Variable camber blade for generating self-adaptive jet flow and design method of variable camber blade

Abstract

The invention discloses a variable camber blade for generating self-adaptive jet flow and a design method thereof, and belongs to the technical field of gas compressors, the variable camber blade comprises a front blade, a rear blade, an elastic film, a jet flow seam inlet, a jet flow seam outlet, a front blade tail edge, a rear blade front edge and a rear blade rotating axis; the jet flow seam inlet is located in the blade pressure face, and the jet flow seam outlet is located in the blade suction face. The elastic film, the front blade tail edge and the rear blade front edge form a jet flow channel with a variable geometrical shape; the elastic film deforms under the rotation of the rear blade and the change of the pressure difference between the two sides of the blade, so that the opening degree and the jet flow of the jet seam outlet are adjusted; on the premise of ensuring the simple structure of the variable camber blade, the variable camber blade can generate jet flow control capable of being adaptively adjusted, so that the suction surface flow separation of the blade in a large camber state is inhibited, and meanwhile, the flow loss of the blade in a small camber state is reduced.

Description

Technical Field

[0001] The invention relates to a variable-camber blade capable of adaptively adjusting jet flow and a design method thereof, and belongs to the technical field of compressors. Background Art

[0002] Advanced aircraft engines are developing towards high thrust-to-weight ratio, high efficiency and high reliability. Due to the large change in rotor angle of attack of high-load multi-stage axial compressors in aircraft engines under non-design conditions, especially at medium and low speeds, compressor surge problems are caused and engine stability margin is reduced. In order to ensure that the surge margin at medium and low speeds meets the requirements, multiple rows of variable stator vanes (VSV) are usually designed to adjust the blade load and compressor surge margin by changing the angle of attack of the rotor flow. For example, advanced civil engine compressors such as LEAP-X and GE9X are designed with five and six rows of adjustable stator vanes, respectively.

[0003] Adjustable stator blades are divided into two types: constant camber and variable camber. Constant camber blades adjust the outlet airflow angle by adjusting the installation angle. Changes in the installation angle cause changes in the angle of attack, which may result in greater performance losses. Variable camber blades are usually composed of variable camber guide vanes with gaps, such as Figure 1 As shown, the basic blade profile is separated from a certain point in the chord length, leaving a gap in the middle, the front section is fixed, and the rear section can rotate around a certain axis at a certain angle.

[0004] However, variable-camber blades also have two shortcomings, namely, leakage flow affects aerodynamic performance and the problem of airflow separation under large camber. Related studies have shown that due to the presence of a certain gap between the two sections of the variable-camber blade, airflow will leak from the blade basin to the back of the blade through the gap. The leakage of the gap airflow can cause the angle of attack of the airflow in the second half of the blade to increase, which has a significant negative impact on the aerodynamic performance of the variable-camber blade. The gap sealing design, such as the use of a rubber strip seal between the two sections of the blade, can inhibit the leakage of the gap airflow and significantly improve the aerodynamic performance of the blade. However, due to the repeated extrusion, deformation, and wear of the rubber strip caused by the rotation of the rear blade, the durability, safety, and reliability of this method are insufficient. In addition, after the rear blade rotates a large angle, the overall blade curvature composed of the front and rear blades becomes larger, resulting in an increase in the blade diffusion pressure, an increase in the risk of flow separation on the blade suction surface, and an impact on the aerodynamic performance of the blade.

[0005] Therefore, it is urgent to solve these two shortcomings of variable camber blades. One idea is to reasonably utilize the gap leakage gas to suppress the flow separation on the suction surface of the blade under large camber state, so as to achieve the effect of killing two birds with one stone. Summary of the invention

[0006] The purpose of the present invention is to overcome the deficiencies in the prior art and to provide a variable-curvature blade with adaptively adjustable jet flow and a design method thereof, so as to achieve that the variable-curvature blade can maintain high aerodynamic performance at different rear blade rotation angles, thereby improving the stability margin of the compressor and the engine.

[0007] To achieve the above object, the present invention is implemented by adopting the following technical solutions: In the first aspect, the present invention provides a variable-curvature blade for generating an adaptive jet, comprising: a front blade, a rear blade, an elastic membrane, a jet slot inlet, a jet slot outlet, a front blade trailing edge, a rear blade leading edge and a rear blade rotation axis; wherein the jet slot inlet is located on the pressure side of the blade, and the jet slot outlet is located on the suction side of the blade; the elastic membrane, the front blade trailing edge and the rear blade leading edge constitute a jet channel with a variable geometric shape; the rear blade can be rotated around the rear blade rotation axis to a set angle, and the elastic membrane is deformed by the rotation of the rear blade and the change of the pressure difference on both sides of the blade, thereby adjusting the opening of the jet slot outlet and the jet flow rate.

