Wind tunnel boundary layer control device and wind tunnel boundary layer control method

Abstract

The invention relates to the technical field of wind tunnels, and provides a wind tunnel boundary layer control device and method. The wind tunnel boundary layer control device comprises a wind tunnel system and a suction system; the wind tunnel system comprises a fan section, an air outlet section, a test section and an air return section which are sequentially arranged in the circulating air flowing direction. The suction system comprises a suction inlet, a suction pipeline and a suction outlet which are sequentially arranged in the air flowing direction. The suction inlet vertically protrudes upwards in the horizontal plane of the test section and is arranged corresponding to the outlet end of the air outlet section; the suction outlet is connected to the inner bottom wall of the air return section in a communicating mode. The latter can be adapted to the former. According to the wind tunnel boundary layer control device, the suction pressure can be adaptively controlled through the suction system, and the problems of insufficient suction and excessive suction caused by poor back pressure change of a fan in a conventional suction mode are effectively solved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of wind tunnels, and in particular to a wind tunnel boundary layer control device and a wind tunnel boundary layer control method. Background Art

[0002] The automobile wind tunnel is a key device for the aerodynamic and thermodynamic ring model test of the whole vehicle. In order to improve the accuracy of the test results, the wind tunnel needs to provide a simulation condition that is as realistic as possible. Unlike road driving, in the automobile wind tunnel, after the airflow leaves the nozzle, the boundary layer will gradually thicken along the test floor. If its influence cannot be effectively eliminated or reduced, the aerodynamic drag of the vehicle will decrease and the lift will increase. However, the influence of the boundary layer on the lift coefficient and lift moment measurement is very complex and difficult to correct using empirical formulas.

[0003] In order to eliminate the influence of the floor boundary layer on the flow field and wind tunnel test results in the automotive environmental wind tunnel, it is necessary to control the development of the boundary layer. Currently, the commonly used methods include floor lifting, suction, blowing, moving the floor, etc., and installing active suction devices such as fans on the suction pipe. This method is prone to over-suction or under-suction problems, and it is not easy to accurately control the boundary layer under different working conditions.

[0004] In view of this, there is an urgent need for a new wind tunnel boundary layer control device and method on the market to solve the problems of over-suction or under-suction and inability to accurately control the boundary layer under different working conditions in the existing wind tunnel boundary layer control device and method. Summary of the invention

[0005] The embodiments of the present disclosure provide a wind tunnel boundary layer control device and a wind tunnel boundary layer control method, in order to solve the problems in the prior art of wind tunnel boundary layer control device and method that over-suction or under-suction is prone to occur and the boundary layer under different working conditions cannot be accurately controlled.

[0006] The wind tunnel boundary layer control device provided by the embodiment of the present disclosure includes a wind tunnel system and a suction system;

[0007] The wind tunnel system comprises a fan section, an air outlet section, a test section and a return air section which are arranged in sequence along the flow direction of the circulating air;

[0008] The suction system comprises a suction inlet, a suction pipe and a suction outlet which are arranged in sequence along the air flow direction;

[0009] Wherein, the suction inlet protrudes vertically upward in the horizontal plane of the test section, and the outlet end of the air outlet section is correspondingly arranged;

[0010] The suction outlet is conductively connected to the inner bottom wall of the return air section.

[0011] In one embodiment, the suction inlet protrudes vertically upward by 60 mm along the horizontal plane.

[0012] In one embodiment, the test section is further provided with a wind tunnel flow field calibration frame for measuring boundary layer thickness and airflow deflection angle;

[0013] The wind tunnel flow field calibration frame is provided with a pitot tube, a direction probe and a differential pressure sensor, and the pitot tube and the direction probe can move relatively along the wind tunnel flow field calibration frame under the drive of a motor.

[0014] In one possible implementation manner, the air outlet section includes a stabilizing section, a contracting section and a nozzle section which are sequentially connected;

[0015] The stabilizing section is provided with a honeycomb and a multi-layer damping net;

[0016] The diameter of the contraction section gradually decreases along the air flow direction.

