A self-excited jet device with adaptive switching of jet modes and its design method

Abstract

This invention discloses a self-excited jet device with adaptive switching of jet modes and its design method. The device includes: an air inlet, a mixing chamber, and a jet inlet located sequentially along the central axis of the device, forming the main flow path; static pressure chambers and feedback loops surrounding the static pressure chambers are respectively provided on both sides of the mixing chamber. The static pressure chamber is a hollow structure formed by the surrounding static pressure chamber wall, and a certain number of static pressure holes are opened on the static pressure chamber wall. A flexible membrane is installed on the side of the static pressure chamber wall closest to the central axis. When different air inlet pressures are applied to the air inlet of the device, the flexible membrane exhibits different modes of being close to or far from the static pressure chamber wall, thereby generating a swept jet or a steady jet at the jet inlet for fluid flow control. This invention can be used to suppress flow separation and improve flow efficiency in fluid machinery, air intake and exhaust systems, and other devices.

Description

Technical Field

[0001] This invention relates to a self-excited jet device with adaptive switching of jet modes and its design method, belonging to the field of flow control technology. Background Technology

[0002] Current fluid machinery development is trending towards higher aerodynamic loads. However, when these loads significantly exceed current aerodynamic design levels, flow separation often occurs due to high adverse pressure gradients or shock-boundary layer interference, leading to a sharp decline in fluid machinery efficiency and even instability. Therefore, researchers both domestically and internationally have been focusing on flow control technologies and corresponding devices that can suppress or even eliminate flow separation. Unsteady flow control technology is an advanced flow control technique. The unsteady excitation it generates can utilize flow instability to coherently interact with the pseudo-ordered structures in the separated flow. Related research shows that to achieve the same flow control effect, unsteady flow control technology can save 1 to 2 orders of magnitude of energy compared to corresponding steady flow control technology, achieving a "leveraging effect with minimal effort."

[0003] A self-excited jet oscillator can be used as an unsteady flow control device. If the inlet and outlet of the self-excited jet oscillator are connected to high-pressure and low-pressure gas sources respectively, the oscillator can generate an unsteady jet at the outlet by relying on flow instability, which can be used as the unsteady excitation required for unsteady flow control. Because the self-excited jet oscillator has a simple structure and no moving parts, it has good application prospects.

[0004] However, current self-excited jet oscillators, as passive unsteady flow control devices, suffer from adaptability issues under varying operating conditions. During operation, the self-excited jet oscillator experiences high internal flow losses due to the periodic oscillation of the fluid within it. Taking the application of self-excited jet oscillators to compressors as an example, under off-design conditions, especially near-stall conditions, compressor blades experience significant flow losses due to blade back separation. In such cases, using a self-excited jet oscillator for unsteady flow control can potentially yield good control results. Although the internal flow losses of the self-excited jet oscillator are high, these losses are often much smaller than the benefits of suppressing flow separation. However, under compressor design conditions, where blades often operate at high efficiency points with little or no flow separation and low blade flow losses, flow control is often unnecessary. However, unless the self-excited jet oscillator is actively shut down, its continued operation will result in high internal flow losses, thereby reducing the overall performance of the compressor. Therefore, conventional self-excited jet oscillators, when used as a passive flow control method, lack applicability to changes in the operating conditions of the passive object, thus affecting their engineering practicality. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a self-excited jet device and its design method with adaptive switching of jet modes, which can be used to suppress flow separation and improve flow efficiency in devices such as fluid machinery and air intake / exhaust systems.

