Method for enhancing mixing in a cavity by plasma-based synthesis of a jet wave standing wave excitation

Abstract

An experimental model based on plasma synthetic jet array excitation is provided to promote the enhancement of cavity mixing. A wall shear stress sensor is arranged upstream of the leading edge of the cavity, a wall shear stress sensor is arranged on the rear vertical surface of the cavity, and a dynamic pressure sensor is arranged on the bottom surface of the cavity. By applying amplitude and phase modulation to different rows or columns of plasma synthetic jet exciters, a traveling wave standing wave excitation method is realized to intelligently enhance the mixing of the cavity. First, a plurality of groups of excitation parameters are randomly initialized and the flow control benefits are evaluated; second, a proxy model is constructed to predict the best combination of excitation parameters by means of an intelligent optimization algorithm; finally, the discharge trigger signal sequence of the power supply is solved in reverse, and the benefits are improved through iterative testing. The plasma synthetic jet traveling wave standing wave excitation method has higher penetration depth, stronger mixing ability, better adaptability, and is more intelligent, and can better meet the needs of flame stable combustion under the wide working boundary of a scramjet engine.

Description

Technical Field

[0001] This invention relates to the field of active flow control, and more particularly to a cavity mixing enhancement method based on plasma-synthesized jet wave standing wave excitation. Background Technology

[0002] Scramjet engines are the power plants for air-breathing hypersonic vehicles, typically operating at Mach numbers above 6. Because organizing combustion directly in supersonic airflow is extremely difficult, these engines often employ concave cavities as flame stabilizers, utilizing the recirculation zone within the cavity to achieve stable combustion of the fuel-air mixture. Plasma actuators, as a novel active flow control device, hold promise for achieving a wider range of stable combustion by promoting mixing in the concave cavity shear layer and increasing the recirculation zone area. In existing work, researchers have mostly arranged a group of pulsed arc plasma actuators at the leading edge of the cavity for flow control ([1] Kong, Y., Wu, Y., Zong, H., & Guo, S. (2022). Supersonic cavity shear layer control using spanwise pulsed spark discharge array. Physics of Fluids, 34(5). doi:10.1063 / 5.0088772. [2] Webb, N., & Samimy, M. (2017). Control of Supersonic Cavity Flow Using Plasma Actuators. AIAA Journal, 55(10), 3346-3355. doi:10.2514 / 1.J055720). Each arc actuator discharges synchronously to excite the KH instability of the separated shear layer and induce large-scale vortex structures. However, this control scheme has several obvious drawbacks. First, "weak penetration performance": The disturbance of the flow field by the pulsed arc plasma actuator is a thermal blocking effect. Limited by the heating area of ​​the arc plasma, it can only affect the area 2-5 mm away from the wall and cannot penetrate the supersonic boundary layer or affect the external flow. Second, "few excitation modes": The single-row plasma actuator arranged along the front edge of the cavity can only excite the two-dimensional spanwise unstable mode of the separation shear layer, and the effect of promoting mixing is very limited. Related studies have shown that there are also a large number of three-dimensional unstable modes in the cavity separation shear layer. If they can be excited by external disturbance, they will more effectively promote the mixing of the cavity flow ([3] Huang, X., & Zhang, X. (2008). Streamwise and spanwise plasma actuators for flow-induced cavity noise control. Physics of Fluids, 20(3). doi:10.1063 / 1.2890448). Third, "poor adaptability to complex operating conditions": The flight speed range of future hypersonic air-breathing aircraft is extremely wide, and the fixed array of arc plasma excitation cannot be optimized and adjusted according to the incoming flow state. Summary of the Invention

