CN117233126B - Background schlieren measurement calibration device and method - Google Patents
Background schlieren measurement calibration device and method Download PDFInfo
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- CN117233126B CN117233126B CN202311205420.9A CN202311205420A CN117233126B CN 117233126 B CN117233126 B CN 117233126B CN 202311205420 A CN202311205420 A CN 202311205420A CN 117233126 B CN117233126 B CN 117233126B
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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Abstract
The invention discloses a background schlieren measurement calibration device and a method, comprising background schlieren equipment and a background plate, and further comprising an experiment bin, wherein two independent density cavities are symmetrically arranged in the experiment bin, and the background schlieren equipment and the background plate are respectively arranged at two ends of the density cavities; the method comprises the steps that two density cavities are respectively provided with a density detector, at least one density cavity is provided with a pressure control valve, the pressure control valve is connected with a pressure control device, the density detectors, the pressure control valve and the pressure control device are connected with a control box, and the method is characterized in that background schlieren equipment is calibrated by using a background schlieren measurement calibration device. According to the invention, by arranging two density cavities, one is used as a control and the other is used as a pressurizing experiment, on one hand, the equivalent density is calculated through the background schlieren equipment, on the other hand, the density of the air field is actually measured through the density monitor, and the measuring accuracy and precision of the background schlieren equipment are accurately analyzed through the comparison of a calculated value and an actually measured value.
Description
Technical Field
The invention belongs to the field of density field measurement, and relates to an equivalent density calibrating device based on background schlieren measuring equipment and a method for calibrating the equivalent density of the background schlieren measuring equipment by using the device.
Background
Background schlieren measurement is a recently developed large field flow field display and measurement technique that is measured by characterizing the phenomenon of light deflection caused by non-uniform characteristics in transparent media that are often invisible to the naked eye. Background schlieren measurement is mainly performed by utilizing the principle that light rays are deflected under the influence of the density of a transparent medium (such as air), and the measurement result is the equivalent density of the medium through which the light rays pass due to the complex density change inside the transparent medium.
The background schlieren is utilized to measure the offset of the background plate mark points caused by the complex structure in the wind tunnel, and the highly unsteady/nonlinear complex flow phenomena such as wind field flow separation, unstable shear layer, wave/vortex/shear layer interference and the like can be demonstrated.
In the process of implementing the present invention, the inventor finds that at least one of the following technical problems exists in the prior art:
The background schlieren equipment calculates the offset of each standard point through a system algorithm carried by the equipment to obtain the equivalent density of the wind field, but the accuracy of the equivalent density measured by the mode cannot be verified.
Disclosure of Invention
In view of this, the present invention aims to provide a means for calibrating or/and verifying the accuracy and precision of equivalent density measurements of background schlieren measuring devices.
Another object of the present inventors is to provide a method for calibrating a background schlieren measuring device using the aforementioned apparatus.
The inventor continuously reforms and innovates through long-term exploration and trial and repeated experiments and efforts, and the technical scheme provided by the invention is that the background schlieren measurement and calibration device comprises background schlieren equipment and a background plate and further comprises an experiment bin, wherein two independent density cavities are symmetrically arranged in the experiment bin, and the background schlieren equipment and the background plate are respectively arranged at two ends of the density cavities; the density detectors are arranged in the two density cavities, the pressure control valve is arranged in at least one density cavity, the pressure control valve is connected with the pressure control device, and the density detectors, the pressure control valve and the pressure control device are connected with the control box.
According to one embodiment of the background schlieren measurement calibration device, the inside of the experimental bin is symmetrically divided into a first density cavity and a second density cavity by a partition plate, and the partition plate is perpendicular to the background plate.
According to one embodiment of the background schlieren measurement calibration device of the present invention, the experimental bin is cylindrical, and the partition is arranged vertically.
According to one embodiment of the background schlieren measurement calibration device of the present invention, the device further comprises a bracket, and the density chamber is fixedly mounted on the bracket.
According to one embodiment of the background schlieren measurement calibration device, the support comprises a platform, a fixing groove is arranged above the platform, and the experimental bin is horizontally fixed in the fixing groove through a fixing hoop.
