Two-degree-of-freedom three-dimensional aeroelasticity measurement device

Abstract

A two-degree-of-freedom three-dimensional aeroelasticity measurement device comprises: a four-component balance, a blade flapping mechanism, a blade pitching mechanism and an end plate structure, wherein: the four-component balance is arranged at the bottom end of the interior of a wind tunnel test section and is connected to the blade flapping mechanism outside the wind tunnel test section; the blade flapping mechanism is located between the four-component balance and the blade pitching mechanism to achieve left and right tilting operation; the blade pitching mechanism is arranged below the blade flapping mechanism to achieve pitching operation; and the end plate structure is arranged at the top of the wind tunnel test section to suppress blade tip vortices. The present invention can achieve high-precision measurement of the nonlinear aerodynamic load, pitch angle change response and flapping angle change response of a forced oscillating blade in a pitch-flapping two-degree-of-freedom three-dimensional aeroelastic system. The present invention has a convenient spring replacement function, can flexibly change the stiffness coefficient in the flapping direction, and can perform parametric simulation of special resonance phenomena such as combined resonance and sub-resonance.

Description

Technical Field

[0001] The present invention relates to a wind tunnel test technology in the field of helicopter blade aeroelastic coupling dynamics, in particular to a two-degree-of-freedom three-dimensional aeroelasticity measuring device. Background Art

[0002] When a helicopter flies forward, the flow field around the blades continuously changes, and coupled with pitch variation, flapping, and flexible deformation, forms a complex transient nonlinear aeroelastic system. Traditional two-dimensional simplified models can no longer meet current research needs. It is necessary to accurately measure the three-dimensional aeroelastic response of the blades to optimize rotor design and improve performance. Figure 1 As shown in (a), the motion of the blade in all directions superimposed on the flexible deformation is a composite vibration, which can be divided into torsion around the x-axis, flapping around the y-axis, and shimmying vibration around the z-axis. Shimmying vibration is generally ignored in research. Figure 1 As shown in (b), the traditional two-dimensional simplified model simplifies torsional vibration and flapping vibration into the pitching motion and floating motion of the airfoil in the yz plane, respectively. The three-dimensional simplified model, which is more in line with engineering practice, simplifies flapping vibration into the flapping motion of the rigid blade in the xz plane. In addition, the three-dimensional simplified model sets a pitch torsion spring at the 1 / 4 chord line of the blade root airfoil (yz plane) and a flapping torsion spring in the xz plane perpendicular to the airfoil to simulate the torsional stiffness of the blade. and bending stiffness . Actual pitch angle of the propeller blade The externally given pitch cycle driving angle Elastic deformation angle caused by pitch torsion spring Waving Horn It is the elastic deformation angle of the flapping torsion spring caused by aerodynamic load, that is, the angle between the blade axis and the balance axis of the flapping torsion spring. Summary of the Invention

[0003] To address the shortcomings of existing technologies, such as the inability to simulate three-dimensional aeroelastic responses, the inability to flexibly change the stiffness coefficients of individual degrees of freedom, and the inability to perform parametric aeroelastic simulation, this paper proposes a two-degree-of-freedom, three-dimensional aeroelastic measurement device. This device enables high-precision measurement of the nonlinear aerodynamic loads, pitch angle response, and flapping angle response of a forced oscillating blade in a two-degree-of-freedom, three-dimensional aeroelastic system. This device features convenient spring replacement, flexible variation of the stiffness coefficients in the flapping direction, and parametric simulation of special resonance phenomena such as combined resonance and secondary resonance.

[0004] The present invention is achieved through the following technical solutions:

[0005] The present invention relates to a two-degree-of-freedom three-dimensional aeroelasticity measuring device, comprising: a four-component balance, a blade flapping mechanism, a blade pitching mechanism and an end plate structure, wherein: the four-component balance is arranged at the bottom end of a wind tunnel test section and is connected to the blade flapping mechanism outside the wind tunnel test section; the blade flapping mechanism is located between the four-component balance and the blade pitching mechanism to realize left and right tilting operation; the blade pitching mechanism is arranged below the blade flapping mechanism to realize pitching operation; and the end plate structure is arranged at the upper part of the wind tunnel test section to suppress blade tip vortex.

