Variable-mach-number wind tunnel experimental device based on jet and suction structure
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI UNIV OF TECH
- Filing Date
- 2023-08-11
- Publication Date
- 2026-06-30
Smart Images
Figure CN117030182B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of aerodynamic experimental devices, specifically to a variable Mach number wind tunnel experimental device based on a jet and suction structure. Background Technology
[0002] With the continuous development of high Mach number aircraft, wide-range flight is an essential capability for new aircraft. Changes in flight Mach number lead to changes in flight performance, and accurate experimental data requires ground simulation equipment capable of handling multiple flight Mach numbers. In supersonic nozzles, different Mach numbers correspond to different expansion ratios, i.e., the ratio of nozzle exit area to throat area. Currently, research on variable Mach number wind tunnel schemes in the nozzle section mainly focuses on flexible-walled and symmetrically opening / closing types. The flexible-walled variable Mach number wind tunnel scheme uses a series of pistons moving up and down to drive controllable deformation of the nozzle wall, thereby changing the Mach number of the nozzle flow field. The symmetrically opening / closing variable Mach number wind tunnel scheme uses symmetrically symmetrical solid-walled nozzles. The nozzle profile rotates around one end of the nozzle as an axis of rotation, and the other end moves up and down to change the nozzle's contraction ratio, thus altering the nozzle flow field Mach number.
[0003] The existing variable Mach number wind tunnel schemes have the following main defects: (1) Complex mechanical mechanism operation: If the nozzle adopts a flexible wall, the multi-point actuation mechanism and control method of the flexible wall are very complex, making it difficult to continuously and accurately control the flow field of the nozzle; (2) The change of the profile leads to the distortion of the flow field: If the nozzle adopts a rigid rotating wall, the change of the selected profile will lead to the distortion of the flow field, making it difficult for a single nozzle to exceed two Mach numbers in the variable Mach range, and it is difficult to cross high Mach numbers. (3) The actual mechanism is subject to time constraints during operation, and the process of changing the Mach number is relatively long, making it difficult to achieve the change of Mach number in a short period of time. Summary of the Invention
[0004] The purpose of this invention is to overcome the above-mentioned defects and provide a variable Mach number wind tunnel experimental device based on a jet and suction structure.
[0005] To achieve the above objectives, the present invention adopts the following technical solution: a wind tunnel comprising a contraction section, an inlet section, a nozzle section, and an experimental section connected sequentially, wherein the central axes of the contraction section, inlet section, nozzle section, and experimental section coincide, and the internal flow channels of the contraction section, inlet section, nozzle section, and experimental section are sequentially connected to form the gas flow channel of the wind tunnel; the nozzle section is surrounded by symmetrically arranged left and right side plates and symmetrically arranged upper and lower profiles, wherein the adjacent end faces of the upper and lower profiles are convex arc surfaces, and the inner surface of the nozzle section... The flow channel includes a nozzle contraction section, a throat, and a nozzle expansion section arranged in sequence. The upper and lower profiles corresponding to the throat are respectively provided with rows of circular air holes. The circular air holes are connected to a jet suction device. The jet suction device includes an air collection chamber, a pipe connected to the air collection chamber, and a solenoid valve connected to the end of the pipe. By opening and closing the solenoid valve orifice, a pneumatic throat can be formed in the nozzle section. By changing the ratio of the throat area to the area at the nozzle expansion section outlet, the Mach number of the flow channel inside the experimental section can be varied.
[0006] It also includes a gas source device, which includes an air compressor, a first pressure storage tank, a first air pipe connecting the air compressor and the first pressure storage tank, a second air pipe connecting the first pressure storage tank and the gas collection chamber, a one-way valve installed on the first air pipe, and a pressure reducing valve installed on the second air pipe, wherein the second air pipe is a rigid pipe.
[0007] It also includes a vacuum device, which includes a vacuum pump, a second pressure storage tank, a third gas pipe connecting the vacuum pump and the second pressure storage tank, a vacuum valve installed on the third gas pipe, and a fourth gas pipe connecting the second pressure storage tank and the internal flow channel of the nozzle section.
[0008] It also includes an air tank, which is connected to the contraction section via a fifth air pipe, and the fifth air pipe is equipped with a one-way ball valve.
[0009] The experimental section includes a Pitot tube, one end of which has a pressure measuring hole is located in the internal flow channel of the experimental section. Pressure sensors are respectively installed on the static pressure tube and the total pressure tube of the Pitot tube, and the pressure sensors are connected to the feedback control system.
