CN110920869A - High-frequency array type combined arc discharge exciter and method for controlling interference instability of shock wave boundary layer - Google Patents
High-frequency array type combined arc discharge exciter and method for controlling interference instability of shock wave boundary layer Download PDFInfo
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- B64—AIRCRAFT; AVIATION; COSMONAUTICS
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- B64C21/00—Influencing air flow over aircraft surfaces by affecting boundary layer flow
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Abstract
The device for controlling the interference instability of the shock wave boundary layer by the high-frequency array type combined arc discharge exciter comprises a driving power supply (201), an exciter (203) and a circuit parameter control box (202). A high-frequency array type combined arc discharge exciter and a method for controlling the interference instability of the shock wave boundary layer are also provided. The invention aims to weaken the disturbance flow instability of the shock wave boundary layer, takes high-frequency array type arc discharge excitation as a control means, and realizes the excitation quasi-steady-state control effect by increasing the disturbance frequency.
Description
Technical Field
The invention relates to a plasma technology, in particular to a device and a method for controlling shock wave intensity by multi-path array type high-frequency pulse arc discharge.
Background
The supersonic/hypersonic technology represents the capability of developing and utilizing space in the future of a country, is an important mark for measuring the battle effectiveness and the viability of the military, and has wide application prospect and extremely important military value. The plasma impact flow control taking the supersonic speed/hypersonic speed technology as the application background has the characteristics of fast response, wide frequency band, high strength and the like. The low-frequency instability of the shock wave boundary layer is the research focus in recent years, and in the disturbance of the supersonic shock wave boundary layer, the shock wave root part usually generates a low-frequency oscillation phenomenon accompanied with the low-frequency movement of a flow structure due to the disturbance of the boundary layer. This motion is a major source of instability. The method has the advantages that the plasma impact flow is used for controlling and regulating the head shock wave motion of the aircraft, so that the key for reducing the flow instability and improving the performance of the aircraft is realized; the hypersonic aircraft taking the scramjet engine as power has obvious advantages, and compressed air passing through the air inlet channel passes through the isolation section and then is adjusted to be in a stable state suitable for working requirements of a combustion chamber. The plasma impact flow is used for controlling and regulating the shock wave motion in the isolation section, so that the flow separation is reduced, and the working efficiency of the engine can be further improved; the high-speed aircraft enters the atmosphere from the space, the surface of the aircraft bears the high temperature of thousands of degrees, and the plasma impact flow excitation is adopted as a thermal protection device of the head of the reentry orbit aircraft, so that the heat can be taken away, the wall surface heat exchange is reduced, the ablation and melting of the shell are prevented, and the service life of the aircraft is prolonged.
For high speed aircraft flow control, plasma actuators are required to have both high intensity and high frequency. At present, although the single-power multi-channel discharge technology is broken through, a flow direction array type combined plasma exciter is developed. The control on the whole front surface of the shock wave is realized, but the excitation frequency is still lower, the disturbance effect on the boundary layer in a standard and steady manner cannot be realized, and the control method becomes a key for restricting the shock wave control efficiency of the plasma exciter.
Disclosure of Invention
In view of the above, the present invention provides a high frequency array type arc discharge exciter, which is characterized by comprising a flat model 101, an electrode 102, a compression slope 103, and a transition strip 104, wherein the flat model 101, the electrode 102, the compression slope 103, and the transition strip 104 are provided
The flat plate model 101 is an insulating medium with a cylindrical small hole in the middle, and is of a roughly flat plate structure as a whole, and the front end of the flat plate model 101 is of a wedge-shaped structure;
an electrode 102, which is arranged in a cylindrical hole of the flat plate model 101 and is in tight fit; arranging a plurality of rows of cylindrical holes along the flow direction, wherein each row is M, M is an even number, each row of cylindrical holes are paired in pairs and divided into M/2 groups, two electrodes 102 of each group form a plasma exciter, the plasma exciter is hereinafter referred to as an exciter for short, the exciters are uniformly arranged along the flow direction, the row number is N, and N is determined according to actual needs; the two electrodes 102 of a plasma actuator comprise a positive electrode and a negative electrode;
a transition strip 104, which is located on the upper surface of the front end of the wedge structure of the flat plate model 101 and is installed along the expanding direction, wherein the width of the transition strip 104 is adjusted according to the thickness of the incoming flow boundary layer, and the length of the transition strip 104 is equal to the width of the flat plate model 101;
a compression slope 103 is installed at the upper surface of the rear end of the flat plate mold 101, and the width of the compression slope 103 is equal to the width of the flat plate mold 101.
