Turbulent friction drag reduction device and method based on array corona discharge

Abstract

A turbulent friction drag reduction device based on array-type corona micro-blowing includes a corona discharge cavity plate (1) and a discharge electrode (2). The front of the corona discharge cavity plate (1) is provided with a plurality of cylindrical oblique micropores, which serve as anodes for corona discharge. These cylindrical oblique micropores are distributed in an array on the front of the corona discharge cavity plate (1), and the oblique directions of the cylindrical oblique micropores are staggered. A high-voltage DC power supply (4) generates a DC high voltage, which is applied to the discharge electrode (2), generating plasma (6) between the discharge electrode (2) and the corona discharge cavity plate (1). The two oblique jets of each discharge group are coupled to form a spirally rising jet, generating a normal blowing effect in the flow field, thereby achieving turbulent friction drag reduction. A turbulent friction drag reduction device and method based on array-type corona discharge are also provided. The present invention arranges sensors in the flow field to collect flow field data, senses the flow field state in real time, controls the corona discharge mode, maintains the best drag reduction effect under rapidly changing flow field states, and further improves the drag reduction adaptability.

Description

Technical Field

[0001] The present invention relates to the field of plasma flow control technology, in particular to a novel plasma actuator for turbulent boundary layer friction drag reduction, and specifically to a turbulent friction drag reduction device and method based on array corona discharge. Background Art

[0002] In the field of aerodynamics, drag reduction has always been a key goal in aircraft aerodynamic design. When cruising at subsonic speeds, approximately half of the drag is due to wall friction. Therefore, frictional drag is directly linked to fuel consumption. In the civil aviation industry, calculations show that 30% to 40% of a ticket price goes towards fuel costs. Reducing aircraft turbulent frictional drag can significantly increase aircraft range and flight time, reduce environmental pollution and fuel consumption, lower flight costs, and ultimately improve aircraft performance and economic efficiency.

[0003] To achieve aircraft drag reduction, various flow control methods have been developed, primarily categorized as passive and active. A typical passive flow control method is grooves. Grooves are flow-directed protrusions periodically arranged along the span of a wall. By separating the underlying strip structures of the turbulent boundary layer, they can achieve a drag reduction of approximately 8% to 10%. However, their adaptability is poor and their operating range is limited. Most grooves can only achieve optimal drag reduction within a narrow Reynolds number range. Once the designed Reynolds number is deviated due to factors such as flight speed, altitude, or weather changes, the drag reduction effect will be significantly reduced, or even increased. Furthermore, their perturbation effect is limited. As the incoming flow velocity increases, the fixed groove spacing cannot match the increasing spacing of the turbulent strip structures, making it difficult to effectively intervene in the turbulent boundary layer, thus losing the drag reduction effect. These changes are inevitable in actual flight, making simple grooves difficult to implement for drag reduction in real-world flight.

[0004] Typical active flow control methods include air blowing and spanwise wall oscillation, which are highly adaptable. Air blowing can achieve a 20% to 30% turbulent drag reduction, while spanwise wall oscillation can reduce turbulent frictional resistance by 45%. However, active control methods often require complex air bleed lines, air sources, motors, and complex mechanical structures. Furthermore, traditional air blowing methods require air to be drawn from the engine, which can compromise engine performance. The energy and cost required to drive air blowing and spanwise wall oscillation far outweigh the drag reduction benefits, making them impractical for practical application.

[0005] Plasma turbulence drag reduction is a new type of active drag reduction method with advantages such as simple structure and low drag reduction cost. It is the most promising turbulence drag reduction method for practical application and has become a research hotspot in recent years. Among plasma turbulence drag reduction methods, dielectric barrier discharge (DBD) is commonly used, which can achieve an 11% airfoil turbulence friction drag reduction effect at an incoming flow velocity of 20 m / s. However, due to the very limited intensity of DBD (the induced velocity is generally only 2-3 m / s), the drag reduction effect drops rapidly to 2.6% when the incoming flow velocity increases to 30 m / s. When the incoming flow velocity increases further, the drag reduction effect disappears. In addition, 90% of DBD is thermal effect, with low mechanical efficiency, making it difficult to implement in practical applications. Therefore, there is an urgent need to find more efficient and flexible plasma turbulence drag reduction methods to achieve efficient drag reduction at higher incoming flow velocities.

[0006] Numerous studies have shown that using microporous materials to generate normal micro-blowing on the wall of a turbulent boundary layer can significantly reduce the velocity and velocity pulsation at the bottom of the boundary layer, forming a low-velocity and low-pulsation zone at the bottom of the boundary layer, thereby effectively reducing turbulent frictional drag at higher incoming flow velocities. However, the generation of such micro-blowing generally requires complex piping to draw high-pressure gas from within the aircraft engine, which imposes a severe structural and weight burden on the aircraft while compromising engine performance. This makes the drag reduction gains difficult to offset the losses, making practical application difficult. Summary of the Invention

[0007] In view of the shortcomings of the existing technology, the present invention provides a turbulent friction drag reduction device based on array corona discharge, comprising a corona discharge cavity plate 1 and an electrode 2, wherein:

[0008] The corona discharge cavity plate 1 is in the shape of a thin rectangular parallelepiped; a plurality of cylindrical oblique micropores are opened on the front of the corona discharge cavity plate 1, which serve as the anode of the corona discharge. These cylindrical oblique micropores are distributed in an array on the front of the corona discharge cavity plate 1. The inclination direction and inclination angle of the cylindrical oblique micropores in the same row are the same, and their axes are parallel to each other and in the same horizontal vertical plane perpendicular to the front of the corona discharge cavity plate 1; the inclination angle of the cylindrical oblique micropores in the next row is the same as that of the previous row, and the inclination direction of the cylindrical oblique micropores in the next row is the same as that of the previous row. The inclination direction is symmetrical about a longitudinal vertical plane perpendicular to the front surface of the corona discharge cavity plate 1; when there are multiple rows of cylindrical oblique micropores, the inclination direction of the cylindrical oblique micropores is staggered according to the above situation; the number of rows of cylindrical oblique micropores is an even number; viewed from the front surface of the corona discharge cavity plate 1, a column of cylindrical oblique micropores is N, N is an even number, and from top to bottom, every two are grouped together to form N / 2 groups in total, and each group of cylindrical oblique micropores forms a pair of discharge electrode holes; the spacing between adjacent cylindrical oblique micropores between two groups is greater than the spacing between two adjacent cylindrical oblique micropores in each group;

[0009] A discharge electrode 2 is fixedly arranged under each cylindrical oblique micropore of the corona discharge cavity plate 1; there is a space between the discharge electrode 2 and the corona discharge cavity plate 1; the discharge electrode 2 and the lower surface of the cylindrical oblique micropore are coaxial; two adjacent discharge electrodes 2 with different oblique hole directions form a corona discharge group, each corona discharge group is connected in parallel or works independently, and each corona discharge group is independently controlled.

[0010] In one embodiment of the present invention, the thickness of the corona discharge cavity plate 1 is 1 to 5 mm; the diameter of each oblique micropore on the corona discharge cavity plate 1 is 1 to 5 mm; the distance between each group of two adjacent cylindrical oblique micropores on the corona discharge cavity plate 1 is 1 to 2 mm; the distance between two groups of adjacent cylindrical oblique micropores is 2 to 3 mm; in the horizontal direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 is 3 to 5 mm; in the vertical direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 is 3 to 5 mm;

[0011] The discharge electrode 2 has a diameter of 1 to 3 mm and a height of 1 to 3 mm; the distance between each electrode and the cylindrical micropore on the corresponding corona discharge cavity plate is 1 to 3 mm.

[0012] In a specific embodiment of the present invention, the corona discharge cavity plate 1 is made of copper, with a length of 27 mm, a width of 29 mm, and a thickness of 3 mm. The diameter of each oblique micropore on the corona discharge cavity plate 1 is 3 mm. The spacing between two adjacent cylindrical oblique micropores in each group on the corona discharge cavity plate 1 is 1 mm. The spacing between adjacent cylindrical oblique micropores between two groups is 2 mm. There are 30 cylindrical oblique micropores and 15 discharge groups. In the horizontal direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 is 3.5 mm. In the vertical direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 is 3.5 mm.

[0013] The discharge electrode 2 is a solid cylinder made of copper with a diameter of 1 mm and a height of 2 mm. The distance between each electrode and the cylindrical microhole on the corresponding corona discharge cavity plate is 2 mm.

[0014] In another embodiment of the present invention, the device is electrically connected as follows: a high-voltage DC power supply 4 generates a DC high voltage, one output end of which is connected to the corona discharge cavity plate 1 and the other end is connected to the discharge electrode 2 .

[0015] In another specific embodiment of the present invention, the high-voltage DC power supply 4 is a high-voltage DC power supply with a voltage greater than 8 kV.

[0016] In another embodiment of the present invention, the device is embedded in the surface requiring drag reduction, the front surface of the corona discharge cavity plate 1 is flush with the surface requiring drag reduction, and the device is arranged slightly upstream in the drag reduction area.

[0017] In addition, in one embodiment of the present invention, the circuit of the device is connected to the controller 3, and multiple small relays are arranged inside the entire circuit to respectively control the voltage polarity on the electrodes of each corona discharge electrode group 5; multiple small transformers are arranged to respectively control the DC voltage on each corona discharge cavity plate 1 and the corona discharge electrode 2; and sensors are arranged in the flow field to collect flow field data.

[0018] The working method of the above-mentioned turbulent friction drag reduction device based on array corona discharge is as follows:

[0019] For a single corona discharge group, the high-voltage DC power supply 4 generates a DC high voltage, which is applied to the discharge electrode 2. A strong electric field is generated between the discharge electrode 2 and the corona discharge cavity plate 1. The electric field strength exceeds the critical value, causing the air molecules to collide and ionize to produce a self-sustaining discharge, generating plasma 6 and forming an ion wind. The two oblique jets of each discharge group couple to form a spiral rising jet, producing a normal blowing effect in the flow field.

[0020] The high-voltage DC power supply 4 is turned on to ionize the air to generate plasma 6 to form ion wind. The two oblique jets of each discharge group are coupled to form a spirally rising normal jet, which washes the bottom fluid of the boundary layer upward to achieve turbulent friction drag reduction.

