Hydrogen-related system safety detection method and system based on double-view background schlieren

Abstract

The invention relates to the technical field of hydrogen safety visual detection, and discloses a hydrogen-related system safety detection method and system based on double-view background schlieren. According to the method, two light field cameras are used for collecting real-time background images of a to-be-measured flow field above a hydrogen related system under double visual angles; obtaining background spot displacement vector data based on the real-time background image; converting the background spot displacement vector data, and calculating to obtain two-dimensional plane gas concentration distribution data under each visual angle based on the refractive index of the optical fiber; superposing the two-dimensional plane gas concentration distribution data under the double view angles into three-dimensional gas concentration distribution field data based on Radon transformation; and hydrogen leakage detection is carried out on the hydrogen related system according to the three-dimensional gas concentration distribution field data. The gas concentration is calibrated through the light refractive index, and the method has the advantages of being low in delay, high in precision and capable of accurately positioning the leakage position.

Description

Technical Field

[0001] The present invention relates to the technical field of hydrogen safety visualization detection, and in particular to a hydrogen-related system safety detection method and system based on dual-viewing angle background schlieren. Background Art

[0002] Hydrogen is extremely flammable, explosive, colorless and odorless. Once a hydrogen pipeline in a hydrogen-related system leaks, the leak location is highly random, and the leak concentration is not easy to detect quickly. Currently, the commonly used gas detection method is basically a contact measurement method. The measurement delay of contact probes is generally 5-20s, and the detection of hydrogen concentration cannot guarantee high accuracy. In addition, contact probes cannot quickly and accurately locate the leak location, and once hydrogen leaks and is ignited, it is very easy to damage the probe. Therefore, current research is mainly focused on non-contact measurement methods that can quickly detect hydrogen and have high accuracy.

[0003] Background Schlieren (BOS) technology is an image-based, large-field-of-view, non-contact quantitative flow field testing technology. This technology combines particle tracer image processing technology (PIV), computer image processing technology and Schlieren technology. The distorted image is compared with the reference image, and the light deflection and density distribution of the observation area are obtained by calculating the offset of the corresponding pixels. This technology not only continues the high sensitivity and high precision of Schlieren technology for density field analysis, but also can observe a very large field of view like PIV technology. Therefore, the technology is widely used in many research fields such as supersonic flow, combustion environment, plasma flow, etc.

[0004] At present, for three-dimensional variable density flow, three-dimensional BOS measurement technology based on multi-projection tomographic reconstruction is often used. Tomographic BOS uses multiple cameras to obtain background displacement information at multiple angles, and the three-dimensional refractive index and density distribution can be obtained through the tomographic reconstruction algorithm, but it is expensive and the system layout is complex. The number of cameras, camera distribution and camera shooting angle will greatly affect the measurement effect. Image fiber BOS uses image fiber instead of camera, and places the image fiber that can capture images at any projection angle in front of the camera, so that a single camera can capture multiple instantaneous images at the same time. The system is low-cost, but its spatial image resolution is worse than that of traditional BOS and the system layout is complex. The emergence of light field BOS makes single-view volume imaging possible. A microlens array (MLA) is placed in front of a camera to replace multiple cameras. Compared with other methods, the light field BOS system is simple, but the image reconstructed by a single light field camera has the problem of lower axial resolution than lateral resolution, which makes three-dimensional high-resolution flow field measurement very difficult. In addition, in the non-contact measurement of gas concentration, the post-processing of images by three-dimensional tomography technology is quite cumbersome, and the calibration method of gas concentration by image grayscale has high limitations, making it very difficult to apply in actual scenarios. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a hydrogen-related system safety detection method and system based on dual-perspective background schlieren. The present invention calibrates the gas concentration by the refractive index of light, and has the advantages of low latency, high precision, and accurate positioning of the leakage position.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] The present invention discloses a hydrogen-related system safety detection method based on dual-viewing angle background schlieren, comprising steps S1 to S5.

[0008] S1. Use two light field cameras to collect real-time background images of the flow field to be measured above the hydrogen-related system under dual viewing angles; wherein the two light field cameras are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., on the adjacent two sides, and are respectively facing two background plates arranged opposite to the flow field to be measured; the two background plates are both perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix.