In one embodiment of the present invention,
the length range of the flat plate model 101 is 250-600 mm, and the width range of the flat plate model is 80-220 mm;
the shape of the electrode 102 is cylindrical, the diameter is 0.5 mm-3 mm, the length is 3 mm-10 mm, and the electrode distance is not more than 10 mm;
the electrode spacing range of each group of exciters is 1-10 mm; the distance between two adjacent groups of exciters in the same row ranges from 0mm to 10 mm; the space between the exciters flowing to two adjacent rows is 10-25 mm;
the slope angle range of the compression slope 103 is 20-30 degrees;
the width of the transition strip 104 is adjusted according to the thickness of the incoming flow boundary layer, and the adjustment range is 1-6 mm.
In a particular embodiment of the present invention,
the length of the flat plate model 101 is 400mm, and the width of the flat plate model is 110 mm;
the diameter of the electrode 102 is 1mm, and the material of the electrode 102 is selected from bronze, stainless steel, platinum or tungsten;
the electrode distance of each group of exciters is 4 mm; the distance between two adjacent groups of exciters in the same row is 4 mm; the distance between the exciters flowing to two adjacent rows is 15 mm;
the ramp angle of the compression ramp 103 is 24 °;
Also provides a device for controlling the disturbance instability of the shock wave boundary layer by the high-frequency array type combined arc discharge exciter, which is characterized in that,
the driving power supply 201 is a high-frequency nanosecond pulse direct current source and provides energy for the whole exciter, the power supply adopts a self-loop design, and the discharge frequency is adjustable; the discharge circuit adopts a serial design;
the number of the N actuators 203-X is determined according to actual needs, electrodes of the actuators 203-X are connected in series, a positive electrode of a first actuator 203-1 is connected with a high-voltage output end of a power supply, a negative electrode of an Nth actuator 203-N is grounded, between the first actuator 203-1 and the Nth actuator 203-N, the negative electrode of the first actuator 203-1 is connected with a positive electrode of a second actuator 203-2, the negative electrode of the second actuator 203-2 is connected with a positive electrode of a third actuator 203-3, and the like;
and the circuit parameter control box 202 is used for controlling the operation of the whole circuit, giving input signals of set frequency, timing, energy and the like through the control box and outputting the input signals to the driving power supply 201, and the driving power supply 201 starts to output high-voltage pulse energy to be loaded to two ends of an exciter 203-X (X is 1 … N) so as to trigger the exciter to operate.
