Plasma wall friction drag sensor of charge transport type

Abstract

The application provides a plasma wall friction drag sensor, which is in a sheet shape as a whole and comprises a high-voltage electrode (10), a grounding electrode (20), a charge collecting electrode (30) and an insulating base (60). The application also provides a plasma wall friction drag sensor system, which comprises the above-mentioned sensor, a high-voltage direct-current power supply (701), a current-limiting resistor (702), a first discharge resistor (703), a grounding terminal (801), a first voltage amplifier (802) and a first output terminal (803). Furthermore, the working process of the above-mentioned plasma wall friction drag sensor system is given. The application also extends the above-mentioned sensor and sensor system to form a double sensor, a multiple sensor and a sensor system. The application can solve the technical problem of how to measure the airflow wall friction drag at low cost, high frequency response and robustness.

Description

Technical Field

[0001] This invention relates to the field of turbulent friction resistance sensing, and in particular to a multi-electrode pulsed DC plasma wall friction resistance sensor based on charge transport effect. Background Technology

[0002] Increased lift and reduced drag are the eternal pursuits in the development of high-performance aircraft. According to their origin, aircraft drag can be divided into two parts: one is the drag caused by the pressure difference between the front and rear of the aircraft due to airflow separation, and the other is the drag caused by viscous friction when air flows over an object's surface (referred to as friction drag). Taking civil airliners and high-aspect-ratio UAVs as examples, the flow state on the aircraft surface during cruise is mostly turbulent, and turbulent friction drag accounts for nearly 50% of the total flight drag. Reducing friction drag, especially turbulent friction drag, is of great significance for improving the aircraft's range and flight time, and reducing engine fuel consumption. To conduct research on turbulent drag reduction, it is first necessary to use certain sensing devices to measure the airflow friction drag at different locations on the aircraft surface. Currently, there are two main types of measurement methods. One type measures friction drag based on the wall thermal film. The basic working principle is that "the higher the wall friction drag, the greater the velocity at the bottom of the boundary layer, the more heat the airflow carries away from the thermal film, and the higher the voltage required to maintain the same thermal film temperature." Another type of method calculates frictional resistance based on velocity profile measurements near the wall. This is based on Newton's law of viscosity, which states that the magnitude of frictional resistance is directly proportional to the slope of the airflow velocity profile near the wall and the gas dynamic viscosity. The former hot-film method requires complex signal conditioning and control circuitry to regulate the temperature of the hot film, resulting in high cost and low frequency response (on the order of 100 Hz). Furthermore, the calibration curve between voltage and wall frictional resistance is greatly affected by ambient temperature, making it environmentally sensitive. The latter method is only suitable for low-speed flows and has long measurement times and low efficiency. In high-speed flows (>100 m / s), with boundary layer thickness on the order of mm and wall viscosity on the order of μm, it is difficult to reliably obtain the velocity distribution of the bottom layer, whether using a hot-wire anemometer or a laser Doppler anemometer. CN1020130002682180 (“Gas Flow Measurement Device Based on AC Discharge Plasma Sensor”, Li Gang, Li Fang, Lin Feng, Zhu Junqiang, Nie Chaoqun, Xu Yanji) proposes a two-electrode sensor based on AC discharge plasma. This sensor determines the three flow states (laminar, transitional, and turbulent) of the gas based on the average value, root mean square (RMS), and skewness of the voltage waveforms of the two electrodes during the discharge process. However, because this plasma sensor senses airflow pulsation signals rather than airflow velocity signals, it cannot be used to measure frictional resistance near walls. Summary of the Invention

[0003] To address the problems existing in the prior art, this invention provides a "charge transport type plasma wall friction resistance sensor," hereinafter referred to as the "sensor." The sensor is generally sheet-shaped and includes a high-voltage electrode 10, a ground electrode 20, a charge collector electrode 30, and an insulating substrate 60. The insulating substrate 60 is a rectangular thin sheet. The high-voltage electrode 10, low-voltage electrode 20, and charge collector electrode 30 are fixed to the upper surface of the insulating substrate 60. The horizontally placed high-voltage electrode 10 has an axial cross-sectional shape resembling a pencil, with the tip pointing to the left. The tip is a sharp isosceles triangle, and the right side of the tip is a first elongated rectangle. The horizontally placed low-voltage electrode 20 is composed of a second elongated rectangle and a semi-circular head. The chord of the semi-circular head coincides with the short side of the second elongated rectangle. The semicircular arc is located at the right end of the low-voltage electrode 20, with the outer side of the semicircular arc facing the tip of the high-voltage electrode 10; the center line of the second long rectangular strip coincides with the center line of the high-voltage electrode 10, and this center line is parallel to the upper and lower sides of the insulating substrate 60, and closer to the upper side; the diameter of the right semicircular head is the same as the width of the long rectangular strip; a discharge gap is formed between the left tip of the high-voltage electrode 10 and the right semicircular head of the low-voltage electrode 20; the charge collector 30 is rectangular, and the length of the rectangle must be greater than the minimum gap between the high-voltage electrode 10 and the ground electrode 20; the axis of the charge collector 30 in the length direction is parallel to the upper and lower sides of the insulating substrate 60, and closer to the lower side; the minimum distance between the charge collector 30 and the high-voltage electrode 10 should be greater than twice the gas discharge gap.

[0004] In one embodiment of the present invention, the thickness of the insulating substrate 60 is determined by the electrical insulation performance of the selected material, and it is necessary to ensure that the breakdown voltage of the substrate material along the thickness direction is higher than twice the working voltage of the high voltage electrode 10; the length and width of the insulating substrate 60 are determined by the size parameters of the high voltage electrode 10 and the grounding electrode 20, and the minimum distance between the high voltage electrode 10 and the edge of the insulating substrate 60 should not be less than 5 mm.

[0005] In another embodiment of the present invention, the apex angle of the pen tip is 30-60 degrees; the width of the rectangle on the right side of the pen tip is 1-3 mm and the length is 10-15 mm.

[0006] In another embodiment of the present invention, the low-voltage electrode 20 has a width of 4-6 mm and a length of 10-15 mm.

[0007] In another embodiment of the present invention, the discharge gap distance between the left tip of the high voltage electrode 10 and the right semicircular head of the low voltage electrode 20 is 2-5 mm; the width of the charge collector electrode 30 is 3-5 mm.