[0017] In one possible implementation, the wind tunnel system further comprises a tail cone diffusion section;

[0018] The tail cone diffusion section is sequentially connected and arranged downstream of the fan section along the air flow direction.

[0019] In one possible implementation, the wind tunnel system further comprises a plurality of corner connection sections;

[0020] The corner connection section is connected between the tail cone diffusion section and the air outlet section, and between the return air section and the fan section.

[0021] In one possible implementation manner, the wind tunnel boundary layer control device further includes a simulated wind tunnel layout model;

[0022] The simulation wind tunnel layout model can simulate and calculate the boundary layer thickness and displacement thickness in the bottom surface of the test section under different test parameters based on a computational fluid turbulence model.

[0023] In addition, the embodiment of the present disclosure further provides a wind tunnel boundary layer control method, which can be applied to the above-mentioned wind tunnel boundary layer control device, and includes:

[0024] Generate a circulating air flow with preset parameters through the wind tunnel system, and adaptively control the boundary layer on the bottom surface of the test section in the wind tunnel system through the suction system;

[0025] By inputting preset parameters corresponding to the simulation wind tunnel layout model and performing simulation operations, the simulation data of the boundary layer at the bottom surface of the simulation test section are obtained;

[0026] The thickness of the boundary layer in the test section in the wind tunnel system is measured to obtain actual measurement data, and the actual measurement data is compared with the simulation data to verify the control effect of the suction system on the boundary layer in the bottom surface of the test section.

[0027] In one possible implementation, in the step of inputting preset parameters and performing simulation calculations corresponding to the wind tunnel layout model, the gas flow process is simplified as follows:

[0028] The gas flow is considered as steady state and the time term in the governing differential equation is not considered;

[0029] The density change of gas flow process is ignored and the gas is regarded as incompressible flow;

[0030] The solid walls in the simulation wind tunnel are considered to be non-slip.

[0031] Compared with the prior art, the technical solution provided by the embodiments of the present disclosure has the following advantages:

[0032] The wind tunnel boundary layer control device provided in the embodiment of the present disclosure can adaptively control the suction pressure through the suction system, effectively avoiding the problems of under-suction and over-suction caused by the poor back pressure change of the fan in the conventional suction method; and can also simulate and calculate the boundary layer thickness and displacement thickness in the bottom surface of the test section under different test parameters through the simulation wind tunnel layout model, and analyze and verify the ground effect simulation results by combining the actual wind tunnel test and the computational fluid dynamics method of the simulation wind tunnel layout model, so as to realize the automobile wind tunnel boundary layer control under continuously variable wind speed.

[0033] In addition, the wind tunnel boundary layer control method provided in the embodiment of the present disclosure can be applied to the above-mentioned wind tunnel boundary layer control device, and can also analyze and verify the ground effect simulation results by combining actual wind tunnel tests with the computational fluid dynamics method of the simulated wind tunnel layout model, thereby realizing automobile wind tunnel boundary layer control under continuously variable wind speed.

[0034] It should be understood that the content described in this section is not intended to identify the key or important features of the embodiments of the present disclosure, nor is it intended to limit the scope of the present disclosure. Other features of the present disclosure will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The above and other objects, features and advantages of the exemplary embodiments of the present disclosure will become readily understood by reading the detailed description below with reference to the accompanying drawings. In the accompanying drawings, several embodiments of the present disclosure are shown in an exemplary and non-limiting manner, in which:

[0036] In the drawings, the same or corresponding reference numerals represent the same or corresponding parts.

[0037] Figure 1 A top view of a wind tunnel boundary layer control device provided by an embodiment of the present disclosure is shown;

[0038] Figure 2 A vertical cross-sectional view of a wind tunnel boundary layer control device provided by an embodiment of the present disclosure is shown;

[0039] Figure 3 A partial schematic diagram of a wind tunnel boundary layer control device provided by an embodiment of the present disclosure is shown;

[0040] Figure 4 A simulation schematic diagram of a wind tunnel boundary layer control device provided by an embodiment of the present disclosure is shown;

[0041] Figure 5 A test parameter diagram of three different nozzle velocities of a wind tunnel boundary layer control device provided by an embodiment of the present disclosure is shown.