[0003] To address the shortcomings of traditional single-pulse arc control methods, such as weak penetration performance, limited excitation modes, and poor adaptability to complex operating conditions, this invention proposes using a high-energy plasma synthetic jet array to control the concave cavity, combined with artificial intelligence methods for adaptive adjustment of excitation parameters. Specifically, an experimental model for promoting cavity mixing enhancement through plasma synthetic jet array excitation is proposed. This model has an overall rectangular shape, with N... x ×N y A matrix consisting of plasma-synthetic jet exciters is symmetrically arranged along the centerline of the upper surface of the cavity, N x and N y These represent the number of rows and columns, respectively; the plasma synthesis jet exciter is embedded inside the cavity, and exerts a strong disturbance on the supersonic flow through a small jet orifice near the upper surface of the cavity; the direction of the plasma synthesis jet exciter's jet is not restricted; and

[0004] (1) A row of wall shear stress sensors is arranged upstream of the front edge of the cavity. They are symmetrically and uniformly distributed along the spanwise direction of the upper surface of the cavity and are located after the plasma synthetic jet array. The arrangement range of the sensors in the spanwise direction should be comparable to that of the plasma synthetic jet exciter array.

[0005] (2) Arrange a row of wall shear stress sensors on the rear facade of the cavity, and arrange them evenly along the flow centerline of the rear facade of the cavity.

[0006] (3) A row of dynamic pressure sensors is arranged on the bottom surface of the cavity along the central axis of the flow direction, and the dynamic pressure sensors are evenly distributed along the flow direction.

[0007] In one embodiment of the present invention, the direction of the jet is a vertical jet, or a jet with a certain tilt angle and deflection angle.

[0008] In another embodiment of the invention,

[0009] Exciter array row spacing L x and column spacing L y Set to 5-10 times the actuator aperture;

[0010] The jet orifice diameter is d = 1-3 mm;

[0011] The spacing between a row of wall shear stress sensors is smaller than the row spacing of the exciter;

[0012] The dynamic pressure sensors are spaced 20-50mm apart, with a total of 3-5 sensors.

[0013] In one specific embodiment of the present invention,

[0014] N x =N y =4;

[0015] The jet orifice diameter is 2mm;

[0016] The spacing between a row of wall shear stress sensors is 5mm;

[0017] The spacing between the wall shear stress sensors is 3mm;

[0018] There are a total of 3 dynamic pressure sensors.

[0019] A cavity mixing enhancement method based on plasma-synthetic jet array excitation is also proposed. This method is based on the cavity experimental model described above for promoting cavity mixing enhancement by plasma-synthetic jet array excitation. The principle of this method is as follows:

[0020] The upper surface of the rectangular body is flush with the inner wall of the experimental section of the supersonic wind tunnel. After the supersonic flow passes over the upper surface of the experimental model, flow separation occurs at the leading edge of the cavity, generating a shear layer. The upper part of the shear layer is the supersonic flow, and the lower part is the recirculation zone. As the shear layer develops downstream, KH vortices are generated due to flow instability. The KH vortices promote the mixing of fluids in different regions on both sides of the shear layer, namely the supersonic flow and the recirculation, causing the width of the shear layer to gradually increase. The shear layer adheres to the rear facade of the cavity, forming a reattachment line. From an instantaneous perspective, due to the continuous pulsation of the shear layer, the position of the reattachment line is also constantly moving. The greater the amplitude of its movement, the more intense the mixing in the cavity.

[0021] In one embodiment of the present invention, each plasma-synthetic jet exciter within the array is individually powered, and its discharge energy, frequency, and phase can be arbitrarily adjusted. When the discharge frequency and energy are the same, plasma-synthetic jet wave excitation can be achieved by applying phase modulation to exciters in different rows or columns of the array. Specifically, assuming the discharge period is T... d The phase difference between two adjacent exciters is set to ΔT = T. d / N, which enables plasma synthesis jet wave excitation propagating along the flow direction; if the phase difference between two adjacent rows of exciters is set to ΔT = T d / N, which enables plasma synthetic jet standing wave excitation propagating along the spanwise direction; furthermore, it can fix the discharge frequency and phase of the plasma synthetic jet exciter, and modulate the discharge energy of exciters in different rows or columns to achieve plasma synthetic jet standing wave excitation; at this time, it is assumed that the maximum jet velocity amplitude is U p The jet velocity of the exciter in the i-th column or i-th row should be set to U. i,max =U p sin(π·i / N).

