Test method of four-meter scale wind tunnel tilt-rotor based on four-degree-of-freedom support platform

Abstract

The application provides a 4-meter wind tunnel tilt-rotor test method based on a four-degree-of-freedom support platform, and belongs to the technical field of wind tunnel test of tilt-rotor. The purpose is to solve the problems of high operation cost, complex test preparation, long occupation period and being not conducive to rapid screening and verification of new aerodynamic layout in the prior art that a 2-meter tilt-rotor model test is carried out in a large-size wind tunnel with a size of 8 meters or more, although the tilt process can be completely simulated. In the application, S1 is horizontal direction leveling of the tilt-rotor; S2 is straightening along the axis of the wind tunnel; S3 is active compensation of the spatial position of the tilt-rotor; and S4 is the wind tunnel test of the tilt-rotor. The application solves the problems of high operation cost, complex test preparation, long occupation period and being not conducive to rapid screening and verification of new aerodynamic layout in the prior art that a 2-meter tilt-rotor model test is carried out in a large-size wind tunnel with a size of 8 meters or more, although the tilt process can be completely simulated.

Description

Technical Field

[0001] This invention belongs to the field of tilt rotor wind tunnel testing technology, and particularly relates to a 4-meter-scale wind tunnel tilt rotor testing method based on a four-degree-of-freedom support platform. Background Technology

[0002] Tiltrotor configurations have become a research hotspot for low-altitude aircraft (such as flying cars and logistics drones) due to their unique vertical takeoff and landing and high-speed cruise capabilities. However, their complex rotor / rotor and rotor / wing aerodynamic interferences, especially the unsteady aerodynamic characteristics during tilt transition, make wind tunnel testing an indispensable research tool.

[0003] Currently, for tiltrotor models with a diameter in the range of 2 meters, in order to simulate the complete tilting process from helicopter mode to fixed-wing mode and avoid the model exceeding the uniform airflow range during tilting, the industry practice is to choose a wind tunnel of 8 meters or larger for testing. For example, there are existing cases of conducting full-size / scaled-size rotor performance tests in 8-meter × 6-meter wind tunnels (such as CN114001919B). However, large-size wind tunnels have disadvantages such as high operating costs, complex test preparation, and long occupancy periods, which are not conducive to the rapid screening and verification of aerodynamic layouts for new models.

[0004] In summary, there is an urgent need to design a 4-meter-scale wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform. This would solve the problems of existing technologies that use large-size wind tunnels of 8 meters or more to conduct 2-meter-scale tilt rotor model tests, which, although able to fully simulate the tilting process, suffer from high operating costs, complex test preparation, long cycle time, and are not conducive to the rapid screening and verification of aerodynamic layouts for new models. Summary of the Invention

[0005] A brief overview of the invention is given below to provide a basic understanding of certain aspects of it. It should be understood that this overview is not an exhaustive summary of the invention. It is not intended to identify key or essential parts of the invention, nor is it intended to limit the scope of the invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0006] In view of this, in order to solve the problems of high operating costs, complex test preparation, long occupation period, and unfavorable to the rapid screening and verification of aerodynamic layout of new models, the present invention provides a 4-meter-scale wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform.

[0007] Solution: A wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform with a diameter of 4 meters. The specific steps are as follows:

[0008] S1. Rotor horizontal leveling:

[0009] The tilt rotor test bench was installed in a 4-meter wind tunnel. The tilt angle of the upper surface of the balance floating frame was measured using a tilt meter. By adjusting the pitch mechanism of the four-degree-of-freedom support platform, the tilt angle of the upper surface of the floating frame was made no greater than 3′, ensuring that the perpendicularity of the rotor rotation plane to the airflow direction met the accuracy requirements.

[0010] S2. Straighten along the wind tunnel axis:

[0011] A laser line is drawn along the central axis of the wind tunnel. The rotor sideslip angle is adjusted by rotating the four-degree-of-freedom support platform around the center mechanism. The rotor position is adjusted by moving the four-degree-of-freedom support platform in the vertical airflow direction. The central scale line of the balance is made to coincide with the laser line, ensuring that the rotor is in the center of the wind tunnel and eliminating sideslip angle error.

[0012] S3. Active spatial position compensation for tilt rotor:

[0013] There is a lever arm L between the tilting axis of the tilt rotor and the center of the hub. When the tilting angle θ of the rotor shaft changes, the center of the hub will generate a significant spatial displacement. In order to ensure that it is in the limited uniform flow field of the 4-meter wind tunnel, it is necessary to compensate for its vertical position and longitudinal position.

