CN113484533A - Visible light-infrared light coupling flow field measurement system based on image processing - Google Patents
Visible light-infrared light coupling flow field measurement system based on image processing Download PDFInfo
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Abstract
The invention discloses a visible light-infrared light coupling flow field measuring system based on image processing, which comprises a testing section, an imaging component and an image processing module, wherein the testing section comprises a testing section body and a measuring section body; the top of test section is equipped with light-transmitting window, and the flow field imaging face in the test section is lighted via light-transmitting window to the laser film light, and the shaping subassembly is including all focusing on first camera and the second camera in flow field imaging face: a first optical filter is arranged on one side of the test section, so that a first camera can acquire a flow field visible light image; a second optical filter is arranged on the other side of the test section, so that a second camera acquires an infrared image of the flow field; the image processing module completes full measurement and collection of flow field information based on the synchronously acquired flow field visible light image and flow field infrared light image. The information of a speed field and the information of a temperature field are synchronously measured by utilizing a visible light-infrared light image, and the information of a pressure field and a density field is obtained by processing, so that the synchronous acquisition of all basic information of an experimental flow field is realized, and the problem of incomplete measurement of the flow field information in the experiment is solved.
Description
Technical Field
The invention relates to the technical field of flow field measurement, in particular to a visible light-infrared light coupling flow field measurement system based on image processing.
Background
At present, the visible light measurement technology aiming at the field of gas fluid mainly comprises the technologies of PIV (particle Image velocimetry), striae, PLIF (planar Laser Induced fluorescence) and the like, wherein the PIV technology obtains quantitative results of flow field flow velocity, turbulence and the like through Image cross-correlation analysis containing trace particles; the schlieren technique reflects density gradient by using the refractive index difference of visible light or laser to obtain flow field characteristics such as flow field shock wave, expansion wave, separation zone and the like; PLIF technology utilizes laser-induced fluorescence to measure components (e.g., PAHs, OH, CO, CH, etc.), temperature, and free radical concentration distribution of measurement objects such as combustion processes, ionization processes, etc. The measurement aiming at invisible light mainly takes infrared imaging, and the flow field temperature is measured by utilizing the thermal infrared spontaneous radiation of gas, liquid and solid.
There is a patent "synchronous measuring device for deformation field and temperature field of orthogonal cutting process" (publication number: CN112518423A) for coupling measurement of visible light and invisible light, which obtains the deformation field and temperature field of the cutting process by processing and reconstructing infrared image and visible light image. However, the scheme is mainly used in the solid cutting process and is not suitable for comprehensive analysis of the flow field.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a visible light-infrared light coupling flow field measurement system based on image processing, which utilizes a visible light-infrared light image to synchronously measure information of a speed field and a temperature field and processes the information to obtain information of a pressure field and a density field, thereby realizing the synchronous acquisition of all basic information of an experimental flow field and solving the problem of incomplete measurement of the flow field information in the experiment.
In order to achieve the above object, the present invention provides a visible light-infrared light coupling flow field measurement system based on image processing, which includes a test section, a laser component, an imaging component and an image processing module, wherein the test section has a flow field with trace particles;
the top of the testing section is provided with a light-transmitting window, the laser assembly is used for generating laser sheet light, and the laser sheet light illuminates a flow field imaging surface in the testing section through the light-transmitting window;
the molding assembly comprises a first camera and a second camera, the first camera and the second camera focus on the flow field imaging surface:
a first optical filter which can only pass visible light is arranged on one side of the test section, and the first optical filter is positioned between the flow field imaging surface and a lens of the first camera, so that the first camera can acquire a flow field visible light image;
a second optical filter which only can pass through infrared light is arranged on the other side of the test section, and the second optical filter is positioned between the flow field imaging surface and a lens of the second camera, so that the second camera can acquire a flow field infrared light image;
the image processing module is in communication connection with the first camera and the second camera to complete full measurement and collection of flow field information based on the flow field visible light image and the flow field infrared light image, wherein the flow field visible light image and the flow field infrared light image are acquired in time synchronization.
In one embodiment, the image processing module performs a full measurement and acquisition process of flow field information by:
obtaining a velocity field and a temperature field of the flow field based on the flow field visible light image and the flow field infrared light image;
obtaining a Mach number field based on a velocity field and a temperature field of a flow field:
Ma＝v/c
in the formula, Ma is a Mach number field of a flow field, v is a velocity field of the flow field, c is local sound velocity, gamma is an adiabatic index, R is a gas constant, and T is a temperature field of the flow field;
obtaining a static pressure distribution field based on a Mach number field of a flow field:
wherein P is the static pressure distribution field of the flow field, P0Is the total pressure of the fluid in the flow field;
obtaining a density field based on a static pressure distribution field and a temperature field of a flow field:
wherein rho is the density field of the flow field, and M is the unit molecular mass.