[0008] Furthermore, the elastic membrane has a width w , when the rear blade rotates at an angle i =0°, the elastic membrane is close to the suction surface of the rear blade and completely covers the jet slit outlet, and the rear blade generates a preload on the elastic membrane. F s0 .

[0009] Furthermore, the maximum rotation angle of the rear blade i max In the range of 10°~90°, the rear blade rotation angle i Satisfy: 0≤ i ≤ i max .

[0010] Furthermore, the angle at which the rear blade rotates around the rear blade rotation axis is i There is a critical angle i c When the rear blade rotates θ≤θ c When the overall curvature of the blade is small, the risk of flow separation is low, and the pressure difference on both sides of the elastic membrane is small. The elastic membrane is in a state of close contact with the rear blade, and the jet slot outlet is in a closed state with zero opening. At this time, no jet is generated at the jet slot outlet; when the rear blade rotates at an angle i > i cWhen the blade has a large overall curvature and a high risk of flow separation, the pressure difference on both sides of the elastic membrane is large, causing the elastic membrane to separate from the rear blade, and the jet slit outlet is in an open state with a certain opening. A jet is generated at the jet slit outlet, which can suppress the flow separation on the back side of the blade. The jet flow rate is then i increases with the increase of .

[0011] In a second aspect, the present invention provides a design method for a variable camber blade for generating an adaptive jet according to any one of the above items, comprising: On the basis of conventional variable camber blades, the geometric shapes of the front blade and the rear blade are designed, and the shapes of the front blade trailing edge and the rear blade leading edge are optimized to reduce the flow loss in the jet slot and ensure that there is no mechanical interference between the front blade and the rear blade when the rear blade rotates; Determine the rear blade rotation angle at which the variable camber blade just produces suction surface flow separation under the designed Mach number and angle of attack by experimental or numerical simulation methods. i As critical angle i c ; and set the maximum rotation angle of the rear blade i max ; Design elastic membrane width w , ensure that when the rear blade rotates i At 0°~ i c When within the range, the elastic membrane can completely cover the jet slit outlet; Determine the pressure coefficient by experimental or numerical simulation methods c , vertical displacement of elastic membrane contact state , vertical displacement of elastic membrane in natural state , elastic coefficient of elastic membrane k And preload .

[0012] Furthermore, the pressure coefficient is determined c The method is as follows: using experimental or numerical simulation methods, the formula Determine the pressure coefficient c ,in: is the average pressure difference on both sides of the elastic membrane.

[0013] Furthermore, the determination of the vertical displacement of the elastic membrane contact state The method is as follows: Set the maximum rotation angle of the rear blade i max The required jet gap width in the state is taken as the vertical displacement of the elastic membrane in the contact state reference value.

[0014] Furthermore, the vertical displacement of the elastic membrane in the natural state is determined The method is as follows: According to the formula Estimation of vertical displacement of elastic membrane in natural state .

[0015] Furthermore, the elastic coefficient of the elastic film is determined k The method is as follows: According to the formula , estimate the elastic constant of the elastic membrane k ,in: l is the span length of the blade.

[0016] Furthermore, the determination of the preload force The method is as follows: According to the formula , estimate the rear blade rotation angle θ= At 0, the supporting force of the blade on the elastic membrane is used as the preload force of the elastic membrane. .

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a variable-curvature blade and design method for adaptively adjusting jet flow, wherein the leakage flow between the front and rear blades is used as a jet for controlling the separation of the back side of the rear blade, and with the help of an elastic membrane, the jet flow can be adaptively adjusted as the overall curvature of the blade changes. When the overall curvature of the blade is small and there is no airflow separation, the jet opening of the variable-curvature blade is zero and no jet flow is generated, so as to reduce the flow loss in the jet gap; and when the overall curvature of the blade is large and there is airflow separation, the jet opening of the variable-curvature blade becomes larger and the jet flow increases, so as to suppress the flow separation on the suction surface of the blade and reduce the flow loss of the blade. This solution can improve the aerodynamic performance of the variable-curvature blade under different rear blade rotation angle conditions, and has the advantages of being relatively simple in structure, strong in adaptability, and strong in engineering practicality. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a schematic diagram of a conventional variable camber blade.

