Vibration elimination device and method suitable for large field of view background speckle thermometry

Abstract

The application discloses a vibration elimination device suitable for large field background stria thermometry, comprising a background device, a damping device arranged at the bottom of the background device; further comprising a CCD camera, the CCD camera is arranged opposite to the background device, a light source is arranged on one side of the CCD camera, an air outlet is arranged between the CCD camera and the background device, and the air outlet is connected with a air supply device through a heater. The application further discloses a vibration elimination method of the vibration elimination device suitable for large field background stria thermometry. The application solves the problem of inaccurate temperature measurement result existing in the prior art BOS temperature measurement technology.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of non-contact detection of airflow temperature field, and relates to a vibration elimination device suitable for background schlieren thermometry in a large field of view. BACKGROUND

[0002] In the field of building indoor environment research, accurate measurement of airflow temperature is a key link of indoor thermal environment monitoring. As a non-contact optical temperature measurement method, background oriented schlieren (BOS) thermometry has the advantages of no tracer particles and whole-field measurement of temperature field. However, in practical application, vibration interference is a key problem restricting the measurement accuracy of the BOS system. The insufficient anti-vibration performance of the existing BOS thermometry system mainly manifests in the following two aspects: first, the stability problem of the test system itself. When the size of the background pattern needs to be increased to meet the testing demand in a large field of view (meter level), the background pattern of the BOS imaging system is easily disturbed by vibration, resulting in a decrease in the stability of the background device and making it difficult to maintain high-precision measurement in a complex environment; second, the influence of the environment around the flow field to be measured. The vibration of mechanical equipment, human activities and airflow disturbance in the building indoor environment can cause a slight displacement of the background pattern, thereby affecting the accurate calculation of the light refraction angle and ultimately reducing the solving accuracy of the airflow temperature field. SUMMARY

[0003] The purpose of the present application is to provide a vibration elimination device suitable for background schlieren thermometry in a large field of view, which solves the problem of inaccurate temperature measurement in the existing BOS thermometry technology.

[0004] Another purpose of the present application is to provide a vibration elimination method suitable for background schlieren thermometry in a large field of view.

[0005] The first technical solution adopted by the present application is a vibration elimination device suitable for background schlieren thermometry in a large field of view, which comprises a background device, a vibration reduction device is arranged at the bottom of the background device; a CCD camera is arranged opposite to the background device, a light source is arranged on one side of the CCD camera, an airflow outlet is arranged between the CCD camera and the background device, and the airflow outlet is connected to an air supply device through a heater.

[0006] The first technical solution of the present application is characterized in that:

[0007] The vibration reduction device comprises a bottom plate, a damping vibration absorber is arranged at the center of the bottom plate, a tray is arranged above the damping vibration absorber, first spring vibration absorbers are arranged at four vertices between the tray and the bottom plate; a support base is arranged on the tray, two second spring vibration absorbers are arranged at two ends of the tray respectively, and each second spring vibration absorber is in contact with the side surface of the support base through a rubber block.

[0008] The second spring damper is vertically connected to the adjustment handle.

[0009] The background device includes several splicing modules, and a vibration sensor is arranged on the back of each splicing module.

[0010] The second technical solution adopted in this invention is a vibration elimination method for a large field-of-view background schlieren thermometry device, which specifically includes the following steps:

[0011] Step 1: Based on the principle that the area of ​​the background device is greater than twice the area of ​​the flow field observation size, construct the background device, and select a length of [missing information] for each splicing module on the background device. A A reference object is placed above the airflow outlet, and an image is captured using a CCD camera to obtain the pixel distance of the object in the image. B ;

[0012] Step 2: Remove the reference object, do not turn on the air supply device and heater, ensure no airflow is emitted from the air outlet, and then use a CCD camera to capture an image of the background device without flow field disturbance. Record the horizontal vibration amplitude monitored by the m stitching modules at the current time t1. u x and vertical vibration amplitude u y The horizontal vibration pixel displacement is obtained through formulas (1) and (2). u 1 and vertical vibration pixel displacement v 1:

[0013] (1)

[0014] (2)

[0015] Step 3: Turn on the air supply device and heater to allow the hot airflow to dissipate from the air outlet. Then, use a CCD camera to capture an image of the background device with flow field disturbance, and record the horizontal vibration amplitude monitored by the m stitching modules at the current time t2. u x ’ and vertical vibration amplitude u y ’ The horizontal vibration pixel displacement is obtained through formulas (3) and (4). u 2 and vertical vibration pixel displacement v 2:

[0016] (3)

[0017] (4)

[0018] Step 4, the pixel values at time t1 and t2 are subtracted, and the error displacement caused by the vibration of each stitching module is obtained by formulas (5) and (6) u 3 and v 3:

[0019] (5)

[0020] (6)

[0021] Step 5, the displacement of the pixel value of the background image without flow field disturbance in the horizontal direction and the vertical direction is obtained ∆x and ∆ y According to the positions of the stitching module and the stitching gap in the image, the image is regionally divided, and the complete displacement field data is split to obtain the displacement field data of each region.

[0022] Step 6, the horizontal direction displacement u 1 x, y ) and the vertical direction displacement v 1 x, y ) of each region are subtracted by the horizontal direction error displacement u 3 v ) and the vertical direction error displacement u 3 x, y ) calculated in step 4 to obtain the corrected horizontal direction displacement v 2 x, y ) and the vertical direction displacement 2

[0023] of each region. u x, y Step 7, the corrected displacement field data of each region in step 6 is recombined to obtain the corrected complete horizontal direction displacement v ( x, y ) and the vertical direction displacement (

[0024] ). n x, y Step 8, the refractive index (

[0025] ) is obtained by solving the Poisson equation according to the complete displacement field data obtained in step 7. n x, y Step 9, the density field data p ( x, y ) is solved according to the refractive index field data (

[0026] ) obtained in step 8. T x, y Step 10, the density field is converted into temperature field data to complete the quantitative solution of the air flow temperature field (

[0027] .The second technical solution of the present application is characterized in that:

[0028] In step 5, the horizontal displacement of the background pattern is obtained by formula (7) and (8) ∆x And the vertical displacement ∆y :

[0029] (7)

[0030] (8)

[0031] In the formula, ZD is the distance between the background and the flow field to be measured; Zi is the distance from the camera lens to the image plane; ZB is the distance from the camera to the background; ΔZD is half the thickness of the flow field to be measured; n is the refractive index inside the flow field; n0 is the refractive index of the surrounding air.

[0032] In step 6, the corrected horizontal displacement u 2( x, y ) and vertical displacement v 2( x, y ) of each region are obtained by formula (9) and (10);

[0033] (9)

[0034] (10).

[0035] In step 8, the refractive index n ( x, y ) is obtained by solving Poisson equation by formula (11):

[0036] (11)

[0037] In the formula, n ( x , y ) is the refractive index value of the grid point x , y , h is the grid step.

[0038] In step 9, the density field data ρ(x,y) is solved by formula (12):

[0039] (12)

[0040] In the formula, K is the Grass-Ton-Dale constant, and ρ is the density of the gas.

[0041] The specific process of step 10 is to convert the density field into the temperature field data by formula (13) to complete the quantitative solution of the airflow temperature field T(x, y):

[0042] (13)

[0043] In the formula, P is the environmental pressure, and R is the gas constant.

[0044] The beneficial effects of the present application are as follows:

[0045] (1) The vibration elimination method of the large field of view BOS imaging system: the vibration elimination method reduces the influence of vibration disturbance on the system measurement results from two aspects of the BOS imaging system and the background pattern displacement error correction. Specifically, by arranging a vibration sensor behind the background device, the vibration amplitude and vibration frequency of the splicing module in the test environment are monitored in real time, and according to the monitored vibration data characteristics (amplitude and frequency), the pressure in the vibration damper cavity is adjusted, so that the background device can be suitable for different vibration intensity test scenes; according to the monitored vibration amplitude, the error correction algorithm is used to correct the background pattern displacement field caused by vibration in different regions, and the accuracy of the temperature field test result is further improved.

