A control system and method for coupling adjustment of wind tunnel Mach number and axial density ratio

Abstract

The present invention discloses a control system and method for coupling adjustment of wind tunnel Mach number and axial density flow ratio, belonging to the field of wind tunnel experiment measurement and control in the aerospace industry; its structure includes an air source, a pressure stabilizing section, a convergence section, an experimental section, an AVDR control device and a control system, wherein the air source includes three Roots blowers, and the Ma of the experimental section is adjusted by controlling the opening of its butterfly valve; two Roots vacuum pumps are used to perform suction on the side wall of the experimental section, and different AVDRs are achieved by controlling the opening of its butterfly valve. The steps are: 1. Obtaining the relationship curve between Ma and the opening of the blower butterfly valve; 2. Automatically adjusting Ma and AVDR by using PID control. The present invention uses PID control to perform compound control of Ma and AVDR, which effectively solves the problems of low precision and long time consumption caused by manual adjustment in traditional experimental methods.

Description

Technical Field

[0001] The invention belongs to the field of wind tunnel experiment measurement and control in the aerospace industry, and specifically relates to a control system and method for coupling regulation of wind tunnel Mach number and axial density ratio. Background Art

[0002] A wind tunnel is a device that uses a power device to drive a controllable airflow within a pipe system to conduct various aerodynamic experiments based on the principles of relativity and similarity of motion.

[0003] At present, the commonly used wind tunnels can be divided into temporary wind tunnels and continuous wind tunnels according to the different driving methods. The continuous wind tunnel uses a controllable motor group and the fan or compressor driven by it as its driving system. The gas pressure in the wind tunnel pipe is increased by rotating the fan blades or the compressor rotor to maintain a stable flow field. Compared with the temporary wind tunnel, the continuous wind tunnel has the advantages of long continuous operation time and low operating costs.

[0004] The compressor is one of the key components of an aero-engine. Its design level not only determines the thrust-to-weight ratio, propulsion efficiency, maximum thrust and other key performance indicators of the aero-engine, but also has a significant impact on the stability of the engine. In the basic research on the performance of compressor blades, a large number of plane blade wind tunnel experiments should be carried out to verify the theoretical research. The plane blade is composed of many blades with the same geometric shape and arranged according to certain requirements and at a certain distance. It can be used to simulate the binary flow and angular separation of the compressor. Through the plane blade experiment, we can have an in-depth understanding of the performance of the blade, understand the aerodynamic performance of the blade under different inlet attack angles and incoming flow Ma, and accumulate data for the design and manufacture of new blades, which is of great significance to improving the overall performance of the compressor. In the plane blade experiment, due to the influence of the spanwise side wall boundary layer of the blade, the flow field of the 50% blade height section cannot achieve true two-dimensionality. AVDR is usually used to measure the two-dimensionality of the plane blade. The larger the AVDR value, the thicker the spanwise side wall boundary layer, that is, the worse the two-dimensionality of the blade.

[0005] During the continuous plane cascade wind tunnel experiment, the air flow entering the wind tunnel is adjusted by controlling the butterfly valve of the air source blower, thereby achieving the effect of controlling Ma. Suction chambers are installed on both sides of the experimental section, which are connected to the vacuum pump to remove the boundary layer on the spanning side wall, thereby achieving the effect of controlling AVDR. The suction volume is adjusted by controlling the opening of the vacuum pump butterfly valve to achieve different AVDRs.