[0014] By using active position compensation based on geometric relationships, it is ensured that the rotor hub center is always precisely located in the central region of the core flow field of the wind tunnel at different tilt angles.

[0015] S4. Tilter rotor wind tunnel test:

[0016] S41. Tilt rotor tilts to initial angle;

[0017] S42. The rotor maintains a small collective pitch as it rotates to the rated speed. The wind tunnel starts to blow. During the wind blowing process, the trim program is activated. The initial thrust is set to ensure that the rotor is always under positive thrust during the wind blowing process until the wind speed reaches the target wind speed. Then, the rotor is re-trimmed to the specified thrust coefficient state, while ensuring that the pitching moment and roll moment are controlled within ±50Nm.

[0018] S43. After balancing and stabilizing, aerodynamic data is collected for 80 revolutions, with 64 points per revolution. The six-component aerodynamic load and rotor torque of the rotor balance are obtained by Fourier transform.

[0019] S44. Change the tensile coefficient and repeat step S43;

[0020] S45. Change the wind speed and repeat steps S42-S44 until all test states at the current tilt angle are completed;

[0021] S46. Change the rotor shaft tilt angle, and repeat S3, S42, S43, S44, and S45 until all tilt angle states are completed.

[0022] Furthermore, the vertical position compensation described in S3: When the fixed-wing mode tilts to the helicopter mode, i.e., the rotor shaft pitches up, the rotor hub center rises; at this time, a height block is inserted between the four-degree-of-freedom support platform and the wind tunnel to perform upward compensation. The compensation height h is determined by the following formula:

[0023] ;

[0024] Where θ is the rotor shaft tilt angle;

[0025] Conversely, when tilting from helicopter mode to fixed-wing mode, i.e., when the rotor shaft pitches down, the rotor hub center lowers; at this time, the height block is removed, and the compensation height h is determined by the following formula:

[0026] .

[0027] Furthermore, regarding the longitudinal position compensation described in S3: when tilting from helicopter mode to fixed-wing mode, the rotor hub center moves towards the wind tunnel nozzle position along the airflow direction; at this time, compensation is performed backward along the airflow direction through the airflow direction moving mechanism of the four-degree-of-freedom support platform, and the compensation distance d is determined by the following formula:

[0028] ;

[0029] Conversely, when the fixed-wing mode is tilted towards the helicopter mode, the rotor hub center moves towards the wind tunnel inlet along the airflow direction. At this time, compensation is performed forward along the airflow direction through the airflow direction moving mechanism of the four-degree-of-freedom support platform. The compensation distance d is determined by the following formula:

[0030] .

[0031] The present invention has the following advantages over the prior art:

[0032] 1. This invention breaks through spatial limitations and for the first time achieves a full-mode transition state test of a 2-meter tilt rotor in a small wind tunnel of 4 meters, breaking the technical barrier that large models must use large wind tunnels;

[0033] 2. This invention significantly reduces testing costs and energy consumption, simplifies the test preparation process, shortens the occupation period, and provides a low-cost, high-efficiency iterative verification platform, facilitating rapid iteration of aerodynamic layout optimization and control law design for tiltrotor aircraft;

[0034] 3. This invention ensures that the model is in the optimal flow field throughout the entire process through a geometric compensation algorithm, improving the accuracy and effectiveness of aerodynamic test data, and providing reliable and feasible experimental technical support for the dynamics research of large-size tilt rotors. Attached Figure Description

[0035] The accompanying drawings, which are included to provide a further understanding of the invention and form part of this invention, illustrate exemplary embodiments of the invention and are used to explain the invention, but do not constitute an undue limitation of the invention. In the drawings:

[0036] Figure 1 This is a schematic diagram of the four-degree-of-freedom support platform in the 4-meter-scale wind tunnel tilt rotor test method based on the four-degree-of-freedom support platform.

[0037] Figure 2 This is a schematic diagram of a wind tunnel test for a helicopter.

[0038] Figure 3 Schematic diagram of wind tunnel test under tilting transition conditions;

[0039] Figure 4 This is a schematic diagram of a wind tunnel test for a propeller-driven aircraft.

[0040] In the diagram, 1-rotation mechanism around the center, 2-pitch mechanism, 3-movement mechanism along the airflow direction, 4-movement mechanism perpendicular to the airflow direction, and 5-height block. Detailed Implementation

[0041] To make the technical solutions and advantages of the embodiments of the present invention clearer, the exemplary embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not an exhaustive list of all embodiments. It should be noted that, unless otherwise specified, the embodiments and features in the embodiments of the present invention can be combined with each other.