[0006] To achieve the above objectives, the present invention is implemented using the following technical solution:

[0007] In a first aspect, the present invention provides a self-excited jet device with adaptive switching of jet modes, comprising: an air intake, a mixing chamber, and a jet outlet located sequentially along the central axis of the device, forming a main flow path; a static pressure chamber and a feedback loop arranged around the static pressure chamber are respectively provided on both sides of the mixing chamber; the static pressure chamber is a hollow structure formed by a static pressure chamber wall, the static pressure chamber wall has a certain number of static pressure holes, and a flexible membrane is installed on the side of the static pressure chamber wall closest to the central axis, wherein:

[0008] When different air inlet pressures are applied to the device's air inlet, the flexible membrane exhibits different modes of adhering closely to or moving away from the static pressure chamber wall, thereby generating swept jets or steady jets at the jet inlet for fluid flow control.

[0009] Furthermore, the static pressure chamber is filled with a fluid having a static pressure P0, which is a fixed value or a pressure value associated with the external flow field controlled by the self-excited jet device.

[0010] Furthermore, the static pressure on the side of the flexible membrane away from the central axis is equal to the static pressure P0 in the static pressure chamber.

[0011] Furthermore, let P1 be the average static pressure near the central axis of the flexible membrane. When the pressure at the air inlet is high, such that P1 ≥ P u At this time, the flexible membrane is in close contact with the static pressure chamber wall, and the jet outlet generates a sweeping jet with a certain frequency. When the pressure at the air intake is low, such that P1 ≤ P s At this time, the flexible membrane is far from the wall of the hydrostatic chamber, and a steady jet is generated at the jet outlet, where: P u When the jet injector is in the minimum flow state of swept jet mode, the average static pressure P near the central axis of the flexible membrane is... u ;P s The average static pressure on the near-central axis side of the flexible membrane when the jet injector just enters the steady jet mode.

[0012] Furthermore, when the jet injector is in the minimum flow state of the swept jet mode, the average static pressure P near the central axis of the flexible membrane 8 is... u The calculation formula is as follows:

[0013] P u ≈P0+F0 / R0

[0014] Where F0 is the tension of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber, and R0 is the average radius of curvature of the wall of the pressure chamber near the central axis.

[0015] Furthermore, the formula for calculating the average static pressure on the flexible membrane near the central axis when the jet injector just enters the steady jet mode is as follows:

[0016] P s =P0-F c / R c

[0017] Among them, R c When the throat width of the flexible membrane is equal to h, the radius of curvature of the flexible membrane is F. c The tension of the flexible membrane is given when the throat width of the flexible membrane is equal to h, where h is the throat width of the flexible membrane corresponding to the jet ejector entering the steady jet mode.

[0018] In a second aspect, the present invention provides a design method for a self-excited jet device with adaptive switching of jet modes according to any one of the foregoing claims, comprising:

[0019] Calculate the average static pressure P near the central axis of the flexible membrane when the flexible membrane is in close contact with the hydrostatic chamber wall and the ejector is in sweeping jet mode at minimum flow. u ;

[0020] Through P u Calculate the tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber;

[0021] Calculate the average static pressure P near the central axis of the flexible membrane when the flexible membrane is far from the hydrostatic chamber wall and the jet injector has just entered the steady jet mode. s ;

[0022] Through P s Calculate the tension F of the flexible membrane when it is far from the wall of the hydrostatic chamber. c ;

[0023] By designing the tensions F0 and F of a given flexible membrane under two critical states... c A self-excited jet device with adaptive switching of jet modes was obtained, which can adaptively switch between steady jet mode and unsteady jet mode.

[0024] Furthermore, the method for calculating the tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber includes:

[0025] The average radius of curvature R0 of the hydrostatic chamber wall near the central axis is calculated based on the jet geometry.

[0026] Given the static pressure at the jet outlet and the static pressure P0 inside the static pressure chamber;

[0027] Numerical simulation was used to calculate the average static pressure P near the central axis of the flexible membrane when it was in close contact with the hydrostatic chamber wall and the jet was in sweeping jet mode at minimum flow. u ;

[0028] The tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber is calculated using the following formula:

[0029] F0≈(P u -P0)×R0.