[0019] Figure 2 Schematic diagram of a variable camber blade for producing an adaptive jet (with no rotation of the rear blade).

[0020] Figure 3 It is a schematic diagram of a variable-camber blade for producing an adaptive jet (the rear blade is rotated by a certain angle).

[0021] Figure 4 A three-dimensional schematic diagram of a variable-camber blade for generating an adaptive jet.

[0022] Figure 5 The present invention is a schematic diagram showing the main parameters of a variable-camber blade and the stress state of an elastic membrane for generating an adaptive jet.

[0023] In the figure: 1, front blade; 2, rear blade; 3, elastic membrane; 4, jet slot inlet; 5, jet slot outlet; 6, front blade trailing edge; 7, rear blade leading edge; 8, rear blade rotation axis. DETAILED DESCRIPTION

[0024] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0025] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", and the like may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0026] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood by specific circumstances.

[0027] Embodiment 1, as Figure 3 As shown, this embodiment introduces a variable-curvature blade for generating an adaptive jet, and its structure includes: a front blade 1, a rear blade 2, an elastic membrane 3, a jet slot inlet 4, a jet slot outlet 5, a front blade trailing edge 6, a rear blade leading edge 7 and a rear blade rotation axis 8; wherein the jet slot inlet 4 is located on the pressure side of the blade, and the jet slot outlet 5 is located on the suction side of the blade; the elastic membrane 3, the front blade trailing edge 6 and the rear blade leading edge 7 constitute a jet channel with a variable geometric shape; the rear blade 2 can rotate around the rear blade rotation axis 8 by a certain angle, and the elastic membrane 3 is deformed under the rotation of the rear blade 2 and the change of the pressure difference on both sides of the blade, thereby adjusting the opening of the jet slot outlet 5 and the jet flow rate.

[0028] like Figure 4 As shown, the elastic membrane 3 has a width w When the rear blade 2 rotates i =0°, the elastic membrane 3 is in close contact with the suction surface of the rear blade 2 and completely covers the jet slot outlet 5, and the rear blade 2 generates a pre-tightening force on the elastic membrane 3 F s0 , at this time Figure 2 Status shown.

[0029] like Figure 5 As shown, the maximum rotation angle of the rear blade 2 i max In the range of 10° to 90°, the actual rotation angle of the rear blade 2 i Satisfy: 0≤ i ≤ i max .

[0030] The angle at which the rear blade 2 rotates around the rear blade rotation axis 8 i There is a critical angle i c .like Figure 2 As shown, when the actual turning angle θ≤θ c When the overall curvature of the blade is small, the risk of flow separation is low, and the pressure difference on both sides of the elastic membrane is small. The elastic membrane is in a state of being close to the rear blade 2, and the jet slot outlet 5 is in a closed state with zero opening. At this time, no jet is generated at the jet slot outlet 5; Figure 3 As shown, when the actual turning angle i > i c When the blade has a large overall curvature and a high risk of flow separation, the pressure difference on both sides of the elastic membrane 3 is large, causing the elastic membrane 3 to separate from the rear blade 2, and the jet slit outlet 5 is in an open state with a certain opening. At this time, a jet is generated at the jet slit outlet 5, which can suppress the flow separation on the back side of the blade. The jet flow rate is then i increases with the increase of .

[0031] like Figure 2-5 As shown, the variable camber blade for generating adaptive jet has the following design method features: Blade geometry design: Figure 1 , 2 As shown, on the basis of conventional variable-camber blades, the geometric shapes of the front blade 1 and the rear blade 2 are designed, and the shapes of the front blade trailing edge 6 and the rear blade leading edge 7 are optimized so that the flow loss in the jet slot formed by them is low, and when the rear blade 2 rotates, there is no mechanical interference between the front blade 1 and the rear blade 2.

[0032] Determine the critical angle i c and maximum rotation angle i max :like Figure 5 As shown, the rotation angle of the rear blade 2 when the variable camber blade just produces suction surface flow separation under the design Mach number and angle of attack is determined by experimental or numerical simulation methods. i As critical angle i c ; Determine the maximum rotation angle of the rear blade 2 according to the design requirements i max .

[0033] Design elastic membrane width w :like Figure 4 As shown, the width of the elastic membrane 3 is designed to be w , when the rear blade 2 rotates i At 0°~ i c Within this range, the elastic membrane 3 can completely cover the jet slot outlet 5.

