Wind tunnel negative pressure working condition pressure sensor initial reading calibration device and method

Abstract

The invention discloses a wind tunnel negative pressure working condition pressure sensor initial reading calibration device and method. The device comprises a high-precision pressure controller, high-precision absolute pressure sensors with different measuring ranges, a vacuum pump, a gas buffer tank, a zero-leakage electromagnetic reversing valve, a matched sealing pipeline and the like. According to the invention, stable acquisition of 0.01%-level precision data can be realized, and important basic guarantee can be provided for accurate control of a wind tunnel flow field and accurate measurement of model aerodynamic parameters. On-line in-situ switching of a test pressure channel and a calibration pressure channel is achieved through switching control of the remote control electromagnetic valve, then the low-range pressure sensor initial reading on-site calibration method is achieved, the problem that initial reading on-site calibration of the low-range pressure sensor cannot be achieved in a conventional atmospheric pressure environment is solved, and the low-range pressure sensor initial reading on-site calibration method is suitable for large-scale popularization and application. The system deviation between the sensors is reduced, the deviation between the pressure truth value of the sensor and the measured pressure is also reduced, and the reliability of pressure measurement is improved.

Description

Technical Field

[0001] The invention belongs to the technical field of wind tunnel tests, and in particular relates to a device and method for high-precision calibration of initial readings of a pressure sensor under negative pressure conditions. Background Art

[0002] A wind tunnel is a pipe test device that measures the effect of fluid on an object and observes its physical phenomena. It generates an approximate real-condition airflow by driving the device under the unified scheduling of the wind tunnel operation and flow field control system, controls the precise movement of the model support mechanism, and then measures the aerodynamic characteristic parameters of the model under different postures, providing important guarantees for the prediction of aerodynamic characteristics of aircraft and the successful development of aircraft. The wind tunnel is an important equipment for aerodynamic experiments on aircraft shape design. It is one of the most commonly used and effective tools for aerodynamic experiments, and it plays a decisive role in aircraft development. The precise control of the wind tunnel flow field and the precise measurement of the model's aerodynamic parameters rely on high-precision pressure sensors to provide accurate data.

[0003] Mach number is the most important parameter to measure the level of wind tunnel flow field indicators. At subsonic speed, the total pressure and static pressure of the axial probe tube in the center of the test section (in order to facilitate flow field adjustment, the static pressure at a reference point on the side wall of the stationary chamber is usually used instead of the static pressure on the axial probe tube) are calculated according to the following isentropic formula Ma number: (Formula 1) in Ma is the Mach number; P 0 is the total pressure in the stable stage; P ct Static pressure in the room In the 1970s, NASA published a flow quality index based on the results of a questionnaire survey of wind tunnel customers, which was cited by the Air Force and the Navy. Ma The number accuracy requirement is single point Ma The numerical accuracy meets ±0.001.

[0004] Calculated by formula 1, the following is a set of calculation data: Table 1 Ma Deviation Requirements for Total Static Pressure Sensor Measurement Deviation

[0005] The calculation results in Table 1 show that to satisfy the single point Ma The number is better than ±0.001. As the total pressure decreases, the accuracy requirements for total pressure and static pressure are higher. When the total pressure is 10kPa, the static pressure deviation is better than ±0.006kPa. Ma The numerical deviation is ±0.00106.

[0006] Since the accuracy of the sensor is x%FS (full scale), when x% is the same, the actual measurement accuracy of pressure sensors with different ranges is also different. Generally, the larger the range of the same type of sensor, the larger the corresponding absolute error. Therefore, in order to meet the needs of different test conditions and improve the pressure control and measurement accuracy, wind tunnels usually configure pressure sensors with high, medium and low levels according to different ranges. In the test, the best range pressure sensor is matched according to the different operating pressures of the wind tunnel.

