Axial detection tube for correcting flow field uniformity influence of subsonic wind tunnel and application of axial detection tube

Abstract

The invention discloses an axial detection tube for correcting the flow field uniformity influence of a subsonic speed wind tunnel and application of the axial detection tube, and aims at solving the problem that extra interference is introduced into wind tunnel test data due to the fact that the total pressure of airflow in a test section and the total pressure of a stable section of a large-size wind tunnel or a three-sound-speed wind tunnel adopting a flexible-wall spray pipe possibly have a large difference. Belongs to the wind tunnel test field. The device comprises a nose cone, a measuring section, a connecting section used for being connected with a test adapter, and a pressure measuring nozzle used for being connected with a pressure measuring pipe, wherein the nose cone, the measuring section and the connecting section are sequentially connected into a whole and are coaxially arranged; the nose cone is integrally in a cone shape, the nose cone is in a circular arc shape, and the rear end of the nose cone is in smooth transition with the measuring section. The axial detection tube is provided with the total pressure measuring points, the Mach number distribution of each axial measuring point is calculated by using the total pressure value actually measured by the test section, and the accuracy of flow field uniformity calculation of the test section is improved.

Description

Technical Field

[0001] This application relates to the field of wind tunnel tests, especially the field of wind tunnel test calibration. Specifically, it is an axial probe tube for correcting the influence of the flow field uniformity of a subsonic wind tunnel and its application. Background Art

[0002] The flow field uniformity of the wind tunnel test section is directly related to the quality of test data and the operation of equipment, and is a key content in the comprehensive performance debugging and flow field calibration of the wind tunnel. At present, according to the test scope and requirements, an axial probe tube is usually used to measure the Mach number distribution of the core flow in the test sections of subsonic and transonic wind tunnels, calculate the flow field uniformity index, and provide input data for the operation of the wind tunnel and data correction. In the domestic and foreign wind tunnel test fields, the requirements for the measuring point spacing and data processing of the axial probe tube have been clarified according to the operation requirements of the wind tunnel and the requirements for test accuracy, and preliminary standard specifications have been formed. For example, "Subsonic Wind Tunnel and Transonic Wind Tunnel Calibration" (AIAA R-093-2003) published by the American Institute of Aeronautics and Astronautics (AIAA) in 2003, and "Requirements for the Flow Field Quality of Low-Speed Wind Tunnels and High-Speed Wind Tunnels" (GJB-1179A-2012) compiled and revised by the China Aerodynamics Research and Development Center, etc.

[0003] The main method of using an axial probe tube to measure the Mach number distribution of the core flow in the test sections of subsonic and transonic wind tunnels is to install the axial probe tube on the middle support of the wind tunnel, calculate the Mach number of each measuring point by using the total pressure measured in the wind tunnel settling chamber and the static pressure measured by the axial probe tube, and then calculate indexes such as the operation correction relationship, axial gradient, and root mean square deviation by using statistical laws for use in the operation of the wind tunnel and the evaluation and correction of test data.

[0004] The above method has simple principles and high applicability, but the differences between the total pressure of the core flow in the test section and the total pressure in the settling chamber, and the differences in the wind tunnel support mechanism between the flow calibration and the model test are ignored during operation. For a solid-block nozzle wind tunnel with a size of less than 1 meter, the distance between the settling chamber and the test section is short, and the error caused by using the total pressure in the settling chamber instead of the total pressure in the test section can be ignored. However, for a large-sized wind tunnel or a three-sonic wind tunnel with a flexible-wall nozzle, there may be a large difference between the total pressure of the airflow in the test section and the total pressure in the settling chamber, and this difference cannot be ignored, otherwise it will introduce additional errors in the calculation of the Mach number in the test section, affect the calculation of the flow field uniformity index, and introduce additional interference in the wind tunnel test data.

[0005] Therefore, there is an urgent need for a new device and / or method to solve the above problems. Summary of the Invention

[0006] The object of the invention of this application is: for large-scale wind tunnels or three-speed sound wind tunnels with flexible-wall nozzles, there may be a large difference between the total pressure of the airflow in the test section and the total pressure in the settling chamber, which will introduce additional interference into the wind tunnel test data. To provide an axial probe tube for correcting the influence of the flow field uniformity of a subsonic wind tunnel and its application.