According to one embodiment of the background schlieren measurement calibration device of the present invention, both the pressure control device and the control box are mounted on the support.
According to one embodiment of the background schlieren measurement calibration device of the present invention, the first density chamber is fitted with a first density detector and a first pressure control valve, and the second density chamber is fitted with a second density detector and a second pressure control valve.
According to one embodiment of the background schlieren measurement calibration device, the control box enables the air pressure in the two density cavities to be normal pressure by controlling the pressure control device and the pressure control valve, and the background schlieren equipment is started to obtain normal pressure measuring points and record data of the first density monitor; maintaining a density chamber at normal pressure, and maintaining a first measuring point as a reference; the other density cavity sequentially increases air pressure according to a preset gradient, the background schlieren equipment is started again after the air pressure is increased and stabilized each time, a pressurizing measurement point is obtained, the offset is measured, and the air equivalent density rho 1-n is calculated through the background schlieren equipment; simultaneously recording density monitor data ρ 2-n for each gradient; comparing ρ 1-n with ρ 2-n, calculating a density error; sequentially pressurizing to obtain multiple groups of data, sequentially depressurizing to obtain multiple groups of data, and calculating variances of all groups of data to obtain density measurement errors of the background schlieren equipment.
According to one embodiment of the background schlieren measurement calibration device, the data of the density monitor is taken as a true value, and the background schlieren correction equipment is calibrated.
The invention also provides a background schlieren measurement calibration method by using the device, which comprises the following steps:
S1: the control box controls the pressure control device, the first pressure control valve and the second pressure control valve to enable the air pressure in the first density cavity and the air pressure in the second density cavity to be normal pressure, the background schlieren equipment is started, a first measuring point is obtained on a background plate corresponding to the first density cavity, and a second measuring point is obtained on a background plate corresponding to the second density cavity; the first measuring point is in line symmetry with the second measuring point; the first measuring point and the second measuring point are both normal pressure measurement;
S2: maintaining the air pressure of the first density cavity at normal pressure, controlling the pressure control device and the first pressure control valve to increase the air pressure of the second density cavity according to a preset gradient value, starting the background schlieren equipment after the air pressure is stabilized after each pressurizing, acquiring a first measuring point on a background plate corresponding to the first density cavity, and acquiring a pressurizing measuring point on a background plate corresponding to the second density cavity; taking the first measuring point as a symmetrical reference, measuring the offset of the pressurizing measuring point, and calculating the air equivalent density rho 1 through background schlieren equipment;
s3: while the background schlieren device is activated, density monitor data ρ 2 for each gradient of the second density chamber is recorded,
S4: sequentially pressurizing according to preset gradients to obtain multiple groups of data, sequentially depressurizing according to the same gradients to obtain multiple groups of data after reaching the highest pre-examination pressure or the highest tolerance pressure of the second density cavity, comparing rho 1-n with rho 2-n, and calculating density errors under the gradients;
S5: calculating variance according to the density error under each gradient to obtain the density measurement error of the background schlieren equipment;
S6: and calibrating and correcting the background schlieren equipment by taking the data of the second density monitor under each gradient as a true value.
Compared with the prior art, one of the technical schemes has the following advantages:
a) The inventor designs the calibrating device according to the background schlieren measuring principle, which is used for calibrating and verifying the accuracy and precision of the equivalent density measured by the background schlieren measuring equipment. According to the invention, by arranging two density cavities, one is used as a control and the other is used as a pressurizing experiment, on one hand, the equivalent density is calculated through the background schlieren equipment, and on the other hand, the density of the air field is actually measured through the density monitor, and the measuring precision of the background schlieren equipment is accurately analyzed through the comparison of a calculated value and an actually measured value.
B) According to the invention, the first measuring point is obtained in the first density cavity and the second measuring point is obtained in the second density cavity, and the offset of the measuring points under different concentrations can be directly and accurately calculated through mirror image processing.
C) The device can verify and calibrate the measurement accuracy and precision of background schlieren equipment with different algorithms.
D) According to the device, the first density cavity and the second density cavity are arranged, so that the interference of factors such as temperature, light and the like is discharged in the verification and calibration processes, and the reliability of a verification result is ensured.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some examples of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a principle mechanism of a background schlieren measurement calibration device according to the present invention.