[0042] Explanation of the numbers in the figure: 1, wind tunnel system; 11, fan section; 12, air outlet section; 121, stable section; 122, contraction section; 123, nozzle section; 13, test section; 14, return air section; 15, tail cone diffusion section; 16, corner connection section;

[0043] 2. Suction system; 21. Suction inlet; 22. Suction pipeline; 23. Suction outlet. DETAILED DESCRIPTION

[0044] In order to make the purpose, features, and advantages of the present disclosure more obvious and easy to understand, the technical solutions in the embodiments of the present disclosure will be clearly and completely described below in conjunction with the drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of the embodiments of the present disclosure, not all of the embodiments. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present disclosure.

[0045] The embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings.

[0046] Combination Figure 1 , Figure 2 and Figure 3As shown, the embodiment of the present disclosure provides a wind tunnel boundary layer control device, which includes a wind tunnel system 1 and a suction system 2; the wind tunnel system 1 includes a fan section 11, an air outlet section 12, a test section 13 and a return air section 14 arranged in sequence along the flow direction of the circulating air; the fan blades in the fan section 11 can be respectively provided with front and rear anti-rotation vanes, the front anti-rotation vanes can improve the flow field uniformity of the fan intake, and the rear anti-rotation vanes are conducive to overcoming the air flow separation caused by the rotation of the airflow behind the fan; the air outlet section 12 can stabilize the turbulent and uneven airflow, attenuate the vortex, and make the distribution of the speed size and direction more uniform. The air outlet section 12 can specifically include a stabilizing section 121, a contracting section 122 and a nozzle section 123 arranged in sequence; the stabilizing section 121 is provided with a honeycomb and a multi-layer damping net to effectively reduce the turbulence intensity; the caliber of the contracting section 122 gradually decreases along the air flow direction, mainly to uniformly accelerate the incoming flow and improve the flow field quality of the test section 13.

[0047] The suction system 2 includes a suction inlet 21, a suction duct 22 and a suction outlet 23 which are sequentially arranged along the air flow direction; wherein the suction inlet 21 protrudes vertically upward in the horizontal plane of the test section 13, and is correspondingly arranged at the outlet end of the air outlet section 12; the suction outlet 23 is conductively connected to the inner bottom wall of the return air section 14, and the suction inlet 21 can specifically protrude vertically upward by 60 mm along the horizontal plane.

[0048] The wind tunnel boundary layer control device provided in the embodiment of the present disclosure is based on the horizontal suction principle, but is essentially different from the manually controlled horizontal suction device in the wind tunnel of the prior art. The manually controlled horizontal suction device is prone to under-suction and over-suction risks when regulating the development of the boundary layer in the test section under different wind speeds in the wind tunnel.

[0049] In the wind tunnel boundary layer control device provided in the embodiment of the present disclosure, the suction inlet 21 of the suction system 2 is located at the outlet end of the air outlet section 12, and the suction inlet 21 is vertically raised 60 mm upward along the horizontal plane of the test section 13, and the suction outlet 23 is conductively connected to the inner bottom wall of the return air section 14, so that the "control and regulation" of the suction pressure of the suction system 2 mainly comes from the inlet dynamic pressure of the air outlet section 12 and the static pressure change of the test section 13 during the circulation flow in the wind tunnel system 1, and the suction amount of the suction system 2 will also change adaptively with the velocity flow and pressure loss in the wind tunnel system 1. Therefore, the method of adaptively adjusting the suction pressure in the suction system 2 can effectively avoid the problems of under-suction and over-suction caused by the manual control of the suction method in the prior art.

[0050] In addition, the wind tunnel boundary layer control device provided in the embodiment of the present disclosure also includes a simulated wind tunnel layout model; the simulated wind tunnel layout model can simulate and calculate the boundary layer thickness and displacement thickness in the bottom surface of the test section under different test parameters based on the computational fluid turbulence model.

