Three-degree-of-freedom variable mounting angle inlet guide vane suitable for variable circulating fan

Abstract

The invention provides a three-degree-of-freedom variable mounting angle inlet guide vane suitable for a variable circulating fan, which comprises 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 arranged on the main shaft, the first hollow auxiliary shaft is arranged on the first auxiliary blade, the second hollow auxiliary shaft is arranged on the second auxiliary blade, and the first auxiliary blade is arranged on the main shaft. The first hollow auxiliary shaft is sleeved with the second hollow auxiliary shaft, the main shaft is sleeved with the first hollow auxiliary shaft, a three-degree-of-freedom rotating mechanism is formed, and the main blade, the first auxiliary blade and the second auxiliary blade form the whole inlet guide blade. The main blade is used for adjusting the flowing direction in the whole flow channel, the second auxiliary blade is used for adjusting and controlling flow field adverse factors generated due to change of the bypass ratio of the variable cycle engine, and meanwhile the first auxiliary blade is used for adjusting and controlling various flow field adverse factors generated due to contact air inlet distortion. Therefore, the performance of the variable circulation fan under the action of different distortion forms under different variable circulation working conditions is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of aviation power devices, and in particular relates to a three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan. 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 adjust the radial characteristics of the flow field before and after the fan by controlling the guide vane profile separately, so as to meet the pre-swirl angle control required by the variable circulation fan under different distortion forms, ensure that the working efficiency, compression capacity, stability margin, etc. of the variable circulation fan when contacting distorted incoming flows of different strengths under different bypass ratio conditions can meet the working requirements of the entire compression system, and provide a three-degree-of-freedom variable installation angle inlet guide vane suitable for the variable circulation fan;

[0013] In order to achieve the above-mentioned object, the present invention adopts the following technical scheme: 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 arranged on the main shaft, the first hollow secondary shaft is arranged on the first secondary blade, the second hollow secondary shaft is arranged on the second secondary blade, and the second hollow secondary shaft is sleeved on the first hollow secondary shaft, and the first hollow secondary shaft is sleeved on the main shaft to form a three-degree-of-freedom rotation mechanism, and the main blade, the first secondary blade and the second secondary blade constitute the entire inlet guide vane.

[0015] Further, the blade tops of the first auxiliary blade and the second auxiliary blade are in contact with the blade bottom of the main blade respectively.

[0016] Furthermore, the height of the second auxiliary blade is the radial height covered by the flow separation vortex appearing in the fan operating under the influence of the total pressure swirl compound distortion at the blade tip.

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

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

[0019] 1) When the variable cycle fan contacts 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 rotate the main blade 5° to 10° counterclockwise;

[0020] 2) When the variable circulation fan is exposed to intake distortion distributed throughout the entire flow passage and with different degrees of distortion in the radial direction when operating at the design bypass ratio or high bypass ratio, keep the second auxiliary blade unchanged, rotate the first auxiliary blade 10° to 15° counterclockwise, and rotate the main blade 5° counterclockwise;

[0021] 3) When the variable circulation fan is operating under a small bypass ratio condition and the contact blade tip is distorted, keep the main blade unchanged, rotate the second auxiliary blade 5° to 10° counterclockwise, and rotate the first auxiliary blade 5° counterclockwise.

[0022] Beneficial effects: The present invention designs a variable geometry blade profile based on the traditional adjustable inlet guide vanes suitable for variable cycle turbofan engines, and constructs a three-degree-of-freedom variable installation angle inlet guide vane, which inherits the advantages of the traditional adjustable inlet guide vane and can ensure that the aircraft engine fan maintains a high performance under the influence of different intake distortions. At the same time, the three-degree-of-freedom rotation mechanism adjustment method makes the three-degree-of-freedom variable installation angle inlet guide vane can be used to improve the performance of the variable cycle fan subjected to different distortion forms under different variable cycle conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a schematic diagram of the structure of the inlet guide vane with adjustable mounting angle of three degrees of freedom.

[0024] Figure 2 It is a schematic diagram of the assembly of the inlet guide vane with adjustable mounting angle of three degrees of freedom.

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

[0026] Figure 4 It is a schematic diagram of blade adjustment when the intake air is distorted and in contact with the blade root under small bypass ratio conditions.

[0027] Figure 5 It is a schematic diagram of blade adjustment when the exhaust fan is exposed to intake distortion distributed throughout the entire flow passage and having different degrees of distortion in the radial direction when working at the designed bypass ratio or large bypass ratio conditions.

[0028] Figure 6 It is a schematic diagram of blade adjustment when working under small bypass ratio conditions and contacting blade tip distortion.

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

[0030] In the figure: 1, main blade, 2, first auxiliary blade, 3, second auxiliary blade, 4, main shaft, 5, first hollow auxiliary shaft, 6, second hollow auxiliary shaft. DETAILED DESCRIPTION

[0031] The present invention will be further explained below in conjunction with 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 arranged on the main shaft 4, the first hollow secondary shaft 5 is arranged on the first secondary blade 2, and the second hollow secondary shaft 6 is arranged on the second secondary blade 3. The blade tops of the first secondary blade 2 and the second secondary blade 3 are respectively in contact with the blade bottom of the main blade 1, and the second hollow secondary shaft 6 is sleeved on the first hollow secondary shaft 5, and the first hollow secondary shaft 5 is sleeved on the main shaft 4 to form 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 the action of different forms of distortion, the flow separation at the blade root of the variable circulation fan is relatively small, and the flow separation is gradually aggravated along the blade height direction due to the influence of distortion. Therefore, the second auxiliary blade 3 is arranged above the blade base of the blade 1. At the same time, during the change of the bypass ratio of the variable circulation fan, the flow at the tip of the blade is affected by the change of the diversion ratio and is mainly reflected in the direction of the blade tip. Therefore, the first auxiliary blade 2 is also arranged above the blade base of the blade 1. In order to make 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 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.