[0008] A charge transport plasma wall friction resistance sensing system is also provided, which is based on the above-mentioned charge transport plasma wall friction resistance sensor, including the sensor of the present invention, a high-voltage DC power supply 701, a current-limiting resistor 702, a first discharge resistor 703, a ground terminal 801, a first voltage amplifier 802, and a first output terminal 803; wherein the high-voltage DC power supply 701, the current-limiting resistor 702, the high-voltage electrode 10, the low-voltage electrode 20, and the ground terminal 801 together constitute a corona discharge circuit; the positive terminal of the high-voltage DC power supply 701 is connected to the tail end of the high-voltage electrode 10 through the current-limiting resistor 702. The negative terminal of the high-voltage power supply is connected to the ground terminal 801; the tail end of the low-voltage electrode 20 is also connected to the ground terminal 801; the charge collector 30, the first unloading resistor 703, the first voltage amplifier 802, and the first output terminal 803 together constitute a signal acquisition and conditioning circuit; the lower end of the charge collector 30 is connected to the ground terminal 801 through the first unloading resistor 703; the positive terminal of the input signal of the first voltage amplifier 802 is connected to the lower end of the charge collector 30, and the negative terminal of the input signal is connected to the ground terminal 801; the signal amplified by the first voltage amplifier 802 is connected to a pair of output terminals 803.

[0009] In one embodiment of the present invention, the output voltage across the high-voltage DC power supply 701 is adjustable between 3-10kV, and the optimal voltage value is proportional to the gas gap between the high-voltage electrode 10 and the low-voltage electrode 20; the current-limiting resistor 702 has a value range between 1MΩ and 100MΩ, and its withstand voltage should be greater than 10kV; the first unloading resistor 703 has a resistance range between 100KΩ and 10MΩ, its withstand voltage should be greater than 500V, and its maximum power should not exceed 1W; the amplification factor of the first voltage amplifier 802 is adjustable from 1 to 100 to ensure that the output signal is within the range of 0-10V.

[0010] Furthermore, a charge transport plasma wall friction resistance sensing system is provided, based on the aforementioned plasma wall friction resistance sensing system, specifically as follows: With a gas gap of 3mm, when the high-voltage DC power supply 701 outputs a 3kV high voltage, due to the tip effect, the electric field concentrates at the left apex of the triangle on the high-voltage electrode 10. This electric field strength is much greater than the average electric field strength between the high-voltage electrode 10 and the low-voltage electrode 20. Therefore, the air at the tip of the high-voltage electrode 10 is ionized, forming free electrons, positive ions, and excited-state particles. These particles further induce ionization of air molecules in other areas through collisional ionization and photoionization, ultimately forming a diffuse filamentary corona plasma 40 between the high-voltage electrode 10 and the low-voltage electrode 20. The corona discharge plasma 40 contains a large number of electrons and positive ions. Electrons are lightweight and have high mobility; therefore, they can rapidly migrate from the low-voltage electrode 20 to the high-voltage electrode 20 under the influence of the electric field. A loop current is formed on the surface of the high-voltage electrode 10; however, the mass of positive ions is much greater than that of electrons, and they move slowly under the influence of the electric field, with a low mobility, and are easily affected by the external airflow and leave the plasma discharge region; affected by the normal airflow 501 near the wall, positive charges 401 are transported downstream and adsorbed on the surface of the charge collector 30; therefore, the potential of the charge collector 30 is higher than that of the ground terminal 801 and the negative electrode 20, and a voltage signal is formed between the two; the higher the speed of the normal airflow 501, the more positive charges 401 are transported from the corona plasma 40 to the downstream, and the higher the voltage on the charge collector 30; furthermore, according to Newton's law of viscosity, the airflow velocity near the wall is proportional to the airflow wall friction resistance, therefore, the voltage across the charge collector 30 is proportional to the airflow wall friction resistance. As long as this relationship is calibrated in advance, the wall friction resistance at any position in the airflow can be measured.

[0011] In addition, a dual-component plasma wall friction resistance sensor, hereinafter referred to as "dual-component sensor", is provided. It is based on the above-mentioned plasma wall friction resistance sensor. The dual-component sensor system is based on the plasma wall friction resistance sensor as described in any one of claims 1-5, with the addition of a charge collector electrode. The left charge collector electrode 301 and the right charge collector electrode 302 are identical and arranged side by side with their top edges aligned, leaving a gap between them. The center lines of the two charge collector electrodes 301 and 302 are aligned vertically with the center of the corona discharge plasma 40, and the vertical distance from the upper edge of the two charge collector electrodes 301 and 302 to the high-voltage electrode 10 is maintained at more than twice the gas discharge gap.

[0012] A dual-component plasma wall friction resistance sensing system, hereinafter referred to as the "dual-component sensor system," is also provided. Based on the aforementioned dual-component plasma wall friction resistance sensor, the left charge collector 301 and the right charge collector 302 are connected to the ground terminal 801 via a first unloading resistor 703 and a second unloading resistor 704, respectively. The resistance, power, and withstand voltage range of the second unloading resistor 704 are the same as those of the first unloading resistor 703. The lower end of the left charge collector 301 is connected to the lower end of the right charge collector 302 via two series-connected voltage divider capacitors 705 and 706. The capacitance values ​​of the voltage divider capacitors 705 and 706 are the same. This dual-component sensing system has two voltage dischargers, respectively... There are a first voltage discharger 802 and a second voltage discharger 804; the positive and negative input terminals of the first voltage amplifier 802 are connected to the lower ends of the left charge collector 301 and the right charge collector 302, respectively, and the amplified differential voltage signal is connected to the first pair of output terminals 803; the positive input terminal of the second voltage amplifier 804 is connected to the connection point of the two voltage dividing capacitors 705 and 706, the negative input terminal is connected to the ground terminal 801, and the amplified differential signal is connected to the second pair of output terminals 805; the tail end of the low voltage electrode 20 is connected to the ground terminal 801; the positive terminal of the high voltage DC power supply 701 is connected to the tail end of the high voltage electrode 10 through the current limiting resistor 702, and the negative terminal of the high voltage power supply is connected to the ground terminal 801.

