A multi-dimensional flow field imaging system and method based on wavelength modulated spectroscopy

Abstract

The application discloses a kind of multi-dimensional flow field imaging system and method based on wavelength modulation spectrum, the system includes: one-dimensional imaging system, for by multiple sets of laser beam expander and collimating lens, the point laser spot of input laser is deformed to obtain multiple sets of strip laser spot, input multiple sets of strip laser spot into the flow field to be measured and obtain two-dimensional image reconstruction information by multiple sets of one-dimensional linear array high-speed infrared camera;Two-dimensional imaging system is used to input laser through the laser beam expander and collimating lens of prearranged arrangement, obtain three-dimensional image reconstruction information by two-dimensional high-speed infrared camera;Computing system is used to calculate multiple sets of two-dimensional image reconstruction information and three-dimensional image reconstruction information, and the state information of the flow field to be measured with spatial resolution is output by speed;State information includes component temperature, component pressure and component concentration.The application realizes the WMS technology from zero-dimensional spatial resolution to one-dimensional, two-dimensional, three-dimensional spatial resolution, realizes the accurate measurement to flow field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of absorption spectroscopy of infrared lasers, and particularly to a multi-dimensional flow field imaging system and method based on wavelength modulation spectroscopy. BACKGROUND

[0002] TDLAS (Tunable Diode Laser Absorption Spectroscopy) is a laser diagnostic technique widely used in the measurement of flow field (especially gaseous flow field) state. TDLAS uses the absorption spectrum of certain molecules at a specific wavelength to quantitatively measure the concentration, temperature, pressure and other parameters of these molecules. The laser used can change the wavelength of the output laser by controlling its input current and other parameters, thereby realizing the measurement of different wavelength absorption spectra.

[0003] The most widely used TDLAS techniques mainly include two types: direct absorption (DA) and wavelength modulation spectroscopy (WMS). Among them, WMS realizes the measurement of flow field in complex environment by modulating the output wavelength of the laser. By using the high-order harmonic of the WMS signal for normalization (WMS-2f / 1f, 2f: second harmonic, 1f: first harmonic), uncalibrated / noisy environment measurement can be realized. The schematic diagram of WMS is shown in Figure 1 The tunable laser (laser 1) emits laser light to penetrate the target gas under the control of the driver signal, and then the WMS measurement original signal is captured by the detector. After subsequent processing, the WMS harmonic signal (WMS-1f, 2f…nf) is obtained. The detector used in WMS is mostly a single-pixel detector, which is mostly used for the measurement of spatially isotropic medium, such as the measurement of gas after reflected shock wave in a shock tube.

[0004] The WMS technology using two or more infrared absorption lines is called WMS dual / multi-line temperature measurement technology. Compared with WMS using a single absorption line for measurement, WMS dual / multi-line temperature measurement technology can directly obtain the temperature parameter by analyzing the WMS signal without knowing the other states (concentration, pressure) of the molecules to be measured in the flow field. WMS-2f / 1f technology and WMS dual / multi-line temperature measurement technology can be used in combination.

[0005] Tomography, also known as tomography and tomographic scanning, is a method of segmenting an object by any penetrable wave. The most well-known application of this technology is the CT (Computed Tomography) device commonly used in medical diagnosis. The basic principle of tomography is to reconstruct the cross section of the observed object by combining the perspective images through perspective from multiple angles

[0006] Current WMS (Wave Streaming Measurement) technology cannot provide spatially resolved measurement results. That is, after the laser is emitted, all portions of the flow field along the laser path are measured, and the results are averaged along the path. Furthermore, most WMS applications use single-point measurement, where the WMS signal is received by a single sensor (lacking two-dimensional resolution, equivalent to a single-pixel camera) after the laser passes through the object under test. To address this issue, some researchers have used multiple laser beams in conjunction with multiple sensors to achieve approximate one-dimensional measurement, such as... Figure 2 As shown. However, due to the physical size limitations of the laser, the optical fiber, and the sensor used, a high one-dimensional spatial resolution cannot be achieved. Figure 2 The beam spacing of the device is approximately 5.6 mm. This approach is closer to "multi-point measurement" than the traditional "one-dimensional measurement".