[0034] Determine the pressure coefficient c 1 :like Figure 5 As shown, by using experimental or numerical simulation methods, the formula Determine the pressure coefficient c .in: is the average pressure difference on both sides of the elastic membrane 3.

[0035] Determine the vertical displacement of the elastic membrane contact state :like Figure 3 and Figure 5 As shown, the maximum rotation angle of the rear blade 2 i max The required jet gap width in the state is taken as the vertical displacement of the elastic membrane in the contact state reference value.

[0036] Determine the vertical displacement of the elastic membrane in its natural state :like Figure 5 As shown, according to the formula , estimate the vertical displacement of the elastic membrane in its natural state .

[0037] Determine the elastic constant of the elastic membrane k :like Figure 5 As shown, according to the formula , estimate the elastic constant of the elastic membrane k .in: l is the span length of the blade.

[0038] Determine the preload :like Figure 2, Figure 5 As shown, according to the formula , estimate the rotation angle of rear blade 2 θ= At 0, the supporting force of the rear blade 2 on the elastic membrane 3, i.e. the elastic membrane preload .

[0039] The contents involved in the above embodiment are described below in conjunction with a preferred embodiment.

[0040] like Figure 2~5 As shown in the figure, for a typical large expansion degree low-speed compressor stator blade, the rear blade angle i = 0, the total chord length of the front and rear blades is 60 mm, the maximum thickness of the blade is 6 mm, and the span length of the blade is l =100 mm, the critical rotation angle of the blade under a certain working condition i c =20°, designed maximum rotation angle i max =45°. Under this condition, the pressure coefficient c ≈600 Pa / rad, select the elastic membrane width w =5 mm, vertical displacement of the elastic membrane in contact state =1 mm. According to the above formula, it can be calculated that the vertical displacement of the elastic membrane in the natural state ≈2 mm, elastic modulus of elastic membrane k ≈50 N / m, rear blade rotation angle θ= Elastic membrane preload at 0 ≈0.04 N. Thus, when the rear blade turns i When the rear blade angle is ≤20°, no jet is generated; θ> When the rear blade turns at 20°, a jet is generated; i =45°, the jet slot outlet width reaches the designed maximum value of 1 mm.

[0041] The working principle of a variable camber blade with adaptive jet flow is as follows: the jet slot inlet 4 of the device is located on the pressure side of the blade, the jet slot outlet 5 is located on the suction side of the blade, and an elastic membrane 3 is installed at the trailing edge 6 of the front blade. The rear blade 2 rotates around the rear blade rotation axis 8 at different angles. i When the pressure difference between the pressure surface and the suction surface of the blade is different, the pressure difference on both sides of the elastic membrane 3 is different, resulting in different degrees of deformation. The deformation of the elastic membrane 3 cooperates with the rotation of the rear blade 2, resulting in a corresponding change in the opening of the jet port 5. Specifically, when the rear blade 2 rotates iWhen the angle is smaller, the overall curvature of the blade is small and the risk of flow separation is low. At this time, the pressure difference on both sides of the elastic membrane is small, the elastic membrane is in a state of close contact with the rear blade 2, and the jet slot outlet 5 is in a closed state with zero opening. At this time, no jet is generated at the jet slot outlet 5; and when the rear blade 2 turns i When the blade is larger, the overall curvature of the blade is large and the risk of flow separation is high. At this time, the pressure difference on both sides of the elastic membrane 3 is large, so that the elastic membrane 3 is separated from the rear blade 2, and the jet slot outlet 5 is in an open state with a certain opening. At this time, a jet is generated at the jet slot outlet 5, which can suppress the flow separation on the back side of the blade. The jet flow rate is then adjusted by the rotation angle of the blade 2. i Therefore, this solution can realize the adaptive adjustment of the jet flow rate associated with the overall curvature of the blade and the risk of flow separation, and reduce the flow loss caused by leakage and flow separation under various working conditions.

[0042] The innovation of the present invention lies in that it adopts a clever way to solve the two problems of variable camber blades, namely, the leakage flow affects the aerodynamic performance and the airflow is easy to separate under large camber. That is, the leakage flow is used as a jet to control the airflow separation, and the elastic membrane shape is reasonably designed to be used as a valve to control the leakage flow flow, thereby achieving the matching of the overall camber of the blade and the jet flow, improving the aerodynamic performance of the blade under variable working conditions, and alleviating the two problems of variable camber blades.