[0013] Based on this, a dual-component plasma wall friction resistance sensor system is provided, which is based on the aforementioned dual-component plasma wall friction resistance sensing system, specifically as follows: Under the influence of the crosswind 502, the positive charges 401 inside the corona plasma 40 are transported downstream. The left half is adsorbed by the left charge collector 301, and the right half is adsorbed by the right charge collector 302. Since the crosswind 502 is deflected to the right, the number of positive charges collected by the right charge collector 302 is greater than that of the left charge collector 301, and there is a potential difference between them. This potential difference is amplified by the first voltage amplifier 802 and output to the first terminal 803. The magnitude of the output voltage is proportional to both the deflection angle of the crosswind 502 and the amplitude of the wall friction resistance, which can be approximated by the following formula:

[0014] U 803 =k0·f total sin(θ) (1)

[0015] Among them, U 803 This indicates the voltage at output terminal 803; θ represents the airflow deflection angle; f total This represents the magnitude of frictional resistance; k0 is the proportionality coefficient.

[0016] On the other hand, when the crosswind angle varies within a small range, the positive charge 401 transported downstream from the corona plasma 40 can always be adsorbed by either the left charge collector 301 or the right charge collector 302. Therefore, the average voltage of the two charge collectors 301 and 302 reflects the amplitude of the lateral airflow 502. The voltage amplified by the second amplifier 804 and output to the second terminal 805 is only proportional to the amplitude of the wall airflow velocity and is basically independent of the crosswind angle, as expressed by the following formula:

[0017] U 805 =k1·f total (2)

[0018] Among them, U 805 The voltage at the second output terminal 805 is represented by k1, which is the proportional coefficient. The amplitude of the wall friction resistance f under crosswind conditions is obtained by combining formulas (1) and (2). total And the airflow deflection angle θ; furthermore, the amplitude of the wall friction resistance can be decomposed along different directions to obtain two components:

[0019]

[0020] Among them, f x and f y These represent the horizontal frictional resistance component and the vertical frictional resistance component, respectively.

[0021] Furthermore, a plasma wall friction resistance sensor resistant to strong electromagnetic interference is provided, hereinafter referred to as "strong interference sensor". Based on the above-mentioned plasma wall friction resistance sensor, the strong interference sensing system adds a charge collector electrode to the plasma wall friction resistance sensor as described in any one of claims 1-5. The two charge collector electrodes 303 and 304 are placed symmetrically vertically and aligned on the left and right sides, with a gap between them. The center lines of the two charge collector electrodes 301 and 302 are aligned horizontally with the center of the corona discharge plasma 40. The vertical distance from the upper edge of the charge collector electrode 303 and the lower edge of the charge collector electrode 304 to the high voltage electrode 10 is maintained at more than twice the gas discharge gap. Looking along the direction of the normal airflow 501, the lower charge collector electrode 303 is downstream of the corona plasma 40, and the upper charge collector electrode 304 is upstream of the corona plasma 40.

[0022] Furthermore, a plasma wall friction resistance sensing system resistant to strong electromagnetic interference is provided, hereinafter referred to as the "strong interference sensing system". Based on the aforementioned strong interference plasma wall friction resistance sensor, the upper charge collector 303 and the lower charge collector 304 are connected to the ground terminal through a first unloading resistor 703 and a second unloading resistor 704, respectively. The resistance, power, and withstand voltage range of the second unloading resistor 704 are the same as those of the first unloading resistor 703. The tail end of the low-voltage electrode 20 is connected to the ground terminal 801. The positive terminal of the high-voltage DC power supply 701 is connected to the tail end of the high-voltage electrode 10 through a current-limiting resistor 702, and the negative terminal of the high-voltage power supply is connected to the ground terminal 801. The positive and negative input terminals of the first voltage amplifier 802 are connected to the lower charge collector 303 and the upper charge collector 304, respectively. The differential voltage signal amplified by the first voltage amplifier 802 is connected to the first output terminal 803.

[0023] Based on this, a working process of a plasma wall friction resistance sensing system resistant to strong electromagnetic interference is provided. Specifically, when the corona discharge operates in an unstable state or when there is strong electromagnetic interference in the environment, the voltage sensed on the lower charge collector 303 includes two parts: one part is the signal voltage formed by the adsorption of positive charges 401, and the other part is the noise voltage induced by electromagnetic interference. A reference charge collector, namely the upper charge collector 304, is set upstream of the corona discharge plasma 40 to measure the noise voltage induced by electromagnetic interference separately. Then, the noise voltage measured by the upper charge collector 304 is subtracted from the total voltage sensed on the lower charge collector 303 to obtain the pure signal voltage. This voltage is then amplified to obtain the first output terminal voltage 803, which is proportional to the amplitude of the wall friction resistance.

[0024] Furthermore, an array-type plasma wall friction resistance sensor is provided, which is based on the above-mentioned charge transport plasma wall friction resistance sensor, and linearly expands a single sensor to form a sensor array; the spacing, number of columns and rows of the sensors inside the array are all adjusted according to the actual flow.

[0025] Based on the charge transport effect, this invention proposes a multi-electrode pulsed DC plasma wall friction resistance sensor, which solves the technical problem of how to measure the wall friction resistance of airflow in a low-cost, high-frequency, and robust manner. Attached Figure Description

[0026] Figure 1 This illustrates the structure of a three-electrode surface DC corona plasma wall friction resistance sensor.

[0027] Figure 2The power supply circuit of the three-electrode DC corona plasma wall friction resistance sensor is shown.

[0028] Figure 3 This illustrates the power supply circuit for the improved A: dual-component four-electrode DC corona plasma wall friction resistance sensor;

[0029] Figure 4 This illustrates the power supply circuit for the improved B-type: anti-interference four-electrode DC corona plasma wall friction resistance sensor.

[0030] Figure 5 This illustrates an improved C: three-electrode DC corona plasma wall friction resistance sensor array.

[0031] Attached image annotations:

[0032] 10 High-voltage electrode 20 Grounding electrode 30 Charge collector 301 Left-side charge collector

[0033] 302 Right-side charge collector; 303 Lower-side charge collector; 304 Upper-side charge collector

[0034] 40 Plasma; 401 Positive Charge; 501 Normal Gas Flow; 502 Lateral Gas Flow; 503 Non-uniform Gas Flow

[0035] 60 Insulating substrate; 701 High voltage DC power supply; 702 Current limiting resistor; 703, 704 Unloading resistor.

[0036] 705, 706 voltage divider capacitors; 801 ground terminal; 802, 804 voltage amplifier; 803, 805 output terminals. Detailed Implementation

[0037] The present invention will now be described in conjunction with the accompanying drawings.

[0038] Figure 1 The basic structure of the invented plasma wall friction resistance sensor (hereinafter referred to as the "sensor") is shown. The sensor is generally sheet-shaped and consists of a high-voltage electrode 10, a ground electrode 20, a charge collector electrode 30, and an insulating substrate 60.