[0007] For another technique under TDLAS, DA, some researchers have used high-speed two-dimensional cameras to measure methane in flames. However, compared with WMS under TDLAS, DA is more susceptible to interference, requires calibration before measurement, and the measurement system is easily affected by particulate matter in the flow field. This makes it difficult to apply to real-world industrial scenarios and multiphase flow fields such as gas-solid / gas-liquid two-phase flows. Flames with black smoke (carbon soot) and flames used in chemical synthesis are typical examples of multiphase flow fields.

[0008] Other non-laser-based measurement techniques, such as thermocouple temperature measurement, passive infrared radiation temperature measurement, and sampling analysis, have limitations, primarily in low sampling frequency (sampling analysis), influence on the flow field (thermocouple temperature measurement), and low measurement accuracy (passive infrared radiation temperature measurement). Furthermore, these techniques are less likely to provide spatially resolved measurement results. Summary of the Invention

[0009] The present invention aims to at least partially solve one of the technical problems in the related art.

[0010] Therefore, the purpose of this invention is to address the lack of spatial resolution in WMS technology. This invention utilizes a one-dimensional high-speed linear array infrared camera and a two-dimensional high-speed infrared camera, combined with tomography, to achieve spatially resolved measurement of component temperature, concentration, and pressure in a flow field. This elevates WMS technology from zero-dimensional spatial resolution to one-dimensional, two-dimensional, and three-dimensional spatial resolution, enabling precise measurement of the flow field. Furthermore, a multi-dimensional flow field imaging system based on wavelength modulation spectroscopy is proposed.

[0011] Another objective of this invention is to propose a multidimensional flow field imaging method based on wavelength modulation spectrum.

[0012] To achieve the above object, the application provides a wavelength modulation spectrum-based multi-dimensional flow field imaging system, which comprises a one-dimensional imaging system, a two-dimensional imaging system and a computing system.

[0013] The wavelength modulation spectrum-based multi-dimensional flow field imaging system of the application can realize the measurement of the component temperature, concentration and pressure of the flow field with spatial resolution by using the one-dimensional high-speed linear array infrared camera, the two-dimensional high-speed infrared camera and the tomography technology.

[0014] In addition, the wavelength modulation spectrum-based multi-dimensional flow field imaging system according to the above-mentioned embodiment of the application can have the following additional technical features.

[0015] Further, in an embodiment of the application, the imaging system further comprises a plurality of lasers for generating a plurality of lasers with different output wavelength ranges.

[0016] Further, in an embodiment of the application, the imaging system further comprises a laser coupler for coupling the plurality of lasers with different output wavelength ranges to obtain the input laser.

[0017] Further, in an embodiment of the application, the flow field to be measured is arranged to arrange the plurality of strip-shaped laser spots in the same plane.

[0018] Further, in an embodiment of the application, the computing system is further arranged to calculate the component pressure and concentration of the flow field to be measured according to the component temperature of the flow field to be measured obtained by the one-dimensional imaging system.

[0019] Further, in an embodiment of the application, for the one-dimensional linear array high-speed infrared camera, an infrared lens is used to collect the wavelength modulation spectrum signal, or the camera sensor is used to receive the wavelength modulation spectrum signal.

[0020] Further, in one embodiment of the present application, the two-dimensional high-speed infrared camera is used to additionally capture information in the vertical direction.

