Stepped plug cone flow measuring nozzle and method

Abstract

The invention discloses a stepped plug cone flow measuring nozzle and method, and relates to the technical field of wind tunnel tests. A conventional air inlet channel flow measuring nozzle is in a Laval nozzle form with a fixed structure, when the flow of an air inlet channel changes in a wind tunnel test, flow measuring nozzles with different inner diameters need to be frequently replaced in the test process, and the test efficiency is greatly reduced. The device comprises a Laval nozzle, a front supporting rib, a driving lead screw, a stepped plug cone, a guide rail, a speed reducer, a rear supporting rib, a servo motor, a rectification protection cover, pressure and temperature acquisition equipment, an industrial personal computer and a motor driver, wherein the stepped plug cone is in a multi-stage cylindrical stepped shape. According to the invention, the throat area of the Laval nozzle can be continuously changed in a stepped manner under the condition that the wind tunnel test process is uninterrupted, and the wide-range variable flow of the air inlet channel can be accurately measured. The invention adopts innovative integration and improvement on the traditional Laval nozzle, and has the advantages of wide applicability, convenience in use, reliability and durability.

Description

Technical Field

[0001] This invention relates to the field of wind tunnel testing technology, and in particular to a stepped plug cone flow measurement nozzle and method. Background Technology

[0002] In wind tunnel testing, conventional inlet flow measurement nozzles are fixed-structure Laval nozzles, meaning the minimum flow area is fixed. When the inlet flow rate changes during wind tunnel testing, to ensure accurate flow measurement, the velocity coefficient q(λ) at the minimum cross-section of the flow measurement nozzle must be greater than 0.85 and as close as possible to 1. This requires the airflow Mach number Ma in the wind tunnel test section to be greater than 0.6 and as close as possible to 1, forming a sonic cross-section. This necessitates frequently changing flow measurement nozzles with different inner diameters during the test, which greatly reduces test efficiency. Alternatively, if the same flow measurement nozzle is used during the test, the flow velocity inside the nozzle will be very low when the flow rate becomes smaller, with q(λ) being much less than 0.85, leading to increased flow measurement error. Summary of the Invention

[0003] The purpose of this invention is to solve the problem that conventional intake flow measurement nozzles are of the fixed structure Laval nozzle type, which requires frequent replacement of flow measurement nozzles with different inner diameters when the intake flow changes during wind tunnel testing, thus greatly reducing the test efficiency. This invention provides a stepped plug cone flow measurement nozzle and method, which enables accurate measurement of intake flow even when it varies over a wide range.

[0004] To achieve the above objectives, the present invention provides the following technical solution: A stepped plug cone flow measurement nozzle includes a Laval nozzle, a front support rib, a drive screw, a stepped plug cone, a guide rail, a reducer, a rear support rib, a servo motor, a rectifier protective cover, pressure and temperature acquisition equipment, an industrial control computer, and a motor driver. The front support rib is installed on the inlet side of the Laval nozzle. The Laval nozzle is connected to total pressure and total temperature measuring rakes via a front flange. The total pressure and total temperature measuring rakes are located in front of the front support rib. The rear support rib is installed at the rear of the expansion section of the Laval nozzle. A rectifier protective cover is installed on the rear support rib. The servo motor is installed inside the rectifier protective cover. The output end of the servo motor is connected to the rear end of the drive screw via the reducer. The drive screw is coaxially mounted with the Laval nozzle. The front end of the drive screw is connected to the central bearing hole of the front support rib. A stepped plug cone is mounted on the drive screw, and a guide rail groove is provided on the stepped plug cone. The front end of the guide rail is set in the guide rail groove, and the rear end of the guide rail is fixedly connected to the rectifier protective cover. A static pressure measuring point is installed on the straight section of the Laval nozzle. The pressure and temperature acquisition device is connected to the total pressure and total temperature measuring rake through a first cable. The pressure and temperature acquisition device is connected to the static pressure measuring point through a static pressure hose. The motor driver is connected to the servo motor through a second cable. The industrial control computer is connected to the pressure and temperature acquisition device and the motor driver respectively.