[0039] The insulating substrate material can be polyimide, polytetrafluoroethylene, nylon, glass fiber, ceramic, mica, etc., as long as it possesses good electrical properties and a certain degree of high-temperature resistance. When the sensor needs to operate continuously for extended periods, high-temperature resistant ceramic materials are preferred. The thickness of the insulating substrate 60 is determined by the electrical insulation performance of the selected material, ensuring that the breakdown voltage of the substrate material along its thickness direction is more than twice the operating voltage of the high-voltage electrode 10. Taking a 10kV operating voltage for the high-voltage electrode 10 as an example, the typical thickness of the ceramic substrate material is 1mm-2mm. The length and width of the insulating substrate 60 are determined by the dimensional parameters of the high-voltage electrode 10 and the grounding electrode 20. To prevent creepage and other phenomena, the minimum distance between the high-voltage electrode and the edge of the substrate should be no less than 5mm.

[0040] Three electrodes, made of copper, silver, or other metals with good conductivity, are electroplated onto an insulating substrate using processes such as screen printing, electrochemical deposition, or magnetron sputtering to form a very thin metallic coating. The coating thickness is uniform, typically 5 μm–50 μm. From the perspective of exciter lifespan, a thicker electrode coating provides better resistance to plasma corrosion. However, a thicker coating can disturb the flow near the wall during measurement, affecting measurement accuracy. As a compromise, a preferred electrode coating thickness is 20 μm.

[0041] The horizontally placed high-voltage electrode 10 has the axial cross-sectional shape of a pencil, with the tip pointing to the left. The tip (i.e., the left head) is a sharp isosceles triangle with a vertex angle ranging from 30 to 60 degrees (preferably 30 degrees). To the right of the tip is a first elongated rectangle with a width of 1-3 mm (preferably 2 mm) and a length of 10-15 mm (preferably 10 mm).

[0042] The horizontally placed low-voltage electrode 20 is composed of a second elongated rectangle and a semi-circular head. The chord (diameter) of the semi-circular head coincides with the short side of the second elongated rectangle. The semi-circular arc of the semi-circular head is located at the right end of the low-voltage electrode 20, and the outer side of the semi-circular arc faces the tip of the high-voltage electrode 10, forming a roughly "tit-for-tat" posture. The center line of the second elongated rectangle coincides with the center line of the high-voltage electrode 10. This center line is parallel to the upper and lower sides of the insulating substrate 60 and is closer to the upper side. The width of the low-voltage electrode 20 is 4-6 mm (preferably 5 mm), and the length is 10-15 mm (preferably 10 mm). The diameter of the right semi-circular head is the same as the width of the elongated rectangle.

[0043] A discharge gap is formed between the left tip of the high-voltage electrode 10 and the right semi-circular head of the low-voltage electrode 20, with a gap distance of 2-5 mm, preferably 3 mm. The charge collector 30 is rectangular and is used to receive the charge transported downstream by the gas flow; the length of the rectangle must be greater than the minimum gap between the high-voltage electrode 10 and the ground electrode 20, preferably 6 mm; the width of the rectangle is 3-5 mm (preferably 4 mm), and the axis of the charge collector 30 along its length is parallel to the upper and lower sides of the insulating substrate 60, and closer to the lower side. The minimum distance between the charge collector 30 and the high-voltage electrode 10 should be greater than twice the gas discharge gap.

[0044] Figure 2 The power supply circuit for the corona plasma wall friction resistance sensor includes the sensor of this invention, a high-voltage DC power supply 701, a current-limiting resistor 702, a first discharge resistor 703, a ground terminal 801, a first voltage amplifier 802, and a first output terminal 803. The high-voltage DC power supply 701, the current-limiting resistor 702, the high-voltage electrode 10, the low-voltage electrode 20, and the ground terminal 801 together constitute the corona discharge circuit. The positive terminal of the high-voltage DC power supply 701 is connected to the tail end of the high-voltage electrode 10 (i.e., the opposite end of the pen tip) through the current-limiting resistor 702, and the negative terminal of the high-voltage power supply is connected to the ground terminal 801. The tail end of the low-voltage electrode 20 (i.e., the opposite end of the semi-circular head) is also connected to the ground terminal 801. The output voltage across the high-voltage DC power supply 701 is adjustable between 3-10kV, and the optimal voltage value is proportional to the gas gap between the high-voltage electrode 10 and the low-voltage electrode 20. The current-limiting resistor 702 has a value range of 1MΩ-100MΩ, a withstand voltage greater than 10kV, and a maximum power determined by its resistance and the voltage across it (typically 10-100W). Its main function is to limit the discharge current and prevent corona discharge from developing into arc discharge. The charge collector 30, the first unloading resistor 703, the first voltage amplifier 802, and the first output terminal 803 together constitute the signal acquisition and conditioning circuit. The lower end of the charge collector 30 is connected to the ground terminal 801 through the first unloading resistor 703. The positive input signal terminal of the first voltage amplifier 802 is connected to the lower end of the charge collector 30, and the negative input signal terminal is connected to the ground terminal 801. The signal amplified by the first voltage amplifier 802 is connected to a pair of output terminals 803. The resistance value of the first unloading resistor 703 has a range of 100KΩ-10MΩ, a withstand voltage greater than 500V, and a maximum power not exceeding 1W. The first voltage amplifier 802 has an adjustable amplification factor of 1-100, ensuring that the output signal is within the range of 0-10V.

[0045] Working Principle: Taking a typical gas gap of 3mm as an example, when the high-voltage DC power supply 701 outputs a 3kV high voltage, due to the tip effect, the electric field will concentrate at the apex of the triangle on the left side of the high-voltage electrode 10. This electric field strength is much greater than the average electric field strength between the high-voltage electrode 10 and the low-voltage electrode 20. Therefore, the air at the tip of the high-voltage electrode 10 is ionized, forming free electrons, positive ions, and excited-state particles. These particles further induce ionization of air molecules in other areas through collisional ionization and photoionization, ultimately forming a diffuse filamentary corona plasma 40 between the high-voltage electrode 10 and the low-voltage electrode 20. The corona discharge plasma 40 contains a large number of electrons and positive ions. Electrons are lightweight and have high mobility; therefore, they can quickly migrate from the low-voltage electrode 20 to the surface of the high-voltage electrode 10 under the influence of the electric field, forming a loop current. However, positive ions are much heavier than electrons, move slowly under the influence of the electric field, have low mobility, and are easily affected by external airflow, causing them to leave the plasma discharge region. Figure 2 For example, influenced by the normal airflow 501 near the wall, positive charges 401 are transported downstream and adsorbed on the surface of the charge collector 30. Therefore, the potential of the charge collector 30 is higher than that of the ground terminal 801 and the negative electrode 20 (0V), forming a voltage signal between them. The higher the velocity of the normal airflow 501, the more positive charges 401 are transported downstream from the corona plasma 40, and the higher the voltage on the charge collector 30. Furthermore, according to Newton's law of viscosity, the airflow velocity near the wall is proportional to the frictional resistance of the airflow against the wall. Therefore, the voltage across the charge collector 30 is proportional to the frictional resistance of the airflow against the wall. Once this relationship is calibrated beforehand, the wall frictional resistance at any location in the airflow can be measured.