[0010] The experimental section is generally square, with a groove on the upper surface facing downwards. The bottom of the groove has a notch that communicates with the internal flow channel of the experimental section. The notch is sealed to the inside and outside of the experimental section by a sealing plate and a sealing ring. The Pitot tube passes through the sealing plate and forms a seal with the sealing plate by an O-ring. The pressure sensor and the feedback control system are connected by wires.
[0011] The upper and lower profiles each include a first profile corresponding to the nozzle contraction section, a second profile corresponding to the throat, and a third profile corresponding to the nozzle expansion section. The second profile includes a first fixing part connected to the first profile, a second fixing part connected to the third profile, an arc-shaped plate connected to the bottom ends of the first and second fixing parts, and a cover plate connected to the top of the first and second fixing parts. The air collection chamber is connected to the lower surface of the cover plate through a first fixing plate and a second fixing plate, and the cover plate is provided with an air inlet that communicates with the interior of the air collection chamber.
[0012] The pipeline includes a first-stage manifold, a second-stage manifold, and a third-stage manifold arranged sequentially from top to bottom. The first-stage manifold is connected to the gas collection chamber via a flexible hose, and the first-stage manifold is connected to the second-stage manifold, and the second-stage manifold is connected to the third-stage manifold via rigid pipes.
[0013] The solenoid valve is a two-position three-way valve. The solenoid valve includes a first through hole and a second through hole at the top, and a third through hole, a fourth through hole, and a fifth through hole at the bottom. The first through hole is connected to the outlet of the third-stage manifold through a rigid pipe, and the diameter of each through hole on the solenoid valve is larger than the diameter of the circular air hole.
[0014] The solenoid valves are arranged in multiple rows side by side. The arc plate is provided with blind slots for installing the solenoid valves. Any two rows of solenoid valves are selected to spray and suck at the throat. The circular air hole is opened at the bottom of the blind slot.
[0015] The internal flow channel of the contraction section is a funnel-shaped flow channel with a large opening and a small outlet. The internal flow channel of the air inlet section is a rectangular flow channel. The internal flow channel of the nozzle section is a contraction-expansion type flow channel. The internal flow channel of the experimental section is a rectangular flow channel. The air inlet section is connected to the contraction section through a first flange. The air inlet section is connected to the nozzle section through a second flange. The nozzle section is connected to the experimental section through a third flange. The wind tunnel is placed on an experimental support platform.
[0016] The beneficial effects of this invention are as follows:
[0017] 1. This invention uses circular air holes at both ends to inject gas, creating an aerodynamic throat within the nozzle section's internal flow channel. This alters the ratio of the nozzle section's outlet area to the throat area, thus achieving a change in the Mach number during the experimental section. Compared to nozzle sections with flexible walls, this invention eliminates complex actuation mechanisms; compared to nozzle sections with rigid rotating walls, the flow field is more uniform; and due to the higher jet velocity and shorter time response, the time history of Mach number changes is correspondingly shortened.
[0018] 2. In this invention, the diameter of the circular air holes is small and they are densely arranged. Each groove is separated by a baffle, and each groove controls only 4 circular holes. At the same time, the three-stage manifold valves are evenly arranged, which can avoid the problem of uneven airflow and the problem of different timing during injection / suction.
[0019] 3. The present invention uses only one Pitot tube, and the pressure measuring hole is arranged at the center of the experimental section. It only measures the pressure of the gas at the center of the experimental section. The number of Pitot tubes can be changed according to the specific situation to measure the pressure in different vertical directions.
[0020] 4. The present invention has strong applicability, key components can be quickly disassembled, and the modular assembly process enables damaged parts to be quickly replaced. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the structure of the present invention;
[0022] Figure 2 This is a schematic diagram of the external structure of the wind tunnel of this invention;
[0023] Figure 3 This is a schematic diagram of the internal structure of the wind tunnel of this invention;
[0024] Figure 4 This is an exploded structural diagram of the nozzle section of the present invention;
[0025] Figure 5 This is a schematic diagram of the arc-shaped plate of the present invention. Figure 1 ;
[0026] Figure 6 yes Figure 5 Enlarged view of part A;
[0027] Figure 7 This is a schematic diagram of the arc-shaped plate of the present invention. Figure 2 ;
[0028] Figure 8 This is a cross-sectional view of the nozzle section of the present invention;
[0029] Figure 9 This is a schematic diagram of the structure of the profile on the nozzle section of the present invention;
[0030] Figure 10 This is an exploded structural diagram of the profile on the nozzle section of the present invention;
[0031] Figure 11 This is a schematic diagram of the structure of the jet suction device of the present invention;
[0032] Figure 12 A schematic diagram of the pipe structure of this invention;
[0033] Figure 13This is a schematic diagram of the structure of the solenoid valve of the present invention;
[0034] Figure 14 This is a schematic diagram of the bottom structure of the solenoid valve of the present invention;
[0035] Figure 15 This is a diagram showing the installation of the solenoid valve and the plate of the present invention.
