Precession simulation device for spiral flutter wind tunnel test

Abstract

The invention belongs to the technical field of wind tunnel tests, and particularly relates to a precession simulation device for a spiral flutter wind tunnel test. According to the invention, the design problem of the rotor craft spiral flutter wind tunnel test device is solved, and the key influence parameters and influence rules of the spiral flutter of the aircraft are researched by designing the precession motion simulation device of the rotor craft. Rotation of the rotor wings can be realized in the wind tunnel, and the rotating speed of the rotor wings is adjusted through the motor. Meanwhile, pitching and deflection modal decoupling of the rotating shaft of the rotating system is achieved, and pitching and deflection modal frequencies are independently adjustable; meanwhile, the axis of the pitch axis and the axis of the yaw axis coincide, so that pitching and yaw freedom degree coupling precession motion can be achieved under the effect of gyroscopic moment. Meanwhile, nacelle rotating mass rotational inertia, nacelle weight and mass center position adjustment can be achieved; and finally, the rotating speed of the rotating mass such as the rotor wing and the propeller hub can be adjusted through a speed adjusting motor, matching of the rotating speed and the incoming flow speed is guaranteed, and the spiral flutter state is achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wind tunnel tests, and particularly relates to a precession simulation device for spiral flutter wind tunnel tests. Background Art

[0002] Spiral flutter (English name: whirl flutter), also known as rotary flutter, is an aeroelastic divergence phenomenon commonly encountered in aircraft powered by propellers such as tiltrotor aircraft and fixed-wing propeller aircraft. It involves the interaction of aerodynamic forces, elastic restoring forces, and inertial forces on the flexibly mounted engine nacelle and rotor system. Under specific rotational speed and flight speed conditions, the engine nacelle undergoes pitch and yaw coupled precession, accompanied by aeroelastic divergence phenomena such as wing and rotor bending and torsion. This phenomenon can cause the aircraft structure to become unstable and seriously threaten flight safety. Currently, it is difficult to accurately predict the spiral flutter phenomenon through theoretical modeling and simulation analysis. Wind tunnel tests are an important technical means for studying spiral flutter problems. There is a lack of design for spiral flutter wind tunnel test model devices in China.

[0003] Patent CN202411438538 discloses a nacelle wind tunnel test model and simulation verification method for rotary flutter analysis, but does not involve the adjustment of parameters such as nacelle support stiffness, weight parameters, and rotational speed. Patent CN202410487340 discloses a method and device for measuring the rotary flutter boundary of a tiltrotor aircraft, but does not involve the rotary flutter wind tunnel test model to be tested. Patent CN202411434304 discloses a method for calculating the rotary flutter damping of a tiltrotor aircraft based on CAMRAD software, and does not involve the wind tunnel test model and test method for rotary flutter. Patent CN202410092465 discloses a ground comprehensive test device and method for a rotor nacelle, and does not involve wind tunnel tests. Patent CN202311507788 discloses a method and test system for a scaled model rotary flutter wind tunnel test of a tiltrotor aircraft, and does not involve structural details and the design of parameter adjustment devices such as stiffness and mass. Patent CN202311507788 discloses a rotor blade configuration design for suppressing rotary flutter of a tiltrotor aircraft, which only relates to the blades and does not involve the design of key components for rotary flutter such as nacelles and wings.

[0004] There is a lack of a spiral flutter wind tunnel test simulation device, a simulation device for the precession motion during the occurrence of spiral flutter, a device for decoupling the pitch and yaw motions of the nacelle and independently adjusting the pitch and yaw stiffness, and a spiral flutter wind tunnel test model device for adjusting the nacelle weight and center of gravity parameters. Summary of the Invention

[0005] The particularity of spiral flutter lies in that the precession of the rotating body (also known as precession, English name: Precession) is caused by the gyroscopic effect (also known as the gyroscopic effect). Under the action of the gyroscopic moment generated by the gyroscopic effect, the out-of-plane motion of the rotating body will cause a moment perpendicular to the direction of this motion, thereby coupling the pitch and yaw modes to form a gyro mode, also known as precession. Therefore, the wind tunnel test device for spiral flutter needs to be able to adjust the stiffness of the pitch and yaw degrees of freedom, and at the same time be able to couple the pitch and yaw to form a gyro mode.

