A protective device for high-speed wind tunnel dynamic airfoil plasma flow control test

Abstract

The invention discloses a protective device for a high-speed wind tunnel dynamic airfoil plasma flow control test, which is composed of an airfoil model, an exciter, an oscillation shaft, an insulating rotating window and a sensor; the lugs at both ends of the airfoil model are fastened to the oscillation shaft by bolts, and the side end of the oscillation shaft in the downstream direction is connected to the motor shaft to drive the airfoil model to oscillate in pitch. The oscillation shaft passes through the insulating rotating window, the upper and lower electrodes of the plasma exciter are connected to the high-voltage wire, and the positive and negative high-voltage wires are led out of the insulating rotating window through the high-voltage wire lead groove at the end of the oscillation shaft. The airfoil surface is covered with a high-voltage insulating tape to ensure the insulation of the airfoil surface when the plasma exciter is discharged; the contact surface of the oscillation shaft and the airfoil lug is pasted with a high-voltage-resistant insulating tape to ensure the insulation of the model from the side wall rotating window and the oscillation shaft; the sensor insulating bushing is used to effectively reduce the electromagnetic interference signal collected by the sensor to protect the test instrument; the protective device is suitable for high-speed wind tunnel dynamic tests.

Description

Technical Field

[0001] The present invention relates to the field of safety and protection of plasma flow control experimental technology in a high-speed wind tunnel, and in particular to a high-speed wind tunnel dynamic airfoil plasma flow control experimental protection device. Background Art

[0002] Dynamic stall is an unsteady flow separation phenomenon. Dynamic stall caused by high angle of attack will occur on the trailing blades of the rotor, and dynamic stall caused by shock wave induced front separation will also occur on the forward blades. Dynamic stall of helicopter rotors will lead to reduced lift, increased torque of the rotor shaft, increased power consumption, increased control load, and changes in the pitch torque of the blades causing vibration of the torque lever and flutter of the blades, reducing the performance of the helicopter. Therefore, improving dynamic stall performance is the key to increasing the forward flight speed of heavy-loaded rotor systems. In recent years, plasma flow control technology has become an emerging research direction of active flow control technology due to its advantages such as short response time, no moving parts, wide excitation frequency band, small thickness of the exciter and little effect on the aerodynamic performance of the airfoil. This technology has successfully achieved the goals of delayed separation, increased lift, and reduced drag in steady-state airfoil tests. Therefore, the use of plasma flow control for dynamic stall problems is of great engineering application value.

[0003] The research on the airfoil dynamic stall plasma flow control technology has gradually emerged in recent years. At present, the large-scale wind tunnel test research of this type is mainly aimed at low-speed flow with an incoming flow of less than 0.3Ma. Under low-speed flow conditions, due to the small aerodynamic force level of the airfoil, the requirement for structural strength is low. Therefore, the low-speed airfoil dynamic stall plasma flow control test generally uses an airfoil model made of insulating materials, so it is easy to achieve the discharge of the plasma exciter on the airfoil surface. Under high-speed incoming flow conditions, the aerodynamic force changes dramatically when the airfoil undergoes dynamic stall, and the structural strength requirements of the airfoil model are high. Traditional insulating materials cannot meet them. In addition, high-speed wind tunnels are generally all made of steel. When plasma discharges, it is necessary to apply a high voltage of tens of thousands of volts to the plasma exciter, which has a great impact on the test data acquisition equipment, the test model and the wind tunnel body. Therefore, how to achieve the insulation of the airfoil model, the wind tunnel body and the experimental instrument when the plasma exciter discharges has become a key issue in realizing the high-speed wind tunnel type dynamic stall plasma flow control test.

[0004] Chinese invention patent 201410108550.5 proposes a "support and protection device for high-speed wind tunnel plasma flow control experiments". This device solves the support and electromagnetic shielding of plasma flow control experiments in high-speed wind tunnels and effectively protects the test instruments; however, this device can only be used for steady-state tests and cannot be used for high-speed wind tunnel dynamic test devices. Summary of the invention

[0005] In order to avoid the deficiencies in the prior art, the present invention proposes a high-speed wind tunnel dynamic airfoil plasma flow control test protection device.