In addition, a high-frequency array type combined arc discharge exciter and a method for controlling the disturbance instability of a shock wave boundary layer thereof are also provided, and the method is characterized by comprising the following steps:
the method comprises the following steps: after the specified discharge frequency is input through the circuit parameter control box 202, the driving power supply 201 is started, and the excitation system starts to work; in order to ensure that all the exciters work normally, the incoming flow conditions should meet the corresponding air pressure state;
step two: one end of a 203-1 exciter connected with the output end of a driving power supply 201 is increased in voltage, the other end of the 203-1 exciter is in a low-voltage state, when the breakdown voltage of the exciter is reached, air between electrodes of a first exciter 203-1 is broken down, the air is converted into a conductor from an insulator, and the voltage of the electrode at the low-voltage end of the first exciter 203-1 begins to increase; meanwhile, the low-voltage ends of the second actuator 203-2 and the first actuator 203-1 are connected with the electrode voltage by a lead wire and are increased simultaneously; when the voltage across the electrodes of the second actuator 203-2 reaches its breakdown voltage, the air between the electrodes of the second actuator 203-2 breaks down; in the same working mode, the air between the electrodes of the rest exciters is broken down to form a complete discharge loop;
step three: the power supply loads energy on the exciter, air near the exciter is heated in an arc discharge mode to generate an instant gas heating effect, and a shock wave and a turbulent vortex structure with a sub-boundary layer scale are formed in the flow direction;
step four: the upstream turbulence boundary layer is continuously disturbed by the high-frequency energy vortex structure, the original state of the turbulence boundary layer is broken, the original structure and the high-frequency energy vortex generate a violent coupling effect, so that the thickness of the boundary layer is increased, more high-frequency vortex structures are generated, and the high-frequency vortex shedding phenomenon occurs before the turbulence boundary layer passes through the shock wave;
step five: the strong separation shock wave is weakened along with the change of the state of the boundary layer, and finally a flow direction high-frequency weak compression wave front is induced, so that the original one strong oblique shock wave is converted into a plurality of weak compression waves; meanwhile, by adopting array excitation, the vortex structure induced by excitation compresses a flow channel between adjacent exciters, so that turbulent mixing is enhanced, and the turbulent boundary layer is thickened while the momentum of the boundary layer is increased; thereby enhancing the capability of the boundary layer to resist the inverse pressure gradient induced by the shock wave, weakening the interference strength of the shock wave boundary layer to a certain extent and further reducing the instability; after high-frequency pulse array type shock wave excitation is applied, the effect of stable control on separated shock waves can be achieved.
The high-frequency array type combined arc discharge exciter and the method for controlling the shock wave thereof aim at weakening the disturbance flow instability of the shock wave boundary layer, and realize the excitation quasi-steady-state control effect by increasing the disturbance frequency by taking the high-frequency array type arc discharge excitation as a control means.
Drawings
FIG. 1 is a schematic diagram of a model of a high frequency pulsed arc plasma exciter in accordance with the present invention;
FIG. 2 is a schematic diagram of a driving circuit of the array plasma arc discharge exciter;
FIG. 3 is a graph comparing the structure of an applied high frequency pulsed arc excitation with a reference flow field, wherein FIG. 3(a) shows a transient reference flow field, FIG. 3(b) shows a transient excitation flow field, FIG. 3(c) shows an average reference flow field, and FIG. 3(d) shows an average excitation flow field;
FIG. 4 is a spatial frequency spectrum plot of an applied excitation flow field, where FIGS. 4(a), (b), (c), (d), (e), (f) show the spatial frequency spectrum plots at specified frequencies of 2kHz, 5kHz, 10kHz, 20kHz, 23kHz, 25kHz, respectively;
FIG. 5 is a theoretical model of high frequency pulsed surface arc excitation for supersonic flow control, where FIGS. 5(a), (b) show the reference and excitation states, respectively;
Detailed Description
In order to achieve the aim, the invention provides a control technology of an array type high-frequency pulse arc discharge plasma exciter on shock waves, which is technically characterized in that an exciter array type layout scheme is used, a relay effect on a boundary layer is realized by adopting an excitation mode of high-frequency pulses, and a quasi-steady disturbance effect is further formed on the boundary layer. The original one-way strong oblique shock wave is converted into a plurality of weak compression waves, and the disturbance flow instability of the shock wave boundary layer is weakened. The following describes an embodiment of the present invention with reference to fig. 1 and 2.
