Wind Tunnel Test Method for Improving Rotor Aerodynamic Performance Based on Active Gurney Flap Control

Abstract

The present invention discloses a wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control, belonging to the technical field of active control of aircraft. It solves the problem in the prior art that in the traditional rotor active control method, when the Gurney flap oscillates at a frequency of 1Ω, it will affect the rotor thrust coefficient. The present invention conducts dynamic characteristic tests on the rotor test bench, calibrates the manipulation matrix on the rotor test bench, and obtains a rotor test bench that meets the requirements; through rotor dynamic balance and rotor coning measurement of the rotor model, a rotor model that meets the requirements is used for Gurney flap active control tests, and the rotor aerodynamic forces under all set conditions are obtained for data processing. According to the processed data, the vibration characteristics and aerodynamic performance of the rotor under different working conditions are analyzed. The present invention effectively improves the rotor performance, avoids affecting the rotor control, and can be applied to the research on the performance of rotors controlled by active Gurney flaps.

Description

Technical Field

[0001] The present invention relates to a wind tunnel test method for improving the aerodynamic performance of a rotor, and particularly to a wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control, belonging to the field of active control technology for aircraft. Background Art

[0002] Due to its capabilities of vertical takeoff and landing, hovering, strong terrain adaptability, and rapid response, helicopters have been widely used in both military and civilian fields such as battlefield reconnaissance, assault transportation, anti-submarine warfare, medical rescue, sightseeing tourism, and construction hoisting. With the development trend of modern helicopters towards high speed, environmental protection, and intelligence, higher requirements are put forward for improving the flight performance of helicopters, and helicopters are required to have higher flight efficiency, faster flight speed, and greater load limit.

[0003] Currently, active control technology and passive control technology have been proposed for the development of improving rotor performance. Compared with passive control technology, active control technology can dynamically adjust the blade angle of attack, deformation, or airflow distribution of the rotor according to the change of the helicopter flight state to meet the needs of different flight states and flight environments, thereby maximizing the rotor performance, and its operating frequency range is wider. Compared with rotor active control technologies such as variable rotor speed, variable rotor diameter, actively twisted rotor, and active trailing edge flap, the active Gurney flap has great advantages due to its simple structure, low design cost, small driving power, and high reliability.

[0004] In the prior art, the rotor active control technology is still in its infancy. Currently, only vibration and noise active control tests have been carried out on the trailing edge flap. However, when performing active noise reduction or active vibration reduction control, the trailing edge flap is controlled at a frequency of (N±1)Ω of the blade number N of the rotor blade, where Ω is the operating speed of the rotor. The high-frequency oscillation of the trailing edge flap will not affect the handling characteristics of the rotor. While the active control method aiming at improving rotor performance is controlled at an oscillation frequency of 1Ω, which will not only affect the handling of the rotor but also affect the trim of the rotor. It is more complex and more dangerous. Conducting wind tunnel tests is one of the most effective means to study the improvement of rotor performance by active Gurney flaps. Wind tunnel tests have more stable test conditions, lower costs, controllable and repeatable test states compared with flight tests, and are the most ideal method to explore the mechanism of lift enhancement of rotors controlled by active Gurney flaps. However, no active control test aiming at improving the performance of Gurney flap rotors has been carried out yet.

[0005] In summary, a wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control is needed to provide test data and technical support for the development of active Gurney flap control technology. Summary of the Invention

[0006] A brief summary of the present invention is given below to provide a basic understanding of certain aspects of the present invention. It should be understood that this summary is not an exhaustive summary of the present invention. It is not intended to identify the key or important parts of the present invention, nor is it intended to limit the scope of the present invention. Its purpose is merely to present certain concepts in a simplified form as a prelude to the more detailed description that follows.

[0007] In view of this, to solve the problem in the traditional active control method of a rotor that when the Gurney flap oscillates at a frequency of 1Ω, it will affect the rotor thrust coefficient in the prior art, the present invention provides a wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control.

[0008] The technical solution is as follows: A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control includes the following steps:

[0009] S1. Conduct dynamic characteristic tests on the rotor test bench to ensure that the rotor test bench does not resonate at the rotor operating speed.

[0010] S2. Calibrate the control matrix on the rotor test bench, establish the conversion relationship between the blade angle and the rotor control actuator, and realize the real-time feedback of the pitch angle during blade rotation.

[0011] S3. Set the dynamic balance requirements, adjust the dynamic balance of the rotor model until the dynamic balance requirements are met.

