Two-degree-of-freedom variable mounting angle inlet guide vanes for turbofans

Abstract

This invention provides a dual-degree-of-freedom variable installation angle inlet guide vane suitable for turbofans, comprising a main blade, secondary blade A, secondary blade B, a main shaft, a hollow secondary shaft A, and a hollow secondary shaft B. The main blade is mounted on the main shaft, and the hollow secondary shaft A is mounted on the secondary blade A, with the hollow secondary shaft A sleeved at one end of the main shaft, forming a first dual-degree-of-freedom rotation mechanism. The hollow secondary shaft B is mounted on the secondary blade B, with the hollow secondary shaft B sleeved at the other end of the main shaft, forming a second dual-degree-of-freedom rotation mechanism. The main blade, secondary blade A, and secondary blade B constitute the entire inlet guide vane. The flow area is adjusted by the main blade, and the flow direction is adjusted by the secondary blades A and B, thereby meeting the pre-rotation angle and flow area control required by the fan under different distortion modes. This ensures that the fan's working efficiency, compression capacity, and stability margin meet the working requirements of the entire compression system when in contact with distorted incoming flow.

Description

Technical Field

[0001] This invention belongs to the field of aviation power plant technology, specifically relating to a dual-degree-of-freedom variable installation angle inlet guide vane suitable for turbofans. Background Technology

[0002] With the continuous development of aviation technology, the requirements for the performance and stability of aero engines are becoming increasingly stringent. Intake distortion, as one of the key factors affecting engine performance, has received widespread attention. Meanwhile, with the widespread application of modern advanced aircraft propulsion systems, such as variable cycle engines, which can change the engine's operating state over a wide range to adapt to varying mission environment requirements, how to improve the operating environment of variable cycle engines affected by intake distortion has gradually become a very important issue.

[0003] Inlet distortion refers to the phenomenon where the inlet flow field parameters of an aero-engine do not match its design assumptions. Depending on the inlet flow field parameters, inlet distortion can be classified into several types, including total pressure distortion, total temperature distortion, and swirling distortion. These distortion types may occur individually or simultaneously during the actual operation of an aero-engine, exerting complex effects on engine performance and stability.

[0004] The causes of intake distortion are varied, mainly including intake separation caused by high angle of attack or high maneuverability of the aircraft, crosswind intake, steam intake during takeoff of carrier-based catapult aircraft, and exhaust gas intake 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 aero engine.

[0005] The effects of intake distortion on aero engines are mainly manifested in the following aspects: First, it can lead to the loss of compressor stability, causing forced vibration of compressor blades, and may even cause serious problems such as stall or surge; second, intake distortion can increase the load and thermal stress on the turbine, negatively affecting the turbine's performance and lifespan; finally, intake distortion can also affect the engine's thrust, fuel consumption and other performance indicators, reducing the overall performance of the engine.

[0006] Current research on the coupling effect between intake distortion and fan has yielded the following results:

[0007] The effect of vortex distortion on fans

[0008] Frohnapfel et al. from Virginia Tech conducted experimental research on a combined model of a bladed swirl distortion generator and a fan, finding that the fan weakens the upstream swirl, shifting the fan's pressure ratio efficiency characteristic curve to the lower left under the influence of the swirl. Sheoran et al. conducted numerical simulation research on a combined model of a chamber-type swirl distortion generator and a fan, showing that forward swirl shifts the fan curve towards lower flow rate and lower pressure ratio, while reverse swirl shifts the fan curve towards higher flow rate and higher pressure ratio. Zhou Youtian et al. conducted experimental research on the effect of the insert plate on the compressor, showing that swirl distortion is the main factor affecting the compressor's flow stability. Liu Hua et al. from Nanjing University of Aeronautics and Astronautics designed a bladed swirl distortion generator and conducted experimental research connected to a downstream low-speed compressor, finding that the rotor strengthens the forward swirl and weakens the reverse swirl, and that swirl distortion causes the rotor to stall prematurely.

[0009] The effect of total pressure distortion on the fan

[0010] Calogeras et al. conducted joint test runs of a distortion simulation board and the J85-GE-13 turbojet engine. The results showed that circumferential total pressure distortion significantly degraded the performance and stability boundary of the compressor components. The effect of radial distortion varied depending on its spatial location; tip radial total pressure distortion caused a significant downward shift in the stability boundary of the compressor components, while hub radial distortion had a limited impact. Jahnen et al. conducted joint tests of a five-stage high-pressure compressor and a total pressure distortion simulator, focusing on the changes in compressor near-stall signals under distortion. Their research found that the stall cluster developed from the distorted region, expanded circumferentially to the undistorted region, and gradually decayed. Chen Feng et al. from the China Aerodynamics Research and Development Center conducted joint tests of a distortion network and a fan, analyzing the dynamic signals before fan stall. Their research found that under circumferentially distorted inlet conditions, modal waves appeared before the compressor's rotating stall, and the unsteady disturbance was strongest at the trailing edge of the distorted region.