[0006] The technical solution adopted by the present invention to solve its technical problem is: including an upper electrode of an exciter, a lower electrode of an exciter, an airfoil model, an oscillation shaft, a positive high-voltage wire, a negative high-voltage wire, an insulating rotating window, a high-voltage wire lead groove, an upper electrode insulating layer, a lower electrode insulating layer and a sensor insulating bushing, characterized in that lugs are provided at both ends of the airfoil model, the lugs at both ends of the airfoil model are respectively matched with the middle cavity holes of the end face of the oscillation shaft and are tightened and fixed by bolts, the side end of the oscillation shaft in the downstream direction is connected to the motor output shaft through a coupling to drive the pitch oscillation of the airfoil model, the oscillation shaft passes through the insulating rotating window, and the gap between the oscillation shaft and the insulating rotating window is less than 0.8 mm, so as to ensure that the oscillation shaft will not rub against the insulating rotating window during high-frequency oscillation movement;

[0007] The distance between the upper electrode of the exciter and the lower electrode of the exciter is 1 mm along the chord length direction of the airfoil model. The upper electrode of the exciter and the lower electrode of the exciter are covered with polyimide insulating tape for insulation. The upper electrode of the exciter and the lower electrode of the exciter are respectively connected to the positive high-voltage wire and the negative high-voltage wire. The positive high-voltage wire and the negative high-voltage wire are respectively led out from the insulating rotating window through the high-voltage wire lead groove on the end of the oscillation shaft;

[0008] The lower electrode insulating layer is pasted on the surface of the airfoil model and is used for insulation between the lower electrode of the exciter and the airfoil model. The lower electrode of the exciter is pasted on the upper surface of the lower electrode insulating layer. The upper electrode insulating layer is pasted on the lower electrode insulating layer and above the lower electrode of the exciter and serves as a dielectric layer for plasma excitation. The upper electrode of the exciter is pasted on the upper electrode insulating layer. The sensor insulating bushing passes through the surface of the airfoil model and communicates with the model cavity. The sensor insulating bushing is used for installing a high-frequency dynamic sensor.

[0009] The upper electrode and the lower electrode of the actuator are 0.2mm thick copper foil insulating tape, and the width of the upper electrode and the lower electrode of the actuator are both 4mm.

[0010] The positive high-voltage wire and the negative high-voltage wire are used to transmit the excitation voltage in the plasma flow control experiment. The multi-layer shielded high-voltage wire is composed of a high-voltage resistant wire, a 75Ω baseband coaxial cable, an ordinary copper mesh, a plastic hose and a metal snake skin hose from the inside to the outside.

[0011] The insulating window structure is made of epoxy resin material; the insulating layer on the surface of the airfoil model is an insulating tape that can withstand high voltage, which completely covers the airfoil surface and the contact surface between the airfoil model and the supporting mechanism.

[0012] The sensor insulating bushing has an inner diameter of 2.33 mm, an outer diameter of 3.5 mm, and a length of 8 mm, and is used to fix the dynamic sensor and insulate it from the airfoil surface; the sensor wire shielding layer is 0.05 mm thick copper foil tape with embossing, which is used to shield the electromagnetic interference to the sensor wire during plasma discharge; the grounding copper foil is a wide copper foil band with a width of 10 cm and a thickness of 0.05 mm, which is used to introduce the induced voltage generated by the plasma discharge on the model into the ground.

[0013] Beneficial Effects

[0014] The invention proposes a high-speed wind tunnel dynamic airfoil plasma flow control test protection device, which is composed of an airfoil model, an exciter, an oscillation shaft, an insulating rotating window and a sensor; the lugs at both ends of the airfoil model are fastened to the oscillation shaft by bolts, and the side end of the oscillation shaft in the downstream direction is connected to the motor input shaft to drive the airfoil model to oscillate in pitch. The oscillation shaft passes through the insulating rotating window, the upper and lower electrodes of the plasma exciter are connected to the high-voltage wire, and the positive and negative high-voltage wires are led out of the insulating rotating window through the high-voltage wire lead groove at the end of the oscillation shaft. The airfoil surface is covered with high-voltage insulating tape to ensure the insulation of the airfoil surface when the plasma exciter is discharged; the insulating rotating window of epoxy resin material is used to achieve the insulation of the wind tunnel body; the insulating tape that can withstand high voltage is pasted on the contact surface of the oscillation shaft and the lug at the end of the airfoil, and the fixing screws are equipped with polytetrafluoroethylene bushings and gaskets to ensure the insulation between the airfoil model and the insulating rotating window and the oscillation shaft, as well as the insulation between the fixing screws and the lugs. The use of multi-layer shielded high-voltage wires makes the induced electromagnetic field attenuate layer by layer to meet the safety withstand voltage and electromagnetic shielding requirements of the measurement and control instruments; the copper foil broadband grounding greatly reduces the induced voltage caused by the electromagnetic field radiated by the transmission wire; the use of dynamic sensor bushings ensures the installation reliability of the sensor and also ensures the insulation between the sensor and the airfoil model; the use of sensor wire shielding layers can effectively reduce the electromagnetic interference signals collected by the sensor. The protective device ensures the insulation effect between the model and the tunnel body and protects the test instrument; the protective device is suitable for high-speed wind tunnel dynamic tests. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The following is a further detailed description of a high-speed wind tunnel dynamic airfoil plasma flow control test protection device of the present invention in conjunction with the accompanying drawings and implementation examples.