Fig. 2 is a schematic front view of a background schlieren measurement calibration device according to a preferred embodiment of the invention.
Fig. 3 is a schematic top view of fig. 2.
Fig. 4 is a schematic perspective view of fig. 2.
FIG. 5 is a schematic cross-sectional view of A-A in FIG. 2.
FIG. 6 is a schematic diagram of a test principle in a preferred embodiment of the background schlieren measurement calibration device according to the present invention.
The marks in the figure are respectively:
100. The experimental bin is provided with a plurality of air inlets,
110. The back-plate is provided with a back-plate,
120. The partition board is provided with a plurality of grooves,
130. The first density of the cavities is defined by a first density of cavities,
131. A first pressure control valve is provided to control the pressure of the fluid,
132. A first one of the density detectors is provided with a first sensor,
133. The first point of measurement is taken from the first measuring point,
140. The second density of the cavities is defined by a second density of cavities,
141. A second pressure control valve is provided to control the pressure of the fluid,
142. A second density detector is provided, which is used for detecting the density of the liquid,
143. A second point of measurement is taken at which,
143A the normal pressure measurement point,
143B of the boost measurement point,
The amount of the L-offset,
200. The bracket is arranged on the upper surface of the bracket,
201. The platform is provided with a plurality of grooves,
202. A fixing groove is arranged on the upper surface of the fixing plate,
203. A fixing hoop is arranged on the upper part of the fixing hoop,
300. The pressure control device comprises a pressure control device and a pressure control device,
400. The control box is provided with a control box,
500. Background schlieren apparatus.
Detailed Description
The following description is of one embodiment with reference to the accompanying drawings.
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments, based on the embodiments of the invention, which are apparent to those of ordinary skill in the art without inventive faculty, are intended to be within the scope of the invention. Thus, the following detailed description of the embodiments of the invention, as presented in the figures, is not intended to limit the scope of the invention, as claimed, but is merely representative of selected embodiments of the invention.
It should be noted that: like reference numerals and letters denote like items in the following figures, and thus, once an item is defined in one figure, it may not be further defined and explained in the following figures.
Example 1
See fig. 1-6. The background schlieren measurement calibration device described in this embodiment includes a background schlieren device 500 and a background plate 110. Background schlieren devices belong to existing devices for studying hydrodynamic and flow phenomena, and can visualize refractive phenomena caused by density variations in gases, thereby observing and analyzing variations and structures in flow. Background schlieren equipment measurement is mainly performed by utilizing the principle that light is affected by the density of a transparent medium (in this embodiment, air is used as the transparent medium) to deflect, and because the density inside the transparent medium changes complicated, the measurement result is the equivalent density of the medium through which the light passes, but not the actual measurement density. The algorithm principle adopted by different background schlieren devices is different, and the accuracy of the measured equivalent density cannot be verified under the prior art condition.
The background schlieren apparatus also includes the following several main components:
light source: providing light for illuminating the flow region;
An optical system: including lenses, mirrors, optical filters, etc., for controlling the propagation and collection of light;
An image pickup apparatus: for recording images or video of the flow area.
In the background schlieren system, a background schlieren device, a background plate and an object, namely a study object are also included.
Referring to fig. 1, the background schlieren measurement calibration device of the present embodiment further includes an experiment bin 100, two independent density cavities (a first density cavity 130 and a second density cavity 140 respectively) are symmetrically disposed in the experiment bin 100, and the background schlieren device 500 and the background plate 110 are respectively disposed at two ends of the first density cavity 130 and the second density cavity 140; the first density chamber 130 is fitted with a first density detector 132 and the second density chamber 140 is fitted with a second density detector 142. At least one of the density chambers is fitted with a pressure control valve, in this embodiment the first density chamber 130 is fitted with a first pressure control valve 131 and the second density chamber 140 is fitted with a second pressure control valve 142. The first pressure control valve 131 and the second pressure control valve 141 are connected to the pressure control device 300, and the first pressure control valve 131, the first density detector 132, the second pressure control valve 141, the second density detector 142, and the pressure control device 300 are connected to the control box 400. During the experiment, one of the first density chamber 130 and the second density chamber 140 was maintained in an atmospheric pressure state as a control group; the other density chamber controls the pressure control device 300 and the pressure control valve through the control box 400 to realize the rising or falling of the air pressure in the density chamber as a treatment group. In this embodiment, the pressure control device 300 is an air compressor, and is mainly used for performing a pressurization experiment on air.