[0007] To achieve the above object, this application adopts the following technical solutions: An axial probe tube for correcting the influence of the flow field uniformity of a subsonic wind tunnel, including a nose cone, a measurement section, a connection section for connecting with a test adapter, and a pressure measuring nozzle for connecting with a pressure measuring tube. The nose cone, the measurement section, and the connection section are connected in sequence as a whole and are coaxially arranged; The nose cone is integrally conical, the outer shape of the nose cone is arc-shaped, and the rear end of the nose cone is smoothly transitioned with the measurement section; The measurement section is integrally circular tubular; The connection section includes a first connection part and a second connection part. The cross-section of the first connection part along the direction perpendicular to its axis is integrally frustum-shaped, and the cross-section of the second connection part along the direction perpendicular to its axis is integrally inverted frustum-shaped. The outer diameter of the large end of the first connection part is greater than the outer diameter of the large end of the second connection part, and the large end of the first connection part is connected to the large end of the second connection part; The connection section is smoothly transitioned with the measurement section through the first connection part and the first connection part can play a rectifying role. A reference platform is arranged on the outer surface of the first connection part close to the second connection part, and the reference platform can be used for installing and leveling the axial probe tube in the pitch and roll directions. The reference platform is parallel to the central axis of the axial probe tube; The inside of the axial probe tube is a hollow through hole for arranging a pressure measuring tube; The nose cone is provided with a total pressure hole and a first static pressure hole. The total pressure hole penetrates the nose cone. The total pressure hole is located on the central axis of the axial probe tube. The first static pressure hole is arranged along the tangent direction of the conical surface; Taking the plane where the reference platform is located relative to the roll direction of the axial probe tube as 0°; There are two first static pressure holes. The measurement section is provided with 2N second static pressure holes, where N is a natural number and N≥1. The first static pressure holes and the second static pressure holes are correspondingly arranged on the straight lines at the 0° and 180° positions of the measurement section relative to the plane where the reference platform is located; Or there are four first static pressure holes. The measurement section is provided with 4N second static pressure holes, where N is a natural number and N≥1. The first static pressure holes and the second static pressure holes are correspondingly arranged on the straight lines at the 0°, 90°, 180°, and 270° positions of the measurement section relative to the plane where the reference platform is located; The center point of the first static pressure hole and the center point of the second static pressure hole at the corresponding position are located on the same plane, and the first static pressure hole and the second static pressure hole are evenly distributed along the central axis of the axial detection tube; The nose cone of the axial detection tube is located inside the wind tunnel test section; The total pressure hole, the first static pressure hole, and the second static pressure hole are respectively guiding cones with a set ratio, and the guiding cones can ensure vertical installation. The total pressure hole is installed in cooperation with the pressure measuring nozzle, and the central axis of the total pressure hole coincides with the central axis of the corresponding pressure measuring nozzle. The first static pressure hole is installed in cooperation with the pressure measuring nozzle, and the central axis of the first static pressure hole coincides with the central axis of the corresponding pressure measuring nozzle. The second static pressure hole is installed in cooperation with the pressure measuring nozzle, and the central axis of the second static pressure hole coincides with the central axis of the corresponding pressure measuring nozzle.

[0008] The total pressure hole is a pressure measuring hole located at the theoretical tip of the nose cone. The head of the nose cone is truncated and provided with a 90° chamfer to expand the insensitive angle of the total pressure measurement point of the total pressure hole to the air flow direction.

[0009] A wedge-shaped hole for connecting with a test adapter is provided on the second connecting part, or a thread for connecting with a flange is provided on the second connecting part.

[0010] The test adapter is one of a straight adapter and a double-rotating shaft adapter.

[0011] The pressure measuring nozzle is a pressure-sensitive device located on the tube body of the axial detection tube, which is cylindrical. Its upper surface is flush with the outer surface of the axial detection tube, its lower surface is flush with the inner wall of the tube body of the axial detection tube, and a pressure measuring tube is arranged in the middle to introduce the pressure of the measurement section of the axial detection tube into the tube body and lead it out to the pressure measuring sensor through the pressure measuring tube.

[0012] The application of the aforementioned axial detection tube includes the following steps: S1. Install the axial detection tube in the wind tunnel that needs to be flow field calibrated through a test adapter, and use the reference platform set on the connecting section to level the pitch and roll of the axial detection tube; S2. After connecting the total pressure measurement point of the total pressure hole, the static pressure measurement point of the first static pressure hole, and the static pressure measurement point of the second static pressure hole to the pressure sensor respectively, conduct the test to obtain the total pressure of the air flow in the test section and the static pressure of each measurement point; S3. Calculate the Mach number of each measurement point in the measurement section using the isentropic relationship as the core flow Mach number of the test section flow field; S4. Use the standard method to calculate the average Mach number of the core flow, the root mean square deviation of the axial distribution, and the axial gradient as the input for wind tunnel operation, flow field uniformity evaluation, and model test data skin friction correction.