[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 technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A variable camber blade for generating an adaptive jet, characterized in that: include: A front blade (1), a rear blade (2), an elastic membrane (3), a jet slot inlet (4), a jet slot outlet (5), a front blade trailing edge (6), a rear blade leading edge (7), and a rear blade rotation axis (8); wherein the jet slot inlet (4) is located on the pressure surface of the blade, and the jet slot outlet (5) is located on the suction surface of the blade; the elastic membrane (3), the front blade trailing edge (6), and the rear blade leading edge (7) constitute a jet channel with a variable geometric shape; the rear blade (2) can rotate around the rear blade rotation axis (8) to a set angle, and the elastic membrane (3) deforms when the rear blade (2) rotates and the pressure difference on both sides of the blade changes, thereby adjusting the opening of the jet slot outlet (5) and the jet flow rate.

2. The variable camber blade for generating an adaptive jet according to claim 1, characterized in that: The elastic membrane (3) has a width w , when the rear blade (2) rotates by an angle θ =0°, the elastic membrane (3) is in close contact with the suction surface of the rear blade (2) and completely covers the jet slot outlet (5), and the rear blade (2) generates a pre-tightening force on the elastic membrane (3). F s0 .

3. The variable camber blade for generating an adaptive jet according to claim 1, characterized in that: The maximum rotation angle of the rear blade (2) θ max In the range of 10° to 90°, the rotation angle of the rear blade (2) θ Satisfy: 0≤ θ ≤ θ max .

4. The variable camber blade for generating an adaptive jet according to claim 1, characterized in that: The rear blade (2) rotates at an angle θ There is a critical angle θ c ,when θ≤θ c When , the pressure difference on both sides of the elastic membrane is small, the elastic membrane is in a state of being closely attached to the rear blade (2), and the jet slit outlet (5) is in a closed state. At this time, no jet is generated at the jet slit outlet (5); when θ > θ c When the pressure difference between the two sides of the elastic membrane (3) is large, the elastic membrane (3) is separated from the rear blade (2), the jet slit outlet (5) is opened, and a jet is generated at the jet slit outlet (5). The jet flow rate generated by the jet slit outlet (5) changes with the θ increases with the increase of .

5. A method for designing a variable camber blade for generating an adaptive jet according to any one of claims 1 to 4, characterized in that: include: On the basis of conventional variable camber blades, the geometric shapes of the front blade (1) and the rear blade (2) are designed, and the shapes of the front blade trailing edge (6) and the rear blade leading edge (7) are optimized to reduce the flow loss in the jet gap and ensure that the front blade (1) and the rear blade (2) do not mechanically interfere with each other when the rear blade (2) rotates; Determine by experimental or numerical simulation methods the rotation angle of the rear blade (2) at which the variable camber blade just produces suction side flow separation under the designed Mach number and angle of attack. θ As critical angle θ c ; and set the maximum rotation angle of the rear blade (2) θ max ; Design elastic membrane width w , ensure that when the rear blade rotates θ At 0°~ θ c When within the range, the elastic membrane can completely cover the jet slit outlet; Determine the pressure coefficient by experimental or numerical simulation methods c , vertical displacement of elastic membrane contact state , vertical displacement of elastic membrane in natural state , elastic coefficient of elastic membrane k And preload .

6. The design method of a variable camber blade for generating an adaptive jet according to claim 5, characterized in that: Determining the pressure coefficient c The method is as follows: using experimental or numerical simulation methods, the formula Determine the pressure coefficient c ,in: is the average pressure difference on both sides of the elastic membrane (3).

7. The design method of a variable camber blade for generating an adaptive jet according to claim 6, characterized in that: Determining the vertical displacement of the elastic membrane contact state The method is as follows: adjust the maximum rotation angle of the rear blade (2) θ max The required jet gap width in the state is taken as the vertical displacement of the elastic membrane in the contact state reference value.

8. The design method of a variable camber blade for generating an adaptive jet according to claim 7, characterized in that: Determining the vertical displacement of the elastic membrane in the natural state The method is as follows: According to the formula Estimation of vertical displacement of elastic membrane in natural state .

9. The design method of a variable camber blade for generating an adaptive jet according to claim 8, characterized in that: The elastic coefficient of the elastic film is determined k The method is as follows: According to the formula , estimate the elastic constant of the elastic membrane k ,in: l is the span length of the blade.

10. The design method of a variable camber blade for generating an adaptive jet according to claim 9, characterized in that: Determining the preload The method is as follows: According to the formula , estimate the rotation angle of the rear blade (2) θ = At 0, the supporting force of the blade (2) on the elastic membrane (3) serves as the elastic membrane preload force. .

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