[0042] Example 1, Reference Figures 1-4 This embodiment describes a wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform with a 4-meter scale. The specific steps are as follows:

[0043] S1. Rotor horizontal leveling:

[0044] The tilt rotor test bench was installed in a 4-meter wind tunnel. The tilt angle of the upper surface of the balance floating frame was measured using an inclinometer. By adjusting the pitch mechanism 2 of the four-degree-of-freedom support platform, the tilt angle of the upper surface of the floating frame was made no greater than 3′, ensuring that the perpendicularity of the rotor rotation plane to the airflow direction met the accuracy requirements.

[0045] S2. Straighten along the wind tunnel axis:

[0046] A laser line is drawn along the central axis of the wind tunnel. The rotor sideslip angle is adjusted by rotating the four-degree-of-freedom support platform around the center mechanism 1. The rotor position is adjusted by moving the four-degree-of-freedom support platform in the vertical airflow direction by the vertical airflow direction moving mechanism 4. The central scale line of the balance is made to coincide with the laser line, ensuring that the rotor is in the center of the wind tunnel and eliminating sideslip angle error.

[0047] S3. Active spatial position compensation for tilt rotor:

[0048] The tilt rotor has a lever arm L between its tilt axis and the center of the hub. When the tilt angle θ of the rotor shaft changes, the center of the hub will experience a significant spatial displacement. To ensure its operation within the finite uniform flow field of a 4-meter wind tunnel, precise compensation is required, including vertical position compensation and longitudinal position compensation.

[0049] Through the above-mentioned active position compensation based on geometric relationships, it is ensured that the rotor hub center is always accurately located in the central region of the core flow field of the wind tunnel at different tilt angles.

[0050] S4. Tilter rotor wind tunnel test:

[0051] S41. Tilt rotor tilts to initial angle;

[0052] S42. The rotor maintains a small collective pitch as it rotates to the rated speed. The wind tunnel starts to blow. During the wind blowing process, the trim program is activated. The initial thrust is set to ensure that the rotor is always under positive thrust during the wind blowing process until the wind speed reaches the target wind speed. Then, the rotor is re-trimmed to the specified thrust coefficient state, while ensuring that the pitching moment and roll moment are controlled within ±50Nm.

[0053] S43. After balancing and stabilizing, aerodynamic data is collected for 80 revolutions, with 64 points per revolution. The six-component aerodynamic load and rotor torque of the rotor balance are obtained by Fourier transform.

[0054] S44. Change the tensile coefficient and repeat step S43;

[0055] S45. Change the wind speed and repeat steps S42-S44 until all test conditions at the current tilt angle are completed;

[0056] S46. Change the rotor shaft tilt angle, and repeat S3, S42, S43, S44, and S45 until all tilt angle states are completed.

[0057] Furthermore, the vertical position compensation described in S3: When the fixed-wing mode tilts to the helicopter mode, i.e., the rotor shaft pitches up, the rotor hub center rises; at this time, a height block 5 is inserted between the four-degree-of-freedom support platform and the wind tunnel to perform upward compensation. The compensation height h is determined by the following formula:

[0058] ;

[0059] Where θ is the rotor shaft tilt angle;

[0060] Conversely, when tilting from helicopter mode to fixed-wing mode, i.e., when the rotor shaft pitches down, the rotor hub center lowers; at this time, removing height block 5, the compensation height h is determined by the following formula:

[0061] .

[0062] Furthermore, regarding the longitudinal position compensation described in S3: when tilting from helicopter mode to fixed-wing mode, the rotor hub center moves towards the wind tunnel nozzle position along the airflow direction; at this time, compensation is performed backward along the airflow direction through the airflow direction moving mechanism 3 of the four-degree-of-freedom support platform, and the compensation distance d is determined by the following formula:

[0063] ;

[0064] Conversely, when the fixed-wing mode is tilted towards the helicopter mode, the rotor hub center moves towards the wind tunnel inlet along the airflow direction; at this time, compensation is performed forward along the airflow direction through the airflow direction moving mechanism 3 of the four-degree-of-freedom support platform, and the compensation distance d is determined by the following formula:

[0065] .

[0066] Furthermore, during the test, the blade profile load is amplified by an amplifier and transmitted to the rotor acquisition system via a slip ring. The blade load and rotor aerodynamic load are synchronously acquired by triggering the external clock.