[0021] A turbulent friction drag reduction method based on array corona discharge is based on the above-mentioned turbulent friction drag reduction device based on array corona discharge, and the device operates in the following three modes:

[0022] Mode 1: When a high-voltage DC power supply 4 is connected, the corona discharge cavity plate 1 serves as the cathode, and the discharge electrode 2 serves as the anode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming a blowing effect. The plasma jets generated from the two inclined holes in each group are coupled to form a spirally rising normal vortex blowing;

[0023] Mode 2: When a high-voltage sinusoidal power supply is connected, the corona discharge cavity plate 1 serves as the cathode and the discharge electrode 2 serves as the anode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming a blowing effect. Plasma jets are generated from the two inclined holes in each group, which couple to form a spirally rising normal vortex blowing. The blowing intensity of each electrode group varies sinusoidally with the voltage.

[0024] Mode 3: When a high-voltage DC power supply 4 is connected, the corona discharge cavity plate 1 serves as the anode and the discharge electrode serves as the cathode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming an air absorption effect;

[0025] The method is specifically as follows:

[0026] Step S1: The sensor collects flow field data. The sensor is placed in the flow field to collect information such as temperature, pressure, velocity, wall shear stress, etc. in the flow field in real time, and inputs the data into the controller;

[0027] Step S2, the controller controls the circuit to select one of the three working modes, tries the three working modes in sequence and adjusts the voltage of each corona discharge group, the discharge density of the array corona discharge group and other parameters;

[0028] Step S3, the sensor collects flow field data again to collect flow field information after corona discharge;

[0029] In step S4, the controller analyzes the data collected by the sensor, compares the information before and after the corona discharge, and compares the changes in the friction resistance measured before and after the corona discharge under the temperature, pressure, and speed conditions. If the measured friction resistance is less than the friction resistance before the corona discharge, the expected drag reduction effect is achieved. Otherwise, the controller returns to step S2 and selects a new operating mode or a new discharge state based on the flow field information. The drag reduction effects of different modes are compared to select the optimal drag reduction mode. The selection method is as follows: when the aircraft is flying at high speed, the voltage needs to be increased, the density of the corona discharge group is increased, and a thicker air film is formed in the drag reduction arrangement area, which effectively reduces the viscous resistance between the air and the wall and meets the high-speed drag reduction requirement. When flying at low speed, a lower voltage is used and some corona discharge electrode groups are turned on to form an air film of a certain thickness in the drag reduction arrangement area, thereby meeting the drag reduction requirement and saving energy.

[0030] In one embodiment of the present invention, a surface shear stress sensor is used to measure the surface friction resistance.

[0031] The present invention utilizes corona discharge, which is more efficient than dielectric barrier discharge, to generate plasma micro-blowing in the flow field, thereby achieving turbulent friction drag reduction at a higher incoming flow velocity.

[0032] The electrode structure required for corona discharge is simple and has a low structural weight, which effectively reduces the weight and complexity of the system and improves the drag reduction effect. In addition, the adjacent blowing channels in the present invention can couple with each other to generate normal vortices, so that the low-speed area and low-pulsation area generated by the micro-jets are transmitted to higher places in the boundary layer, and effective drag reduction can be achieved at a smaller flow rate and a higher incoming flow velocity. The corona array turbulent friction drag reduction device has higher mechanical efficiency and can effectively generate normal jets, thereby achieving turbulent drag reduction. The present invention belongs to an active method with stronger adaptability. It can adjust the discharge intensity and density in real time according to the incoming flow conditions to adapt to the drag reduction needs under different incoming flow conditions. It can also achieve effective drag reduction in actual flight where the incoming flow conditions change rapidly. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1The overall structure diagram of the turbulent friction drag reduction device based on array-type corona micro-blowing is shown;

[0034] Figure 2 A diagram showing the electrode geometry;

[0035] Figure 3 Shows the geometric structure diagram of the corona discharge cavity plate;

[0036] Figure 4 A schematic diagram of the oblique micro-hole grouping of a turbulent friction drag reduction device based on array-type corona micro-blowing is shown;

[0037] Figure 5 The schematic diagram of the working of the turbulent friction drag reduction device based on array-type corona micro-blowing is shown;

[0038] Figure 6 A schematic diagram showing the installation position of a turbulent friction drag reduction device based on array-type corona micro-blowing is shown;

[0039] Figure 7 Showing the circuit diagram of the device of the present invention;

[0040] Figure 8 A schematic diagram showing the operation of a turbulent friction drag reduction device based on array-type corona micro-blowing when the DC voltages of each group are the same;

[0041] Figure 9 A schematic diagram of the operation of the turbulent friction drag reduction device based on array-type corona micro-blowing when modulating each group of DC high voltages is shown; a circuit diagram of the device of the present invention is shown;

[0042] Figure 10 The schematic diagram of the operation of the turbulent friction drag reduction device based on array-type corona micro-blowing is shown when the corona discharge cavity plate is connected to the cathode and the electrode is connected to the anode;

[0043] Figure 11 A flow chart of a turbulent friction drag reduction method based on array-type corona micro-blowing is shown;

[0044] Figure 12 A diagram showing the relationship between the various parts of the turbulent friction drag reduction method based on array corona micro-blowing is shown.