[0009] S2. Acquire background spot displacement vector data based on the real-time background image.

[0010] S3. Convert the background spot displacement vector data, and obtain the two-dimensional plane gas concentration distribution data at each viewing angle based on the optical fiber refractive index.

[0011] S4. Based on Radon transform, the two-dimensional plane gas concentration distribution data under dual perspectives are superimposed into three-dimensional gas concentration distribution field data.

[0012] S5. Conduct hydrogen leakage detection on hydrogen-related systems based on three-dimensional gas concentration distribution field data.

[0013] As a further improvement of the above solution, in step S2, the process of acquiring the background spot displacement vector data includes:

[0014] The real-time background image of each viewing angle is Fourier transformed with the corresponding pre-stored leakage-free background image, and the vector displacement value between pixels is identified using the cross-correlation algorithm. By moving the window, the background spot displacement vector data of the entire two-dimensional plane of each viewing angle is obtained.

[0015] As a further improvement of the above solution, step S3 includes the following specific steps:

[0016] S31. Calculate the gas density ρ corresponding to each pixel in the real-time background image through the background spot displacement vector data gas :

[0017]

[0018] In the formula, ρ air is the atmospheric density; K is the Gladstone-Dale coefficient; Δs is the displacement of any background spot pixel, and s is the background point pixel size;

[0019] S32. Calculate the gas density as ρ air The refractive index of the light in the ambient gas is n gas :

[0020] n gas =1+Kρ gas

[0021] S33. The refractive index of the light n gas Calculate the corresponding gas mole fraction X:

[0022]

[0023] Where n air is the atmospheric refractive index; T and T amb is the temperature coefficient, T is 1.15, T amb The value is 0.95;

[0024] S34. Obtain the gas concentration c corresponding to each pixel in the real-time background image according to the gas mole fraction X, thereby obtaining the two-dimensional plane gas concentration distribution data at each viewing angle according to the gas concentrations corresponding to all pixels in the real-time background image; wherein c=X·M, M is the molar mass of hydrogen.

[0025] As a further improvement of the above scheme, in step S4, the two-dimensional plane gas concentration data of a specific single pixel under each viewing angle is decomposed into an n-term arithmetic progression with 1 as the arithmetic progression based on Radon transform, each item of the sequence is defined as a concentration eigenvalue, and the concentration eigenvalues ​​are numbered to obtain n groups of concentration eigenvalue data at each pixel point in the viewing direction; the concentration eigenvalues ​​at the same pixel point position in the two viewing directions are compared to locate the two concentration eigenvalues ​​at each position in the space, and the average value of the two concentration eigenvalues ​​is taken to obtain the gas reconstruction concentration at the position, thereby obtaining the gas concentration value corresponding to each position of the flow field to be measured, and constructing the three-dimensional gas concentration distribution field data.

[0026] As a further improvement of the above solution, in step S5, the hydrogen leakage source is located according to the highest concentration position in the three-dimensional gas concentration distribution field data.

[0027] As a further improvement of the above scheme, in step S5, when it is determined that there is hydrogen leakage in the hydrogen-related system, the highest concentration position of the gas concentration field is marked, and an alarm signal containing the leakage source location information is sent to the remote interactive terminal accordingly.

[0028] The present invention also discloses a hydrogen-related system safety detection system based on dual-viewing angle background schlieren, which applies the hydrogen-related system safety detection method based on dual-viewing angle background schlieren as described above; the safety detection system includes: an image acquisition module and a data processing module.

[0029] The image acquisition module is used to acquire real-time background images of the flow field to be measured above the hydrogen-related system under dual viewing angles; the image acquisition module includes two light field cameras, which are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., at two adjacent sides, and respectively face two background plates arranged opposite to the flow field to be measured; the two background plates are both perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix;

[0030] The data processing module is used to obtain background spot displacement vector data based on the real-time background image; convert the background spot displacement vector data to obtain two-dimensional plane gas concentration distribution data under each viewing angle; superimpose the two-dimensional plane gas concentration distribution data under dual viewing angles into three-dimensional gas concentration distribution field data based on Radon transformation; and perform hydrogen leakage detection on hydrogen-related systems according to the three-dimensional gas concentration distribution field data.