[0006] Taking Figure 7 as an example, the rotor system includes a rotating shaft and rotating blades. When not rotating, its motion can be represented by two degrees of freedom, namely pitch θ about the y-axis and yaw ψ about the z-axis, and the support stiffness coefficients of the two degrees of freedom are K θ , K ψ , where the stiffness coefficients come from the wing, engine nacelle pylon, etc. In the case where the propeller is stationary and the air flow velocity is zero, the nacelle-propeller system contains two independent vibration modes, where the modal frequency about the y-axis is ω θ , and the modal frequency about the z-axis is ω ψ .

[0007] When considering the propeller rotation speed of Ω, the gyroscopic effect causes the two independent modes to couple into a whirl motion, as shown in Figure 8. This is because the angular velocity ω ψ about the z-axis causes a gyroscopic moment relative to the y-axis, and vice versa, ultimately resulting in the motion of the propeller shaft becoming an elliptical gyroscopic motion.

[0008] Considering the propeller rotation speed of Ω and the oncoming flow velocity of V ∞ , the described gyro mode vibration shape will cause a change in the angle of attack of the propeller blade, and they generate unsteady aerodynamic forces, which will cause flutter instability under specific conditions. From the perspective of flight stability, the critical flutter speed is represented by V FL , as shown in Figure 9. When the oncoming flow velocity V ∞ < V FL , the motion is stable, and the rotation of the rotating shaft converges towards the center, as shown in Figure 9(a); when V ∞ > V FL , the motion is divergent, and the motion amplitude of the rotating shaft becomes larger and larger, as shown in Figure 9(b), and ultimately will lead to structural instability and failure.

[0009] The present invention provides a precession simulation device for spiral flutter wind tunnel tests, which solves the problem of the design of spiral flutter wind tunnel tests for the rotating body of a rotorcraft. By simulating the precession motion mode caused by the gyroscopic effect (gyroscopic effect), key influencing parameters of the spiral flutter characteristics of the aircraft are obtained, and the influence of key parameters on the spiral flutter boundary speed V FLInfluence law. The technical solution provided by this invention patent can simulate the free rotation of the aircraft's rotating system (including engine rotor, rotating shaft, rotor, etc.) in a wind tunnel and adjust the rotation speed of the rotating body through a motor. At the same time, the pitch and yaw degrees of freedom of the rotating shaft of the rotating system are released, enabling it to rotate around the pitch axis and the yaw axis. At the same time, the axes of the pitch axis and the yaw axis coincide. Thus, under the action of the gyroscopic moment, the rotating body can achieve pitch and yaw coupled precession motion. At the same time, the pitch and yaw degrees of freedom of the rotating shaft are respectively supported by unidirectional spring plates and decoupling pins, enabling the modal frequency of a single degree of freedom to be adjustable. Thus, the support stiffness of the rotating body can be reasonably designed to study the influence of the support stiffness on the spiral flutter boundary. A counterweight is designed to adjust the weight and the center of gravity position of the nacelle to study the influence of factors such as weight and center of gravity position on the spiral flutter boundary speed.

[0010] To achieve the above object, the technical solution of the present invention is as follows:

[0011] A precession simulation device for spiral flutter wind tunnel tests, comprising: a speed regulating motor, a coupling, a rotating shaft, a bearing seat, a hub, a pitch axis, a yaw axis, a pitch spring plate, a yaw spring plate, a pitch decoupling pin, a yaw decoupling pin, a hub limiter, a counterweight, and a blade clamp.

[0012] Figure 1 Among them, the speed regulating motor is fixed on the tray, and its output shaft is connected to the coupling. The coupling is responsible for connecting the output shaft of the motor and the rotating shaft. The rotating shaft is fixed on the tray through two bearing seats, transmitting the force and torque of the rotating body to the tray. The rotating body includes a rotating shaft, a hub, a blade clamp, and a rotor.

[0013] The end of the rotating shaft is connected to the hub. The hub is connected to 3 blade clamps, and the 3 blade clamps are respectively connected to 3 blades. The angle between every two blade clamps is 120°. The hub is fixed on the rotating shaft through a hub limiter.

[0014] The hub is of a detachable type. After disassembling, the angle of the blade clamp can be adjusted, and thus the pitch of the rotor blade can be adjusted.

[0015] Figure 2 Among them, the tray is responsible for fixing the motor and the rotating system and bearing the force and torque from the motor and the rotating body through the bearing seat. The tray is connected to the yaw bracket through the pitch axes on its left and right sides. When the yaw bracket is fixed, the tray together with the motor and the rotating body fixed thereon can rotate freely around the pitch axis.