[0036] Figure 16 This is a schematic diagram of the experimental section of the present invention;
[0037] Figure 17 This is a schematic diagram of the exploded structure of the experimental section of the present invention;
[0038] Figure 18 This is a partial schematic diagram of the experimental section of the present invention. Figure 1 ;
[0039] Figure 19 This is a partial schematic diagram of the experimental section of the present invention. Figure 2 ;
[0040] Figure 20 This is a partial exploded view of the experimental section of the present invention;
[0041] Figure 21 These are the flow field cloud diagram and X-Ma diagram of the nozzle section when the present invention does not have a jet suction device;
[0042] Figure 22 These are the flow field cloud diagrams and X-Ma diagrams of the nozzle section and experimental section in Embodiment 1 of the present invention;
[0043] Figure 23 These are the flow field cloud diagrams and X-Ma diagrams of the nozzle section and experimental section in Embodiment 2 of the present invention;
[0044] Figure 24 These are the flow field cloud diagrams and X-Ma diagrams of the nozzle section and experimental section in Embodiment 3 of the present invention;
[0045] Figure 25 These are the flow field cloud diagrams and X-Ma diagrams of the nozzle section and experimental section in Embodiment 4 of the present invention.
[0046] The reference numerals in the above figures are as follows: 1. Contraction section; 2. Inlet section; 3. Nozzle section; 31. Left side plate; 32. Right side plate; 33. Upper profile; 33. First profile; 331. Second profile; 332. First fixing part; 3322. Second fixing part; 3323. Arc plate; 3324. Cover plate; 3325. First fixing plate; 3326. Second fixing plate; 3327. Inlet hole; 3328. Blind groove; 3329. Circular air hole; 333. Third profile; 34. Lower profile; 35. Nozzle contraction section; 36. Throat; 37. Nozzle expansion section; 38. Solenoid valve; 381. First through hole; 382. Second through hole; 383. Third through hole; 384. Fifth through hole; Through hole 385, flat plate 386, gas collecting chamber 39, first-stage manifold 391, second-stage manifold 392, third-stage manifold 393, experimental section 4, Pitot tube 41, pressure measuring hole 42, static pressure pipe 43, total pressure pipe 44, pressure sensor 45, feedback control system 46, groove 47, sealing plate 471, sealing ring 472, O-ring 48, wire 49, air compressor 51, first pressure storage tank 52, one-way valve 53, pressure reducing valve 54, vacuum pump 61, second pressure storage tank 62, vacuum valve 63, gas tank 7, one-way ball valve 71, first flange 81, second flange 82, third flange 83, experimental support platform 84. Detailed Implementation
[0047] The present invention will be further described below with reference to the accompanying drawings:
[0048] like Figure 1 , Figure 2 , Figure 3 The wind tunnel experimental apparatus shown is a variable Mach number wind tunnel based on a jet and suction structure. It comprises a wind tunnel consisting of a contraction section 1, an inlet section 2, a nozzle section 3, and an experimental section 4 connected sequentially, and is placed on an experimental support platform 84. The central axes of the contraction section 1, inlet section 2, nozzle section 3, and experimental section 4 coincide, and their internal flow channels are sequentially connected to form the gas flow channels of the wind tunnel. Specifically, the internal flow channel of the contraction section 1 is a funnel-shaped channel with a large opening and a small outlet; the internal flow channel of the inlet section 2 is a rectangular channel; the internal flow channel of the nozzle section 3 is a contraction-expansion type channel; and the internal flow channel of the experimental section 4 is a rectangular channel. The inlet section 2 is connected to the contraction section 1 via a first flange 81, the inlet section 2 is connected to the nozzle section 3 via a second flange 82, and the nozzle section 3 is connected to the experimental section 4 via a third flange 83.