As shown in fig. 1, the insulating medium is a flat plate model 101 with a cylindrical small hole in the middle, and the electrode 102 is arranged in the cylindrical hole of the flat plate model 101 in tight fit; multiple rows of cylindrical holes are arranged along the flow direction, each row is M, M is an even number, every two rows of cylindrical holes are paired and divided into M/2 groups, two electrodes 102 (one is a positive electrode and the other is a negative electrode) in each group form a plasma exciter (hereinafter referred to as an exciter), the number of rows is N, and N is determined according to actual needs. The front end of the flat plate is in a wedge-shaped structure, the transition strip 104 is installed at the front end of the upper surface along the span direction, the width (i.e. the flow direction length) of the transition strip 104 can be adjusted according to the thickness of the incoming flow boundary layer, the adjustment range is 1-6 mm, preferably 4mm, and the length (i.e. the span direction length) of the transition strip 104 is generally equal to the width of the flat plate model 101. The flat plate model 101 is provided with a compression ramp 103 at the rear end thereof, and the width (i.e., the spanwise length) of the compression ramp 103 is generally equal to the width of the flat plate model 101. The material, shape and mounting of transition strap 104 and compression ramp 103 are well known to those skilled in the art and will not be described further. The supersonic flow strong separation shock waves are various, the most important is the separation shock waves induced by a two-dimensional compression corner, supersonic incoming flow flows through a flat plate model 101 with a certain length to form a turbulent flow boundary layer (formed by installing a transition strip 104 through a slot at the front end of the flat plate model 101), when the supersonic incoming flow passes through a compression inclined plane 103 installed at the rear end of the flat plate model 101, the air flow deflects to generate the separation shock waves, and the shock waves and the boundary layer further form interference flow. The exciters are mounted in cylindrical apertures in the plate upstream of the separation shock, and as mentioned above, the plurality of exciters are arranged uniformly in the flow direction with the spacing between adjacent exciters being in the range 10mm to 25mm, preferably 15 mm. The compression corner induced separation shock wave is taken as a research object, and the upper surface of the electrode 102 is flush with the upper wall surface of the flat plate 101, so that additional resistance cannot be generated, and the original flow field is not influenced.
In one embodiment of the invention, the plate length is in the range of 250 to 600mm, preferably 400mm in view of wind tunnel size and optimal conditions for start-up, and the plate width is in the range of 80 to 220mm, preferably 110mm in view of optimal blockage ratio at the nozzle outlet. The selectable range of the slope angle is 20-30 degrees, the slope angle of 24 degrees can generate obvious slope induced separation under the condition of supersonic incoming flow, typical flow field structures such as separation shock waves, reattachment shock waves and the like are obvious, and research objects are abundant, so that 24 degrees is the preferred angle for researching the disturbance flow of the shock wave boundary layer. The electrode distance range of each group of exciter electrodes is 1-4 mm, and the preferred value is 4 mm. The distance between two adjacent groups of exciters in the same row ranges from 0mm to 10mm, and the preferred value is 4 mm. The distance between the exciters flowing to two adjacent rows is 10-25 mm, and the optimal value is 15 mm.
The electrode material 102 is selected from bronze, stainless steel, platinum or tungsten. In order to generate a uniform arc form by discharging, the electrode is cylindrical, the diameter is 0.5-3 mm, the length is 3-10 mm, the electrode distance needs to be matched according to the air pressure and the capacity of a driving power supply, generally not more than 10mm, and the distance of 4mm is optimal in order to improve the energy utilization rate of an exciter. The working principle of the exciter is that gas is heated instantaneously by energy generated by arc discharge to form shock wave and vortex mass structures. The exciter utilizes the continuity to rapidly generate shock waves and vortex groups to apply disturbance to the boundary layer, thereby achieving the effect of specifically controlling the shock waves.
In one embodiment of the present invention, the arc discharge electrode 102 is a 1mm copper electrode with a 4mm electrode spacing.
Fig. 2 shows a schematic circuit diagram of a driver circuit of the actuator. Wherein
The driving power supply 201 is a high-frequency nanosecond pulse direct current source and supplies energy to the whole exciter, the output range of the power supply is 0-20kV, the power supply adopts a self-loop design, the discharge pulse width is 100ns, the rising edge and the falling edge are 50ns, the discharge frequency is adjustable, and the maximum excitation frequency is 50 kHz. The discharge circuit adopts a serial design.
The number of the actuators 203-X (such as 203-.
