CN103868670A - Mach number control method of experimental section flow field of continuous transonic wind tunnel - Google Patents

Abstract

The invention relates to a method for controlling the Mach number of the flow field in the experimental section of a continuous transonic wind tunnel. According to the given target Mach number, the compressor speed n, the vane angle β and the grid finger position L, firstly maintain the vane angle β, The grid finger position L remains unchanged at the initial state, and the compressor speed n is adjusted to the target value; after the compressor speed n is in place, according to the specific experiment settings, first adjust the stator blade angle β, and then adjust the grid finger position L to the target value ; When the three parameters of compressor speed n, vane angle β, and gate finger position L are adjusted to the target values, the real-time measured Mach number of the test section is compared with the target Mach number, and the compressor speed, static Blade angle and grid finger until the actual Mach number approaches the target Mach number. The invention provides an idea for the Mach number control of the continuous transonic high Reynolds number wind tunnel flow field, and provides technical support for ensuring the smooth development of the national advanced aircraft.

Description

A Mach number control method for the flow field in the experimental section of a continuous transonic wind tunnel

technical field

The invention belongs to the field of aerospace, and in particular relates to a method for controlling the Mach number of a flow field in a continuous transonic wind tunnel experiment section. the

Background technique

The continuous transonic wind tunnel is a recirculation wind tunnel. The flow field in the experimental section is a transonic flow field, and a large number of blowing experiments can be carried out continuously. Its structure is shown in Figure 1. Through this wind tunnel, aircraft type selection experiments can be carried out, providing technical support for advanced airfoil type selection and advanced aircraft design. the

The continuous transonic wind tunnel has the following characteristics:

1) Dynamic experiment

The wind tunnel can continuously provide a stable experimental flow field (stable Mach number), and the continuous movement of the experimental model can be realized through a certain mechanism. It is one of the research hotspots concerned by scholars. the

2) Incoming flow Mach number control has high precision

The existing temporary wind tunnels in China use high-pressure gas source as power to establish the experimental flow field required for the experimental section by releasing the gas source instantaneously. The whole process lasts from a few seconds to tens of seconds, and there is a Mach number control accuracy. Shortcomings such as low flow field continuity and low stability. The continuous transonic wind tunnel can operate continuously, and the Mach number can be continuously controlled, so it has the characteristics of stable flow field in the experimental section and high control accuracy of incoming flow Mach number. the

3) High efficiency and low cost

At present, domestic transonic production wind tunnels are all stored in high-pressure air pipes. Each compression can only make the wind tunnel work for a few seconds to tens of seconds, and then re-compress the gas, so it has the characteristics of low efficiency and high cost. The continuous transonic wind tunnel can operate continuously (the Mach number is continuously controllable), so it has the characteristics of high efficiency and low cost. the

An important challenge in continuous transonic wind tunnel experiments is how to control the Mach number of the flow field in the experimental section, so that the Mach number can be continuously adjusted under normal pressure to meet the experimental requirements. The essence of continuous transonic wind tunnel Mach number control is how to control the power source of the wind tunnel (the speed of the motor and the angle of the vane of the axial flow compressor) and the two throat grid fingers to realize the experimental section on the basis of ensuring the safety of the wind tunnel operation. Precise control of flow field Mach number. "Experimental Fluid Mechanics" in the fourth issue of 2010, "NF-6 Wind Tunnel Mach Number Closed-loop Control System Design Research" through several graphs briefly introduces the Mach number control method, and then explains it with a flow chart, and finally Some control effects are given, but it does not involve the construction idea of continuous transonic wind tunnel Mach number control and the corresponding system equipment and control methods. the

Contents of the invention

technical problem to be solved

In order to avoid the deficiencies of the prior art, the present invention proposes a method for controlling the Mach number of the flow field in the experimental section of the continuous transonic wind tunnel to realize the Mach number control of the flow field of the continuous transonic wind tunnel. the

Technical solutions

A method for controlling the flow field Mach number in the experimental section of a continuous transonic wind tunnel, characterized in that the steps are as follows:

Step 1: Specify the target Mach number and the specific values of the three parameters of compressor speed n, vane angle β, and grid finger position L;

Step 2: Keep the vane angle β and grid finger position L unchanged in the initial state, and adjust the compressor speed n to the target value;

Step 3: After the compressor speed n is in place, according to the setting of the specific experiment, first adjust the vane angle β, and then adjust the grid finger position L to the target value;

Step 4: When the three parameters of compressor speed n, vane angle β, and gate finger position L are adjusted to the target values, compare the real-time measured Mach number of the test section with the target Mach number, and adjust the compressor speed according to the deviation value , vane angle and grid finger until the actual Mach number approaches the target Mach number. the

