollow secondary shaft A (5) is arranged on the secondary blade A (2), and the hollow secondary shaft A (5) is sleeved on one end of the main shaft (4), forming a first double-degree-of-freedom rotation mechanism, the hollow secondary shaft B (6) is arranged on the secondary blade B (3), and the hollow secondary shaft B (6) is sleeved on the other end of the main shaft (4), forming a second double-degree-of-freedom rotation mechanism, and the main blade (1), the secondary blade A (2) and the secondary blade B (3) constitute the entire inlet guide vane.

2. The double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan according to claim 1, characterized in that: The blade top of the auxiliary blade A (2) contacts the blade bottom of the auxiliary blade B (3).

3. The double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan according to claim 1, characterized in that: The sum of the axial lengths of the auxiliary blade A (2) and the auxiliary blade B (3) is equal to the axial length of the main blade (1).

4. The double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan according to claim 1, characterized in that: The radial length of the auxiliary blade A (2) accounts for 25% to 30% of the total radial length of the entire inlet guide vane, and the axial length of the auxiliary blade A (2) accounts for 40% of the axial length of the entire inlet guide vane.

5. The double-degree-of-freedom variable installation angle inlet guide vane suitable for a turbofan according to claim 1, characterized in that: The adjustment method of the first dual-degree-of-freedom rotation mechanism and the second dual-degree-of-freedom rotation mechanism is: 1) When the swirl distortion is mainly located at the blade tip, the installation angles of the main blade (1) and the auxiliary blade B (3) are kept unchanged, and the auxiliary blade A (2) is rotated 10° to 20° in a clockwise direction; 2) When the swirl distortion mainly acts on the portion from the blade root to the middle of the blade, the installation angles of the main blade (1) and the auxiliary blade A (2) are kept unchanged, and the auxiliary blade B (3) is rotated 5° to 10° in a clockwise direction; 3) When total pressure distortion occurs upstream of the fan, keep the installation angles of auxiliary blades A (2) and B (3) unchanged and rotate the main blade (1) 10° to 25° clockwise to reduce the flow area; 4) When the distorted flow field upstream of the fan is a total pressure swirl combined distortion, adjust the installation angle of the auxiliary blade A (2) within ±10°, adjust the installation angle of the auxiliary blade B (3) within ±5°, and adjust the installation angle of the main blade within -10° to 15°.

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