[0031] As a further improvement of the above scheme, the two background plates have fixed and mutually matched pixel positions, shape parameters and inverse scale parameters; and the distance between each light field camera and the corresponding background plate is adjustable.

[0032] Compared with the prior art, the present invention has the following beneficial effects:

[0033] Compared with the traditional sensor contact measurement, the present invention has the advantages of high precision, low latency and wide test range. Compared with the existing three-dimensional flow field test methods such as tomographic light field background schlieren, this new dual-view schlieren technology uses the image superposition of the front view and the side view to improve the axial resolution of light field imaging. The three-dimensional concentration field of hydrogen is quickly acquired through the dual-view image acquisition method, which reduces the cost of the three-dimensional background schlieren system and simplifies the operating system.

[0034] In addition, the present invention proposes a calibration relationship between background spot offset and gas concentration, which is simpler than the calibration relationship involved in traditional three-dimensional flow field testing, significantly reducing the amount of post-processing calculations in the system. Therefore, the experimental device of the present invention is simpler and the gas concentration detection is faster, which can accurately and quickly locate the leakage position of the hydrogen-related device after leakage, and provide data support for the setting of hydrogen discharge action after leakage in the hydrogen-related system. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a flow chart of the hydrogen-related system safety detection method based on dual-viewing background schlieren in Example 1 of the present invention.

[0036] Figure 2 Schematic diagram of the arrangement of the light field camera and the background plate in Embodiment 1 of the present invention.

[0037] Figure 3 Background diagram of the Schlieren technique. DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example 1

[0040] See also Figure 1 This embodiment provides a hydrogen-related system safety detection method based on dual-view background schlieren, including steps S1 to S5.

[0041] S1. Use two light field cameras 1 to collect real-time background images of the flow field to be measured above the hydrogen-related system 3 under dual viewing angles; wherein the two light field cameras 1 are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., on the adjacent two sides, and are respectively facing two background plates 2 arranged opposite to the flow field to be measured; the two background plates 2 are both perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix.

[0042] See also Figures 2 to 3 In step S1, the two background plates 2 have fixed and mutually matched pixel positions, shape parameters and inverse scale parameters; the distance between each light field camera 1 and the corresponding background plate 2 can be adjusted to be close or far. When collecting images, the high-speed camera and the background plate 2 are fixed to ensure that there is no slight shaking of the background during the shooting process, and the shooting angle of the camera is kept absolutely vertical to the background plate 2.

[0043] S2. Acquire background spot displacement vector data based on the real-time background image.

[0044] In step S2, the process of acquiring the background spot displacement vector data includes:

[0045] The real-time background image of each viewing angle is Fourier transformed with the corresponding pre-stored leakage-free background image, and the pre-stored leakage-free background image and the real-time background image are cross-correlated analyzed using a particle high-speed velocimetry algorithm based on MATLAB to identify the vector displacement value between pixel points. By moving the window, the background spot displacement vector data of the entire two-dimensional plane of each viewing angle is obtained.

[0046] In this embodiment, the method for collecting the pre-stored leakage-free background image is: when the hydrogen-related system 3 is not running, the camera is turned on to keep it in the collected image at all times, and the airflow-free background image collected simultaneously from the main perspective and the side perspective is saved and stored in the system.

[0047] S3. Convert the background spot displacement vector data, and obtain the two-dimensional plane gas concentration distribution data at each viewing angle based on the optical fiber refractive index.

[0048] Step S3 includes the following specific steps:

[0049] S31. Calculate the gas density ρ corresponding to each pixel in the real-time background image through the background spot displacement vector data gas :

[0050]

[0051] In the formula, ρ air is the atmospheric density; K is the Gladstone-Dale coefficient; Δs is the displacement of any background spot pixel, and s is the background point pixel size;

[0052] S32. Calculate the gas density as ρ air The refractive index of the light in the ambient gas is n gas :

[0053] n gas =1+Kρ gas

[0054] S33. The refractive index of the light n gas Calculate the corresponding gas mole fraction X:

[0055]

[0056] Where n air is the atmospheric refractive index; T and T amb is the temperature coefficient, T is 1.15, T amb The value is 0.95;

[0057] S34. Obtain the gas concentration c corresponding to each pixel in the real-time background image according to the gas mole fraction X, thereby obtaining the two-dimensional plane gas concentration distribution data at each viewing angle according to the gas concentrations corresponding to all pixels in the real-time background image; wherein c=X·M, M is the molar mass of hydrogen.

