A three-stage continuous combined boundary layer control system for an automotive wind tunnel

Abstract

The present invention relates to a three-stage continuous combined boundary layer control system for an automotive wind tunnel, comprising a horizontal suction system, a first vertical suction system, a second vertical suction system, a tangential jet system, and a control module. The suction port of the horizontal suction device is located within the nozzle, the suction port of the first vertical suction device is located on the ground between the nozzle outlet and the balance turntable, the suction port of the second vertical suction device is located on the balance turntable, and the jet port of the tangential jet device is located between the suction port of the second vertical suction device and the moving belt. Compared with the prior art, the present invention proposes a boundary layer control system that utilizes a three-stage continuous combination of horizontal suction, vertical suction, and tangential jet. The horizontal suction device is arranged at the nozzle outlet, a weak vertical suction device is used at the nozzle and the front end of the test model, and a tangential jet is used in front of the moving belt. Ultimately, the boundary layer of the test area is controlled while not affecting the axial static pressure gradient.

Description

Technical Field

[0001] The present invention relates to the technical field of automobile wind tunnels, and in particular to a three-stage continuous combined boundary layer control system for an automobile wind tunnel. The control system is used to control the ground boundary layer of an automobile wind tunnel test section by continuously combining horizontal suction, vertical suction, and tangential jets in a three-stage manner without generating negative effects such as additional axial static pressure gradients or airflow angles of attack that could induce experimental errors. Background Art

[0002] When the fluid moves relative to the solid wall, the influence of the viscous force in the thin layer near the solid wall cannot be ignored, and there is a considerable velocity gradient along the normal direction of the wall. This is the so-called boundary layer in fluid mechanics.

[0003] Under ideal conditions, since there is no relative motion between the airflow and the road, the airflow in front of a real-world vehicle has no boundary layer near the ground. However, wind tunnel testing uses a stationary vehicle and flowing airflow. Viscous friction causes the airflow to adhere to the ground, inevitably forming a boundary layer. Extensive testing has shown that as the thickness of the boundary layer increases, the measured drag coefficient decreases, and within a certain range, there is a linear decreasing relationship, which can be corrected. However, the effect of the boundary layer on lift and torque is more complex, making it difficult to correct using empirical formulas.

[0004] In order to simulate the airflow characteristics of a car driving on a real road, automotive wind tunnels must eliminate the boundary layer through appropriate technical measures. Boundary layer control is a technology unique to automotive wind tunnels. It is necessary to eliminate the vertical velocity gradient changes caused by the boundary layer to achieve uniform incoming flow in the wind tunnel, and to control interference to avoid the negative effects such as axial static pressure gradients or airflow angles of attack that affect the errors of wind tunnel experiments.

[0005] Common boundary layer control technologies currently used in automotive wind tunnels include vertical suction and tangential jets. Vertical suction can be categorized as either completely vertical to the ground or partially inclined with a height difference. Its purpose is to remove low-kinetic-energy boundary layer airflow. Tangential jets, on the other hand, increase the kinetic energy of the airflow within the boundary layer by creating a jet parallel to the floor through a narrow slit. However, vertical suction often generates an additional axial static pressure gradient, leading to "horizontal buoyancy" errors in the test model, while tangential jets are prone to airflow deviation.

[0006] Tongji University's Shanghai Ground Transportation Wind Tunnel Center has for the first time adopted a more effective and reasonable horizontal suction boundary layer control method. Test results show that by raising the floor at the front end of the test section and adjusting the suction flow according to the test wind speed and model blockage, the boundary layer thickness can be made close to zero, without affecting the axial pressure gradient.

[0007] In addition, flow control of horizontal suction, vertical suction, and tangential jets is also crucial. Excessive or insufficient flow can cause airflow deviation or additional boundary layers, resulting in the inflow of the test section not matching the actual situation. At the same time, if the vertical suction distribution area is extended to the test model area, it will also affect the airflow around the test model, causing uncertainty in the test results. Finally, for airflow deviation testing, the balance turntable can be freely deflected within a certain angle range. In addition, the complex "five-belt" system is integrated, and the layout of the suction pipes within the turntable is also subject to certain restrictions.

[0008] In summary, the existing technology cannot effectively eliminate the impact of the wind tunnel boundary layer on automobile aerodynamic tests. Therefore, it is necessary to further study the boundary layer elimination scheme to achieve control of the boundary layer in the test area. Summary of the Invention

[0009] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide a three-stage continuous combined boundary layer control system for an automobile wind tunnel. A horizontal suction device is arranged at the nozzle outlet to eliminate the boundary layer of the airflow coming out of the nozzle; a weak vertical suction device is used at the front end of the nozzle and the test model to maintain the boundary layer thickness basically unchanged; a tangential jet is used in front of the moving belt to supplement the kinetic energy of the airflow in the boundary layer; and finally, the boundary layer of the test area is controlled without affecting the axial static pressure gradient.

[0010] The purpose of the present invention can be achieved by the following technical solutions:

[0011] A three-stage continuous combined boundary layer control system for an automobile wind tunnel, which is used in an automobile wind tunnel consisting of a stationary chamber and a flow channel, comprises a horizontal suction system, a first vertical suction system, a second vertical suction system, a tangential jet system and a control module;

[0012] The two ends of the flow channel are respectively provided with a nozzle and a collecting port, the nozzle is used to eject airflow, and the collecting port is used to recover airflow. The nozzle and the collecting port are located at both ends of the stationary chamber. A rotatable balance turntable is provided on the floor of the stationary chamber, and the test model is placed on the balance turntable. A moving belt is provided on the balance turntable, and the moving belt is located at the bottom of the test model.

