Calibration device and method for liquid rocket engine nozzle airflow field PIV test

By designing a calibration device for the PIV test of the nozzle air flow field of the liquid rocket engine, the problem of cumbersome calibration process and low accuracy in the prior art is solved, and an efficient and accurate calibration process is achieved, ensuring the accuracy of the test data.

CN119738118APending Publication Date: 2025-04-01BEIJING AEROSPACE PROPULSION INST
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Patent Information

Application Number
CN202411821397.0
Authority / Receiving Office
CN · China
Patent Type
Applications(China)
Current Assignee / Owner
Filing Date
2024-12-11
Publication Date
2025-04-01

AI Technical Summary

Technical Problem

In the prior art, in the PIV test of the nozzle air flow field of the liquid rocket engine, the calibration process is cumbersome and complex, and the calibration accuracy is low, which affects the accuracy of the test data.

Method used

A calibration device including a bench, a screw bolt, an elastic fixture, a calibration code disc, a level and a right angle meter is designed, through which the camera focal plane, a laser irradiation plane and a product flow field are accurately positioned.

Benefits of technology

It significantly improves calibration efficiency and accuracy, simplifies the calibration process, and ensures the accuracy of test data.

✦ Generated by Eureka AI based on patent content.

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Abstract

The invention relates to a calibration device and method for a liquid rocket engine nozzle airflow field PIV test. The device comprises a rack, a screw-in bolt, an elastic clamp, a calibration code disc, a gradienter and a right angle instrument. The bolt is screwed in to realize the clamping function of the elastic clamp on the spray pipe, the calibration device is adjusted to a horizontal state through the gradienter, and the relative positions of the device and the spray pipe are fixed; the calibration code disc moves through the guide rail to coincide with the jet pipe airflow scene, and the position of the code disc is determined through scale marks on the side face of the rack; the right angle instrument realizes vertical position visualization and completes relative position positioning of the camera and the laser generator; the elastic clamp has a detachable and replaceable function, and is suitable for clamping and fixing products of different structures through technological design.
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Description

Technical Field

[0001] The invention relates to an auxiliary calibration device for a liquid rocket engine nozzle airflow field PIV test, belonging to the technical field of fluid test. Background Art

[0002] Image calibration is a key step in particle image velocimetry (PIV) technology, which directly affects the data accuracy of post-test processing, and further affects the judgment of the axial length and circumferential uniformity of the nozzle air film. Through the process design of the calibration device, the calibration process is simplified and the calibration accuracy is significantly improved.

[0003] During the refinement test of the supersonic cooling film of the engine nozzle, adjust the position of the laser generator to achieve the overlap of the laser irradiation surface and the product flow field. Adjust the camera angle and the position of the camera focal plane to complete the overlap of the camera focal plane and the product flow field. After completing the overlap of the three surfaces (laser irradiation surface, product flow field and camera focal plane), adjust the position of the calibration code disk so that its calibration surface coincides with the above three surfaces, and complete the size calibration within the measurement surface through the PIV system. In this process, personnel are required to wear laser goggles to enter the site, and multiple people operate the position and angle of the laser, camera, and code disk at the same time. Since the relative positions of each device are unclear, it is necessary to judge by the naked eye and repeatedly compare the sample photos, and iteratively adjust the position of the device to obtain a high-precision calibration result. The operation process is cumbersome and complicated, and the calibration accuracy is low. Summary of the invention

[0004] The technical problem solved by the present invention is: to overcome the deficiencies of the prior art, by inventing an auxiliary calibration device for a liquid rocket engine nozzle airflow field PIV test, to visualize the calibration position, to simplify the calibration process, and to significantly improve the calibration efficiency and accuracy.

