Three-degree-of-freedom variable installation angle inlet guide vanes suitable for variable circulation fans

Abstract

This invention provides a three-degree-of-freedom variable installation angle inlet guide vane suitable for variable cycle fans, comprising: a main blade, a first auxiliary blade, a second auxiliary blade, a main shaft, a first hollow auxiliary shaft, and a second hollow auxiliary shaft. The main blade is mounted on the main shaft, the first hollow auxiliary shaft is mounted on the first auxiliary blade, and the second hollow auxiliary shaft is mounted on the second auxiliary blade. The second hollow auxiliary shaft is sleeved on the first hollow auxiliary shaft, and the first hollow auxiliary shaft is sleeved on the main shaft, forming a three-degree-of-freedom rotating mechanism. The main blade, the first auxiliary blade, and the second auxiliary blade constitute the entire inlet guide vane. By using the main blade to adjust the flow direction within the entire flow channel, and by using the second auxiliary blade to control the adverse flow field factors caused by changes in the bypass ratio of the variable cycle engine, and by using the first auxiliary blade to control various adverse flow field factors caused by contact intake distortion, the performance of the variable cycle fan subjected to different distortion forms under different variable cycle operating conditions is improved.

Description

Technical Field

[0001] This invention belongs to the field of aviation power plant technology, specifically relating to a three-degree-of-freedom variable installation angle inlet guide vane suitable for variable cycle fans. 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 swirl 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 adjust the radial characteristics of the flow field before and after the fan by separately controlling the guide vane profile, so as to meet the pre-swirl angle control required by the variable circulation fan under different distortion modes, and ensure that the working efficiency, compression capacity, stability margin, etc. of the variable circulation fan can meet the working requirements of the entire compression system when it comes into contact with distorted incoming flow of different intensities under different bypass ratio conditions. This invention provides a three-degree-of-freedom variable installation angle inlet guide vane suitable for variable circulation fans.

[0013] To achieve the above objectives, the present invention adopts the following technical solution: a three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan, comprising: a main blade, a first auxiliary blade, a second auxiliary blade, a main shaft, a first hollow auxiliary shaft, and a second hollow auxiliary shaft;

[0014] The main blade is mounted on the main shaft, the first hollow secondary shaft is mounted on the first secondary blade, the second hollow secondary shaft is mounted on the second secondary blade, and the second hollow secondary shaft is sleeved on the first hollow secondary shaft. The first hollow secondary shaft is sleeved on the main shaft, forming a three-degree-of-freedom rotation mechanism. The main blade, the first secondary blade, and the second secondary blade constitute the entire inlet guide vane.

[0015] Furthermore, the tips of the first and second secondary blades are in contact with the base of the main blade, respectively.

[0016] Furthermore, the height of the second blade is the radial height covered by the flow separation vortex at the blade tip of the fan operating under the influence of the total pressure swirling composite distortion.

[0017] Furthermore, the axial length of the second auxiliary blade is 40% of the total length of the inlet guide vane blade.

[0018] Furthermore, the adjustment method for the three-degree-of-freedom rotation mechanism is as follows:

[0019] 1) When the variable circulation fan is in contact with the intake distortion distributed at the blade root under the condition of small bypass ratio, keep the first set of blades unchanged, rotate the second set of blades 5° counterclockwise, and at the same time rotate the main blades 5° to 10° counterclockwise.

[0020] 2) When the variable circulation fan is in operation under the design bypass ratio or high bypass ratio conditions, it comes into contact with the intake distortion that is distributed throughout the flow channel and has different degrees of distortion in the radial direction. Keep the second auxiliary blade unchanged, rotate the first auxiliary blade counterclockwise by 10° to 15°, and at the same time rotate the main blade counterclockwise by 5°.

[0021] 3) When the variable circulation fan is operating under low bypass ratio conditions and the blade tip is distorted, keep the main blade unchanged, rotate the second auxiliary blade 5° to 10° counterclockwise, and at the same time rotate the first auxiliary blade 5° counterclockwise.