The circuit parameter control box 202 is used for controlling the work of the whole circuit, input signals of set frequency, timing sequence, energy and the like are given through the control box and output to the pulse power supply 201, the pulse power supply 201 starts to output high-voltage pulse energy to be loaded to two ends of an exciter 203-X (X is 1 … N), and the exciter is triggered to work.
In a specific example of the invention, the output voltage of the high-frequency nanosecond pulse direct-current source is 14kV, the peak current of a single pulse reaches 70A, the discharge time scale is 300ns, and the energy of the single pulse is calculated to be about 30mJ through a discharge voltage-current curve.
In an embodiment of the invention, in consideration of the high arc discharge temperature, the flat plate 101 is made of acrylic plastic acrylic, so that the flat plate has good high-temperature resistance and good insulation, and can effectively prevent a creepage phenomenon in an experimental process. The discharge electrodes in the exciter 203 are made of bronze materials, and copper wires are soft and convenient to install.
The output voltage of the high-frequency nanosecond pulse power supply is 14kV, and the working frequency is 10 kHz.
The method for controlling the disturbance instability of the shock wave boundary layer by the high-frequency array type combined arc discharge exciter comprises the following steps:
the method comprises the following steps: after a specified discharge frequency is input through the circuit parameter control box 202, the high-frequency nanosecond pulse power supply 201 is started, and the excitation system starts to work. For all actuators to work properly, the incoming flow conditions should satisfy the corresponding pressure conditions.
Step two: one end of an exciter 203-1 connected with the output end of a high-frequency nanosecond pulse power supply 201 is increased in voltage, the other end of the exciter 203-1 is in a low-voltage state, after the breakdown voltage of the exciter is reached, air between electrodes 203-1 is broken down, the air is converted into a conductor from an insulator, and the voltage of the electrode at the low-voltage end 203-1 begins to increase. At the same time, the low voltage terminals of the actuators 203-2 and 203-1 are connected to the electrode voltage by the lead wire and are raised. When the voltage across the electrode of actuator 203-2 reaches its breakdown voltage, the air breaks down between the electrodes of actuator 203-2. In the same way, the air between the other exciter electrodes will be broken down, forming a complete discharge loop.
Step three: the power supply loads energy on the exciter, air near the exciter is heated in an arc discharge mode, an instant gas heating effect is generated, shock waves and turbulent vortex structures with sub-boundary layer scales are formed in the flow direction, and due to high-frequency excitation, the vortex structures with the scales can be continuously formed in the boundary layer and blown to the position of the separated shock waves along with the incoming flow.
Step four: the upstream turbulence boundary layer is continuously disturbed by the high-frequency energy vortex structure, the original state of the turbulence boundary layer is broken, the original structure and the high-frequency energy vortex generate a violent coupling effect, so that the thickness of the boundary layer is increased, more high-frequency vortex structures are generated, and the high-frequency vortex shedding phenomenon is generated without passing through a shock wave.
Step five: the strong separation shock wave is weakened along with the change of the state of the boundary layer, and finally a flow direction high-frequency weak compression wave front is induced, so that the original one strong oblique shock wave is converted into a plurality of weak compression waves. Meanwhile, by adopting array excitation, the vortex structure induced by excitation compresses a flow channel between adjacent exciters, so that turbulent mixing is enhanced, and the turbulent boundary layer is thickened while the momentum of the boundary layer is increased. Thereby enhancing the capability of the boundary layer to resist the inverse pressure gradient induced by the shock wave, weakening the interference strength of the shock wave boundary layer to a certain extent and further reducing the instability. After high-frequency pulse array type shock wave excitation is applied, the effect of stable control on separated shock waves can be achieved.
DETAILED DESCRIPTION OF EMBODIMENT (S) OF INVENTION
Referring to fig. 1-2, the exciter model is mainly composed of a flat plate model 101 and an electrode 102. Two round holes are formed in the insulating flat plate, the diameter range of the surface electrode is 1-5 mm, the preferred value is 2mm, the center-to-center distance range of the two holes is 1-10 mm, and the preferred value is 4 mm. The upper end of the electrode 102 is flush with the upper surface of the flat plate model 101, so that clutter interference generated in a supersonic flow field is avoided.