[0046] In turbulent flow, the airflow velocity and frictional resistance at the wall are constantly changing. If there is no discharge channel for the charge on the surface of the charge collector 30, the voltage on the charge collector 30 will remain at its maximum value and will not keep up with the changes in the external airflow velocity. The function of the first unloading resistor 703 is to provide a discharge channel for the charge, ensuring that the voltage on the charge collector 30 can reflect the instantaneous changes in turbulent frictional resistance in real time. In addition, due to the low ionization degree in the corona plasma 40 under atmospheric pressure, the voltage change on the surface of the charge collector 30 will be relatively weak (on the order of mV), which does not reach the input amplitude range (0-5V) of commonly used analog voltage signal acquisition systems. Therefore, the first voltage amplifier 802 is needed to amplify the signal before outputting it to the downstream data acquisition system. In addition to amplification, the first voltage amplifier 802 also isolates the signal input and output terminals; if an arc is accidentally generated between the high-voltage electrode 10 and the charge collector 30, the first voltage amplifier 802 can protect the downstream data acquisition system from damage caused by the arc discharge.

[0047] It is particularly important to emphasize that the sensor in this invention must operate in a low-power, low-current corona discharge mode. If the voltage across the high-voltage DC power supply 701 exceeds the threshold voltage, the discharge mode will change from corona discharge to arc discharge. Due to the intense heating effect of the arc, the insulating medium 60 may be burned, resulting in irreversible sensor damage.

[0048] Implementation Case (Improved Version A):

[0049] Figure 1-2 The existing sensor can only measure the wall friction resistance perpendicular to the gas discharge gap direction and is easily affected by external electromagnetic interference. The following section proposes improvements to the sensor to meet testing requirements in different situations. Figure 3 An improved power supply circuit for type A is presented, the purpose of which is to achieve separate measurement of the horizontal and vertical components of wall frictional resistance under lateral inflow 502. A dual-component sensor is provided, which... Figure 1-2 Based on this, an additional charge collector electrode is added, resulting in a total of four electrodes. The left charge collector electrode 301 and the right charge collector electrode 302 are identical and arranged side by side with their top edges aligned. The gap between adjacent electrodes is set to 0.5-2 mm, preferably 1 mm. The centerlines of the two charge collector electrodes 301 and 302 are vertically aligned with the center of the corona discharge plasma 40 (i.e., the center of the discharge channel formed by the ground electrode 20 and the high-voltage electrode 10). The vertical distance from the upper edge of the two charge collector electrodes 301 and 302 to the high-voltage electrode 10 is maintained at more than twice the gas discharge gap, as described above.

[0050] Figure 3The power supply circuit for the corona plasma wall friction resistance sensor is shown in the middle. The left charge collector 301 and the right charge collector 302 are connected to the ground terminal 801 through the first unloading resistor 703 and the second unloading resistor 704, respectively. The resistance, power, and withstand voltage range of the second unloading resistor 704 are the same as those of the first unloading resistor 703, and the specific values ​​have been explained above and will not be repeated here. The lower end of the left charge collector 301 is connected to the lower end of the right charge collector 302 through two series-connected voltage divider capacitors 705 and 706. The capacitance values ​​of the voltage divider capacitors 705 and 706 are the same, with a typical range of 1-10pF (preferably 5pF), and the withstand voltage of each is greater than 500V. This dual-component sensor has two voltage dischargers, namely the first voltage discharger 802 and the second voltage discharger 804, which are used to amplify the differential voltage and average voltage of the left charge collector 301 and the right charge collector 302, respectively. The positive and negative input terminals of the first voltage amplifier 802 are connected to the lower ends of the left and right charge collectors 301 and 302, respectively, and the amplified differential voltage signal is connected to the first pair of output terminals 803. The positive input terminal of the second voltage amplifier 804 is connected to the connection point of the two voltage divider capacitors 705 and 706, and the negative input terminal is connected to the ground terminal 801. The amplified differential signal is connected to the second pair of output terminals 805.

[0051] The working principle of the improved type A is as follows: Under the influence of the crosswind 502, the positive charges 401 inside the corona plasma 40 are transported downstream. The left half is adsorbed by the left charge collector 301, and the right half is adsorbed by the right charge collector 302. Because the crosswind 502 is deflected to the right, the number of positive charges collected by the right charge collector 302 is greater than that collected by the left charge collector 301, and there is a potential difference (i.e., voltage) between them. This potential difference is amplified by the first voltage amplifier 802 and output to the first terminal 803. The magnitude of the output voltage is proportional to the deflection angle of the crosswind 502 and the amplitude of the wall friction resistance, which can be approximately expressed by the following formula:

[0052] U 803 =k0·f total sin(θ) (1)

[0053] Among them, U 803 This indicates the voltage at output terminal 803; θ represents the airflow deflection angle; f total This represents the magnitude of frictional resistance; k0 is the proportionality coefficient, which can be obtained through calibration.

[0054] On the other hand, when the crosswind angle varies within a small range, the positive charge 401 transported downstream from the corona plasma 40 can always be adsorbed by either the left charge collector 301 or the right charge collector 302. Therefore, the average voltage of the two charge collectors 301 and 302 reflects the amplitude of the lateral airflow 502. The voltage amplified by the second amplifier 804 and output to the second terminal 805 is only proportional to the amplitude of the wall airflow velocity (i.e., the amplitude of the wall friction resistance) and is basically independent of the crosswind angle, as expressed by the following formula:

[0055] U 805 =k1·f total (2)

[0056] Among them, U 805 This represents the voltage at the second output terminal 805; k1 is the proportional coefficient, which can be obtained through calibration. The amplitude of the wall friction resistance f under crosswind conditions can be obtained by simultaneously solving formulas (1) and (2). total And the airflow deflection angle θ. Furthermore, the amplitude of this wall frictional resistance can be decomposed along different directions to obtain two components:

[0057]

[0058] Among them, f x and f y These represent the horizontal and vertical components of frictional resistance, respectively. It should be noted that "horizontal" and "vertical" are relative to the viewpoint. Figure 3 The horizontal direction is the centerline direction of the high-voltage electrode 10, and the vertical direction is the normal direction of the gas gap.

