A MEMS-driven suction plate for suppressing curved surface shock waves and boundary layer interference

Abstract

This invention discloses a MEMS-driven suction orifice plate for suppressing interference from curved shock waves and boundary layers, belonging to the field of aerodynamics. It includes a suction orifice plate with an array of suction orifices; an array of wall static pressure measuring points on the suction orifice plate, each measuring point equipped with a steady-state pressure sensor, the static pressure signal of each measuring point being measured by the steady-state pressure sensor; an elastic foil covering the orifice opening within each suction orifice; and a foil driving device below each elastic foil for driving the elastic foil to close and open the suction orifice; the steady-state pressure sensor and the foil driving device are connected to a control computer. This invention effectively suppresses airflow separation caused by shock wave and boundary layer interference. When suppression is not required, the elastic foil closes the suction orifice, maintaining a complete solid wall shape, reducing outflow and flow loss, and can adapt to complex situations where curved shock waves are incident on the wall surface.

Description

Technical Field

[0001] This invention relates to the field of aerodynamics, specifically to a MEMS-driven suction plate for suppressing surface shock waves and boundary layer interference. Background Technology

[0002] In the air intakes of supersonic and hypersonic air-breathing aircraft, severe shock wave and boundary layer interference often occurs in the compressed airflow. To improve the compression efficiency of the air intake, some form of flow field control is needed to weaken and eliminate unfavorable flow field structures such as separation caused by shock wave and boundary layer interference. Boundary layer extraction is a commonly used method with good flow field control effect and relatively simple structure. A common boundary layer extraction method is to set extraction grooves or extraction orifice plates at the location of shock wave and boundary layer interference.

[0003] However, traditional boundary layer suction channels and similar devices can only be used when the positions of shock wave and boundary layer interference are fixed. Boundary layer suction orifice plates are suitable for situations where the positions of shock wave and boundary layer interference vary within a certain range, and therefore have more engineering applications. The most advanced boundary layer suction orifice plates currently available employ an adaptive design with the orifice tilted forward. In ultrasonic flow conditions, suction can be limited by the Prandtl-Mayer expansion wave structure, and in subsonic flow conditions, especially in the separation state caused by shock wave and boundary layer interference, this structure can achieve a significant suction effect.

[0004] Even with the current advanced suction technology, orifice plates still face several challenges: 1. To cope with variations in shock wave incident positions under different operating conditions, a relatively wide (and large-area) suction zone opening is required. In areas where suction is not needed, the opening affects the smoothness of the wall surface, increasing flow losses to some extent. 2. To control flow losses caused by the opening, the orifice plate's opening ratio (the ratio of the opening area to the total area of ​​the orifice plate, often set at 20%–30% or less) is generally required. However, a low opening ratio severely impacts the boundary layer suction effect. 3. When curved shock waves are incident on the wall surface (the most advanced three-dimensional internal rotation inlet, or three-dimensional internal contraction inlet, uses curved shock wave compression airflow), the intersection of the shock wave surface and the wall surface is curved, and this curve changes with operating conditions. This complexity makes it even more difficult to reconcile the contradictions mentioned above. Summary of the Invention

[0005] Purpose of the invention: To solve the above problems, the present invention provides a MEMS driven suction orifice plate that suppresses interference from curved surface shock waves and boundary layers. The present invention can overcome the shortcomings of traditional suction grooves and existing suction orifice plates, effectively suppress and weaken the effects of separation flow caused by shock wave boundary layer interference, and reduce local flow losses to a certain extent, thus ensuring the quality of internal flow.

[0006] Technical solution: A MEMS-driven suction orifice plate for suppressing curved surface shock waves and boundary layer interference, comprising a suction orifice plate with an array of suction orifices; an array of wall static pressure measuring points on the suction orifice plate, each measuring point being equipped with a steady-state pressure sensor, the static pressure signal of each measuring point being measured by the steady-state pressure sensor; an elastic foil covering the orifice opening being provided in each suction orifice; and a foil driving device below each elastic foil for driving the elastic foil to close and open the suction orifice.