[0046] (2) Design of combined vibration damping device of BOS imaging system: the combined vibration damping device is designed to eliminate the influence of horizontal and vertical vibration of the system, and according to the vibration frequency and vibration amplitude monitored by the vibration sensor in real time, the pressure in the damping damper cavity and the compression degree of the spring damper in the vibration damping device are adjusted, so that the background schlieren temperature measurement system can adapt to different test scenes.

[0047] (3) Algorithm correction of vibration environment background pattern displacement error: the vibration sensor is used to monitor the vibration amplitude of each splicing module in real time and convert it into pixel displacement, the cross-correlation algorithm is used to calculate the displacement field data, and the displacement error correction algorithm is further used to correct the influence of environmental vibration on the background schlieren displacement field in different regions, so as to obtain the displacement field calculation result without vibration disturbance and improve the precision of solving the temperature field data of the system. BRIEF DESCRIPTION OF DRAWINGS

[0048] Figure 1 It is a structural schematic view of the vibration elimination device suitable for large field of view background schlieren temperature measurement of the present application;

[0049] Figure 2 It is a schematic view of the vibration damping device in the vibration elimination device suitable for large field of view background schlieren temperature measurement of the present application;

[0050] Figure 3 It is a vibration sensor arrangement schematic view in the vibration elimination device suitable for large field of view background schlieren temperature measurement of the present application;

[0051] Figure 4Flow chart of the elimination method of the vibration elimination device suitable for large field of view background texture shadow thermometry of the present application;

[0052] Figure 5 Error displacement comparison chart under different vibration frequencies in the elimination method of the vibration elimination device suitable for large field of view background texture shadow thermometry of the present application;

[0053] Figure 6 Displacement vector distribution comparison chart at 0.1 m above the hot airflow before and after vibration elimination in the elimination method of the vibration elimination device suitable for large field of view background texture shadow thermometry of the present application;

[0054] Figure 7 Temperature field calculation result error comparison chart before and after vibration elimination in the elimination method of the vibration elimination device suitable for large field of view background texture shadow thermometry of the present application;

[0055] In the figure, 1. background device, 101. splicing module, 102. vibration sensor, 103. data transmission line;

[0056] 2. vibration reduction device, 201. damping vibration absorber, 202. first spring vibration absorber, 203. second spring vibration absorber, 204. rubber block, 205. adjusting handle, 206. tray, 207. bottom plate, 208. support base;

[0057] 3. CCD camera, 4. light source, 5. computer, 6. air supply device, 7. heater, 8. airflow outlet, 9. exhaust device. DETAILED DESCRIPTION

[0058] The present application will be described in detail below in combination with the drawings and specific embodiments.

[0059] The vibration elimination device suitable for large field of view background texture shadow thermometry of the present application is used to improve the portability of the measuring device and the accuracy of the measurement results. Its main features include: ① vibration sensors are installed on the back side of the background device to monitor the vibration data of the test environment in real time; ② combined vibration reduction devices are designed and installed in the four corners of the bottom of the background device, and the vibration data of each splicing module collected by the computer are used as input signals to control the pressure in the vibration absorber cavity using a controller to reduce the vibration interference of the test environment; ③ a background pattern displacement error correction algorithm is introduced to correct the error of the pattern displacement field calculation result in different regions according to the vibration amplitude of each splicing module.

