Rotor aerodynamic performance improvement wind tunnel test method based on active gurney flap control

Abstract

The invention discloses a rotor aerodynamic performance improvement wind tunnel test method based on active gurney flap control, and belongs to the technical field of active control of aircrafts. The problem that in a traditional rotor active control method in the prior art, when a gurney flap oscillates at the frequency of 1 ohm, the tension coefficient of a rotor is affected is solved. The method comprises the following steps: carrying out dynamic characteristic test on a rotor test bed, and carrying out control matrix calibration on the rotor test bed to obtain the rotor test bed meeting requirements; rotor wing dynamic balance and rotor wing common taper measurement are carried out on a rotor wing model, the obtained rotor wing model meeting the requirement is subjected to a Gurney flap active control test, rotor wing aerodynamic force under all set conditions is obtained and subjected to data processing, and according to the processed data, vibration characteristics and aerodynamic performance of the rotor wing in different working states are obtained through analysis. According to the method, the rotor performance is effectively improved, the influence on rotor control is avoided, and the method can be applied to active gurney flap control rotor performance research.

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 such as 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, 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 adapt to 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, active 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, high reliability, etc.

[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. The active control method aimed 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 active Gurney flap control for rotor lift enhancement. However, no active control test aimed 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 overview 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 overview is not an exhaustive overview 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 to be discussed later.

[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, 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: S1. Conduct a dynamic characteristic test 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 realize the real-time feedback of the pitch angle during blade rotation; S3. Set the dynamic balance requirement, adjust the dynamic balance of the rotor model until the dynamic balance requirement is met; S4. Set the coning measurement requirement, measure and adjust the coning of the rotor model until the coning measurement requirement is met; S5. Conduct an active control test on the Gurney flap for 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.

[0009] 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.

[0010] 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.

[0011] Further, in the step S4, the coning angle of the rotor model is measured at the working rotational 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, adjust by finely tuning the length of the pitch link until the coning angle measurement requirement is met.

[0012] Further, in the step S5, the following steps are included: S51. The inclination angle of the main shaft 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 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, the rotor thrust, pitching moment, rolling 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 active control program of the Gurney flap, and give the preset telescopic frequency, maximum extension amplitude and initial telescopic phase of the Gurney flap. S55. Conduct control over the frequency, amplitude and phase of the Gurney flap. In the step S55, the control sequence of the frequency, amplitude and phase of the Gurney flap is as follows: S551. Fix the dynamic telescopic frequency of the Gurney flap at 1Ω. S552. Fix the telescopic frequency and amplitude of the Gurney flap, conduct a phase sweep analysis, and determine the optimal initial telescopic phase. S553. Fix the telescopic frequency and initial phase of the Gurney flap, conduct an amplitude sweep analysis, and determine the optimal telescopic 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 force. 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 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 force under all set conditions is obtained.

[0013] Further, in the step S6, during the process of collecting the rotor aerodynamic force, 80 circles of raw data are collected, averaged into 8 circles, then FFT transformation and calculation are carried out to obtain the 0-8th harmonic components of the rotor rotation frequency, that is, the processed data.

[0014] The beneficial effects of the present invention are as follows: Based on a single-rotor test rig with a 4-meter diameter and the closed test section of an 8-meter large-scale low-speed return wind tunnel, the present invention proposes a wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control, and illustrates a complete set of test procedures from the dynamic characteristic test of the rotor test rig, 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 for controlling 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

[0015] The drawings described herein are used to provide a further understanding of the present invention and constitute 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 of the present invention. In the drawings: Figure 1 It is a flowchart of a wind tunnel test method for improving the aerodynamic performance of a rotor based on Gurney flap control; Figure 2 It is a flowchart of an embodiment of a wind tunnel test method for improving the aerodynamic performance of a rotor based on Gurney flap control; Figure 3 It is a schematic diagram of an active Gurney flap control wind tunnel test; Figure 4 It is a side view of an active Gurney flap control wind tunnel test; Figure 5 It is a front view of an active Gurney flap control wind tunnel test; Figure 6 It is a schematic diagram of the overall blade with active Gurney flap control; Figure 7 It is a front view of the blade with active Gurney flap control; Figure 8 It is a side view of the blade with active Gurney flap control.

[0016] Reference numerals: 1. reference blade; 2. Gurney flap; 3. rotor test rig; 4. rotor model. Detailed Embodiment

[0017] In order to make the technical solutions and advantages in the embodiments of the present invention clearer and more understandable, the following further details the exemplary embodiments of the present invention with reference to the 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.