[0022] In another embodiment of the present invention, the adaptive adjustment process of the excitation of the intelligent plasma synthetic jet array in supersonic cavity flow control is as follows:

[0023] Step 1: Randomly initialize several sets of incentive parameters and evaluate the benefits of flow control;

[0024] Several sets of excitation parameter combinations are randomly generated and loaded into the plasma synthetic jet excitation array; the output signal τ based on the wall shear stress sensor array... i i = 1, 2, ..., m, where m is the total number of wall pressure sensors. The flow wall friction resistance coefficient C is calculated according to formula (1). f,i ; Output signal p based on dynamic pressure sensor array j j = 1, 2, ..., n, where n is the total number of dynamic pressure sensors. The pressure pulsation intensity I at the bottom of the cavity is calculated according to formula (2). p The position of the next dot X r It can be approximately represented as the location where the minimum shear stress occurs in the wall shear stress sensor array;

[0025]

[0026]

[0027] Where ρ represents the gas density, U ∞ Represents the velocity of the supersonic incoming flow; RMS(·) represents the root mean square function;

[0028] Incoming wall friction resistance coefficient C f,i For the state parameters of the incoming flow, I p X r These two parameters are observed output parameters, reflecting the flow control benefits under the current sets of control inputs; specifically, pressure pulsation I... p The larger the value, the more likely it is to be a dotted position X r The closer to the upstream, the stronger the mixing in the concave cavity and the higher the flow control benefit;

[0029] Step 2: Construct a proxy model and use an intelligent optimization algorithm to predict the optimal combination of incentive parameters;

[0030] Construct a surrogate model of control input, incoming flow state, and observed output. Optimize the surrogate model using an intelligent optimization algorithm to find the optimal combination of excitation parameters that can achieve higher control benefits.

[0031] Step 3: Reverse-calculate the power supply discharge trigger signal sequence and improve profitability through iterative testing;

[0032] The optimal excitation parameter combination predicted by the surrogate model in step 2 is inversely solved to obtain the discharge trigger signal sequence of the power system; the discharge trigger signal obtained by inverse solution is loaded onto the plasma synthetic jet excitation array, and the response of the supersonic cavity flow is monitored; the above process is repeated until the flow control benefit E no longer increases; the flow control benefit is:

[0033] E=w1·ΔI p +w2·ΔX r

[0034] Where, ΔI p The increase in pressure pulsation intensity before and after excitation; ΔX r The change in the position of the additional point before and after the excitation; w1 and w2 are both weight coefficients in the range of 0-1.

[0035] In another embodiment of the present invention, if plasma synthesis jet wave excitation with a specified frequency and speed is to be achieved, the pulse width needs to be calculated first based on the discharge energy, and then the discharge phase difference of each exciter column needs to be calculated based on the number of exciter columns and the discharge period. With the pulse width, phase difference and frequency, the repetition frequency pulse signal that should be applied to each control port of the power supply system is obtained.

[0036] The advantages of this invention are as follows:

[0037] 1. Greater Penetration Depth: Traditional pulsed arc plasma excitation methods apply disturbances to the flow field through thermal blocking effects. Limited by the heating area of ​​the arc plasma, they can only affect a region 2-5 mm from the wall and cannot penetrate the supersonic boundary layer or affect the external flow. This invention applies disturbances to the external flow field through a supersonic plasma synthetic jet, achieving a penetration depth of 10-20 mm.

[0038] 2. Enhanced mixing capability: Traditional single-row plasma exciters can only excite two-dimensional spanwise unstable modes of the separated shear layer, resulting in extremely limited mixing effects. The method of this invention can achieve plasma-synthesized jet stream and standing wave excitation. Because it can excite three-dimensional unstable modes of the cavity separated shear layer and simultaneously improve the excitation frequency through flow superposition effects, it possesses a stronger flow mixing capability.