[0006] The bottom of the four-component balance is fixed to the blade flapping mechanism, and the upper part is used to install the blade model, which can measure the aerodynamic force and aerodynamic torque exerted on the blade model with high precision.

[0007] The blade swinging mechanism comprises a swinging arm at the upper part and a swinging seat at the lower part, wherein the swinging seat and the swinging arm are elastically connected by a pair of swinging springs or rigidly connected by bolts.

[0008] The two ends of the swing spring are respectively fixed to the swing seat and the swing arm, and the swing shaft is arranged through the middle of the swing arm and the swing seat to form a seesaw structure; a swing angle sensor for measuring the angle change of the swing angle is provided on one side of the swing shaft.

[0009] The blade pitch mechanism includes: a pitch shaft, a pitch support bearing seat and a pitch angle sensor located at the upper part, and a horizontal connecting block group and a pitch drive motor composed of a left connecting block and a right connecting block located at the lower part, wherein: the top end of the pitch shaft is fixedly connected to the blade flapping mechanism and is passed through the pitch support bearing seat through a bearing, the pitch support bearing seat is fixed to the square box shell, and a pitch angle sensor for measuring the angular change of the pitch angle is provided inside; the left connecting block is fixedly connected to the pitch shaft, the right connecting block is fixedly connected to the output shaft of the pitch drive motor, and the left connecting block and the right connecting block are elastically connected by a pitch spring or rigidly connected by bolts.

[0010] The end plate structure is fixed to the left and right side walls of the wind tunnel test section through adapters and L-shaped plates on both sides; a support member and an end plate are provided in the middle, the upper end of the support member is fixed to the upper wall of the wind tunnel test section, and the end plate is fixedly connected to the lower end of the support member.

[0011] Technical Effects

[0012] The present invention utilizes a four-component balance, a pitch structure, and a flapping structure to achieve high-precision measurement of the nonlinear aerodynamic loads, pitch angle response, and flapping angle response of a forced oscillating blade in a three-dimensional aeroelastic system with two degrees of freedom: pitch and flapping. The present invention features convenient spring replacement, enabling flexible changes in the flapping direction's stiffness coefficient and enabling parametric simulation of special resonance phenomena such as combined resonance and subresonance. Furthermore, through the convenient assembly and disassembly capabilities of the end plate structure, the present invention provides an effective means for intuitively evaluating the impact of tip vortices on three-dimensional aeroelastic systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the principle of three-dimensional forced oscillation blade;

[0014] In the figure: (a) is a schematic diagram of a three-dimensional blade oscillation; (b) is a schematic diagram of a three-dimensional simplified model of a forced oscillating blade aeroelastic system;

[0015] Figure 2 It is a schematic diagram of the overall structure of the present invention;

[0016] In the figure: (a) is a schematic diagram of the whole state without end plates; (b) is a schematic diagram of the whole state with end plates;

[0017] Figure 3 is a schematic diagram of the blade model;

[0018] Figure 4 It is a schematic diagram of a four-component balance;

[0019] Figure 5 This is a schematic diagram of the blade flapping mechanism;

[0020] Figure 6 Schematic diagram of the blade pitch mechanism;

[0021] Figure 7 is a schematic diagram of the end plate structure;

[0022] Figure 8 This is a schematic diagram of the finite element analysis of the sensitivity of a four-component balance;

[0023] Figure 9 To simplify the model, the finite element analysis diagram of the waving motion is shown;

[0024] Figure 10 Schematic diagram of numerical simulation of blade flow field;

[0025] In the figure: (a) is the vortex cloud diagram in the state without end plates; (b) is the vortex cloud diagram in the state with end plates; (c) is the velocity vector diagram in the state without end plates; (d) is the velocity vector diagram in the state with end plates;

[0026] In the figure: 1 wind tunnel test section, 2 blade model, 3 blade flapping mechanism, 4 blade pitching mechanism, 5 end plate structure, 201 left cover plate, 202 blade tip cap, 203 right cover plate, 204 four-component balance, 301 flapping angle sensor, 302 flapping seat, 303 flapping arm, 304 flapping spring, 305 flapping shaft, 306 bearing cover, 401 pitching shaft, 402 pitching angle sensor, 403 pitching support bearing seat, 404 left connecting block, 405 right connecting block, 406 pitching spring, 407 pitching drive motor, 408 square box shell, 501 adapter, 502 L-shaped plate, 503 support, 504 end plate. DETAILED DESCRIPTION