[0007] The steady-state pressure sensor and foil driving device are connected to the control computer. The control computer calculates the shock wave boundary layer interference zone on the suction orifice plate based on the received static pressure signal, and then controls the elastic foil in the shock wave boundary layer interference zone to open the suction orifice through the foil driving device, and controls the elastic foil outside the shock wave boundary layer interference zone to close the suction orifice.

[0008] Furthermore, the opening ratio of the suction plate is 40% to 60%, the suction hole is a rectangular hole, and the two included angles of the rectangular hole are rounded and located on the same side of the rectangular hole.

[0009] Furthermore, the wall static pressure measuring point array has measuring points arranged according to the shape of the suction hole plate and evenly distributed within the suction hole array area.

[0010] Furthermore, the foil driving device includes a micro-airbag and a MEMS on / off valve. The micro-airbag is connected to the high-pressure air path and the suction chamber. The MEMS on / off valve connects the high-pressure air path and the suction chamber and is used to control the closing and opening of the high-pressure air path and the suction chamber. One end of the elastic foil is fixed to the inner wall of the suction hole. The upper side of the micro-airbag is fixedly connected to the lower side of the elastic foil, and the position of the lower side of the micro-airbag is fixed.

[0011] Furthermore, the control computer is an embedded microcontroller.

[0012] Furthermore, the calculation method for the shock wave boundary layer interference zone on the suction orifice plate is as follows:

[0013] 1) First, the control computer uses the cubic spline interpolation method to process the pressure data obtained from the static pressure measuring point array on the wall and sort out the pressure distribution on the wall.

[0014] 2) Secondly, using the theoretical maximum pressure increment ΔP of the incident shock wave to this wall as a reference value, draw isobars according to the pressure interval of ΔP / 10.

[0015] The formula for calculating the theoretical maximum pressure increment range ΔP is as follows:

[0016] ΔP=3P wave ~8P wave

[0017] Among them, P wave Let ΔP be the wavefront pressure, and ΔP be the theoretical maximum pressure increment of the incident shock wave at this wall.

[0018] 3) Finally, if the distance between an isobar and an adjacent isobar is less than twice the local boundary layer momentum loss thickness θ in front of the shock wave, then the isobar is determined to belong to the shock wave boundary layer interference zone. Any two isobars that belong to the shock wave boundary layer interference zone are also determined to be within the shock wave boundary layer interference zone.

[0019] The formula for the boundary layer momentum loss thickness θ is as follows:

[0020]

[0021] Where θ is the boundary layer momentum loss thickness, U e Let ρ be the free flow velocity. e Let ρ be the free flow density, h be the distance, ρ be the density at a point within the boundary layer, and U be the velocity at a point within the boundary layer.

[0022] Furthermore, after calculating the shock wave boundary layer interference region on the suction orifice plate, the control computer sends an opening signal to the MEMS on / off valve located in the shock wave boundary layer interference region and a closing signal to the MEMS on / off valve not located in the shock wave boundary layer interference region.

[0023] After receiving the start signal from the control key computer, the MEMS start-stop valve located in the shock wave boundary layer interference region connects the suction chamber, the gas in the micro-bag is extracted, and the elastic foil deflects downward under the action of low back pressure in the suction chamber to open the suction hole.

[0024] When the MEMS valve, which is not in the shock wave boundary layer interference zone, receives the closing signal output by the control key computer, the MEMS valve connects to the high-pressure gas path, and the micro-airbag expands upward to push against the elastic foil, thus closing the suction hole.