[0060] Example 1

[0061] The vibration elimination device suitable for large field of view background texture shadow thermometry of the present application, as shown in Figure 1As shown, the device includes a background device 1, a vibration damping device 2, a CCD camera (charge-coupled device camera) 3, a light source 4, a computer 5, an air supply device 6, a heater 7, an air outlet 8, and an exhaust device 9. Its functions are as follows: the background device 1 provides a large background area for temperature measurement; the vibration damping device 2 improves the stability of the background device 1; the light source 4 is positioned next to the CCD camera 3 to uniformly illuminate the background pattern; the CCD camera 3 is used to capture schlieren images with and without a flow field; the airflow is controlled by the air supply device 6, then by the heater 7 to control the airflow temperature, and finally dissipated through the air outlet 8; the computer 5 is used to set the shooting parameters of the CCD camera 3 and process the schlieren image data; and the exhaust device 9 is used to adjust the vibration conditions of the experiment.

[0062] Example 2

[0063] like Figure 2 As shown, the vibration damping device 2 includes a base plate 207, a damping damper 201 is disposed at the center of the base plate 207, a tray 206 is disposed above the damping damper 201, and first spring dampers 202 are disposed at the four vertices between the tray 206 and the base plate 207 to reduce the longitudinal vibration of the portable assembled background schlieren device. A support base 208 is placed on the tray 206, one end of a second spring damper 203 is fixed to the side of the tray 206, and the other end of the second spring damper 203 is connected to a rubber block 204. The rubber block 204 contacts the side of the support base 208 to achieve the fixation of the support base 208 and the lateral vibration damping of the background device 1.

[0064] The second spring damper 203 is vertically connected to the adjustment handle 205. By moving the adjustment handle 205 laterally, the compression degree of the spring in the spring damper can be adjusted, thereby causing the rubber block 204 to move laterally, which facilitates the installation and disassembly of the bracket base 208 and the damping device.

[0065] Example 3

[0066] like Figure 3 As shown, the background device 1 consists of multiple splicing modules 101. Each splicing module 101 has a vibration sensor 102 (model: WT-VB01-485) arranged on its back to monitor the vibration data of each splicing module 101 and import the data into the computer 5 through the data transmission line 103.

[0067] The frame of the splicing module 101 is made of aluminum splicing material, and its front is sprayed with a background pattern. Its size is 0.6 m × 0.6 m.

[0068] The number of splicing modules 101 is determined by the flow field observation area, and the ratio of the area of ​​the background device 1 to the flow field observation area should be greater than 2.

[0069] The vibration sensor 102 can monitor the three-axis vibration amplitude and vibration frequency of the splicing module 101, and transmit the monitoring data to the computer 5 through the data transmission line 103.

[0070] The optimal setting parameters of the vibration damping device under different vibration frequencies are obtained through experiments, and a database is formed in the computer 5 to set the control strategy, so that the background schlieren temperature measurement system can control the pressure in the damping chamber of the damping device and the compression degree of the second spring damper 203 according to the vibration frequency monitored by the vibration sensor 102 in real time.

[0071] Embodiment 4

[0072] The air exhaust device 9 is used to control the vibration condition of the experiment, and the vibration damping device 2 is placed below the background device 1 to improve the stability of the background device 1. The light source 4 and the CCD camera 3 are arranged on one side of the air outlet 8, and the background device 1 is arranged on the other side of the air outlet 8. The light source 4 is arranged beside the CCD camera 3, and uniformly illuminates the background pattern on the background device 1. When the system is not in air flow, the computer 5 is used to control the CCD camera 3 to shoot the image without flow field, and the background pattern in the image does not occur deflection; after the air supply device 6 and the heater 7 are turned on, hot air flow is discharged from the air outlet 8, and the CCD camera 3 is controlled to shoot the image with flow field, and the background pattern is affected by the hot air flow to cause the light to be refracted, and the deflection displacement of the background pattern can be obtained by calculating the cross-correlation of the two images, and then the air flow refractive index distribution is calculated by solving the Poisson equation, and finally the air flow density distribution is calculated by the G-D equation, and finally the air flow temperature distribution is obtained according to the ideal gas state equation.