[0016] Figure 1 It is a schematic diagram of the protective device for the high-speed wind tunnel dynamic airfoil plasma flow control test of the present invention.

[0017] Figure 2 This is a schematic diagram of the installation of the test protection device model of the present invention.

[0018] Figure 3 Schematic diagram of the leading edge of the airfoil model.

[0019] Figure 4 Schematic diagram of the oscillation axis.

[0020] Figure 5 Schematic diagram of the sensor insulation bushing.

[0021] In the picture

[0022] 1. Upper electrode of exciter 2. Lower electrode of exciter 3. Airfoil model 4. Oscillation axis 5. Positive high-voltage wire 6. Negative high-voltage wire 7. Insulation window 8. High-voltage wire lead slot 9. Upper electrode insulation layer 10. Lower electrode insulation layer 11. Sensor insulation bushing DETAILED DESCRIPTION

[0023] The present embodiment is a high-speed wind tunnel dynamic airfoil plasma flow control test protection device.

[0024] See also Figure 1 to Figure 5 The high-speed wind tunnel dynamic airfoil plasma flow control test protection device of this embodiment is used in the dynamic experimental system of the NF-6 pressurized continuous high-speed wind tunnel. The NF-6 pressurized continuous high-speed wind tunnel and the dynamic test mechanism are all made of steel. When conducting plasma flow control experiments, the assembly and insulation of the wind tunnel body, model and its supporting mechanism must be considered to prevent high voltage from electromagnetic interference to measurement and control instruments and equipment.

[0025] The protective device for the dynamic airfoil plasma flow control test of the high-speed wind tunnel of this embodiment is composed of an exciter upper electrode 1, an exciter lower electrode 2, an airfoil model 3, an oscillation shaft 4, a positive high-voltage wire 5, a negative high-voltage wire 6, an insulating window 7, a high-voltage wire lead slot 8, an upper electrode insulation layer 9, a lower electrode insulation layer 10 and a sensor insulation bushing 11; wherein, lugs are provided at both ends of the airfoil model 3, and the lugs at the ends of the airfoil model 3 are respectively extended into the cavity of the oscillation shaft and fixed by bolts. The side end of the oscillation shaft 4 in the downstream direction is connected to the motor output shaft to drive the airfoil model 3 to oscillate in pitch. The oscillation shaft 4 passes through the insulating window 7, and the gap between the oscillation shaft 4 and the insulating window 7 is less than 0.8mm to ensure that the oscillation shaft will not scratch the insulating window during high-frequency oscillation movement. The exciter upper electrode 1 and the exciter lower electrode 2 are located on the airfoil model 3, and the distance along the chord length direction of the airfoil model 3 is 1mm. The exciter upper electrode 1 and the exciter lower electrode 2 are 0.2mm thick copper foil insulation tape, and the electrode width is 4mm; the exciter upper electrode 1 and the exciter lower electrode 2 are insulated by a layer of polyimide insulation tape. The exciter upper electrode 1 and the exciter lower electrode 2 are respectively connected to the positive high-voltage wire 5 and the negative high-voltage wire 6, and the positive high-voltage wire 5 and the negative high-voltage wire 6 are respectively led out from the insulation window 7 through the high-voltage wire lead groove 8 at the end of the oscillation shaft. The positive high-voltage wire 5 and the negative high-voltage wire 6 are used to transmit the excitation voltage in the plasma flow control experiment. The multi-layer shielded high-voltage wire is a high-voltage resistant wire, a 75Ω baseband coaxial cable, a common copper mesh, a plastic hose and a metal snake skin hose from the inside to the outside; the multi-layer shielded high-voltage wire is used to transmit the excitation voltage in the plasma flow control experiment. The lower electrode insulation layer 10 is pasted on the surface of the airfoil model for insulation between the exciter lower electrode 2 and the airfoil model 3, and the exciter lower electrode 2 is pasted on the lower electrode insulation layer 10. The upper electrode insulating layer 9 is attached to the lower electrode insulating layer 10 and the lower electrode 2 of the exciter, serving as a dielectric layer for plasma excitation. The upper electrode 1 of the exciter is attached to the upper electrode insulating layer 9. The sensor insulating bushing 11 passes through the airfoil surface, connecting the atmosphere and the cavity of the airfoil model 3, and is used to install a high-frequency dynamic sensor.

[0026] In this embodiment, the insulating window structure is made of epoxy resin material; the gap between the oscillation shaft 4 and the insulating window 7 is less than 0.8mm, ensuring that the oscillation shaft will not rub against the insulating window during high-frequency oscillation movement. In addition, the airtightness between the two must be ensured. If a large-scale air leakage occurs, it will affect the binary characteristics of the airfoil test and reduce the authenticity and reliability of the test data. The insulating layer on the airfoil surface is an insulating tape that can withstand high voltage, which completely covers the airfoil surface and the contact surface between the airfoil and the support mechanism.