[0007] Due to the existence of system deviation, the output values ​​of multiple groups and multiple pressure sensors participating in the wind tunnel test under the same ambient pressure are different. In order to eliminate the differences between sensors, the method of collecting initial readings of multiple pressure sensors participating in the test at the same time is usually used for on-site calibration during the wind tunnel test to eliminate the system deviation between equipment. The specific method is as follows: (1) Before the test, in an atmospheric pressure environment, using the atmospheric pressure value as a reference, obtain the deviation between the feedback value of each sensor and the atmospheric pressure sensor. That is, ΔPx=Psnrx / t0-Pa, Then Px / t0 = Psnrx / t0-ΔPx= Pa; (2) The pressure value of the measuring point at a certain moment in the future is the difference between the corresponding sensor feedback value and the deviation value: Px / tn = Psnrx / tn-ΔPx Where ΔPx is the deviation between the feedback value of a sensor x and the atmospheric pressure sensor at the time of initial reading (t0), Psnrx / t0 and Psnrx / tn are the feedback values ​​of sensor x at t0 and tn, Px / t0 and Px / tn are the true values ​​of sensor x obtained by the acquisition system at t0 and tn after deducting the system deviation ΔPx. This true value is also the value used for flow field control and model aerodynamic parameter measurement. Pa is the pressure value fed back by the atmospheric pressure sensor.

[0008] The above method is feasible for pressure sensors with a range exceeding atmospheric pressure or that can obtain effective feedback data under atmospheric pressure environment. However, for wind tunnels with negative pressure test conditions, the low-range pressure sensors (sensors with a range lower than atmospheric pressure, commonly known as negative pressure sensors, the present invention specifically refers to small-range absolute pressure sensors that cannot obtain correct readings under atmospheric pressure environment) that the wind tunnel needs to use have atmospheric pressure exceeding their measurement range. Therefore, it is impossible to take initial readings for on-site calibration under atmospheric environment, and it is also impossible to determine the deviation of this sensor from the true value, which introduces uncertain deviations into the accurate measurement and control of negative pressure conditions. The above-mentioned problems are also the problems that the present invention aims to solve. Summary of the invention

[0009] In order to overcome the above-mentioned shortcomings of the prior art, the present invention proposes a device and method for calibrating the initial readings of a pressure sensor under negative pressure conditions in a wind tunnel, which solves the problems of inaccurate key pressure data collection, large system errors, and inability to calibrate the initial readings of high-precision negative pressure sensors during the implementation of existing wind tunnel negative pressure conditions tests.

[0010] The technical solution adopted by the present invention to solve the technical problem is: a device for calibrating the initial reading of a pressure sensor under negative pressure conditions in a wind tunnel, comprising a high-precision pressure controller, a three-way solenoid valve for switching the gas path, a PLC controller and a program-controlled computer, wherein: The low-pressure gas source interface of the high-precision pressure controller is connected to the first stop ball valve and the vacuum pump in sequence; The high-pressure gas source interface of the high-precision pressure controller is connected to the adjustable pressure reducing valve, the fourth stop ball valve and the high-pressure nitrogen bottle in sequence; The standard pressure output end of the high-precision pressure controller is connected to the first buffer tank, the second stop ball valve and the R end of the third gas circuit switching three-way solenoid valve in sequence to form a calibration channel No. 1; the P end of the third gas circuit switching three-way solenoid valve is connected to the second buffer tank and the wind tunnel chamber in sequence to form a test channel No. 2; the A end of the third gas circuit switching three-way solenoid valve is connected to the P end of the first gas circuit switching three-way solenoid valve, the P end of the second gas circuit switching three-way solenoid valve and the high-range pressure sensor, respectively, and the A ends of the first gas circuit switching three-way solenoid valve and the second gas circuit switching three-way solenoid valve are connected to the low-range pressure sensor and the mid-range pressure sensor, respectively; The program-controlled interface end of the high-precision pressure controller is connected to the program-controlled computer and the PLC controller through a network switch; the PLC controller is connected to the first, second and third gas path switching three-way solenoid valves and low, medium and high range pressure sensors respectively.