[0013] The horizontal suction system includes a horizontal suction device, a horizontal suction pipeline, a horizontal suction flow meter, a horizontal suction electric air valve and a horizontal suction variable frequency fan;

[0014] The first vertical suction system includes a first vertical suction device, a first vertical suction pipeline, a first vertical suction flow meter, a first vertical suction electric air valve and a first vertical suction variable frequency fan;

[0015] The second vertical suction system includes a second vertical suction device, a second vertical suction pipe, a second vertical suction flow meter, a second vertical suction electric air valve and a second vertical suction variable frequency fan;

[0016] The tangential jet system includes a tangential jet device, a tangential jet pipeline, a tangential jet flowmeter, a tangential jet electric air valve and a tangential jet variable frequency fan;

[0017] The control module is connected to the horizontal suction flowmeter, the horizontal suction electric air valve, the horizontal suction variable frequency fan, the first vertical suction flowmeter, the first vertical suction electric air valve, the first vertical suction variable frequency fan, the second vertical suction flowmeter, the second vertical suction electric air valve, the second vertical suction variable frequency fan, the tangential jet flowmeter, the tangential jet electric air valve and the tangential jet variable frequency fan;

[0018] The suction port of the horizontal suction device is located inside the nozzle, the suction port of the first vertical suction device is located on the ground between the nozzle outlet and the balance turntable, the suction port of the second vertical suction device is located on the balance turntable, and the jet port of the tangential jet device is located between the suction port of the second vertical suction device and the moving belt.

[0019] Furthermore, the suction port on the horizontal suction device is connected to the horizontal suction duct through a horizontal suction cavity, the horizontal suction duct merges into the total return air duct, the total return air duct leads to the flow channel, and the horizontal suction cavity is a circular arc gradually expanding cavity.

[0020] Furthermore, the suction port on the first vertical suction device includes a plurality of suction holes distributed on the ground between the nozzle outlet and the balance turntable. The suction holes are connected to the first vertical suction pipe through the first vertical suction cavity. The first vertical suction pipe merges into the main return air pipe, and the main return air pipe leads to the flow channel.

[0021] Furthermore, the suction port on the second vertical suction device includes a plurality of suction holes distributed on the balance turntable, and the suction holes are connected to the second vertical suction duct through the second vertical suction cavity. The second vertical suction duct merges into the main return air duct, and the main return air duct leads to the flow channel.

[0022] Furthermore, the collecting port is connected to the diffusion section, the diffusion section is connected to the connecting section, the connecting section is connected to the nozzle, and the total return air duct leads to the connecting section.

[0023] Furthermore, the jet outlet of the tangential jet device is a narrow slit, the jet ejected from the jet outlet is consistent with the direction of the flow from the jet outlet and is close to the surface of the balance turntable, the jet outlet is connected to the tangential jet pipe through the tangential jet cavity, and the tangential jet pipe is connected to the atmosphere.

[0024] Furthermore, the tangential jet pipe is divided into a tangential jet pipe on the turntable and a tangential jet pipe outside the turntable, and the tangential jet pipe on the turntable and the tangential jet pipe outside the turntable are connected via a second rotating pipe joint.

[0025] Furthermore, the second vertical suction pipe is divided into a second vertical suction pipe on the turntable and a second vertical suction pipe outside the turntable, and the second vertical suction pipe on the turntable and the second vertical suction pipe outside the turntable are connected through a first rotating pipe joint.

[0026] Furthermore, the test wind speed U0 and horizontal suction flow rate Q are pre-calibrated SC The control module controls the horizontal suction variable frequency fan based on the horizontal suction flow meter signal and the test wind speed U0 to adjust the horizontal suction flow to the preset horizontal suction flow, the horizontal suction flow Q SC The calculation formula is as follows:

[0027] Q SC =η SC ·U0·A SC

[0028] Among them, η SC Indicates the suction rate of the suction port of the horizontal suction device, A SC represents the inlet area of the suction port of the horizontal suction device, U0 represents the test wind speed, η SC The calculation formula is:

[0029]

[0030] Among them, U SC Indicates the suction airflow velocity at the suction port of a horizontal suction device.

[0031] Furthermore, the test wind speed U0 and the first vertical suction flow Q are pre-calibrated. SUC1 The control module controls the first vertical suction variable frequency fan based on the first vertical suction flow meter signal and the test wind speed U0 to adjust the first vertical suction flow to the preset first vertical suction flow. The first suction flow Q SUC1 The calculation formula is as follows:

[0032] Q SUC1 =η SUC1 ·U0·A SUC1

[0033] Among them, η SUC1 represents the suction rate of the suction port of the first suction device, A SUC1 represents the inlet area of the suction port of the first suction device, U0 represents the test wind speed, η SUC1The calculation formula is:

[0034]

[0035] Among them, U SUC1 Indicates the suction airflow velocity of the suction port of the first vertical suction device.