[0013] The operation of step S1 is as follows: S1.1 Connect the test adapter to be calibrated and tested to the middle bracket of the wind tunnel; S1.2 Connect the axial detection tube to the test adapter; S1.3 Use the reference platform to measure the pitch angle and roll angle of the axial detection tube, and adjust the wind tunnel vane and roll mechanism so that the absolute angles of the pitch angle and roll angle are less than 0.03° respectively; The total pressure measurement point is a pressure measurement hole located at the theoretical tip of the nose cone. The head is truncated and a 90° chamfer is set to expand the insensitive angle of the total pressure measurement point to the air flow direction.

[0014] In step S1.2, it is connected and tightened through the conical surface of the axial detection tube and the front end of the test adapter; Or a flange is provided on the connecting section of the axial detection tube, and the axial detection tube is connected to the test adapter through the flange.

[0015] The test adapter refers to the transfer mechanism between the strut and the middle bracket of the wind tunnel, ensuring that the model and the balance are installed at the center of the test section; the test adapter is a straight head, or the test adapter is a double-rotating shaft joint with a pre-bias angle to increase the model attitude.

[0016] The attitude leveling refers to using the wind tunnel vane mechanism and roll mechanism to level the installation attitude of the axial detection tube to ensure that the axis of the axial detection tube coincides with the axis of the test section. According to the calibration requirements of the subsonic wind tunnel, the absolute values of the attitude angles in the pitch and roll directions should be less than 0.03°.

[0017] The test in step S2 refers to the flow field calibration test, that is, the wind tunnel constant total temperature and variable total pressure Mach number test. After each step of the flow field is stable, the total pressure at the head of the axial detection tube and the static pressure value at the measurement section are measured through the pressure sensor.

[0018] The total pressure of the test section air flow refers to the pressure when the air flow in the test section is isentropically stagnated to zero velocity, which is used as the input condition for calculating the Mach number of each measurement point in the measurement section of the axial detection tube. Due to the air flow friction effect, the total pressure of the test section air flow is slightly lower than the total pressure of the stable section.

[0019] The nose cone is a component with a gradually expanding diameter at the front of the axial detection tube to reduce the influence of the tube body on the air flow. To reduce the flow field disturbance caused by the profile discontinuity at the connection between the nose cone and the measurement section, a circular arc shape is adopted and it is smoothly transitioned to the connection with the measurement section.

[0020] The second static pressure hole refers to the static pressure measurement points distributed on the measurement section of the axial detection tube, which are arranged in two rows (upper and lower) or four rows (upper, lower, left, and right) along the axis of the axial detection tube. The spacing between each measurement point and the diameter of the measurement point can be determined according to the diameter of the wind tunnel test section.

[0021] The isentropic relationship assumes that the operating medium in the test section is an ideal gas, the internal energy depends only on temperature, and the temperature remains constant during the short time of test acquisition, that is, it meets the requirements of an adiabatic and reversible thermodynamic process. At this time, the simplified relationship between the total pressure and static pressure of the air flow can be used to solve the Mach number of the measurement point.

[0022] The standard method refers to the method of calculating the flow field uniformity index by using the core flow Mach number distribution according to the "Requirements for the Flow Field Quality of Low-Speed Wind Tunnels and High-Speed Wind Tunnels" (GJB 1179A-2012).

[0023] The floating resistance correction refers to using data such as the axial gradient of Mach number, model volume or cross-sectional area distribution to calculate the additional resistance caused by the axial static pressure gradient in the test section, and correcting the test results to improve the accuracy of the data.

[0024] As mentioned above, in view of the requirements for the evaluation of the flow field of subsonic wind tunnels, in order to improve the accuracy of the measurement of the flow field uniformity and ensure the consistency between the flow field calibration state and the wind tunnel operation state, the present invention proposes an axial probe tube for correcting the influence of the flow field uniformity of subsonic wind tunnels and its application to realize the functions of total pressure measurement in the test section and evaluation of the influence of test adapters.