[0011] The present invention also provides a method for calibrating the initial reading of a pressure sensor under negative pressure conditions in a wind tunnel, comprising the following steps: Step 1: Turn on the high-precision pressure controller and preheat for half an hour; Step 2: Perform air tightness test on the device and turn on the power of the vacuum pump after the leakage meets the requirement; Step 3: Before taking the initial reading, open the first and second gas path switching three-way solenoid valves, connect the low-range pressure sensor, the mid-range pressure sensor and the measuring gas path, and the high-range pressure sensor is always in the measuring state; Step 4: Control the third gas circuit to switch the three-way solenoid valve to the R end to connect the calibration pressure gas circuit; Step 5: The output pressure of the high-precision pressure controller is used as the calibration pressure Pcal, and the pressure setting value is 60% of the full scale of the low-range pressure sensor; Step 6: When the calibration pressure reaches a steady state, start the initial reading calibration procedure; Step 7: The high-precision pressure controller returns to normal pressure; Step 8: Control the third gas circuit to switch the three-way solenoid valve to the P end, connect the test pressure gas circuit, and wait for the test; Step 9. After the test starts, the wind tunnel control system uses the true pressure values ​​of the mid-range pressure sensor and the high-range pressure sensor as reference to control the wind tunnel pressure to gradually approach the target pressure in the negative pressure direction. When the test pressure enters the working pressure range of the low-range pressure sensor, it switches to closed-loop control of the wind tunnel pressure using the true pressure value of the low-range pressure sensor as reference. The measurement system collects the true pressure value of the low-range pressure sensor for calculation of the wind tunnel flow field and model aerodynamic characteristic parameters.