[0059] Implementation Case (Improved Version B):

[0060] exist Figure 2 In this system, the typical distance between the charge collector 30 and the high-voltage electrode 10 is only 6-10 mm. Therefore, when the corona discharge is unstable, it is easily affected by electromagnetic interference, inducing a high induced voltage on the charge collector 30 and reducing the signal-to-noise ratio of the measurement system. To solve this problem, it is possible to follow... Figure 4 The sensor was improved, and this improved version is similar to... Figure 3Both contain two charge collectors. However, they differ in that the two charge collectors 303 and 304 are placed symmetrically, one above the other. Viewed along the direction of the normal airflow 501, the lower charge collector 303 is downstream of the corona plasma 40, while the upper charge collector 304 is upstream of the corona plasma 40. The upper and lower charge collectors 303 and 304 are connected to the ground terminal through the first and second unloading resistors 703 and 704, respectively. The positive and negative input terminals of the first voltage amplifier 802 are connected to the lower and upper charge collectors 303 and 304, respectively, and the differential voltage signal amplified by the first voltage amplifier 802 is connected to the first output terminal 803.

[0061] The working principle of Improved Type B: When the corona discharge operates in an unstable state or when there is strong electromagnetic interference in the environment, the voltage sensed on the lower charge collector 303 consists of two parts: one part is the signal voltage formed by the adsorption of positive charges 401, and the other part is the noise voltage induced by electromagnetic interference. Directly amplifying the voltage on the lower charge collector 303 will also amplify the noise and cannot solve the problem of low signal-to-noise ratio of the sensor. Improved Type B sets a reference charge collector (i.e., the upper charge collector 304) upstream of the corona discharge plasma 40 to measure the noise voltage induced by electromagnetic interference separately. Then, by subtracting the noise voltage measured by the upper charge collector 304 from the total voltage sensed on the lower charge collector 303, a pure signal voltage can be obtained. This voltage is then amplified to obtain the first output terminal voltage 803, which is proportional to the amplitude of the wall friction resistance.

[0062] Implementation Case (Other Improvements):

[0063] Apart from Figure 3 , 4 In addition to the improved form described in the text, it is also possible to... Figure 2 A single wall friction resistance sensor is linearly extended to create a Figure 5 The sensor array (shown in the figure as three groups of individual wall friction resistance sensors) allows for adjustment of the spacing, number of columns, and number of rows of sensors within the array based on the actual flow. This adaptive design is well-known to those skilled in the art and will not be elaborated upon here. The advantage of this improved array is its ability to obtain the spatial distribution of wall friction resistance under non-uniform airflow 503, which is crucial for turbulence drag reduction research. Figure 5 The array design is based on a three-electrode corona discharge plasma triboelectric resistance sensor, but other types of sensors can also be used. Figure 3 The dual-component four-electrode corona discharge plasma triboelectric resistance sensor, or Figure 4 Anti-interference friction resistance sensor, or Figure 3 and Figure 4 A dual-component, anti-interference, five-electrode corona discharge plasma triboelectric resistance sensor is synthesized (the electrode arrangement consists of an upstream reference electrode to measure electromagnetic interference signals, two downstream electrodes to collect charge signals, and a high-voltage electrode and a grounding electrode to generate corona discharge). Any plasma sensing device based on the charge transport-type wall friction resistance measurement principle described in this invention falls within the scope of this invention.

[0064] Based on the above description of the working principle and structure, it is easy to see that the advantages of this invention are:

[0065] 1. Low cost: Compared with traditional hot film friction resistance sensors, this sensor has a simple power supply circuit and signal conditioning circuit, consisting of only a few resistors, capacitors and amplifiers, thus resulting in low cost.

[0066] 2. High-frequency response: Traditional hot-film measurement devices suffer from thermal inertia. When turbulent frictional resistance changes, the signal conditioning device needs a certain reaction time to maintain the temperature of the hot film after interference back to the set value, resulting in a typical measurement frequency of only 100Hz. This sensor, however, has no thermal inertia and operates in continuous mode, enabling high-speed measurement of real-time wall frictional resistance. Its frequency response is determined by the induced capacitance and unloading resistor value on the charge collector, and after optimization, it can easily reach frequencies above 10kHz.

[0067] 3. Good robustness: DC plasma corona is not sensitive to ambient temperature. When the ambient temperature changes within a small range (e.g., 300K±20K), the discharge state of the DC corona plasma is almost unaffected, thus there is no temperature drift, and its robustness is superior to that of hot-film friction resistance sensors. In addition, the invented improved sensor type B has good anti-electromagnetic interference capability.

[0068] 4. Wide range of applications: Compared with friction resistance measuring devices based on wall velocity profile measurement, the friction resistance sensor of the present invention has the advantages of a wide applicable speed range and high measurement efficiency.

[0069] 5. It also has the function of diagnosing gas flow state: The sensor proposed in invention patent CN1020130002682180 can only determine the gas flow state (laminar flow, transitional flow, turbulent flow), while the sensor in this invention can measure the real-time friction resistance amplitude and two components in the near-wall area. The gas flow state can be further determined from the amplitude and pulsation curve of the friction resistance, thus covering the scope of application of patent CN1020130002682180.

Claims

1. A charge transport type plasma wall friction resistance sensor, characterized in that, The sensor is sheet-like in shape, comprising a high-voltage electrode (10), a low-voltage electrode (20), a charge collector, and an insulating substrate (60); the insulating substrate (60) is a rectangular thin sheet; the high-voltage electrode (10), the low-voltage electrode (20), and the charge collector are fixed on the upper surface of the insulating substrate (60); the horizontally placed high-voltage electrode (10) has the shape of a pencil axial section, with the tip pointing to the left, the tip being a sharp isosceles triangle, and the right side of the tip being a first elongated rectangle; the horizontally placed low-voltage electrode (20) is composed of a second elongated rectangle and a semi-circular head, the chord of the semi-circular head coinciding with the short side of the second elongated rectangle, the semi-circular arc of the semi-circular head located at the right end of the low-voltage electrode (20), and the outer side of the semi-circular arc facing... The tip of the high-voltage electrode (10); the center line of the second long rectangular strip coincides with the center line of the high-voltage electrode (10), which is parallel to the upper and lower sides of the insulating substrate (60) and close to the upper side; the diameter of the right semi-circular head is the same as the width of the long rectangular strip; a discharge gap is formed between the left tip of the high-voltage electrode (10) and the right semi-circular head of the low-voltage electrode (20); the charge collector is rectangular, and the length of the rectangle is greater than the minimum gap between the high-voltage electrode (10) and the low-voltage electrode (20); the axis of the charge collector along its length is parallel to the upper and lower sides of the insulating substrate (60) and close to the lower side; the minimum distance between the charge collector and the high-voltage electrode (10) is greater than twice the gas discharge gap.