[0049] Specifically, such as Figure 4 , Figure 8 , Figure 9 , Figure 10As shown, nozzle section 3 is formed by symmetrically arranged left side plate 31, right side plate 32, and symmetrically arranged upper profile 33 and lower profile 34. The end faces of the upper profile 33 and lower profile 34 that are close to each other are convex arc surfaces, that is, the convex direction of the arc surfaces points to the central axis of the nozzle section. The internal flow channel of nozzle section 3 includes a nozzle contraction section 35, a throat 36, and a nozzle expansion section 37 arranged in sequence. Correspondingly, the upper profile 33 and lower profile 34 each include a first profile 331 corresponding to the nozzle contraction section 35, a second profile 332 corresponding to the throat 36, and a third profile 333 corresponding to the nozzle expansion section 37. More specifically, the second profile 332 includes a first fixing part 3321 connected to the first profile 331, a second fixing part 3322 connected to the third profile 333, an arc-shaped plate 3323 connected to the bottom ends of the first fixing part 3321 and the second fixing part 3322, and a cover plate 3324 connected to the top of the first fixing part 3321 and the second fixing part 3322. The air collecting chamber 39 is connected to the lower surface of the cover plate 3324 through the first fixing plate 3325 and the second fixing plate 3326, and the cover plate 3324 is provided with an air inlet 3327 communicating with the interior of the air collecting chamber 39.
[0050] Furthermore, such as Figure 5 , Figure 6 , Figure 7 As shown, the upper profile 33 and lower profile 34, corresponding to the throat 36, are respectively provided with rows of circular air holes 3329. The circular air holes 3329 are connected to the jet suction device. Specifically, multiple blind slots 3328 for installing solenoid valves 38 are distributed in rows on the arc plate 3323 of the second profile, and the circular air holes 3329 are opened at the bottom of the blind slots 3328.
[0051] like Figure 11 As shown, the jet suction device includes a gas collection chamber 39, a pipe connected to the gas collection chamber 39, and a solenoid valve 38 connected to the end of the pipe. By opening and closing the orifice of the solenoid valve 38, a pneumatic throat can be formed in the nozzle section 3. In use, by changing the ratio of the area of the throat 36 to the area at the outlet of the nozzle expansion section 37, the Mach number of the flow channel inside the experimental section 4 can be changed.
[0052] Specifically, such as Figure 12 As shown, the pipeline includes a first-stage manifold 391, a second-stage manifold 392, and a third-stage manifold 393 arranged sequentially from top to bottom. The first-stage manifold 391 is connected to the gas collection chamber 39 via a flexible hose. The first-stage manifold 391 and the second-stage manifold 392, as well as the second-stage manifold 392 and the third-stage manifold 393, are all connected by rigid pipes. Additionally, as... Figure 13 , Figure 14 , Figure 15As shown, the solenoid valve 38 is a two-position three-way valve, model 3V320-10. The solenoid valve 38 includes a first through-hole 381 and a second through-hole 382 at the top, and a third through-hole 383, a fourth through-hole 384, and a fifth through-hole 385 at the bottom. The first through-hole 381 is connected to the outlet of the third-stage manifold 393 via a rigid pipe. The solenoid valve 38 is fixed to the upper part of the blind slot 3328 by a plate 386, which has through-holes that correspond to the positions of the third through-hole 383, the fourth through-hole 384, and the fifth through-hole 385.
[0053] Multiple rows of solenoid valves 38 are arranged side by side, and blind slots 3328 for mounting the solenoid valves 38 are provided on the arc-shaped plate 3323. Preferably, in this invention, a total of 25 rows of solenoid valves 38 are arranged, with 10 solenoid valves 38 in each row. Correspondingly, 25 rows of blind slots 3328 are also arranged, with 10 blind slots 3328 in each row. Here, each row refers to the direction perpendicular to the axis of the nozzle section 3. The bottom of each blind slot 3328 is provided with 4 circular air holes 3329 with a diameter of 1.2 mm, and each blind slot 3328 controls 4 circular air holes 3329. In actual use, the number of blind slots 3328 and the number of circular air holes 3329 controlled by the blind slots 3328 can be set according to specific working conditions. This invention only shows one setting method, which is determined according to the bottom surface area of the nozzle.
[0054] Of the 25 rows of solenoid valves 38, any two rows are selected for jetting and suction at the throat 36. That is, only two rows of solenoid valves 38 are operational: one for jetting and the other for suction. The remaining 23 rows are used to adjust the positions of jetting and suction. For example, closing the row of solenoid valves originally used for jetting and opening different rows for jetting adjusts the jetting position; the same applies to suction. At startup, the first port 381, the fourth port 384, and the fifth port 385 of the solenoid valves in the jetting row are open, while the second port 382 and the third port 383 are closed. Similarly, the second port 382, the third port 383, and the fourth port 384 of the solenoid valves in the suction row are open, while the first port 381 and the fifth port 385 are closed. When it is necessary to adjust the position of the jet or suction circular air hole, the solenoid valve 38 controls the opening and closing of the port according to the feedback signal. Selecting two air ports at the bottom for jet or suction can make the gas flow distribution more uniform when each row of solenoid valves is performing suction or jet.