In some embodiments, the pressure control device 300 may use a vacuum pump for negative pressure experiments on air.
The first density chamber 130 and the second density chamber 140 are closed chambers, and in particular, remain closed during the experiment, ensuring that the air pressure within the first density chamber 130 and the second density chamber 140 remains stable.
The first pressure control valve 131 and the second pressure control valve 141 are valves for controlling the air to enter or exit the density chamber, and are controlled by the control box 400.
The first density detector 132 is used for measuring the air pressure in the first density cavity 130 in real time, the second density detector 142 is used for measuring the air pressure in the second density cavity 140 in real time, and the air pressure values obtained by the first density detector 132 and the second density detector 142 are used as true values for correcting the detection values of the background schlieren measurement.
Referring to fig. 5 and 6, the experimental bin 100 is cylindrical, made of pressure-resistant glass, and has a partition 120 vertically disposed, and the inside of the experimental bin is symmetrically divided into a first density chamber 130 and a second density chamber 140 by the partition 120, and the partition 120 is perpendicular to the background plate 110. The first density chamber 130 and the second density chamber 140 are arranged in a plane symmetry manner relative to the partition board 120, and meanwhile, the first density detector 132 and the second density detector 142, the first pressure control valve 131 and the second pressure control valve 141 are also arranged in a plane symmetry manner relative to the partition board 120, so that the conditions of the first density chamber 130 and the second density chamber 140 are identical except that the air pressure is different in the experimental process. The symmetrical arrangement is also convenient for obtaining the first measurement point 133 in the first density cavity 130 and the second measurement point 143 in the second density cavity 140, and the measurement point offset under different concentrations can be directly and accurately calculated without complex operation through the mirror image processing of the measurement points, so as to calculate the equivalent density. The first measurement points 133 and the second measurement points 143 are each plural and distributed in a matrix form.
The arrangement of the first density chamber 130 and the second density chamber 140 as reference/treatment sets may be interchanged.
In this embodiment, the first density chamber 130 is used as a reference set and the second density chamber 140 is used as a processing set. Further, the first measurement point 133 is an image obtained at normal pressure, and the first density chamber 130 is always maintained at normal pressure during the experiment. Referring to fig. 6, the second measurement point 143 is an image obtained under a pressure change, the position of which changes according to the pressure change in the second density chamber 140, and in the normal pressure state, the second measurement point 143 is a normal pressure measurement point 143a, and in the pressurized state, the second measurement point 143 is a pressure increase measurement point 143b. The normal pressure measurement point 143a and the first measurement point 133 are plane-symmetric, and in the pressurized state, the relative position of the normal pressure measurement point 143a, that is, the mirror position of the first measurement point 133 can be obtained in the second density chamber 140 by mirror-imaging the image, and then the offset L of the pressure increase measurement point 143b with respect to the normal pressure measurement point 143a is measured, and the air equivalent density is further calculated by the background schlieren device 500.
The pressurizing process is carried out according to a preset gradient, and measurement is carried out after the air pressure is stabilized in each pressurizing process. For example, 10 gradients were set for a duration of 30min at 0.5 atmospheres pressure each time.
At the beginning of an experiment, controlling an air compressor and a pressure control valve through a control box 400 to enable the air pressure in two density cavities to be normal pressure, starting a background schlieren device 500, acquiring a normal pressure measuring point 143a, and recording data of a first density monitor; maintaining the first density chamber 130 at normal pressure, maintaining the first measurement point 133 as a reference; the second density chamber 140 sequentially increases the air pressure according to 0.5 atmosphere, and when the air pressure is increased for 30min each time, the background schlieren device 500 is started again, the pressurizing measurement point 143b is obtained, the offset L is measured, and the air equivalent density rho 1 is calculated through the background schlieren device 500; the density monitor data ρ 2 for each gradient is recorded simultaneously. Comparing ρ 1 and ρ 2, the density error is calculated.