[0025] In summary, due to the adoption of the above technical solutions, the beneficial effects of the present invention are as follows: (1) The axial probe tube of the present application is provided with total pressure measurement points, and the Mach number distribution of each axial measurement point is calculated using the total pressure value measured in the test section, improving the accuracy of the calculation of the flow field uniformity in the test section; (2) The pressure measurement holes in the measurement section of the axial probe tube of the present application adopt a guiding cone to ensure that each static pressure measurement point is perpendicular to the axis of the axial probe tube, reducing the influence of the processing quality of the static pressure measurement points on the measurement results; (3) A reference platform is arranged at the rear of the axial probe tube of the present application to ensure the installation attitude of the device, facilitate inspection and maintenance, and reduce the installation errors of different personnel at different times; (4) The connection section is connected to the test adapter in a variety of connection methods, and the rear support during calibration is completely consistent with the model test, avoiding the difference in the measurement results of the Mach number gradient caused by directly installing the axial probe tube on the middle support of the wind tunnel in the traditional measurement method, and improving the accuracy of the floating resistance correction.

[0026] Other advantages, objectives and features of the present invention will be partially reflected by the following description and partially understood by those skilled in the art through the research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention will be described by way of examples with reference to the accompanying drawings, wherein: Figure 1 It is a schematic diagram of the overall structure of the axial probe tube in Embodiment 1.

[0028] Figure 2 It is the axial detection tube head cone sectional view in Embodiment 1.

[0029] Figure 3 It is the structural schematic diagram of the axial detection tube connection section in Embodiment 1.

[0030] Figure 4 It is the schematic diagram of the measurement result of the axial distribution of the Mach number in the test section.

[0031] Figure 5 It is the comparison curve of the floating resistance correction amount.

[0032] Markings in the figure: 1. Head cone, 2. Measurement section, 3. Connection section, 4. First static pressure hole, 5. Second static pressure hole, 6. Reference platform, 7. Total pressure hole, 8. Connection part 1, 9. Connection part 2, 10. Wedge-shaped hole, 11. Thread. Detailed implementation manners

[0033] All features disclosed in this specification, or all steps in the disclosed methods or processes, except for mutually exclusive features and / or steps, can be combined in any way.

[0034] Any feature disclosed in this specification, unless specifically described, can be replaced by other equivalent or similar-purpose alternative features. That is, unless specifically described, each feature is only an example in a series of equivalent or similar features.

[0035] The following further describes the present invention in detail with reference to the accompanying drawings, so that those skilled in the art can implement it according to the description in the specification.

[0036] It should be understood that terms such as "having", "comprising" and "including" used herein do not exclude the presence or addition of one or more other elements or their combinations.

[0037] It should be noted that in the description of the present invention, the orientation or positional relationship indicated by the terms is based on the orientation or positional relationship shown in the accompanying drawings. It is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it cannot be understood as a limitation to the present invention. In addition, the terms "Ⅰ" and "Ⅱ" are only for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0038] In the description of the present invention, it should be noted that unless otherwise clearly specified and defined, terms such as "installation", "provided with", "sheathed / connected", "connection", etc. should be understood in a broad sense. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection. It can be directly connected or indirectly connected through an intermediate medium. It can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0039] Embodiment 1 This embodiment provides an axial detection tube for correcting the influence of the flow field uniformity of a subsonic wind tunnel, which includes a nose cone 1, a measurement section 2, a connection section 3 for connecting with a test adapter, and a pressure measurement nozzle for connecting with a pressure measurement tube. As shown in the figure, the nose cone 1, the measurement section 2, and the connection section 3 are connected in sequence as a whole and are coaxially arranged. The nose cone 1 of the axial detection tube is located in the test section of the wind tunnel, and the inside of the axial detection tube is a hollow through hole for arranging the pressure measurement tube. Among them, the nose cone 1 is overall conical, the outer shape of the nose cone 1 is arc-shaped, and the rear end of the nose cone 1 is smoothly connected to the measurement section 2; the measurement section 2 is overall round tubular.