[0027] In this embodiment, since the dynamic sensor is made of metal, it has extremely high requirements for the electromagnetic environment and needs to be insulated. The material of the sensor bushing is polytetrafluoroethylene, which can not only ensure its insulation from the airfoil model but also play the role of wrapping and tightening the sensor. The inner diameter of the dynamic sensor insulation bushing is 2.33mm, the outer diameter is 3.5mm, the length is 8mm, the inner diameter tolerance is -0.1mm, and the outer diameter tolerance is +0.1mm; after the sensor is installed, the bushing extending out of the airfoil surface needs to be flattened to ensure that it is flush with the airfoil surface. The sensor wire shielding layer is a 0.05mm thick embossed copper foil tape, which is used to shield the electromagnetic interference of the sensor wire during plasma discharge. The grounding copper foil broadband uses a 10cm wide and 0.05mm thick copper foil broadband, which is used to introduce the induced voltage generated by the plasma discharge on the model into the ground.

Claims

1. A high-speed wind tunnel dynamic airfoil plasma flow control test protection device, comprising an exciter upper electrode, an exciter lower electrode, an airfoil model, an oscillation shaft, a positive high-voltage wire, a negative high-voltage wire, an insulating window, a high-voltage wire lead slot, an upper electrode insulating layer, a lower electrode insulating layer and a sensor insulating bushing, characterized in that: Lugs are provided at both ends of the airfoil model, and the lugs at both ends of the airfoil model are respectively matched with the middle cavity holes on the end face of the oscillation shaft and are fixed by bolts. The side end of the oscillation shaft in the downstream direction is connected to the motor output shaft through a coupling to drive the airfoil model to oscillate in pitch. The oscillation shaft passes through the insulating rotating window, and the gap between the oscillation shaft and the insulating rotating window is less than 0.8 mm, so as to ensure that the oscillation shaft will not rub against the insulating rotating window during high-frequency oscillation movement. The distance between the upper electrode of the exciter and the lower electrode of the exciter is 1 mm along the chord length direction of the airfoil model. The upper electrode of the exciter and the lower electrode of the exciter are covered with polyimide insulating tape for insulation. The upper electrode of the exciter and the lower electrode of the exciter are respectively connected to the positive high-voltage wire and the negative high-voltage wire. The positive high-voltage wire and the negative high-voltage wire are respectively led out from the insulating rotating window through the high-voltage wire lead groove on the end of the oscillation shaft; The lower electrode insulating layer is pasted on the surface of the airfoil model and is used for insulation between the lower electrode of the actuator and the airfoil model. The lower electrode of the actuator is pasted on the upper surface of the lower electrode insulating layer. The upper electrode insulating layer is pasted on the lower electrode insulating layer and the lower electrode of the actuator and serves as a dielectric layer for plasma excitation. The upper electrode of the actuator is pasted on the upper electrode insulating layer. The sensor insulating bushing passes through the surface of the airfoil model and communicates with the model cavity. The sensor insulating bushing is used for installing a high-frequency dynamic sensor. The upper electrode and the lower electrode of the actuator are 0.2mm thick copper foil insulating tape, and the width of the upper electrode and the lower electrode of the actuator are both 4mm; The positive high-voltage wire and the negative high-voltage wire are used to transmit the excitation voltage in the plasma flow control experiment. The multi-layer shielded high-voltage wire is composed of a high-voltage resistant wire, a 75Ω baseband coaxial cable, an ordinary copper mesh, a plastic hose and a metal snake skin hose from the inside to the outside.

2. The high-speed wind tunnel dynamic airfoil plasma flow control test protection device according to claim 1 is characterized by: The insulating window structure is made of epoxy resin material; the insulating layer on the surface of the airfoil model is an insulating tape that can withstand high voltage, which completely covers the airfoil surface and the contact surface between the airfoil model and the supporting mechanism.

3. The high-speed wind tunnel dynamic airfoil plasma flow control test protection device according to claim 1, characterized in that: The sensor insulating bushing has an inner diameter of 2.33 mm, an outer diameter of 3.5 mm, and a length of 8 mm, and is used to fix the dynamic sensor and insulate it from the airfoil surface; the sensor wire shielding layer is an embossed copper foil tape with a thickness of 0.05 mm, which is used to shield the electromagnetic interference to the sensor wire during plasma discharge; the grounding copper foil adopts a copper foil wide band with a width of 10 cm and a thickness of 0.05 mm, which is used to introduce the induced voltage generated by the plasma discharge on the model into the ground.

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