A wind tunnel test model device for measuring unsteady dynamic loads on propellers

Abstract

The present invention relates to a wind tunnel test model device for measuring unsteady dynamic loads on propellers. This device, which belongs to the technical field of propeller wind tunnel testing, addresses the problems of existing wind tunnel test models, such as their inability to measure dynamic loads, inaccurate measurement results, and inability to quickly and accurately achieve specific vibration frequencies and amplitudes. The wind tunnel test model device of the present invention includes a motor, a six-component force balance, a T-shaped support rod, a vibration mechanism, and a bracket; the device of the present invention improves the accuracy of test results.

Description

Technical Field

[0001] The invention belongs to the field of propeller wind tunnel tests, and in particular relates to a wind tunnel test model device for measuring unsteady dynamic loads on a propeller. Background Art

[0002] Modern aircraft design often requires wind tunnel testing to simulate the aircraft's flight conditions in the atmosphere and verify that the design meets requirements. Wind tunnel testing, based on the principle of relativity of motion, involves fixing an aircraft model in a wind tunnel and artificially creating airflow to simulate flight. Despite the rapid development of computational fluid dynamics (CFD), wind tunnel testing remains an essential and irreplaceable analytical method in aircraft design.

[0003] Propeller aircraft have many advantages, such as high thrust and high fuel efficiency, and are widely used in modern regional airliners, military transport aircraft, general aviation, and other fields. During flight, the magnitude and direction of propeller thrust and torque, affected by wing vibration, change periodically with the movement, causing significant changes in the aircraft's lift-drag characteristics, controllability, and stability, which has a significant impact on the aircraft's flight safety. This is an important direction in the study of unsteady aerodynamic loads on propeller aircraft and a key issue in the overall design of aircraft. Therefore, accurate measurement of the unsteady loads generated by the propeller is necessary. Aircraft propeller wind tunnel testing is mainly aimed at obtaining the dynamic unsteady aerodynamic loads generated by the propeller in the airflow due to the vibration of the elastic wing, providing reliable test data for the overall design of propeller aircraft, aerodynamic characteristics prediction, and flight performance evaluation.

[0004] However, the propeller wind tunnel test models in the existing technology mainly focus on the steady propeller loads and the aerodynamic problems caused by them, and pay less attention to the unsteady dynamic loads, resulting in inaccurate test results. Summary of the Invention

[0005] In view of the above problems, the present invention provides a wind tunnel test model device for measuring the unsteady dynamic load of a propeller, which solves the problems that the existing wind tunnel test model cannot realize dynamic load measurement, the measurement results are inaccurate, and the specific vibration frequency and amplitude cannot be achieved quickly and accurately.

[0006] The present invention provides a wind tunnel test model device for measuring unsteady follower loads on a propeller, characterized in that it comprises a motor, a six-component force balance, a T-shaped support rod, a vibration mechanism and a bracket;

[0007] The T-shaped support rod includes a horizontal rod and a vertical rod; the motor is connected to a six-component force balance;

[0008] The vibration mechanism includes an L-shaped connecting rod and a linear reciprocating servo. The linear reciprocating servo provides vibration power to drive the L-shaped connecting rod to move. The L-shaped connecting rod drives the T-shaped support rod.

[0009] The vertical rod of the T-shaped support rod and the linear reciprocating servo are installed on the bracket through a mounting seat.

[0010] Optionally, the front end and the rear end of the six-component force balance are both circular planes; the front end of the six-component force balance is connected to the motor, and the rear end is fixed to the horizontal rod.

[0011] Optionally, the L-shaped connecting rod includes a first connecting arm and a second connecting arm; a sliding groove is provided at one end of the first connecting arm, and the other end is connected to one end of the second connecting arm; the other end of the second connecting arm is connected to the vertical rod; the linear reciprocating servo includes a reciprocating drive end rod, one end of the reciprocating drive end rod is connected to the power source of the linear reciprocating servo, and the other end is inserted into the sliding groove of the L-shaped connecting rod through a pin.

[0012] Optionally, a linear reciprocating servo is mounted directly behind the T-shaped support rod.