[0036] Furthermore, the test wind speed U0 and the second vertical suction flow Q are pre-calibrated. SUC2 The control module controls the second vertical suction variable frequency fan based on the second vertical suction flow meter signal and the test wind speed U0 to adjust the second vertical suction flow to the preset second vertical suction flow. The second suction flow Q SUC2 The calculation formula is as follows:

[0037] Q SUC2 =η SUC2 ·U0·A SUC2

[0038] Among them, η SUC2 A represents the suction rate of the suction port of the second suction device, SUC2 represents the inlet area of the suction port of the second suction device, U0 represents the test wind speed, η SUC2 The calculation formula is:

[0039]

[0040] Among them, U SUC2 Indicates the suction airflow velocity of the suction port of the second vertical suction device.

[0041] Furthermore, the test wind speed U0 and tangential jet flow rate Q are pre-calibrated TB The control module controls the tangential jet variable frequency fan based on the tangential jet flowmeter signal and the test wind speed U0 to adjust the tangential jet flow rate to the preset tangential jet flow rate, the tangential jet flow rate Q TB The calculation formula is as follows:

[0042] Q TB =η TB ·U0·A TB

[0043] Among them, η TB Indicates the jet rate of the jet orifice of the tangential jet device, A TB represents the outlet area of the jet port of the tangential jet device, U0 represents the test wind speed, η TB The calculation formula is:

[0044]

[0045] Among them, U TB Indicates the jet air flow velocity at the jet outlet of the tangential jet device.

[0046] Compared with the prior art, the present invention has the following beneficial effects:

[0047] (1) It can effectively eliminate the influence of wind tunnel boundary layer on automobile aerodynamic test, and overcome the negative effects of test section airflow deflection angle or axial static pressure gradient change caused by traditional boundary layer control methods such as vertical suction or tangential jet.

[0048] (2) Horizontal suction, vertical suction and tangential jet are used for three-level continuous control. The suction system covers the area from the nozzle outlet to the leading edge of the moving belt, and there is no regeneration boundary layer in front of the moving belt. Horizontal suction completely eliminates the boundary layer inside the wind tunnel nozzle, and the burden of vertical suction is greatly reduced. Weak vertical suction is used to control the regeneration of the boundary layer, and the noise level generated by the system itself is low. The tangential jet assists the movement of the moving belt, making the airflow on the surface of the moving belt completely uniform, that is, a zero-thickness boundary layer.

[0049] (3) The return air inlet is set in the connecting section, closer to the fan, the return air back pressure is low, the power required by the system is small, and the energy consumption is lower.

[0050] (4) For the second vertical suction pipe and the tangential jet pipe that need to rotate with the balance turntable, a first rotating pipe joint and a second rotating pipe joint are designed, and the second rotating pipe joint of the tangential jet pipe can be built into the second vertical suction pipe to reduce the space occupied by the pipe. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] Figure 1 It is a structural schematic diagram of the present invention;

[0052] Figure 2 Schematic diagram of the distribution positions of the horizontal suction device, the vertical suction device and the tangential jet device;

[0053] Figure 3 Schematic diagram of the distribution positions of the horizontal suction device, the vertical suction device and the tangential jet device;

[0054] Figure 4 is a schematic diagram of a first rotary pipe joint and a second rotary pipe joint;

[0055] Figure 5 It is a schematic diagram of the horizontal suction effect of the present invention;

[0056] Figure 6 It is a schematic diagram of the vertical suction effect of the present invention;

[0057] Figure 7 Schematic diagram of the tangential jet structure of the present invention;

[0058] Figure 8 This is a schematic diagram of the tangential jet effect of the present invention;

[0059] Figure 9 It is a schematic diagram of the application of the present invention;

[0060] Figure 10 Schematic diagram of the axial static pressure gradient in the wind tunnel test section for the entire vehicle aerodynamics and acoustics;

[0061] Figure 11 Schematic diagram of the boundary layer measurement results of the full vehicle aerodynamic and acoustic wind tunnel test section;

[0062] Figure 1: Horizontal suction device, 2: First vertical suction device, 3: Second vertical suction device, 4: Tangential jet device, 5: Nozzle, 6: Moving belt, 7: Test model, 8: Floor of stationary chamber, 9: Collecting port, 10: Stationary chamber, 11: Diffusion section, 12: Connecting section, 13: Horizontal suction pipe, 14: First vertical suction pipe, 15: Second vertical suction pipe, 16: Tangential jet pipe, 17: Horizontal suction flowmeter, 18: First vertical suction flowmeter, 19: Second vertical suction Suction flowmeter, 20, tangential jet flowmeter, 21, horizontal suction electric damper, 22, first vertical suction electric damper, 23, second vertical suction electric damper, 24, tangential jet electric damper, 25, horizontal suction variable frequency fan, 26, first vertical suction variable frequency fan, 27, second vertical suction variable frequency fan, 28, tangential jet variable frequency fan, 29, main return air duct, 30, control module, 31, first rotary pipe joint, 32, second rotary pipe joint, 33, balance turntable, 34, boundary layer;

[0063] 1-1. Suction port of the horizontal suction device, 1-2. Horizontal suction cavity of the horizontal suction device, 2-1. Suction port of the first vertical suction device, 2-2. First vertical suction cavity of the first vertical suction device, 3-1. Suction port of the second vertical suction device, 3-2. Second vertical suction cavity of the second vertical suction device, 4-1. Jet port of the tangential jet device, 4-2. Tangential jet cavity of the tangential jet device; 5-1. Nozzle outlet plane, 5-2. Nozzle wall, 6-1. Moving belt roller, 6-2. Moving belt body; 15-1. Upper part of the turntable of the second vertical suction pipe, 15-2. Outer part of the turntable of the second vertical suction pipe, 16-1. Upper part of the turntable of the tangential jet pipe, 16-2. Outer part of the turntable of the tangential jet pipe; 33-1. Rotating axis of the balance turntable, 34-1, 34-2, 34-3. Different positions of the boundary layer. DETAILED DESCRIPTION

[0064] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0065] In the drawings, components with identical structures are denoted by the same reference numerals, and components with similar structures or functions are denoted by similar reference numerals. The size and thickness of each component shown in the drawings are arbitrary and are not limited by the present invention. For clarity, some components in the drawings are exaggerated.