[0025] Beneficial effects:

[0026] This invention, based on the flow field structure of shock-induced boundary layer separation verified by current scientific research, utilizes data obtained from a wall hydrostatic measuring point array. A specific algorithm in the control computer is then used to determine the shock-induced boundary layer interference zone. The computer then controls a MEMS on / off valve below the suction orifice within the interference zone, controlling the exhaust of micro-gasbags to drive an elastic foil to open the suction orifice. This keeps other suction orifices outside the interference zone closed and maintains a relatively intact solid wall structure. Thus, the MEMS-driven suction orifice plate of this invention can suppress the adverse effects of shock / boundary layer interference while minimizing airflow energy loss due to excessive air release and large-area openings in the suction orifice plate. This effectively suppresses and weakens the effects of separation flow caused by shock / boundary layer interference, and to a certain extent reduces local flow losses, ensuring internal flow quality. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the shock wave boundary layer interference and suction orifice plate of the present invention;

[0028] Figure 2 This is a schematic diagram of the MEMS-driven suction plate of the present invention;

[0029] Figure 3 This is a schematic diagram of the micro-airbag and MEMS valve driving the opening and closing of the suction port in this invention.

[0030] Figure 4 This diagram illustrates the process of using spline interpolation to obtain isobars based on static pressure measurement data to determine the shock wave / boundary layer interference zone. Detailed Implementation

[0031] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the embodiments.

[0032] like Figure 2 As shown, this invention provides a MEMS-driven suction port plate for suppressing shock wave and boundary layer interference on curved surfaces. The plate includes a suction port plate with an array of suction ports. The suction port plate also has an array of wall static pressure measurement points, each with a steady-state pressure sensor. The static pressure signal at each point is measured by the steady-state pressure sensor. Each suction port contains an elastic foil covering its opening. Below each elastic foil is a foil driving device for opening and closing the suction port. The steady-state pressure sensor and the foil driving device are connected to a control computer. The control computer calculates the shock wave boundary layer interference zone on the suction port plate based on the received static pressure signal, and then controls the elastic foil within the shock wave boundary layer interference zone to open the suction port, and controls the elastic foil outside the shock wave boundary layer interference zone to close the suction port. After the suction port is closed, the upper surface of the elastic foil remains in a plane or curved surface with the wall of the suction port plate.

[0033] The foil driving device includes a micro-airbag and a MEMS on / off valve. The micro-airbag is connected to the high-pressure gas path and the suction chamber. The MEMS on / off valve connects the high-pressure gas path and the suction chamber and is used to control the closing and opening of the high-pressure gas path and the suction chamber. One end of the elastic foil is fixed to the inner wall of the suction hole. The upper side of the micro-airbag is fixedly connected to the lower side of the elastic foil. The lower side of the micro-airbag is fixed in position and can be fixed at a certain position below the suction hole plate surface to ensure that the elastic foil can deflect downward to open the suction hole when the gas in the micro-airbag is extracted, and to deflect upward to close the suction hole when the micro-airbag is inflated.

[0034] The perforation rate of the suction plate is 40% to 60%; the suction holes are rectangular holes, and the two included corners of the rectangular holes are rounded and located on the same side of the rectangular holes. The suction holes with rounded corners are beneficial to boundary layer displacement and can reduce the expansion effect in the corner region to a certain extent.

[0035] When the shock wave violently interferes with the boundary layer, causing flow separation, the effect is as follows: Figure 1 As shown; the wall static pressure measuring point array distributed on the suction orifice plate, the layout of which can be arranged according to the shape of the suction orifice plate, can generally be set to 4 horizontally × 5 in the flow direction, evenly distributed within the suction orifice array area, such as... Figure 2 As shown in the figure, the dots represent side points. If the shock boundary layer interference zone at this wall location is expected to have a complex shape, more measuring points can be set in the transverse and flow directions.

[0036] In this invention, the control computer has low requirements for input and output control and requires minimal computation; a common embedded microcontroller can suffice. The calculation method for the shock wave boundary layer interference region on the suction port plate is as follows:

[0037] 1) First, the control computer uses the cubic spline interpolation method to process the pressure data obtained from the static pressure measuring point array on the wall and sort out the pressure distribution on the wall.