[0030] Furthermore, the calculated tension F of the flexible membrane when it is far from the hydrostatic cavity wall is... c The methods include:

[0031] Given the static pressure at the jet outlet and the static pressure inside the static pressure chamber as P0;

[0032] The width h of the flexible membrane throat corresponding to the jet ejector entering the steady jet mode was determined by numerical simulation.

[0033] Calculate the radius of curvature R of the flexible membrane when the throat width is equal to h. c ;

[0034] The average static pressure P on the near-central side of the flexible membrane was calculated using numerical simulation when the flexible membrane was far from the wall of the hydrostatic chamber and the throat width was equal to h. s ;

[0035] Calculate the tension F of the flexible membrane when it is far from the wall of the hydrostatic chamber and the width of the larynx is equal to h. c The formula is as follows:

[0036] F c =(P0-P s )×R c .

[0037] Furthermore, the design method also includes:

[0038] The total inlet pressure P is obtained when the ejector just enters steady jet mode and the width of the flexible membrane throat is equal to h. is *And the total inlet pressure P corresponding to the ejector being in sweeping jet mode at minimum flow rate. iu *;

[0039] When the total pressure P at the ejector inlet i * Satisfies P i * <P is *At this time, the ejector enters steady jet mode;

[0040] When the total pressure P at the ejector inlet i * Satisfies P iu * <P i*At this time, the jet injector enters the unsteady swept jet mode.

[0041] Compared with the prior art, the beneficial effects achieved by the present invention are as follows:

[0042] This invention provides a self-excited jet device and its design method with adaptive switching of jet modes. It can adaptively adjust the jet mode according to different air inlet pressures, thereby solving the problem of low or even negative returns of existing self-excited jet devices for separation flow control under varying operating conditions, and has stronger engineering practicality. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of a self-excited jet device with adaptive jet mode switching provided in an embodiment of the present invention;

[0044] Figure 2 This is a schematic diagram of the device provided in the embodiment of the present invention in swept jet mode;

[0045] Figure 3 This is a schematic diagram of the device provided in the embodiment of the present invention in steady jet mode.

[0046] In the diagram: 1. Air intake port; 2. Mixing chamber; 3. Feedback loop; 4. Jet port; 5. Static pressure chamber; 6. Static pressure chamber wall; 7. Static pressure hole; 8. Flexible membrane. Detailed Implementation

[0047] The present invention will be further described below with reference to the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and should not be used to limit the scope of protection of the present invention.

[0048] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are only for the convenience of describing the invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0049] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0050] Example 1

[0051] This embodiment introduces a self-excited jet device with adaptive switching of jet modes, comprising: an air intake 1, a mixing chamber 2, and a jet outlet 4 located sequentially along the central axis of the device, forming the main flow path; static pressure chambers 5 and feedback loops 3 surrounding the static pressure chambers 5 are respectively provided on both sides of the mixing chambers 5. The static pressure chambers 5 are hollow structures formed by a surrounding static pressure chamber wall 6, and a certain number of static pressure holes 7 are opened on the static pressure chamber wall 6. A flexible membrane 8 is installed on the side of the static pressure chamber wall 6 closest to the central axis, wherein:

[0052] When different air inlet pressures are applied to the air inlet 1 of the device, the flexible membrane 8 exhibits different modes of being close to or far from the static pressure chamber wall 6, thereby generating a swept jet or a steady jet at the jet inlet for fluid flow control.

[0053] The static pressure chamber 5 is filled with fluid having a static pressure P0, which is a fixed value or a pressure value associated with the external flow field controlled by the self-excited jet device.