[0016] Figure 3Among them, the left and right sides of the yaw support are pitch axes, and at the same time, yaw axes are designed at its upper and lower ends. The yaw axes are connected to the nacelle cage through bearings. When the nacelle cage is fixed, the yaw support together with the tray can freely rotate around the yaw axis. The axes of the yaw axis and the pitch axis coincide at a point P. This design can ensure that the rotational motion of the rotating body around the pitch axis and the yaw axis is coupled into a vortex motion around P.

[0017] Figure 3 The midpoint A of the upper beam of the yaw support in Figure 4 is connected to point C of the pitch spring leaf in

[0018] Figure 3 Among them, the yaw support is a frame structure, with fixed planes on both sides, and the upper beam and the lower beam of the yaw support respectively at the upper and lower parts. Yaw axes are vertically provided at the central positions of the upper beam and the lower beam of the yaw support, and the axes of the yaw axes of the upper beam and the lower beam coincide. The other ends of the yaw axes are connected to the nacelle cage through bearings, and the nacelle cage is connected to the wing through bolts. When the nacelle cage is fixed, the yaw support can rotate around the yaw axis. Similar to the pitch degree of freedom, the yaw spring leaf and the yaw decoupling pin are vertically fixed and form a support structure for the yaw degree of freedom. By adjusting the thickness of the yaw spring leaf, the yaw frequency of the rotating body can be changed.

[0019] The axes of the yaw axis and the pitch axis coincide at a point P, ensuring that when the rotating body rotates, under the action of the gyroscopic effect, a precession motion of the rotating body around point P can be generated.

[0020] Figure 1 Among them, a counterweight is designed on the tail shaft of the tray, and its counterweight size and front and rear positions can be adjusted, enabling the adjustment of the weight and center of gravity of the nacelle to study the influence law of the nacelle weight factor on the spiral flutter boundary velocity.

[0021] The overall installation schematic diagram of the precession simulation device is shown in Figure 5 and Figure 6 as shown. Among them, Figure 5 shows the installation schematic diagram of the precession simulation device on the nacelle cage. The nacelle cage suspends the precession simulation device through the yaw axis and is fixed to the wing through bolts. Figure 6Disclosed is a precession simulation device for a tilt-rotor aircraft spiral flutter wind tunnel test model, including a rigid wing, an elastic wing, a nacelle cage and a precession simulation device. The nacelle cage is installed on the elastic wing through bolts, the elastic wing is fixed on the wind tunnel wall, and the rigid fuselage is also fixed on the wind tunnel wall. The fuselage only serves to maintain its aerodynamic shape.

[0022] A further improvement of the present invention lies in that the pitch and yaw modes of the nacelle and the rotor are designed to be decoupled. The pitch degree of freedom of the nacelle is realized by rotation around the pitch axis, and the yaw degree of freedom of the nacelle is realized by rotation around the yaw axis. The modal frequencies of the pitch and yaw degrees of freedom can be independently adjusted by adjusting the thickness of the pitch spring plate and the yaw spring plate, and the pitch and yaw frequency parameters of the nacelle during the wind tunnel test can be changed. The axes of the pitch axis and the yaw axis intersect at a point, ensuring that the pitch and yaw motions can be coupled into a precession motion under the action of the gyroscopic moment.

[0023] A further improvement of the present invention lies in that the rotational speed of the rotor can be adjusted by a speed control motor and a coupling system. The rotational speed of the rotor does not depend on the wind tunnel flow velocity, and the rotational speed parameters during the wind tunnel test can be changed.

[0024] A further improvement of the present invention lies in that the weight and the center of gravity position of the nacelle can be adjusted by counterweight blocks, and the mass and the center of mass position parameters of the rotating mass during the wind tunnel test can be changed.

[0025] A method for using a precession simulation device for a spiral flutter wind tunnel test is as follows:

[0026] The first step: The speed control motor is fixed on the tray, and its output shaft is connected to the coupling. The coupling is responsible for connecting the output shaft of the motor and the rotating shaft. The rotating shaft is fixed on the tray through two bearing seats, transmitting the force and torque of the rotating body to the tray. The end of the rotating shaft is connected to the hub, the hub is connected to 3 blade clamps, and the 3 blade clamps are respectively connected to 3 blades. The hub is responsible for adjusting the rotor pitch.

[0027] The second step: The tray is responsible for fixing the motor and the rotating system and bearing the force and torque from the motor and the rotating body through the bearing seats. The tray is connected to the yaw bracket through the pitch axes on its left and right sides. When the yaw bracket is fixed, the tray together with the motor and the rotating system fixed thereon can rotate freely around the pitch axis.

