A jet device for boundary layer jet control transition test

Abstract

The invention relates to the technical field of wind tunnel jet test, and in particular to an injection device for boundary layer jet control transition test, comprising: a test model installed inside the wind tunnel and an injection system outside the wind tunnel; a stagnation chamber and an absolute pressure sensor are fixed on the test model, and the injection system comprises an air storage tank and an air source, and the air storage tank is connected to the air source through an air source pipe in sequence; the air storage tank is connected to the stagnation chamber through an injection pipe passing through the wind tunnel wall, and the air storage tank is also connected to the wind tunnel flow field inside the wind tunnel through a pressure reducing pipe passing through the wind tunnel wall; the invention utilizes the process of vacuuming before the wind tunnel is operated to discharge the residual gas in the injection system to make it close to a vacuum state, and then injects gas into the air storage tank through a detachable air source, and then deflates and reduces the pressure to the stagnation pressure required for injection, and compared with directly using the existing air supply system of the wind tunnel, an ultra-low pressure air source of 2000Pa close to a vacuum state can be provided, so as to realize precise control of the injection pressure.

Description

Technical Field

[0001] The invention relates to the technical field of wind tunnel jet test, and in particular to a jet device for boundary layer jet control transition test. Background Art

[0002] When air flows over a wall, a region with a large velocity gradient will form near the wall, namely the boundary layer. Boundary layers are divided into laminar boundary layers and turbulent boundary layers according to different flow states. Usually, when air flows over a wall, the boundary layer flow state develops along the wall from the laminar boundary layer region, through the transition region, and finally develops into turbulence. Since different boundary layer flow states have their own characteristics, the wall friction and thermal conductivity of the laminar boundary layer are relatively small, but the ability to resist the adverse pressure gradient is weak, and flow separation is prone to occur; the friction and thermal conductivity of the turbulent boundary layer are relatively large, but the ability to resist the adverse pressure gradient is strong, and flow separation is less likely to occur. Therefore, when designing an aircraft, control is applied to the boundary layer transition according to different working conditions. Delaying / promoting the boundary layer transition can make the aircraft have higher aerodynamic efficiency. At present, the study of boundary layer transition control is one of the hot topics in the field of aerodynamics.

[0003] Boundary layer transition control can be roughly divided into two categories: active jet control transition control and rough element passive transition control. Among them, active jet control transition control has attracted more attention in current research because it can freely control the injection pressure ratio to achieve different control effects. Active jet control transition achieves the effect of controlling transition by arranging nozzle holes on the wall and injecting underexpanded jets into the mainstream.

[0004] In order to develop more efficient active jet control transition control technology, a large number of tests need to be carried out in wind tunnels to study the influence of different jet parameters on the transition control effect. Among them, the injection pressure and the molecular weight of the injected gas are both important injection parameters. The following formula shows the relationship between the static pressure of the incoming flow and the total pressure:

[0005]

[0006] In the formula, P 0 is the total pressure, P is the static pressure, Gamma is the specific heat ratio, Mais the Mach number. According to the above formula, when the total pressure of the wind tunnel is constant, the higher the simulated incoming flow Mach number, the lower the incoming flow static pressure. Under the Mach number simulated by the current wind tunnel test, the incoming flow static pressure can be as low as 200Pa, and the corresponding injection pressure can be as low as 2000Pa, which is close to the vacuum state. At present, the air supply for gas jet tests in wind tunnels usually adopts the method of using a pressure reducing valve to reduce the pressure of the gas source above atmospheric pressure, but this method has the following problems: First, the common pressure reducing valve can only reduce the pressure to near atmospheric pressure at most, so it is difficult to reduce the pressure to a pressure far below atmospheric pressure using the air supply system of the wind tunnel, let alone 2000Pa close to the vacuum state; second, the pressure measured by this method is the pressure at the outlet of the pressure reducing valve, and the pressure loss along the way between the pressure reducing valve and the nozzle is not deducted, so that the actual injection pressure is lower than the pressure at the outlet of the pressure reducing valve; third, the gas source is matched with the wind tunnel air supply system, and the type of injection gas can only be selected from the gas already in the air supply system, which makes it difficult to carry out research on the effect of different injection gases on promoting transition. Therefore, the traditional wind tunnel air supply system cannot achieve the injection pressure required for the jet control transition, and it is difficult to achieve precise control of the pressure, and it is even more impossible to replace the injection gas other than the gas source supporting the air supply system as needed.