[0021] Further, in one embodiment of the present application, the two-dimensional imaging system is further used to move the one-dimensional imaging system along a direction perpendicular to the paper surface to obtain tomographic images of different height positions under a preset condition of the flow field to be measured

[0022] To achieve the above object, another aspect of the present application provides a multi-dimensional flow field imaging method based on wavelength modulation spectroscopy, comprising:

[0023] The point laser spot of the input laser is deformed into a plurality of groups of strip-shaped laser spots through a plurality of groups of laser beam expanders and collimating lenses, the plurality of groups of strip-shaped laser spots are input into the flow field to be measured, and two-dimensional image reconstruction information is acquired through a plurality of groups of one-dimensional linear array high-speed infrared cameras; the input laser is input through the laser beam expanders and collimating lenses in a preset arrangement mode, and three-dimensional image reconstruction information is acquired through a two-dimensional high-speed infrared camera; the two-dimensional image reconstruction information and the three-dimensional image reconstruction information are calculated, and state information of the flow field to be measured with spatial resolution is output in real time; wherein the state information includes component temperature, component pressure and component concentration.

[0024] The multi-dimensional flow field imaging method based on wavelength modulation spectroscopy of the embodiment of the present application realizes the measurement of the component temperature, concentration and pressure of the flow field with spatial resolution by using the one-dimensional high-speed linear array infrared camera and the two-dimensional high-speed infrared camera in combination with the tomographic technology.

[0025] The present application has the following advantages:

[0026] 1) The present application can provide two-dimensional cross-section and three-dimensional reconstruction results of the flow field under high noise. The measurement results include the temperature field, pressure field and concentration field of the flow to be measured. In the research field, it can be used for imaging of single-phase and multi-phase flow fields, such as flames generated by combustion (containing soot or not containing soot) and flames used in chemical synthesis. In the engineering industry, it can be used for high-precision real-time monitoring of the state (temperature, pressure, concentration of combustion products / intermediate products) of the combustion chamber, and the measurement results can be used to adjust the combustion state of the industrial burner to achieve more efficient combustion. The present application can effectively monitor the state of the combustion chamber under the condition. The present application realizes high spatial resolution real-time measurement of multi-phase flow fields under complex conditions without disturbing the flow field.

[0027] 2) In the application aspect of the present application, by providing accurate combustion chamber monitoring data, it provides reference for accurate, real-time adjustment of industrial burner parameters, which will help to improve the efficiency of industrial burners. For other industrial multiphase flow fields, such as the exhaust flow of industrial gas turbines, it also has similar effects. In the research field, it can provide researchers with high-precision, high-spatial resolution, non-invasive single / multiphase flow field imaging, which is of great significance to scientific research in many fields such as combustion, chemistry and material synthesis.

[0028] 3) The WMS spatial resolution provided by the present application can be hundreds to thousands of times that of the prior art (the current test uses a camera with a single pixel edge length of about 12.5 microns). At the same time, the use of a single sensor (camera) greatly simplifies the design of the measurement system, which is more conducive to related applications in the industrial field.

[0029] 4) The present application based on WMS has higher accuracy and lower detection limit, can realize non-calibration measurement, and has more accurate measurement results for multiphase flow fields, especially gas-solid / gas-liquid two-phase flow.

[0030] 5) The present application can provide simultaneous, non-invasive measurement of various parameters of the flow field with spatial resolution. The parameters that can be measured include the temperature field, pressure field and component concentration field of the measured flow field.

[0031] 6) The present application can provide real-time measurement results (using a personal workstation level high-performance computer), with a sampling frequency of hundreds of times per second, far exceeding the sampling frequency of physical sampling analysis.