[0054] The static pressure on the side of the flexible membrane 8 away from the central axis is equal to the static pressure P0 in the static pressure chamber 5. The average static pressure on the side of the flexible membrane 8 near the central axis is set to P1. When the pressure applied to the air inlet 1 is relatively high, P1 ≥ P0. u At this time, the flexible membrane 8 is in a state of close contact with the static pressure chamber wall 6, and the jet port 4 generates a sweeping jet with a certain frequency. When the pressure given by the air intake port 1 is low, such that P1≤P s At this time, the flexible membrane 8 is in a state far away from the static pressure chamber wall 6, and the jet port 4 generates a steady jet, wherein: P u With the jet ejector in the minimum flow state of swept jet mode, the average static pressure P near the central axis of the flexible membrane 8 is... u ;P s This represents the average static pressure near the central axis of the flexible membrane 8 when the jet injector just enters the steady jet mode. Wherein:

[0055] When the jet injector is in the minimum flow state of the swept jet mode, the average static pressure P near the central axis of the flexible membrane 8 is... u The calculation formula is as follows:

[0056] Pu ≈P0+F0 / R0

[0057] Where F0 is the tension of the flexible membrane 8 when it is in close contact with the static pressure cavity wall 6, and R0 is the average radius of curvature of the pressure cavity wall 6 near the central axis.

[0058] The formula for calculating the average static pressure near the central axis of the flexible membrane 8 when the jet injector just enters the steady jet mode is as follows:

[0059] P s =P0-F c / R c

[0060] Among them, R c For the flexible membrane 8, when the throat width is equal to h, the radius of curvature F of the flexible membrane 8 is... c The tension of the flexible membrane is given when the throat width of the flexible membrane 8 is equal to h, where h is the throat width of the flexible membrane 8 corresponding to the jet injector entering the steady jet mode.

[0061] The technical principle of this invention is as follows: When the pressure at the air inlet 1 is relatively high, the flexible membrane 8 is in a state of close contact with the static pressure chamber wall under the action of the pressure difference on both sides. Figure 2 As shown, due to the Coanda effect, the inlet airflow adheres to either the left or right wall of the mixing chamber 2. Due to the feedback loop 3, the airflow alternates along different paths at a certain frequency, forming an unsteady swept jet at the jet inlet 4—the principle of a conventional feedback self-excited jet ejector. At this point, the flow loss within the ejector is relatively high due to fluid oscillation. When the pressure at the air inlet 1 is low, the flexible membrane 8 is positioned far from the static pressure chamber wall under the pressure difference on both sides. Figure 3 As shown, since the fluid in the mixing chamber cannot alternate between the two side walls through the Coanda effect, a steady jet is generated at the jet outlet, and the flow loss is low in the ejector due to the absence of fluid oscillation. In summary, this self-excited ejector can switch between a high-loss, swept jet mode and a low-loss, steady jet mode according to different input pressures, thereby adapting to different flow conditions of the controlled object.

[0062] The beneficial effects achieved by this invention are as follows: This invention is a self-excited jet device with adaptive switching of jet modes. This device can adaptively adjust the jet mode according to different air inlet pressures, thereby solving the problem of low or even negative returns of existing self-excited jet devices for separation flow control under varying operating conditions, and has stronger engineering practicality.

[0063] The following description, in conjunction with a preferred embodiment, illustrates the content involved in the above embodiments.

[0064] like Figure 1As shown, a self-excited jet device with adaptive switching of jet modes includes an air intake 1, a mixing chamber 2, a feedback loop 3, a jet inlet 4, a static pressure chamber 5, a static pressure chamber wall 6, a static pressure orifice 7, and a flexible membrane 8. The air intake 1, mixing chamber 2, feedback loop 3, and jet inlet 4 are components found in conventional self-excited jet oscillators with feedback loops. These components can be scaled down based on the sweeping jet flow rate and frequency required by the controlled object (such as a compressor) for flow control.