[0006] The patent with publication number CN110161841A discloses a feedforward-fuzzy PID control method suitable for a transient transonic wind tunnel. The PID parameters are adjusted in real time through fuzzy reasoning to improve the control accuracy of the total pressure and Mach number. The patent with publication number CN110702361A discloses a flow field precision control system and control method for a DC transient transonic wind tunnel. The control method of PID control plus feedforward control and the optimization control of the flow field solves the control accuracy problem of 1.0-1.2 Mach numbers. The patent with publication number CN101887267B discloses a wind tunnel Mach number controller. The fuzzy control method with self-adjusting factors is used in the wind tunnel startup stage. When the Mach number is basically stable, PID control is used instead. The patent with publication number CN113008507A discloses a large-flow, high-stable Mach number wind tunnel rapid adjustment system and method based on a temporary air source. It adopts a composite control strategy of main valve feedforward and auxiliary valve closed-loop PID to solve the problem of the outlet Mach number being difficult to stabilize in wind tunnel experiments due to the continuous decrease in air source pressure and the poor repeatability, strong nonlinearity and slow adjustment speed of the main valve.

[0007] The above methods only consider the adjustment of Mach number. When it is necessary to adjust Mach number and axial flow ratio at the same time, the above methods for single variables are no longer applicable. In traditional blade cascade experiments, Mach number Ma and axial flow ratio are both manually adjusted, and these two parameters are coupled with each other. When one parameter is adjusted, the other parameter will also be greatly affected. It is difficult to find the regulation law during the experiment, and the operator needs to have rich experience. At the same time, a set of blade cascades often needs to be tested under multiple Mach numbers and axial flow ratio conditions. Manual adjustment will take a lot of time and effort, and it is difficult to ensure the accuracy of the regulation results. Summary of the invention

[0008] Technical issues to be solved:

[0009] In order to avoid the shortcomings of the prior art, the present invention provides a control system and method for coupled regulation of wind tunnel Mach number (Ma) and axial velocity density ratio (AVDR), which adopts PID control method to perform composite control of Mach number and axial velocity density ratio of a wind tunnel test section, and can effectively solve the problems of low precision and long time consumption caused by manual adjustment in traditional experimental methods.

[0010] The technical solution of the present invention is: a control system for coupling adjustment of wind tunnel Mach number and axial density ratio, characterized in that it includes an air source, a pressure stabilizing section, a convergent section, an experimental section, an AVDR control device, a pressure sensor and a control system, wherein the air source, the pressure stabilizing section and the convergent section are sequentially installed at the entrance of the experimental section, the experimental section is used to install a cascade test piece and perform relevant parameter measurements, and the AVDR control device is arranged on both sides of the experimental section;

[0011] The Mach number Ma of the experimental section is adjusted by controlling the opening of the butterfly valve of the air source, and different AVDRs are achieved by controlling the opening of the butterfly valve of the AVDR control device; the control system calculates Ma and AVDR in real time according to the input Ma, AVDR instructions and the measurement results of the pressure sensor to automatically adjust the air source and the opening of the butterfly valve of the AVDR control device.

[0012] A further technical solution of the present invention is: the air source includes three Roots blowers, which can realize a blade blowing experiment with an inlet Mach number of 0.3 to 0.95.

[0013] A further technical solution of the present invention is that the voltage stabilizing section is cylindrical with a constant diameter.

[0014] A further technical solution of the present invention is: the convergent section includes a round-to-square structure and an adjustable rectangular convergent section, the round-to-square structure enables the wind tunnel duct to transition from a cylindrical pressure-stabilizing section to a rectangular cross-section that is convenient for blowing in blade cascade experiments; the inlet of the adjustable rectangular convergent section is the outlet of the round-to-square structure, its outlet width is fixed, and the outlet height can be adjusted according to different experimental working conditions of the blade cascade.

[0015] A further technical solution of the present invention is that the relevant parameter measurements carried out in the experimental section include the total temperature and total pressure of the airflow before the grating, the static pressure on the wall before the grating, the total pressure and static pressure of the airflow after the grating, the airflow angle at the blade outlet and the static pressure on the wall after the grating.

[0016] A further technical solution of the present invention is: the blade grid test piece is composed of a rectangular grid plate and straight blades mounted thereon, and the straight blade refers to a blade whose blade shape is completely consistent from the root to the tip of the blade, and the centroid line of the blade shape is perpendicular to the plane where the root of the blade is located.