[0007] Taking the above into consideration, the present invention proposes an injection device for boundary layer jet control transition test. By reasonably setting the volume of the gas tank, the pipeline diameter, and the position of the pressure sensor, on the one hand, the injection pressure can be reduced to a minimum of 2000Pa, and the pressure can be precisely controlled so that the actual injection pressure is basically consistent with the designed injection pressure. On the other hand, through the detachable gas source, the type of injection gas can be freely replaced, making it possible to study the effects of different injection gases in controlling the transition. Summary of the invention

[0008] The purpose of the present invention is to provide an injection device for a boundary layer jet control transition test, which can achieve ultra-low pressure air supply close to a vacuum state, accurately control the injection pressure, and freely change the type of injection gas, thereby realizing the air supply for the jet control transition test of an air-breathing engine flying at a faster speed, improving the accuracy of the test, and expanding the types of injection gas for experimental research.

[0009] To achieve the above-mentioned object of the invention, the present invention is as follows:

[0010] A jet injection device for boundary layer jet control transition test, comprising: a test model installed inside a wind tunnel and a jet injection system outside the wind tunnel;

[0011] The test model is fixed with a stationary chamber and an absolute pressure sensor, wherein one end of the absolute pressure sensor is directly connected to the stationary chamber, and the other end is connected to the display through a signal line;

[0012] The injection system includes an air tank and an air source, wherein the air tank is connected to the air source through an air source pipe with a first valve and a pressure reducing valve arranged in sequence; the air tank is connected to a stationary chamber through an injection pipe with a second valve passing through the wind tunnel wall, and a spray hole is arranged on the stationary chamber; the air tank is also connected to the wind tunnel flow field inside the wind tunnel through a pressure reducing pipe with a third valve passing through the wind tunnel wall; a vacuum gauge for reading the pressure inside the air tank is installed on the air tank.

[0013] As a preferred method, a. when the wind tunnel is evacuated, the remaining gas in the injection system is discharged into the wind tunnel through the pressure reducing pipe and is evacuated together with the process of evacuating the wind tunnel;

[0014] When the pressure is close to vacuum and it is difficult to continue to drop, let the gas in the gas source be injected into the gas tank. When the pressure in the gas tank is not less than 150% of the stagnation pressure required for the jet control transition test, let the gas in the injection system flow to the vacuum environment in the wind tunnel through the jet pipe and the pressure reducing pipe.

[0015] When the pressure of the gas storage tank drops to 110% of the stagnation pressure required for the jet control transition test, the gas in the injection system is allowed to flow through the stagnation chamber only through the jet pipe, and then discharged into the vacuum environment of the wind tunnel through the nozzle of the stagnation chamber.

[0016] b. When the wind tunnel starts to operate, the injection system supplies gas of the stagnation pressure required for the jet-controlled transition test to the stagnation chamber through the jet pipe;

[0017] As a preferred embodiment, the injection pressure of the injection device is reduced to a minimum of 2000Pa close to a vacuum state.

[0018] As a preferred embodiment, the gas source is detachably connected to the gas source pipe, and the type of injection gas of the gas source is replaceable.

[0019] As a preferred method, the injection pressure is reduced to a minimum of 2000Pa by setting the volume of the gas storage tank, the diameter of the injection pipe, and the position of the absolute pressure sensor, and the injection pressure is controlled so that the actual injection pressure is consistent with the designed injection pressure.