[0005] The solution to the technical problem of the present invention is: a calibration device for liquid rocket engine nozzle airflow field PIV test, the device includes a bench, screw-in bolts, an elastic clamp, a calibration code disk, a level, and a right angle meter;

[0006] The stand is N-shaped and includes a horizontal beam and two vertical legs. The vertical legs are located at both ends of the horizontal beam and are respectively marked as the left leg and the right leg, which are used to support the horizontal beam. A horizontal groove is provided above the horizontal beam, and guide rails are provided on both sides of the horizontal groove. The side of the horizontal beam is provided with scale lines in the horizontal direction;

[0007] The elastic clamp comprises a left clamping part and a right clamping part, wherein the left clamping part is mounted on the left supporting leg, and the right clamping part is fixed on the right supporting leg, and the left clamping part and the right clamping part cooperate with each other to clamp the nozzle to be tested;

[0008] The screw-in bolt is installed on the left leg to drive the left arm to move, and the screw-in length of the left arm relative to the left leg is recorded through the built-in scale line;

[0009] The calibration code disk can be installed in conjunction with the guide rail and move along the guide rail to calibrate the vertical position of the nozzle airflow field and the focal length of the camera;

[0010] A level, installed on the upper surface of the platform beam, is used to adjust the platform to a horizontal state;

[0011] The right angle meter can be installed in conjunction with the guide rail and move along the guide rail to calibrate the relative position of the camera and the laser generator.

[0012] Preferably, the scale lines on the side of the crossbeam and the scale lines zero position on the screw-in bolt correspond to the same vertical reference plane, and the screw-in length of the screw-in bolt is the relative position distance between the nozzle airflow field and the calibration code disk.

[0013] Preferably, in the elastic clamp, the left clamping component includes a left clamping arm and a left clamp, and the right clamping component includes a right clamping arm and a right clamp;

[0014] One end of the left clamping arm is connected to the left clamp through a rotating shaft, and the other end is marked as the driving end, which is inserted into the through hole of the left leg in the horizontal direction. The left clamp and the right clamp are contoured to the nozzle wall and are used to clamp the nozzle wall. One end of the right clamping arm is connected to the right clamp through a rotating shaft, and the other end is fixed to the right leg in the horizontal direction. By rotating and adjusting the postures of the left clamp and the right clamp, the nozzle wall can be closely fitted to the left clamp and the right clamp.

[0015] Preferably, a boss is provided at the end of the screw-in bolt, which is connected and fixed in cooperation with a groove at the driving end of the clamping left arm.

[0016] Preferably, the calibration code disc has 10*10 grids and a single grid size of 1cm*1cm.

[0017] Another technical solution of the present invention is: a calibration method for a liquid rocket engine nozzle airflow field PIV test, the method comprising the following steps:

[0018] The screw-in bolt and the elastic clamp are matched through the concave and convex surfaces to complete the fixing of the screw-in bolt and the elastic clamp;

[0019] Place the test bench on a horizontal test bench, with the right leg inside the nozzle and the left leg outside the nozzle. Screw in the bolts so that the elastic clamps hold the nozzle wall. Record the screw-in length of the screw-in bolts by the scale lines on the screw-in bolts.

[0020] Place the calibration disc in the groove on the bench, and move the calibration disc until the distance between the calibration disc and the zero position of the scale line on the side of the bench is equal to the screw-in length of the screw-in bolt, ensuring that the calibration disc and the flow field are in the same plane position;

[0021] Record the scale line on the side of the gantry corresponding to the calibration code disk, replace the calibration code disk with the right angle meter, make a ray emitted by the right angle meter coincide with the scale line where the calibration code disk is located at the end of the previous step, and use the vertical visualization function of the right angle meter to adjust the position of the laser generator and the camera so that the nozzle airflow field coincides with the laser irradiation surface;

[0022] Replace the right angle meter with the calibration code disk and adjust the camera focal length to make the camera focal plane coincide with the calibration code disk surface, and finally achieve the coincidence of the camera focal plane, nozzle airflow field and laser irradiation surface.

[0023] The beneficial effects of the present invention compared with the prior art are:

[0024] (1) The present invention realizes the precise positioning of the relative positions of the camera focal plane, the laser irradiation surface and the product flow field by designing a calibration device. Compared with the calibration method of the prior art, the test calibration efficiency is improved while meeting the calibration accuracy.