[0058] S4. Based on Radon transform, the two-dimensional plane gas concentration distribution data under dual perspectives are superimposed into three-dimensional gas concentration distribution field data.

[0059] In step S4, the two-dimensional plane gas concentration data of a specific single pixel under each viewing angle is decomposed into an n-term arithmetic progression with 1 as the arithmetic progression based on Radon transform, each item of the sequence is defined as a concentration eigenvalue, and the concentration eigenvalues ​​are numbered to obtain n groups of concentration eigenvalue data at each pixel point in the viewing direction; the concentration eigenvalues ​​at the same pixel point position in the two viewing directions are compared to locate the two concentration eigenvalues ​​at each position in the space, and the average of the two concentration eigenvalues ​​is taken to obtain the gas reconstruction concentration at the position, thereby obtaining the gas concentration value corresponding to each position of the flow field to be measured, and constructing the three-dimensional gas concentration distribution field data.

[0060] S5. Perform hydrogen leakage detection on the hydrogen-related system 3 according to the three-dimensional gas concentration distribution field data.

[0061] In step S5, the hydrogen leakage source is located according to the highest concentration position in the three-dimensional gas concentration distribution field data. When it is determined that there is hydrogen leakage in the hydrogen-related system, the highest concentration position of the gas concentration field is marked, and an alarm signal containing the leakage source location information is sent to the remote interactive terminal. The interactive terminal can be a mobile phone, a laptop computer, a tablet computer or other terminal device that can interact with relevant personnel.

[0062] Example 2

[0063] This embodiment provides a hydrogen-related system safety detection system based on dual-viewing background schlieren, and applies the hydrogen-related system safety detection method based on dual-viewing background schlieren described in Example 1; the safety detection system includes: an image acquisition module and a data processing module.

[0064] The image acquisition module is used to collect real-time background images of the flow field to be measured above the hydrogen-related system under dual viewing angles; the image acquisition module includes two light field cameras, which are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., on the adjacent two sides, and are respectively facing two background plates arranged opposite to the flow field to be measured; the two background plates are both perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix.

[0065] The two background plates have fixed and mutually matched pixel positions, shape parameters and inverse scale parameters; and the distance between each light field camera and the corresponding background plate is adjustable.

[0066] The data processing module is used to obtain background spot displacement vector data based on the real-time background image; convert the background spot displacement vector data to obtain two-dimensional plane gas concentration distribution data under each viewing angle; superimpose the two-dimensional plane gas concentration distribution data under dual viewing angles into three-dimensional gas concentration distribution field data based on Radon transformation; and perform hydrogen leakage detection on hydrogen-related systems according to the three-dimensional gas concentration distribution field data.

[0067] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A hydrogen-related system safety detection method based on dual-viewing background schlieren, characterized in that: include: S1. Use two light field cameras to collect real-time background images of the flow field to be measured above the hydrogen-related system under dual viewing angles; wherein the two light field cameras are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., at the adjacent two sides, and are respectively facing two background plates arranged opposite to the flow field to be measured; the two background plates are perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix; S2. Acquire background spot displacement vector data based on the real-time background image; S3. Convert the background spot displacement vector data, and obtain the two-dimensional plane gas concentration distribution data at each viewing angle based on the optical fiber refractive index; S4. Based on Radon transform, the two-dimensional plane gas concentration distribution data under dual viewing angles are superimposed into three-dimensional gas concentration distribution field data; S5. Conduct hydrogen leakage detection on hydrogen-related systems based on three-dimensional gas concentration distribution field data.