[0039] 3. Better adaptability and intelligence: Traditional single-row arc plasma excitation schemes mostly operate in synchronous triggering mode, with each exciter operating at a strictly consistent frequency and phase, lacking adjustment capabilities and exhibiting poor adaptability to complex incoming flow conditions. The plasma synthetic jet array excitation of this invention can automatically optimize and adjust parameters based on flow field feedback. Compared to traditional feedback-free control schemes, it has better adaptability and can better meet the requirements for stable flame combustion under the wide operating boundaries of scramjet engines. Attached Figure Description

[0040] Figure 1 A schematic diagram of a method for enhancing cavity mixing through plasma-synthetic jet array excitation is shown, wherein... Figure 1 (a) shows a side view of the method arrangement. Figure 1 (b) A top view showing the arrangement of the method;

[0041] Figure 2 The diagram shows a schematic of plasma synthetic jet stream excitation and standing wave excitation, in which... Figure 2 (a) illustrates plasma-synthesized radio wave excitation based on phase modulation. Figure 2 (b) illustrates the standing wave excitation of plasma synthetic jet based on amplitude modulation;

[0042] Figure 3 The block diagram of intelligent adaptive control for supersonic cavity flow is shown. Detailed Implementation

[0043] Figure 1 This diagram illustrates a method for enhancing mixing in a concave cavity using plasma-synthetic jet array excitation. The entire concave cavity experimental model is rectangular, with its upper surface flush with the inner wall of the supersonic wind tunnel experimental section. The concave cavity serves as the inner cavity of the supersonic wind tunnel experimental section. When used as a flame stabilizer, the length-to-depth ratio of the concave cavity is typically 3-8, and the rear facade has a certain inclination angle (30°-60°). After the supersonic incoming flow passes over the upper surface of the experimental model, flow separation occurs at the leading edge of the concave cavity, generating a shear layer. The upper part of the shear layer is the supersonic incoming flow, and the lower part is the recirculation zone. As the shear layer develops downstream, KH vortices (i.e., several vortex-shaped continuous lines of increasing size in the diagram) are generated due to flow instability. The KH vortices promote the mixing of fluids in different regions on both sides of the shear layer (i.e., the supersonic incoming and recirculation), causing the width of the shear layer to gradually increase. Finally, the shear layer adheres to the rear facade of the concave cavity, forming a reattachment line (e.g., ...). Figure 1 (b) shows the reattachment line, which serves as the boundary between the internal reflux flow and the external supersonic incoming flow. Its direction and position are closely related to the size of the reflux region inside the cavity (the further back the reattachment line is, the larger the area of ​​the reflux region inside the cavity). From an instantaneous perspective, due to the continuous pulsation of the shear layer, the position of the reattachment line is also constantly moving. The greater the amplitude of its movement, the more intense the mixing in the cavity.

[0044] To achieve co-enhancement, N is arranged upstream of the cavity. x ×N y A matrix of plasma-synthetic jet exciters is arranged symmetrically along the centerline of the upper surface of the cavity (which is along the inlet direction). Wherein, N x and N yThese represent the number of rows and columns, respectively. In this implementation case, N... x =N y =4. The plasma-synthetic jet exciter is embedded inside the cavity, and exerts strong disturbance on the supersonic incoming flow through a small jet orifice near the upper surface of the cavity. The direction of the jet is not limited; it can be a vertical jet or a jet with a certain tilt angle and deflection angle. The jet orifice shape is preferably circular, but it can also be designed as a slit or polygon, etc. The basic structure and working principle of the plasma-synthetic jet exciter are well known to those skilled in the art and will not be described in detail here. The typical range of the jet orifice diameter is d = 1-3 mm (2 mm is preferred in this case). The maximum jet velocity is positively correlated with the discharge heating energy, and is about 300-600 m / s. Due to the high jet velocity, the penetration depth of the plasma-synthetic jet in the supersonic incoming flow can easily reach 10-20 mm, far exceeding the height of the thermal blockage region (2-5 mm) caused by surface pulsed arc plasma excitation. From top to bottom, each row of the exciter array is represented by R. i (i = 1, 2, ..., N) x () refers to; from left to right, each column of the exciter array is represented by C. i (i = 1, 2, ..., N) y () refers to. To achieve effective connection of disturbances induced by different exciters, the line spacing L x and column spacing L y It should be set to 5-10 times the actuator aperture. Taking d=2mm as an example, the row spacing and column spacing should range from 10-20mm, with L being preferred. x =L y =10mm.