As shown in FIG. 2, the output voltage of the high-frequency nanosecond pulse power supply is 0-20kV, and the excitation frequency is 0-50 kHz. One end (positive end) of an exciter 203-1 connected with the output end of the high-frequency nanosecond pulse power supply 201 is increased in voltage, the other end (negative end) is in a low-voltage state, when the breakdown voltage of the exciter is reached, air between electrodes of the exciter 203-1 is broken down, gas is converted into a conductor from an insulator, and the electrode voltage of the low-voltage end (negative end) of the exciter 203-1 starts to be increased. Meanwhile, the positive electrode of the actuator 203-2 is connected with the low-voltage end of the actuator 203-1 by a wire, so that the positive voltage of the actuator 203-2 rises simultaneously, and the negative voltage of the actuator 203-2 is in a low-voltage state. When the voltage across the electrode of actuator 203-2 reaches its breakdown voltage, the air breaks down between the electrodes of actuator 203-2. In the same way, the air between the other exciter electrodes will be broken down, forming a complete discharge loop. The layout mode of the exciters is 5 groups of flow directions, the distance between each group is 15mm, and the distance between the electrodes is 4 mm. When the power supply applies high voltage to two ends of the exciter, the high-frequency nanosecond pulse power supply outputs 14kV, and the exciting frequency is set to be 10 kHz. Flow direction 5 group exciters are punctured, and the power passes through the near air in electric arc discharge flash heating exciters surface, produces 5 groups of shock wave superposes to form a plurality of turbulent vortex structures, a plurality of turbulent vortex structures produce the coupling effect with boundary layer inner structure, change boundary layer initial condition, and then change the shock wave structure, change original one strong oblique shock wave into multichannel weak compression wave, weakened shock wave intensity. Fig. 3(b) is a transient schlieren image of a shock wave structure when the exciter works, the effect of controlling the shock wave by flow direction array type layout excitation is obvious in advantage, different from the control effect of single-group excitation, the disturbance effect of the array type layout on the shock wave structure is particularly prominent, the separation shock wave has an obvious bifurcation phenomenon, the flow control effect is also found to have a delay phenomenon, the control effect does not begin to appear until the control effect of the third pulse period, therefore, the reduction of the shock wave intensity is inevitably related to the cumulative effect of high-frequency excitation, if the excitation frequency is lower, a longer control interval exists between two adjacent excitations, the separation shock wave is easy to recover, and the quasi-stable control effect is difficult to realize. By comparative analysis of the striae (3000 pieces of time average statistics) before and after the excitation is applied in fig. 3(b), the position of the starting point of the strong separation shock wave rises by about 50mm from the reference state, and the shock wave near the wall surface almost appears in a vanishing state.
Fig. 4 shows spatial frequency spectrum diagrams at different specified frequencies with an excitation frequency of 10kHz, wherein fig. 4(a), (b), (c), (d), (e), (f) show the spatial frequency spectrum diagram distributions at specified frequencies of 2kHz, 5kHz, 10kHz, 20kHz, 23kHz, and 25kHz, respectively. It can be seen that under the array type excitation with the pulse frequency of 10kHz, the control effect of the shock wave is obvious, and the shock wave at the foot of the separated shock wave basically disappears. In terms of the pulsation frequency, when the maximum energy in the frequency spectrum appears when f is 10kHz, the maximum energy is mainly concentrated in the upper region and just coincides with the excitation frequency of the discharge, which shows that the pulsation frequency of the shock wave can be influenced to a certain extent by controlling the pulse discharge frequency, and the main oscillation frequency of the separated shock wave can be effectively changed from the low frequency to the high frequency. As can be seen from the space frequency spectrogram, the structure of the boundary layer becomes clear under the display of higher specified frequency, which shows that under the excitation action, the pulsation frequency of the boundary layer is increased compared with the reference flow field state, and presumably is caused by the increase of the turbulence degree of the boundary layer due to the continuous disturbance of high-frequency excitation.