[0020] As a preferred method, the volume of the gas storage tank is > 0.5m 3 The inner diameter cross-sectional area of ​​the jet pipe shall not be less than 3 times the total area of ​​all the nozzle holes in the stationary chamber, the inner diameter of the jet pipe shall be >15mm, and the inner diameter of the pressure reducing pipe shall not be less than 20mm.

[0021] The reason for this setting is that: since the gas pressure in the gas storage tank will gradually decrease as the gas is ejected, in order to stabilize the pressure, the volume of the gas storage tank should not be too small (volume> 0.5m 3 ). Because the nozzle hole uses sonic injection, and the boundary layer thickens along the process, the inner diameter cross-sectional area of ​​the nozzle tube is not less than 3 times the sum of the areas of all nozzle holes, so the inner diameter of the nozzle tube should not be too small (>15mm). The pressure reducing tube needs to be quickly exhausted and decompressed, and the inner diameter should not be less than 20mm.

[0022] As a preferred embodiment, when the wind tunnel is evacuated, the injection device closes the first valve, the pressure reducing valve, and the second valve, and opens the third valve to allow the remaining gas in the injection system to be discharged into the wind tunnel along the pressure reducing pipe and evacuated together with the wind tunnel being evacuated; reads the pressure of the vacuum gauge on the gas storage tank, and when the pressure is close to vacuum and is difficult to continue to drop, closes the third valve, opens the first valve, rotates the pressure reducing valve, allows the gas in the gas source to be injected into the gas storage tank, and reads the pressure on the vacuum gauge, and when the pressure is not less than 150% of the stagnation pressure required for the jet control transition test, closes the first valve in sequence Open the valve, the pressure reducing valve, and then the second valve and the third valve in sequence, so that the gas in the injection system flows to the vacuum environment in the wind tunnel along the injection pipe and the pressure reducing pipe, and read the pressure of the absolute pressure sensor directly connected to the stagnant chamber through the display. When the pressure drops to 110% of the stagnation pressure required for the jet control transition test, close the third valve, so that the gas in the injection system flows through the stagnant chamber only through the injection pipe, and then is discharged to the vacuum environment of the wind tunnel through the nozzle of the stagnant chamber. When the pressure of the absolute pressure sensor is equal to the stagnation pressure required for the jet control transition test, close the second valve;

[0023] When the wind tunnel starts to operate, open the second valve, and the injection system supplies gas with the stagnation pressure required for the jet-controlled transition test to the stagnation chamber through the jet pipe; when it is necessary to study the influence of different injection gases on the transition, just replace the gas source of the required injection gas.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows: the present invention utilizes the process of evacuating the wind tunnel before operation to discharge the residual gas in the injection system to make it close to a vacuum state, and then injects the gas into the gas storage tank through a detachable gas source, and then deflates the gas and reduces the pressure to the stagnation pressure required for injection. Compared with directly using the existing gas supply system of the wind tunnel, it has the following advantages: First, combined with the process of evacuating the wind tunnel, an ultra-low pressure gas source of 2000Pa close to a vacuum state can be provided; second, the debugging pressure reference is the absolute pressure sensor directly connected to the resident chamber, compared with the pressure of the reference gas supply system outlet pressure reducing valve, the error of pressure loss along the process is reduced, and precise control of the injection pressure is achieved; third, a detachable gas source is used, and a gas source containing corresponding gas can be purchased according to the test needs, thereby expanding the types of injection gases for experimental research. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] FIG1 is a schematic diagram of an injection device for an air-breathing engine jet control transition test;

[0026] 1-gas source, 2-first valve, 3-pressure reducing valve, 4-gas source pipe, 5-gas storage tank, 6-vacuum gauge, 7-second valve, 8-third valve, 9-injection pipe, 10-pressure reducing pipe, 11-display, 12-signal line, 13-wind tunnel wall, 14-test model, 15-absolute pressure sensor, 16-station chamber. DETAILED DESCRIPTION

[0027] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0028] like Picture 1 As shown, an injection device for boundary layer jet control transition test includes: a test model 14 installed inside a wind tunnel and an injection system outside the wind tunnel;