[0055] Preferably, in this invention, the diameter of the circular air holes 3329 is 1.2 mm. The small diameter and dense arrangement result in more uniform flow when the gas is injected into the internal flow channel of the nozzle section 3. The diameter of each through hole on the solenoid valve 38 is 3.15 mm. The diameter of each through hole on the solenoid valve 38 is larger than the diameter of the circular air holes 3329. Thus, when the solenoid valve 38 is opened, the high-pressure gas tends to contract when it is injected into the internal flow channel of the nozzle section 3.
[0056] like Figure 16 , Figure 17 , Figure 18 , Figure 19 , Figure 20 As shown, specifically, experimental section 4 includes a Pitot tube 41. One end of the Pitot tube 41 with a pressure measuring port 42 is located in the internal flow channel of experimental section 4. Pressure sensors 45 are respectively installed on the static pressure tube 43 and the total pressure tube 44 of the Pitot tube 41. The pressure sensors 45 are connected to the feedback control system 46. The central axis of the end of the Pitot tube 41 located in the internal flow channel of experimental section 4 coincides with the central axis of the internal flow channel of experimental section 4. The pressure sensor 45 in this invention is a small pressure sensor, using the Shanghai Tianmu NS-2 sensor, with a measurement range of -100kPa to 35000kPa. The static pressure tube 43 is used to measure the static pressure of the gas, and the total pressure tube 44 is used to measure the total pressure of the gas. The measured pressure is converted into an electrical signal by the pressure sensor 45 and input to the feedback control system 46.
[0057] The experimental section 4 is square in shape. The upper surface of the experimental section 4 has a groove 47 facing downwards, and the bottom of the groove 47 has a notch that communicates with the internal flow channel of the experimental section 4. The notch is sealed to the inside and outside of the experimental section 4 by a sealing plate 471 and a sealing ring 472. The Pitot tube 41 is installed through the sealing plate 471, and the Pitot tube 41 forms a seal with the sealing plate 471 by an O-ring 48 to ensure airtightness. The pressure sensor 45 is connected to the feedback control system 46 by a wire 49.
[0058] Furthermore, the present invention also includes a gas source device, which includes an air compressor 51, a first pressure air tank 52, a first air pipe connecting the air compressor 51 and the first pressure air tank 52, a second air pipe connecting the first pressure air tank 52 and the air collecting chamber 39, a one-way valve 53 disposed on the first air pipe, and a pressure reducing valve 54 disposed on the second air pipe. The second air pipe is a rigid pipe. In the present invention, two parallel second air pipes are arranged, that is, the gas coming out of the first pressure air tank 52 is divided into two paths through the two second air pipes, one path communicating with the air inlet 3327 on the upper profile and the other path communicating with the air inlet 3327 on the lower profile.
[0059] Furthermore, the present invention also includes a vacuum device, which includes a vacuum pump 61, a second pressure storage tank 62, a third air pipe connecting the vacuum pump 61 and the second pressure storage tank 62, a vacuum valve 63 disposed on the third air pipe, and a fourth air pipe connecting the second pressure storage tank 62 and the internal flow channel of the nozzle section 3.
[0060] Furthermore, the present invention also includes an air tank 7, which is connected to the contraction section 1 via a fifth air pipe, and a one-way ball valve 71 is provided on the fifth air pipe.
[0061] The working principle and process of this invention are as follows:
[0062] The air intake section 2 and the contraction section 1 of this invention are used to provide the airflow for the experiment. The nozzle section 3 is equipped with a jet suction device that forms a pneumatic throat in the nozzle to achieve changes in Mach number. The experimental section is equipped with a pressure sensor and a feedback control system. The static pressure and total pressure of the airflow are measured by a Pitot tube, the Mach number of the airflow in the experimental section is calculated, and the data is fed back to the solenoid valve control unit to control the position of the jet / suction port and the working pressure.