[0073] The vibration amplitude received by different splicing modules 101 in different directions is different, in order to reduce the error of the flow field calculation caused by the vibration interference in the test environment, the displacement error correction algorithm is used to correct the air flow displacement field data obtained by using the cross-correlation calculation according to the real-time monitoring of the vibration amplitude of each splicing module 101, which can reduce the error displacement of the background schlieren system caused by the environmental vibration, and the displacement error correction algorithm is introduced to solve the air flow temperature field data.

[0074] Embodiment 5

[0075] The present application is suitable for the vibration elimination method of large field of view background schlieren temperature measurement, and the flow is as shown in Figure 4 , and specifically includes the following steps:

[0076] Step 1, the surface of the background plate is sprayed with a background pattern, according to the principle that the area of the background device is greater than twice the area of the flow field observation size, the background device 1 is built, the light source 4 is turned on to illuminate the background device 1, and a reference object with a length of A is placed above the air outlet 8, and the CCD camera 3 is used to shoot the image to obtain the pixel distance of the object in the imageB ;

[0077] Step 2, remove the reference, do not open the air supply device 6 and the heater 7, the system without airflow emission, and then use the CCD camera 3 to shoot the background device 1 to obtain the flow field disturbance image without flow field disturbance, record the horizontal direction vibration amplitude monitored by the m splicing modules at the current t1 time u x And the vertical direction vibration amplitude u y The horizontal direction vibration pixel displacement u 1 and the vertical direction vibration pixel displacement v 1 are obtained by formulas (1) and (2);

[0078] (1)

[0079] (2)

[0080] Step 3, open the air supply device 6 and the heater 7, so that the hot air flow is emitted from the air outlet 8, and then use the CCD camera 3 to shoot the background device 1 to obtain the flow field disturbance image with flow field disturbance, record the horizontal direction vibration amplitude monitored by the m splicing modules at the current t2 time u x ’ And the vertical direction vibration amplitude u y ’ The horizontal direction vibration pixel displacement u 2 and the vertical direction vibration pixel displacement v 2 are obtained by formulas (3) and (4);

[0081] (3)

[0082] (4)

[0083] Step 4, difference the pixel values at t1 and t2, through formulas (5) and (6), the horizontal direction error displacement u 3 and the vertical direction error displacement v 3 caused by the vibration of each splicing module are obtained;

[0084] (5)

[0085] (6)

[0086] Step 5, using the flow field disturbance images with and without flow field disturbance shot by the CCD camera 3, through formulas (7) and (8), the horizontal direction displacement amount ∆x And the vertical direction displacement amount ∆y, according to the position of the splicing module and the splicing gap in the image, the image is regionally divided, and the complete displacement field data is split to obtain the horizontal direction displacement u 1( x, y ) and vertical direction displacement v 1( x, y ) of each region;

[0087] (7)

[0088] (8)

[0089] In the formula, ZD is the distance between the background and the flow field to be measured; Zi is the distance from the camera lens to the image plane; ZB is the distance from the camera to the background; ΔZD is half of the thickness of the flow field to be measured; n is the refractive index inside the flow field; n0 is the refractive index of the surrounding air.

[0090] Step 6, subtract the horizontal direction error displacement u 3 and the vertical direction error displacement x, y 3 calculated in step 4 from the horizontal direction displacement v 1( x, y ) and the vertical direction displacement u 1( v ) of each region, and obtain the corrected horizontal direction displacement u 2( x, y ) and the vertical direction displacement v 2( x, y ) of each region through formulas (9) and (10);

[0091] (9)

[0092] (10)

[0093] Step 7, recombine the corrected displacement field data of each region in step 6 to obtain the corrected complete horizontal direction displacement u ( x, y ) and the vertical direction displacement v ( x, y ).

[0094] The present application first monitors the vibration amplitude of each splicing module through a vibration sensor to obtain the background pattern error displacement caused by vibration; then calculates the displacement field data of the airflow through the background schlieren technique; and finally performs regional error correction on the displacement field according to the vibration monitoring data to obtain the corrected complete displacement field data.