The preset target values of the three parameters of compressor speed n, vane angle β and grid finger position L are obtained according to wind tunnel debugging test experience. the

Beneficial effect

A continuous Mach number control method of the flow field in the experimental section of the transonic wind tunnel proposed by the present invention measures the Mach number in real time by simultaneously controlling the grid fingers, the motor and the axial flow compressor, and realizes the spanning of the experimental section of the wind tunnel under normal pressure. The establishment of the sonic flow field provides an idea for the Mach number control of the continuous transonic high Reynolds number wind tunnel flow field, and provides technical support for the smooth development of the country's advanced aircraft. the

Description of drawings

Figure 1 is a schematic diagram of the structure of a continuous transonic wind tunnel;

1-compressor, 2-wind tunnel test section, 3-grid finger, 4-anti-surge bypass quick valve

Figure 2 is a schematic diagram of the working principle of the continuous transonic wind tunnel Mach number control system;

Figure 3 is a schematic diagram of the Mach number control structure of a continuous transonic wind tunnel;

Figure 4 is a schematic structural diagram of the motor and axial compressor control subsystem;

Figure 5 is a schematic diagram of the motor speed control subsystem;

Fig. 6 is a schematic structural diagram of the Mach number measurement subsystem;

Figure 7 is a schematic structural diagram of the gate finger control subsystem;

Figure 8 is a schematic diagram of the structure of the Mach number control auxiliary system;

Figure 9 is a schematic diagram of the implementation of Mach number control in a continuous transonic wind tunnel;

Figure 10 is the Mach number distribution diagram of the core flow in the model area of the experimental section at different Mach numbers

Detailed ways

Now in conjunction with embodiment, accompanying drawing, the present invention will be further described:

The working principle of Mach number control is: the system uses high-precision pressure sensors (transmitters) to measure the total pressure and static pressure, and calculates the Mach number by using the measured total and static pressure values. The calculated value enters the closed-loop automatic control of the computer, and finally obtains The target Mach number within the accuracy specification. In order to reduce system interference, the sensor output is a large signal. The 16-bit A/D multi-function data acquisition card completes the total and static pressure acquisition, and the computer controls the compressor motor speed and vane angle or grid finger position to change the Mach number, and uses advanced intelligent control strategies to control the Mach number. Atmospheric pressure, the total temperature of the wind tunnel and the dry gas source pressure and humidity used to replace the humid air in the tunnel are also measured by the system. The working principle of the Mach number control system is shown in Figure 2. the

The idea of Mach number control is shown in Figure 3, including motor and axial flow compressor control subsystem, Mach number measurement subsystem, grid finger control subsystem, and auxiliary subsystem. The control and operation of the entire system is realized through the upper industrial computer. the

The control subsystem of the motor and axial flow compressor subsystem mainly completes the control of the motor and axial flow compressor speed and the vane angle, as shown in Figure 4. There are two ways to control the steady speed of the compressor motor: computer setting (digital and analog setting) and console manual setting. The specific principle control is shown in Figure 5. If the computer setting method is used, the motor speed command is transmitted from the industrial computer to the DC speed regulating device through the PLC system and then reaches the motor. The real-time speed of the motor is fed back to the industrial computer through the speed regulating device to realize the closed-loop control of the speed. The higher the motor speed means The greater the kinetic energy provided to the experimental section, the easier it is to establish the transonic flow field in the experimental section. At a certain fixed speed of the compressor, the change of the vane angle of the compressor can cause a significant change of the Mach number. Adjusting and controlling the vane angle of the compressor is one of the most important means of Mach number adjustment. The closed-loop control of the vane angle on the axial flow compressor can be realized through the industrial computer, which is used to change the flow rate at the inlet of the compressor and indirectly change the flow velocity field in the experimental section. the

The Mach number measurement subsystem mainly completes the measurement of the Mach number in the experimental section, as shown in Figure 6. The total static pressure measuring point in the wind tunnel is connected to the pressure sensor through the pipeline, and the total temperature measurement is connected to the temperature sensor. The measured values of the pressure and total temperature sensor are provided to the data acquisition card through electrical signals. The real-time value of Mach number in the experimental section is obtained through calculation. the

The grid finger control subsystem mainly completes the control of the grid finger displacement of the grid finger mechanism, as shown in Figure 7. The flow field in the wind tunnel test section can be controlled by the displacement of the grid finger, which is realized by controlling the grid finger mechanism through the servo motor. The industrial computer transmits the motion information to the AC servo controller through the motion control card, and drives The movement of the servo motor finally realizes the control of the movement of the grid fingers. the