[0011] After fully understanding the different forms of distortion, targeted improvement measures can be designed based on their varying mechanisms of affecting fan performance: For the effect of swirling distortion on the fan inlet angle of attack, main and auxiliary blades can be designed to change the incoming flow direction, thereby reducing the fan rotor angle of attack; for the effect of total pressure distortion on fan flow rate and velocity, main and auxiliary blades can be designed to control the flow area. This allows for the adjustment of the distorted incoming flow through the dual-degree-of-freedom adjustable guide vanes in front of the rotor. Summary of the Invention

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

[0013] To achieve the above objectives, the present invention adopts the following technical solution: a two-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 mounted on the main shaft, the hollow secondary shaft A is mounted on the secondary blade A, and the hollow secondary shaft A is sleeved on one end of the main shaft, forming a first two-degree-of-freedom rotation mechanism. The hollow secondary shaft B is mounted on the secondary blade B, and the hollow secondary shaft B is sleeved on the other end of the main shaft, forming a second two-degree-of-freedom rotation mechanism. The main blade, secondary blade A, and secondary blade B constitute the entire inlet guide vane.

[0015] Furthermore, the tip of the secondary blade A is in contact with the base of the secondary blade B.

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

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

[0018] Furthermore, the adjustment methods for the first two-degree-of-freedom rotation mechanism and the second two-degree-of-freedom rotation mechanism are as follows:

[0019] 1) When the swirl distortion is mainly located in the tip of the blade, keep the installation angle of the main blade and the secondary blade B unchanged, and rotate the secondary blade A clockwise by 10° to 20°.

[0020] 2) When the vortex distortion mainly acts on the part from the leaf root to the middle of the leaf, keep the installation angle of the main blade and the secondary blade A unchanged, and rotate the secondary blade B clockwise by 5° to 10°.

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

[0022] 4) When the upstream distorted flow field of the fan is a total pressure swirling 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 within -10° to 15°.

[0023] Beneficial effects: By setting up a first two-degree-of-freedom rotation mechanism and a second two-degree-of-freedom rotation mechanism, the auxiliary blades A and B can be adjusted separately from both ends to improve the swirling distortion that occurs upstream of the fan. Furthermore, the fan's flow area can be adjusted by separately adjusting the installation angle of the main blade to improve the total pressure distortion that occurs upstream. At the same time, the installation angles of the main blade, blade A, and auxiliary blade B can be adjusted to regulate the fan's flow field and improve the combined total pressure swirling distortion that occurs upstream. This improves the distorted flow with different characteristics and intensities at different positions of the fan, ensuring that the fan has better working conditions under different distortion conditions. Attached Figure Description

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

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

[0026] Figure 3 This is a schematic diagram of the two-degree-of-freedom variable installation angle inlet guide vanes and the S2 flow surface of the fan stage, applicable to turbofans.

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

[0028] Figure 5 This is a schematic diagram of leaf adjustment when vortex distortion mainly affects the leaf root to the middle part of the leaf.

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

[0030] Figure 7 This is a schematic diagram of blade adjustment when the upstream distorted flow field of the fan is a combination of total pressure swirling and distortion.

[0031] Figure 8 This is a schematic diagram of the flow field under the combined distortion of total pressure swirling flow.

[0032] In the diagram: 1. Main blade, 2. Secondary blade A, 3. Secondary blade B, 4. Main shaft, 5. Hollow secondary shaft A, 6. Hollow secondary shaft B. Detailed Implementation

[0033] The invention will now be further explained with reference to the accompanying drawings.

[0034] like Figure 1-2As shown, the present invention provides a two-degree-of-freedom variable installation angle inlet guide vane suitable for turbofans, 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 mounted on the main shaft 4, and the hollow secondary shaft A 5 is mounted on the secondary blade A 2. The hollow secondary shaft A 5 is sleeved on one end of the main shaft 4, forming a first two-degree-of-freedom rotation mechanism. The hollow secondary shaft B 6 is mounted 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 two-degree-of-freedom rotation mechanism. The tip of the secondary blade A 2 is in contact with the base of the secondary blade B 3, and the secondary blade A 2 and the secondary blade B 3 are located on the same side. The main blade 1, the secondary blade A 2, and the secondary blade B 3 constitute the entire inlet guide vane.