2. The plasma wall friction resistance sensor as described in claim 1, characterized in that, The thickness of the insulating substrate (60) is determined by the electrical insulation performance of the selected material, ensuring that the breakdown voltage of the substrate material along the thickness direction is higher than twice the working voltage of the high voltage electrode (10); the length and width of the insulating substrate (60) are determined by the size parameters of the high voltage electrode (10) and the low voltage electrode (20), and the minimum distance between the edge of the high voltage electrode (10) and the edge of the insulating substrate (60) is not less than 5 mm.

3. The plasma wall friction resistance sensor as described in claim 1, characterized in that, The apex angle of the pen tip is 30-60 degrees; the width of the rectangle on the right side of the pen tip is 1-3mm, and the length is 10-15mm.

4. The plasma wall friction resistance sensor as described in claim 1, characterized in that, The width of the low-voltage electrode (20) is 4-6 mm and the length is 10-15 mm.

5. The plasma wall friction resistance sensor as described in claim 1, characterized in that, The discharge gap distance between the left tip of the high voltage electrode (10) and the right semicircular head of the low voltage electrode (20) is 2-5 mm; the width of the charge collector electrode (30) is 3-5 mm.

6. A charge transport plasma wall friction resistance sensing system, based on the charge transport plasma wall friction resistance sensor as described in any one of claims 1-5, characterized in that, The system includes a sensor, a high-voltage DC power supply (701), a current-limiting resistor (702), a first discharge resistor (703), a ground terminal (801), a first voltage amplifier (802), and a first pair of output terminals (803); wherein the high-voltage DC power supply (701), the current-limiting resistor (702), the high-voltage electrode (10), the low-voltage electrode (20), and the ground terminal (801) together constitute a corona discharge circuit; the positive terminal of the high-voltage DC power supply (701) is connected to the tail end of the high-voltage electrode (10) through the current-limiting resistor (702), and the negative terminal of the high-voltage power supply is connected to the ground terminal (801); the low-voltage electrode (702) 20) The tail end is also connected to the ground terminal (801); the charge collector (30), the first unloading resistor (703), the first voltage amplifier (802) and the first pair of output terminals (803) together constitute the signal acquisition and conditioning circuit; the lower end of the charge collector (30) is connected to the ground terminal (801) through the first unloading resistor (703); the positive terminal of the input signal of the first voltage amplifier (802) is connected to the lower end of the charge collector (30), the negative terminal of the input signal is connected to the ground terminal (801), and the signal amplified by the first voltage amplifier (802) is connected to the first pair of output terminals (803).

7. The charge transport type plasma wall friction resistance sensing system as described in claim 6, characterized in that, The output voltage of the high voltage DC power supply (701) is adjustable between 3-10kV, and the optimal voltage value is proportional to the gas gap between the high voltage electrode (10) and the low voltage electrode (20); the current limiting resistor (702) has a value range of 1MΩ-100MΩ and a withstand voltage greater than 10kV; the first unloading resistor (703) has a resistance range of 100KΩ-10MΩ, a withstand voltage greater than 500V, and a maximum power of no more than 1W; the amplification factor of the first voltage amplifier (802) is adjustable from 1 to 100 to ensure that the output signal is in the range of 0-10V.

8. A measurement method for a charge transport-type plasma wall friction resistance sensing system, based on the plasma wall friction resistance sensing system as described in claim 6 or 7, characterized in that, Specifically, the gas gap is set to 3 mm. When the high voltage DC power supply (701) outputs a high voltage of 3 kV, due to the tip effect, the electric field will concentrate at the left triangle vertex of the high voltage electrode (10). The electric field strength is much greater than the average electric field strength between the high voltage electrode (10) and the low voltage electrode (20). Therefore, the air at the tip of the high voltage electrode (10) is ionized, forming free electrons, positive ions and excited state particles. These particles further induce the ionization of air molecules in other regions through collision ionization and photoionization, and finally form a diffuse filamentous corona plasma (40) between the high voltage electrode (10) and the low voltage electrode (20). The corona discharge plasma (40) contains a large number of electrons and positive ions. Electrons are light in mass and have high mobility. Therefore, they can quickly migrate from the low voltage electrode (20) to the surface of the high voltage electrode (10) under the action of the electric field to form a loop current. However, the mass of positive ions is much greater than that of electrons. They move slowly under the action of the electric field and have low mobility. They are easily affected by the external airflow and leave the plasma discharge area. Influenced by the normal airflow (501) near the wall, positive charges (401) are transported downstream and adsorbed on the surface of the charge collector (30). Therefore, the potential of the charge collector (30) is higher than that of the ground terminal (801) and the low-voltage electrode (20), forming a voltage signal between them. The higher the speed of the normal airflow (501), the more positive charges (401) are transported downstream from the corona plasma (40), and the higher the voltage on the charge collector (30). Furthermore, according to Newton's law of viscosity, the airflow speed near the wall is proportional to the frictional resistance of the airflow wall. Therefore, the voltage across the charge collector (30) is proportional to the frictional resistance of the airflow wall. This relationship is calibrated in advance, and the frictional resistance of the wall at any position in the airflow is measured.

9. A dual-component plasma wall friction resistance sensor, based on the plasma wall friction resistance sensor as described in any one of claims 1-5, characterized in that, The dual-component plasma wall friction resistance sensor is based on the plasma wall friction resistance sensor as described in any one of claims 1-5, with the addition of a charge collector electrode; the left and right charge collector electrodes are identical and arranged side by side with their top edges aligned, and a gap is left between them; the center lines of the two charge collector electrodes are aligned vertically with the center of the corona discharge plasma (40), and the vertical distance from the upper edge of the two charge collector electrodes to the high-voltage electrode (10) is maintained at more than twice the gas discharge gap.