[0005] Furthermore, the front flange, inner contraction section, straight section, expansion section, rear flange section, and rear pipe of the Laval nozzle are connected in sequence.

[0006] Furthermore, the front support rib is in the shape of a cross or a human figure.

[0007] Furthermore, the stepped plug cone is a multi-stage cylindrical stepped shape, and the different stepped cylinders of the stepped plug cone and the straight section of the Laval nozzle form measurement areas with different annular flow areas.

[0008] Furthermore, a lead wire groove is provided on the rear support rib, and the second cable passes through the lead wire groove.

[0009] A method for measuring flow rate using a stepped plug cone, comprising the following steps: S1. Design the number of steps and the diameter of each step of the stepped plug cone according to the test flow range, and install the stepped plug cone onto the drive screw. S2. During the inlet wind tunnel test, when the flow rate entering the flow measurement nozzle changes from high to low, the total pressure measured by the total pressure and total temperature measuring rake, and the static pressure measured by the static pressure measuring point of the Laval nozzle, are transmitted to the industrial control computer to calculate the velocity coefficient q(λ). The relationship between q(λ) and the total pressure and static pressure is as follows: ; If q(λ) is less than the preset value range of 0.85~1, the industrial control computer sends a signal to the motor driver to drive the servo motor to move the stepped plug cone forward quantitatively, reduce the airflow area of ​​the measurement area, and increase q(λ) to the target value range, thereby completing the measurement.

[0010] The beneficial effects of this invention: 1. This invention can continuously and stepwise change the throat area of ​​the Laval nozzle during wind tunnel testing without interruption, and can accurately measure the flow rate over a wide range of inlet variations.

[0011] 2. This invention adopts an innovative integration and improvement of the traditional Laval nozzle, which has wide applicability, is convenient to use, and is reliable and durable. Attached Figure Description

[0012] Figure 1 This is a schematic diagram of a stepped plug cone flow measurement nozzle; Figure 2 This is a schematic diagram of the minimum flow rate of a stepped plug cone flow measurement nozzle; Figure 3 This is a schematic diagram showing the maximum flow rate of a stepped plug cone flow measurement nozzle. Figure 4 This is a control block diagram for a stepped plug cone flow measurement nozzle.

[0013] In the diagram, 1-front support rib; 2-drive screw; 3-measuring area; 4-stepped plug cone; 5-guide rail; 6-reducer; 7-rear support rib; 8-servo motor; 9-total pressure and total temperature measuring rake; 10-front flange; 11-inner contraction section; 12-static pressure measuring point; 13-straight section; 14-expansion section; 15-lead wire groove; 16-rear flange section; 17-rectifier protection cover; 18-rear pipe; 19-first cable; 20-static pressure hose; 21-second cable; 22-pressure and temperature acquisition equipment; 23-industrial control computer; 24-motor driver. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0015] Example 1: Combination Figures 1-4This embodiment describes a stepped plug cone flow measurement nozzle, including a Laval nozzle, a front support rib 1, a drive screw 2, a stepped plug cone 4, a guide rail 5, a reducer 6, a rear support rib 7, a servo motor 8, a rectifier protection cover 17, a pressure and temperature acquisition device 22, an industrial control computer 23, and a motor driver 24. The front support rib 1 is installed on the inlet side of the Laval nozzle. The Laval nozzle is connected to a total pressure and total temperature measuring rake 9 via a front flange 10. The total pressure and total temperature measuring rake 9 is located in front of the front support rib 1. The rear support rib 7 is installed at the rear of the expansion section 14 of the Laval nozzle. A rectifier protection cover 17 is installed on the rear support rib 7. The servo motor 8 is installed inside the rectifier protection cover 17. The output end of the servo motor 8 is connected to the drive screw via the reducer 6. The rear end of the drive screw 2 is connected to the Laval nozzle. The front end of the drive screw 2 is connected to the central bearing hole of the front support rib 1. A stepped plug cone 4 is installed on the drive screw 2. A guide rail groove is opened on the stepped plug cone 4. The front end of the guide rail 5 is set in the guide rail groove. The rear end of the guide rail 5 is fixedly connected to the flow protection cover 17. A static pressure measuring point 12 is installed on the straight section 13 of the Laval nozzle. The pressure and temperature acquisition device 22 is connected to the total pressure and total temperature measuring rake 9 through the first cable 19. The pressure and temperature acquisition device 22 is connected to the static pressure measuring point 12 through the static pressure hose 20. The motor driver 24 is connected to the servo motor 8 through the second cable 21. The industrial control computer 23 is connected to the pressure and temperature acquisition device 22 and the motor driver 24 respectively.