Fig. 5 shows a theoretical model of supersonic shock wave controlled by excitation of high-frequency array type arc discharge plasma, wherein fig. 5(a) and (b) respectively show the theoretical models of supersonic flow in a reference state and an excitation state. The power supply loads energy on the exciter, air near the exciter is heated in an arc discharge mode, an instant gas heating effect is generated, shock waves and turbulent vortex structures with sub-boundary layer scales are formed in the flow direction, and due to high-frequency excitation, the vortex structures with the scales can be continuously formed in the boundary layer and blown to the position of the separated shock waves along with the incoming flow. The upstream turbulence boundary layer is continuously disturbed by the high-frequency energy vortex structure, the original state of the turbulence boundary layer is broken, the two structures have a violent coupling effect, so that the thickness of the boundary layer is increased, more high-frequency vortex structures are generated, and the high-frequency vortex shedding phenomenon is generated without passing through a shock wave. The strong separation shock wave is weakened along with the change of the state of the boundary layer, and finally a flow direction high-frequency weak compression wave front is induced, so that the original one strong oblique shock wave is converted into a plurality of weak compression waves. The low-frequency motion of the separated shock wave is inhibited, and the counter pressure gradient induced by the shock wave is weakened, so that the disturbance flow instability of the shock wave boundary layer is reduced.
Claims (5)
1. The high-frequency array type arc discharge exciter is characterized by comprising a flat model (101), an electrode (102), a compression inclined plane (103) and a transition strip (104), wherein
The flat plate model (101) is an insulating medium with a cylindrical small hole in the middle, and is of a roughly flat plate structure as a whole, and the front end of the flat plate model (101) is of a wedge-shaped structure;
the electrode (102) is arranged in the cylindrical hole of the flat plate model (101) in a tight fit manner; arranging a plurality of rows of cylindrical holes along the flow direction, wherein each row is M, M is an even number, every two rows of cylindrical holes are paired and divided into M/2 groups, two electrodes (102) of each group form a plasma exciter, the plasma exciter is hereinafter referred to as an exciter for short, the exciters are uniformly arranged along the flow direction, the row number is N, and N is determined according to actual needs; the two electrodes (102) of a plasma exciter comprise a positive electrode and a negative electrode;
the transition strip (104) is positioned on the upper surface of the front end of the wedge-shaped structure of the flat-plate model (101) and is installed along the expansion direction, the width of the transition strip (104) is adjusted according to the thickness of the incoming flow boundary layer, and the length of the transition strip (104) is equal to the width of the flat-plate model (101);
a compression slope 103 is installed at the upper surface of the rear end of the flat plate mold 101, and the width of the compression slope 103 is equal to the width of the flat plate mold 101.
2. The high frequency array-type combined arc discharge actuator of claim 1,
the length range of the flat plate model (101) is 250-600 mm, and the width range of the flat plate is 80-220 mm;
the shape of the electrode (102) is cylindrical, the diameter is 0.5 mm-3 mm, the length is 3 mm-10 mm, and the electrode distance is not more than 10 mm;
the electrode spacing range of each group of exciters is 1-10 mm; the distance between two adjacent groups of exciters in the same row ranges from 0mm to 10 mm; the space between the exciters flowing to two adjacent rows is 10-25 mm;
the slope angle range of the compression slope (103) is 20-30 degrees;
the width of the transition strip (104) is adjusted according to the thickness of the incoming flow boundary layer, and the adjusting range is 1-6 mm.
3. The high frequency array-type combined arc discharge actuator of claim 2,
the length of the flat plate model (101) is 400mm, and the width of the flat plate is 110 mm;
the diameter of the electrode (102) is 1mm, and the material of the electrode (102) is selected from bronze, stainless steel, platinum or tungsten;
the electrode distance of each group of exciters is 4 mm; the distance between two adjacent groups of exciters in the same row is 4 mm; the distance between the exciters flowing to two adjacent rows is 15 mm;
the slope angle of the compression slope (103) is 24 degrees;
the transition strip (104) is 4mm wide.