[0025] (2) The elastic clamp of the present invention ensures the stability of the clamping device and the position accuracy of the calibration device by compensating for the circumferential shape of the nozzle. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a liquid rocket engine nozzle airflow field test system based on PIV technology in an embodiment of the present invention;

[0027] FIG2( a ) is a schematic diagram of a calibration state of a calibration device according to an embodiment of the present invention;

[0028] FIG2( b ) is a relative position positioning state of an embodiment of the present invention;

[0029] FIG3( a ) is a structural diagram of a calibration state of a calibration device according to an embodiment of the present invention;

[0030] FIG3( b ) is a structural diagram of the relative position positioning state of the calibration device according to an embodiment of the present invention;

[0031] FIG. 4( a ) is a side view of the elastic clamp according to an embodiment of the present invention.

[0032] FIG. 4( b ) is a top view of the elastic clamp according to an embodiment of the present invention. DETAILED DESCRIPTION

[0033] The present invention will be further described below in conjunction with the embodiments.

[0034] The liquid rocket engine nozzle airflow field test based on PIV technology uses optical means to measure the distribution of the air film after it is ejected from the small nozzle of the tube bundle nozzle outlet collector during the cold test, and gives an evaluation of the axial length and circumferential uniformity of the supersonic air film, providing data support for actual launch.

[0035] The basic principle of the airflow field particle image velocimetry (PIV) test technology is: add dyed particles to the airflow field, take continuous images, and measure the moving length s of the same particle in two adjacent images. The moving length s = the number of pixels moved by the particle * the length of a single pixel. According to the set interval time t between the two pictures, the velocity vector diagram of the airflow field can be measured after software processing through the formula v = s / t.

[0036] The liquid rocket engine nozzle airflow field test based on PIV technology mainly meets the dynamic characterization of the supersonic air film flow field through non-contact measurement. In order to accurately calculate the flow field velocity results, the test should ensure the position accuracy and dimensional accuracy: the camera focal plane, product flow field and laser irradiation surface are three-sided coincident; the camera focal plane is calibrated in length. Ensuring the accuracy of the calibration results has become a crucial test requirement.

[0037] The test accuracy consists of three aspects: (1) the length of a single pixel is accurately calibrated before the test; (2) the camera focal length (camera focal plane) is ensured to be focused on the laser surface to ensure that the particles are correctly photographed; and (3) the laser surface is ensured to coincide with the flow surface so that the particles are completely dyed by the laser.

[0038] like Figure 1 As shown, according to the test requirements, the present invention provides a calibration device for liquid rocket engine nozzle airflow field PIV test, including a test bench, a screw-in bolt, an elastic clamp, a calibration code disk, a level, and a right angle meter;

[0039] The stand is N-shaped and includes a horizontal beam and two vertical legs. The vertical legs are located at both ends of the horizontal beam and are respectively marked as the left leg and the right leg, which are used to support the horizontal beam. A horizontal groove is provided above the horizontal beam, and guide rails are provided on both sides of the horizontal groove. The side of the horizontal beam is provided with scale lines in the horizontal direction;

[0040] The elastic clamp comprises a left clamping part and a right clamping part, wherein the left clamping part is mounted on the left supporting leg, and the right clamping part is fixed on the right supporting leg, and the left clamping part and the right clamping part cooperate with each other to clamp the nozzle to be tested;

[0041] The screw-in bolt is installed on the left leg to drive the left arm to move, and the screw-in length of the left arm relative to the left leg is recorded through the built-in scale line;

[0042] The calibration code disk can be installed in conjunction with the guide rail and move along the guide rail to calibrate the vertical position of the nozzle airflow field and the focal length of the camera;

[0043] A level, installed on the upper surface of the platform beam, is used to adjust the platform to a horizontal state;

[0044] The right angle meter can be installed in conjunction with the guide rail and move along the guide rail to calibrate the relative position of the camera and the laser generator.

[0045] Preferably, the scale lines on the side of the crossbeam and the scale line zero position on the screw-in bolt correspond to the same vertical reference plane, and the screw-in length of the screw-in bolt is the relative position distance between the nozzle airflow field and the calibration code disk.