[0028] The third step: The pitch axes on the left and right sides of the yaw bracket are designed with yaw axes at their upper and lower ends. The yaw axes are connected to the nacelle cage through bearings. When the nacelle cage is fixed, the yaw bracket together with the tray can rotate freely around the yaw axis. Note: The axes of the yaw axis and the pitch axis coincide at a point P. This design can ensure that the rotational motions of the rotating body around the pitch axis and the yaw axis can be coupled into a vortex motion around P.

[0029] Step 4: The midpoint A of the upper beam of the yaw bracket is connected to point Z of the pitch spring plate. The pitch spring plate is connected to the pitch decoupling pin, and the pitch decoupling pin is connected to the tail end shaft of the tray. When the tray rotates around the pitch axis, it is restricted by the pitch decoupling pin and the pitch spring plate. Since the diameter of the pitch decoupling pin is relatively thin, it can only transmit axial tensile and compressive forces and does not transmit bending moments. Therefore, the support stiffness of the pitch degree of freedom is only affected by the thickness of the pitch spring plate. By adjusting the thickness of the pitch spring plate, the independent adjustment of the pitch frequency can be achieved, and the yaw frequency will not be significantly affected.

[0030] Step 5: Yaw axes are also designed at the upper and lower beam ends of the yaw bracket. The yaw axes are connected to the nacelle cage through bearings, and the nacelle cage is connected to the wing through bolts. Relative to the nacelle cage, the yaw bracket can rotate around the yaw axis. Similar to the pitch degree of freedom, the yaw spring plate and the yaw decoupling pin support the yaw degree of freedom, and adjusting the thickness of the yaw spring plate will not have a significant impact on the pitch frequency.

[0031] Step 6: The axes of the yaw axis and the pitch axis coincide at a point P, ensuring that when the rotating body rotates, under the action of the gyroscopic effect, a precession motion of the rotating body around point A can be generated.

[0032] Step 7: A counterweight is designed on the tail shaft of the tray, and its counterweight size and front-back position can both be adjusted, enabling the adjustment of the nacelle weight and center of gravity, and used to study the influence law of the nacelle weight factor on the spiral flutter boundary velocity.

[0033] Step 8: The overall installation schematic diagram of the precession simulation device is as shown in Figure 2 and Figure 3 shown. Among them, the precession simulation device is installed on the nacelle cage through the yaw axis, the nacelle cage is installed on the wing through bolts, the wing is fixed on the wind tunnel wall, and the rigid fuselage is only responsible for the profile.

[0034] Compared with the current technology, the present invention has the following beneficial effects:

[0035] The present invention solves the problem of experimental prediction of the spiral flutter boundary of a tiltrotor aircraft, and obtains the key influencing parameters of the spiral flutter characteristics of the tiltrotor aircraft and the influence law of the key parameters. The present invention can achieve the decoupling of the nacelle pitch and yaw modes, and the nacelle pitch and yaw mode frequencies can be independently adjusted; at the same time, it can achieve the adjustment of the rotational inertia of the rotating mass of the nacelle, the nacelle weight and the position of the center of mass; finally, through the speed control motor, the rotational speed of the rotating masses such as the rotor and the hub can be adjusted to ensure the matching of the rotational speed and the oncoming flow velocity, and reach the spiral flutter state. It effectively supports the development of tiltrotor aircraft models. Description of the Drawings

[0036] Figure 1 Nacelle precession motion simulation device diagram;

[0037] Figure 2 Nacelle tray and rotating body diagram;

[0038] Figure 3 Yaw support diagram;

[0039] Figure 4 Detailed schematic diagram of pitch, yaw spring plates and decoupling pins;

[0040] Figure 5(a) Perspective view of nacelle structure;

[0041] Figure 5(b) Front view of nacelle structure;

[0042] Figure 6 Schematic diagram of tilt-rotor aircraft spiral flutter wind tunnel test model device;

[0043] Figure 7(a) Schematic diagram of pitch motion;

[0044] Figure 7(b) Schematic diagram of yaw motion;

[0045] Figure 8(a) Schematic diagram of backward vortex motion during precession;

[0046] Figure 8(b) Schematic diagram of forward vortex motion during precession;

[0047] Figure 9(a) V < V FL Schematic diagram of spiral flutter convergence and divergence;

[0048] Figure 9(b) V > V FL Schematic diagram of spiral flutter convergence and divergence.