[0045] Description of the accompanying drawings:

[0046] 1. Corona discharge cavity plate 2. Electrode 3. Controller 4. High voltage DC power supply 5. Corona discharge group 6. Plasma 1), 2), 3), 4), 5) First, second, third, fourth, and fifth corona discharge groups DETAILED DESCRIPTION

[0047] The present invention provides an array-type corona discharge turbulent friction drag reduction device, comprising a corona discharge cavity plate 1, an electrode 2, such as Figure 1 shown.

[0048] like Figure 3 As shown, the corona discharge cavity plate 1 is a thin rectangular parallelepiped made of conductive metals such as copper, silver, and tungsten. A plurality of cylindrical oblique micropores are opened on the front of the corona discharge cavity plate 1, which serve as the anode of the corona discharge and the discharge electrode 2 to generate plasma. These cylindrical oblique micropores are distributed in an array on the front of the corona discharge cavity plate 1. The inclination direction and inclination angle of the cylindrical oblique micropores in the same row are the same, and their axes are parallel to each other and in the same horizontal vertical plane perpendicular to the front of the corona discharge cavity plate 1; the inclination angle of the cylindrical oblique micropores in the next row is the same as the inclination angle of the previous row, and the inclination direction of the cylindrical oblique micropores in the next row is symmetrical with the inclination direction of the previous row about the longitudinal vertical plane perpendicular to the front of the corona discharge cavity plate 1; when there are multiple rows of cylindrical oblique micropores (must be an even number of rows), the inclination direction of the cylindrical oblique micropores is staggered and changed according to the above situation, which will not be repeated. Viewed from the front of the corona discharge cavity plate 1 , a row of cylindrical oblique micropores must be an even number, for example, N. From top to bottom, two cylindrical oblique micropores form a group, forming a total of N / 2 groups. Each group of cylindrical oblique micropores forms a pair of discharge electrode holes.

[0049] The discharge electrode 2 is a solid needle, and a discharge electrode 2 is fixedly arranged under each cylindrical oblique microhole of the corona discharge cavity plate 1. There is a space between the discharge electrode 2 and the corona discharge cavity plate 1, and plasma 6 is generated between the discharge electrode 2 and the corona discharge cavity plate 1. Figure 2 As shown. The discharge electrode 2 is coaxial with the lower surface of the cylindrical oblique micropore. The discharge electrode 2 is usually made of copper or tungsten. Two adjacent discharge electrodes 2 with different oblique hole directions (the upper and lower discharge electrodes 2 shown in the figure) form a corona discharge group, as shown in FIG. Figure 4 As shown, each corona discharge group is connected in parallel or works independently, and each corona discharge group can be controlled independently.

[0050] High-voltage DC power supply 4 is used to generate a high DC voltage to drive the electrode array to discharge. One end of its output is connected to the corona discharge cavity plate 1, and the other end is connected to the discharge electrode 2. When high-voltage DC power supply 4 is connected, it ionizes the air between the corona discharge cavity plate 1 and the discharge electrode 2, generating plasma 6.

[0051] In a specific embodiment of the present invention, the corona discharge cavity plate 1 is made of copper, and its length ( Figure 4 The horizontal direction is the length direction) is 27mm; the width ( Figure 4The longitudinal direction is the width direction) is 29mm; the thickness can be 1 to 5mm, preferably 3mm, and 3mm is taken in this example. The diameter of each oblique micropore on the corona discharge cavity plate 1 can be 1 to 5mm, preferably 3mm, and 3mm is taken in this example. The distance between each group of two adjacent cylindrical oblique micropores on the corona discharge cavity plate 1 can be 1 to 2mm, preferably 1mm, and 1mm in this example. The distance between adjacent cylindrical oblique micropores between the two groups can be 2 to 3mm, preferably 2mm, and 2mm in this example. The distance between adjacent cylindrical oblique micropores between the two groups must be greater than the distance between two adjacent cylindrical oblique micropores in each group; there are 30 cylindrical oblique micropores and 15 discharge groups, such as Figure 4 As shown. In the transverse direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 can be 3-5 mm, preferably 3.5 mm, and in this example, 3.5 mm. In the longitudinal direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate 1 can be 3-5 mm, preferably 3.5 mm, and in this example, 3.5 mm.

[0052] The discharge electrodes 2 are made of copper and can have a diameter of 1 to 3 mm (1 mm in this example). They can be 1 to 3 mm tall (2 mm in this example). Each electrode corresponds to a cylindrical micropore on the corona discharge chamber plate and is coaxial with the lower surface of the oblique micropore, with a distance of 1 to 3 mm (2 mm in this example).

[0053] The high-voltage DC power supply 4 can select any high-voltage DC power supply with a voltage greater than 8kV. The volume and weight of the power supply should be as small as possible to reduce the structural weight cost of the device and adapt to application scenarios with limited space and load, such as drones.