[0067] Example 2, Reference Figures 1-4 This embodiment describes a wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform with a 4-meter scale. The specific steps are as follows:

[0068] S1. Rotor horizontal leveling:

[0069] The tilt rotor test bench was installed in a 4-meter wind tunnel. The tilt angle of the upper surface of the balance floating frame was measured using an inclinometer. By adjusting the pitch mechanism 2 of the four-degree-of-freedom support platform, the tilt angle of the upper surface of the floating frame was made no greater than 3′, ensuring that the perpendicularity of the rotor rotation plane to the airflow direction met the accuracy requirements.

[0070] S2. Straighten along the wind tunnel axis:

[0071] A laser line is drawn along the central axis of the wind tunnel. The rotor sideslip angle is adjusted by rotating the four-degree-of-freedom support platform around the center mechanism 1, so that the central scale line of the balance coincides with the laser line, ensuring that the rotor is in the center position of the wind tunnel and eliminating sideslip angle error.

[0072] S3. Active spatial position compensation for tilt rotor:

[0073] Taking a tilt rotor with a lever arm L=500mm between its tilt axis and hub center as an example:

[0074] ① When the tilt angle θ = 30°, the mode transitions from helicopter mode to fixed-wing mode;

[0075] 1) Vertical compensation height At this point, the corresponding height block 5 should be replaced so that the height block is lowered by 67mm relative to the helicopter mode, thus achieving downward compensation.

[0076] 2) Longitudinal supplementary distance At this point, compensation should be made by moving the mechanism 3 250mm backward along the airflow direction to counteract the forward movement of the rotor hub center;

[0077] ② When the tilt angle θ = 60°, the mode transitions from helicopter mode to fixed-wing mode;

[0078] 1) Vertical compensation height At this point, the corresponding height block 5 should be replaced so that it is lowered by 250mm relative to the helicopter mode, thus achieving downward compensation.

[0079] 2) Longitudinal supplementary distance At this point, compensation should be made by moving the moving mechanism 3 backward by 433mm along the airflow direction to counteract the forward movement of the rotor hub center;

[0080] ③ When the tilt angle θ = 90°, the tilt rotor is in fixed-wing mode;

[0081] 1) Vertical compensation height At this point, the corresponding height block 5 should be replaced so that it is lowered by 500mm relative to the helicopter mode, thus achieving downward compensation;

[0082] 2) Longitudinal supplementary distance At this point, compensation should be made by moving the mechanism 3 backward by 500mm along the airflow direction to counteract the forward movement of the rotor hub center;

[0083] Through the above compensation, the center of the propeller hub is always located at the central axis of the wind tunnel, ensuring that the model is always in the core uniform flow field.

[0084] S4. Tilter rotor wind tunnel test:

[0085] S41. The tilt rotor tilts to the initial tilt angle θ=0°, putting the tilt rotor into helicopter mode;

[0086] S42. With the rotor maintaining a small collective pitch (e.g., 2° collective pitch), rotate to the rated speed of 2000 RPM. Initiate wind tunnel operation to the target wind speed of 30 m / s. During wind initiation, activate the trim program and set the thrust target to 200 N to ensure the rotor remains under positive thrust throughout the wind initiation process. After the wind speed stabilizes, re-trim to the specified thrust coefficient (e.g., CT = 0.01).

[0087] S43. After balancing and stabilizing, aerodynamic data were collected for 80 revolutions, with 64 points per revolution. The six-component load of the balance and the rotor torque were obtained by Fourier transform.

[0088] S44. Change the tensile coefficient (e.g., CT=0.015, 0.02, etc.) and repeat step S43;

[0089] S45. Change the wind speed (e.g., 40m / s, 50m / s) and repeat steps S42-S44 until all test conditions at this tilt angle are completed.

[0090] S46. Change the rotor shaft tilt angle to θ=30°, and repeat S3, S42, S43, S44, S45 until all tilt angle states (such as 30°, 60°, 90°) are completed.

[0091] Furthermore, during the test, the blade profile load is amplified by an amplifier and transmitted to the rotor acquisition system via a slip ring. The blade load and rotor aerodynamic load are synchronously acquired by triggering the external clock.

[0092] This invention overcomes spatial limitations and enables the first-ever completion of a full-mode transition state test of a 2-meter tiltrotor aircraft in a small wind tunnel of 4 meters in size, breaking the technical barrier that large models must use large wind tunnels. At the same time, this invention significantly reduces test costs and energy consumption, simplifies test preparation procedures, shortens the occupation period, and provides a low-cost, high-efficiency iterative verification platform, facilitating rapid iteration of aerodynamic layout optimization and control law design for tiltrotor aircraft.