In one embodiment, the first filter is quartz optical glass.
In one embodiment, the second filter is coated germanium glass.
In one embodiment, the method further comprises the following steps:
a fluid generation assembly for generating a fluid;
the particle generation assembly is connected with the fluid generation assembly and is used for accelerating pressure reduction of the fluid so as to reduce the temperature and desublimate the fluid to generate micron-scale or nanometer-scale ice crystal tracer particles;
the particle generating assembly is coupled to the test section to deliver a fluid with ice crystal tracer particles into the test section.
In one embodiment, the particle generating assembly comprises a supersonic nozzle, an injection quenching section and a particle generating and mixing section;
the fluid generation assembly comprises a first pressure storage tank with high-pressure gas, and the output end of the first pressure storage tank is communicated with the contraction end of the supersonic velocity spray pipe so as to input high-pressure fluid into the supersonic velocity spray pipe, so that the high-pressure fluid is converted into supersonic velocity low-temperature jet flow after being accelerated and depressurized and is output through the expansion end of the supersonic velocity spray pipe;
the input end of the injection quenching section is communicated with the expansion end of the supersonic velocity spray pipe, and the input end of the injection quenching section is provided with an air injection port for injecting air to the injection quenching section;
the input end of the particle generation mixing section is communicated with the output end of the injection quenching section and is used for mixing air with the supersonic low-temperature jet flow so that water vapor in the air is quenched to generate the ice crystal tracing particles, and the output end of the particle generation mixing section is communicated with the input end of the testing section.
In one embodiment, the particle generation assembly comprises a supersonic nozzle;
the fluid generation assembly comprises a second pressure storage tank and a third pressure storage tank, wherein the second pressure storage tank is internally provided with high-pressure easily-desublimed gas, and the third pressure storage tank is internally provided with high-pressure dispersed gas;
the output end of the second pressure storage tank and the output end of the third pressure storage tank are communicated with the input end of the supersonic velocity spray pipe, so that the easily desublimated gas and the dispersed gas are subjected to accelerated depressurization in the supersonic velocity spray pipe to generate rapid cooling, and the easily desublimated gas is spontaneously condensed to generate the ice crystal tracer particles;
and the output end of the supersonic velocity spray pipe is communicated with the input end of the test section.
In one embodiment, the desublimating gas includes, but is not limited to, CO2And freon.
The visible light-infrared light coupling flow field measuring system based on image processing has the following beneficial technical effects:
1) the invention is not only suitable for the field of experimental fluid, but also can be expanded to the field of solid, and has wide application range;
2) the invention can synchronously acquire the speed field and the temperature field, and then couple and calculate the speed field and the temperature field to obtain the pressure field and the density field, so as to obtain all key information in the flow field and provide a solid foundation for subsequent research.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the structures shown in the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a visible light-infrared light coupling flow field measurement system based on image processing in an embodiment of the present invention;
FIG. 2 is a schematic diagram of a full measurement acquisition process of flow field information in an embodiment of the present invention;
FIG. 3 is a schematic structural diagram of a visible light-infrared light coupled flow field measurement system with a flow generation assembly and a particle generation assembly based on image processing according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a first embodiment of a fluid generation assembly and a particle generation assembly according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a second embodiment of a fluid generation assembly and a particle generation assembly according to an embodiment of the invention.
Reference numerals:
a test section 10, a light-transmitting window 101, a flow field imaging surface 102, a first optical filter 103, a second optical filter 104,
a first camera 301, a second camera 302, infrared light information 303, visible light information 304;
an image processing module 40;
a fluid generation assembly 50, a first pressure reservoir 501, a second pressure reservoir 502, a third pressure reservoir 503;
the particle generating assembly 60, the supersonic velocity spray pipe 601, the injection quenching section 602, the particle generating and mixing section 603 and the air injection port 604;
The implementation, functional features and advantages of the objects of the present invention will be further explained with reference to the accompanying drawings.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
It should be noted that all the directional indicators (such as up, down, left, right, front, and rear … …) in the embodiment of the present invention are only used to explain the relative position relationship between the components, the movement situation, etc. in a specific posture (as shown in the drawing), and if the specific posture is changed, the directional indicator is changed accordingly.
In addition, the descriptions related to "first", "second", etc. in the present invention are only for descriptive purposes and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "connected," "secured," and the like are to be construed broadly, and for example, "secured" may be a fixed connection, a removable connection, or an integral part; the connection can be mechanical connection, electrical connection, physical connection or wireless communication connection; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In addition, the technical solutions in the embodiments of the present invention may be combined with each other, but it must be based on the realization of those skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination of technical solutions should not be considered to exist, and is not within the protection scope of the present invention.