[0040] The connection section 3 includes a first connection part 8 and a second connection part 9; as shown in the figure, the cross-section of the first connection part 8 along the direction perpendicular to its axis is overall frustum-shaped, and the cross-section of the second connection part 9 along the direction perpendicular to its axis is overall inverted frustum-shaped. The outer diameter of the large end of the first connection part 8 is larger than the outer diameter of the large end of the second connection part 9, and the large end of the first connection part 8 is connected to the large end of the second connection part 9. The connection section 3 is smoothly connected to the measurement section 2 through the first connection part 8, and the first connection part 8 can play a role in rectifying. Further, a reference platform 6 is provided on the outer surface of the first connection part 8, and the reference platform 6 is located at one end of the first connection part 8 close to the second connection part 9. The reference platform 6 can be used for installing and leveling the axial detection tube in the pitch and roll directions. The reference platform 6 is parallel to the central axis of the axial detection tube. In this structure, the reference platform 6 is used for installing and leveling the axial detection tube in the pitch and roll directions, which can ensure the installation attitude of the device, facilitate inspection and maintenance, reduce the installation errors of different personnel and at different times, and improve the accuracy.

[0041] The nose cone 1 is provided with a total pressure hole 7 and a first static pressure hole 4. The total pressure hole 7 penetrates through the nose cone 1 and is located on the central axis of the axial detection tube. The first static pressure hole 4 is arranged along the tangent direction of the conical surface. The first static pressure hole 4 can be used to calibrate the pneumatic deformation. The plane where the reference platform 6 is located relative to the rolling direction of the axial detection tube is defined as 0°. There are two first static pressure holes 4, and the measuring section 2 is provided with 2N second static pressure holes 5, where N is a natural number and N≥1. The first static pressure holes 4 and the second static pressure holes 5 are correspondingly arranged on the straight line at the 0° and 180° positions of the measuring section 2 relative to the plane where the reference platform 6 is located. Or there are four first static pressure holes 4, and the measuring section 2 is provided with 4N second static pressure holes 5, where N is a natural number and N≥1. The first static pressure holes 4 and the second static pressure holes 5 are correspondingly arranged on the straight lines at the 0°, 90°, 180°, and 270° positions of the measuring section 2 relative to the plane where the reference platform 6 is located.

[0042] The center point of the first static pressure hole 4 and the center point of the corresponding second static pressure hole 5 are located on the same plane, and the first static pressure holes 4 and the second static pressure holes 5 are evenly distributed along the central axis of the axial detection tube.

[0043] The total pressure hole 7, the first static pressure hole 4, and the second static pressure hole 5 are respectively guiding cones with a set ratio, and the guiding cones can ensure vertical installation. The total pressure hole 7 is installed in cooperation with the pressure measuring nozzle, and the central axis of the total pressure hole 7 coincides with the central axis of the corresponding pressure measuring nozzle. The first static pressure hole 4 is installed in cooperation with the pressure measuring nozzle, and the central axis of the first static pressure hole 4 coincides with the central axis of the corresponding pressure measuring nozzle. The second static pressure hole 5 is installed in cooperation with the pressure measuring nozzle, and the central axis of the second static pressure hole 5 coincides with the central axis of the corresponding pressure measuring nozzle. In a specific example, the pressure measuring nozzle is connected to the pressure measuring tube and then installed in cooperation with the measuring section 2. The pressure measuring hole has a 1:50 guiding cone to ensure the vertical installation of the pressure measuring hole. With this structure, wire rope traction can be avoided, and the influence of the traction rope on the wind tunnel airflow can be reduced.

[0044] Furthermore, this embodiment provides the application of the aforementioned axial detection tube, which includes the following steps.

[0045] S1. Install the axial detection tube in the wind tunnel that needs to be calibrated for the flow field through the test adapter, and use the reference platform 6 provided in the connection section 3 to level the pitch and roll postures of the axial detection tube.

[0046] S2. After connecting the total pressure measurement point of the total pressure hole 7, the static pressure measurement point of the first static pressure hole 4, and the static pressure measurement point of the second static pressure hole 5 to the pressure sensors respectively, conduct the test to obtain the total pressure of the airflow in the test section and the static pressures of each measurement point.

[0047] S3. Calculate the Mach number of each measurement point in the measuring section 2 using the isentropic relationship as the core flow Mach number of the flow field in the test section.

[0048] S4. Use standard methods to calculate the core flow average Mach number, axial distribution root mean square deviation, and axial gradient as input for wind tunnel operation, flow field uniformity assessment, and float resistance correction of model test data.

[0049] The total pressure measuring point is a pressure measuring hole located at the theoretical tip of the head cone 1. The head is truncated and chamfered at 90° to expand the insensitive angle of the total pressure measuring point to the airflow direction.

[0050] The total airflow pressure in the test section refers to the pressure when the airflow in the test section is entropically stagnated to zero velocity. It is used as the input condition for calculating the Mach number at each measuring point in the axial detection tube measuring section 2. Due to the friction of the airflow, the total airflow pressure in the test section is slightly lower than the total pressure in the stable section.