[0054] First, the working process of a single corona discharge group, that is, the discharge electrodes 2 that are adjacent and have different oblique hole directions, after being energized is explained. Specifically, the high-voltage DC power supply 4 generates a DC high voltage, which is applied to the discharge electrode 2, generating a strong electric field between the discharge electrode 2 and the corona discharge cavity plate 1. The electric field strength exceeds the critical value, causing air molecules to collide and ionize, resulting in self-sustaining discharge, generating plasma 6, and forming an ion wind. The two oblique jets of each discharge group couple to form a spiral rising jet, producing a normal blowing effect in the flow field.

[0055] The discharge electrodes 2 are fixed correspondingly below the oblique micropores of the corona discharge cavity plate 1 in an array arrangement, thereby forming an array type corona discharge turbulent friction drag reduction device. Connect the high voltage DC power supply 4 to ionize the air to generate plasma 6 to form ion wind, such as Figure 5 As shown, the two oblique jets of each discharge group couple to form a spirally rising normal jet, which washes up the bottom fluid of the boundary layer and realizes turbulent friction drag reduction.

[0056] The array type corona discharge turbulent friction drag reduction device of the present invention is embedded into the surface where drag reduction is required, and the front surface of the corona discharge cavity plate 1 is flush with the surface where drag reduction is required, such as Figure 6 As shown. Since the drag reduction effect in the flow field can persist for a distance after leaving the device, the device of the present invention can be placed in a position slightly upstream of the drag reduction area in specific layout to save discharge energy and improve drag reduction efficiency.

[0057] In the specific implementation process, the circuit diagram is as follows Figure 7 As shown, the circuit of the turbulent friction drag reduction device of the array corona discharge of the present invention is connected to the controller 3, and a plurality of small relays are arranged inside the entire circuit, which can respectively control the voltage polarity on the electrodes of each corona discharge electrode group 5, wherein 1), 2), 3), 4), 5) the first, second, third, fourth, and fifth corona discharge groups are specific examples of the corona discharge electrode group 5; at the same time, a plurality of small transformers are arranged, which can respectively control the DC voltage on each electrode (corona discharge cavity plate 1 and corona discharge electrode 2). Sensors are arranged in the flow field to collect flow field data, and the temperature, pressure, velocity, wall shear stress and other information in the flow field are collected in real time, and the data are input into the controller 3. The data collected by the sensor is analyzed in the controller 3, and the appropriate working mode and parameters are selected by the control circuit accordingly to realize a complex control strategy. Therefore, in practical applications, the present invention provides multiple working modes, which can match the artificial intelligence algorithm to achieve more significant control effects.

[0058] Mode 1: When a high-voltage DC power supply 4 is connected, the corona discharge cavity plate 1 is the cathode, and the discharge electrode 2 is the anode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming a blowing effect. The plasma jets generated from the two inclined holes in each group are coupled to form a spiral rising normal vortex blowing, such as Figure 8 As shown (the bar graph in the figure is the voltage corresponding to each discharge group).

[0059] Mode 2: When a high voltage sinusoidal power supply is connected, the corona discharge cavity plate 1 is the cathode and the discharge electrode 2 is the anode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming a blowing effect. The plasma jets generated from the two inclined holes of each group are coupled to form a spiral rising normal vortex blowing. The blowing intensity of each group of electrodes changes sinusoidally with the voltage as shown in the following example: Figure 9 As shown (the bar graph in the figure is the voltage corresponding to each discharge group).

[0060] Mode 3: When a high voltage DC power supply 4 is connected, the corona discharge cavity plate 1 is the anode and the discharge electrode is the cathode, plasma 6 is generated between the corona discharge cavity plate 1 and the discharge electrode 2, forming an air inhalation effect. Figure 10 As shown (the bar graph in the figure is the voltage corresponding to each discharge group).

[0061] Based on the above device, the present invention also proposes a turbulent friction drag reduction method based on array corona micro-blowing, the process of which is as follows: Figure 11 shown.

[0062] In step S1, the sensor collects flow field data. The sensor is arranged in the flow field to collect information such as temperature, pressure, velocity, wall shear stress, etc. in the flow field in real time, and inputs the data into the controller.

[0063] Step S2 , the controller controls the circuit to select one of the three working modes, tries the three working modes in sequence and adjusts the voltage of each corona discharge group, the discharge density of the array corona discharge group and other parameters.

[0064] In step S3, the sensor collects flow field data again to collect flow field information after corona discharge.

[0065] Step S4 analyzes the data collected by the sensor in the controller, compares the information before and after the corona discharge, and compares the changes in the frictional resistance measured before and after the corona discharge under the temperature, pressure, and speed conditions. If the measured frictional resistance is less than the frictional resistance before the corona discharge, the expected drag reduction effect is achieved. Otherwise, return to step S2 and select a new operating mode or a new discharge state based on the flow field information. The drag reduction effects of different modes are compared to select the optimal drag reduction mode. The selection method is as follows: when the aircraft is flying at high speed, it is necessary to increase the voltage and increase the density of the corona discharge groups (the number of corona discharge groups turned on) to form a thicker air film in the drag reduction arrangement area, which can effectively reduce the viscous resistance between the air and the wall to meet the high-speed drag reduction requirements. When flying at low speeds, a lower voltage and opening of some corona discharge electrode groups can form a certain thickness of air film in the drag reduction arrangement area, achieving the drag reduction requirements and saving energy.