2. The hydrogen-related system safety detection method based on dual-viewing background schlieren according to claim 1 is characterized in that: In step S2, the process of acquiring the background spot displacement vector data includes: The real-time background image of each viewing angle is Fourier transformed with the corresponding pre-stored leakage-free background image, and the vector displacement value between pixels is identified using the cross-correlation algorithm. By moving the window, the background spot displacement vector data of the entire two-dimensional plane of each viewing angle is obtained.

3. The hydrogen-related system safety detection method based on dual-viewing background schlieren according to claim 1 is characterized in that: Step S3 includes the following specific steps: S31. Calculate the gas density ρ corresponding to each pixel in the real-time background image through the background spot displacement vector data gas : In the formula, ρ air is the atmospheric density; K is the Gladstone-Dale coefficient; Δs is the displacement of any background spot pixel, and s is the background point pixel size; S32. Calculate the gas density as ρ air The refractive index of the light in the ambient gas is n gas : n gas =1+Kρ gas S33. The refractive index of the light n gas Calculate the corresponding gas mole fraction X: Where n air is the atmospheric refractive index; T and T amb is the temperature coefficient, T is 1.15, T amb The value is 0.95; S34. Obtain the gas concentration c corresponding to each pixel in the real-time background image according to the gas mole fraction X, thereby obtaining the two-dimensional plane gas concentration distribution data at each viewing angle according to the gas concentrations corresponding to all pixels in the real-time background image; wherein c=X·M, M is the molar mass of hydrogen.

4. The hydrogen-related system safety detection method based on dual-viewing background schlieren according to claim 1 is characterized in that: In step S4, the two-dimensional plane gas concentration data of a specific single pixel under each viewing angle is decomposed into an n-term arithmetic progression with 1 as the arithmetic progression based on Radon transform, each item of the sequence is defined as a concentration eigenvalue, and the concentration eigenvalues ​​are numbered to obtain n groups of concentration eigenvalue data at each pixel point in the viewing direction; the concentration eigenvalues ​​at the same pixel point position in the two viewing directions are compared to locate the two concentration eigenvalues ​​at each position in the space, and the average of the two concentration eigenvalues ​​is taken to obtain the gas reconstruction concentration at the position, thereby obtaining the gas concentration value corresponding to each position of the flow field to be measured, and constructing the three-dimensional gas concentration distribution field data.

5. The hydrogen-related system safety detection method based on dual-viewing background schlieren according to claim 1 is characterized in that: In step S5, the hydrogen leakage source is located according to the highest concentration position in the three-dimensional gas concentration distribution field data.

6. The hydrogen-related system safety detection method based on dual-viewing background schlieren according to claim 1 is characterized in that: In step S5, when it is determined that there is hydrogen leakage in the hydrogen-related system, the highest concentration position of the gas concentration field is marked, and an alarm signal containing the leakage source position information is sent to the remote interactive terminal accordingly.

7. A hydrogen-related system safety detection system based on dual-viewing background schlieren, characterized in that: The method for safety detection of hydrogen-related systems based on dual-viewing background schlieren as claimed in any one of claims 1 to 6 is applied; the safety detection system comprises: An image acquisition module is used to acquire real-time background images of the flow field to be measured above the hydrogen-related system under dual viewing angles; the image acquisition module comprises two light field cameras, which are deployed at the front viewing angle and the side viewing angle of the flow field to be measured, i.e., at two adjacent sides, and respectively face two background plates arranged opposite to the flow field to be measured; the two background plates are both perpendicular to the horizontal plane, perpendicular to each other and have a random dot matrix; A data processing module is used to obtain background spot displacement vector data based on the real-time background image; convert the background spot displacement vector data to obtain two-dimensional plane gas concentration distribution data under each viewing angle; superimpose the two-dimensional plane gas concentration distribution data under two viewing angles into three-dimensional gas concentration distribution field data based on Radon transformation; and perform hydrogen leakage detection on hydrogen-related systems according to the three-dimensional gas concentration distribution field data.

8. The hydrogen-related system safety detection system based on dual-viewing background schlieren according to claim 7 is characterized in that: The two background plates have fixed and matched pixel positions, shape parameters and inverse scale parameters; the distance between each light field camera and the corresponding background plate is adjustable.

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