[0045] In this invention, each plasma synthesis jet exciter within the array is individually powered, and its discharge energy, frequency, and phase can be arbitrarily adjusted. When the discharge frequency and energy are the same, phase modulation can be applied to exciters in different rows or columns of the array to achieve the desired effect. Figure 2 (a) illustrates plasma-synthesized jet wave excitation. Specifically, it is assumed that the discharge period is T. d The phase difference between two adjacent exciters is set to ΔT = T. d / N can be used to achieve plasma synthesis jet wave excitation propagating along the flow direction; similarly, if the phase difference between two adjacent rows of exciters is set to ΔT = T d / N can be used to achieve plasma synthetic jet standing wave excitation propagating along the spanwise direction. Besides phase modulation, the discharge frequency and phase of the plasma synthetic jet exciter can be fixed, and the discharge energy (velocity amplitude modulation) of exciters in different rows or columns can be modulated to achieve plasma synthetic jet standing wave excitation. In this case, it is assumed that the maximum jet velocity amplitude is U. pThe jet velocity of the exciter in the i-th column or i-th row should be set to U. i,max =U p sin(π·i / N).

[0046] Compared to traditional single-row or single-column plasma excitation, the plasma synthetic jet wave / standing wave excitation method proposed in this invention has two advantages. First, it enhances the apparent frequency of the incoming boundary layer through the flow superposition effect. Based on Taylor's "frozen turbulence" hypothesis, the multiple spatial excitations experienced by the boundary layer during its propagation from upstream to downstream can be approximately converted into multiple excitations at the same spatial location in the time dimension. Therefore, the apparent frequency experienced by the incoming boundary layer is N times the discharge frequency of a single exciter. y Times, N y The first factor is the number of columns in the exciter array along the flow direction. The second factor is to excite three-dimensional perturbation modes to accelerate the instability velocity of the shear layer. The sensitivity of shear layer flow to three-dimensional perturbations with different spanwise wavenumbers varies greatly. By selecting the optimal perturbation based on the flow field state feedback, and applying the corresponding excitation to increase the perturbation growth rate, the purpose of increasing the shear layer entrainment rate and enhancing cavity mixing can be achieved.

[0047] The plasma-synthesized jet array excitation in this invention has a series of adjustable parameters, including maximum jet velocity, discharge frequency, spanwise spacing of the exciters, flow spacing, and phase difference. For different concave flow configurations and complex and variable flight conditions, these excitation parameters should also be adaptively adjusted to maintain optimal flow control performance and improve control robustness. Therefore, in Figure 1Three types of sensors are arranged in the experimental model as flow field feedback, as described in detail below. (1) A row of wall shear stress sensors is arranged upstream of the front edge of the concave cavity. They are symmetrically and uniformly distributed along the spanwise direction of the upper surface of the concave cavity and are located after the plasma synthetic jet array. The arrangement range of the sensors in the spanwise direction should be comparable to that of the plasma synthetic jet exciter array, and are used to monitor the state changes of the incoming flow boundary layer in real time. The greater the wall shear stress, the higher the incoming flow velocity, and the corresponding plasma synthetic jet intensity should also be increased. In terms of layout, the spacing of a row of wall shear stress sensors should be less than the row spacing of the exciter, preferably 5 mm. (2) A row of wall shear stress sensors is arranged on the rear facade of the concave cavity. They are uniformly arranged along the flow centerline of the rear facade of the concave cavity, and are used to detect the position of the separation line in real time. Since the wall shear stress near the separation line is close to 0, the real-time position of the separation line can be inferred from the position of the minimum value of the wall shear stress, and the pulsation amplitude of the separation line can be further calculated. The smaller the spacing of the wall shear stress sensors, the higher the recognition accuracy of the separation line. Under the current technology, a sensor spacing of 3 mm is preferred. (3) A row of dynamic pressure sensors is arranged along the central axis of the flow direction on the bottom surface of the concave cavity to quantitatively monitor the pressure pulsation intensity in the flow field. This index can be used to measure the control benefits of plasma synthetic jet array excitation. The typical spacing of the dynamic pressure sensors is 20-50 mm, and a total of 3-5 sensors are sufficient (preferably 3). The dynamic pressure sensors are evenly distributed along the flow direction.