[0029] The test model 14 is fixed with a stationary chamber 16 and an absolute pressure sensor 15, wherein one end of the absolute pressure sensor 15 is directly connected to the stationary chamber 16, and the other end is connected to the display 11 through a signal line 12;

[0030] The injection system includes an air tank 5 and an air source 1, wherein the air tank 5 is connected to the air source 1 through an air source pipe 4 which is sequentially provided with a first valve 2 and a pressure reducing valve 3; the air tank 5 is connected to a stationary chamber 16 through an injection pipe 9 with a second valve 7 passing through a wind tunnel wall 13, and a spray hole is provided on the stationary chamber 16; the air tank 5 is also connected to the wind tunnel flow field inside the wind tunnel through a pressure reducing pipe 10 with a third valve 8 passing through the wind tunnel wall 13; a vacuum gauge 6 for reading the pressure inside the air tank is installed on the air tank 5.

[0031] a. When the wind tunnel is evacuated, the remaining gas in the injection system is discharged into the wind tunnel through the pressure reducing pipe 10 and is evacuated along with the process of evacuating the wind tunnel;

[0032] When the pressure is close to vacuum and difficult to drop further, the gas in the gas source 1 is injected into the gas storage tank 5. When the pressure of the gas storage tank 5 is not lower than 150% of the stagnation pressure required for the jet control transition test, the gas in the injection system is allowed to flow to the vacuum environment in the wind tunnel along the jet pipe 9 and the pressure reducing pipe 10.

[0033] When the pressure of the gas storage tank 5 drops to 110% of the stagnation pressure required for the jet control transition test, the gas in the injection system is allowed to flow through the stationary chamber 16 only through the jet pipe 9, and then discharged to the vacuum environment of the wind tunnel through the jet hole of the stationary chamber 16;

[0034] b. When the wind tunnel starts to operate, the injection system supplies gas of the stagnation pressure required for the jet-controlled transition test to the stationary chamber 16 through the jet pipe 9; preferably, the injection pressure of the injection device is reduced to a minimum of 2000Pa, which is close to the vacuum state.

[0035] Preferably, the gas source 1 is detachably connected to the gas source pipe 4, and the type of injection gas of the gas source 1 is replaceable.

[0036] Preferably, the injection pressure is reduced to a minimum of 2000Pa by setting the volume of the gas storage tank 5, the diameter of the injection pipe 9, and the position of the absolute pressure sensor 15, and the injection pressure is controlled so that the actual injection pressure is consistent with the designed injection pressure.

[0037] Preferably, the volume of the gas storage tank 5 is >0.5m 3 The inner diameter cross-sectional area of ​​the jet pipe 9 is not less than 3 times the total area of ​​all the jet holes in the stationary chamber 16, the inner diameter of the jet pipe 9 is greater than 15 mm, and the inner diameter of the pressure reducing pipe 10 is not less than 20 mm.

[0038] The working method of the present invention is as follows:

[0039] When the wind tunnel is evacuated, close the first valve 2, the pressure reducing valve 3, and the second valve 7, and open the third valve 8 to allow the remaining gas in the injection system to be discharged into the wind tunnel along the pressure reducing pipe 10 and evacuated together with the wind tunnel being evacuated; read the pressure of the vacuum gauge 6 on the gas storage tank 5. When the pressure is close to vacuum and it is difficult to continue to drop, close the third valve 8, open the first valve 2, turn the pressure reducing valve 3, allow the gas in the gas source 1 to be injected into the gas storage tank 5, and read the pressure on the vacuum gauge 6. When the pressure is not less than 150% of the stagnation pressure required for the jet control transition test, close the first valve 2 and the pressure reducing valve 3 in turn, and then follow the steps below to complete the test. The second valve 7 is opened again, and the third valve 8 is opened to allow the gas in the injection system to flow to the vacuum environment in the wind tunnel along the injection pipe 9 and the pressure reducing pipe 10, and the pressure of the absolute pressure sensor 15 directly connected to the stationary chamber 16 is read through the display 11. When the pressure drops to 110% of the stagnation pressure required for the injection control transition test, the third valve 8 is closed to allow the gas in the injection system to flow through the stationary chamber 16 only through the injection pipe 9, and then discharged to the vacuum environment of the wind tunnel through the nozzle of the stationary chamber 16. When the pressure of the absolute pressure sensor 15 is equal to the stagnation pressure required for the injection control transition test, the second valve 7 is closed;