[0012] S4. Set the coning measurement requirements, measure and adjust the coning of the rotor model until the coning measurement requirements are met.

[0013] S5. Conduct active Gurney flap control tests on the obtained rotor test bench and rotor model that meet the requirements to obtain the rotor aerodynamic forces under all set conditions.

[0014] S6. Process the data of the rotor aerodynamic forces under all set conditions, and analyze the vibration characteristics and aerodynamic performance of the rotor under different operating conditions based on the processed data.

[0015] Further, in S1, an exciter is used to excite the rotor test bench, an acceleration sensor is used to collect the vibration signals of the rotor, an LMS analysis system is used to identify the vibration modes of the rotor test bench, and the dynamic characteristics of the rotor test bench are adjusted by adjusting the stiffness device of the rotor test bench until resonance does not occur at the rotor operating speed, thus completing the test.

[0016] Further, in S3, for the rotor model, the dynamic balance requirement is that the dynamic balance amount of the rotor test bench is guaranteed to be less than the set value at the operating speed. If not satisfied, it is adjusted by increasing or decreasing the counterweight of the hub arm until the dynamic balance requirement is met.

[0017] Further, in step S4, the coning angle of the rotor model is measured at the operating rotational speed of the rotor, such that the height difference between the blades of the rotor model is less than half of the blade thickness. If not satisfied, adjust by finely tuning the length of the pitch link until the coning angle measurement requirements are met.

[0018] Further, step S5 includes the following steps:

[0019] S51. The spindle inclination angle changes from -8° to 8°, and the initial angle of attack reading is collected.

[0020] S52. The zero point of the Gurney flap control system is collected.

[0021] S53. With the total rotor pitch at 2°, the rotor speed is increased to the operating speed. After the rotor speed stabilizes, the wind tunnel starts to blow. During the process, the rotor thrust, pitching moment, rolling moment, torque, and vibration parameters are monitored in real time.

[0022] S54. After reaching the specified wind speed, the trimming program is started. After trimming to the specified thrust coefficient, the active control program of the Gurney flap is started, and the preset telescopic frequency, maximum extension amplitude, and initial telescopic phase of the Gurney flap are given.

[0023] S55. Control the frequency, amplitude, and phase of the Gurney flap.

[0024] In step S55, the control sequence of the frequency, amplitude, and phase of the Gurney flap is as follows:

[0025] S551. Fix the dynamic telescopic frequency of the Gurney flap at 1Ω.

[0026] S552. Fix the telescopic frequency and amplitude of the Gurney flap, conduct a phase sweep analysis, and determine the optimal initial telescopic phase.

[0027] S553. Fix the telescopic frequency and initial phase of the Gurney flap, conduct an amplitude sweep analysis, and determine the optimal telescopic amplitude.

[0028] S56. After the Gurney flap control system stabilizes, start the trimming program again, trim to the specified thrust coefficient in step S54, and collect the rotor aerodynamic force.

[0029] S57. Change the thrust coefficient, and repeat steps S54 to S56 until all thrust coefficient states are completed.

[0030] S58. Change the wind speed, and repeat steps S54 to S57 until all wind speed states are completed.

[0031] S59. Close the Gurney flap control program, stop the wind tunnel, during which the total rotor pitch is reduced to 2°, the cyclic pitch is reduced to 0°. After the wind speed stabilizes, the rotor test bench stops rotating, and the rotor aerodynamic forces under all set conditions are obtained.

[0032] Further, in step S6, during the process of collecting the rotor aerodynamic forces, 80 circles of raw data are collected, averaged into 8 circles, and then subjected to FFT transformation and calculation to obtain the 0-8th harmonic components of the rotor rotation frequency, i.e., the processed data.

[0033] The beneficial effects of the present invention are as follows: Based on a 4-meter diameter single-rotor test bench and an 8-meter large-scale low-speed return-flow wind tunnel closed test section, the present invention proposes a wind tunnel test method for improving the rotor aerodynamic performance based on active Gurney flap control, and illustrates a complete set of test processes from the dynamic characteristic test of the rotor test bench, blade matrix calibration, dynamic balance adjustment, coning adjustment to the active control test process of the Gurney flap and then to the test data processing; the present invention identifies the blade azimuth angle signal by means of external clock synchronization triggering, and controls the Gurney flap signal according to the blade azimuth angle to control the initial telescopic phase of the Gurney flap; the present invention proposes a method for re-trimming after activating the active control of the Gurney flap. When aiming to improve the rotor performance, the control method of the Gurney flap described in the present invention ensures that the test can be carried out efficiently and safely. Description of the Drawings