[0032] Additional aspects and advantages of the present application will be partially given in the following description, partially will become obvious from the following description, or will be understood through the practice of the present application. BRIEF DESCRIPTION OF DRAWINGS

[0033] The above and / or additional aspects and advantages of the present application will become apparent and be readily understood from the following description, taken in conjunction with the accompanying drawings, in which:

[0034] Figure 1 is a schematic diagram of WMS technology;

[0035] Figure 2 is a schematic diagram of one-dimensional spatial resolution of WMS based on multiple lasers / laser beam splitting;

[0036] Figure 3 is a structural schematic diagram of a multi-dimensional flow field imaging system based on wavelength modulation spectroscopy according to an embodiment of the present application;

[0037] Figure 4 is a structural schematic diagram of a one-dimensional linear array high-speed infrared camera according to an embodiment of the present application;

[0038] Figure 5 Structure diagram of a two-dimensional high-speed infrared camera according to an embodiment of the present application;

[0039] Figure 6 Flow chart of a wavelength-modulated spectroscopy-based multi-dimensional flow field imaging method according to an embodiment of the present application. DETAILED DESCRIPTION

[0040] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0041] In order to enable those skilled in the art to better understand the present application, the technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings and in combination with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present application.

[0042] A wavelength-modulated spectroscopy-based multi-dimensional flow field imaging system and method according to an embodiment of the present application will be described below with reference to the accompanying drawings.

[0043] Figure 3 Structure diagram of a wavelength-modulated spectroscopy-based multi-dimensional flow field imaging system according to an embodiment of the present application.

[0044] As shown in Figure 3 , the system 10 comprises a one-dimensional imaging system 100, a two-dimensional imaging system 200 and a computing system 300, wherein,

[0045] The one-dimensional imaging system 100 is configured to deform a point laser spot of input laser into a plurality of strip-shaped laser spots through a plurality of laser expanders and collimating lenses, input the plurality of strip-shaped laser spots into a flow field to be measured, and acquire two-dimensional image reconstruction information through a plurality of one-dimensional linear array high-speed infrared cameras.

[0046] The two-dimensional imaging system 200 is configured to input laser through laser expanders and collimating lenses arranged in a preset manner, and acquire three-dimensional image reconstruction information through a two-dimensional high-speed infrared camera.

[0047] The computing system 300 is configured to calculate the two-dimensional image reconstruction information and the three-dimensional image reconstruction information, and output state information of the flow field to be measured with spatial resolution in real time; wherein the state information comprises component temperature, component pressure and component concentration.

[0048] Figure 4The structural schematic diagram of the one-dimensional imaging system 100 of the embodiment of the present application is shown in Figure 4 .

[0049] As an example, the laser 1 and the laser 2 have different output wavelength ranges, the outputs of the laser 1 and the laser 2 are combined into one laser beam through the laser coupler 3, and are deformed from a point laser spot into a strip laser spot through the laser beam expander 4 and the collimating lens 5. The strip laser spot passes through the flow field to be measured 6, and is then received by the one-dimensional linear array high-speed infrared camera 7.

[0050] As an example, Figure 3 The imaging system composed of the laser beam expander 4, the collimating lens 5 and the high-speed infrared camera 7 in the embodiment shows two groups in total, and in actual application, the number of groups can be more than two. It is necessary to ensure that the strip laser spots generated by each imaging system are located in the same plane, and multiple imaging systems can be used to provide clearer two-dimensional cross-section reconstruction of the flow field.

[0051] Further, the laser 1 and the laser 2 are respectively controlled by different controllers to generate the laser required by the WMS technology. Using two lasers with different wavelength ranges can realize the WMS double-line temperature measurement technology.

[0052] Specifically, for the one-dimensional linear array high-speed infrared camera 7 shown in Figure 3 , an infrared lens can be used to collect the WMS signal, or the camera sensor can be directly used to receive the signal. By using the tomography technology to analyze the WMS signals obtained by multiple one-dimensional linear array high-speed infrared cameras 7, Figure 3 the one-dimensional imaging system 100 shown in can obtain the two-dimensional reconstruction information of the flow field at a certain cross-section.

[0053] Figure 5 The structural schematic diagram of the two-dimensional imaging system 200 of the embodiment of the present application is shown in Figure 5 .