[0012] Compared with the prior art, the present invention has the following positive effects: The high-precision calibration device for the initial reading of the pressure sensor of the wind tunnel negative pressure working condition of the present invention comprises a high-precision pressure controller (calibrator), high-precision absolute pressure sensors of different ranges, a vacuum pump group, a gas buffer tank, a zero-leakage electromagnetic reversing valve, and a matching sealing pipeline. The vacuum pump group generates an initial negative pressure environment for the pressure controller (calibrator). After the high-precision pressure controller (calibrator) stabilizes the output, it is used to generate a 0.005% high-precision initial reference pressure reference point for all sensors and wind tunnel measurement, control and other systems. The gas buffer tank is located between the output end of the pressure controller (calibrator) and the high-precision pressure sensor to buffer and stabilize the high-precision reference pressure reference point output by the pressure controller (calibrator). High-precision absolute pressure sensors of different ranges are used for pressure data collection and monitoring during the test process. The zero-leakage electromagnetic reversing valve controls the on and off of different gas paths to realize the calibration and accuracy verification of sensors of different ranges. The present invention can realize the stable collection of 0.01%-level accuracy data, and can provide an important basic guarantee for the precise control of the wind tunnel flow field and the precise measurement of the model aerodynamic parameters. The present invention realizes the online in-situ switching of the test pressure and calibration pressure channels through remote control of the electromagnetic valve switching control, and then realizes the on-site calibration method of the initial reading of the low-range pressure sensor, which solves the problem that the initial reading of the low-range pressure sensor cannot be calibrated on-site under the conventional atmospheric pressure environment; the on-site calibration method using the stable pressure output by the high-precision pressure controller as the reference pressure reduces the system deviation between sensors, and also reduces the deviation between the true value of the sensor pressure and the measured pressure, and improves the reliability of pressure measurement, thereby providing an important basic guarantee for the precise control of the wind tunnel flow field and the precise measurement of the model aerodynamic parameters. The specific advantages of the present invention include: (1) Multiple pressure sensors can be calibrated and tested for accuracy online simultaneously or individually. The No. 1 calibration channel output by the independent pressure controller (calibrator) and the No. 2 test pressure output channel in the wind tunnel chamber can be connected to the pressure sensors of the corresponding ranges by remotely controlling the electromagnetic reversing valves, so that online in-situ calibration, calibration and test measurement can be realized by program control without changing the hardware layout. A pressure stabilizing chamber (i.e., the first buffer tank) is provided at the output end of the pressure controller (calibrator) of the No. 1 calibration channel to ensure the stability and reliability of the pressure value in the gas circuit at the detection end of the pressure sensor to be calibrated, so as to avoid abnormal fluctuations affecting the measurement accuracy. Before the wind tunnel test is started and pressurized, the No. 1 calibration channel is responsible for measuring the standard pressure reference point. When the indications of each pressure sensor are stable and the initial readings are collected and saved, the No. 2 test pressure measurement channel is switched to measure the feedback value of the wind tunnel chamber test pressure. (2) In addition to the core high-precision pressure calibration function, the device of the present invention has reserved a flexible interface. By opening or closing the third stop ball valve, it can be easily expanded to connect other pipelines or equipment, such as connecting to a digital display for air tightness and air permeability detection, expanding sensors to be calibrated, connecting portable handheld pressurizing equipment, etc. The reserved spare interface is a replaceable self-locking sleeve interface, which is convenient for fast and flexible connection of external devices with different pipe diameters and specifications. It can easily perform online air tightness and leakage rate detection and evaluation of the entire device system, so as to assist in device self-inspection, troubleshooting, etc., to ensure the reliable operation of the equipment and the final calibration accuracy; (3) The present invention can remotely implement all operations in the centralized control room, including arbitrarily setting the calibration pressure point, arbitrarily setting the verification pressure point, remotely and automatically calculating the calibration coefficient, and remotely switching the calibration and verification working conditions and the test measurement working conditions; (4) During the initial reading calibration phase before the start of the wind tunnel test, when the pressure feedback value measured by the No. 1 measurement channel output by the pressure controller (calibrator) does not reach within ±1 kPa of the given value, the No. 1 measurement channel is responsible for calibrating the pressure measurement value feedback, and the No. 2 measurement channel is used as the monitoring channel. At this time, the system has a built-in stability protection function to prevent the calibration procedure from being triggered by mistake when the calibration pressure value does not reach the required accuracy range; (5) After the wind tunnel test is started, the entire calibration device of the present invention can be placed in a power-off offline state, and the No. 1 measurement channel output of the pressure controller (calibrator) can be independently connected to other gas circuits and sensors for other operations, without affecting the normal test measurement of other sensor channels after calibration; (6) In addition to being used for calibrating the initial readings of pressure sensors under negative pressure conditions in wind tunnels, the present invention can also be used to perform online testing of the stability and accuracy of test sensors, re-calibrate calibration coefficients, and assist in determining whether the test sensors are usable or need to be replaced. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 It is a schematic diagram of the structure of the calibration device, in which the thick solid line is the gas path and the dotted line is the circuit; Figure 2 It is a flow chart of the implementation of the calibration process; Figure 3 It is the test measurement curve of the first two 50kPa range sensors before calibration; Figure 4 It is the test measurement curve of two 50kPa range sensors after calibration. DETAILED DESCRIPTION