[0034] The drawings described herein are used to provide a further understanding of the present invention and form a part of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0035] Figure 1 is a flowchart of a wind tunnel test method for improving the rotor aerodynamic performance based on Gurney flap control;

[0036] Figure 2 is a flowchart of an embodiment of a wind tunnel test method for improving the rotor aerodynamic performance based on Gurney flap control;

[0037] Figure 3 is a schematic diagram of an active Gurney flap control wind tunnel test;

[0038] Figure 4 is a side view of an active Gurney flap control wind tunnel test;

[0039] Figure 5 is a front view of an active Gurney flap control wind tunnel test;

[0040] Figure 6 is a schematic diagram of the overall blade of an active Gurney flap control;

[0041] Figure 7Front view of the blade with active Gurney flap control

[0042] Figure 8 Side view of the blade with active Gurney flap control

[0043] Reference numerals: 1. Reference blade; 2. Gurney flap; 3. Rotor test bench; 4. Rotor model Detailed implementation mode

[0044] In order to make the technical solutions and advantages in the embodiments of the present invention clearer and more understandable, the following further describes the exemplary embodiments of the present invention in detail with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than an exhaustive list of all embodiments. It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments can be combined with each other

[0045] Refer to Figures 1-7 This embodiment is described in detail. The wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control specifically includes the following steps

[0046] S1. Conduct dynamic characteristic tests on the rotor test bench to ensure that resonance does not occur on the rotor test bench at the rotor operating speed

[0047] S2. Calibrate the control matrix on the rotor test bench, establish the conversion relationship between the blade angle and the rotor control actuator, and realize the real-time feedback of the pitch angle during blade rotation

[0048] S3. Set the dynamic balance requirements, adjust the rotor dynamic balance of the rotor model until the dynamic balance requirements are met

[0049] S4. Set the coning measurement requirements, measure and adjust the rotor coning of the rotor model until the coning measurement requirements are met

[0050] S5. Conduct active Gurney flap control tests on the obtained rotor test bench and rotor model that meet the requirements to obtain the rotor aerodynamic forces under all set conditions

[0051] S6. Process the data of the rotor aerodynamic forces under all set conditions, and analyze the vibration characteristics and aerodynamic performance of the rotor under different operating conditions based on the processed data

[0052] Specifically, in step S2, the pitch of the rotor blade is a function of the collective pitch, cyclic pitch, and blade azimuth angle. It is necessary to establish the conversion relationship between the blade angle and the rotor control actuator, establish the control matrix, realize the rotor control, and then realize the real-time feedback of the pitch angle during blade rotation

[0053] Further, in step S1, an exciter is used to excite the rotor test bench, an acceleration sensor is used to collect the vibration signals of the rotor, and an LMS analysis system is used to identify the vibration modes of the rotor test bench. By adjusting the stiffness device of the rotor test bench, the dynamic characteristics of the rotor test bench are further adjusted until resonance does not occur at the working speed of the rotor, and the test is completed;

[0054] Specifically, during the dynamic characteristic test of the rotor test bench, the coincidence between the natural frequency of the rotor test bench and the multiple frequency of the rotor working speed should be avoided, and a certain resonance stability margin should be reserved to prevent resonance from occurring.

[0055] Further, in step S3, for a rotor model with a diameter of 4 meters, the dynamic balance requirement is that the dynamic balance amount of the rotor test bench is less than the set value, that is, 0.2 IPS, at the working speed. If not satisfied, it is adjusted by increasing or decreasing the counterweight of the hub support arm until the dynamic balance requirement is met;

[0056] Specifically, the dynamic balance of the rotor directly affects the vibration characteristics of the rotor test bench under the working state, and is one of the direct factors affecting the test safety and data quality.

[0057] Further, in step S4, the coning angle of the rotor model is measured at the working speed of the rotor, so that the height difference between the blades of the rotor model is less than half of the blade thickness. If not satisfied, it is adjusted by finely tuning the length of the pitch link until the coning angle measurement requirement is met;

[0058] Specifically, the coning angle is a concentrated manifestation of the balance of the inertial forces and aerodynamic forces of each rotor blade.