[0027] like Figure 2 As shown, this embodiment relates to a two-degree-of-freedom three-dimensional aeroelastic measurement device, including: a wind tunnel test section 1, a blade model 2, a blade flapping mechanism 3 and a blade pitching mechanism 4, wherein: the blade model 2 is arranged at the bottom end of the wind tunnel test section 1 and is connected to the blade flapping mechanism 3 located outside the wind tunnel test section 1, the blade flapping mechanism 3 is located between the blade model 2 and the blade pitching mechanism 4, the blade pitching mechanism 4 is arranged below the blade flapping mechanism 3, and the end plate structure 5 is arranged on the upper part of the wind tunnel test section 1.

[0028] like Figure 3 As shown, the blade model 2 includes: a left cover plate 201, a blade tip cap 202, a right cover plate 203 and a four-component balance 204, wherein: the left cover plate 201 and the right cover plate 203 are relatively horizontally combined, the blade tip cap 202 is arranged on the top of the left cover plate 201 and the right cover plate 203, and the blade tip cap 202 is divided into a flat cap and a round cap for replacement, and the upper part of the four-component balance 204 is arranged between the bottom of the left cover plate 201 and the right cover plate 203.

[0029] The left cover plate 201 and the right cover plate 203 constitute a NACA 0012 airfoil as a reference airfoil, with an overall span of 0.6 m, a chord length of 0.3 m, and a top distance of 0.746 m from the upper wall of the wind tunnel test section 1, ensuring good three-dimensional characteristics of the blade tip flow field and little influence from the wall.

[0030] like Figure 4 As shown, the four-component balance 204 generally adopts a rod-type structure, a measuring element is set in the middle, a 12-column beam form, and a π-type structure is adopted at the top, which is fixed to the root of the blade model 2.

[0031] like Figure 5As shown, the blade flapping mechanism 3 comprises a flapping angle sensor 301, a flapping base 302, a flapping arm 303, a flapping spring 304, a flapping shaft 305, and a bearing cap 306. The middle portion of the flapping arm 303 is rotatably mounted on the flapping base 302 via the flapping shaft 305, forming a seesaw-like structure. The flapping angle sensor 301, which measures the flapping angle, is fixed to the bearing cap 306 at one end of the flapping shaft 305. A pair of flapping springs 304 are positioned between the flapping base 302 and the flapping arm 303, with their ends fixed to the flapping base 302 and the flapping arm 303, respectively, simulating the flapping torsion spring in a three-dimensional aeroelastic system.

[0032] The swing arm 303 and the swing seat 302 are selectively rigidly connected by bolts, thereby locking the swing degree of freedom and turning the device into a single-degree-of-freedom pitch oscillation system.

[0033] like Figure 6 As shown, the blade pitch mechanism 4 includes: a pitch shaft 401, a pitch angle sensor 402, a pitch support bearing seat 403, a horizontal connecting block group, a pitch drive motor 407 and a square box shell 408, which are arranged in sequence from top to bottom, wherein: the top of the pitch shaft 401 is fixedly connected to the blade swinging mechanism 3 and is passed through the pitch support bearing seat 403 through a bearing, transmitting the pitch motion to the blade swinging mechanism 3 and the blade model 2; the pitch support bearing seat 403 is fixedly set on the upper part of the square box shell 408, and is provided with a pitch angle sensor 402 for measuring the pitch angle change; the horizontal connecting block group is set between the pitch shaft 401 and the pitch drive motor 407; the pitch drive motor 407 is fixedly set at the lower part of the square box shell 408.

[0034] The horizontal connecting block group includes: a left connecting block 404, a right connecting block 405 and a pitch spring 406, wherein: the pitch axis 401 is fixedly connected to the left connecting block 404, the output shaft of the pitch drive motor 407 is fixedly connected to the right connecting block 405, and four pitch springs 406 are arranged between the left connecting block 404 and the right connecting block 405 to achieve an elastic connection between the pitch axis 401 and the output shaft of the pitch drive motor 407. The pitch spring 406 simulates the pitch torsion spring in the three-dimensional aeroelastic system.

[0035] The left connecting block 404 and the right connecting block 405 are selectively rigidly connected by bolts, and the pitch freedom movement of the device is converted into rigid oscillation.