[0065] like Figure 1 As shown, the static pressure chamber 5 is a hollow structure formed by a surrounding static pressure chamber wall 6, and a certain number of static pressure holes 7 are opened on the static pressure chamber wall 6. The size and number of static pressure holes 7 are optimized to ensure that the static pressure on the side of the flexible membrane 8 far from the central axis can quickly match the static pressure P0 inside the static pressure chamber 5, and to ensure that the flexible membrane 8 does not enter the interior of the static pressure chamber 5. The static pressure P0 can be associated with the external flow field controlled by the self-excited jet device, for example, by induced air, so that the static pressure P0 is equal to the outlet static pressure of the jet port 4 (i.e., the back pressure of the jet outlet).

[0066] like Figure 2 As shown, the average radius of curvature R0 of the static pressure chamber wall 6 near the central axis is calculated based on the jet geometry. Through numerical simulation, given a fixed value P0 for the outlet static pressure of the jet inlet 4 and the static pressure inside the static pressure chamber 5, the simulation is performed with the flexible membrane 8 in close contact with the static pressure chamber wall 6 and the jet in sweeping jet mode at minimum flow rate (corresponding to a total inlet pressure of P). iu *), Average static pressure P on the near-central axis side of flexible membrane 8 u Therefore, the tension F0 of the flexible membrane 8 (adhering tightly to the static pressure chamber wall) at this time satisfies: F0≈(P u -P0)×R0.

[0067] like Figure 3 As shown, the throat width h of the flexible membrane 8 corresponding to the jet nozzle entering the steady jet mode is determined by numerical simulation, and the average static pressure P near the central axis of the flexible membrane 8 at this time is calculated. s The radius of curvature R of the flexible membrane 8 c and the total pressure P at the ejector inlet is * Therefore, the tension F of the flexible membrane at this time can be obtained. c (The width of the flexible membrane throat is h) satisfies: F c ≈(P0-P s )×R c .

[0068] Through the above steps, by designing the tension F0 (adhering tightly to the hydrostatic cavity wall) and F of a given flexible membrane under two critical states, cWith a flexible membrane throat width of h, a self-excited jet device with adaptive jet mode switching can be obtained. The device can adaptively switch between steady jet mode and unsteady jet mode. Specifically, when the total pressure P at the jet inlet... i * Satisfies P i * <P is When * is in the steady jet mode (low flow loss inside the ejector), it is suitable for flow fields with low loss and good flow conditions (such as the compressor design point); while when the total pressure P at the ejector inlet is * iu * <P i When the jet enters unsteady swept jet mode (with higher flow losses inside the jet), it is suitable for high-loss flow fields with poor flow conditions (such as near the compressor stall point).

[0069] Example 2

[0070] This embodiment provides a design method for a self-excited jet device with adaptive switching of jet modes according to any one of Embodiments 1, including:

[0071] Calculate the average static pressure P near the central axis of the flexible membrane when the flexible membrane is in close contact with the hydrostatic chamber wall and the ejector is in sweeping jet mode at minimum flow. u ;

[0072] Through P u Calculate the tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber;

[0073] Calculate the average static pressure P near the central axis of the flexible membrane when the flexible membrane is far from the hydrostatic chamber wall and the jet injector has just entered the steady jet mode. s ;

[0074] Through P s Calculate the tension F of the flexible membrane when it is far from the wall of the hydrostatic chamber. c ;

[0075] By designing the tensions F0 and F of a given flexible membrane under two critical states... c A self-excited jet device with adaptive switching of jet modes was obtained, which can adaptively switch between steady jet mode and unsteady jet mode.

[0076] The method for calculating the tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber includes:

[0077] The average radius of curvature R0 of the hydrostatic chamber wall near the central axis is calculated based on the jet geometry.

[0078] Given the static pressure at the jet outlet and the static pressure P0 inside the static pressure chamber;

[0079] Numerical simulation was used to calculate the average static pressure P near the central axis of the flexible membrane when it was in close contact with the hydrostatic chamber wall and the jet was in sweeping jet mode at minimum flow. u ;

[0080] The tension F0 of the flexible membrane when it is in close contact with the wall of the hydrostatic chamber is calculated using the following formula:

[0081] F0≈(P u -P0)×R0.