[0059] Further, step S5 includes the following steps:

[0060] S51. The spindle inclination angle changes from -8° to 8°, and the initial angle of attack reading is collected. The initial angle of attack reading is used to deduct the influence of the self-weight of the hub and blades;

[0061] S52. Collect the zero point of the Gurney flap control system;

[0062] S53. Under the state that the total rotor pitch is 2°, the rotor speed is increased to the working speed. After the rotor speed is stable, the wind tunnel starts to blow. During the process, parameters such as rotor thrust, pitching moment, rolling moment, torque and vibration are monitored in real time;

[0063] S54. After reaching the specified wind speed, the trimming program is started. After trimming to the specified thrust coefficient, the Gurney flap active control program is started, and the preset Gurney flap retraction / extension frequency, maximum extension amplitude and initial retraction / extension phase are given;

[0064] S55. Perform Gurney flap frequency, amplitude and phase control;

[0065] In S55, the control sequence for the Gurney flap frequency, amplitude, and phase is as follows:

[0066] S551. Fix the dynamic telescopic frequency of the Gurney flap at 1Ω;

[0067] S552. Fix the telescopic frequency and amplitude of the Gurney flap, conduct a phase sweep analysis, and determine the optimal initial telescopic phase;

[0068] S553. Fix the telescopic frequency and initial phase of the Gurney flap, conduct an amplitude sweep analysis, and determine the optimal telescopic amplitude;

[0069] S56. After the Gurney flap control system stabilizes, restart the trimming program, trim to the specified thrust coefficient described in step S54, and collect the rotor aerodynamic forces;

[0070] S57. Change the thrust coefficient, and repeat steps S54 to S56 until all thrust coefficient states are completed;

[0071] S58. Change the wind speed, and repeat steps S54 to S57 until all wind speed states are completed;

[0072] S59. Turn off the Gurney flap control program, stop the wind in the wind tunnel. During this period, the total rotor pitch is reduced to 2°, the cyclic pitch is reduced to 0°. After the wind speed stabilizes, the rotor test bench stops rotating, and the rotor aerodynamic forces under all set conditions are obtained;

[0073] Specifically, in S54, the specified trimming thrust coefficient is 0.008 - 0.02, and at the same time, the trimmed pitch moment and roll moment are within ±10 Nm;

[0074] In S551, the telescopic frequency of the Gurney flap is 1Ω, and the maximum extended amplitudes of the Gurney flap are 1%c, 2%c, and 3%c, where c represents the blade chord length. The phase control of the Gurney flap, i.e., the initial telescopic phase of the Gurney flap, starts to extend and retract when the blade of the rotor model is at azimuth angles of 0° to 360°, and a phase sweep control is performed at intervals of 30°;

[0075] In S552, during the process of conducting the phase sweep analysis, the initial telescopic phase of the Gurney flap is identified by the method of external clock synchronization triggering. The trigger pulse signal is generated by an optical encoder. The encoder simultaneously generates 3 types of TTL square wave pulses, the angular pulse Z that positions once per revolution defines the starting point of a circle of data, the azimuth angle pulses A that are 1024 - 4096 times per revolution, and the azimuth angle pulses B that are 1024 - 4096 times per revolution. Moreover, the azimuth angle pulses A and B differ by 90°. Triggering is performed at each rising edge of the azimuth angle pulses A and B to identify the azimuth angle signal of the blade, which is used to define the initial telescopic phase of the Gurney flap;

[0076] In the above S553, during the process of conducting the sweep analysis, the initial extended position of the Gurney flap is controlled by the above-mentioned phase sweep analysis result. Taking the example that the Gurney flap starts to extend at the azimuth angle of 90°, assuming that the Gurney flap unfolds in a sine manner, the Gurney flap reaches the maximum extended amount when the blade moves to the azimuth angle of 270°. The maximum extended amplitude of the Gurney flap is controlled by the actuator. When the maximum extended amplitudes of the Gurney flap are 1%c, 2%c, and 3%c respectively, parameters such as the rotor thrust, drag, and torque are measured. The optimal telescopic amplitude is the one when the rotor performance improvement is the most obvious;

[0077] In the above S56, after the Gurney flap control system is stable, the trimming program is started again. When the Gurney flap performs dynamic telescoping at a frequency of 1Ω, it will cause a change in the rotor thrust coefficient. In order to compare the performance changes before and after the active control of the Gurney flap under the same thrust coefficient, the trimming program needs to be started again to re-trim the rotor thrust coefficient to the given thrust coefficient value before the active control of the Gurney flap is turned on.

[0078] Furthermore, in the above S6, during the process of collecting the rotor aerodynamic force, 80 circles of raw data are collected, averaged into 8 circles, and then FFT transformation and calculation are performed to obtain the 0-8th harmonic components of the rotor rotation frequency, that is, the processed data.