[0049] In the figure: 1 fuselage; 2 elastic wing; 2(a) elastic wing beam; 2(b) elastic wing rib; 3 nacelle cage; 4 nacelle; 5 rotor; 7 speed control motor; 8 coupling; 9 rotating shaft; 10 bearing seat; 11 hub; 12 pitch axis; 13 yaw axis; 14 pitch spring plate; 15 yaw spring plate; 16 pitch decoupling pin; 17 yaw decoupling pin; 18 hub stopper; 19 counterweight; 21 blade clip; 22 tray; 23 yaw support. Detailed implementation method

[0050] Example 1:

[0051] The present invention provides a precession simulation device for spiral flutter wind tunnel tests, as Figure 1 shown, including: speed control motor 7, coupling 8, rotating shaft 9, bearing seat 10, hub 11, pitch axis 12, yaw axis 13, pitch spring plate 14, yaw spring plate 15, pitch decoupling pin 16, yaw decoupling pin 17, hub stopper 18, counterweight 19 and blade clip 21.

[0052] Figure 1Among them, the speed-regulating motor 7 is fixed on the tray 22, and its output shaft is connected to the coupling 8. The coupling 8 is responsible for connecting the output shaft of the motor 7 and the rotating shaft 9. The rotating shaft 9 is fixed on the tray 22 through two bearing seats 10, transmitting the force and torque of the rotating body to the tray 22. The rotating body includes the rotating shaft 9, the hub 11, the blade clamp 21 and the rotor 5.

[0053] The end of the rotating shaft 9 is connected to the hub 11. The hub 11 is connected to 3 blade clamps 21. The 3 blade clamps 21 are respectively connected to 3 blades. The angle between every two blade clamps 21 is 120°. The hub 11 is fixed on the rotating shaft 9 through the hub limiter 18.

[0054] The hub 11 is of a detachable type. After disassembly, the angle of the blade clamp can be adjusted, thereby adjusting the pitch of the rotor blade.

[0055] Figure 2 Among them, the tray 22 is responsible for fixing the motor 7 and the rotating system, and bearing the force and torque from the motor and the rotating body through the bearing seats 10. The tray 22 is connected to the yaw bracket 23 through the pitch axes 12 on its left and right sides. When the yaw bracket 23 is fixed, the tray 22 together with the motor 7 and the rotating body fixed thereon can freely rotate around the pitch axis 12.

[0056] Figure 3 Among them, the left and right sides of the yaw bracket 23 are the pitch axes 12, and at the same time, the upper and lower ends thereof are designed with yaw axes 13. The yaw axes 13 are connected to the nacelle cage 3 through bearings. When the nacelle cage 3 is fixed, the yaw bracket 23 together with the tray 22 can freely rotate around the yaw axes 13. The axes of the yaw axes 13 and the pitch axes 12 coincide at a point P. This design can ensure that the rotational movement of the rotating body around the pitch axis 12 and the yaw axis 13 is coupled into a whirling motion around P.

[0057] Figure 3 The midpoint A of the upper beam of the yaw bracket 23 in Figure 4 is connected to point C of the pitch spring piece 14 in

[0058] Figure 3In it, the yaw support 23 is of a frame structure, with fixed planes on both sides, and the upper beam and the lower beam of the yaw support 23 are respectively on the upper and lower parts. Yaw axes 13 are vertically provided at the central positions of the upper beam and the lower beam of the yaw support 23, and the axes of the yaw axes 13 of the upper beam and the lower beam coincide. The other ends of the yaw axes 13 are connected to the nacelle cage 3 through bearings, and the nacelle cage 3 is connected to the wing 2 through bolts. When the nacelle cage 3 is fixed, the yaw support 23 can rotate around the yaw axis 13. Similar to the pitch degree of freedom, the yaw spring plate 15 and the yaw decoupling pin 17 are vertically fixed and constitute the support structure of the yaw degree of freedom. By adjusting the thickness of the yaw spring plate 15, the yaw frequency of the rotating body can be changed.

[0059] The axes of the yaw axis 12 and the pitch axis 13 coincide with a point P, ensuring that when the rotating body rotates, under the action of the gyroscopic effect, a precession motion of the rotating body around point P can be generated.

[0060] Figure 1 In it, a counterweight 19 is designed on the tray tail shaft, and its counterweight size and front and rear positions are adjustable, enabling the adjustment of the nacelle weight and the center of gravity, so as to study the influence law of the nacelle weight factor on the spiral flutter boundary speed.