[0038] 2) Secondly, using the theoretical maximum pressure increment ΔP of the incident shock wave to this wall as a reference value, draw isobars according to the pressure interval of ΔP / 10.

[0039] ΔP=3P wave ~8P wave

[0040] Among them, P wave Let ΔP be the wavefront pressure, and ΔP be the theoretical maximum pressure increment of the incident shock wave at this wall.

[0041] 3) Finally, if the distance between an isobar and an adjacent isobar is less than twice the local boundary layer momentum loss thickness θ in front of the shock wave, then the isobar is determined to belong to the shock wave boundary layer interference zone. Any two isobars that belong to the shock wave boundary layer interference zone are also determined to be within the shock wave boundary layer interference zone.

[0042] The formula for the boundary layer momentum loss thickness θ is as follows:

[0043]

[0044] Where θ is the boundary layer momentum loss thickness, Ue is the free flow velocity, and ρ e Let ρ be the free flow density, h be the distance, ρ be the density at a point within the boundary layer, and U be the velocity at a point within the boundary layer.

[0045] Using the above calculation method, we can obtain strip regions of arbitrary curved surface shape covered by shock wave boundary layer interference, i.e., shock wave boundary layer interference regions, such as... Figure 4 As shown;

[0046] After the control computer calculates the shock wave boundary layer interference region on the suction orifice plate, it sends an opening signal to the MEMS on / off valve located in the shock wave boundary layer interference region and a closing signal to the MEMS on / off valve not located in the shock wave boundary layer interference region; for example Figure 2 As shown:

[0047] After receiving the activation signal from the control computer, the MEMS on / off valve located in the shock wave boundary layer interference region connects the suction chamber (simultaneously closing the high-pressure gas path), and the gas inside the micro-bag is extracted, such as... Figure 3 As shown in (a), the elastic foil deflects downward under the action of low back pressure in the suction chamber to open the suction port, thereby displacing the boundary layer (displacing the low energy flow from the suction port under the action of pressure gradient).

[0048] The MEMS on / off valve, located outside the shock wave boundary layer interference region, receives a shutdown signal from the control computer. The MEMS on / off valve then connects to the high-pressure gas path (simultaneously closing the suction chamber). Figure 3 As shown in (b), the micro-gas bladder expands upwards and presses against the elastic foil to close the suction orifice. Closing the suction orifice ensures that the wall surface of the suction orifice, which is not in the shock wave boundary layer interference zone, presents a smooth solid wall shape, which can reduce the amount of gas release and flow loss, and can adapt to the complex situation of curved shock waves incident on the wall surface.

[0049] This invention is used in the air intakes of supersonic and hypersonic air-breathing aircraft. Based on the shock-induced boundary layer separation flow field structure verified by current scientific research, this invention utilizes data obtained from an array of wall static pressure measuring points and employs a specific algorithm in a control computer to determine the shock-induced boundary layer interference zone. Figure 2 (As shown in the shaded area); then, the computer controls the MEMS on / off valve below the suction port in the interference area, controls the micro-gasbag to release gas, and drives the elastic foil to open the suction port, keeping other suction ports outside the interference area closed and maintaining a relatively intact solid wall shape. In this way, the MEMS-driven suction port plate can suppress the adverse effects of shock wave / boundary layer interference, and minimize the airflow energy loss caused by excessive gas release and large-area openings in the suction port plate.

[0050] This invention effectively suppresses and weakens the effects of shock wave boundary layer interference on separated flow, and reduces local flow loss to a certain extent, ensuring internal flow quality. It can also adapt to complex situations where curved shock waves are incident on the wall surface (the intersection of the shock wave surface and the wall surface is curved, and this curve changes with the operating conditions).

[0051] As described above, although the invention has been shown and described with reference to specific preferred embodiments, it should not be construed as limiting the invention itself. Various changes in form and detail may be made without departing from the spirit and scope of the invention as defined in the appended claims.