[0046] As shown in FIG. 4( a ) and FIG. 4( b ), in the elastic clamp, the left clamping component includes a left clamping arm 7 and a left clamp 8 , and the right clamping component includes a right clamping arm 9 and a right clamp 10 ;

[0047] One end of the left clamping arm 7 is connected to the left clamp 8 by a rotating shaft, and the other end is marked as a driving end, which is inserted into the through hole of the left leg in the horizontal direction. The left clamp 8 and the right clamp 10 are contoured to the nozzle wall and are used to clamp the nozzle wall. One end of the right clamping arm 9 is connected to the right clamp 10 by a rotating shaft, and the other end is fixed to the right leg in the horizontal direction. By rotating and adjusting the postures of the left clamp 8 and the right clamp 10, the nozzle wall can be closely fitted to the left clamp 8 and the right clamp 10.

[0048] Preferably, a boss is provided at the end of the screw-in bolt 1 , which is connected and fixed in cooperation with a groove at the driving end of the clamping left arm 7 .

[0049] The screw-in bolt 1 comprises a screw rod, a differential sleeve and a fixed sleeve;

[0050] The screw-in bolt 1 is similar to the structure of the micrometer screw. A part of the screw is processed into a thread with a pitch of 0.5mm. When it rotates in the fixed sleeve, the screw can move forward or backward. The differential sleeve and the screw are connected as one body, and its periphery is divided into 50 equal grids. The number of full turns of the screw is measured by the 0.5mm interval scale lines of the fixed sleeve, and the part less than one turn is measured by the scale lines around the differential sleeve. The screw drives the left clamping arm 7 to tighten the product.

[0051] The above components have the following advantages:

[0052] (1) Screw in the bolt to realize the clamping function of the elastic clamp on the nozzle, adjust the calibration device to a horizontal state using a level meter, and complete the relative position fixation of the device and the nozzle;

[0053] (2) The calibration code disk moves along the guide rail to achieve the overlap with the nozzle airflow field, and the position of the code disk is determined by the scale lines on the side of the test bench;

[0054] (3) The right angle meter realizes the visualization of the vertical position and completes the relative positioning of the camera and the laser generator;

[0055] (4) The elastic clamp is removable and can be adapted to the clamping and fixing of products with different structures through process design.

[0056] This experimental device is divided into two states. (1) a calibration state, the number of calibration code disks is 10*10, and the single grid size is 1cm*1cm. By taking the image of the calibration code disk, the length of a single pixel point of the calibration code disk can be determined. (2) b relative position positioning state, the level meter is used to determine that the device is in a horizontal state, and the right angle meter is used to determine the relative vertical position of the laser instrument and the camera.

[0057] Based on the above device, the present invention also provides a calibration method for a liquid rocket engine nozzle airflow field PIV test, the method comprising the following steps:

[0058] The screw-in bolt 1 and the elastic clamp 2 are matched through the concave and convex surfaces to complete the fixing of the screw-in bolt 1 and the elastic clamp;

[0059] Place the test bench on a horizontal test bench, with the right leg inside the nozzle and the left leg outside the nozzle, screw in the bolt so that the elastic clamp 2 clamps the nozzle wall, and record the screw-in length of the screw-in bolt through the scale line on the screw-in bolt;

[0060] Place the calibration disc 3 in the groove on the stand, move the calibration disc 3 until the distance between the calibration disc and the zero position of the scale line on the side of the stand is equal to the screw-in length of the screw-in bolt, and ensure that the calibration disc and the flow field are in the same plane position. At this time, the calibration disc surface coincides with the nozzle airflow field;

[0061] Record the scale line on the side of the gantry corresponding to the calibration code disk 3, replace the calibration code disk 3 with the right angle meter 5, so that a ray emitted by the right angle meter coincides with the scale line where the calibration code disk is located at the end of the previous step, and use the vertical visualization function of the right angle meter to adjust the position of the laser generator and the camera so that the nozzle airflow scene coincides with the laser irradiation surface;

[0062] The calibration code disc 3 is replaced with the right angle meter 5, and the focal length of the camera is adjusted to make the focal plane of the camera coincide with the calibration code disc surface, and finally the focal plane of the camera, the nozzle airflow field and the laser irradiation surface are coincident with each other.