10. A dual-component plasma wall friction resistance sensing system, based on the dual-component plasma wall friction resistance sensor as described in claim 9, characterized in that, The left charge collector (301) and the right charge collector (302) are connected to the ground terminal (801) through a first unloading resistor (703) and a second unloading resistor (704), respectively; the resistance, power, and withstand voltage range of the second unloading resistor (704) are the same as those of the first unloading resistor (703); the lower end of the left charge collector (301) is connected to the lower end of the right charge collector (302) through two series-connected voltage divider capacitors (705, 706); the capacitance values ​​of the voltage divider capacitors (705 and 706) are the same; this dual-component plasma wall friction resistance sensing system has two voltage amplifiers, namely a first voltage amplifier (802) and a second voltage amplifier (804); the first voltage amplifier... The positive and negative input terminals of the voltage amplifier (802) are connected to the lower ends of the left charge collector (301) and the right charge collector (302) respectively, and the amplified differential voltage signal is connected to the first pair of output terminals (803); the positive input terminal of the second voltage amplifier (804) is connected to the connection point of two voltage dividing capacitors (705 and 706), the negative input terminal is connected to the ground terminal (801), and the amplified differential signal is connected to the second pair of output terminals (805); the tail end of the low voltage electrode (20) is connected to the ground terminal (801); the positive terminal of the high voltage DC power supply (701) is connected to the tail end of the high voltage electrode (10) through the current limiting resistor (702), and the negative terminal of the high voltage power supply is connected to the ground terminal (801).

11. A measurement method for a dual-component plasma wall friction resistance sensor system, based on the dual-component plasma wall friction resistance sensing system as described in claim 10, characterized in that, Specifically, under the influence of the crosswind (502), the positive charges (401) inside the corona plasma (40) are transported downstream. The left half is adsorbed by the left charge collector, and the right half is adsorbed by the right charge collector. Since the crosswind (502) is deflected to the right, the number of positive charges collected by the right charge collector is greater than that of the left charge collector, and there is a potential difference between them. This potential difference is amplified by the first voltage amplifier (802) and output to the first pair of output terminals (803). The magnitude of the output voltage is proportional to the deflection angle of the crosswind (502) and the amplitude of the wall friction resistance, which can be approximated by the following formula: U 803 =k0·f total ·sin(θ) (1) Among them, U 803 The voltage across the first pair of output terminals (803) is represented by θ; the airflow deflection angle is represented by f. total This represents the magnitude of frictional resistance; k0 is the proportionality coefficient. On the other hand, when the crosswind angle varies within a small range, the positive charges (401) transported from the corona plasma (40) to the downstream can always be adsorbed by either the left or right charge collector. Therefore, the average voltage of the two charge collectors reflects the amplitude of the crosswind flow (502). The voltage amplified by the second voltage amplifier (804) and output to the second pair of output terminals (805) is only proportional to the amplitude of the wall airflow velocity and is basically independent of the crosswind angle. This can be expressed by the following formula: AT 805 =k1 f total (2) Among them, U 805 The voltage across the second pair of output terminals (805) is represented by k1, which is the proportionality coefficient. The amplitude of the wall friction resistance f under crosswind conditions is obtained by combining formulas (1) and (2). total And the airflow deflection angle θ; furthermore, the amplitude of the wall friction resistance can be decomposed along different directions to obtain two components: Among them, f x and f y These represent the horizontal frictional resistance component and the vertical frictional resistance component, respectively.

12. A plasma wall friction resistance sensor resistant to strong electromagnetic interference, based on the plasma wall friction resistance sensor as described in any one of claims 1-5, characterized in that, The anti-strong electromagnetic interference plasma wall friction resistance sensor is based on the plasma wall friction resistance sensor as described in any one of claims 1-5, with the addition of a charge collector electrode; the two charge collector electrodes are placed symmetrically on top of each other, aligned on the left and right sides, with a gap between them; the centerline of the two charge collector electrodes is aligned with the center of the corona discharge plasma (40) in the horizontal direction, and the vertical distance from the upper edge of the lower charge collector electrode and the lower edge of the upper charge collector electrode to the high voltage electrode (10) is maintained at more than twice the gas discharge gap; looking along the direction of the normal airflow (501), the lower charge collector electrode is downstream of the corona plasma (40), and the upper charge collector electrode is upstream of the corona plasma (40).

13. A plasma wall friction resistance sensing system resistant to strong electromagnetic interference, based on the plasma wall friction resistance sensor resistant to strong electromagnetic interference as described in claim 12, characterized in that, The upper charge collector and the lower charge collector are connected to the ground terminal through the first unloading resistor (703) and the second unloading resistor (704), respectively. The resistance, power and withstand voltage range of the second unloading resistor (704) are the same as those of the first unloading resistor (703). The tail end of the low voltage electrode (20) is connected to the ground terminal (801). The positive terminal of the high voltage DC power supply (701) is connected to the tail end of the high voltage electrode (10) through the current limiting resistor (702), and the negative terminal of the high voltage power supply is connected to the ground terminal (801). The positive and negative terminals of the input terminals of the first voltage amplifier (802) are connected to the lower charge collector and the upper charge collector, respectively. The differential voltage signal amplified by the first voltage amplifier (802) is connected to the first pair of output terminals (803).

14. A measurement method for a plasma wall friction resistance sensing system resistant to strong electromagnetic interference, based on the plasma wall friction resistance sensing system resistant to strong electromagnetic interference as described in claim 13, characterized in that, Specifically, when the corona discharge is in an unstable state or there is strong electromagnetic interference in the environment, the voltage sensed on the lower charge collector includes two parts: one part is the signal voltage formed by the adsorption of positive charges (401), and the other part is the noise voltage induced by the electromagnetic interference. A reference charge collector, namely the upper charge collector, is set upstream of the corona discharge plasma (40) to measure the noise voltage induced by the electromagnetic interference separately. Then, the noise voltage measured by the upper charge collector is subtracted from the total voltage sensed on the lower charge collector to obtain the pure signal voltage. The voltage is then amplified to obtain the voltage of the first pair of output terminals (803) that is proportional to the amplitude of the wall friction resistance.

15. An array-type plasma wall friction resistance sensor, based on the charge transport plasma wall friction resistance sensor as described in any one of claims 1-5, characterized in that, A single sensor is linearly expanded to form a sensor array; the spacing, number of columns, and number of rows of sensors within the array are all adjusted according to the actual flow.

Images