[0054] Figure 5 The perspective view of the imaging system when the two-dimensional high-speed infrared camera 7 is used is shown. Compared with Figure 4 , the two-dimensional camera can additionally capture the information in the vertical direction, thereby providing the possibility of three-dimensional reconstruction of the flow field (equivalent to obtaining multiple cross-sections at different height positions along the direction perpendicular to the paper under the condition that the flow field to be measured is stable). Figure 4 The laser beam expander 4 and the collimating lens 5 shown in the embodiment need to be additionally adjusted for the two-dimensional laser beam expansion shown in Figure 5 . As an example, the laser beam expander 4 and the collimating lens 5 given in the embodiment Figure 5 are schematic diagrams, and their shapes do not represent the final functions. Figure 5

[0055] Finally, the raw data measured by the one-dimensional imaging system 100 and the two-dimensional imaging system 200 of the multi-dimensional WMS imaging system is processed by the high-performance computer, and the temperature, pressure and concentration of the flow field are output at a near real-time speed. The temperature field is directly obtained based on the WMS dual-line / multi-line temperature measurement technology, and the pressure and the concentration of the measured components are obtained based on the WMS through simulation calculation based on the measured temperature field.

[0056] According to the multi-dimensional flow field imaging system based on wavelength modulation spectroscopy, the component temperature, concentration and pressure of the flow field with spatial resolution are measured by using the one-dimensional high-speed linear array infrared camera and the two-dimensional high-speed infrared camera in combination with the tomography technology. Thus, the WMS technology is improved from zero-dimensional spatial resolution to one-dimensional, two-dimensional and three-dimensional spatial resolution, and the accurate measurement of the flow field is realized.

[0057] In order to realize the above-mentioned embodiments, as shown in the accompanying drawings, the embodiment further provides a multi-dimensional flow field imaging method based on wavelength modulation spectroscopy, comprising: Figure 6

[0058] S1, the point laser spot of the input laser is deformed into a plurality of strip-shaped laser spots by a plurality of laser beam expanders and collimating lenses, the plurality of strip-shaped laser spots are input into the flow field to be measured, and two-dimensional image reconstruction information is acquired by a plurality of one-dimensional linear array high-speed infrared cameras;

[0059] S2, the input laser is input through the laser beam expander and the collimating lens in a preset arrangement mode, and three-dimensional image reconstruction information is acquired by a two-dimensional high-speed infrared camera;

[0060] S3, the two-dimensional image reconstruction information and the three-dimensional image reconstruction information are calculated, and the state information of the flow field to be measured with spatial resolution is output at a real-time speed; wherein the state information includes the component temperature, the component pressure and the component concentration.

[0061] Further, the above-mentioned method further comprises: acquiring a plurality of lasers with different output wavelength ranges.

[0062] Further, the above-mentioned method further comprises: coupling a plurality of lasers with different output wavelength ranges to obtain the input laser.

[0063] Further, the above-mentioned method further comprises: arranging the plurality of strip-shaped laser spots in the same plane of the flow field to be measured.

[0064] Further, the above-mentioned method further comprises: calculating the component pressure and the component concentration of the flow field to be measured at a real-time speed according to the measured component temperature of the flow field to be measured.

[0065] ​Further, for one-dimensional linear array high-speed infrared camera, wavelength modulation spectrum signal is collected by using infrared lens, or wavelength modulation spectrum signal is received by using camera sensor.

[0066] Further, the above method further comprises: capturing information in the vertical direction by using a two-dimensional high-speed infrared camera.

[0067] According to the multi-dimensional flow field imaging method based on wavelength modulation spectrum, the component temperature, concentration and pressure of the flow field with spatial resolution are measured by using one-dimensional high-speed linear array infrared camera, two-dimensional high-speed infrared camera and combining with tomography technology.

[0068] In addition, the terms "first", "second", "third", etc. are used herein merely to describe various corresponding components and do not imply or suggest any relative importance or a number of the corresponding components. Thus, the features with "first", "second", "third", etc. can explicitly or implicitly include at least one of the features. In the description of the present application, the meaning of "a plurality of" is at least two, for example, two, three, etc., unless otherwise specifically limited.