[0013] Optionally, the outer diameter R2, inner diameter R3 and length L3 of the horizontal rod are set as follows:

[0014] 1 / E c =V f / E f +V m / E m

[0015] K=(E c *π / 64*(R2 4 –R3 4 )) / L3

[0016] Among them, E c is the elastic modulus of the horizontal rod made of carbon fiber; V f is the carbon fiber volume fraction of the horizontal rod made of carbon fiber; E f is the uniaxial elastic modulus of the horizontal rod made of carbon fiber; V m is the volume fraction of the horizontal rod made of carbon fiber; E m is the elastic modulus of the horizontal rod of carbon fiber material; K is the stiffness of the horizontal rod of carbon fiber material.

[0017] Compared with the prior art, the present invention has at least the following beneficial effects:

[0018] (1) The linear reciprocating servo of the test model device of the present invention receives computer control signals, which can more conveniently, quickly and accurately achieve a vibration frequency of 0 to 7 Hz and a vibration amplitude of ±5°, and realize real-time feedback of the actual vibration signal and the load measurement signal. The vibration frequency of 0 to 7 Hz is consistent with the vibration frequency of most wing structures, and can more realistically simulate the pitch motion of the propeller caused by wing vibration, help to better study the influence of elastic wing structure vibration on the aerodynamic characteristics of the propeller, explore the law of change of the propeller's unsteady dynamic aerodynamic load with the motion frequency, amplitude and relative position of the propeller / wing, and provide better data support for the design of propeller aircraft.

[0019] (2) The wind tunnel test model device of the present invention is used to simulate the unsteady dynamic loads generated by vibration. It simulates the propeller's tension, torque and other loads driven by the vibration of the wing, which change periodically with the propeller's pitch motion and become dynamic loads, thereby improving the accuracy of the test results. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] The drawings are only for purposes of illustrating particular embodiments and are not to be considered limiting of the invention.

[0021] Figure 1 is a schematic diagram of a wind tunnel test model apparatus of the present invention;

[0022] Figure 2 is a schematic diagram of the propeller and measuring mechanism of the present invention;

[0023] Figure 3 is a schematic diagram of a support rod of the present invention;

[0024] Figure 4 It is a schematic diagram of the vibration mechanism of the present invention.

[0025] Reference numerals:

[0026] 1. Propeller; 2. Motor; 3. Six-component force balance; 4. T-shaped support rod; 5. Linear reciprocating servo; 6. L-shaped connecting rod; 7. Bearing base; 8. Angle steel; 9. Adapter; 10. Wind tunnel support rod. DETAILED DESCRIPTION

[0027] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. In addition, the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0028] A specific embodiment of the present invention, as Figure 1-4 , discloses a wind tunnel test model device for measuring unsteady follow-up loads on a propeller, comprising a motor 2, a six-component force balance 3, a T-shaped support rod 4, a vibration mechanism and a bracket;

[0029] The T-shaped support rod 4 includes a horizontal rod and a vertical rod; the propeller 1 to be tested is set at one end of the horizontal rod through the motor 2; the motor 2 is connected to the six-component force balance 3; the front and rear ends of the six-component force balance 3 are both circular planes; the front end of the six-component force balance 3 is connected to the motor 2, and the rear end is fixed to the horizontal rod;

[0030] The vibration mechanism includes an L-shaped connecting rod 6 and a linear reciprocating servo 5; the L-shaped connecting rod 6 includes a first connecting arm and a second connecting arm; one end of the first connecting arm is provided with a sliding groove, and the other end is connected to one end of the second connecting arm; the other end of the second connecting arm is connected to a vertical rod; the length of the first connecting arm is L1, and the length of the second connecting arm is L2; ​​the linear reciprocating servo 5 includes a reciprocating drive end rod, and the maximum reciprocating stroke of the reciprocating drive end rod is S; one end of the reciprocating drive end rod is connected to the power source of the linear reciprocating servo, and the other end is inserted into the sliding groove of the L-shaped connecting rod 6 via a pin. The linear reciprocating servo provides the vibration power, driving the entire mechanism to move;

[0031] The vertical rod of the T-shaped support rod 4 and the linear reciprocating servo 5 are installed on the bracket through the mounting seat; the linear reciprocating servo 5 is installed directly behind the T-shaped support rod 4 to ensure the flow field quality of the wind tunnel test, avoid the servo from affecting the airflow around the propeller, and ensure that the wind tunnel test data is more accurate.