[0014] A device for calibrating the initial reading of a pressure sensor under negative pressure in a wind tunnel, such as Figure 1 As shown, it includes: vacuum pump 1, first to fourth stop ball valves 21 to 24, first to third gas filters 31 to 33, high-precision pressure controller 4, first and second buffer tanks 51 and 52, first to fourth electric contact pressure gauges 61 to 64, first to third gas path switching three-way solenoid valves 71 to 73, low, medium and high range pressure sensors 81 to 83 to be calibrated, program-controlled computer 9, on-site PLC controller 10, network switch 11, reserved spare interface 12, high-pressure nitrogen cylinder 13, adjustable pressure reducing valve 14, wind tunnel chamber 15, etc. Among them: The vacuum pump 1, the first to the cut-off ball valve 21, and the first gas filter 31 are connected to the low-pressure gas source interface of the high-precision pressure controller 4 in sequence; the standard pressure output end of the high-precision pressure controller 4, the first buffer tank 51, and the second cut-off ball valve 22 are connected to the R end (No. 1 calibration channel) of the third gas path switching three-way solenoid valve 73, and the first to the electric contact pressure gauge 61 and the third cut-off ball valve 23 are arranged on the pipeline between the second cut-off ball valve 22 and the R end of the third gas path switching three-way solenoid valve 73, and a reserved spare interface 12 is arranged at the third cut-off ball valve 23; the wind tunnel chamber 15, the second gas filter 32, and the second buffer tank 52 are connected to the P end (No. 2 test channel) of the third gas path switching three-way solenoid valve 73 in sequence, and the second electric contact pressure gauge 62 is arranged between the second buffer tank 52 and the P end of the third gas path switching three-way solenoid valve 73; the size and structure of the No. 1 calibration channel and the No. 2 test measurement channel are exactly the same; the high-pressure nitrogen bottle 13, the fourth cut-off ball valve 24, and the adjustable pressure reducing valve 14 are connected to the high The high-pressure gas source interface of the high-precision pressure controller 4 is provided with a third electric contact pressure gauge 63 between the high-pressure nitrogen bottle 13 and the fourth stop ball valve 24, and a fourth electric contact pressure gauge 64 is provided between the adjustable pressure reducing valve 14 and the high-pressure gas source interface of the high-precision pressure controller 4; the program-controlled interface end of the high-precision pressure controller 4 is connected to the network switch 11; the A end of the third gas path switching three-way solenoid valve 73 is connected to the third gas filter 33, and the third gas filter 33 is respectively connected to the P end of the first gas path switching three-way solenoid valve 71, the P end of the second gas path switching three-way solenoid valve 72, and the high-range pressure sensor 83, and the A end of the first gas path switching three-way solenoid valve 71 and the second gas path switching three-way solenoid valve 72 are respectively connected to the low-range pressure sensor 81 and the medium-range pressure sensor 82; the program-controlled computer 9, the network switch 11, and the on-site PLC controller 10 are connected in sequence, and the on-site PLC controller 10 is respectively connected to the first, second, and third gas path switching three-way solenoid valves and the low, medium, and high range pressure sensors.

[0015] The vacuum pump 1 is an oil-sealed rotary vane vacuum pump, which is used to provide a high-pressure controller 4 with a high-vacuum gas source environment with a high pumping rate and a high vacuum degree; the stop ball valve is a plate-mounted manual stop ball valve, which is used to cut off local components or mechanisms in the gas path during device maintenance and overhaul, or in emergency situations such as overpressure, abnormal equipment status and loss of control, so as to facilitate local disassembly and maintenance and ensure the safety of the internal equipment of the device; the gas filter is used to filter dust, debris and other sundry particles in the gas path of the device to ensure the cleanliness of the working air medium required by the precision components in the device; the vacuum pump 1, the stop ball valve, the gas filter and the high-precision pressure controller 4 The G3 / 8 type hard stainless steel pressure pipeline is used for connection, and the interface is sealed with glue; the buffer tank is a stainless steel air pressure buffer tank, which is used to ensure the stability and reliability of the pressure value in the gas circuit at the detection end of the pressure sensor to be calibrated, avoid the influence of abnormal fluctuations on the measurement accuracy, and ensure the accuracy of data acquisition; the electric contact pressure gauge 6 is an electric contact pointer gas pressure gauge, which is used to conveniently and intuitively monitor the wind tunnel test site, and is connected to the pressure values ​​of various gas circuits in the calibration device of the present invention to ensure that there is no pressure build-up or overpressure in various parts of the system, which damages the pipeline or equipment; the gas circuit switching three-way solenoid valve 7 is a zero-leakage three-way solenoid reversing valve, which is used to select Select and switch the gas path connected to the measuring end of the sensor to be calibrated; through the solenoid valve switching, each sensor 8 to be calibrated can be calibrated at the same time or individually; the gas path switching three-way solenoid valve 7 and the sensor to be calibrated 8 are connected through a standard 12mm outer diameter hose; the program-controlled computer 9 is a remote control computer, which is used to send control instructions such as controlling the on-off of the solenoid valve and outputting the calibration target pressure value to the pressure controller through the program in the remote operation room to the on-site PLC, and monitor the state parameters of the pressure controller and the measured value of the pressure sensor to be calibrated; the on-site PLC controller 10 is a on-site PLC programmable logic controller The controller is used to control the on-off of equipment such as on-site solenoid valves; the network switch 11 is used for local area network access and interconnection of equipment such as program-controlled computers, on-site control PLCs, and pressure controllers; the reserved spare interface 12 is a reserved card sleeve interface for use in leak detection or other expansion of an external digital pressure gauge; the high-pressure nitrogen cylinder 13 is used to add positive pressure to the pressure controller, and to use the gas source for the air permeability and air tightness detection of the entire system pipeline of the device described in the present invention; the adjustable pressure reducing valve 14 is an adjustable pressure reducing valve, which is used to reduce the high pressure output by the high-pressure nitrogen cylinder 13 and then input it into the high-precision pressure controller 4 for use.