[0061] The overall installation schematic diagram of the precession simulation device is shown in Figure 5 and Figure 6 as shown. Among them, Figure 5 shows the installation schematic diagram of the precession simulation device on the nacelle cage 3. The nacelle cage 3 suspends the precession simulation device through the yaw axis 13 and is fixed to the wing 2 through bolts. Figure 6 shows the tilt-rotor aircraft spiral flutter wind tunnel test model device, including a rigid wing 1, an elastic wing 2, a nacelle cage 3 and a precession simulation device. Among them, the nacelle cage 3 is installed on the elastic wing 2 through bolts, the elastic wing 2 is fixed on the wind tunnel wall, and the rigid fuselage 1 is also fixed on the wind tunnel wall. The fuselage only serves to maintain its aerodynamic shape.

[0062] The pitch and yaw modes of the nacelle 4 and the rotor 5 are designed to be decoupled. The pitch degree of freedom of the nacelle 4 is realized by rotating around the pitch axis 12, and the yaw degree of freedom of the nacelle is realized by rotating around the yaw axis 13. The modal frequencies of the pitch and yaw degrees of freedom can be independently adjusted by adjusting the thicknesses of the pitch spring plate 14 and the yaw spring plate 15, and the pitch and yaw frequency parameters of the nacelle during the wind tunnel test can be changed. The axes of the pitch axis 12 and the yaw axis 13 intersect at a point, ensuring that the pitch and yaw motions can be coupled into a precession motion under the action of the gyroscopic moment.

[0063] The rotational speed of the rotor 5 can be adjusted through a speed control motor and a coupling system. The rotational speed of the rotor 5 does not depend on the wind tunnel flow velocity, and the rotational speed parameters during the wind tunnel test can be changed.

[0064] The weight and center of gravity position of the nacelle can be adjusted by the counterweight, so that the mass and center of gravity position parameters of the rotating mass can be changed during the wind tunnel test.

[0065] Embodiment 2:

[0066] A method for using a spiral flutter wind tunnel test precession simulation device, the steps are as follows:

[0067] Step 1: The speed regulating motor 7 is fixed on the tray 22, and its output shaft is connected to the coupling 8. The coupling 8 is responsible for connecting the output shaft of the motor 7 and the rotating shaft 9. The rotating shaft 9 is fixed on the tray 22 through two bearing seats 10 to transmit the force and torque of the rotating body to the tray 22. The end of the rotating shaft is connected to the propeller hub 11, and the propeller hub 11 is connected to three blade clamps 21. The three blade clamps 21 are respectively connected to three blades. The propeller hub 11 is responsible for adjusting the rotor pitch.

[0068] Step 2: The tray 22 is responsible for fixing the motor 7 and the rotating system, and bears the force and torque from the motor and the rotating body through the bearing seat 10. The tray 22 is connected to the yaw bracket 23 through the pitch axis 12 on its left and right sides. When the yaw bracket 23 is fixed, the tray 22, together with the motor 7 and the rotating system fixed thereon, can rotate freely around the pitch axis 12.

[0069] Step 3: The pitch axis 12 on the left and right sides of the yaw bracket 23 is designed with a yaw axis 13 at its upper and lower ends. The yaw axis 13 is connected to the nacelle cage 3 through a bearing. When the nacelle cage 3 is fixed, the yaw bracket 23 together with the tray 22 can rotate freely around the yaw axis 13. Note: The axes of the yaw axis 13 and the pitch axis 12 coincide with each other at a point P. This design can ensure that the rotational motion of the rotating body around the pitch axis 12 and the yaw axis 13 can be coupled into a vortex around P.

[0070] Step 4: The midpoint A of the upper beam of the yaw bracket 23 is connected to the point Z of the pitch spring sheet 14, the pitch spring sheet 14 is connected to the pitch decoupling needle 16, and the pitch decoupling needle 16 is connected to the tail end axis of the tray 22. When the tray 22 rotates around the pitch axis 12, it is restricted by the pitch decoupling needle 16 and the pitch spring sheet 12. Since the pitch decoupling needle 16 has a thin diameter, it can only transmit axial tension and pressure, but not bending moment. Therefore, the support stiffness of the pitch degree of freedom is only affected by the thickness of the pitch spring sheet. By adjusting the thickness of the pitch spring sheet 14, the pitch frequency can be independently adjusted without significantly affecting the yaw frequency.

[0071] Step 5: Yaw axes 13 are also designed at the upper and lower beam ends of the yaw bracket 23. The yaw axes 13 are connected to the nacelle cage 3 through bearings, and the nacelle cage 3 is connected to the wing 2 through bolts. Relative to the nacelle cage 3, the yaw bracket 23 can rotate around the yaw axes 13. Similar to the pitch degree of freedom, the yaw spring plates 15 and the yaw decoupling pins 17 support the yaw degree of freedom, and adjusting the thickness of the yaw spring plates 15 will not have a significant impact on the pitch frequency.