[0069] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in any one or more embodiments or examples. In addition, the different embodiments or examples described in the present application and the features of the different embodiments or examples can be combined and combined by those skilled in the art without contradiction.

[0070] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and should not be construed as limiting the present application, and those skilled in the art can make changes, modifications, replacements and variations to the above embodiments within the scope of the present application.

Claims

1. A multi-dimensional flow field imaging system based on wavelength modulated spectroscopy, characterized in that, The imaging system comprises a one-dimensional imaging system, a two-dimensional imaging system and a computing system, wherein, The one-dimensional imaging system is configured to deform point laser spots of input laser into a plurality of strip-shaped laser spots through a plurality of laser expanders and collimating lenses, input the plurality of strip-shaped laser spots into a flow field to be measured, and acquire two-dimensional image reconstruction information through a plurality of one-dimensional linear array high-speed infrared cameras; The two-dimensional imaging system is configured to input the input laser through laser expanders and collimating lenses in a preset arrangement mode, and acquire three-dimensional image reconstruction information through a two-dimensional high-speed infrared camera; The computing system is configured to calculate the two-dimensional image reconstruction information and the three-dimensional image reconstruction information, and output state information of the flow field to be measured with spatial resolution through real-time speed; wherein the state information comprises component temperature, component pressure and component concentration; The imaging system further comprises a plurality of lasers configured to generate a plurality of lasers with different output wavelength ranges; The imaging system further comprises a laser coupler configured to couple the plurality of lasers with different output wavelength ranges to obtain the input laser; The flow field to be measured is configured to arrange the plurality of strip-shaped laser spots in the same plane; For the one-dimensional linear array high-speed infrared camera, an infrared lens is used to collect wavelength modulation spectrum signals, or a camera sensor is used to receive the wavelength modulation spectrum signals; The two-dimensional high-speed infrared camera is configured to additionally capture information in a vertical direction; The two-dimensional imaging system is further configured to move the one-dimensional imaging system along a direction perpendicular to the paper plane to obtain a plurality of tomographies at different height positions under a preset condition of the flow field to be measured; The computing system is further configured to calculate the component pressure and the component concentration of the flow field to be measured through real-time speed according to the component temperature of the flow field to be measured obtained by the one-dimensional imaging system.

2. A method of multi-dimensional flow field imaging based on wavelength modulated spectroscopy, characterized in that The method comprises the following steps: deforming point laser spots of input laser into a plurality of strip-shaped laser spots through a plurality of laser expanders and collimating lenses, inputting the plurality of strip-shaped laser spots into a flow field to be measured, and acquiring two-dimensional image reconstruction information through a plurality of one-dimensional linear array high-speed infrared cameras; inputting the input laser through laser expanders and collimating lenses in a preset arrangement mode, and acquiring three-dimensional image reconstruction information through a two-dimensional high-speed infrared camera; calculating the two-dimensional image reconstruction information and the three-dimensional image reconstruction information, and outputting state information of the flow field to be measured with spatial resolution through real-time speed; wherein the state information comprises component temperature, component pressure and component concentration; The method further comprises acquiring a plurality of lasers with different output wavelength ranges; The method further comprises coupling the plurality of lasers with different output wavelength ranges to obtain the input laser; The method further comprises arranging the plurality of strip-shaped laser spots in the same plane of the flow field to be measured; The outputting of the state information of the flow field to be measured with spatial resolution through real-time speed is specifically: calculating the component pressure and the component concentration of the flow field to be measured through real-time speed according to the component temperature of the flow field to be measured measured; For the one-dimensional linear array high-speed infrared camera, an infrared lens is used to collect a wavelength modulation spectrum signal, or the wavelength modulation spectrum signal is received by a camera sensor; The method further comprises: capturing information in a vertical direction by the two-dimensional high-speed infrared camera.

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