[0095] After correcting the displacement field data obtained by the background schlieren technique using the vibration elimination method of this invention, more accurate temperature field data can be obtained. The steps for solving the temperature field data based on the displacement field data are as follows:

[0096] Step 8: Based on the complete displacement field data obtained in Step 7, solve the Poisson equation using formula (11) to obtain the refractive index. n ( x, y ):

[0097] (11)

[0098] In the formula n ( x , y ) is a grid point ( x , y The refractive index value of ) h It is the grid step size.

[0099] Step 9: Based on the refractive index field data obtained in Step 8 n ( x, y The density field data can be solved using formula (12). p ( x, y ).

[0100] (12)

[0101] In the formula, K It is the Glaston-Dale constant, with a value of 0.0002257 m. 3 / kg; p Let be the density of the gas.

[0102] Step 10: Using formula (13), the density field is further converted into temperature field data to complete the analysis of the airflow temperature field. T ( x, y ) quantitative solution.

[0103] (13)

[0104] In the formula, P It's environmental pressure. R It is the universal gas constant ( R =8.314 J·mol⁻¹·K⁻¹.

[0105] Example 6

[0106] This embodiment explores the applicability of the vibration reduction device of the present invention by taking the background schlieren imaging thermal airflow temperature field test analysis as an example under different vibration frequency test environments. The focus is on analyzing the influence of different vibration frequencies on the temperature measurement results of the background schlieren imaging system. During the experiment, multiple experimental conditions with different frequencies were set by adjusting the rotation frequency of the exhaust device, as detailed in Table 1.

[0107] Table 1 Test Environment Vibration Disturbance Test Conditions

[0108]

[0109] The experimental procedure is as follows:

[0110] Step 1: Spray a background pattern onto the background board surface and build a background device 1 with dimensions of 1.8 m × 1.8 m. The airflow outlet 8 has a diameter of 0.15 m and a pixel distance of 300 px in the image.

[0111] Step 2: Use CCD camera 3 to capture a background device 1 to obtain an image without flow field disturbance. Turn on the air supply device 6 and heater 7, and control the airflow velocity and temperature to 1 m / s and 100 ℃ respectively. Use CCD camera 3 to capture a background device 1 to obtain an image with flow field disturbance.

[0112] Step 3: Adjust the vibration frequency according to the experimental conditions, repeat step 2, and obtain vibration and flow field disturbance images under different conditions.

[0113] Step 4: Use formulas (7) and (8) to solve for the background image displacement caused by the high-temperature hot airflow.

[0114] Based on the above steps, the background pattern displacement vectors at different vibration frequencies under the presence of a vibration damping device were obtained, such as... Figure 5 As shown, when the vibration frequency is 5-30 Hz, the vibration damping device can effectively reduce vibration, and the calculated displacement error is approximately 0.056 px, which is relatively small. When the vibration frequency is 30 and 40 Hz, the displacement error caused by vibration is approximately 0.14 px, which is 150% larger than that at lower vibration frequencies. Therefore, the vibration damping device has a good vibration reduction effect in the 5-30 Hz vibration frequency range. A large displacement vector error will cause the refractive index field data obtained by solving the Poisson equation to fail to reflect the correct flow field distribution, ultimately leading to a large error in the temperature field calculation results.

[0115] Example 7

[0116] This embodiment takes different damping measures of background schlieren system as an example to explore the influence of damping system on the calculation accuracy of BOS system. The heat flow emission temperature difference is 100 ℃, the emission outlet diameter is 0.15 m, and the emission speed is 1 m / s. The specific operation steps of the experiment are as follows:

[0117] Step 1, vertically arrange 7 temperature measuring points above the air outlet, the distance between measuring points is 0.075 m, and horizontally arrange 4 measuring points above the air outlet 8 at 0.225 m, the distance between measuring points is 0.075 m, open the air supply device 6 and the heater 7, control the air flow emission speed and temperature respectively as 1 m / s and 100 ℃, after the air flow is stable, record the temperature data of each measuring point.