[0016] like Figure 2 As shown, a method for calibrating the initial reading of a pressure sensor under negative pressure conditions in a wind tunnel comprises the following steps: 1. According to Figure 1 The diagram shows the connections for the various parts of the calibration device.

[0017] 2. Turn on the high-precision pressure controller 4 and preheat it for half an hour; 3. Air tightness test of the device: open the outlet valve of the high-pressure nitrogen bottle 13, and reduce the air pressure at the rear end of the pressure reducing valve to 300kPa-400kPa by adjusting the pressure reducing valve 14. At the same time, close the first stop valve 21 at the outlet end of the vacuum pump 1, and switch all the low-range sensor air circuits to be calibrated in the device air circuit to the closed state; connect the digital display monitoring pressure to the reserved spare interface 12, and open the third stop valve 23 at the reserved spare interface 12 at the same time. In addition, all other stop valves in the device are opened to ensure that all air circuits of the device are unobstructed. Set the pressure controller 4 so that the output pressure at its standard pressure output end is 300kPa, observe the indication of the first digital pressure gauge 61 connected to the reserved spare interface 12 for 2 minutes, and record it every 30 seconds. Finally, calculate the recorded data to obtain the gas leakage of the entire device connecting the air circuit. After the leakage meets the requirements, continue with the following operations; 4. Turn on the power of vacuum pump 1; 5. Before taking the initial reading, open the first solenoid valve 71 and the second solenoid valve 72, connect the low-range pressure sensor 81, the middle-range pressure sensor 82 and the measuring gas path, and the high-range pressure sensor 83 is always in the measuring state; 6. Control the third solenoid valve 73 to the R end to connect the calibration pressure gas circuit; 7. The output pressure of the high-precision digital pressure controller 4 is used as the calibration pressure. The pressure setting value is 60% of the full scale of the low-range pressure sensor. For example, if the full scale of the low-range pressure sensor is 50 kPa, the calibration pressure point Pcal is set to 50×60%=30.00 kPa; 8. Confirm that the output pressure of the pressure controller 4 reaches the target pressure and is stable, confirm that the pressure values ​​collected by each pressure sensor are stable, and collect the initial readings, ΔPx=Psnrx / t0-Pcal; 9. The pressure controller 4 returns to normal pressure; 10. Control the third solenoid valve 73 to the P end, connect the test pressure gas circuit, and wait for the test; 11. After the test starts, the wind tunnel control system uses the true pressure values ​​of the mid-range pressure sensor 82 and the high-range pressure sensor 83 as reference to control the wind tunnel pressure to gradually approach the target pressure in the negative pressure direction. When the test pressure enters the working pressure range of the low-range pressure sensor 81, it switches to the wind tunnel pressure closed-loop control with the true pressure value of the low-range pressure sensor (Px / tn = Psnrx / tn-ΔPx) as reference. The measurement system collects the true pressure value of the low-range pressure sensor for calculation of the wind tunnel flow field and the aerodynamic characteristic parameters of the model.