[0063] Before the experiment, air compressor 51 generates high-pressure gas, which enters the first pressure storage tank 52 through one-way valve 53. Vacuum pump 61 generates vacuum gas, which enters the second pressure storage tank 62 through vacuum valve 63. During the experiment, one-way ball valve 71 is opened, and airflow enters the constriction section 1 through the air tank 7. After passing through the intake section 2 and nozzle section 3, the Mach number in the experimental section 4 reaches a stable value. The static pressure and total pressure are measured by Pitot tube 41, and the measured pressure is converted into an electrical signal by pressure sensor 45. The electrical signal enters the feedback control system 46. Since a normal shock wave is formed in front of Pitot tube 41, the feedback control system 46 converts the pressure signal into a Mach number signal according to the airflow relationship before and after the shock wave and feeds it back to the control unit of solenoid valve 38, controlling solenoid valve 38 to open. At the same time, the second pressure storage tank 62 is opened, so that the internal cavity of nozzle section 3 achieves a stable Mach number. Empty; then open the first pressure storage tank 52, and high-pressure gas enters the gas collecting chamber 39 through the second gas pipe and the pressure reducing valve 54. The high-pressure gas in the gas collecting chamber 39 is injected into the internal flow channel of the nozzle section 3 after passing through the three-stage manifold and the solenoid valve 38. At this time, the solenoid valve 38 used for spraying sprays high-pressure gas into the internal flow channel of the nozzle section 3, and the solenoid valve 38 used for suction draws gas out from the internal flow channel of the nozzle section 3, forming a pneumatic throat, which changes the ratio of the outlet area of the nozzle section 3 to the throat area, thus achieving a variable Mach number. When the Mach number reaches a stable value, the static pressure and total pressure are measured by the Pitot tube 41 and converted into an electrical signal by the pressure sensor 45. The electrical signal is converted into a Mach number signal by the feedback control system 46 and fed back to the control unit of the solenoid valve, which controls the change of the injection position of the solenoid valve 38 and the working pressure, and repeats the above operation.
[0064] The relationship between the airflow before and after the shock wave in the above principle is as follows:
[0065]
[0066] Where: p t p1 is the static pressure, Ma1 is the total pressure behind the normal shock wave, and Ma1 is the Mach number behind the normal shock wave. ∞ For the total pressure at the front of the normal shock wave, Ma ∞ γ is the Mach number of the normal shock wave front, and γ is the absolute pressure coefficient, which is taken as 1.4.
[0067] like Figure 21 As shown, in the absence of a jet-suction device in this invention, the Mach number of the entire flow field changes as follows: Figure 21 As shown in (a), the Mach number cloud map near its throat is as follows: Figure 21 As shown in (b), the Mach number of the experimental section is as follows: Figure 21 As shown in (c), its Mach number variation curve is as follows: Figure 21 As shown in (d), its mainstream region Mach number is 2.8.
[0068] Example 1:
[0069] Air compressor 51 generates high-pressure gas, which enters the first pressure storage tank 52 through one-way valve 53. Vacuum pump 61 generates vacuum gas, which enters the second pressure storage tank 62 through vacuum valve 63. During the experiment, one-way ball valve 71 is opened, and airflow at 1 atmosphere (hereinafter referred to as atm) enters the contraction section 1 through the air inlet section 2 and nozzle section 3, bringing the Mach number in the experimental section 4 to 2.8 Ma. The static pressure and total pressure are measured by Pitot tube 41, and the measured pressure is converted into an electrical signal by pressure sensor 45. The electrical signal enters the feedback control system 46, which converts the pressure signal into a Mach number signal according to the airflow relationship before and after the shock wave and feeds it back to the control unit of solenoid valve 38, controlling solenoid valve 38 to open. At the same time, the second pressure storage tank 62 is opened, creating a vacuum in the internal cavity of nozzle section 3. Then the first pressure storage tank 52 is opened, and the high-pressure gas enters the second pressure storage tank 62 through the vacuum valve 63. The two gas pipes enter the gas collecting chamber 39 through the pressure reducing valve 54. The high-pressure gas in the gas collecting chamber 39 is injected into the internal flow channel of the nozzle section 3 after passing through the three-stage manifold and the solenoid valve 38. At this time, the solenoid valve 38 used for jetting injects high-pressure gas into the internal flow channel of the nozzle section 3. The injected high-pressure gas has an absolute pressure of 1.8 atm. The solenoid valve 38 used for suction draws gas out of the internal flow channel of the nozzle section 3. The suction air pressure is 0.1 atm, forming a pneumatic throat, which changes the ratio of the nozzle section 3 outlet area to the throat area, thus achieving a variable Mach number. When the Mach number reaches 3.5 Ma, the static pressure and total pressure are measured by the Pitot tube 41 and converted into an electrical signal by the pressure sensor 45. The electrical signal is converted into a Mach number signal by the feedback control system 46 and fed back to the control unit of the solenoid valve, which controls the change of the injection position and working pressure of the solenoid valve 38, and repeats the above operation.
[0070] like Figure 22 As shown, the Mach number of the entire flow field changes as follows: Figure 22 As shown in (a); the Mach number cloud map near its throat is as follows: Figure 22 As shown in (b), the double arrows in the figure represent the position of the formed aerodynamic throat and the original throat position, respectively. It can be seen that this embodiment achieves throat forward movement and changes the area ratio; the Mach number of the experimental section is as follows. Figure 22As shown in (c), it can be seen that the Mach number variation range is larger compared to the case without jet / suction, and its Mach number variation curve is as follows. Figure 22 As shown in (d), its mainstream region Mach number is 3.5.