[0016] Specifically, the front flange 10, inner contraction section 11, straight section 13, expansion section 14, rear flange section 16, and rear pipe 18 of the Laval nozzle are connected in sequence.

[0017] Specifically, the front support rib 1 is in the shape of a cross or a V-shape, with a symmetrical airfoil guide design. The outer side is fixedly connected to the inlet end of the Laval nozzle, and the center of the front support rib 1 is a bearing hole connected to the drive screw 2.

[0018] Specifically, the drive screw 2 carries the stepped piston cone 4 and provides the driving force for the stepped piston cone 4 to move back and forth. The rear end of the drive screw 2 is connected to the servo motor 8 through the reducer 6.

[0019] Specifically, the stepped plug cone 4 is a multi-stage cylindrical stepped shape, with its front and rear end faces designed for flow guidance and drag reduction. The different stepped cylinders of the stepped plug cone 4 and the straight section 13 of the Laval nozzle form measurement areas 3 with different annular flow areas, which are used to match the wide range of flow variations in the intake. When the intake flow is large, the stepped plug cone 4 moves backward to form a large annular flow area; when the intake flow is small, the stepped plug cone 4 moves forward to form a small annular flow area, ensuring that the velocity coefficient q(λ) is greater than 0.85 and as close as possible to 1 under all the above conditions.

[0020] Specifically, the number of steps and the diameter of each step of the stepped plug cone 4 can be designed according to the test flow requirements.

[0021] Specifically, the guide rail 5 guides the stepped plug cone 4 to move back and forth along the axial direction without rotating. Its front end is connected to the inside of the stepped plug cone 4, and its rear end is fixedly connected to the rectifier protection cover 17.

[0022] Specifically, the servo motor 8 is the power source. The torque is increased by the reducer and then transmitted to the stepped piston cone 4 through the drive screw 2, converting the rotational motion of the servo motor 8 into the linear motion of the stepped piston cone 4.

[0023] Specifically, the rear support rib 7 provides support and has a lead wire groove 15 inside. Its shape is a symmetrical airfoil guide design. The outer end is connected to the vicinity of the Laval nozzle outlet, and the inner end is connected to the rectifier shield 17.

[0024] Specifically, the function of the rectifier protective cover 17 is to reduce airflow resistance, protect the servo motor 8, and fix the rear support rib 7. It is an elliptical guide type, divided into front and rear parts. The rear part can be removed separately. When the rear part is removed, the servo motor 8 can be disassembled or maintained.

[0025] Example 2: Combination Figures 1-4 This embodiment describes a method for measuring the flow rate of a stepped plug cone. The steps of the method are as follows: S1. Design the number of steps and the diameter of each step of the stepped plug cone 4 according to the test flow range, and install the processed stepped plug cone 4 onto the drive screw 2.

[0026] S2. During the inlet wind tunnel test, when the flow rate entering the flow measurement nozzle changes from large to small, the total pressure measured by the total pressure and total temperature measuring rake 9 and the static pressure measured by the static pressure measuring point 12 of the Laval nozzle are transmitted to the industrial control computer 23 to calculate the velocity coefficient q(λ). The relationship between q(λ) and the total pressure and static pressure is as follows: ; If q(λ) is less than the preset value range of 0.85~1, the industrial control computer 23 sends a signal to the motor driver 24 to drive the servo motor 8 to move the stepped plug cone 4 forward quantitatively, reduce the airflow area of ​​the measurement area 3, and increase q(λ) to the target value range, thereby completing the measurement.