[0066] In the description of the embodiments of the present application, it should be understood that the terms "center", "up", "down", "left", "right", "vertical", "horizontal", "inside", "outside", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the product of the application is conventionally placed when in use, or are the orientations or positional relationships conventionally understood by those skilled in the art. They are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0067] Furthermore, the terms “first,” “second,” “third,” etc., are merely used for distinguishing descriptions and are not to be understood as indicating or implying relative importance.

[0068] In the description of the embodiments of the present application, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to internal connections between two components. Those skilled in the art will understand the specific meanings of the above terms in this application based on the specific circumstances.

[0069] Example 1:

[0070] A three-stage continuous combined boundary layer control system for an automobile wind tunnel, the overall structure is as follows Figure 1 As shown, the automobile wind tunnel composed of a stationary chamber 10 and a flow channel includes a horizontal suction system, a first vertical suction system, a second vertical suction system, a tangential jet system and a control module 30;

[0071] The two ends of the flow channel are respectively a nozzle 5 and a collecting port 9, the nozzle 5 is used to eject airflow, and the collecting port 9 is used to recover airflow. The nozzle 5 and the collecting port 9 are located at both ends of the station chamber 10, and a rotatable balance turntable 33 is provided on the ground of the station chamber 10. When the present application is used for testing, the car to be tested (i.e., the test model 7) is placed on the balance turntable 33, and a moving belt 6 is provided on the balance turntable 33. The moving belt 6 is used to simulate the relative movement between the ground and the vehicle. The moving belt 6 is located at the bottom of the test model 7, so that the aerodynamic force it is subjected to is measured by the balance under the balance turntable 33. The horizontal suction system, the first vertical suction system, the second vertical suction system, the tangential jet system and the control module 30 are used to control the boundary layer of the test area without affecting the axial static pressure gradient.

[0072] The horizontal suction system includes a horizontal suction device 1, a horizontal suction pipe 13, a horizontal suction flowmeter 17, a horizontal suction electric air valve 21 and a horizontal suction variable frequency fan 25; the first vertical suction system includes a first vertical suction device 2, a first vertical suction pipe 14, a first vertical suction flowmeter 18, a first vertical suction electric air valve 22 and a first vertical suction variable frequency fan 26; the second vertical suction system includes a second vertical suction device 3, a second vertical suction pipe 15, a second vertical suction flowmeter 19, a second vertical suction electric air valve 23 and a second vertical suction variable frequency fan 27; the tangential jet system includes a tangential jet system. The tangential jet device 4, the tangential jet duct 16, the tangential jet flowmeter 20, the tangential jet electric damper 24 and the tangential jet variable frequency fan 28; the control module 30 (also called the boundary layer control module) is connected to the horizontal suction flowmeter 17, the horizontal suction electric damper 21, the horizontal suction variable frequency fan 25, the first vertical suction flowmeter 18, the first vertical suction electric damper 22, the first vertical suction variable frequency fan 26, the second vertical suction flowmeter 19, the second vertical suction electric damper 23, the second vertical suction variable frequency fan 27, the tangential jet flowmeter 20, the tangential jet electric damper 24 and the tangential jet variable frequency fan 28;

[0073] The distribution positions of the horizontal suction device 1, the vertical suction device and the tangential jet device 4 are as follows: Figure 2 and Figure 3 As shown, the suction port of the horizontal suction device 1 is located in the nozzle 5, the suction port of the first vertical suction device 2 is located on the floor 8 of the chamber between the outlet of the nozzle 5 and the balance turntable 33, the suction port of the second vertical suction device 3 is located on the balance turntable 33, and the jet port of the tangential jet device 4 is located between the suction port of the second vertical suction device 3 and the moving belt 6.

[0074] In practice, the three-stage continuous boundary layer control includes a horizontal suction section, a vertical suction section, and a tangential jet section. The vertical suction section's suction area is divided into two parts due to the balance turntable 33, thus separating into a first vertical suction system and a second vertical suction system. In practical applications, given the large size of the duct and the difficulty of fans in achieving uniform suction and jet flow across long cross-sections, the duct is often split into multiple ducts, each implemented by multiple fans. For example, the horizontal and vertical suction ducts can be divided into two ducts, each equipped with a fan. These two fans can be collaboratively controlled to achieve horizontal suction. This is readily understood by those skilled in the art and will not be further elaborated upon here.

[0075] The two ends of the flow channel are respectively a nozzle 5 and a collecting port 9 . The collecting port 9 is connected to a diffusion section 11 . The diffusion section 11 is connected to a connecting section 12 . The connecting section 12 is connected to the nozzle 5 .

[0076] The moving belt 6 includes a moving belt roller 6 - 1 and a moving belt body 6 - 2 , which is similar to a conveyor belt structure. The moving belt body 6 - 2 moves with the rotation of the moving belt roller 6 - 1 .