[0017] A further technical solution of the present invention is: the AVDR control device comprises a suction hood installed on both sides of the experimental section and two Roots vacuum pumps, and the suction capacity thereof can achieve an AVDR of 1.0 to 1.2 in the experimental section.

[0018] A control method for a control system for coupling adjustment of wind tunnel Mach number and axial density ratio, characterized by the following specific steps:

[0019] Step 1: After installing the cascade test piece to the test section, keep the vacuum pump butterfly valve fully open, and manually close the blower butterfly valve continuously, so that the test section Ma exceeds the maximum Ma required by the test conditions, and obtain the relationship curve between Ma and the opening of the blower butterfly valve;

[0020] Step 2: Manually open all the blower butterfly valves, start the automatic adjustment mode of Ma and AVDR, and adjust Ma and AVDR in turn according to the set target Mach number Ma* and target axial flow ratio AVDR* through the PID control method until the errors between Ma and AVDR and the target values ​​meet the requirements, that is, one measurement is completed.

[0021] A further technical solution of the present invention is: in step 2, automatically adjusting the Ma and AVDR modes comprises the following steps:

[0022] (1) Input all Ma values ​​and AVDR values ​​to be measured this time;

[0023] (2) Set the target Mach number Ma* to the maximum intended measurement value;

[0024] (3) Set the target axial density flow ratio AVDR* to the maximum intended measurement value;

[0025] (4) According to the target Mach number Ma*, the blower butterfly valve is closed to the blower butterfly valve opening obtained by interpolation of the Ma-blower butterfly valve opening relationship curve;

[0026] (5) PID adjusts the blower butterfly valve so that the error between the real-time Mach number Ma0 and the target Mach number Ma* is less than a given range;

[0027] (6) PID adjusts the vacuum pump butterfly valve so that the error between the real-time axial flow ratio AVDR0 and the target axial flow ratio AVDR* is less than a given range;

[0028] (7) Repeat steps (5) and (6) until the error requirements of Ma* and AVDR* are met at the same time, that is, measurement is performed under the current Ma* and AVDR*;

[0029] (8) Set AVDR* as the remaining intended measurement value, repeat steps (4)-(7) to complete the measurement of all AVDRs under the current Ma*;

[0030] (9) Set Ma* as the remaining intended measurement value and repeat steps (3)-(8) to complete the measurement of all Ma and AVDR;

[0031] (10) End this measurement.

[0032] A further technical solution of the present invention is: the PID adjustment method is based on the deviation between the current real-time value and the target value according to U(k)=Kp E(k)+K I ∑E(k)+K D E c (k) Control and adjust parameter K according to actual conditions p , K I , K D , where E(k) is the difference between the current value and the target value, E c (k) is the rate of change of E(k) per unit time, K p is the proportional gain coefficient, K I is the integral gain coefficient, K D is the differential gain coefficient.

[0033] Beneficial Effects

[0034] The beneficial effects of the present invention are as follows: based on the PID adjustment method, the present invention can realize the coupled adjustment of Ma and AVDR in the plane blade wind tunnel experiment. The operator only needs to obtain the relationship curve between Ma and the opening of the blower butterfly valve by manual adjustment, and input the Ma and AVDR values ​​to be measured this time, and the control system can automatically complete the subsequent measurement work. Compared with the traditional experimental method of manually adjusting each Ma and AVDR in turn, the adjustment accuracy can be greatly improved and the experimental time can be significantly shortened.