[0051] The nose cone 1 is a gradually expanding diameter component provided at the front of the axial detection tube to reduce the influence of the tube body on the airflow. In order to reduce the flow field disturbance caused by the surface discontinuity at the connection between the nose cone 1 and the measuring section 2, an arc shape is adopted, and a smooth transition is made at the connection with the measuring section 2.

[0052] The second static pressure holes 5 refer to the static pressure measuring points distributed on the measuring section 2 of the axial detection tube, which are divided into two rows, upper and lower, or four rows, upper, lower, left and right, along the axial direction of the axial detection tube. The spacing and diameter of each measuring point can be determined according to the caliber of the wind tunnel test section.

[0053] The pressure measuring nozzle is a pressure sensing device located on the body of the axial detection tube. It is cylindrical in shape, with its upper surface flush with the outer surface of the axial detection tube and its lower surface flush with the inner wall of the axial detection tube. A pressure measuring tube is arranged in the middle to introduce the pressure of the measuring section 2 of the axial detection tube into the interior of the tube body and lead it out to the pressure sensor through the pressure measuring tube.

[0054] The test adapter refers to the adapter mechanism between the support rod and the middle bracket of the wind tunnel, which ensures that the model and the balance are installed in the center of the test section; the test adapter can be a straight head, or the test adapter can also be a double-axis joint with a pre-bias angle to increase the model posture.

[0055] Attitude leveling refers to the use of the wind tunnel scimitar mechanism and the rolling mechanism to level the installation attitude of the axial detection tube to ensure that the axis of the axial detection tube coincides with the axis of the test section. According to the subsonic wind tunnel calibration requirements, the absolute value of the attitude angle in the pitch and roll directions should be less than 0.03°.

[0056] The test refers to the flow field calibration test, that is, the wind tunnel constant total temperature, total pressure and variable Mach number test. After each step flow field is stable, the total pressure at the head of the axial detection tube and the static pressure value of the measuring section 2 are measured by the pressure sensor.

[0057] The isentropic relationship assumes that the working medium in the test section is an ideal gas, the internal energy depends only on temperature, and the temperature remains constant during the short time process of test acquisition, that is, it meets the requirements of an adiabatic and reversible thermodynamic process. At this time, the simplified relationship between the total pressure and static pressure of the air flow can be used to solve the Mach number of the measuring point.

[0058] The standard method refers to the method of calculating the flow field uniformity index using the core flow Mach number distribution in accordance with the "Requirements for the Flow Field Quality of Low-Speed Wind Tunnels and High-Speed Wind Tunnels" (GJB 1179A-2012).

[0059] Float resistance correction refers to calculating the additional resistance caused by the axial static pressure gradient in the test section using data such as the axial gradient of Mach number, model volume or cross-sectional area distribution, and correcting the test results to improve the accuracy of the data.

[0060] Furthermore, a wedge-shaped hole 10 for connecting with a test adapter is provided on the second connecting portion 9, or a thread 11 for connecting with a flange is provided on the second connecting portion 9; the test adapter is one of a straight adapter and a double-rotating shaft adapter.

[0061] Taking the flow field calibration of a 2.4-meter transonic wind tunnel as an example, the usage method of the axial detection tube involved in the present invention is described, and the specific implementation steps are as follows.

[0062] First step: Install the test adapter to be calibrated on the middle bracket of the 2.4-meter transonic wind tunnel. For this wind tunnel, the commonly used test adapters are divided into two sets, namely a straight adapter and a double-rotating shaft adapter, and the installation methods are the same. In this embodiment, a straight adapter is used, as shown by the solid line part in Figure 1 the figure.

[0063] Second step: Install the axial detection tube of this embodiment on the test adapter. In this embodiment, it is connected and tightened through the conical surface of the axial detection tube and the front end of the test adapter. Furthermore, a flange is also provided on the connecting section 3 of the axial detection tube; for a specific test adapter, the flange tightening method can be used for installation.

[0064] Third step: Use the reference platform 6 to measure the pitch angle and roll angle of the axial detection tube, and adjust the wind tunnel vane and roll mechanism to make the absolute angle less than 0.03°.

[0065] Fourth step: Lead out the steel pipes of the total pressure measuring point at the head of the axial detection tube and the static pressure measuring point in the measuring section 2 to the middle bracket, and connect them to the pressure sensor.