[0077] like Figure 4 As shown, unlike the first vertical suction duct 14, the second vertical suction duct 15 needs to rotate with the balance turntable 33. Therefore, the second vertical suction duct 15 is divided into a second vertical suction duct 15-1 on the turntable and a second vertical suction duct 15-2 outside the turntable. The second vertical suction duct 15-1 on the turntable and the second vertical suction duct 15-2 outside the turntable are connected by a first rotating pipe joint 31. Similar to the second vertical suction duct 15, the tangential jet duct 16 needs to rotate with the balance turntable 33. Therefore, the tangential jet duct 16 is divided into a tangential jet duct 16-1 on the turntable and a tangential jet duct 16-2 outside the turntable. The tangential jet duct 16-1 on the turntable and the tangential jet duct 16-2 outside the turntable are connected by a second rotating pipe joint 32.

[0078] Among them, the axes of the first rotating pipe joint 31 and the second rotating pipe joint 32 coincide with the rotating shaft 33-1 of the balance turntable. Since the diameter of the tangential jet pipe 16 is small, the second rotating pipe joint 32 of the tangential jet pipe 16 can be built into the second vertical suction pipe 15 to reduce the space occupied by the pipe.

[0079] The horizontal suction part, the vertical suction part and the tangential jet part are described in detail below.

[0080] (1) The suction port 1-1 on the horizontal suction device 1 is connected to the horizontal suction pipe 13 through the horizontal suction cavity 1-2. The horizontal suction pipe 13 merges into the main return air pipe 29, and the main return air pipe 29 leads to the flow channel. The horizontal suction cavity 1-2 is a circular arc gradually expanding cavity.

[0081] like Figure 5As shown, the horizontal suction device 1 in the horizontal suction system is located inside the nozzle 5. The key design is the height H of the suction port 1-1 from the floor 8 of the station. SC and a distance L deep into the nozzle 5 SC (i.e. the distance between the suction port 1-1 and the nozzle outlet plane 5-1). Suction port height H SC It is related to the length of the curved surface of the wind tunnel nozzle 5. The longer the curved surface of the nozzle 5, the thicker the boundary layer 34-1 at the nozzle wall 5-1. In principle, the height of the suction port 1-1 must be greater than the boundary layer thickness at the nozzle outlet. The horizontal suction port 1-1 is located inside the nozzle 5, and L SC ≥100mm to avoid the occurrence of three-dimensional flow effects at the end; since the height of the suction port 1-1 is relatively small (the wind tunnel of the entire vehicle will not exceed 100mm), the suction port 1-1 is immediately followed by a circular arc-shaped gradually expanding cavity (i.e., the horizontal suction cavity 1-2) to reduce the momentum loss of the suction airflow. The horizontal suction device 1 plus the horizontal suction pipe 13, the horizontal suction flowmeter 17, the horizontal suction electric air valve 21 and the horizontal suction variable frequency fan 25 constitute the horizontal suction system I. The horizontal suction flowmeter 17 is used to monitor the horizontal suction flow, and the horizontal suction electric air valve 21 is used to control the opening and closing of the horizontal suction pipe 13. The horizontal suction pipe 13 eventually merges into the main return air duct 29. The horizontal suction airflow is guided by the main return air duct 29 to the return air port of the connecting section 12 with lower return air back pressure and returns to the interior of the flow channel.

[0082] (2) The suction port 2-1 on the first vertical suction device 2 includes a plurality of suction holes distributed on the floor 8 of the chamber between the outlet of the nozzle 5 and the balance turntable 33. The suction holes are connected to the first vertical suction pipe 14 through the first vertical suction cavity 2-2. The first vertical suction pipe 14 merges into the main return air duct 29, and the main return air duct 29 enters the flow channel. The suction port 3-1 on the second vertical suction device 3 includes a plurality of suction holes distributed on the balance turntable 33. The suction holes are connected to the second vertical suction pipe 15 through the second vertical suction cavity 3-2. The second vertical suction pipe 15 merges into the main return air duct 29, and the main return air duct 29 enters the flow channel.

[0083] like Figure 6 As shown, the thickness of the boundary layer 34-2 in the vertical suction region is δ(x)=(5x) / Re xThe thickness of the boundary layer 34-3 in the vertical suction area is δ(x-x2). The vertical suction is divided into the outer part of the turntable and the upper part of the turntable. The floor 8 of the stationary room and the balance turntable 33 are in the same plane. In order to realize the multiple suction holes required by the first vertical suction device 2 and the second vertical suction device 3, the key design lies in the ground suction porous plate and the suction chambers 2-2 and 3-2 under the porous plate. The suction hole plate should be as close to the uniform porous medium as possible under the conditions permitted by the machining technology. The suction chambers (i.e., the first vertical suction chamber 2-2 and the second vertical suction chamber 3-2) are evenly distributed and have the largest space within the space limit of the wind tunnel nozzle 5 and the balance turntable 33, so as to achieve the plane uniformity of the suction airflow. The first vertical suction device 2 and the first vertical suction pipe 14, the first vertical suction flowmeter 18, the first vertical suction electric air valve 22, and the first vertical suction variable frequency fan 26 constitute the first vertical suction system II (the vertical suction part outside the turntable); the second vertical suction device 3 and the second vertical suction pipe 15, the second vertical suction flowmeter 19, the second vertical suction electric air valve 23, and the second vertical suction variable frequency fan 27 constitute the second vertical suction system III (the vertical suction part on the turntable).