[0022] Beneficial effects: Based on the traditional adjustable guide vanes applicable to variable cycle turbofan engines, this invention incorporates variable geometry airfoil design to construct a three-degree-of-freedom variable installation angle inlet guide vane. This guide vane inherits the advantages of traditional adjustable guide vanes while ensuring that the aero-engine fan maintains high performance under different inlet distortion conditions. At the same time, the three-degree-of-freedom rotating mechanism adjustment method allows the three-degree-of-freedom variable installation angle inlet guide vane to be used to improve the performance of variable cycle fans subjected to different distortion forms under different variable cycle operating conditions. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the structure of a three-degree-of-freedom adjustable inlet guide vane.

[0024] Figure 2 This is a schematic diagram of the assembly of a three-degree-of-freedom adjustable inlet guide vane.

[0025] Figure 3 This is a schematic diagram of the three-degree-of-freedom adjustable inlet guide vane and the S2 flow surface of the fan stage.

[0026] Figure 4 This is a schematic diagram of blade adjustment when contacting the intake distortion distributed at the blade root under low bypass ratio conditions.

[0027] Figure 5 This is a schematic diagram of blade adjustment when encountering intake distortion that is distributed throughout the entire flow channel and has different degrees of distortion in the radial direction during operation under design bypass ratio or high bypass ratio conditions.

[0028] Figure 6 This is a schematic diagram of blade adjustment when operating under low bypass ratio conditions and encountering tip distortion.

[0029] Figure 7 This is a schematic diagram of the flow separation near the stall point of the fan during distortion.

[0030] In the diagram: 1. Main blade, 2. First secondary blade, 3. Second secondary blade, 4. Main shaft, 5. First hollow secondary shaft, 6. Second hollow secondary shaft. Detailed Implementation

[0031] The invention will now be further explained with reference to the accompanying drawings.

[0032] like Figure 1-2 As shown, the present invention provides a three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan, comprising: a main blade 1, a first auxiliary blade 2, a second auxiliary blade 3, a main shaft 4, a first hollow auxiliary shaft 5, and a second hollow auxiliary shaft 6;

[0033] The main blade 1 is mounted on the main shaft 4, the first hollow secondary shaft 5 is mounted on the first secondary blade 2, and the second hollow secondary shaft 6 is mounted on the second secondary blade 3. The tips of the first secondary blade 2 and the second secondary blade 3 are in contact with the base of the main blade 1, and the second hollow secondary shaft 6 is sleeved on the first hollow secondary shaft 5. The first hollow secondary shaft 5 is sleeved on the main shaft 4, forming a three-degree-of-freedom rotation mechanism. The main blade 1, the first secondary blade 2, and the second secondary blade 3 constitute the entire inlet guide vane.

[0034] In this embodiment, under different forms of distortion, the flow separation at the root of the variable recirculation fan is relatively small. The flow separation is gradually aggravated along the blade height due to the distortion. Therefore, the second blade 3 is set above the blade bottom of the blade 1. At the same time, during the change of the bypass ratio of the variable recirculation fan, the flow at the blade tip is mainly affected by the change of the split ratio in the blade tip direction. Therefore, the first blade 2 is also set above the blade bottom of the blade 1. In order to keep the flow field in front of the fan as simple as possible, the blade shape of the entire three-degree-of-freedom variable installation angle inlet guide vane adopts a simple symmetrical blade shape without curvature.

[0035] 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.

[0036] Determining the blade profile and installation position of the secondary blades: The radial height of the secondary blades needs to be determined based on the flow conditions at the fan blade tip. In this design, the heights of the first secondary blade 2 and the second secondary blade 3 are the radial heights covered by the flow separation vortices at the blade tip of the fan operating under the influence of the combined distortion of total pressure swirl. The axial length distribution of the secondary blades should be determined by referring to the flow separation conditions near the fan's stall point under the same distortion. Figure 7 It can be seen that the flow separation region caused by distortion begins at about 40% of the blade's axial length. Therefore, in this design, the axial length of the second blade 3 is 40% of the overall blade length, and the axial length of the first blade 2 is 50% of the overall blade length.

[0037] like Figure 3 The diagram shows a three-degree-of-freedom adjustable inlet guide vane and the meridional flow surface of the fan stage. The adjustable inlet guide vane is located in front of the fan stage. The variable circulation fan stage consists of a rotor and a stator. Behind the fan stage are the variable circulation fan splitter and the mode selection valve (MSV).