[0082] Furthermore, the calculated tension F of the flexible membrane when it is far from the hydrostatic cavity wall is... c The methods include:

[0083] Given the static pressure at the jet outlet and the static pressure inside the static pressure chamber as P0;

[0084] The width h of the flexible membrane throat corresponding to the jet ejector entering the steady jet mode was determined by numerical simulation.

[0085] Calculate the radius of curvature R of the flexible membrane when the throat width is equal to h. c ;

[0086] The average static pressure P on the near-central side of the flexible membrane was calculated using numerical simulation when the flexible membrane was far from the wall of the hydrostatic chamber and the throat width was equal to h. s ;

[0087] Calculate the tension F of the flexible membrane when it is far from the wall of the hydrostatic chamber and the width of the larynx is equal to h. c The formula is as follows:

[0088] F c =(P0-P s )×R c .

[0089] The design method further includes:

[0090] The total inlet pressure P is obtained when the ejector just enters steady jet mode and the width of the flexible membrane throat is equal to h. is *And the total inlet pressure P corresponding to the ejector being in sweeping jet mode at minimum flow rate. iu *;

[0091] When the total pressure P at the ejector inlet i * Satisfies P i * <P is *At this time, the ejector enters steady jet mode;

[0092] When the total pressure P at the ejector inlet i * Satisfies P iu * <P i*At this time, the jet injector enters the unsteady swept jet mode.

[0093] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A self-excited jet device with adaptive switching of jet modes, characterized in that, include: The air intake (1), mixing chamber (2), and jet outlet (4) located sequentially along the central axis of the device form the main flow path; static pressure chambers (5) and feedback loops (3) surrounding the static pressure chambers (5) are respectively provided on both sides of the mixing chamber. The static pressure chamber (5) is a hollow structure formed by the surrounding static pressure chamber wall (6). A certain number of static pressure holes (7) are opened on the static pressure chamber wall (6), and a flexible membrane (8) is installed on the side of the static pressure chamber wall (6) near the central axis. When different air inlet pressures are given to the air inlet (1) of the device, the flexible membrane (8) exhibits different modes of being close to or far from the static pressure chamber wall (6), thereby generating a swept jet or a steady jet at the jet inlet for fluid flow control. The average static pressure on the near-central axis side of the flexible membrane (8) is set to P1. When the pressure at the air inlet (1) is relatively high, such that P1 ≥ P u At this time, the flexible membrane (8) is in a state of close contact with the static pressure chamber wall (6), and the jet port (4) generates a sweeping jet with a certain frequency. When the pressure given by the air intake port (1) is low, such that P1≤P s At this time, the flexible membrane (8) is in a state far away from the static pressure cavity wall (6), and the jet port (4) generates a steady jet, wherein: P u When the jet injector is in the minimum flow state of swept jet mode, the average static pressure P near the central axis of the flexible membrane (8) u ;P s The average static pressure on the near-central axis side of the flexible membrane (8) when the jet injector just enters the steady jet mode.

2. The self-excited jet device with adaptive switching of jet modes according to claim 1, characterized in that, The static pressure chamber (5) is filled with a fluid having a static pressure P0, which is a fixed value or a pressure value associated with the external flow field controlled by the self-excited jet device.

3. The self-excited jet device with adaptive switching of jet modes according to claim 2, characterized in that, The static pressure on the side of the flexible membrane (8) away from the central axis is equal to the static pressure P0 in the static pressure chamber (5).

4. The self-excited jet device with adaptive switching of jet modes according to claim 3, characterized in that, The jet injector is in the minimum flow state of the swept jet mode, and the average static pressure P on the near-central axis side of the flexible membrane (8) is... u The calculation formula is as follows: P u ≈P0+F0 / R0 Wherein, F0 is the tension of the flexible membrane (8) when it is in close contact with the static pressure cavity wall (6), and R0 is the average radius of curvature of the static pressure cavity wall (6) near the central axis.