Sequentially pressurizing to obtain multiple groups of data, sequentially depressurizing to obtain multiple groups of data, and calculating variances of all groups of data to obtain density measurement errors of the background schlieren device 500.
According to one embodiment of the background schlieren measurement calibration apparatus of the present invention, the corrected background schlieren device 500 is calibrated with the data of the density monitor as a true value.
In a further embodiment, referring to fig. 2-5, further comprising a bracket 200, the density chamber is fixedly mounted on the bracket 200.
In a further embodiment, referring to fig. 2 to 5, the stand 200 includes a platform 201, a fixing groove 202 is installed above the platform 201, and the experimental bin 100 is horizontally fixed in the fixing groove 202 by a fixing hoop 203.
In a further embodiment, referring to fig. 2 to 5, the air compressor and the control box 400 are both mounted on the stand 200.
Example 2
The background schlieren measurement calibration method described in the present embodiment uses the background schlieren measurement calibration device described in the embodiment to calibrate, and specifically includes the following steps:
The control box 400 controls the air compressor, the first pressure control valve 131 and the second pressure control valve 141 to enable the air pressure in the first density cavity 130 and the air pressure in the second density cavity 140 to be normal pressure, the background schlieren device 500 is started, the background schlieren device 500 is aligned to the background plate 100 to shoot, the first measuring point 133 is obtained on the background plate 110 corresponding to the first density cavity 130, and the second measuring point 143 is obtained on the background plate 110 corresponding to the second density cavity 140. The first measurement point 133 is line symmetric with the second measurement point 143. The first measurement point 133 and the second measurement point 143 are both normal pressure measurements; the second measurement point 143 is now an atmospheric measurement point 143a. While recording the first density detector 132 and the second density monitor 142 data.
Maintaining the air pressure of the first density cavity 130 at normal pressure, controlling the air compressor and the first pressure control valve 131 to increase the air pressure of the second density cavity 140 according to 0.5 atmosphere pressure, waiting for 30min after each pressurization, starting the background schlieren equipment 500 after the air pressure is stabilized, acquiring a first measuring point 133 on a background plate 110 corresponding to the first density cavity 130, and acquiring a pressurization measuring point 143b on a background plate 110 corresponding to the second density cavity 140; the offset L of the boost measurement point 143b is measured with the first measurement point 133 as a mirror reference, and the air equivalent density ρ 1-n is calculated by the background schlieren apparatus 500.
The second density monitor 142 data ρ 2-n is recorded for each gradient of the second density chamber 140 each time the background schlieren apparatus 500 is activated. At the same time, the first density detector 132 is observed to ensure that the air pressure in the first density chamber 130 is normal pressure, and the first measurement point 133 is continuously stable.
And sequentially pressurizing and stabilizing the pressure according to preset gradients to obtain 10 groups of data, after the air pressure in the second density cavity 140 reaches 6 atmospheres, reducing the air pressure by 0.5 atmosphere each time and stabilizing the pressure for 30min each time to obtain data, and finally sequentially depressurizing to normal pressure, wherein ρ 1-n and ρ 2-n are compared, n represents a stabilizing measurement sequence, and the density error under each gradient is calculated.
The variance is calculated from the density error at each gradient to obtain the density measurement error of the background schlieren device 500.
The background schlieren correction device 500 is calibrated with the data of the second density monitor at each gradient as true values.
In the description of the present invention, it should be understood that the terms "first," "second," and the like are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
In the present invention, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present invention can be understood by those of ordinary skill in the art according to the specific circumstances.
The foregoing is merely a preferred embodiment of the present invention, and it should be noted that the above-mentioned preferred embodiment should not be construed as limiting the invention, and the scope of the invention should be defined by the appended claims. It will be apparent to those skilled in the art that various modifications and adaptations can be made without departing from the spirit and scope of the invention, and such modifications and adaptations are intended to be comprehended within the scope of the invention.