[0066] Fifth step: Start the test, and the relevant parameters are as follows: the state is a total pressure of 130 kPa, and data of each pressure measuring point are collected at Mach numbers of 0.60, 0.70, 0.80, and 0.90 respectively.

[0067] Compared with the total pressure in the stable section, the measured results of the total pressure measurement points in the test section are 100 - 200 Pa lower, as shown in Table 1 below; this indicates that it will have an impact of about 0.001 - 0.002 on the calculation of the Mach number in the test section.

[0068] Table 1 Test measurement data

[0069] Step 6: Calculate the Mach number distribution of the core flow field in the test section using the measured total pressure and static pressure values.

[0070] Figure 4 A comparison chart of the measurement results between the axial detection tube of the present application and the traditional axial detection tube is given. From Figure 4 it can be seen that: the axial detection tube of the present application can accurately obtain the influence of the test adapter on the flow field uniformity, and the obtained indexes such as the axial gradient of the Mach number and the average Mach number are closer to the real test state.

[0071] Step 7: Calculate indexes such as the average Mach number, root mean square deviation, and axial gradient of the core flow in the test section according to the requirements of the national military standard.

[0072] Step 8: Compare with the measurement results of the traditional axial detection tube and analyze the differences in the correction of the floating drag of the airliner.

[0073] Figure 5 A comparison chart of the calculation results between the present application and the traditional axial detection tube is given; from Figure 5 it can be seen that: the data measured using the present application is more accurate.

[0074] The above scheme is only an illustration of a preferred example, but is not limited thereto. When implementing the present invention, appropriate substitutions and / or modifications can be made according to the needs of the user.

[0075] The number of devices and the processing scale described here are used to simplify the description of the present invention. The application, modification, and variation of the present invention are obvious to those skilled in the art.

[0076] Although the embodiments of the present invention have been disclosed above, it is not limited to the applications listed in the specification and the embodiments. It can be fully applied to various fields suitable for the present invention. For those familiar with the field, additional modifications can be easily achieved. Therefore, without departing from the general concept defined by the claims and the equivalent scope, the present invention is not limited to the specific details and the illustrated examples here.

[0077] The present invention is not limited to the foregoing specific embodiments. The present invention extends to any new feature or any new combination disclosed in this specification, as well as any new method or process step or any new combination disclosed.

Claims

1. An axial detection tube for correcting the influence of the flow field uniformity of a subsonic wind tunnel, characterized in that, It includes a nose cone, a measurement section, a connection section for connecting with a test adapter, and a pressure measuring nozzle for connecting with a pressure measuring tube. The nose cone, the measurement section, and the connection section are connected in sequence as a whole and are coaxially arranged; The nose cone is overall conical, the outer shape of the nose cone is arc-shaped, and the rear end of the nose cone is smoothly transitioned with the measurement section; The measurement section is overall circular tubular; The connection section includes a first connection part and a second connection part. The cross-section of the first connection part perpendicular to its axis is overall frustum-shaped, and the cross-section of the second connection part perpendicular to its axis is overall inverted frustum-shaped. The outer diameter of the large end of the first connection part is greater than the outer diameter of the large end of the second connection part, and the large end of the first connection part is connected to the large end of the second connection part; The connection section is smoothly transitioned with the measurement section through the first connection part, and the first connection part can play a role in flow rectification. A reference platform is arranged on the outer surface of the first connection part close to the second connection part, and the reference platform can be used for the installation leveling of the axial detection tube in the pitch and roll directions. The reference platform is parallel to the central axis of the axial detection tube; The inside of the axial detection tube is a hollow through hole for arranging the pressure measuring tube; The nose cone is provided with a total pressure hole and a first static pressure hole. The total pressure hole penetrates through the nose cone. The total pressure hole is located on the central axis of the axial detection tube. The central axis of the first static pressure hole is perpendicular to the tangent direction of the conical surface of the nose cone; Taking the plane where the reference platform is located relative to the roll direction of the axial detection tube as 0°; There are two first static pressure holes. The measurement section is provided with 2N second static pressure holes, where N is a natural number and N≥1. The first static pressure holes and the second static pressure holes are correspondingly arranged on the straight lines at the 0° and 180° positions of the measurement section relative to the plane where the reference platform is located; Or there are four first static pressure holes. The measurement section is provided with 4N second static pressure holes, where N is a natural number and N≥1. The first static pressure holes and the second static pressure holes are correspondingly arranged on the straight lines at the 0°, 90°, 180°, and 270° positions of the measurement section relative to the plane where the reference platform is located; The center points of the first static pressure holes and the center points of the corresponding second static pressure holes are located in the same plane. The first static pressure holes and the second static pressure holes are evenly distributed along the central axis of the axial detection tube; The nose cone of the axial detection tube is located in the wind tunnel test section; The total pressure hole, the first static pressure hole, and the second static pressure hole are respectively guiding cones with a set ratio, and the guiding cones can ensure vertical installation. The pressure measuring nozzle is installed in cooperation with the total pressure hole, and the central axis of the total pressure hole coincides with the central axis of the corresponding pressure measuring nozzle. The pressure measuring nozzle is installed in cooperation with the first static pressure hole, and the central axis of the first static pressure hole coincides with the central axis of the corresponding pressure measuring nozzle. The pressure measuring nozzle is installed in cooperation with the second static pressure hole, and the central axis of the second static pressure hole coincides with the central axis of the corresponding pressure measuring nozzle.