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

[0037] Main blade design: In order to avoid the flow complexity caused by using overly complex blade shapes, the main blade 1 in this scheme adopts a three-dimensional blade shape without curvature.

[0038] Sub-blade design: The radial height of sub-blades A2 and B3 is the radial height covered by the flow separation vortex at the blade tip of the fan operating under the combined distortion of total pressure swirl, such as... Figure 8 As shown, the fan surface exhibits flow separation vortices under combined distortion. The axial and radial dimensions of these vortices can be used to determine the axial and radial dimensions of the secondary blades. Based on this, the design is as follows: the radial length of secondary blade A2 accounts for 25%–30% of the total radial length, and the axial length of secondary blade A2 accounts for 40% of the total axial length of the inlet guide vane. The radial length of secondary blade B3 accounts for 70%–75% of the total radial length, and the axial length accounts for approximately 30% of the total axial length of the inlet guide vane. This design allows the adjustable guide vane to control the flow field even under strong distortion, effectively suppressing the generation of flow separation vortices on the fan surface.

[0039] like Figure 3 The diagram shows a two-degree-of-freedom variable installation angle inlet guide vane and the S2 flow surface of the fan stage, illustrating the installation position of the adjustable inlet guide vane.

[0040] like Figure 4-7 As shown, the adjustment methods for the first two-degree-of-freedom rotational mechanism and the second two-degree-of-freedom rotational mechanism are as follows:

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

[0042] When the swirling distortion mainly acts on the part from the leaf root to the leaf center, keep the installation angle of the main blade 1 and the secondary blade A 2 unchanged, and rotate the secondary blade B 3 clockwise by 5° to 10° to adjust the pre-swirl angle in the direction from the leaf center to the leaf root, so as to improve the swirling distortion from the leaf center to the leaf root.

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

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

[0045] This invention is based on the blade inlet velocity triangle theory. It uses a two-degree-of-freedom variable-angle inlet guide vane, applicable to turbofans, to adjust the flow field, changing the angle of attack at the fan inlet, reducing flow separation, and preventing stall. Simultaneously, adjustable-angle auxiliary blades A2 and B3 are designed to improve tip flow under different flow separation conditions at different blade heights, along with a main blade 1 to adjust the flow area. This allows for adjustment of the radial characteristics of the flow field in front of the fan, satisfying the fan's pre-swirl angle and flow area control requirements under different distortion patterns. This ensures that the fan's efficiency, compression capacity, and stability margin meet the operational requirements of the entire compression system when encountering distorted incoming flow.

[0046] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for adjusting the inlet guide vanes of a turbofan with a two-degree-of-freedom variable installation angle, characterized in that, include: The main blade (1), secondary blade A (2), secondary blade B (3), main shaft (4), hollow secondary shaft A (5), and hollow secondary shaft B (6) are 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) to form a first two-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) to form a second two-degree-of-freedom rotation mechanism. The main blade (1), secondary blade A (2), and secondary blade B (3) constitute the entire inlet guide vane. The adjustment methods for the first two-degree-of-freedom rotation mechanism and the second two-degree-of-freedom rotation mechanism are as follows: 1) When the swirling distortion is mainly located at the tip of the blade, keep the installation angle of the main blade (1) and the secondary blade B (3) unchanged, and rotate the secondary blade A (2) clockwise by 10° to 20°; 2) When the swirling distortion mainly acts on the part from the root to the middle of the blade, keep the installation angle of the main blade (1) and the secondary blade A (2) unchanged, and rotate the secondary blade B (3) clockwise by 5° to 10°; 3) When total pressure distortion occurs upstream of the fan, keep the installation angle of the secondary blade A (2) and the secondary blade B (3) unchanged, and rotate the main blade (1) clockwise by 10° to 25° to reduce the flow area; 4) When the distorted flow field upstream of the fan is a total pressure swirling distortion, adjust the installation angle of the secondary blade A (2) between ±10°, adjust the installation angle of the secondary blade B (3) between ±5°, and adjust the installation angle of the main blade between -10° and 15°.

2. The method for adjusting the inlet guide vanes of a turbofan with a two-degree-of-freedom variable installation angle according to claim 1, characterized in that, The tip of the secondary leaf A (2) is in contact with the base of the secondary leaf B (3).

3. The method for adjusting the inlet guide vanes of a turbofan with a two-degree-of-freedom variable installation angle according to claim 1, characterized in that, The sum of the axial lengths of the secondary blades A (2) and B (3) is equal to the axial length of the main blade (1).

4. The method for adjusting the inlet guide vanes of a turbofan with a two-degree-of-freedom variable installation angle 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 total axial length of the entire inlet guide vane.

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