[0036] like Figure 7As shown, the end plate structure 5 includes: an adapter 501, an L-shaped plate 502, a support member 503 and an end plate 504, wherein: the end plate 504 is fixedly connected to the left and right side walls of the wind tunnel test section 1 through the adapter 501 and the L-shaped plate 502, thereby improving the overall stiffness of the end plate structure 5; the upper end of the support member 503 is fixed to the top of the wind tunnel test section 1, and the end plate 504 is fixedly connected to the lower end of the support member 503, and the distance between the two support members 503 is 0.8m, which can reduce the influence of the wake of the support member 503 on the flow field of the blade model 2; the middle section of the end plate 504 is made of organic glass, and the left and right sections are made of aluminum alloy, which are fixedly connected by the support member 503 respectively, while ensuring stiffness, it is convenient for laser irradiation and camera shooting of the PIV experiment; and the lower surface of the end plate 504 is only 0.002m away from the top of the blade model 2 equipped with the flat cap, which can eliminate the influence of the tip vortex.

[0037] Preferably, before the end plate structure 5 is installed, the blade tip cap 202 of the blade model 2 is assembled as a flat cap. After the end plate structure 5 is disassembled, the blade tip cap 202 of the blade model 2 is assembled as a round cap, forming a smooth transition between the upper and lower airfoils.

[0038] like Figure 8 As shown in Table 1, the finite element analysis of the four-component balance 204 was performed under the extreme load conditions of lift of 1176.7 N, flapping moment of 353 Nm, pitching moment of 70.65 Nm, and drag of 235.32 N. Figure 8 (a) is lift analysis, Figure 8 (b) is the flapping moment analysis, Figure 8 (c) is the pitching moment analysis, Figure 8 (d) is resistance analysis, and the obtained data are summarized in Figure 9 From the sensitivity calculation table of the four-component balance, we can see that the sensitivity (micro-strain) of the four-component balance 204 in the lift, flapping moment, pitching moment and drag directions are 240, 700, 760 and 112 respectively, and the overall accuracy reaches 0.2‰.

[0039] Table 1 Four-component balance sensitivity calculation table

[0040] Quantity lift Swinging torque Pitching moment resistance Remark Load (N, Nm) 1176.7 353 70.65 235.32 Theoretically calculated maximum strain εmax (με) 291 718 443 130 Material mechanics calculations Patch area bridge strain εave (με) 240 700 760 105 Finite element calculation

[0041] like Figure 9 As shown in Table 2, under the same limit load condition, the finite element analysis was performed on the blade model 2 equipped with the simplified blade flapping mechanism 3. Figure 9 To simplify the finite element analysis of the model's flapping motion, Table 2 is a comparison table of the flapping angle responses of three different flapping springs 304. It can be seen that replacing different flapping springs 304 can change the stiffness coefficient of the device's flapping direction and produce different flapping angle responses under the same load.

[0042] Table 2 Comparison of flapping angle responses under different flapping springs

[0043] Waving Spring Serial Number Stiffness coefficient in the swing direction (N / m) Corresponding circular frequency (Hz) Spring displacement (mm) Flapping angle response 1 38580 42 20 7.7° 2 95999 65 8 3° 3 155344 84 5 2°

[0044] like Figure 10 As shown, when the wind speed is 48.7 m / s and the Reynolds number is 1×10 6 , under the working condition of pitch angle of 30 degrees, the flow field of blade model 2 in the state without end plate 504 and with end plate 504 is numerically simulated. Figure 10 (a) Figure 10 (c) The vorticity cloud diagram and velocity vector diagram are respectively shown in the state without end plate 504. It can be seen that the tip of blade model 2 has obvious tip vortex, and the maximum x-direction vorticity is 6100 s -1 ; Figure 9 (2) Figure 10 (d) The vorticity cloud diagram and velocity vector diagram are respectively shown in the state with the end plate 504. It can be seen that there is basically no rolled-up vortex system at the tip of blade model 2. Most of the tip vortex is suppressed by the end plate 504, and the maximum x-direction vorticity is only 2000 s -1 .