[0036] Determination of blade shape and installation position of auxiliary blades: The radial height of the auxiliary blades needs to be determined by the flow conditions at the fan blade tip. In this scheme, the height of the first auxiliary blade 2 and the second auxiliary blade 3 is the radial height covered by the flow separation vortex when the fan is working under the influence of the total pressure swirl compound distortion at the blade tip, and the distribution of the axial length of the auxiliary blades should refer to the flow separation conditions of the fan near the stall point when the fan is affected by the same distortion. Figure 7 It can be seen that the flow separation area caused by the distortion starts at about 40% of the axial length of the blade. Therefore, in this solution, the axial length of the second auxiliary blade 3 is 40% of the overall blade length, and the axial length of the first auxiliary blade 2 is 50% of the overall blade length.

[0037] like Figure 3 The figure shows a schematic diagram of the three-degree-of-freedom installation angle adjustable inlet guide vane and the fan stage meridian flow surface. The inlet adjustable guide vane is located in front of the fan stage. The variable cycle fan stage consists of a rotor and a stator. The variable cycle fan diverter and the mode selection valve (MSV) are located behind the fan stage.

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

[0039] When the variable cycle fan encounters intake distortion distributed at the blade root under small bypass ratio conditions, keep the second auxiliary blade unchanged and rotate the first auxiliary blade 5° counterclockwise to adapt to the problem of increased angle of attack caused by the small bypass ratio conditions. At the same time, rotate the main blade 5° to 10° counterclockwise to adjust the intake distortion in the area from the blade root to the middle of the blade.

[0040] When the variable circulation fan is operating at the design bypass ratio or large bypass ratio and is exposed to intake distortion distributed throughout the entire flow channel and with different degrees of distortion in the radial direction, the first auxiliary blade is kept unchanged, and the second auxiliary blade is rotated 10° to 15° counterclockwise to adapt to the larger angle of attack at the blade tip. At the same time, the main blade is rotated 5° counterclockwise to adapt to the distortion distributed in the middle and root of the blade. The design bypass ratio is a condition between the small bypass ratio and the large bypass ratio, which is the most efficient condition.

[0041] When the variable circulation fan operates under small bypass ratio conditions and the contact blade tip is distorted, keep the main blade unchanged, rotate the first auxiliary blade 5° to 10° counterclockwise, and rotate the second auxiliary blade 5° counterclockwise to adjust the flow field under this condition.

[0042] The present invention uses the main blade 1 to adjust the flow direction in the entire flow channel, and drives the second auxiliary blade 3 to rotate through the second hollow secondary shaft 6 to control the adverse flow field factors caused by the change of the bypass ratio of the variable cycle engine. At the same time, the first auxiliary blade 2 is driven to rotate by the first hollow secondary shaft 5 to control various adverse flow field factors caused by contact with intake distortion, thereby improving the performance of the variable cycle fan subjected to different distortion forms under different variable cycle conditions.

[0043] 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 three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan, characterized in that: include: 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); The main blade (1) is arranged on the main shaft (4), the first hollow secondary shaft (5) is arranged on the first secondary blade (2), the second hollow secondary shaft (6) is arranged on the second secondary blade (3), and the second hollow secondary shaft (6) is sleeved on the first hollow secondary shaft (5), and the first hollow secondary shaft (5) is sleeved on the main shaft (4), forming a three-degree-of-freedom rotation mechanism, and the main blade (1), the first secondary blade (2) and the second secondary blade (3) constitute the entire inlet guide vane.

2. The three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan according to claim 1, characterized in that: The blade tops of the first auxiliary blade (2) and the second auxiliary blade (3) are in contact with the blade bottom of the main blade (1) respectively.

3. The three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan according to claim 1, characterized in that: The height of the second auxiliary blade (3) is the radial height covered by the flow separation vortex when the fan is working under the influence of the total pressure swirl compound distortion at the blade tip.

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

5. The three-degree-of-freedom variable installation angle inlet guide vane suitable for a variable circulation fan according to claim 1, characterized in that: The adjustment method of the three-degree-of-freedom rotation mechanism is: 1) When the variable cycle fan contacts 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 rotate the main blade 5° to 10° counterclockwise; 2) When the variable circulation fan is exposed to intake distortion distributed throughout the entire flow passage and with different degrees of distortion in the radial direction when operating at the design bypass ratio or high bypass ratio, keep the second auxiliary blade unchanged, rotate the first auxiliary blade 10° to 15° counterclockwise, and rotate the main blade 5° counterclockwise; 3) When the variable circulation fan is operating under a small bypass ratio condition and the contact blade tip is distorted, keep the main blade unchanged, rotate the second auxiliary blade 5° to 10° counterclockwise, and rotate the first auxiliary blade 5° counterclockwise.

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