Fig. 1 shows a visible light-infrared light coupling flow field measurement system based on image processing, which mainly includes a test section 10, a laser component 20, an imaging component, and an image processing module 40. The testing section 10 is provided with a flow field with trace particles, the top of the testing section 10 is provided with a light-transmitting window 101, the laser assembly 20 is used for generating a laser sheet 201, and the laser sheet 201 illuminates the flow field imaging surface 102 in the testing section 10 through the light-transmitting window 101. The molding assembly includes a first camera 301 and a second camera 302, and both the first camera 301 and the second camera 302 focus on the flow field imaging plane 102. One side of the test section 10 is provided with a first optical filter 103 which can only pass through visible light, and the first optical filter 103 is located between the flow field imaging surface 102 and the lens of the first camera 301, so that the first camera 301 acquires a flow field visible light image. The other side of the test segment 10 is provided with a second optical filter 104 only capable of passing infrared light, and the second optical filter 104 is located between the flow field imaging surface 102 and the lens of the second camera 302, so that the second camera 302 acquires an infrared light image of the flow field. The image processing module 40 is in communication connection with the first camera 301 and the second camera 302 to complete full measurement and acquisition of flow field information based on a flow field visible light image and a flow field infrared light image, wherein the acquisition time of the flow field visible light image and the acquisition time of the flow field infrared light image are synchronous.
In this embodiment, the optical signals in the flow field are screened by the first optical filter 103 and the second optical filter 104 disposed at the front and the rear sides of the test section 10. The transmission wavelength range of the first optical filter 103 is a visible light waveband, laser sheet light 201 generated by the laser component 20 is transmitted and converted into sheet light which can be just focused on the flow field imaging surface 102 through the light-transmitting window 101 above the testing section 10, and acts on tracer particles carried by airflow in the testing section 10 to generate mie scattering or rayleigh scattering, the visible light generated by scattering penetrates through the first optical filter 103 in front of the testing section 10, and the contained information is captured by the first camera 301, namely, a flow field visible light image. The transmission wavelength of the second optical filter 104 is a medium-long infrared wave (wavelength 8-14 μm), when the test fluid flows through the test section 10, infrared radiation is spontaneously generated according to the static temperature of the fluid, infrared light of the infrared radiation passes through the second optical filter 104 behind the test section 10, and the contained information is captured by the second camera 302, that is, a flow field infrared light image. By the design of the first optical filter 103 and the second optical filter 104, synchronous and separate acquisition processing of the flow field infrared light information 303 and the visible light information 304 is realized, and finally, the flow field visible light image and the flow field infrared light image are synchronously input to the image processing module 40 to complete full-measurement acquisition of the flow field information. The first filter 103 is preferably quartz optical glass, the second filter 104 is preferably coated germanium glass, and the second camera 302 is an infrared camera.
In the present embodiment, the laser assembly 20 is preferably a double-pulse Nd: YAG laser with wavelength of 532nm has two laser beams in very short time interval.
Referring to fig. 2, the image processing module 40 completes the full measurement and collection process of the flow field information as follows: and obtaining a velocity field and a temperature field of the flow field based on the visible light image and the infrared light image of the flow field, obtaining a Mach number field based on the velocity field and the temperature field of the flow field, obtaining a static pressure distribution field based on the Mach number field of the flow field, and obtaining a density field based on the static pressure distribution field and the temperature field of the flow field.
In the specific implementation process, the velocity values of all areas of the experimental imaging section can be obtained by carrying out PIV cross-correlation algorithm analysis on the flow field visible light image, namely the velocity field. The infrared camera obtains a flow field infrared light image, the static temperature of the measured object has a corresponding relation with the gray value of the image obtained by the infrared camera with fixed parameters, the infrared camera with fixed parameters is calibrated by a standard black body to obtain the flow field infrared light image, and then the static temperature values of all areas of the focusing section of the infrared camera can be obtained by gray level analysis according to the gray value of the pixel, namely the temperature field. The acquisition of the velocity field and the temperature field is conventional technical means in the field, and therefore, the detailed description thereof is omitted in this embodiment.
Compressibility does not generally need to be considered in the liquid flow field, velocity and temperature information is sufficient for analysis, while the gas flow field needs more flow field data for analysis, and the following description describes the subsequent data processing of gas, and the specific flow is shown in fig. 2. Firstly, the obtained information of the velocity field and the temperature field is stored in a second-order matrix form, the XY coordinates of the space of the flow field imaging surface 102 are used as a matrix sequence, the velocity values and the temperature values of the corresponding coordinates are used as matrix numerical values to be stored, and then subsequent calculation analysis is carried out.