[0045] Compared with the existing technology, the present device can realize high-precision measurement of the nonlinear aerodynamic loads (lift, drag, flapping moment, pitching moment) of the forced oscillating blade in the pitch and flapping two-degree-of-freedom three-dimensional aeroelastic system through the four-component balance 204 in the blade model 2; the present device can realize the flapping motion of the blade model 2 under different flapping stiffness coefficients through the blade flapping mechanism 3, and can also change the flapping stiffness coefficient of the device by replacing the flapping spring 304, and realize high-precision measurement of the response to the flapping angle change through the flapping angle sensor 301, so as to achieve the purpose of parametric simulation of the aeroelasticity of the blade flapping direction; in addition, the present device can also suppress the blade tip vortex by installing the end plate structure 5, and compare with the working condition without the end plate structure 5, which can clearly reveal the influence of the blade tip vortex on the three-dimensional aeroelastic response and flow field of the blade.

[0046] The above-mentioned specific implementation can be partially adjusted in different ways by those skilled in the art without departing from the principles and purpose of the present invention. The scope of protection of the present invention shall be based on the claims and shall not be limited by the above-mentioned specific implementation. All implementation schemes within its scope shall be subject to the constraints of the present invention.

Claims

1. A two-degree-of-freedom three-dimensional aeroelasticity measuring device, characterized in that: include: a four-component balance, a blade flapping mechanism, a blade pitching mechanism, and an end plate structure, wherein: the four-component balance is arranged at the bottom end of the wind tunnel test section and is connected to the blade flapping mechanism outside the wind tunnel test section; the blade flapping mechanism is located between the four-component balance and the blade pitching mechanism to realize left and right tilting operation; the blade pitching mechanism is arranged below the blade flapping mechanism to realize pitching operation; the end plate structure is arranged at the upper part of the wind tunnel test section to suppress the blade tip vortex; the upper part of the four-component balance is used to install the blade model; The blade swinging mechanism comprises: a swinging arm located at the upper part and a swinging seat located at the lower part, wherein: the swinging seat and the swinging arm are elastically connected by a pair of swinging springs or rigidly connected by bolts; The blade pitch mechanism includes: a pitch shaft, a pitch support bearing seat and a pitch angle sensor located at the upper part, and a horizontal connecting block group consisting of a left connecting block and a right connecting block located at the lower part, and a pitch drive motor; The end plate structure is fixed to the left and right side walls of the wind tunnel test section through adapters and L-shaped plates on both sides; a support member and an end plate are provided in the middle, the upper end of the support member is fixed to the upper wall of the wind tunnel test section, and the end plate is fixedly connected to the lower end of the support member.

2. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 1, characterized in that: The bottom of the four-component balance is fixed to the blade flapping mechanism, and can measure the aerodynamic force and aerodynamic moment exerted on the blade model with high precision.

3. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 1, characterized in that: The two ends of the swing spring are respectively fixed to the swing seat and the swing arm, and the swing shaft is arranged through the middle of the swing arm and the swing seat to form a seesaw structure; a swing angle sensor for measuring the angle change of the swing angle is provided on one side of the swing shaft.

4. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 1, characterized in that: The top end of the pitch shaft is fixedly connected to the blade flapping mechanism and is passed through the pitch support bearing seat through a bearing. The pitch support bearing seat is fixed to the square box shell and is provided with a pitch angle sensor for measuring the angular change of the pitch angle; the left connecting block is fixedly connected to the pitch shaft, and the right connecting block is fixedly connected to the output shaft of the pitch drive motor. The left connecting block and the right connecting block are elastically connected by a pitch spring or rigidly connected by bolts.

5. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 1, characterized in that: The blade model includes: a left cover plate, a blade tip cap, a right cover plate and a four-component balance, wherein: the left cover plate and the right cover plate are relatively horizontally combined, the blade tip cap is arranged on the top of the left cover plate and the right cover plate, and the blade tip cap is divided into a flat cap and a round cap for replacement, and the upper part of the four-component balance is arranged between the bottom of the left cover plate and the right cover plate.

6. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 5, characterized in that: The left cover plate and the right cover plate constitute a NACA 0012 airfoil as a reference airfoil, with an overall span of 0.6 m, a chord length of 0.3 m, and a top distance of 0.746 m from the upper wall of the wind tunnel test section.

7. The two-degree-of-freedom three-dimensional aeroelasticity measuring device according to claim 1 or 2, characterized in that: The four-component balance adopts a rod-type structure, a measuring element is arranged in the middle, a 12-column beam form is adopted, and a π-type structure is adopted at the top.

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