[0118] Step 2, adjust the vibration frequency in the test environment to 20 Hz, build an image acquisition device without damping device, use CCD camera 3 to shoot background device 1 to obtain flow field disturbance image without flow field; open the air supply device 6 and the heater 7, and collect the schlieren image with flow field after the emission stable flow field;

[0119] Step 3, use formulas (7) and (8) to process the image pairs shot in step 2 to obtain the air flow displacement field data under the condition without damping device;

[0120] Step 4, build an image acquisition device with damping device, use CCD camera 3 to shoot background device 1 to obtain flow field disturbance image without flow field, open the air supply device 6 and the heater 7, and collect the schlieren image with flow field after the emission stable flow field, use vibration sensor to monitor the vibration displacement of splicing module 101 as 0.3 px and 0.2 px;

[0121] Step 5, use formulas (7) and (8) to process the image pairs shot in step 4 to obtain the displacement field data with vibration error, and then use error displacement correction algorithm to obtain the displacement field data after error correction;

[0122] Step 6, extract the displacement value at 0.1 m above the air outlet 8 in the calculation result of air flow displacement field;

[0123] Step 7, extract the calculation result of air flow temperature field and compare it with the thermocouple measurement result.

[0124] The displacement vector field calculation results obtained under different conditions are as follows: Figure 6It can be seen from the figure that there are error displacement vectors on both sides of the flow field, and it is difficult to ensure that the displacement vector value in the area not disturbed by the flow field is 0 px. When there is no damping system, the average value of the error displacement vectors on both sides of the flow field obtained by the background schlieren system is about 0.28 px; by adding a damping device, the background displacement caused by vibration can be better eliminated, but there is still a small displacement vector error on both sides of the flow field, about 0.15 px; further using the displacement error repair algorithm to process the calculation results, the displacement vector value around the flow field is reduced to 0.09 px, compared with the optimization without damping system, the error displacement vector value is reduced by 0.19 px, and the relative error is reduced by 67.9%.

[0125] Further analysis of the experimental error of the BOS airflow temperature field test and the thermocouple test results, such as Figure 7 Under the same vibration conditions, after using the damping device and the error displacement repair algorithm, the error values of the remaining measuring points are less than those without the damping device. The average error of the system calculation temperature based on the damping device is 3.2%, and the average error of the system calculation temperature based on the damping device and the error displacement repair algorithm is 2.6%, so the calculation accuracy of the airflow temperature field of the background schlieren system is improved by 0.6% after adding the damping device under the design background.