[0071] Example 2:
[0072] like Figure 23 As shown, based on Example 1, the airflow pressure drawn by the solenoid valve is changed to absolute pressure of 0.4 atm, and the operation of Example 1 is repeated. At this time, the Mach number of the entire flow field changes as follows: Figure 23 As shown in (a); the Mach number cloud map near its throat is as follows: Figure 23 As shown in (b), the two double arrows in the figure represent the position of the formed aerodynamic throat and the original throat position, respectively. It can be seen that this embodiment achieves throat forward movement and changes the area ratio; the Mach number of the experimental section is as follows. Figure 23 As shown in (c), it can be seen that the Mach number variation range is larger compared to the case without jet / suction, and its Mach number variation curve is as follows. Figure 23 As shown in (d), its mainstream region Mach number is 3.4.
[0073] Example 3:
[0074] like Figure 24 As shown, based on Example 1, the position of the circular air hole used for suction was adjusted (before adjustment, it was located at x-axis -0.004m, see [reference]). Figure 22 (b), after adjustment, located at -0.005m on the x-axis), repeat the operation of Example 1. At this time, the Mach number of the entire flow field changes as follows: Figure 24 As shown in (a); the Mach number cloud map near its throat is as follows: Figure 24 As shown in (b), the two double arrows in the figure represent the position of the formed pneumatic throat and the adjusted position of the suction circular orifice, respectively. It can be seen that this embodiment achieves forward movement of the throat and changes the area ratio; the Mach number of the experimental section is as follows: Figure 24 As shown in (c), it can be seen that adjusting the suction port in the opposite direction of the flow direction results in a decrease in the Mach number, as illustrated in the Mach number change curve. Figure 24 As shown in (d), its mainstream Mach number is 3.4, which is 0.1 lower than that before adjustment.
[0075] Example 4:
[0076] like Figure 25 As shown, based on Example 1, the position of the circular air hole used for the jet was adjusted (before adjustment, it was located at x-axis -0.01m, see...). Figure 22 (b), after adjustment, located at -0.016m on the x-axis), repeat the operation of Example 1. At this time, the Mach number of the entire flow field changes as follows: Figure 25 As shown in (a); the Mach number cloud map near its throat is as follows: Figure 25As shown in (b), the two double arrows in the figure represent the position of the formed aerodynamic throat and the adjusted position of the jet orifice, respectively. It can be seen that this embodiment achieves the forward movement of the throat and changes the area ratio; the Mach number of the experimental section is as follows: Figure 25 As shown in (c), it can be seen that adjusting the jet nozzle in the opposite direction of the flow direction increases the Mach number, and the Mach number change curve is as follows. Figure 25 As shown in (d), its mainstream Mach number is 3.7, which is 0.2 higher than that before adjustment.
[0077] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. Various modifications and improvements made by those skilled in the art to the technical solutions of the present invention without departing from the spirit of the present invention should fall within the protection scope defined by the claims of the present invention.
Claims
1. A variable Mach number wind tunnel experimental device based on a jet and suction structure, characterized in that: The wind tunnel comprises a converging section (1), an inlet section (2), a nozzle section (3), and an experimental section (4) connected in sequence. The central axes of the converging section (1), the inlet section (2), the nozzle section (3), and the experimental section (4) coincide, and the internal flow channels of the converging section (1), the inlet section (2), the nozzle section (3), and the experimental section (4) are connected in sequence to form the gas flow channels of the wind tunnel. The nozzle section (3) is surrounded by a symmetrically arranged left side plate (31), a right side plate (32), and symmetrically arranged upper profile (33) and lower profile (34). The end faces of the upper profile (33) and the lower profile (34) that are close to each other are convex arc surfaces. The internal flow channels of the nozzle section (3) include sequentially arranged... The nozzle contraction section (35), throat (36) and nozzle expansion section (37) are provided with rows of circular air holes (3329) on the arc surfaces of the upper profile (33) and lower profile (34) corresponding to the throat (36). The circular air holes (3329) are connected to the jet suction device. The jet suction device includes an air collection chamber (39), a pipe connected to the air collection chamber (39) and a solenoid valve (38) connected to the end of the pipe. By switching the opening and closing of the solenoid valve (38) orifice, a pneumatic throat can be formed in the nozzle section (3). By changing the ratio of the area of the throat (36) to the area at the outlet of the nozzle expansion section (37), the Mach number of the internal flow channel of the experimental section (4) can be changed. It also includes an air source device, which includes an air compressor (51), a first pressure storage tank (52), a first air pipe connecting the air compressor (51) and the first pressure storage tank (52), a second air pipe connecting the first pressure storage tank (52) and the air collection chamber (39), a one-way valve (53) installed on the first air pipe, and a pressure reducing valve (54) installed on the second air pipe, wherein the second air pipe is a rigid pipe; It also includes a vacuum device, which includes a vacuum pump (61), a second pressure storage tank (62), a third gas pipe connecting the vacuum pump (61) and the second pressure storage tank (62), a vacuum valve (63) installed on the third gas pipe, and a fourth gas pipe connecting the second pressure storage tank (62) and the internal flow channel of the nozzle section (3). It also includes an air tank (7), which is connected to the contraction section (1) through a fifth air pipe, and a one-way ball valve (71) is provided on the fifth air pipe. The pipeline includes a first-stage manifold (391), a second-stage manifold (392), and a third-stage manifold (393) arranged sequentially from top to bottom. The first-stage manifold (391) is connected to the gas collection chamber (39) through a flexible hose. The first-stage manifold (391) and the second-stage manifold (392), as well as the second-stage manifold (392) and the third-stage manifold (393), are all connected by rigid pipes.
2. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 1, characterized in that: The experimental section (4) includes a Pitot tube (41). One end of the Pitot tube (41) with a pressure measuring hole (42) is located in the internal flow channel of the experimental section (4). Pressure sensors (45) are respectively provided on the static pressure tube (43) and the total pressure tube (44) of the Pitot tube (41). The pressure sensors (45) are connected to the feedback control system (46).
3. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 2, characterized in that: The experimental section (4) is square in shape. The upper surface of the experimental section (4) is provided with a groove (47) facing downward. The bottom of the groove (47) is provided with a notch that communicates with the internal flow channel of the experimental section (4). The notch is sealed to the inside and outside of the experimental section (4) by a sealing plate (471) and a sealing ring (472). The Pitot tube (41) is installed through the sealing plate (471). The Pitot tube (41) is sealed to the sealing plate (471) by an O-ring (48). The pressure sensor (45) is connected to the feedback control system (46) by a wire (49).
4. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 1, characterized in that: The upper profile (33) and lower profile (34) each include a first profile (331) corresponding to the nozzle contraction section (35), a second profile (332) corresponding to the throat (36), and a third profile (333) corresponding to the nozzle expansion section (37). The second profile (332) includes a first fixing part (3321) connected to the first profile (331), a second fixing part (3322) connected to the third profile (333), and a third fixing part (3321) connected to the first profile (331). The first fixing part (3321) and the second fixing part (3322) have an arc-shaped plate (3323) at the bottom end, and a cover plate (3324) is connected to the top of the first fixing part (3321) and the second fixing part (3322). The gas collecting chamber (39) is connected to the lower surface of the cover plate (3324) through the first fixing plate (3325) and the second fixing plate (3326), and the cover plate (3324) is provided with an air inlet (3327) that communicates with the inside of the gas collecting chamber (39).
5. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 1, characterized in that: The solenoid valve (38) is a two-position three-way valve. The solenoid valve (38) includes a first through hole (381) and a second through hole (382) at the top, and a third through hole (383), a fourth through hole (384), and a fifth through hole (385) at the bottom. The first through hole (381) is connected to the outlet of the third-stage manifold (393) through a rigid pipe, and the diameter of each through hole on the solenoid valve (38) is larger than the diameter of the circular air hole (3329).
6. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 4, characterized in that: The solenoid valves (38) are arranged in multiple rows. The arc plate (3323) is provided with blind grooves (3328) for installing the solenoid valves (38). Any two rows of solenoid valves are selected to spray and suck at the throat (36). The circular air hole (3329) is opened at the bottom of the blind groove (3328).
7. The variable Mach number wind tunnel experimental device based on jet and suction structure according to claim 1, characterized in that: The internal flow channel of the contraction section (1) is a funnel-shaped flow channel with a large opening and a small outlet. The internal flow channel of the air intake section (2) is a rectangular flow channel. The internal flow channel of the nozzle section (3) is a contraction-expansion type flow channel. The internal flow channel of the experimental section (4) is a rectangular flow channel. The air intake section (2) is connected to the contraction section (1) through the first flange (81). The air intake section (2) is connected to the nozzle section (3) through the second flange (82). The nozzle section (3) is connected to the experimental section (4) through the third flange (83). The wind tunnel is placed on the experimental support platform (84).