5. The self-excited jet device with adaptive switching of jet modes according to claim 4, characterized in that, The formula for calculating the average static pressure near the central axis of the flexible membrane (8) when the jet injector just enters the steady jet mode is as follows: P s =P0-F c / R c Among them, R c F is the radius of curvature of the flexible membrane (8) when the throat width of the flexible membrane (8) is equal to h. c The tension of the flexible membrane (8) when the throat width is equal to h, where h is the throat width of the flexible membrane (8) when the jet nozzle just enters the steady jet mode.

6. A design method for a self-excited jet device with adaptive switching of jet modes according to any one of claims 1-5, characterized in that, include: The average static pressure P near the central axis of the flexible membrane (8) is calculated when the flexible membrane (8) is in close contact with the static pressure chamber wall (6) and the jet injector is in the minimum flow state of the swept jet mode. u ; Through P u Calculate the tension F0 of the flexible membrane (8) when it is in close contact with the wall (6) of the static pressure chamber; Calculate the average static pressure P on the near-central axis side of the flexible membrane (8) when the flexible membrane (8) is far from the static pressure chamber wall (6) and the jet injector has just entered the steady jet mode. s ; Through P s Calculate the tension F of the flexible membrane (8) when it is far from the hydrostatic cavity wall (6). c ; By designing the tensions F0 and F of a given flexible membrane under two critical states... c A self-excited jet device with adaptive switching of jet modes was obtained, which can adaptively switch between steady jet mode and unsteady jet mode.

7. The design method of the self-excited jet device with adaptive switching of jet modes according to claim 6, characterized in that, The method for calculating the tension F0 of the flexible membrane (8) when it is in close contact with the wall (6) of the hydrostatic chamber includes: The average radius of curvature R0 of the hydrostatic cavity wall (6) near the central axis is calculated from the geometry of the jet injector. Given the static pressure at the outlet of the jet (4) and the static pressure P0 in the static pressure chamber (5); The average static pressure P near the central axis of the flexible membrane (8) was calculated by numerical simulation when the flexible membrane (8) was in the mode of being in close contact with the static pressure chamber wall (6) and the jet was in the minimum flow state of the swept jet mode. u ; The tension F0 of the flexible membrane (8) when it is in close contact with the wall (6) of the static pressure chamber is calculated using the following formula: F0≈(P u -P0)×R0。 8. The design method of the self-excited jet device with adaptive switching of jet modes according to claim 6, characterized in that, The calculated tension F of the flexible membrane (8) when it is far from the hydrostatic cavity wall (6) is... c The methods include: Given the static pressure at the outlet of the jet (4) and the static pressure in the static pressure chamber (5) as P0; The throat width h of the flexible membrane (8) corresponding to the jet ejector entering the steady jet mode was determined by numerical simulation. Calculate the radius of curvature R of the flexible membrane (8) when the throat width is equal to h. c ; The average static pressure P on the near-central axis side of the flexible membrane (8) was calculated by numerical simulation when the flexible membrane (8) was in a state far from the wall of the static pressure chamber (6) and the throat width was equal to h. s ; Calculate the tension F when the flexible membrane (8) is far from the hydrostatic cavity wall (6) and the larynx width is equal to h. c The formula is as follows: F c =(P0-P s )×R c 。 9. The design method of the self-excited jet device with adaptive switching of jet modes according to claim 6, characterized in that, The design method further includes: The total inlet pressure P is obtained when the ejector just enters steady jet mode and the width of the flexible membrane throat is equal to h. is *And the total inlet pressure P corresponding to the ejector being in sweeping jet mode at minimum flow rate. iu *; When the total pressure P at the ejector inlet i * Satisfies P i * <P is *At this time, the ejector enters steady jet mode; When the total pressure P at the ejector inlet i * Satisfies P iu * <P i *At this time, the jet injector enters the unsteady swept jet mode.

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