[0084] The first vertical suction flowmeter 18 is used to monitor the first vertical suction flow (outside the turntable), the second vertical suction flowmeter 19 is used to monitor the second vertical suction flow (on the turntable), the first vertical suction electric air valve 22 is used to control the opening and closing of the first vertical suction duct 14, and the second vertical suction electric air valve 23 is used to control the opening and closing of the second vertical suction duct 15. The first vertical suction duct 14 and the second vertical suction duct 15 finally merge into the main return air duct 29, and the vertical suction airflow and the horizontal suction airflow merge into the main return air duct 29 together, and are finally guided to the return air outlet of the connecting section 12 with lower return air back pressure and return to the inside of the flow channel.

[0085] (3) The jet port 4-1 of the tangential jet device 4 is a narrow slit. The jet ejected from the jet port 4-1 is consistent with the flow direction of the nozzle 5 and is close to the surface of the balance turntable 33. The jet port 4-1 is connected to the tangential jet pipe 16 through the tangential jet cavity 4-2, and the tangential jet pipe 16 is connected to the atmosphere.

[0086] like Figure 7 、 Figure 8As shown, the key design of the tangential jet device 4 lies in the position, inclination and size of the jet port 4-1. The jet port 4-1 is a narrow slit perpendicular to the axial direction of the stationary chamber 10, ensuring that the jet direction is consistent with the flow direction of the nozzle 5 and is close to the surface of the balance turntable. The jet port 4-1 is located as close as possible to the leading edge of the moving belt 6, with an inclination of approximately 1°. The width of the jet port 4-1 is approximately 1mm. The narrow slit is connected to the high-pressure cavity (i.e., the tangential jet cavity 4-2), and the bottom of the high-pressure cavity 4-2 is connected to the tangential jet pipe 16. The tangential jet device 4, the tangential jet pipe 16, the tangential jet flowmeter 20, the tangential jet electric air valve 24 and the tangential jet variable frequency fan 28 constitute the tangential jet system IV. A tangential jet flowmeter 20 is installed within the tangential jet duct 16. The jet is supplied by a tangential jet variable-frequency blower 28, with a tangential jet electric damper 24 installed at the inlet of the tangential jet variable-frequency blower 28. Because the tangential jet flow is small and negligible relative to the wind tunnel airflow, the tangential jet air is drawn from the atmosphere, and the inlet of the tangential jet duct 16 does not need to extend into the wind tunnel.

[0087] Since the return air back pressure of the connecting section 12 is relatively low, the vertical suction airflow and the horizontal suction airflow are guided to the connecting section 12 to return to the flow channel. The connecting section 12 is closer to the fan, the return air back pressure is relatively low, the system requires less power, and consumes less energy.

[0088] (4) The control module 30 performs real-time regulation and closed-loop control on the suction or jet flow of the horizontal suction system I, the first vertical suction system II, the second vertical suction system III and the tangential jet system IV.

[0089] The horizontal suction flow rate is controlled by adjusting the speed of the horizontal suction variable-frequency fan 25 connected to the horizontal suction duct 13. The flow rate signal from the horizontal suction flowmeter 17, the opening and closing signals of the horizontal suction electric damper 21, and the speed signal of the horizontal suction variable-frequency fan 25 are all connected to the control module 30 via signal cables. The specific control logic of the control module 30 is determined by the relationship between the test wind speed obtained during the wind tunnel calibration phase, the horizontal suction flow rate, and the speed of the horizontal suction variable-frequency fan 25.

[0090] The first vertical suction flow rate is controlled by adjusting the speed of the first vertical suction variable-frequency fan 26 connected to the first vertical suction duct 14 (outside the turntable). The flow rate signal from the first vertical suction flowmeter 18, the opening and closing signals of the first vertical suction electric damper 22, and the speed signal of the first vertical suction variable-frequency fan 26 are all connected to the control module 30 via signal cables. The specific control logic of the control module 30 is determined by the relationship between the test wind speed obtained during the wind tunnel calibration phase, the first vertical suction flow rate, and the speed of the first vertical suction variable-frequency fan 26.

[0091] The second vertical suction flow rate is controlled by adjusting the speed of the second vertical suction variable-frequency fan 27 connected to the second vertical suction duct 15 (on the turntable). The flow rate signal from the second vertical suction flowmeter 19, the opening and closing signals of the second vertical suction electric damper 23, and the speed signal of the second vertical suction variable-frequency fan 27 are all connected to the control module 30 via signal cables. The specific control logic of the control module 30 is determined by the relationship between the test wind speed obtained during the wind tunnel calibration phase, the second vertical suction flow rate, and the speed of the second vertical suction variable-frequency fan 27.

[0092] The tangential jet flow rate is controlled by adjusting the speed of the tangential jet variable frequency blower 28 connected to the tangential jet duct 16. The flow rate signal from the tangential jet flowmeter 20, the opening and closing signals of the tangential jet electric damper 24, and the speed signal of the tangential jet variable frequency blower 28 are all connected to the control module 30 via signal cables. The specific control logic of the control module 30 is determined by the relationship between the test wind speed, the tangential jet flow rate, and the tangential jet blower speed obtained during the wind tunnel calibration phase.