[0066] In one specific embodiment of the present invention, a surface shear stress sensor, such as a hot film sensor (publication number: CN111351609A), is used to measure surface frictional resistance. The changes in frictional resistance measured before and after corona discharge are compared. If the measured frictional resistance is less than the frictional resistance before corona discharge, the desired drag reduction effect is achieved and the process is complete. Otherwise, a new operating mode or a new discharge state is selected again from step S2 based on the flow field information until the desired drag reduction effect is achieved. Numerous studies have shown that in a turbulent boundary layer, micro-blowing of air normal to the wall can significantly reduce the velocity and velocity pulsation at the bottom of the boundary layer, forming a low-velocity and low-pulsation zone at the bottom of the boundary layer, thereby effectively reducing turbulent frictional resistance at higher incoming flow velocities.

[0067] During the implementation of the turbulent friction drag reduction method based on array corona discharge, the relationship between the various parts of the method is as follows: Figure 12 shown.

[0068] The present invention is different from other technologies in the same field as follows:

[0069] Among existing technologies, most turbulent drag reduction methods are simple, passive groove-based methods. Among technologies using plasma discharge for turbulent drag reduction, the discharge methods used are mostly dielectric barrier discharge and arc discharge. There is no technology using corona discharge for turbulent drag reduction. The present invention proposes an array-type corona micro-blowing turbulent friction drag reduction device and method. Each group of corona discharges generates plasma jets at oblique micropores, which couple with each other to form spiraling, normal vortex jets. This jet has a wider operating range and forms a thick air film in the drag reduction area, reducing frictional resistance between the air and the wall, thereby achieving efficient turbulent friction drag reduction.

[0070] Compared with other turbulent drag reduction methods, the present invention has the following advantages:

[0071] 1. Simpler structure and lower drag reduction cost. Compared with the air-bleed micro-blowing method, the array-type corona discharge turbulent friction drag reduction device and method proposed in this invention has significant advantages. The corona discharge adopts high mechanical efficiency, the coupled airflow can penetrate deeper into higher locations to reduce drag, and the structure is simple. It does not require air bleed from the engine and other parts, and the airflow channel is shorter without compromising engine performance.

[0072] 2. The effective incoming flow velocity is higher and the efficiency is higher. Compared with the plasma turbulent drag reduction method based on dielectric barrier discharge, the array-type corona discharge turbulent friction drag reduction device and method proposed in the present invention uses a higher corona discharge intensity, which can produce effective disturbances at a higher incoming flow velocity, thereby generating a wider effective drag reduction incoming flow velocity range. This effectively solves the problems of low discharge intensity and extremely limited effective drag reduction speed range existing in the existing plasma turbulent drag reduction technology based on dielectric barrier discharge, and has a stronger application prospect in the drag reduction application of various types of aircraft.

[0073] 3. Rapid response and flexible control. Since the corona electrode of the present invention can be controlled by the power supply electrical signal, compared with other turbulent drag reduction devices such as traditional methods such as blowing and suction, oscillating wall, piezoelectric synthetic jet, etc., the corona plasma actuator of the present invention has the advantages of simple structure, high frequency response, and fast response speed. It can produce a discharge effect within microseconds and achieve a rapid response to the flow field. This rapid response capability enables the present invention to reach the optimal design state more quickly and achieve better drag reduction effect. It also makes it possible to combine the present invention with various intelligent control methods such as deep reinforcement learning.

[0074] 4. Greater adaptability. Compared with traditional passive groove drag reduction methods, the array-type corona discharge turbulent friction drag reduction device and method proposed in this invention is an active method. It can adjust the discharge intensity and density in real time according to the flow field changes during actual flight, and change the control mode to meet the drag reduction needs. It can effectively adapt to the rapidly changing flow field conditions during actual flight, and maintain the optimal drag reduction state at all times, which has significantly enhanced adaptability and practicality.

[0075] The principle of corona discharge can be used to ionize air to form plasma. The charged particles in the plasma move under the action of the electric field and collide with air molecules, thereby accelerating the air. This phenomenon is also called "ion wind". The present invention uses the principle of corona discharge to generate ion wind, accelerates the air through corona discharge, and combines it with microporous materials to generate normal microjets, thereby reducing the friction resistance under turbulent conditions. Since the electrode structure required for corona discharge is very simple, the structural weight of the high-voltage package that drives the corona discharge is also very small. At the same time, it can also draw air nearby the surface of the wing or fuselage. Therefore, the use of corona discharge to generate microjets can achieve the function of micro-blowing drag reduction at a very low structural weight cost, effectively reducing the weight and complexity of the system, improving the drag reduction effect, and making it have practical application capabilities. In addition, unlike the typical micro-jet drag reduction method that uses normal-parallel inclined holes, the adjacent blowing channels in the present invention are coupled with each other, thereby generating normal vortices. By utilizing this vortex structure, the low-speed and low-pulsation areas generated by the microjet can be transferred to higher places in the boundary layer, thereby enhancing its ability to resist high-speed incoming flow, thereby achieving effective drag reduction at a higher incoming flow velocity with a smaller flow rate.