[0063] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

Claims

1. A calibration device for liquid rocket engine nozzle airflow field PIV test, characterized by comprising a stand, screw-in bolts, elastic clamps, calibration code discs, a level, and a right angle meter; The stand is N-shaped and includes a horizontal beam and two vertical legs. The vertical legs are located at both ends of the horizontal beam and are respectively marked as the left leg and the right leg, which are used to support the horizontal beam. A horizontal groove is provided above the horizontal beam, and guide rails are provided on both sides of the horizontal groove. The side of the horizontal beam is provided with scale lines in the horizontal direction; The elastic clamp comprises a left clamping part and a right clamping part, wherein the left clamping part is mounted on the left supporting leg, and the right clamping part is fixed on the right supporting leg, and the left clamping part and the right clamping part cooperate with each other to clamp the nozzle to be tested; The screw-in bolt is installed on the left leg to drive the left arm to move, and the screw-in length of the left arm relative to the left leg is recorded through the built-in scale line; The calibration code disk can be installed in conjunction with the guide rail and move along the guide rail to calibrate the vertical position of the nozzle airflow field and the focal length of the camera; A level, installed on the upper surface of the platform beam, is used to adjust the platform to a horizontal state; The right angle meter can be installed in conjunction with the guide rail and move along the guide rail to calibrate the relative position of the camera and the laser generator.

2. A calibration device for PIV test of liquid rocket engine nozzle airflow field according to claim 1, characterized in that the scale line on the side of the crossbeam and the zero position of the scale line on the screw-in bolt correspond to the same vertical reference plane, and the screw-in length of the screw-in bolt is the relative position distance between the nozzle airflow field and the calibration code disk.

3. A calibration device for a liquid rocket engine nozzle airflow field PIV test according to claim 1, characterized in that, in the elastic clamp, the left clamping component includes a clamping left arm (7) and a left clamp (8), and the right clamping component includes a clamping right arm (9) and a right clamp (10); One end of the left clamping arm (7) is connected to the left clamp (8) via a rotating shaft, and the other end is recorded as a driving end and is inserted into the through hole of the left leg in the horizontal direction. The left clamp (8) and the right clamp (10) are contoured with the nozzle wall and are used to clamp the nozzle wall. One end of the right clamping arm (9) is connected to the right clamp (10) via a rotating shaft, and the other end is fixed to the right leg in the horizontal direction. By rotating and adjusting the postures of the left clamp (8) and the right clamp (10), the nozzle wall can be closely fitted with the left clamp (8) and the right clamp (10).

4. A calibration device for a liquid rocket engine nozzle airflow field PIV test according to claim 1, characterized in that a boss is provided at the end of the screw-in bolt (1), which is connected and fixed with the driving end groove of the clamping left arm (7).

5. A calibration device for liquid rocket engine nozzle airflow field PIV test according to claim 1, characterized in that the calibration code disk has 10*10 grids and a single grid size of 1cm*1cm.

6. A calibration method for liquid rocket engine nozzle airflow field PIV test according to claim 1, characterized in that The steps include: The screw-in bolt (1) and the elastic clamp (2) are matched by the concave and convex surfaces to complete the fixing of the screw-in bolt (1) and the elastic clamp; The test bench is placed on a horizontal test bench, with the right leg located inside the nozzle and the left leg located outside the nozzle. The bolt is screwed in so that the elastic clamp (2) clamps the nozzle wall, and the screw-in length of the screw-in bolt is recorded by the scale line on the screw-in bolt. Place the calibration disc (3) in the groove on the stand, and move the calibration disc (3) until the distance between the calibration disc and the zero position of the scale line on the side of the stand is equal to the screw-in length of the screw-in bolt, ensuring that the calibration disc and the flow field are in the same plane position; Record the scale line on the side of the platform corresponding to the calibration code disk (3), replace the calibration code disk (3) with the right angle meter (5), make a ray emitted by the right angle meter coincide with the scale line where the calibration code disk is located at the end of the previous step, and use the vertical visualization function of the right angle meter to adjust the position of the laser generator and the camera so that the nozzle airflow field coincides with the laser irradiation surface; The calibration code disk (3) is replaced with the right angle meter (5), and the focal length of the camera is adjusted so that the focal plane of the camera coincides with the surface of the calibration code disk, and finally the focal plane of the camera, the airflow field of the nozzle and the laser irradiation surface coincide with each other.