[0051] The simulation wind tunnel layout model can be specifically established based on the CFD (Computational Fluid Dynamics) method. The simulation wind tunnel layout model can be compared and verified using CFD and the actual test method of the wind tunnel system 1, so as to compare and verify the boundary layer control effect of the suction system 2 on the bottom wall of the test section 13.

[0052] When the simulation wind tunnel layout model is established using the CFD method, the wind tunnel outlet can be set to a square outlet of 3.05m×2.69m, and the maximum wind speed at the outlet is ≥180km / h. In order to improve the calculation accuracy, the calculation domain is divided into structural grids. For the calculation of the wall boundary layer, the wall boundary is encrypted using a multi-layer O block nesting method, and the total number of grids is 9.873 million.

[0053] Moreover, in the CFD example, the gas flow process can be simplified as follows:

[0054] The calculated gas flow is considered as steady state and the time term in the control differential equation is not considered;

[0055] Since the gas flows at a low speed, the change of gas density during the flow is not considered, and the gas is regarded as an incompressible flow;

[0056] The solid wall in the simulated wind tunnel has no slip;

[0057] Moreover, ANSYS FLUENT16.0 can be used to solve the equations. Based on the above assumptions, the flow control equation adopts the NS equations of incompressible flow. The turbulence model Standard ke has high accuracy, strong applicability, high stability and reasonable accuracy. Therefore, Standard ke is used as the turbulence model.

[0058] The inlet mass flow rate is used as the inlet boundary condition of the contraction section 122, and the pressure loss calculation result is used as the outlet boundary condition of the outlet section 12. The damping net uses the porous-jump boundary condition to simulate the effect of the damping net. The outlet velocities of the outlet section 123 are 80km / h, 135km / h, and 180km / h, respectively. The calculation result of 180km / h is as follows: Figure 4 shown.

[0059] In one embodiment, a wind tunnel flow field calibration frame for measuring boundary layer thickness and airflow deflection angle is also provided in the test section 13; a Pitot tube, a directional probe and a differential pressure sensor are provided in the wind tunnel flow field calibration frame, and the Pitot tube and the directional probe can move relative to each other along the wind tunnel flow field calibration frame driven by a motor.

[0060] In this way, when the wind tunnel boundary layer control device is actually tested, the nozzle section 123 is tested at speeds of 80km / h, 135km / h, and 180km / h, respectively. The boundary layer thickness test section is located at the nozzle section 123 outlet 1m along the airflow direction, and three different positions within a 2m range in the Y direction can be measured (-1m, 0m, 1m). The pitot tube and differential pressure sensor in the wind tunnel flow field calibration frame are relatively moved along the wind tunnel flow field calibration frame to complete the measurement and calculation of the boundary layer thickness.

[0061] In the specific actual experimental research, the boundary layer thickness test section is located at the outlet of the nozzle section 123, 1m in the direction of the airflow. The test range on this section is 2m along the Y direction to measure three different positions (-1m, 0m, 1m). The pitot tube and high differential pressure sensor on the wind tunnel flow field calibration frame are relatively moved along the wind tunnel flow field calibration frame to complete the measurement and calculation of the boundary layer thickness. The nozzle speeds of the nozzle section 123 are tested at 80km / h, 135km / h, and 180km / h, respectively. The results of selecting the center position of the section (y=0mm) are shown in Table 1 below.

[0062] Table 1 Test results

[0063]

[0064] Figure 5 (a), (b), and (c) correspond to the changes in the airflow velocity along the height direction at the center of the cross section 1m away from the nozzle of nozzle section 123 at three different nozzle velocities. When the boundary layer is not controlled in the wind tunnel, the maximum boundary layer thickness at the three speeds is about 155mm. If the thickness of the boundary layer continues to increase in the test section 13, it will affect the heat exchange effect of the automobile chassis in the test section 13. After adding the suction measures of the adaptive suction system 2, the development of the boundary layer is effectively controlled, and the maximum boundary layer thickness is ≤40mm.