[0072] Step 6: The axes of the yaw axis 12 and the pitch axis 13 coincide at a point P, ensuring that when the rotating body rotates, under the action of the gyroscopic effect, a precessional motion of the rotating body around point A can be generated.

[0073] Step 7: A counterweight 19 is designed on the shaft at the tail of the tray. The size and the front and rear positions of the counterweight can be adjusted, enabling the adjustment of the weight and the center of gravity of the nacelle to study the influence law of the nacelle weight factor on the spiral flutter boundary velocity.

[0074] Step 8: The overall installation schematic diagram of the precession simulation device is as shown in Figure 2 and Figure 3 wherein the precession simulation device is installed on the nacelle cage 3 through the yaw axis 13. The nacelle cage 3 is installed on the wing 1 through bolts, the wing is fixed on the wind tunnel wall, and the rigid fuselage is only responsible for the shape.

Claims

1. A precession simulation device for spiral flutter wind tunnel tests, characterized in that, It includes a speed-regulating motor (7), a coupling (8), a rotating shaft (9), a bearing housing (10), a hub (11), a pitch axis (12), a yaw axis (13), a pitch spring strip (14), a yaw spring strip (15), a pitch decoupling pin (16), a yaw decoupling pin (17), a hub limiter (18), a counterweight (19) and a blade clamp (21). The speed-regulating motor (7) is fixed on a tray (22), and its output shaft is connected to the coupling (8). The coupling (8) is responsible for connecting the output shaft of the motor (7) and the rotating shaft (9). The rotating shaft (9) is fixed on the tray (22) through two bearing housings (10), transmitting the force and torque of the rotating body to the tray (22). The rotating body includes a rotating shaft (9), a hub (11), a blade clamp (21) and a rotor (5). The end of the rotating shaft (9) is connected to the hub (11), and the hub (11) is connected to 3 blade clamps (21). The tray (22) is connected to a yaw bracket (23) through the pitch axes (12) on its left and right sides. When the yaw bracket (23) is fixed, the tray (22) together with the motor (7) and the rotating body fixed thereon can freely rotate around the pitch axis (12). The left and right sides of the yaw bracket (23) are pitch axes (12), and at the same time, yaw axes (13) are designed at its upper and lower ends. The yaw axes (13) are connected to the nacelle cage (3) through bearings. When the nacelle cage (3) is fixed, the yaw bracket (23) together with the tray (22) can freely rotate around the yaw axis (13). The axes of the yaw axis (13) and the pitch axis (12) coincide at a point P. This design can ensure that the rotational motion of the rotating body around the pitch axis (12) and the yaw axis (13) is coupled into a whirling motion around P. The yaw bracket (23) is of a frame structure, with two fixed planes on both sides, and the upper beam and the lower beam of the yaw bracket (23) respectively at the upper and lower parts. The center positions of the upper beam and the lower beam of the yaw bracket (23) are respectively vertically provided with yaw axes (13), and the axes of the yaw axes (13) on the upper beam and the lower beam coincide. The other ends of the yaw axes (13) are connected to the nacelle cage (3) through bearings, and the nacelle cage (3) is connected to the wing (2) through bolts. When the nacelle cage (3) is fixed, the yaw bracket (23) can rotate around the yaw axis (13). Similar to the pitch degree of freedom, the yaw spring strip (15) and the yaw decoupling pin (17) are vertically fixed and form a support structure for the yaw degree of freedom. By adjusting the thickness of the yaw spring strip (15), the yaw frequency of the rotating body can be changed. The axes of the yaw axis (12) and the pitch axis (13) coincide at a point P, ensuring that when the rotating body rotates, under the action of the gyroscopic effect, a precession motion of the rotating body around point P can be generated.

2. The precession simulation device for the spiral flutter wind tunnel test according to claim 1, characterized in that The midpoint A of the upper beam of the yaw bracket (23) is connected to point C of the pitch spring strip (14). The pitch spring strip (14) is vertically fixed to the pitch decoupling pin (16), and the other end of the pitch decoupling pin (16) is fixed to the tail-end shaft of the tray (22).

3. The precession simulation device for a helical flutter wind tunnel test according to claim 1, characterized in that, The three blade clamps (21) are respectively connected to three blades, and the angle between every two blade clamps (21) is 120°. The hub (11) is fixed on the rotating shaft (9) through a hub limiter (18).