[0076] Compared to typical plasma turbulence drag reduction methods based on dielectric barrier discharge (DBD), the corona array turbulence friction drag reduction device provided by the present invention has higher mechanical efficiency and is also more flexible, capable of achieving drag reduction at higher incoming flow velocities. Furthermore, typical DBD drag reduction methods are passive, inevitably forming a drag-increasing zone while producing a drag reduction effect. However, the corona microjets generated by the present invention are active, achieving drag reduction without being limited by the drag-increasing effect. Compared to the invention patent "Multi-layer Array Microporous Discharge Plasma Generator and Generation Method" (Publication No.: CN 113543442A), which is entirely based on DBD and has low mechanical efficiency. Furthermore, due to its lack of a unidirectional electric field, it cannot produce an effective normal jet. The corona array turbulence friction drag reduction device provided by the present invention has higher mechanical efficiency and can effectively generate a normal jet, thereby achieving turbulent drag reduction. Compared to typical air-entrained micro-blowing methods, the present invention does not require air to be drawn from the engine or other parts, resulting in a shorter airflow channel and a significantly reduced structural weight of the device without compromising engine performance, significantly improving drag reduction efficiency. Compared with traditional passive control methods such as groove drag reduction, the present invention is an active method with stronger adaptability. It can adjust the discharge intensity and density in real time according to the incoming flow conditions to meet the drag reduction needs under different incoming flow conditions. It can also achieve effective drag reduction in actual flight where the incoming flow conditions change rapidly.

Claims

1. A turbulent friction drag reduction device based on array corona discharge, comprising a corona discharge cavity plate (1) and an electrode (2), characterized in that: The corona discharge cavity plate (1) is in the shape of a thin rectangular parallelepiped; a plurality of cylindrical oblique micropores are provided on the front side of the corona discharge cavity plate (1) as anodes of corona discharge, and these cylindrical oblique micropores are distributed in an array on the front side of the corona discharge cavity plate (1); the inclination direction and inclination angle of the cylindrical oblique micropores in the same row are the same, and their axes are parallel to each other and are in the same horizontal vertical plane perpendicular to the front side of the corona discharge cavity plate (1); the inclination angle of the cylindrical oblique micropores in the next row is the same as the inclination angle of the previous row, and the inclination direction of the cylindrical oblique micropores in the next row is symmetrical with the inclination direction of the previous row about the longitudinal vertical plane perpendicular to the front side of the corona discharge cavity plate (1); when there are multiple rows of cylindrical oblique micropores, the inclination directions of the cylindrical oblique micropores are staggered and changed according to the above situation; The number of rows of cylindrical oblique micropores is an even number; when viewed from the front of the corona discharge cavity plate (1), there are N cylindrical oblique micropores in a row, where N is an even number, and two cylindrical oblique micropores are grouped together from top to bottom, forming a total of N / 2 groups, and each group of cylindrical oblique micropores forms a pair of discharge electrode holes; the spacing between adjacent cylindrical oblique micropores in two groups is greater than the spacing between two adjacent cylindrical oblique micropores in each group; A discharge electrode (2) is fixedly arranged under each cylindrical oblique micropore of a corona discharge cavity plate (1); a space is provided between the discharge electrode (2) and the corona discharge cavity plate (1); the discharge electrode (2) and the lower surface of the cylindrical oblique micropore are coaxial; two adjacent discharge electrodes (2) with different oblique hole directions form a corona discharge group, each corona discharge group is connected in parallel or works independently, and each corona discharge group is independently controlled.

2. The turbulent friction drag reduction device based on array corona discharge according to claim 1, characterized in that: The thickness of the corona discharge cavity plate (1) is 1 to 5 mm; the diameter of each oblique micropore on the corona discharge cavity plate (1) is 1 to 5 mm; the distance between each group of two adjacent cylindrical oblique micropores on the corona discharge cavity plate (1) is 1 to 2 mm; the distance between two groups of adjacent cylindrical oblique micropores is 2 to 3 mm; in the horizontal direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate (1) is 3 to 5 mm; in the vertical direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate (1) is 3 to 5 mm; The discharge electrode (2) has a diameter of 1 to 3 mm and a height of 1 to 3 mm; the distance between each electrode and the cylindrical micropore on the corresponding corona discharge cavity plate is 1 to 3 mm.

3. The turbulent friction drag reduction device based on array corona discharge according to claim 2, characterized in that: The corona discharge cavity plate (1) is made of copper, with a length of 27 mm, a width of 29 mm, and a thickness of 3 mm. The diameter of each oblique micropore on the corona discharge cavity plate (1) is 3 mm. The distance between each group of two adjacent cylindrical oblique micropores on the corona discharge cavity plate (1) is 1 mm. The distance between two adjacent cylindrical oblique micropores is 2 mm. There are 30 cylindrical oblique micropores and 15 discharge groups. In the horizontal direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate (1) is 3.5 mm. In the vertical direction, the distance between the center of the first and last cylindrical holes and the edge of the corona discharge cavity plate (1) is 3.5 mm. The discharge electrode (2) is a solid cylinder made of copper with a diameter of 1 mm and a height of 2 mm; the distance between each electrode and the cylindrical microhole on the corresponding corona discharge cavity plate is 2 mm.