[0018] Reference Figures 1-7 The present embodiment is described in detail. A wind tunnel test method for improving the aerodynamic performance of a rotor based on active Gurney flap control specifically 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, establish 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.

[0019] 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, and achieve rotor control, so as to achieve real-time feedback of the pitch angle during blade rotation.

[0020] 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 mode 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, and the test is completed; 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 operating speed should be avoided, and a certain resonance stability margin should be reserved to prevent resonance.

[0021] Further, in 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 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; Specifically, the dynamic balance of the rotor directly affects the vibration characteristics of the rotor test bench under the working condition, and is one of the direct factors affecting the test safety and data quality.

[0022] Further, in step S4, measure the coning angle of the rotor model at the operating rotational speed of the rotor, and make the height difference between the blades of the rotor model 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; Specifically, the coning angle is a concentrated manifestation of the balance of the inertial forces and aerodynamic forces of each rotor blade.

[0023] Further, step S5 includes the following steps: S51. The inclination angle of the main shaft 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; S52. Collect the zero point of the Gurney flap control system; S53. Under the condition that the total rotor pitch is 2°, increase the rotor speed to the operating speed. After the rotor speed is stable, start the wind tunnel. During the process, monitor parameters such as rotor thrust, pitching moment, rolling moment, torque, and vibration in real time; S54. After reaching the specified wind speed, start the trimming program. After trimming to the specified thrust coefficient, start the active control program of the Gurney flap, and give the preset Gurney flap telescopic frequency, maximum extension amplitude, and initial telescopic phase; S55. Perform control of the Gurney flap frequency, amplitude, and phase; In step S55, the control sequence of the Gurney flap frequency, amplitude, and phase is as follows: S551. Fix the dynamic telescopic frequency of the Gurney flap at 1Ω; S552. Fix the telescopic frequency and amplitude of the Gurney flap, conduct a phase sweep analysis, and determine the optimal initial telescopic phase; S553. Fix the telescopic frequency and initial phase of the Gurney flap, conduct an amplitude sweep analysis, and determine the optimal telescopic 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 force; 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 tunnel. During this period, the total rotor pitch is reduced to 2°, the cyclic pitch is reduced to 0°, and after the wind speed stabilizes, the rotor test bench stops rotating, and the rotor aerodynamic force under all set conditions is obtained; Specifically, in step S54, the specified trimming thrust coefficient is 0.008 - 0.02, and at the same time, the trimmed pitching moment and rolling moment are within ±10 Nm; In the above S551, the flapping frequency of the Gurney flap is 1Ω, and the maximum extension 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, that is, the initial flapping phase of the Gurney flap, starts to flap when the blade of the rotor model is at the azimuth angle from 0° to 360°, and the phase is swept at an interval of 30° for control; In the above S552, during the process of carrying out the phase sweep analysis, the initial flapping phase of the Gurney flap is identified by the way of external clock synchronization triggering. The trigger pulse signal is generated by the photoelectric encoder. The encoder simultaneously generates 3 kinds of TTL square wave pulses. The angular pulse Z with 1 position per revolution defines the starting point of one circle of data, the azimuth angle pulse A with 1024 - 4096 positions per revolution, and the azimuth angle pulse B with 1024 - 4096 positions per revolution. And the azimuth angle pulse A and the azimuth angle pulse B differ by 90°. Triggering is carried out at each rising edge of the azimuth angle pulse A and the azimuth angle pulse B to identify the azimuth angle signal of the blade, which is used to define the initial flapping phase of the Gurney flap; In the above S553, during the process of carrying out the amplitude sweep analysis, the initial extension position of the Gurney flap is controlled by the above phase sweep analysis result. Taking the Gurney flap starting to extend at the azimuth angle of 90° as an example, assuming that the Gurney flap unfolds in a sine manner, the Gurney flap reaches the maximum extension amount when the blade moves to the azimuth angle of 270°. The maximum extension amplitude of the Gurney flap is controlled by the driver. When the maximum extension 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. When the rotor performance improvement is the most obvious, it is the optimal extension amplitude; In the above S56, after the Gurney flap control system is stable, the trimming program is started again. When the Gurney flap dynamically flaps 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 is turned on 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.