2. The axial detection tube according to claim 1, characterized in that, The total pressure hole is a pressure measuring hole located at the theoretical tip of the nose cone. The head of the nose cone is truncated and provided with a 90° chamfer to expand the insensitive angle of the total pressure measurement point of the total pressure hole to the air flow direction.

3. The axial detection tube according to claim 1, characterized in that, The test adapter is one of a straight adapter and a double-rotating shaft adapter.

4. The axial detection tube according to any one of claims 1 to 3, characterized in that, The pressure measuring nozzle is a pressure sensing device located on the body of the axial detection tube. It is cylindrical, with its upper surface flush with the outer surface of the axial detection tube and its lower surface flush with the inner wall of the axial detection tube. A pressure measuring tube is arranged in the middle to introduce the pressure of the measurement section of the axial detection tube into the interior of the pressure measuring tube and lead it out to the pressure sensor through the pressure measuring tube.

5. Use of the axial detection tube according to any one of claims 1 to 4, characterized in that It includes the following steps: S1. Install the axial detection tube in the wind tunnel that needs to be calibrated for the flow field through a test adapter, and use the reference platform set in the connection section to level the pitch and roll of the axial detection tube. S2. After connecting the total pressure measuring point of the total pressure hole, the static pressure measuring points of the first static pressure hole and the second static pressure hole to the pressure sensors respectively, conduct the test to obtain the total pressure of the airflow in the test section and the static pressures at each measuring point. S3. Calculate the Mach number at each measuring point in the measurement section using the isentropic relationship as the core flow Mach number of the test section flow field. S4. Use the standard method to calculate the core flow average Mach number, the root mean square deviation of the axial distribution, and the axial gradient as the input for wind tunnel operation, flow field uniformity evaluation, and floating resistance correction of model test data.

6. The application according to claim 5, characterized in that, The operation of step S1 is as follows: S1.1 Connect the test adapter to be calibrated to the middle bracket of the wind tunnel. S1.2 Connect the axial detection tube to the test adapter. S1.3 Measure the pitch angle and roll angle of the axial detection tube using the reference platform, and adjust the wind tunnel vane and roll mechanism so that the absolute angles of the pitch angle and roll angle are less than 0.03° respectively. The total pressure measuring point is a pressure measuring hole located at the theoretical tip of the nose cone. The head is truncated and provided with a 90° chamfer to increase the insensitive angle of the total pressure measuring point to the airflow direction.

7. The application according to claim 6, wherein In step S1.2, it is connected and tightened through the conical surface of the axial detection tube and the front end of the test adapter. Or a flange is provided on the connection section of the axial detection tube, and the axial detection tube is connected to the test adapter through the flange.

8. The application according to claim 5, wherein The test adapter refers to the transfer mechanism between the strut and the middle bracket of the wind tunnel to ensure that the model and the balance are installed at the center of the test section; the test adapter is a straight joint, or the test adapter is a double-rotating joint with a pre-deviation angle to increase the model attitude.

9. The application according to claim 5, characterized in that, The attitude leveling refers to using the wind tunnel vane mechanism and roll mechanism to level the installation attitude of the axial detection tube to ensure that the axis of the axial detection tube coincides with the axis of the test section.

10. The application according to claim 5, wherein The floating resistance correction refers to calculating the additional resistance caused by the axial static pressure gradient in the test section using data such as the axial gradient of the Mach number, the model volume or cross-sectional area distribution, etc., and correcting the test results to improve the accuracy of the data.

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