4. The precession simulation device for the spiral flutter wind tunnel test according to claim 1, characterized in that, The hub (11) is of a detachable type. After disassembly, the angle of the blade clamp can be adjusted, thereby adjusting the pitch of the rotor blade.

5. The precession simulation device for a helical flutter wind tunnel test according to claim 1, characterized in that, A counterweight (19) is designed on the tail shaft of the tray (22), and both the weight and the front and rear positions of the counterweight can be adjusted, enabling the adjustment of the weight and the center of gravity of the nacelle.

6. The precession simulation device for spiral flutter wind tunnel test according to claim 1, characterized in that, The nacelle cage (3) suspends the precession simulation device through a yaw axis (13) and is fixed to the wing (2) by bolts.

7. The precession simulation device for a helical flutter wind tunnel test according to claim 1, wherein, The pitching and yawing modes of the nacelle (4) and the rotor (5) are designed to be decoupled. The pitching degree of freedom of the nacelle (4) is achieved by rotation around the pitching axis (12), and the yawing degree of freedom of the nacelle is achieved by rotation around the yaw axis (13); the modal frequencies of the pitching and yawing degrees of freedom can be independently adjusted by adjusting the thicknesses of the pitching spring plate (14) and the yawing spring plate (15); the axes of the pitching axis (12) and the yaw axis (13) intersect at a point, ensuring that the pitching and yawing motions can be coupled into a precession motion under the action of gyroscopic torque.

8. The precession simulation device for a spiral flutter wind tunnel test according to claim 1, characterized in that, The rotational speed of the rotor (5) is adjusted by a speed control motor and a coupling system. The rotational speed of the rotor (5) does not depend on the flow velocity of the wind tunnel, and the rotational speed parameters during wind tunnel tests can be changed.

9. The precession simulation device for a spiral flutter wind tunnel test according to claim 1, characterized in that, The weight and the position of the center of gravity of the nacelle (4) can be adjusted by counterweights, enabling the change of the mass and the position of the center of mass of the rotating mass during wind tunnel tests.

10. A method for using a precession simulation device for a spiral flutter wind tunnel test according to any one of claims 1 to 9, characterized in that, The steps are as follows: First step: The speed control motor (7) is fixed on the tray (22), and its output shaft is connected to the coupling (8). The coupling (8) is responsible for connecting the output shaft of the motor (7) and the rotating shaft (9). The rotating shaft (9) is fixed on the tray (22) through two bearing seats (10), transmitting the force and torque of the rotating body to the tray (22); the end of the rotating shaft is connected to the hub (11), the hub (11) is connected to three blade clamps (21), and the three blade clamps (21) are respectively connected to three blades. The hub (11) is responsible for adjusting the rotor pitch. Second step: The tray (22) is responsible for fixing the motor (7) and the rotating system and bearing the force and torque from the motor and the rotating body through the bearing seats (10); the tray (22) is connected to the yaw support (23) through the pitching axes (12) on its left and right sides; when the yaw support (23) is fixed, the tray (22) together with the motor (7) and the rotating system fixed thereon can rotate freely around the pitching axis (12). Third step: On the pitching axes (12) on the left and right sides of the yaw support (23), yaw axes (13) are designed at the upper and lower ends. The yaw axes (13) are connected to the nacelle cage (3) through bearings. When the nacelle cage (3) is fixed, the yaw support (23) together with the tray (22) can rotate freely around the yaw axis (13). Fourth step: The pitching spring plate (14) is connected to the pitching decoupling pin (16), and the pitching decoupling pin (16) is connected to the tail shaft of the tray (22). Step 5: Yaw shafts (13) are also designed at the upper and lower beam ends of the yaw support (23). The yaw shafts (13) are connected to the nacelle cage (3) through bearings, and the nacelle cage (3) is connected to the wing (2) through bolts; Step 6: The axes of the yaw shaft (12) and the pitch shaft (13) coincide with a point P. This ensures that when the rotating body rotates, under the action of the gyroscopic effect, a precessional motion of the rotating body around point A can be generated; Step 7: A counterweight (19) is designed on the shaft at the tail of the tray, and both its weight and the front-back position can be adjusted; Step 8: The precession simulation device is installed on the nacelle cage (3) through the yaw shaft (13). The nacelle cage (3) is installed on the wing (1) through bolts, and the wing is fixed on the wind tunnel wall. The rigid fuselage only serves for shaping.

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