[0048] Figure 3 The adaptive adjustment process of intelligent plasma synthetic jet array excitation in supersonic cavity flow control is presented. This adjustment process is jointly completed by the system body, observation output, feedback correction, and control input.

[0049] Step 1: Randomly initialize several sets of incentive parameters and evaluate the benefits of flow control;

[0050] Several sets of excitation parameter combinations (including jet velocity, momentum coefficient, excitation frequency, and other parameters required for the operation of the plasma synthetic jet array exciter) are randomly generated and loaded into the plasma synthetic jet excitation array. The output signal τ based on the wall shear stress sensor array... i (i = 1, 2, ..., m; where m is the total number of wall pressure sensors), the flow wall friction resistance coefficient C is calculated according to formula (1). f,i The output signal p based on the dynamic pressure sensor array j (j=1,2,…,n; where n is the total number of dynamic pressure sensors), the pressure pulsation intensity I at the bottom of the cavity is calculated according to formula (2). p The position of the next dot is X. r It can be approximately represented as the location where the minimum shear stress occurs in the wall shear stress sensor array, and the specific evaluation method is well known to those skilled in the art.

[0051]

[0052]

[0053] In formula (1), ρ represents the gas density, and U ∞ The value represents the speed of the supersonic incoming flow; RMS(·) in formula (2) represents the root mean square function.

[0054] Among the parameters obtained from the sensor above, the coefficient of frictional resistance of the incoming flow wall is C. f,i For the state parameters of the incoming flow, I p X r These two parameters are observed output parameters, reflecting the flow control benefits under the current sets of control inputs. Specifically, pressure pulsation I... p The larger the value, the more likely it is to be a dotted position X r The closer to the upstream, the stronger the mixing in the concave cavity and the higher the flow control benefits.

[0055] Step 2: Construct a proxy model and use an intelligent optimization algorithm to predict the optimal combination of incentive parameters;

[0056] A surrogate model is constructed, consisting of control inputs (jet velocity, momentum coefficient, excitation frequency, etc.), incoming flow conditions (incoming flow velocity, incoming flow wall friction coefficient), and observed outputs (pressure pulsation intensity and reattachment location). This surrogate model is then optimized using intelligent optimization algorithms (such as genetic algorithms, ant colony algorithms, simulated annealing algorithms, neural networks, etc.) to find the optimal combination of excitation parameters that achieves higher control benefits. Specific methods for constructing the surrogate model and for optimization are known to those skilled in the art and will not be elaborated further.

[0057] Step 3: Reverse-calculate the power supply discharge trigger signal sequence and improve profitability through iterative testing;

[0058] The optimal excitation parameter combination predicted by the surrogate model in step 2 is then reverse-engineered into a discharge trigger signal sequence for the power system. This reverse-engineering process is specific to the power system architecture. Figure 2(a) For example, to achieve plasma synthetic jet standing wave excitation at a specified frequency and speed, the pulse width must first be calculated based on the discharge energy, and then the discharge phase difference of each exciter column must be calculated based on the number of exciter columns and the discharge period. With the pulse width, phase difference, and frequency, the repetition rate pulse signal that should be applied to each control port of the power supply system is obtained. Similarly, those skilled in the art can also perform inverse calculation of the discharge trigger signal under plasma synthetic jet standing wave excitation. The discharge trigger signal obtained from the above inverse calculation is loaded onto the plasma synthetic jet excitation array, and the response of the supersonic cavity flow is monitored. The above process is repeated until the flow control benefit E no longer increases. The flow control benefit can be expressed in the following form:

[0059] E=w1·ΔI p +w2·ΔX r

[0060] Where, ΔI p The increase in pressure pulsation intensity before and after excitation; ΔX r The change in the position of the additional point before and after the excitation; w1 and w2 are both weight coefficients in the range of 0-1.

[0061] The plasma-synthetic jet in this invention can reach supersonic speeds and easily penetrate to a depth of 10-20 mm, which is 2-5 times higher than traditional methods. Secondly, the excitation array of the plasma-synthetic jet can be changed by setting the phase difference, which can excite multiple modes of the separated shear layer. Finally, the excitation parameters and array shape of the plasma-synthetic jet array can be intelligently optimized and adjusted according to the flow field sensor, which has good adaptability.

Claims

1. A cavity doping enhancement method based on plasma-synthesized jet array excitation, comprising a cavity experimental model for promoting cavity doping enhancement by plasma-synthesized jet array excitation. The model has a rectangular overall shape, and N is arranged upstream of the cavity. x ×N y A matrix consisting of plasma-synthetic jet exciters is symmetrically arranged along the centerline of the upper surface of the cavity, N x and N y These represent the number of rows and columns, respectively; the plasma synthesis jet exciter is embedded inside the cavity, and exerts a strong disturbance on the supersonic flow through a small jet orifice near the upper surface of the cavity; the direction of the plasma synthesis jet exciter's jet is not restricted; and (1) A row of wall shear stress sensors is arranged upstream of the front edge of the cavity. They are symmetrically and uniformly distributed along the spanwise direction of the upper surface of the cavity and are located after the plasma synthetic jet array. The arrangement range of the sensors in the spanwise direction should be equivalent to that of the plasma synthetic jet exciter array. (2) A row of wall shear stress sensors is arranged on the rear facade of the cavity, and they are evenly arranged along the flow center line of the rear facade of the cavity. (3) A row of dynamic pressure sensors is arranged on the bottom surface of the concave cavity along the central axis of the flow direction, and the dynamic pressure sensors are evenly distributed along the flow direction. Its features are, The principle of this method is as follows: The upper surface of the rectangular body is flush with the inner wall of the experimental section of the supersonic wind tunnel. After the supersonic flow passes over the upper surface of the experimental model, flow separation occurs at the leading edge of the cavity, generating a shear layer. The upper part of the shear layer is the supersonic flow, and the lower part is the recirculation zone. As the shear layer develops downstream, KH vortices are generated due to flow instability. The KH vortices promote the mixing of fluids in different regions on both sides of the shear layer, namely the supersonic flow and the recirculation, causing the width of the shear layer to gradually increase. The shear layer adheres to the rear surface of the cavity, forming a reattachment line. From an instantaneous perspective, due to the continuous pulsation of the shear layer, the position of the reattachment line is also constantly moving. The greater the amplitude of its movement, the more intense the mixing in the cavity. Each plasma-synthetic jet exciter within the array is individually powered, and its discharge energy, frequency, and phase can be arbitrarily adjusted. When the discharge frequency and energy are the same, plasma-synthetic jet excitation can be achieved by applying phase modulation to exciters in different rows or columns of the array. Specifically, assuming the discharge period is T... d Set the phase difference between two adjacent exciters to This means that plasma synthesis jet wave excitation propagating along the flow direction can be achieved; if the phase difference between two adjacent rows of exciters is set to This means that it can achieve plasma-synthetic jet standing wave excitation propagating along the spanwise direction; in addition, it can fix the discharge frequency and phase of the plasma-synthetic jet exciter, and modulate the discharge energy of exciters in different rows or columns to achieve plasma-synthetic jet standing wave excitation; at this time, it is assumed that the maximum jet velocity amplitude is U p The jet velocity of the exciter in the i-th column or i-th row should be set to .