[0093] The specific principles are as follows:

[0094] During the wind tunnel commissioning phase, it is necessary to calibrate the test wind speed U0 and horizontal suction flow Q SC , the first vertical suction flow Q SUC1 (outside the turntable), the second vertical suction flow Q SUC2 (on the turntable) and tangential jet flow Q TB , and the relationship curve of the variable frequency fan speed of each system. Before the aerodynamic test is officially launched, the control module 30 first issues a command to open the electric air valves of each system; after the test starts, the control module 30 adjusts the variable frequency fan speed in real time according to the test wind speed, and determines whether the required suction or jet flow rate is achieved based on the signal measured by the flow meter. If the real-time flow signal is inconsistent with the calibrated target flow signal, the suction or jet flow rate is adjusted by controlling the variable frequency fan speed to achieve closed-loop control of the boundary layer control system. This allows the three-stage continuous combination boundary layer control system of horizontal suction, vertical suction and tangential jet to eliminate the boundary layer 34 in the wind tunnel test section without affecting the flow field quality and axial static pressure gradient in the test section.

[0095] ① Such as Figure 5 As shown, the inlet area of the horizontal suction port is defined as A SC , then the horizontal suction flow Q SC According to the horizontal suction rate η SC calculate:

[0096] Q SC =η SC ·U0·A SC

[0097] Define the suction air velocity out of the horizontal suction port as U SC , horizontal suction rate η SC The calculation formula is as follows:

[0098]

[0099] According to engineering experience, the horizontal suction rate η SC It should be controlled at around 0.9.

[0100] ② If Figure 6 As shown, the suction port area (outside the turntable) of the first vertical suction device 2 is defined as A SUC1 (Total area of multiple suction holes), the suction port area of the second vertical suction device 3 (on the turntable) is A SUC1 (total area of multiple suction holes), the suction flow rate Q of the first vertical suction device 2 is SUC1 and the suction flow Q of the second vertical suction device 3 SUC2 According to the vertical suction rate η SUC calculate:

[0101] Q SUC1 =η SUC ·U0·A SUC1

[0102] Q SUC2 =η SUC ·U0·A SUC2

[0103] It can be understood that although the vertical suction area is divided into two parts due to the balance turntable 33, the first vertical suction system and the second vertical suction system actually belong to the vertical suction part, so the suction airflow speed of the suction port is the same, and therefore the suction rate is the same.

[0104] The suction air velocity perpendicular to the suction perforated plate plane is defined as U SUC , then the vertical suction rate η SUC The calculation formula is as follows:

[0105]

[0106] According to engineering experience, the vertical suction rate η SUC It should be controlled at less than or equal to 0.03.

[0107] ③ Such as Figure 7 、 Figure 8 As shown, the tangential jet outlet area is defined as A TB , then the tangential jet flow rate Q TB According to the tangential jet rate η TB calculate:

[0108] QTB =η TB ·U0·A TB

[0109] The jet velocity of the tangential jet nozzle is defined as U TB , tangential jet rate η TB The calculation formula is as follows:

[0110]

[0111] According to engineering experience, the tangential jet rate η TB Should be controlled to be greater than 1.

[0112] In this embodiment, the three-level continuous combined boundary layer control system is as follows: Figure 9 As shown in the figure, a three-stage continuous combined boundary layer control system was used to conduct a full vehicle wind tunnel test, and the flow rate of the horizontal suction pipe 13 was about 24960m 3 / h, the flow rate of the first vertical suction pipe 14 is about 7934m 3 / h, the flow rate of the second vertical suction pipe 15 is about 3297m 3 / h, the flow rate of the tangential jet pipe 16 is about 600m 3 / h. Figure 10 This is the measured axial static pressure gradient result of the wind tunnel test section. The vertical axis represents the pressure coefficient Cp, and the horizontal axis represents the distance between the measuring point and the center of the balance. AAWT stands for aerodynamic and aero-acoustic wind tunnel. BLRS On means the boundary layer removal system is on, i.e., this application is activated. Scoop Open indicates that horizontal suction is the active suction mode. Figure 11 The results of the boundary layer measurements at the center of the turntable and at different positions on the left and right sides are shown. The vertical axis in the figure represents the height of the measuring point from the turntable surface, the horizontal axis represents the pressure coefficient Cp, U represents the measured wind speed, Y represents the lateral distance, and BLRS Off represents the boundary layer removal system off, i.e., closing this application. As can be seen from the figure, when the three-stage continuous combined boundary layer control system is closed, the boundary layer thickness at the measured position is about 55mm. When the three-stage continuous combined boundary layer control system is turned on, the boundary layer thickness is basically zero; and the axial static pressure gradient of the test section does not exceed 0.005 in the area 4m before and after the center of the turntable.

[0113] The above describes in detail the preferred embodiments of the present invention. It should be understood that those skilled in the art can make numerous modifications and variations based on the concepts of the present invention without inventive effort. Therefore, any technical solutions that can be derived by those skilled in the art through logical analysis, reasoning, or limited experimentation based on the concepts of the present invention and the prior art should be within the scope of protection defined by the claims.