[0035] In traditional blade cascade experiments, Ma and AVDR are manually adjusted, and these two parameters are coupled with each other. It is difficult to find the control rules during the experiment, which requires the operator to have rich experience. A set of blade cascades often needs to be tested under multiple Ma and AVDR conditions. Manual adjustment will take a lot of time and effort, and it is difficult to ensure the accuracy of the control results. The PID control method is used to automatically adjust Ma and AVDR, which can be adjusted accurately and quickly, greatly improving the experimental efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic diagram of the control system structure suitable for a continuous plane cascade wind tunnel to simultaneously adjust the Mach number and the axial density ratio;

[0037] Figure 2 The present invention is a flow chart of a control method for simultaneously adjusting the Mach number and the axial density ratio of a continuous plane cascade wind tunnel. DETAILED DESCRIPTION

[0038] The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, but should not be construed as limiting the present invention.

[0039] This embodiment is a control system and method for coupling adjustment of Mach number and axial density ratio of a continuous plane cascade wind tunnel, and its structure diagram is as follows: Figure 1As shown, it includes an air source, a pressure stabilizing section, a convergent section, an experimental section, a vacuum pump, a pressure sensor and a control system. The air source includes three Roots blowers to realize the blade blowing experiment with an inlet Mach number of 0.3 to 0.95. The Ma of the experimental section is adjusted by controlling the opening of its butterfly valve; the pressure stabilizing section is a cylindrical structure with equal diameter; the convergent section of the wind tunnel is divided into two parts. The first part is a round-to-square structure, which makes the wind tunnel duct transition from the cylindrical pressure stabilizing section to a rectangular section that is convenient for the blade experiment to blow air. The second part is an adjustable rectangular convergent section that is easy to adjust. Its outlet width is fixed, and the outlet height can be adjusted according to different experimental conditions of the blade (the vertical direction is the height direction, and the vertical direction is the width direction); the experimental section is used to install the blade test piece and conduct related parameters (total temperature and total pressure of the airflow in front of the blade, static pressure on the wall in front of the blade, total pressure and static pressure of the airflow behind the blade, airflow angle at the blade outlet and wall behind the blade The cascade test piece is composed of a rectangular cascade plate and straight blades mounted thereon. A straight blade refers to a blade with a completely consistent blade shape from the root to the tip of the blade, and the centroid line of the blade shape is perpendicular to the plane where the root of the blade is located; the AVDR control device includes a suction hood installed on both sides of the experimental section and two Roots vacuum pumps. The vacuum pump is connected to the side wall of the experimental section through a suction chamber. Its suction capacity can achieve an AVDR of 1.0 to 1.2 in the experimental section, and different AVDRs can be achieved by controlling the opening of its butterfly valve; the control system can calculate Ma and AVDR in real time according to the measurement results of the pressure sensor in the experimental section, and then automatically adjust the opening of the blower and vacuum pump butterfly valves through PID control according to the input Ma, AVDR instructions and the calculated real-time results.

[0040] The adjustment flow chart in the experiment is shown in the attached figure. Figure 2 The adjustment method is as follows:

[0041] 1. After installing the cascade test piece to the test section, keep the vacuum pump butterfly valve fully open and manually close the blower butterfly valve continuously, so that the test section Ma exceeds the maximum Ma required by the test conditions, and obtain the relationship curve between Ma and the opening of the blower butterfly valve;

[0042] 2. Manually open all the butterfly valves of the blower and turn on the automatic adjustment Ma and AVDR modes;

[0043] 3. Enter all the Ma values ​​that need to be measured this time {Ma1, Ma2, ..., Ma n} and AVDR value (AVDR1, AVDR2, ..., AVDR m};

[0044] 4. Set the target Mach number (Ma*) to the maximum intended measured value Ma n ;

[0045] 5. Set the target axial density flow ratio (AVDR*) to the maximum intended measured value AVDRm ;

[0046] 6. According to the Ma* required by the experimental working conditions, the Ma-blower butterfly valve opening relationship curve obtained in step 1 is interpolated to obtain the corresponding blower butterfly valve opening;

[0047] 7. To ensure the safety of the experiment and avoid overpressure operation of the blower, keep the vacuum pump butterfly valve in the fully open state, and close the blower butterfly valve to 110% of the opening found in 6;

[0048] 8. Check the real-time Mach number (Ma0) at this time, and select the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) PID adjustment is performed on the blower butterfly valve so that the absolute value of the difference between Ma0 and Ma* is less than 0.005;

[0049] 9. Check the real-time axial density ratio (AVDR0) at this time. If AVDR0 is less than AVDR* or greater than AVDR* by no more than 0.01, measure it. The current AVDR0 is the maximum AVDR value of this blade at the current Ma* and angle of attack.