[0065] In the CFD simulation experiment of the simulated wind tunnel layout model, the simulation experiment of the above parameters was also carried out. The boundary layer thickness and displacement thickness results at three speeds are shown in Table 2 below:

[0066] Table 2 Comparison of boundary layer thickness results

[0067]

[0068] At the section 1m away from the nozzle in the front end of the simulation test area, the maximum thickness of the boundary layer is 38.48mm, and the maximum displacement thickness is 3.4mm. The development of the boundary layer has been effectively controlled. Since the actual test and CFD simulation calculation position section are close to the suction port, the value is small, so the relative error has a certain instability. At the same time, the test results show that at different Y-direction positions on the same section, there are certain differences in the development of the boundary layer, but the overall trend and range remain consistent, indicating that the existing CFD simulation calculation method can be used to study boundary layer related issues.

[0069] In order to analyze the influence of the adaptive suction mode of the suction system 2 on the airflow deflection angle, the airflow deflection angle was measured at the center position of the 1m section of the nozzle outlet, and the test results are shown in Table 3. It can be seen that considering a certain test error, the adaptive suction mode of the suction system 2 has little effect on the airflow deflection angle, and the maximum airflow deflection angle is ≤+0.5°.

[0070] Table 3 Airflow deflection test results

[0071]

[0072] Based on the wind tunnel of the whole vehicle, the actual test research and simulation model numerical simulation of the adaptive boundary layer control method were carried out. After the analysis of the results, the following conclusions were drawn:

[0073] (1) The wind tunnel boundary layer control device can effectively control the development of the boundary layer in the test section 13 of the automobile wind tunnel at different wind speeds, reduce the displacement thickness of the boundary layer, and avoid the risks of under-suction and over-suction caused by suction by artificially controlling the back pressure;

[0074] (2) The adaptive suction mode of the suction system 2 in the wind tunnel boundary layer control device has little effect on the quality of the wind tunnel flow field. The horizontal and pitch angles of the airflow in the test section 13 are ≤0.35°, which meets the requirements of the airflow angle of the wind tunnel test.

[0075] (3) The wind tunnel boundary layer control device is realized by the suction system 2 adaptively sucking away the low-energy airflow near the ground at the outlet of the nozzle section 123, and is suitable for test equipment such as automobile wind tunnels that require ground effect simulation.

[0076] In one possible implementation, the wind tunnel system 1 further includes a plurality of corner connection sections 16 ; the corner connection sections 16 are connected between the tail cone diffuser section 15 and the air outlet section 12 , and between the return air section 14 and the fan section 11 .

[0077] Since the wind tunnel system 1 is a recirculation wind tunnel, in order to ensure smooth airflow when turning, reduce the diffusion and contraction effects of the inner and outer walls, and reduce airflow separation, the guide vanes in the corner connection section 16 can be reasonably aerodynamically designed.

[0078] In addition, the embodiment of the present disclosure further provides a wind tunnel boundary layer control method, which is characterized in that it can be applied to the above-mentioned wind tunnel boundary layer control device, and includes:

[0079] The first step S1—generating a circulating air flow with preset parameters through the wind tunnel system, and adaptively controlling the boundary layer in the bottom surface of the test section in the wind tunnel system through the suction system;

[0080] The second step S2—by inputting preset parameters corresponding to the simulation wind tunnel layout model and performing simulation calculations, the simulation data of the boundary layer at the bottom surface of the simulation test section are obtained;

[0081] The third step S3 - measuring the thickness of the boundary layer in the test section of the wind tunnel system, obtaining actual measurement data, and comparing the actual measurement data with the simulation data to verify the control effect of the suction system on the boundary layer in the bottom surface of the test section.

[0082] In one possible implementation, in the step of inputting preset parameters and performing simulation calculations corresponding to the wind tunnel layout model, the gas flow process is simplified as follows:

[0083] The gas flow is considered as steady state and the time term in the governing differential equation is not considered;

[0084] The density change of gas flow process is ignored and the gas is regarded as incompressible flow;

[0085] Treating solid walls in a wind tunnel simulation as no-slip

[0086] The wind tunnel boundary layer control method can be applied to the above-mentioned wind tunnel boundary layer control device, and can also analyze and verify the ground effect simulation results by combining actual wind tunnel tests with the computational fluid dynamics method of the simulated wind tunnel layout model, so as to realize the automobile wind tunnel boundary layer control under continuously variable wind speed.