4. The device for controlling the disturbance instability of the shock wave boundary layer by the high-frequency array type combined arc discharge exciter is characterized in that,
the driving power supply (201) is a high-frequency nanosecond pulse direct current source and provides energy for the whole exciter, the power supply adopts a self-loop design, and the discharge frequency is adjustable; the discharge circuit adopts a serial design;
the number of the N is determined according to actual needs, electrodes of the exciters (203-X) are connected in series, positive electrodes of the first exciters (203-1) are connected with a high-voltage output end of a power supply, negative electrodes of the Nth exciters (203-N) are grounded, between the first exciters (203-1) and the Nth exciters (203-N), negative electrodes of the first exciters (203-1) are connected with positive electrodes of the second exciters (203-2), negative electrodes of the second exciters (203-2) are connected with positive electrodes of the third exciters (203-3), and the like;
and the circuit parameter control box (202) is used for controlling the operation of the whole circuit, input signals of set frequency, timing, energy and the like are given through the control box and output to the driving power supply (201), the driving power supply (201) starts to output high-voltage pulse energy to be loaded to two ends of the exciter (203-X, X is 1 … N), and the exciter is triggered to operate.
5. The high-frequency array type combined arc discharge exciter and the method for controlling the disturbance instability of the shock wave boundary layer thereof are characterized by comprising the following steps:
the method comprises the following steps: after the appointed discharge frequency is input through a circuit parameter control box (202), a driving power supply (201) is started, and an excitation system starts to work; in order to ensure that all the exciters work normally, the incoming flow conditions should meet the corresponding air pressure state;
step two: one end of an exciter (203-1) connected with the output end of a driving power supply (201) is increased in voltage, the other end of the exciter is in a low-voltage state, when the voltage reaches the breakdown voltage, air between electrodes of the first exciter (203-1) is broken down, the air is converted into a conductor from an insulator, and the voltage of the electrode at the low-voltage end of the first exciter (203-1) begins to increase; meanwhile, the low-voltage ends of the second actuator (203-2) and the first actuator (203-1) are connected with the electrode voltage by a lead and are increased simultaneously; when the voltage across the electrodes of the second exciter (203-2) reaches the breakdown voltage thereof, the air between the electrodes of the second exciter (203-2) breaks down; in the same working mode, the air between the electrodes of the rest exciters is broken down to form a complete discharge loop;
step three: the power supply loads energy on the exciter, air near the exciter is heated in an arc discharge mode to generate an instant gas heating effect, and a shock wave and a turbulent vortex structure with a sub-boundary layer scale are formed in the flow direction;
step four: the upstream turbulence boundary layer is continuously disturbed by the high-frequency energy vortex structure, the original state of the turbulence boundary layer is broken, the original structure and the high-frequency energy vortex generate a violent coupling effect, so that the thickness of the boundary layer is increased, more high-frequency vortex structures are generated, and the high-frequency vortex shedding phenomenon occurs before the turbulence boundary layer passes through the shock wave;
step five: the strong separation shock wave is weakened along with the change of the state of the boundary layer, and finally a flow direction high-frequency weak compression wave front is induced, so that the original one strong oblique shock wave is converted into a plurality of weak compression waves; meanwhile, by adopting array excitation, the vortex structure induced by excitation compresses a flow channel between adjacent exciters, so that turbulent mixing is enhanced, and the turbulent boundary layer is thickened while the momentum of the boundary layer is increased; thereby enhancing the capability of the boundary layer to resist the inverse pressure gradient induced by the shock wave, weakening the interference strength of the shock wave boundary layer to a certain extent and further reducing the instability; after high-frequency pulse array type shock wave excitation is applied, the effect of stable control on separated shock waves can be achieved.
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