[0050] If AVDR0 is greater than AVDR* by more than 0.03, by selecting the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) Perform PID adjustment on the vacuum pump butterfly valve so that AVDR0 is adjusted to the average value of the current value and AVDR* within the scope;

[0051] If AVDR0 is greater than AVDR* by more than 0.01 but not more than 0.03, by selecting appropriate PID parameters

[0052] K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) Perform PID adjustment on the vacuum pump butterfly valve so that AVDR0 is adjusted to within the scope;

[0053] 10. Check Ma0 at this time. If the absolute value of the difference between Ma0 and Ma* is less than 0.005, do not adjust the blower butterfly valve;

[0054] If the absolute value of the difference between Ma0 and Ma* exceeds 0.015, by selecting the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) Perform PID adjustment on the blower butterfly valve so that Ma0 is adjusted to the average value of the current value and Ma* within the scope;

[0055] If the absolute value of the difference between Ma0 and Ma* exceeds 0.005 but does not exceed 0.015, by selecting the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) Perform PID adjustment on the blower butterfly valve so that Ma0 is adjusted to within the scope;

[0056] 11. Check AVDR0 at this time. If the absolute value of AVDR0 and AVDR* is less than 0.01, do not adjust the vacuum pump butterfly valve;

[0057] If the absolute value of the difference between AVDR0 and AVDR* exceeds 0.03, by selecting the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+K I ∑E(k)+K D E c (k) Perform PID adjustment on the vacuum pump butterfly valve so that AVDR0 is adjusted to the average value of the current value and AVDR* within the scope;

[0058] If the absolute value of the difference between AVDR0 and AVDR* exceeds 0.01 but does not exceed 0.03, by selecting the appropriate PID parameter K p , K I , K D , according to U(k)=K p E(k)+KI ∑E(k)+K D E c (k) Perform PID adjustment on the vacuum pump butterfly valve so that AVDR0 is adjusted to within the scope;

[0059] 12. Repeat steps 10 and 11 until both the absolute value of the difference between Ma0 and Ma* is less than 0.005 and the absolute value of the difference between AVDR0 and AVDR* is less than 0.01, that is, the measurement under the current Ma* and AVDR* is performed;

[0060] 13. Set AVDR* as the remaining intended measurement values ​​in descending order, and repeat steps 9-12 to complete the measurement of all AVDRs under the current Ma*;

[0061] 14. Set Ma* as the remaining intended measurement values ​​in descending order, and repeat steps 6-12 to complete the measurement of all Ma and AVDR;

[0062] Open all the butterfly valves of the blower and vacuum pump and turn them off.

[0063] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention without departing from the principles and intent of the present invention.