[0038] like Figure 4-6 As shown, the adjustment method for the three-degree-of-freedom rotary mechanism is as follows:

[0039] When the variable recirculation fan comes into contact with the intake distortion distributed at the blade root under low bypass ratio conditions, the second set of blades remains unchanged, and the first set of blades is rotated 5° counterclockwise to adapt to the increased angle of attack caused by the low bypass ratio conditions. At the same time, the main blades are rotated 5° to 10° counterclockwise to adjust the intake distortion located in the region from the blade root to the blade center.

[0040] When a variable-circulation fan operates under designed bypass ratio or high bypass ratio conditions, it encounters intake distortion distributed throughout the entire flow channel with varying degrees of radial distortion. The first set of blades remains unchanged, while the second set of blades is rotated 10°–15° counterclockwise to accommodate the larger angle of attack at the blade tip. Simultaneously, the main blades are rotated 5° counterclockwise to accommodate distortion distributed in the middle and root of the blades. The designed bypass ratio is between that of a small and a large bypass ratio, representing the most efficient operating condition.

[0041] When the variable circulation fan is operating under low bypass ratio conditions and is experiencing tip distortion, keep the main blade unchanged and rotate the first auxiliary blade 5° to 10° counterclockwise, while simultaneously rotating the second auxiliary blade 5° counterclockwise, to adjust the flow field under these conditions.

[0042] This invention uses the main blade 1 to adjust the flow direction within the entire flow channel and drives the second auxiliary blade 3 to rotate via the second hollow auxiliary shaft 6, thereby controlling the adverse flow field factors caused by the change in bypass ratio of the variable cycle engine. At the same time, it drives the first auxiliary blade 2 to rotate via the first hollow auxiliary shaft 5, thereby controlling various adverse flow field factors caused by contact intake distortion, thus improving the performance of the variable cycle fan under different distortion modes under different variable cycle operating conditions.

[0043] 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 three-degree-of-freedom variable installation angle variable circulation fan, characterized in that, include: The main blade (1), the first auxiliary blade (2), the second auxiliary blade (3), the main shaft (4), the first hollow auxiliary shaft (5), and the second hollow auxiliary shaft (6) are arranged on the main shaft (4), the first hollow auxiliary shaft (5) is arranged on the first auxiliary blade (2), the second hollow auxiliary shaft (6) is arranged on the second auxiliary blade (3), and the second hollow auxiliary shaft (6) is sleeved on the first hollow auxiliary shaft (5). The first hollow auxiliary shaft (5) is sleeved on the main shaft (4), forming a three-degree-of-freedom rotation mechanism. The main blade (1), the first auxiliary blade (2), and the second auxiliary blade (3) constitute the entire inlet guide vane. The adjustment method of the three-degree-of-freedom rotating mechanism is as follows: 1) When the variable circulation fan is in contact with the intake distortion distributed at the blade root under the condition of small bypass ratio, keep the first auxiliary blade unchanged, rotate the second auxiliary blade 5° counterclockwise, and at the same time rotate the main blade 5° to 10° counterclockwise; 2) When the variable circulation fan is in contact with the intake distortion distributed throughout the entire flow channel and with different degrees of distortion in the radial direction under the condition of design bypass ratio or large bypass ratio, keep the second auxiliary blade unchanged, rotate the first auxiliary blade 10° to 15° counterclockwise, and at the same time rotate the main blade 5° counterclockwise; 3) When the variable circulation fan is in contact with the blade tip distortion under the condition of small bypass ratio, keep the main blade unchanged, rotate the second auxiliary blade 5° to 10° counterclockwise, and at the same time rotate the first auxiliary blade 5° counterclockwise.

2. The method for adjusting the inlet guide vanes of a three-degree-of-freedom variable installation angle applicable to a variable circulation fan according to claim 1, characterized in that, The tips of the first secondary leaf (2) and the second secondary leaf (3) are in contact with the bottom of the main leaf (1).

3. The method for adjusting the inlet guide vanes of a three-degree-of-freedom variable installation angle applicable to a variable circulation fan according to claim 1, characterized in that, The height of the second blade (3) is the radial height covered by the flow separation vortex of the fan operating under the influence of total pressure swirling composite distortion at the blade tip.

4. The method for adjusting the inlet guide vanes of a three-degree-of-freedom variable installation angle applicable to a variable circulation fan according to claim 1, characterized in that, The axial length of the second auxiliary blade (3) is 40% of the total length of the inlet guide vane blade.

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