[0018] The comparison results of the measurement data before and after calibration of a sensor with a measuring range of 50 kPa obtained in a wind tunnel test using the present invention are shown in Table 2 below.

[0019] Table 2 Comparison of test results of 50kPa pressure sensor before and after calibration

[0020] It can be seen from Table 2 that the deviation mean and variance indicators of the test pressure data of the sensor calibrated by the device described in the present invention are better than those of the uncalibrated sensor, and the maximum error of the pressure value measured by the sensor calibrated by the device and method described in the present invention is lower than the ±0.03 kPa described in Table 1, thereby ensuring that the Ma number deviation required for the final wind tunnel test reaches the required ±0.001.

[0021] Figure 3 and Figure 4 The following is a graph of the pressure values ​​obtained by testing two 50kPa range sensors before and after calibration, corresponding to Table 2. Figure 3 and Figure 4 It can also be seen that after calibration by the device and method of the present invention, the two low-pressure sensors have good measurement consistency and small deviation under the test condition near 5kPa.

Claims

1. A device for calibrating the initial reading of a pressure sensor under negative pressure in a wind tunnel, characterized in that: It includes a high-precision pressure controller, a three-way solenoid valve for gas circuit switching, a PLC controller and a program-controlled computer, among which: The low-pressure gas source interface of the high-precision pressure controller is connected to the first stop ball valve and the vacuum pump in sequence; The high-pressure gas source interface of the high-precision pressure controller is connected to the adjustable pressure reducing valve, the fourth stop ball valve and the high-pressure nitrogen bottle in sequence; The standard pressure output end of the high-precision pressure controller is connected to the first buffer tank, the second stop ball valve and the R end of the third gas circuit switching three-way solenoid valve in sequence to form a calibration channel No. 1; the P end of the third gas circuit switching three-way solenoid valve is connected to the second buffer tank and the wind tunnel chamber in sequence to form a test channel No. 2; the A end of the third gas circuit switching three-way solenoid valve is connected to the P end of the first gas circuit switching three-way solenoid valve, the P end of the second gas circuit switching three-way solenoid valve and the high-range pressure sensor, respectively, and the A ends of the first gas circuit switching three-way solenoid valve and the second gas circuit switching three-way solenoid valve are connected to the low-range pressure sensor and the mid-range pressure sensor, respectively; The program-controlled interface end of the high-precision pressure controller is connected to the program-controlled computer and the PLC controller through a network switch; the PLC controller is connected to the first, second and third gas path switching three-way solenoid valves and low, medium and high range pressure sensors respectively.

2. The device for calibrating the initial reading of a pressure sensor under negative pressure in a wind tunnel according to claim 1, characterized in that: A third stop ball valve is arranged on the pipeline between the second stop ball valve and the R end of the third gas path switching three-way solenoid valve, and a reserved spare interface is arranged at the third stop ball valve.

3. The device for calibrating the initial reading of a pressure sensor under negative pressure in a wind tunnel according to claim 1, characterized in that: A first gas filter is arranged between the first stop ball valve and the low-pressure gas source interface of the high-precision pressure controller; a second gas filter is arranged between the second buffer tank and the wind tunnel chamber; the A end of the third gas path switching three-way solenoid valve is respectively connected to the P end of the first gas path switching three-way solenoid valve, the P end of the second gas path switching three-way solenoid valve and the high-range pressure sensor through the third gas filter.

4. The device for calibrating the initial reading of a pressure sensor under negative pressure in a wind tunnel according to claim 3, characterized in that: The vacuum pump, the first stop ball valve, the first gas filter and the high-precision pressure controller are connected by G3 / 8 hard stainless steel pressure pipes, and the interfaces are sealed with glue.