Claims

1. A three-stage continuous combined boundary layer control system for an automobile wind tunnel, characterized in that: An automotive wind tunnel composed of a stationary chamber and a flow channel, comprising a horizontal suction system, a first vertical suction system, a second vertical suction system, a tangential jet system, and a control module; The two ends of the flow channel are respectively provided with a nozzle and a collecting port, the nozzle is used to eject airflow, and the collecting port is used to recover airflow. The nozzle and the collecting port are located at both ends of the stationary chamber. A rotatable balance turntable is provided on the floor of the stationary chamber, and the test model is placed on the balance turntable. A moving belt is provided on the balance turntable, and the moving belt is located at the bottom of the test model. The horizontal suction system includes a horizontal suction device, a horizontal suction pipeline, a horizontal suction flow meter, a horizontal suction electric air valve and a horizontal suction variable frequency fan; The first vertical suction system includes a first vertical suction device, a first vertical suction pipeline, a first vertical suction flow meter, a first vertical suction electric air valve and a first vertical suction variable frequency fan; The second vertical suction system includes a second vertical suction device, a second vertical suction pipeline, a second vertical suction flow meter, a second vertical suction electric air valve and a second vertical suction variable frequency fan; The tangential jet system includes a tangential jet device, a tangential jet pipeline, a tangential jet flowmeter, a tangential jet electric air valve and a tangential jet variable frequency fan; The control module is connected to the horizontal suction flowmeter, the horizontal suction electric air valve, the horizontal suction variable frequency fan, the first vertical suction flowmeter, the first vertical suction electric air valve, the first vertical suction variable frequency fan, the second vertical suction flowmeter, the second vertical suction electric air valve, the second vertical suction variable frequency fan, the tangential jet flowmeter, the tangential jet electric air valve and the tangential jet variable frequency fan; The suction port of the horizontal suction device is located in the nozzle, the suction port of the first vertical suction device is located on the ground between the nozzle outlet and the balance turntable, the suction port of the second vertical suction device is located on the balance turntable, and the jet port of the tangential jet device is located between the suction port of the second vertical suction device and the moving belt; The suction port on the horizontal suction device is connected to the horizontal suction pipe through the horizontal suction cavity, the horizontal suction pipe merges into the main return air pipe, the main return air pipe leads to the flow channel, and the horizontal suction cavity is a circular arc gradually expanding cavity; The suction port on the first vertical suction device includes a plurality of suction holes distributed on the ground between the nozzle outlet and the balance turntable, the suction holes are connected to the first vertical suction pipe through the first vertical suction cavity, the first vertical suction pipe merges into the main return air pipe, and the main return air pipe leads to the flow channel; The suction port on the second vertical suction device includes a plurality of suction holes distributed on the balance turntable. The suction holes are connected to the second vertical suction duct through the second vertical suction cavity. The second vertical suction duct merges into the main return air duct, and the main return air duct leads to the flow channel.

2. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: The collecting port is connected to the diffusion section, the diffusion section is connected to the connecting section, the connecting section is connected to the nozzle, and the total return air duct leads to the connecting section.

3. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: The jet outlet of the tangential jet device is a narrow slit. The jet ejected from the jet outlet is consistent with the direction of the incoming flow from the jet outlet and is close to the surface of the balance turntable. The jet outlet is connected to the tangential jet pipe through the tangential jet cavity, and the tangential jet pipe is connected to the atmosphere.

4. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: Pre-calibrate the test wind speed U0 and horizontal suction flow Q SC The control module controls the horizontal suction variable frequency fan based on the horizontal suction flow meter signal and the test wind speed U0 to adjust the horizontal suction flow to the preset horizontal suction flow, the horizontal suction flow Q SC The calculation formula is as follows: Q SC =the SC ·U0·A SC Among them, η SC Indicates the suction rate of the suction port of the horizontal suction device, A SC represents the inlet area of the suction port of the horizontal suction device, U0 represents the test wind speed, η SC The calculation formula is: Among them, U SC Indicates the suction airflow velocity at the suction port of a horizontal suction device.

5. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: Pre-calibrate the test wind speed U0 and the first vertical suction flow Q SUC1 The control module controls the first vertical suction variable frequency fan based on the first vertical suction flow meter signal and the test wind speed U0 to adjust the first vertical suction flow to the preset first vertical suction flow. The first suction flow Q SUC1 The calculation formula is as follows: Q SUC1 =the SUC1 ·U0·A SUC1 Among them, η SUC1 represents the suction rate of the suction port of the first suction device, A SUC1 represents the inlet area of the suction port of the first suction device, U0 represents the test wind speed, η SUC1 The calculation formula is: Among them, U SUC1 Indicates the suction airflow velocity of the suction port of the first vertical suction device.

6. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: Pre-calibrate the test wind speed U0 and the second vertical suction flow Q SUC2 The control module controls the second vertical suction variable frequency fan based on the second vertical suction flow meter signal and the test wind speed U0 to adjust the second vertical suction flow to the preset second vertical suction flow. The second suction flow Q SUC2 The calculation formula is as follows: Q SUC2 =the SUC2 ·U0·A SUC2 Among them, η SUC2 A represents the suction rate of the suction port of the second suction device, SUC2 represents the inlet area of the suction port of the second suction device, U0 represents the test wind speed, η SUC2 The calculation formula is: Among them, U SUC2 Indicates the suction airflow velocity of the suction port of the second vertical suction device.

7. The three-stage continuous combined boundary layer control system for an automobile wind tunnel according to claim 1, characterized in that: Pre-calibrate the test wind speed U0 and tangential jet flow Q TB The control module controls the tangential jet variable frequency fan based on the tangential jet flowmeter signal and the test wind speed U0 to adjust the tangential jet flow rate to the preset tangential jet flow rate, the tangential jet flow rate Q TB The calculation formula is as follows: Q TB =the TB ·U0·A TB Among them, η TB Indicates the jet rate of the jet orifice of the tangential jet device, A TB represents the outlet area of the jet port of the tangential jet device, U0 represents the test wind speed, η TB The calculation formula is: Among them, U TB Indicates the jet air flow velocity at the jet outlet of the tangential jet device.

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