[0024] Furthermore, in the above S6, during the process of collecting the rotor aerodynamic force, 80 circles of original data are collected, averaged into 8 circles, and then FFT transformation and calculation are carried out to obtain the 0 - 8th harmonic components of the rotor rotation frequency, that is, the processed data.

[0025] Although the present invention has been described in terms of a limited number of embodiments, those skilled in the art, having the benefit of the foregoing description, will appreciate that other embodiments can be contemplated within the scope of the invention as thus described. Additionally, it should be noted that the language used in this specification has been principally selected for readability and instructional purposes and not to limit or define the inventive subject matter. Accordingly, many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the appended claims. For the scope of the present invention, the disclosure herein is illustrative and not restrictive, and the scope of the invention is defined by the appended claims.

Claims

1. A wind tunnel test method for improving rotor aerodynamic performance based on active Gurney flap control, characterized in that: The following steps are involved: S1. Conduct dynamic characteristics test of the rotor test bench to ensure that the rotor test bench will not resonate at the rotor operating speed; S2. Calibrate the control matrix on the rotor test bench to build the conversion relationship between the blade angle and the rotor control actuator to achieve real-time feedback of the pitch angle when the blade rotates; S3. Set the dynamic balance requirement and adjust the rotor dynamic balance of the rotor model until the dynamic balance requirement is met; S4. Set the common taper measurement requirements, perform rotor common taper measurement on the rotor model and adjust it until the common taper measurement requirements are met; S5. Conduct a Gurney flap active control test on the rotor test bench and rotor model that meet the requirements to obtain the rotor aerodynamic force under all settings; S6. Perform data processing on the rotor aerodynamic force under all setting conditions, and analyze the vibration characteristics and aerodynamic performance of the rotor under different working conditions based on the processed data.

2. A wind tunnel test method for improving rotor aerodynamic performance based on active Gurney flap control according to claim 1, characterized in that: In S1, a vibration exciter is used to excite the rotor test bench, an acceleration sensor is used to collect vibration signals of the rotor, an LMS analysis system is used to identify the vibration mode of the rotor test bench, and the rotor test bench stiffness device is adjusted to further adjust the dynamic characteristics of the rotor test bench until no resonance occurs at the operating speed of the rotor, thereby completing the test.

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

4. A wind tunnel test method for improving rotor aerodynamic performance based on active Gurney flap control according to claim 3, characterized in that: In S4, the common taper 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 the thickness of the blade. If it is not satisfied, it is adjusted by fine-tuning the length of the variable pitch pull rod until the common taper measurement requirement is met.

5. A wind tunnel test method for improving rotor aerodynamic performance based on active Gurney flap control according to claim 4, characterized in that: The S5 comprises the following steps: S51. The spindle inclination angle changes from -8° to 8°, and the initial reading of the angle of attack is collected; S52. Collect the zero point of the Gurney flap control system; S53. Raise the rotor speed to the operating speed when the rotor collective pitch is 2°. After the rotor speed stabilizes, start the wind tunnel. During the process, monitor the rotor thrust, pitch moment, roll moment, torque and vibration parameters in real time. S54. After reaching the specified wind speed, start the trimming program, and after trimming to the specified tension coefficient, start the Gurney flap active control program, and set the preset Gurney flap extension and retraction frequency, maximum extension amplitude, and initial extension and retraction phase; S55. Perform Gurney flap frequency, amplitude and phase control; In S55, the control sequence of the Gurney flap frequency, amplitude and phase control is as follows: S551. Fixed Gurney flap dynamic extension and retraction frequency to 1Ω; S552. Fix the Gurney flap extension and retraction frequency and amplitude, conduct phase sweep analysis, and determine the optimal initial extension and retraction phase; S553. Fix the Gurney flap extension and retraction frequency and initial phase, conduct sweep analysis, and determine the optimal extension and retraction amplitude; S56. After the Gurney flap control system is stabilized, the trimming procedure is started again, trimmed to the specified pull coefficient described in step S54, and the rotor aerodynamic force is collected; S57. Change the tension coefficient, repeat steps S54 to S56 until all tension coefficient states are completed; S58. Change the wind speed, repeat steps S54 to S57 until all wind speed states are completed; S59. Turn off the Gurney flap control program and stop the wind tunnel. During this period, the rotor collective pitch is reduced to 2° and the cyclic pitch is reduced to 0°. After the wind speed stabilizes, the rotor test bench is stopped to obtain the rotor aerodynamic force under all setting conditions.

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

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