[0087] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present disclosure, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0088] The above are only specific embodiments of the present disclosure, but the protection scope of the present disclosure is not limited thereto. Any technician familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed in the present disclosure, which should be included in the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be based on the protection scope of the claims.

Claims

1. A wind tunnel boundary layer control device, characterized in that: include: A wind tunnel system (1) comprises a fan section (11), an air outlet section (12), a test section (13) and a return air section (14) which are arranged in sequence along the flow direction of circulating air; A suction system (2) comprising a suction inlet (21), a suction duct (22) and a suction outlet (23) arranged in sequence along the air flow direction; Wherein, the suction inlet (21) protrudes vertically upward in the horizontal plane of the test section (13), and is correspondingly arranged at the outlet end of the air outlet section (12); The suction outlet (23) is conductively connected to the inner bottom wall of the return air section (14).

2. The wind tunnel boundary layer control device according to claim 1, characterized in that: The suction inlet (21) protrudes vertically upward by 60 mm along the horizontal plane.

3. The wind tunnel boundary layer control device according to claim 1, characterized in that: The test section (13) is also provided with a wind tunnel flow field calibration frame for measuring the boundary layer thickness and airflow deflection angle; The wind tunnel flow field calibration frame is provided with a pitot tube, a direction probe and a differential pressure sensor, and the pitot tube and the direction probe can move relatively along the wind tunnel flow field calibration frame under the drive of a motor.

4. The wind tunnel boundary layer control device according to claim 1, characterized in that: The air outlet section (12) comprises a stabilizing section (121), a contracting section (122) and a nozzle section (123) which are sequentially connected; The stabilizing section (121) is provided with a honeycomb and a multi-layer damping net; The diameter of the contraction section (122) gradually decreases along the air flow direction.

5. The wind tunnel boundary layer control device according to claim 1, characterized in that: The wind tunnel system (1) further comprises a tail cone diffusion section (15); The tail cone diffusion section (15) is sequentially connected and arranged downstream of the fan section (11) along the air flow direction.

6. The wind tunnel boundary layer control device according to claim 5, characterized in that: The wind tunnel system (1) further comprises a plurality of corner connection sections (16); The corner connection section (16) is connected between the tail cone diffusion section (15) and the air outlet section (12), and between the return air section (14) and the fan section (11).

7. The wind tunnel boundary layer control device according to any one of claims 1 to 6, characterized in that: The wind tunnel boundary layer control device also includes a simulated wind tunnel layout model; The simulation wind tunnel layout model can simulate and calculate the boundary layer thickness and displacement thickness in the bottom surface of the test section under different test parameters based on a computational fluid turbulence model.

8. A wind tunnel boundary layer control method, characterized in that: The wind tunnel boundary layer control device can be applied to claim 7, characterized in that it comprises: Generate a circulating air flow with preset parameters through the wind tunnel system, and adaptively control the boundary layer on the bottom surface of the test section in the wind tunnel system through the suction system; By inputting preset parameters corresponding to the simulation wind tunnel layout model and performing simulation operations, the simulation data of the boundary layer at the bottom surface of the simulation test section are obtained; The thickness of the boundary layer in the test section in the wind tunnel system is measured to obtain actual measurement data, and the actual measurement data is compared with the simulation data to verify the control effect of the suction system on the boundary layer in the bottom surface of the test section.

9. The wind tunnel boundary layer control method according to claim 8, characterized in that: In the steps of inputting preset parameters and performing simulation calculations corresponding to the simulation wind tunnel layout model, the gas flow process is simplified as follows: The gas flow is considered as steady state and the time term in the governing differential equation is not considered; The density change of gas flow process is ignored and the gas is regarded as incompressible flow; The solid walls in the simulation wind tunnel are considered to be non-slip.

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