Claims

1. A MEMS-driven suction plate for suppressing interference from curved surface shock waves and boundary layer, characterized in that, The device includes a suction orifice plate with an array of suction orifices; an array of wall static pressure measuring points on the suction orifice plate, with a steady-state pressure sensor at each measuring point, and the static pressure signal at each measuring point is measured by the steady-state pressure sensor; an elastic foil covering the orifice is provided inside each suction orifice; and a foil driving device is provided below each elastic foil to drive the elastic foil to close and open the suction orifice. The steady-state pressure sensor and foil driving device are connected to the control computer. The control computer calculates the shock wave boundary layer interference zone on the suction orifice plate based on the received static pressure signal, and then controls the elastic foil in the shock wave boundary layer interference zone to open the suction orifice through the foil driving device, and controls the elastic foil outside the shock wave boundary layer interference zone to close the suction orifice.

2. The MEMS driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 1, characterized in that, The perforation rate of the suction plate is 40% to 60%, and the suction hole is a rectangular hole with two rounded corners located on the same side of the rectangular hole.

3. The MEMS driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 1, characterized in that, The wall static pressure measuring point array has its measuring points arranged according to the shape of the suction orifice plate and evenly distributed within the suction orifice array area.

4. The MEMS driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 1, characterized in that, The foil driving device includes a micro-airbag and a MEMS on / off valve. The micro-airbag is connected to the high-pressure air circuit and the suction chamber. The MEMS on / off valve is connected to the high-pressure air circuit and the suction chamber and is used to control the closing and opening of the high-pressure air circuit and the suction chamber. One end of the elastic foil is fixed to the inner wall of the suction hole, the upper side of the micro airbag is fixedly connected to the lower side of the elastic foil, and the position of the lower side of the micro airbag is fixed.

5. The MEMS driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 1, characterized in that, The control computer is an embedded microcontroller.

6. The MEMS driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 4, characterized in that, The calculation method for the shock wave boundary layer interference zone on the suction orifice plate is as follows: 1) First, the control computer uses the cubic spline interpolation method to process the pressure data obtained from the static pressure measuring point array on the wall and sort out the pressure distribution on the wall. 2) Secondly, using the theoretical maximum pressure increment ΔP of the incident shock wave to this wall as a reference value, draw isobars according to the pressure interval of ΔP / 10. The formula for calculating the theoretical maximum pressure increment range ΔP is as follows: ΔP=3P wave ~8P wave Among them, P wave Let ΔP be the wavefront pressure, and ΔP be the theoretical maximum pressure increment of the incident shock wave at this wall. 3) Finally, if the distance between an isobar and an adjacent isobar is less than twice the local boundary layer momentum loss thickness θ in front of the shock wave, then the isobar is determined to belong to the shock wave boundary layer interference zone. Any two isobars that belong to the shock wave boundary layer interference zone are also determined to be within the shock wave boundary layer interference zone. The formula for the boundary layer momentum loss thickness θ is as follows: Where θ is the boundary layer momentum loss thickness, U e Let ρ be the free flow velocity. e Let ρ be the free flow density, h be the distance, ρ be the density at a point within the boundary layer, and U be the velocity at a point within the boundary layer.

7. A MEMS-driven suction plate for suppressing curved surface shock waves and boundary layer interference according to claim 6, characterized in that, After calculating the shock wave boundary layer interference region on the suction orifice plate, the control computer sends an opening signal to the MEMS on / off valve located in the shock wave boundary layer interference region and a closing signal to the MEMS on / off valve not located in the shock wave boundary layer interference region. After receiving the start signal from the control key computer, the MEMS start-stop valve located in the shock wave boundary layer interference region connects the suction chamber, the gas in the micro-bag is extracted, and the elastic foil deflects downward under the action of low back pressure in the suction chamber to open the suction hole. When the MEMS valve, which is not in the shock wave boundary layer interference zone, receives the closing signal output by the control key computer, the MEMS valve connects to the high-pressure gas path, and the micro-airbag expands upward to push against the elastic foil, thus closing the suction hole.

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