The auxiliary system mainly completes the acquisition of auxiliary information during Mach number control, as shown in Figure 8. The acquisition of the working pressure of the wind tunnel body and the measurement of the humidity of the airflow in the wind tunnel will affect the implementation of Mach number control. the

The flow of the specific implementation method of Mach number control in the continuous transonic wind tunnel flow field is shown in Figure 9, and the steps are as follows:

1) Given the target Mach number, call the Mach number preset module, and the control software will automatically find the corresponding specific values of the three parameters of compressor speed n, stator blade angle β, and grid finger position L from the database;

2) Keep the vane angle β and grid finger position L unchanged in the initial state, and gradually adjust the compressor speed n to the target value;

3) After the compressor speed n is in place, according to the needs of the specific experiment, first adjust the stator blade angle β, then adjust the gate finger position L to the target value, and check whether the actual feedback is within the error range. If the actual parameters are not in place, Then continue to adjust according to the difference;

4) When the three parameters are adjusted to the target value, compare the real-time measured Mach value of the test section with the target Mach number, and adjust the compressor speed, vane angle and gate finger according to the deviation value until the actual Mach number approaches the target Mach number number. the

5) The preset target values of the three parameters of compressor speed n, vane angle β, and grid finger position L are calculated by the algorithm and wind tunnel debugging test experience, and some adaptive adjustments are made according to different types of tests. If it is desired to achieve a Mach number of 0.6 under normal pressure, the initial values of the three parameters of compressor speed n, vane angle β, and grid finger position L given in the preset module are: n=2500r/min, β= 45°, L=5mm. the

specific implementation effect

Figure 10 shows the Mach number distribution of the core flow in the model area at different Mach numbers. The abscissa in the figure is the distance from the point in the model area to the entrance of the experimental section. It can be seen from the figure that the Mach number distribution of the core flow is very uniform, and there is only a certain fluctuation when Ma=1.05. Table 1 shows the distribution of axial Mach number, root mean square deviation of Mach number, maximum Mach number deviation and Mach number gradient in the model area of the experimental section at different Mach numbers. When Ma<0.9, the root mean square deviation of the Mach number is less than 0.002, reaching the advanced index of the national military standard (GJB1179-91); and when Ma≥0.9, the root mean square deviation of the Mach number is less than 0.005, which also meets the qualified index of the national military standard ( GJB1179-91). the

Table 1: Distribution of core flow axial Mach number, root mean square deviation of Mach number, maximum Mach number deviation and Mach number gradient in the model area of the experimental section at different Mach numbers. the

Ma m ΔMmax σ _M dM/dX 0.2 0.2019 0.0011 0.0005 -0.0003 0.3 0.3018 0.0020 0.0006 -0.0002 0.4 0.4010 0.0024 0.0007 0.0004 0.5 0.5003 0.0030 0.0010 0.0004 0.6 0.6007 0.0035 0.0012 0.0007 0.7 0.6989 0.0041 0.0014 0.0007 0.75 0.7494 0.0046 0.0016 0.0013 0.8 0.7984 0.0046 0.0017 0.0011 0.85 0.8510 0.0049 0.0019 0.0013 0.9 0.9004 0.0054 0.0021 0.0013 0.95 0.9488 0.0057 0.0023 0.0011 1.0 0.9981 0.0064 0.0028 0.0009 1.05 1.0512 0.0184 0.0081 -0.0047

Claims (2)

1. a continous way transonic wind tunnel experimental section flow field Mach number control method, is characterized in that step is as follows:

Step 1: the concrete numerical value that refers to L tri-parameters in position to set the goal Mach number and compressor rotary speed n, static blade angle β, grid;

Step 2: keep static blade angle β, grid to refer to that position L is constant in original state, regulate compressor rotary speed n to desired value;

Step 3: after compressor rotary speed n puts in place, according to the setting of specific experiment, first regulate static blade angle β, rear adjusting grid to refer to that position L is to desired value;

Step 4: be adjusted to after desired value when compressor rotary speed n, static blade angle β, grid refer to tri-parameters of position L, test section Mach numerical value will be recorded in real time and target Mach number is compared, regulate compressor rotary speed, stator blade angle and grid to refer to according to deviate, until actual Mach number approaches target Mach number.

2. continous way transonic wind tunnel experimental section flow field Mach number control method according to claim 1, is characterized in that: described compressor rotary speed n, static blade angle β and grid refer to that the goal-selling value of tri-parameters of position L obtains according to tunnel debug test experience.

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