[0093] This invention uses a geometric compensation algorithm to ensure that the model is in the optimal flow field throughout the process, improving the accuracy and effectiveness of aerodynamic test data and providing reliable and feasible experimental technical support for the study of large-size tilt rotor dynamics.

[0094] Although the invention has been described with reference to a limited number of embodiments, those skilled in the art will understand from the foregoing description that other embodiments are conceivable within the scope of the invention described herein. Furthermore, it should be noted that the language used in this specification has been chosen primarily for readability and instructional purposes, and not for the purpose of interpreting or limiting the subject matter of the invention. Therefore, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the invention is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform for a 4-meter-scale rotor, characterized in that, The specific steps are as follows: S1. Rotor horizontal leveling: The tilt rotor test bench was installed in a 4-meter wind tunnel. The tilt angle of the upper surface of the balance floating frame was measured using an inclinometer. The tilt angle of the upper surface of the floating frame was adjusted by adjusting the pitch mechanism (2) of the four-degree-of-freedom support platform so that it was no greater than 3′, ensuring that the perpendicularity of the rotor rotation plane to the airflow direction met the accuracy requirements. S2. Straighten along the wind tunnel axis: A laser line is drawn along the central axis of the wind tunnel. The rotor sideslip angle is adjusted by rotating the four-degree-of-freedom support platform around the center (1). The rotor position is adjusted by moving the vertical airflow direction moving mechanism (4) of the four-degree-of-freedom support platform so that the central scale line of the balance coincides with the laser line, ensuring that the rotor is in the center position of the wind tunnel and eliminating sideslip angle error. S3. Active spatial position compensation for tilt rotor: There is a lever arm L between the tilting axis of the tilt rotor and the center of the hub. When the tilting angle θ of the rotor shaft changes, the center of the hub will generate a significant spatial displacement. In order to ensure that it is in the limited uniform flow field of the 4-meter wind tunnel, it is necessary to compensate for its vertical position and longitudinal position. By using active position compensation based on geometric relationships, it is ensured that the rotor hub center is always precisely located in the central region of the wind tunnel core flow field at different tilt angles. S4. Tilter rotor wind tunnel test: S41. Tilt rotor tilts to initial angle; S42. The rotor maintains a small collective pitch as it rotates to the rated speed. The wind tunnel starts to blow. During the wind blowing process, the trim program is activated. The initial thrust is set to ensure that the rotor is always under positive thrust during the wind blowing process until the wind speed reaches the target wind speed. Then, the rotor is re-trimmed to the specified thrust coefficient state, while ensuring that the pitching moment and roll moment are controlled within ±50Nm. S43. After balancing and stabilizing, aerodynamic data is collected for 80 revolutions, with 64 points per revolution. The six-component aerodynamic load and rotor torque of the rotor balance are obtained by Fourier transform. S44. Change the tensile coefficient and repeat step S43; S45. Change the wind speed and repeat steps S42-S44 until all test states for the current tilt angle are completed; S46. Change the rotor shaft tilt angle, and repeat S3, S42, S43, S44, and S45 until all tilt angle states are completed.

2. The wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform for a 4-meter-scale rotor, as described in claim 1, is characterized in that... Vertical position compensation as described in S3: When the fixed-wing mode tilts to the helicopter mode, that is, when the rotor shaft pitches up, the rotor hub center rises; at this time, a height block (5) is inserted between the four-degree-of-freedom support platform and the wind tunnel to perform upward compensation. The compensation height h is determined by the following formula: ； Where θ is the rotor shaft tilt angle; Conversely, when tilting from helicopter mode to fixed-wing mode, i.e., when the rotor shaft pitches down, the rotor hub center lowers; at this time, the height block (5) is removed, and the compensation height h is determined by the following formula: 。 3. The wind tunnel tilt rotor test method based on a four-degree-of-freedom support platform for a 4-meter-scale rotor, as described in claim 2, is characterized in that... The longitudinal position compensation described in S3: When the helicopter mode is tilted to the fixed-wing mode, the rotor hub center moves towards the wind tunnel nozzle position along the airflow direction; at this time, compensation is performed backward along the airflow direction through the airflow direction moving mechanism (3) of the four-degree-of-freedom support platform, and the compensation distance d is determined by the following formula: ； Conversely, when the fixed-wing mode tilts to the helicopter mode, the rotor hub center moves towards the wind tunnel inlet along the airflow direction; at this time, compensation is performed forward along the airflow direction through the airflow direction moving mechanism (3) of the four-degree-of-freedom support platform, and the compensation distance d is determined by the following formula: 。

Images