[0032] Optionally, the mounting seat for mounting the T-shaped support rod 4 is a bearing base 7 ; and the bracket is an angle steel 8 .

[0033] The motor and propeller of the wind tunnel test model device of the present invention can be replaced with different models according to the test requirements; a fairing is installed on the outside of the overall structure to avoid affecting the airflow; the T-shaped support rod also avoids the vibration of the dynamic mechanism affecting the wind tunnel flow field.

[0034] Optionally, the diameter of the circular planes at both ends of the six-component force balance is R1; four M4 threaded holes are set on both circular planes; the front end of the six-component force balance is connected to the motor through four screws; and the rear end is fixed to the horizontal rod through a flange.

[0035] Optionally, the horizontal rod is a carbon fiber tube with an outer diameter of R2 and an inner diameter of R3, which ensures that the overall structure has sufficient rigidity while reducing mass. The horizontal rod adopts a modular design, and carbon fiber tubes of different lengths L3 are selected according to the requirements of the wind tunnel test to simulate different installation positions of the propeller on the wing relative to the wing, and then measure the impact of different installation positions on the propeller's follow-up aerodynamic load. The front end of the horizontal rod is connected to the six-component force balance through a flange, and the tail is connected to the vertical rod through a T-sleeve; the vertical rod is a carbon fiber tube with an outer diameter of R4, an inner diameter of R5, and a length of L4, which can ensure that the overall structure is sufficiently stable; the tail of the vertical support rod is connected to the vibration mechanism, and the bottom is fixed to the bracket through a ball bearing.

[0036] Optionally, the outer diameter R2, inner diameter R3 and length L3 of the horizontal rod made of carbon fiber material are set as follows:

[0037] 1 / E c =V f / E f +V m / E m

[0038] K=(E c *π / 64*(R2 4 –R3 4 )) / L3

[0039] Among them, E c is the elastic modulus of the carbon fiber support rod material; V f is the volume fraction of carbon fiber in the support rod material; E f V is the uniaxial elastic modulus of carbon fiber; m is the volume fraction of the support rod material matrix; E m is the elastic modulus of the matrix; K is the stiffness of the support rod.

[0040] As a result, the horizontal rod can have both sufficiently large rigidity and sufficiently small mass, thus avoiding large deformation during vibration that affects data measurement.

[0041] Optionally, R1:R2:R3:R4:R5=21:15:13:15:13.

[0042] In order to ensure that the horizontal rod supports the six-component force balance stably enough, the dimensions of the horizontal rod and the six-component force balance satisfy the following relationship:

[0043] 4*R3 2 =π*R1 2 -π*R2 2

[0044] The diameter of the circular planes at both ends of the six-component force balance is R1 = 21 mm. According to the formula and subsequent test measurements, it is finally determined that R2 = 15 mm and R3 = 13 mm.

[0045] Designing R2=R4 and R3=R5 allows for modular assembly and reduced costs. The horizontal and vertical support rods can be made from the same material. The same inner and outer diameters also allow for quick assembly, saving time.

[0046] Optionally, L1≤S / 2tanα; wherein α is the maximum rotation angle of the lower T-shaped support rod 4 driven by the steering gear.

[0047] The values ​​of R1, R2, R3, R4, R5, S, α, and L1 selected for the test are 21 mm, 15 mm, 13 mm, 15 mm, and 13 mm, respectively.

[0048] To ensure the quality of the wind tunnel flow field and the accuracy of the test data, the vibration mechanism is installed directly behind the propeller bracket. L2 is determined based on the size of the mounting base and the linear reciprocating servo, and is ultimately selected as 180mm.

[0049] In order to simulate different installation positions of the propeller relative to the wing and measure the effect of different installation positions on the propeller's aerodynamic load, the length of the horizontal rod L3 can be designed to be different. The setting method of L3 is:

[0050] 1.2R≤L3≤2.5R;

[0051] Where R is the propeller radius;

[0052] Based on this, the range of L3 is 192mm to 400mm. To make the changes in the test data due to length changes more obvious, the length of different rods is changed by 50mm. Finally, L3 is selected as 230mm, 280mm, 330mm or 380mm.