Claims

1. A control system for coupling adjustment of wind tunnel Mach number and axial density ratio, characterized in that: It includes an air source, a pressure stabilizing section, a convergent section, an experimental section, an AVDR control device, a pressure sensor and a control system. The air source, the pressure stabilizing section and the convergent section are sequentially installed at the entrance of the experimental section. The experimental section is used to install the cascade test piece and measure related parameters. The AVDR control device is arranged on both sides of the experimental section. The Mach number Ma of the experimental section is adjusted by controlling the opening of the butterfly valve of the gas source, and different AVDRs are achieved by controlling the opening of the butterfly valve of the AVDR control device; the control system calculates Ma and AVDR in real time according to the input Ma and AVDR instructions and the measurement results of the pressure sensor to automatically adjust the gas source and the opening of the butterfly valve of the AVDR control device; The control method of the control system for coupling adjustment of the wind tunnel Mach number and the axial density ratio comprises the following specific steps: Step 1: After installing the cascade test piece to the test section, keep the vacuum pump butterfly valve fully open, and manually close the blower butterfly valve continuously, so that the test section Ma exceeds the maximum Ma required by the test conditions, and obtain the relationship curve between Ma and the opening of the blower butterfly valve; Step 2: Manually open all the butterfly valves of the blower, start the automatic adjustment mode of Ma and AVDR, and adjust Ma and AVDR in turn according to the set target Mach number Ma* and target axial density flow ratio AVDR* through the PID control method until the errors between Ma and AVDR and the target values ​​meet the requirements, that is, one measurement is completed; The automatic adjustment of Ma and AVDR modes comprises the following steps: (1) Input all Ma values ​​and AVDR values ​​to be measured this time; (2) Set the target Mach number Ma* to the maximum intended measurement value; (3) Set the target axial density flow ratio AVDR* to the maximum intended measurement value; (4) According to the target Mach number Ma*, close the blower butterfly valve to the blower butterfly valve opening obtained by interpolation of the Ma-blower butterfly valve opening relationship curve; (5) PID adjusts the blower butterfly valve to make the real-time Mach number The error with the target Mach number Ma* is less than a given range; (6) PID adjusts the vacuum pump butterfly valve to achieve real-time axial density flow ratio The error with the target axial density ratio AVDR* is less than a given range; (7) Repeat steps (5) and (6) until the error requirements of Ma* and AVDR* are met at the same time, that is, measurement is performed under the current Ma* and AVDR*; (8) Set AVDR* as the remaining intended measurement value and repeat steps (4) to (7) to complete the measurement of all AVDRs under the current Ma*; (9) Set Ma* as the remaining intended measurement value and repeat steps (3) to (8) to complete the measurement of all Ma and AVDR; (10) End the measurement; The PID adjustment method is based on the deviation between the current real-time value and the target value. Control and adjust parameters according to actual conditions ,in is the difference between the current value and the target value, In unit time The rate of change, is the proportional gain coefficient, is the integral gain coefficient, is the differential gain coefficient.

2. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to claim 1 is characterized in that: The air source includes three Roots blowers, which can realize a blade blowing experiment with an inlet Mach number of 0.3 to 0.

95.

3. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to claim 1 is characterized in that: The voltage stabilizing section is in the shape of a cylinder with a constant diameter.

4. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to claim 1 is characterized in that: The convergent section includes a round-to-square structure and an adjustable rectangular convergent section. The round-to-square structure enables the wind tunnel duct to transition from a cylindrical pressure-stabilizing section to a rectangular cross-section that is convenient for blowing in blade cascade experiments. The inlet of the adjustable rectangular convergent section is the outlet of the round-to-square structure, and its outlet width is fixed, and the outlet height can be adjusted according to different experimental working conditions of the blade cascade.

5. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to claim 1 is characterized in that: The relevant parameter measurements carried out in the experimental section include the total temperature and total pressure of the airflow before the cascade, the static pressure on the wall before the cascade, the total pressure and static pressure of the airflow after the cascade, the airflow angle at the blade outlet and the static pressure on the wall after the cascade.

6. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to claim 1 is characterized in that: The blade cascade test piece is composed of a rectangular cascade plate and straight blades mounted thereon. A straight blade refers to a blade whose blade shape is completely consistent from the blade root to the blade tip, and the centroid line of the blade shape is perpendicular to the plane where the blade root is located.

7. The control system for coupling adjustment of wind tunnel Mach number and axial flow ratio according to any one of claims 1 to 6, characterized in that: The AVDR control device includes a suction hood installed on both sides of the experimental section and two Roots vacuum pumps, and its suction capacity can achieve an AVDR of 1.0 to 1.2 in the experimental section.

Images