Claims

1. A method of cancellation for a vibration cancellation device suitable for large field of view background speckle thermography, characterized in that: The vibration elimination device suitable for large field background schlieren temperature measurement comprises a background device (1), a damping device (2) is arranged at the bottom of the background device (1); further comprising a CCD camera (3), the CCD camera (3) is arranged opposite to the background device (1), a light source (4) is arranged on one side of the CCD camera (3), an air outlet (8) is arranged between the CCD camera (3) and the background device (1), the air outlet (8) is connected with a air supply device (6) through a heater (7); Specifically comprising the following steps: Step 1, according to the principle that the area of the background device (1) is greater than 2 times the area of the flow field observation size, the background device (1) is built, and a length of A is selected as a reference object on each splicing module (101) of the background device (1) and placed above the air outlet (8), and a CCD camera (3) is used to shoot an image to obtain the pixel distance B of the reference object in the image; Step 2, remove the reference, not open air supply device (6) and heater (7), no air flow in the outlet (8) emission, and then use the CCD camera (3) to shoot the background device (1) to obtain no flow field disturbance image, record the current t1 moment m splicing module monitoring the horizontal direction vibration amplitude u x And vertical direction vibration amplitude u y , through the formula (1) and (2) to obtain horizontal direction vibration pixel displacement u 1 and vertical direction vibration pixel displacement v 1: （1） （2） Step 3, turn on the air supply device (6) and the heater (7) to make the hot air flow from the air outlet (8), and then use the CCD camera (3) to capture the background device (1) to obtain the flow field disturbance image, and record the horizontal direction vibration amplitude monitored by the m splicing modules at the current t2 moment u x ’ and the vertical direction vibration amplitude u y ’ The horizontal direction vibration pixel displacement is obtained by formulas (3) and (4) u 2 and the vertical direction vibration pixel displacement v 2: （3） （4） Step 4, the pixel values at time t1 and t2 are subtracted, and the error displacement caused by the vibration of each splicing module is obtained through formulas (5) and (6) u 3 and v 3: （5） （6） Step 5, obtaining the displacement amount of the pixel value of the horizontal and vertical direction flow field disturbance background image x and y According to the position of the splicing module (101) and the splicing gap in the image, the image is regionally divided, and the complete displacement field data is split to obtain the displacement field data of each region. Step 6, horizontal direction displacement of each region is displaced u 1( x,y ) and vertical direction displacement v 1( x,y ) is subtracted by horizontal direction error displacement u 3 and vertical direction error displacement v 3 calculated in step 4, to obtain corrected horizontal direction displacement u 2( x,y ) and vertical direction displacement v 2( x,y ) of each region; Step 7, recombining the corrected displacement field data of each region in step 6 to obtain the corrected complete horizontal direction displacement u ( x,y ) and vertical direction displacement v ( x,y ); Step 8, solve the Poisson equation for the refractive index from the complete displacement field data obtained in step 7 n ( x,y ) Step 9, refractive index field data obtained from step 8 n ( x,y ), solving density field data ρ ( x,y ); Step 10, converting the density field to temperature field data, completes the quantitative solution of the gas flow temperature field T ( x,y ) 2. The method of claim 1, wherein the method is applied to a large field of view background speckle thermography. The damping device (2) comprises a bottom plate (207), a damping damper (201) is arranged at the center of the bottom plate (207), a tray (206) is arranged above the damping damper (201), and four first spring dampers (202) are arranged at four vertexes between the tray (206) and the bottom plate (207); a support base (208) is arranged on the tray (206), two second spring dampers (203) are arranged at two ends of the tray (206) respectively, and each second spring damper (203) is in contact with the side surface of the support base (208) through a rubber block (204).

3. The method of claim 2, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. The second spring damper (203) is connected with an adjusting handle (205) in the vertical direction.

4. The method for eliminating vibration according to claim 2, which is suitable for large field background schlieren thermometry, characterized in that: The background device (1) comprises a plurality of splicing modules (101), and a vibration sensor (102) is arranged on the back of each splicing module (101).

5. The method of claim 1, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. In step 5, the horizontal displacement amount of the background pattern is obtained by equations (7) and (8) x and the vertical displacement amount y : （7） （8） wherein ZD is the distance between the background and the flow field to be measured; Zi is the distance from the camera lens to the image plane; ZB is the distance from the camera to the background; ΔZD is half of the thickness of the flow field to be measured; n is the refractive index inside the flow field; n0 is the refractive index of the surrounding air.

6. The method of claim 5, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. In step 6, the horizontal displacement of each region after correction is obtained by formulas (9) and (10) u 2( x,y ) and the vertical displacement v 2( x,y ) of each region （9） （10）。 7. The method of claim 6, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. In step 8, the refractive index is obtained by solving the Poisson equation using equation (11) n ( x,y ) （11） wherein n ( x , y ) are the refractive index values of the grid points ( x , y ), h is the grid step.

8. The method of claim 7, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. In step 9, the density field data ρ(x,y) is solved by using formula (12): （12） In the formula, K is the Grass-Ton-Dale constant, and ρ is the density of the gas.

9. The method of claim 8, wherein the method is applied to a vibration cancellation device for large field-of-view background speckle thermography. The specific process of step 10 is that the density field is converted into temperature field data by formula (13), and the quantitative solution of the air flow temperature field T(x,y) is completed: （13） In the formula, P is the environmental pressure, and R is the gas constant.

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