[0027] The present invention has been described in detail above. However, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, any modifications or improvements that do not depart from the spirit of the present invention are within the scope of protection of the present invention.

Claims

1. A stepped plug cone flow measuring nozzle, characterized in that... The system includes a Laval nozzle, a front support rib (1), a drive screw (2), a stepped plug cone (4), a guide rail (5), a reducer (6), a rear support rib (7), a servo motor (8), a rectifier protection cover (17), a pressure and temperature acquisition device (22), an industrial control computer (23), and a motor driver (24). The front support rib (1) is installed on the inlet side of the Laval nozzle. The Laval nozzle is connected to a total pressure and total temperature measuring rake (9) via a front flange (10). The total pressure and total temperature measuring rake (9) is located in front of the front support rib (1). The rear support rib (7) is installed at the rear of the expansion section (14) of the Laval nozzle. A rectifier protection cover (17) is installed on the rear support rib (7). The servo motor (8) is installed inside the rectifier protection cover (17). The output end of the servo motor (8) is connected to the rear end of the drive screw (2) via a reducer (6). (2) The drive screw (2) is coaxially set with the Laval nozzle. The front end of the drive screw (2) is connected to the center bearing hole of the front support rib (1). A stepped plug cone (4) is installed on the drive screw (2). A guide rail groove is opened on the stepped plug cone (4). The front end of the guide rail (5) is set in the guide rail groove. The rear end of the guide rail (5) is fixedly connected to the rectifier protection cover (17). A static pressure measuring point (12) is installed on the straight section (13) of the Laval nozzle. The pressure and temperature acquisition device (22) is connected to the total pressure and total temperature measuring rake (9) through the first cable (19). The pressure and temperature acquisition device (22) is connected to the static pressure measuring point (12) through the static pressure hose (20). The motor driver (24) is connected to the servo motor (8) through the second cable (21). The industrial control computer (23) is connected to the pressure and temperature acquisition device (22) and the motor driver (24) respectively.

2. The stepped plug cone flow measuring nozzle according to claim 1, characterized in that... The Laval nozzle consists of a front flange (10), an inner contraction section (11), a straight section (13), an expansion section (14), a rear flange section (16), and a rear pipe (18) connected in sequence.

3. A stepped plug cone flow measuring nozzle according to claim 1, characterized in that... The front support rib (1) is in the shape of a "+" or "human".

4. A stepped plug cone flow measuring nozzle according to claim 1, characterized in that... The stepped plug cone (4) is a multi-stage cylindrical stepped shape. Different stepped cylinders of the stepped plug cone (4) and the straight section (13) of the Laval nozzle form measurement areas (3) with different annular flow areas.

5. A stepped plug cone flow measuring nozzle according to claim 1, characterized in that... The rear support rib (7) is provided with a lead wire groove (15), and the second cable (21) is passed through the lead wire groove (15).

6. A method for measuring flow rate of a stepped plug cone, characterized in that... It relies on a stepped plug cone flow measuring nozzle as described in any one of claims 1-5, and the method steps are as follows: S1. Design the number of steps and the diameter of each step of the stepped plug cone (4) according to the test flow range, and install the stepped plug cone (4) onto the drive screw (2). S2. During the inlet wind tunnel test, when the flow rate entering the flow measurement nozzle changes from large to small, the total pressure measured by the total pressure and total temperature measuring rake (9) and the static pressure measured by the static pressure measuring point (12) of the Laval nozzle are transmitted to the industrial control computer (23) to calculate the velocity coefficient q(λ). The relationship between q(λ) and the total pressure and static pressure is as follows: ； If q(λ) is less than the preset value range of 0.85~1, the industrial control computer (23) sends a signal to the motor driver (24) to drive the servo motor (8) to move the stepped plug cone (4) forward quantitatively, reduce the airflow area of ​​the measurement area (3), and increase q(λ) to the target value range, thereby completing the measurement.

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