[0040] When the wind tunnel starts to operate, the second valve 7 is opened, and the injection system supplies gas with the stagnation pressure required for the jet-controlled transition test to the resident chamber 16 through the jet pipe 9; when it is necessary to study the influence of different injection gases on the transition, the gas source 1 of the required injection gas can be replaced.

[0041] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical ideas disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A jetting device for boundary layer jet control transition test, characterized in that: include: A test model (14) installed inside the wind tunnel and an injection system outside the wind tunnel; A stationary chamber (16) and an absolute pressure sensor (15) are fixed on the test model (14), wherein one end of the absolute pressure sensor (15) is directly connected to the stationary chamber (16), and the other end is connected to the display (11) via a signal line (12); The injection system comprises an air storage tank (5) and an air source (1), wherein the air storage tank (5) is connected to the air source (1) via an air source pipe (4) provided with a first valve (2) and a pressure reducing valve (3) in sequence; the air storage tank (5) is connected to a stationary chamber (16) via an air injection pipe (9) provided with a second valve (7) and passing through a wind tunnel wall (13); the stationary chamber (16) is provided with an injection hole; the air storage tank (5) is also connected to a wind tunnel flow field inside the wind tunnel via a pressure reducing pipe (10) provided with a third valve (8) and passing through the wind tunnel wall (13); a vacuum gauge (6) for reading the pressure inside the air storage tank is installed on the air storage tank (5); a. When the wind tunnel is evacuated, the remaining gas in the injection system is discharged into the wind tunnel through the pressure reducing pipe (10) and is evacuated along with the evacuation process of the wind tunnel; When the pressure approaches vacuum and is difficult to drop further, the gas in the gas source (1) is injected into the gas storage tank (5); when the pressure in the gas storage tank (5) is not less than 150% of the stagnation pressure required for the jet control transition test, the gas in the injection system is allowed to flow to the vacuum environment in the wind tunnel through the jet pipe (9) and the pressure reducing pipe (10); When the pressure of the gas storage tank (5) drops to 110% of the stagnation pressure required for the jet control transition test, the gas in the injection system is allowed to flow through the resident chamber (16) only through the jet pipe (9), and then discharged into the vacuum environment of the wind tunnel through the jet hole of the resident chamber (16); b. When the wind tunnel starts to operate, the injection system supplies gas with the stagnation pressure required for the jet-controlled transition test to the stagnant chamber (16) through the jet pipe (9).

2. The injection device for boundary layer jet control transition test according to claim 1, characterized in that: The injection pressure of the injection device is reduced to 2000Pa, which is close to the vacuum state.

3. The injection device for boundary layer jet control transition test according to claim 1, characterized in that: The gas source (1) is detachably connected to the gas source pipe (4), and the type of gas injected by the gas source (1) is replaceable.

4. The injection device for boundary layer jet control transition test according to claim 1, characterized in that: By setting the volume of the gas storage tank (5), the diameter of the injection pipe (9), and the position of the absolute pressure sensor (15), the injection pressure is reduced to a minimum of 2000 Pa, and the injection pressure is controlled so that the actual injection pressure is consistent with the designed injection pressure; The volume of the gas storage tank (5) is > 0.5m 3 The inner diameter cross-sectional area of ​​the jet pipe (9) is not less than 3 times the total area of ​​all the jet holes in the stationary chamber (16), the inner diameter of the jet pipe (9) is greater than 15 mm, and the inner diameter of the pressure reducing pipe (10) is not less than 20 mm.

Images