2. The cavity doping enhancement method based on plasma-synthesized radio wave standing wave excitation as described in claim 1, characterized in that, The direction of the jet is either a vertical jet or a jet with a certain tilt angle and deflection angle.

3. The cavity doping enhancement method based on plasma-synthesized radio wave standing wave excitation as described in claim 1, characterized in that, Exciter array row spacing L x and column spacing L y Set to 5-10 times the actuator aperture; The jet orifice diameter is d = 1-3 mm; The spacing between a row of wall shear stress sensors is smaller than the row spacing of the exciter; The dynamic pressure sensors are spaced 20-50 mm apart, and there are a total of 3-5 sensors.

4. The cavity doping enhancement method based on plasma-synthesized radio wave standing wave excitation as described in claim 3, characterized in that, N x =N y =4; The jet orifice diameter is 2 mm; The spacing between a row of wall shear stress sensors is 5 mm; The spacing between the wall shear stress sensors is 3 mm; There are a total of 3 dynamic pressure sensors.

5. The cavity doping enhancement method based on plasma-synthesized radio wave standing wave excitation as described in claim 1, characterized in that, In supersonic cavity flow control, the adaptive adjustment process of the excitation of the intelligent plasma synthetic jet array is as follows: Step 1: Randomly initialize several sets of incentive parameters and evaluate the benefits of flow control; Several sets of excitation parameter combinations are randomly generated and loaded into the plasma synthetic jet excitation array; the output signal τ based on the wall shear stress sensor array... i i = 1, 2, ..., m, where m is the total number of wall pressure sensors. The flow wall friction resistance coefficient C is calculated according to formula (1). f,i ; Output signal p based on dynamic pressure sensor array j j=1,2,…,n, where n is the total number of dynamic pressure sensors. The pressure pulsation intensity I at the bottom of the cavity is calculated according to formula (2). p The position of the next dot X r It can be approximately represented as the location where the minimum shear stress occurs in the wall shear stress sensor array; （1） （2） in, Indicates gas density, Indicates the speed of a supersonic incoming stream; Represents the root mean square function; Incoming wall friction resistance coefficient C f,i For the state parameters of the incoming flow, I p X r These two parameters are observed output parameters, reflecting the flow control benefits under the current sets of control inputs; specifically, pressure pulsation I... p The larger the value, the more likely it is to be a dotted position X r The closer to the upstream, the stronger the mixing in the concave cavity and the higher the flow control benefit; Step 2: Construct a proxy model and use an intelligent optimization algorithm to predict the optimal combination of incentive parameters; Construct a surrogate model of control input, incoming flow state, and observed output. Optimize the surrogate model using an intelligent optimization algorithm to find the optimal combination of excitation parameters that can achieve higher control benefits. Step 3: Reverse-calculate the power supply discharge trigger signal sequence and improve profitability through iterative testing; The optimal excitation parameter combination predicted by the surrogate model in step 2 is inversely solved to obtain the discharge trigger signal sequence of the power system; the discharge trigger signal obtained by inverse solution is loaded onto the plasma synthetic jet excitation array, and the response of the supersonic cavity flow is monitored; the above process is repeated until the flow control benefit E no longer increases; the flow control benefit is: in, To determine the increase in the intensity of pressure pulsations before and after the excitation; To incentivize the change in the position of the additional point before and after; and All are weighting coefficients ranging from 0 to 1.

6. The cavity doping enhancement method based on plasma-synthesized radio wave standing wave excitation as described in claim 5, characterized in that, To achieve plasma synthesis jet wave excitation at a specified frequency and speed, the pulse width must first be calculated based on the discharge energy, and then the discharge phase difference of each exciter column must be calculated based on the number of exciter columns and the discharge period. With the pulse width, phase difference, and frequency, the repetition frequency pulse signal that should be applied to each control port of the power supply system can be obtained.

Images