Claims (9)
1. The background schlieren measurement calibration device comprises background schlieren equipment and a background plate and is characterized by further comprising an experiment bin, wherein two independent density cavities are symmetrically arranged in the experiment bin, and the background schlieren equipment and the background plate are respectively arranged at two ends of the density cavities; the two density chambers are provided with density detectors, at least one density chamber is provided with a pressure control valve, the pressure control valve is connected with a pressure control device, and the density detectors, the pressure control valve and the pressure control device are connected with a control box; the control box controls the pressure control device and the pressure control valve to enable the air pressure in the two density cavities to be normal pressure, starts background schlieren equipment, obtains normal pressure measuring points and records data of the first density monitor; maintaining a density chamber at normal pressure, and maintaining a first measuring point as a reference; the other density cavity sequentially increases air pressure according to a preset gradient, the background schlieren equipment is started again after the air pressure is increased and stabilized each time, a pressurizing measurement point is obtained, the offset is measured, and the air equivalent density rho 1-n is calculated through the background schlieren equipment; simultaneously recording density monitor data ρ 2-n for each gradient; comparing ρ 1-n with ρ 2-n, calculating a density error; sequentially pressurizing to obtain multiple groups of data, sequentially depressurizing to obtain multiple groups of data, and calculating variances of all groups of data to obtain density measurement errors of the background schlieren equipment.
2. The background schlieren measurement calibration device of claim 1, wherein the interior of the experimental bin is symmetrically divided into a first density chamber and a second density chamber by a partition plate, the partition plate being perpendicular to the background plate.
3. The background schlieren measurement calibration device of claim 2, wherein the experimental bin is cylindrical and the baffle is disposed vertically.
4. A background schlieren measurement calibration device according to any one of claims 1 to 3, further comprising a bracket, wherein the density chamber is fixedly mounted on the bracket.
5. The background schlieren measurement calibration device of claim 4, wherein the support comprises a platform, a fixed slot is installed above the platform, and the experimental bin is horizontally fixed in the fixed slot through a fixed hoop.
6. The background schlieren measurement calibration device of claim 4, wherein the pressure control device and the control box are both mounted on the bracket.
7. The background schlieren measurement calibration device of claim 2, wherein the first density chamber is fitted with a first density detector and a first pressure control valve and the second density chamber is fitted with a second density detector and a second pressure control valve.
8. The background schlieren measurement calibration apparatus of claim 1, wherein the background schlieren correction device is calibrated with the data of the density monitor as a true value.
9. A background schlieren measurement calibration method using the device according to any one of claims 1-8, comprising the steps of:
S1: the control box controls the pressure control device, the first pressure control valve and the second pressure control valve to enable the air pressure in the first density cavity and the air pressure in the second density cavity to be normal pressure, the background schlieren equipment is started, a first measuring point is obtained on a background plate corresponding to the first density cavity, and a second measuring point is obtained on a background plate corresponding to the second density cavity; the first measuring point is in line symmetry with the second measuring point; the first measuring point and the second measuring point are both normal pressure measurement;
S2: maintaining the air pressure of the first density cavity at normal pressure, controlling the pressure control device and the first pressure control valve to increase the air pressure of the second density cavity according to a preset gradient value, starting the background schlieren equipment after the air pressure is stabilized after each pressurizing, acquiring a first measuring point on a background plate corresponding to the first density cavity, and acquiring a pressurizing measuring point on a background plate corresponding to the second density cavity; taking the first measuring point as a symmetrical reference, measuring the offset of the pressurizing measuring point, and calculating the air equivalent density rho 1 through background schlieren equipment;
s3: while the background schlieren device is activated, density monitor data ρ 2 for each gradient of the second density chamber is recorded,
S4: sequentially pressurizing according to preset gradients to obtain multiple groups of data, sequentially depressurizing according to the same gradients to obtain multiple groups of data after reaching the highest pre-examination pressure or the highest tolerance pressure of the second density cavity, comparing rho 1-n with rho 2-n, and calculating density errors under the gradients;
S5: calculating variance according to the density error under each gradient to obtain the density measurement error of the background schlieren equipment;
S6: and calibrating and correcting the background schlieren equipment by taking the data of the second density monitor under each gradient as a true value.
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