[0053] Optionally, L4 ≥ 1.5R, so as to avoid interference with the propeller flow field and influence on the test data measurement.

[0054] According to the propeller radius R=160 mm selected in the test, L4≥240 mm. Considering the installation and processing requirements, preferably, L4 is 270 mm.

[0055] Preferably, R1 = 21mm, R2 = 15mm, R3 = 13mm, R4 = 15mm, R5 = 13mm, L1 = 120mm, L2 = 180mm, L3 = 230mm, 280mm, 330mm or 380mm, L4 = 270mm, S = 42mm. Using the method for determining the dimensions of the structural components of the invention, the natural vibration modes of the test assembly can be obtained through modal measurement tests as shown in the following table.

[0056]

[0057] Tests have shown that using these parameters to design a wind tunnel test model device results in sufficient stiffness and low mass. The first five natural vibration frequencies are all above 1000Hz, which does not resonate with the 7Hz reciprocating frequency of the servo, ensuring the stability of the test structure and the accuracy of the experimental data measurements. Using smaller rod sizes revealed insufficient stiffness, which can lead to significant deformation and resonance with the reciprocating motion, resulting in inaccurate experimental measurements. Using larger rod sizes is more expensive and more prone to gap nonlinearity, resulting in loose installation of the test equipment and measurement errors.

[0058] When using the wind tunnel test model device of the present invention, the wind tunnel is first started according to the test plan. Once the flow rate stabilizes, a speed controller sends a control signal to the propeller motor, controlling the propeller speed to the set test speed. The vibration frequency and amplitude are then set on the computer to control the linear reciprocating servo, driving the T-shaped support rod and propeller to achieve pitch motion. Once the motion stabilizes, the computer receives measurement data from the six-component force balance and completes the measurement of the propeller's dynamic load.

[0059] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with this technical field within the technical scope disclosed by the present invention should be covered by the scope of protection of the present invention.

Claims

1. A wind tunnel test model device for measuring unsteady dynamic loads on a propeller, characterized in that: It includes a motor, a six-component force balance, a T-shaped support rod, a vibration mechanism and a bracket; The T-shaped support rod includes a horizontal rod and a vertical rod; the motor is connected to a six-component force balance; The vibration mechanism includes an L-shaped connecting rod and a linear reciprocating servo. The linear reciprocating servo provides vibration power to drive the L-shaped connecting rod to move. The L-shaped connecting rod drives the T-shaped support rod. The vertical rod of the T-shaped support rod and the linear reciprocating servo are mounted on the bracket through the mounting base; The L-shaped connecting rod includes a first connecting arm and a second connecting arm; a sliding groove is provided at one end of the first connecting arm, and the other end is connected to one end of the second connecting arm; the other end of the second connecting arm is connected to the vertical rod; the linear reciprocating servo includes a reciprocating drive end rod, one end of the reciprocating drive end rod is connected to the power source of the linear reciprocating servo, and the other end is inserted into the sliding groove of the L-shaped connecting rod through a pin.

2. The wind tunnel test model device according to claim 1, characterized in that: The front end and the rear end of the six-component force balance are both circular planes; the front end of the six-component force balance is connected to the motor, and the rear end is fixed on the horizontal rod.

3. The wind tunnel test model device according to claim 1, characterized in that: The linear reciprocating servo is installed directly behind the T-shaped support rod.

4. The wind tunnel test model device according to claim 1, characterized in that: The outer diameter R2, inner diameter R3 and length L3 of the horizontal rod are set as follows: 1 / E c =V f / E f +V m / E m K=(E c *π / 64*(R2 4 -R3 4 )) / L3 Among them, E c is the elastic modulus of the horizontal rod made of carbon fiber; V f is the carbon fiber volume fraction of the horizontal rod made of carbon fiber; E f is the uniaxial elastic modulus of the horizontal rod made of carbon fiber; V m is the volume fraction of the horizontal rod made of carbon fiber; E m is the elastic modulus of the horizontal rod of carbon fiber material; K is the stiffness of the horizontal rod of carbon fiber material.

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