[0079] Although the present invention has been described based on a limited number of embodiments, those skilled in the art in this technical field will understand that other embodiments can be envisioned within the scope of the present invention thus described. In addition, it should be noted that the language used in this specification is mainly selected for readability and teaching purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention. Therefore, many modifications and changes are obvious to those of ordinary skill in this technical field without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure of the present invention is illustrative rather than restrictive, and the scope of the present invention is defined by the appended claims.

Claims

1. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control, characterized in that, It includes the following steps: S1. Conduct dynamic characteristic tests on the rotor test bench to ensure that the rotor test bench does not resonate at the rotor operating speed; S2. Calibrate the control matrix on the rotor test bench, construct the conversion relationship between the blade angle and the rotor control actuator, and achieve real-time feedback of the pitch angle during blade rotation; S3. Set the dynamic balance requirements, adjust the dynamic balance of the rotor model until the dynamic balance requirements are met; S4. Set the coning measurement requirements, measure and adjust the coning of the rotor model until the coning measurement requirements are met; S5. Conduct Gurney flap active control tests on the obtained rotor test bench and rotor model that meet the requirements to obtain the rotor aerodynamic forces under all set conditions; S6. Process the data of the rotor aerodynamic forces under all set conditions, and analyze and obtain the vibration characteristics and aerodynamic performance of the rotor under different operating conditions based on the processed data.

2. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control according to claim 1, characterized in that In the above S1, an exciter is used to excite the rotor test bench, an acceleration sensor is used to collect the vibration signals of the rotor, and an LMS analysis system is used to identify the vibration modes of the rotor test bench. By adjusting the stiffness device of the rotor test bench, the dynamic characteristics of the rotor test bench are further adjusted until resonance does not occur at the rotor operating speed, and the test is completed.

3. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control according to claim 2, characterized in that, In the above S3, for the rotor model, the dynamic balance requirement is that the dynamic balance amount of the rotor test bench is less than the set value at the operating speed. If not satisfied, it is adjusted by increasing or decreasing the weights on the hub struts until the dynamic balance requirements are met.

4. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control according to claim 3, characterized in that, In the above S4, the coning of the rotor model is measured at the rotor operating speed, so that the height difference between the blades of the rotor model is less than half of the blade thickness. If not satisfied, it is adjusted by finely tuning the length of the pitch link until the coning measurement requirements are met.

5. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control according to claim 4, characterized in that, In the above S5, it includes the following steps: S51. The main shaft inclination angle changes from -8° to 8°, and the initial reading of the angle of attack is collected; S52. The zero point of the Gurney flap control system is collected; S53. Under the condition that the total rotor pitch is 2°, the rotor speed is increased to the operating speed. After the rotor speed is stable, the wind tunnel starts to blow. During the process, the rotor thrust, pitch moment, roll moment, torque and vibration parameters are monitored in real time; S54. After reaching the specified wind speed, start the trimming program. After trimming to the specified thrust coefficient, start the Gurney flap active control program, and give the preset Gurney flap retraction / extension frequency, maximum extension amplitude and initial retraction / extension phase; S55. Conduct Gurney flap frequency, amplitude and phase control; In the above S55, the control sequence of the Gurney flap frequency, amplitude and phase control is as follows: S551. Fix the dynamic retraction / extension frequency of the Gurney flap at 1Ω; S552. Fix the retraction / extension frequency and amplitude of the Gurney flap, conduct a phase sweep analysis to determine the optimal initial retraction / extension phase; S553. Fix the retraction / extension frequency and initial phase of the Gurney flap, conduct an amplitude sweep analysis to determine the optimal retraction / extension amplitude; S56. After the Gurney flap control system is stable, start the trimming program again, trim to the specified thrust coefficient in step S54, and collect the rotor aerodynamic forces; S57. Change the thrust coefficient, and repeat steps S54 to S56 until all thrust coefficient states are completed. S58. Change the wind speed and repeat steps S54 to S57 until all wind speed states are completed; S59. Turn off the Gurney flap control program, stop the wind in the wind tunnel. During this period, the total rotor pitch is reduced to 2°, the cyclic pitch is reduced to 0°. After the wind speed stabilizes, the rotor test bench stops rotating, and the rotor aerodynamic forces under all set conditions are obtained.

6. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control according to claim 5, characterized in that In step S6, during the process of collecting the rotor aerodynamic forces, 80 circles of original data are collected, averaged into 8 circles, and then FFT transformation and calculation are performed to obtain the 0-8th harmonic components of the rotor rotation frequency, that is, the processed data.

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