4. The turbulent friction drag reduction device based on array corona discharge according to claim 1, characterized in that: The device is electrically connected as follows: a high-voltage DC power supply (4) generates a DC high voltage, one output end of which is connected to a corona discharge cavity plate (1), and the other end is connected to a discharge electrode (2).

5. The turbulent friction drag reduction device based on array corona discharge according to claim 1, characterized in that: The high-voltage direct current power supply (4) is a high-voltage direct current power supply with a voltage greater than 8 kV.

6. The turbulent friction drag reduction device based on array corona discharge according to any one of claims 1 to 5, characterized in that: The device is embedded in the surface where drag reduction is required, the front surface of the corona discharge cavity plate (1) is flush with the surface where drag reduction is required, and the device is arranged at a position slightly upstream in the drag reduction area.

7. The turbulent friction drag reduction device based on array corona discharge according to any one of claims 1 to 5, characterized in that: The circuit of the device is connected to a controller (3), and a plurality of small relays are arranged inside the entire circuit to respectively control the voltage polarity on the electrodes of each corona discharge electrode group (5); A plurality of small transformers are arranged to respectively control the DC voltage on each corona discharge cavity plate (1) and the corona discharge electrode (2); and sensors are arranged in the flow field to collect flow field data.

8. The turbulent friction drag reduction device based on array corona discharge according to any one of claims 1 to 5, characterized in that: The device works as follows: For a single corona discharge group, a high-voltage DC power supply (4) generates a DC high voltage, which is applied to the discharge electrode (2), generating a strong electric field between the discharge electrode (2) and the corona discharge cavity plate (1). The electric field intensity exceeds a critical value, causing air molecules to collide and ionize to produce a self-sustaining discharge, generating plasma (6), and forming an ion wind. The two oblique jets of each discharge group are coupled to form a spiral rising jet, generating a normal blowing effect in the flow field; A high-voltage DC power supply (4) is connected to ionize the air to generate plasma (6) to form an ion wind. The two oblique jets of each discharge group are coupled to form a spirally rising normal jet, which causes the bottom fluid of the boundary layer to wash upward and achieve turbulent friction drag reduction.

9. A turbulent friction drag reduction device and method based on array corona discharge, which is based on the turbulent friction drag reduction device based on array corona discharge according to any one of claims 1 to 5, characterized in that: The device works in the following three modes: Mode 1: When a high-voltage DC power supply (4) is connected, the corona discharge cavity plate (1) is the cathode, and the discharge electrode (2) is the anode, plasma (6) is generated between the corona discharge cavity plate (1) and the discharge electrode (2), forming a blowing effect, and plasma jets are generated from the two inclined holes in each group to couple to form a spiral rising normal vortex blowing; Mode 2: When a high-voltage sinusoidal power supply is connected, the corona discharge cavity plate (1) is the cathode, and the discharge electrode (2) is the anode, plasma (6) is generated between the corona discharge cavity plate (1) and the discharge electrode (2), forming a blowing effect. The plasma jets generated from the two inclined holes of each group are coupled to form a spiral rising normal vortex blowing. The blowing intensity of each group of electrodes changes sinusoidally with the voltage. Mode 3: When a high-voltage DC power supply (4) is connected, the corona discharge cavity plate (1) is the anode and the discharge electrode is the cathode, plasma (6) is generated between the corona discharge cavity plate (1) and the discharge electrode (2), forming an air suction effect; The method is specifically as follows: Step S1: The sensor collects flow field data. The sensor is placed in the flow field to collect information such as temperature, pressure, velocity, wall shear stress, etc. in the flow field in real time, and inputs the data into the controller; Step S2, the controller controls the circuit to select one of the three working modes, tries the three working modes in sequence and adjusts the voltage of each corona discharge group, the discharge density of the array corona discharge group and other parameters; Step S3, the sensor collects flow field data again to collect flow field information after corona discharge; In step S4, the controller analyzes the data collected by the sensor, compares the information before and after the corona discharge, and compares the changes in the friction resistance measured before and after the corona discharge under the temperature, pressure, and speed conditions. If the measured friction resistance is less than the friction resistance before the corona discharge, the expected drag reduction effect is achieved. Otherwise, the controller returns to step S2 and selects a new operating mode or a new discharge state based on the flow field information. The drag reduction effects of different modes are compared to select the optimal drag reduction mode. The selection method is as follows: when the aircraft is flying at high speed, the voltage needs to be increased, the density of the corona discharge group is increased, and a thicker air film is formed in the drag reduction arrangement area, which effectively reduces the viscous resistance between the air and the wall and meets the high-speed drag reduction requirement. When flying at low speed, a lower voltage is used and some corona discharge electrode groups are turned on to form an air film of a certain thickness in the drag reduction arrangement area, thereby meeting the drag reduction requirement and saving energy.

10. The turbulent friction drag reduction device and method based on array corona discharge according to claim 9, characterized in that: The surface friction resistance is measured using a surface shear stress sensor.

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