5. The device for calibrating initial readings of a pressure sensor under negative pressure conditions in a wind tunnel according to claim 1, characterized in that: A first electric contact pressure gauge is arranged on the pipeline between the second stop ball valve and the R end of the third gas circuit switching three-way solenoid valve; a second electric contact pressure gauge is arranged between the second buffer tank and the P end of the third gas circuit switching three-way solenoid valve; a third electric contact pressure gauge is arranged between the high-pressure nitrogen bottle and the fourth stop ball valve, and a fourth electric contact pressure gauge is arranged between the adjustable pressure reducing valve and the high-pressure gas source interface of the high-precision pressure controller.

6. The device for calibrating initial readings of a pressure sensor under negative pressure in a wind tunnel according to claim 1, characterized in that: The vacuum pump is an oil-sealed rotary vane vacuum pump; the buffer tank is a stainless steel air pressure buffer tank.

7. The device for calibrating initial readings of a pressure sensor under negative pressure conditions in a wind tunnel according to claim 1, characterized in that: The gas circuit switching three-way solenoid valve is a zero-leakage three-way solenoid reversing valve, and the gas circuit switching three-way solenoid valve and the pressure sensor are connected through a standard 12mm outer diameter hose.

8. A method for calibrating the initial reading of a pressure sensor under negative pressure conditions in a wind tunnel, characterized in that: The steps include: Step 1: Turn on the high-precision pressure controller and preheat for half an hour; Step 2: Perform air tightness test on the device and turn on the power of the vacuum pump after the leakage meets the requirement; Step 3: Before taking the initial reading, open the first and second gas path switching three-way solenoid valves, connect the low-range pressure sensor, the mid-range pressure sensor and the measuring gas path, and the high-range pressure sensor is always in the measuring state; Step 4: Control the third gas circuit to switch the three-way solenoid valve to the R end to connect the calibration pressure gas circuit; Step 5: The output pressure of the high-precision pressure controller is used as the calibration pressure Pcal, and the pressure setting value is 60% of the full scale of the low-range pressure sensor; Step 6: When the calibration pressure reaches a steady state, start the initial reading calibration procedure; Step 7: The high-precision pressure controller returns to normal pressure; Step 8: Control the third gas circuit to switch the three-way solenoid valve to the P end, connect the test pressure gas circuit, and wait for the test; Step 9. After the test starts, the wind tunnel control system uses the true pressure values ​​of the mid-range pressure sensor and the high-range pressure sensor as reference to control the wind tunnel pressure to gradually approach the target pressure in the negative pressure direction. When the test pressure enters the working pressure range of the low-range pressure sensor, it switches to closed-loop control of the wind tunnel pressure using the true pressure value of the low-range pressure sensor as reference. The measurement system collects the true pressure value of the low-range pressure sensor for calculation of the wind tunnel flow field and model aerodynamic characteristic parameters.

9. A method for calibrating the initial reading of a pressure sensor in a wind tunnel negative pressure condition according to claim 8, characterized in that: The method for air tightness detection described in step 2 is: open the outlet valve of the high-pressure nitrogen bottle, and reduce the air pressure at the rear end of the adjustable pressure reducing valve to 300kPa-400kPa by adjustment; at the same time, close the first stop ball valve at the outlet end of the vacuum pump, and switch the air circuits of all low-range pressure sensors to be calibrated in the air circuit of the device to a closed state; connect the electric contact pressure gauge to the reserved spare interface, and open the third stop ball valve at the reserved spare interface at the same time, and then open all the stop ball valves to ensure that all the air circuits of the device are unobstructed; set the high-precision pressure controller so that the output pressure of its standard pressure output end is 300kPa, observe the display value of the pressure gauge connected to the reserved spare interface for 2 minutes, and record it every 30s, and finally calculate the recorded data to obtain the gas leakage amount of the entire device connecting the air circuit.

10. The method for calibrating the initial reading of a pressure sensor in a wind tunnel negative pressure condition according to claim 8, characterized in that: In step six, the method for determining whether the calibration pressure forms a steady state is as follows: when the pressure feedback value measured by the No. 1 calibration channel reaches within ±1 kPa of the given value output by the high-precision pressure controller, the control system delays determining whether the calibration pressure forms a steady state.

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