The temperature field value can be calculated by a sound velocity formula to obtain local sonic field information of the flow field imaging surface 102, and the mach number field of the flow field imaging surface 102 can be summarized by dividing the local sonic field information by the velocity field information:
Ma＝v/c
in the formula, Ma is a Mach number field of a flow field, v is a velocity field of the flow field, c is local sound velocity, gamma is an adiabatic index, R is a gas constant, and T is a temperature field of the flow field;
from the mach number field and the known total fluid pressure, the static pressure value can be calculated by using the isentropic relation to obtain the static pressure distribution field of the flow field imaging surface 102:
wherein P is the static pressure distribution field of the flow field, P0Is the total pressure of the fluid in the flow field;
the density field of the flow field imaging surface 102 can be calculated by the static pressure distribution field and the temperature field, combining with the fluid physical property parameters and by an ideal gas state equation:
wherein rho is the density field of the flow field, and M is the unit molecular mass.
Referring to fig. 3, as a preferred implementation manner, the visible light-infrared light coupled flow field measurement system based on image processing in the present embodiment further includes a fluid generation assembly 50 and a particle generation assembly 60. The fluid generating assembly 50 is used to generate fluid during a flow field test. The particle generating assembly 60 is connected to the fluid generating assembly 50, such that the fluid is accelerated and depressurized after entering the particle generating assembly 60, such that the fluid is rapidly cooled and de-sublimated to generate micron-scale or nanometer-scale ice crystal tracer particles 706, and the particle generating assembly 60 is connected to the test section 10, such that the fluid with the ice crystal tracer particles 706 is input to the test section 10.
In this embodiment, different ice crystal tracer particles 706 are generated for different mach number flow fields. For the case of low Mach number (less than Mach 2), the low-temperature jet flow extremely-cold air is adopted to promote the water vapor in the air to be condensed into micron-scale or nano-scale ice crystal tracer particles 706, and the particle size of the ice crystal tracer particles 706 is adjusted through extremely-cold degree, so that the visual measurement requirements of PIV, NPLS, MPLS and the like are met. For the case of high Mach number (Mach 2 or more), the static temperature corresponding to the flow field is low enough, and CO can be used2And Freon and other easily-desublimated gases 704 spontaneously generate ice crystal tracer particles 706, and the density of the ice crystal tracer particles 706 can be changed by controlling the mixing amount of the easily-desublimated gases 704 and the dispersed gas 705, so that the requirements of visual measurement of PIV, NPLS, MPLS and the like are met.
Referring to fig. 4, a first embodiment of a spontaneous generation of ice crystal tracer particles 706 with flow field velocities less than mach 2. Specifically, in this embodiment, the particle generating assembly 60 includes a supersonic nozzle 601, an injection quenching section 602, and a particle generating mixing section 603, the fluid generating assembly 50 includes a first pressure storage tank 501 having a high-pressure gas 701, an output end of the first pressure storage tank 501 is communicated with a contraction end of the supersonic nozzle 601, so as to input the high-pressure gas 701 into the supersonic nozzle 601, and convert the high-pressure gas 701 into a supersonic low-temperature jet 702 after being accelerated and depressurized and output via an expansion end of the supersonic nozzle 601; the input end of the injection quenching section 602 is communicated with the expansion end of the supersonic velocity spray pipe 601, and the input end of the injection quenching section 602 is provided with an air injection port 604 for injecting air 703 to the injection quenching section 602; the input end of the particle generation mixing section 603 is communicated with the output end of the injection quenching section 602 and is used for mixing the air 703 with the supersonic low-temperature jet 702, so that water vapor in the air 703 is quenched to generate ice crystal tracer particles 706, and the output end of the particle generation mixing section 603 is communicated with the input end of the testing section 10. The high-pressure gas 701 is an inert gas, a nitrogen gas, dehydrated air, or the like which does not participate in the reaction.
The working process of the first embodiment is as follows: high-pressure gas 701 in a first pressure storage tank 501 passes through an ultrasonic spray pipe 601(Ma <2) and then is changed from high pressure to low pressure, ultrasonic low-temperature jet flow 702 is generated in an injection quenching section 602, air 703 is injected through an air injection port 604 in the injection quenching section 602, the ultrasonic low-temperature jet flow 702 is mixed with the air 703 in a particle generation mixing section 603, the air 703 is rapidly cooled, water vapor in the air 703 is condensed to form small ice crystals, ice crystal tracing particles 706 and the gas are fully mixed in the particle generation mixing section 603 and then enter a testing section 10, the ice crystal tracing particles 706 obtained through spontaneous particle generation are lightened in the testing section 10 through laser sheet light 201, then a high-resolution visible light image of a flow field can be obtained through a first camera 301, qualitative information such as an NPLS image analysis flow field structure and the like can be used, and through cross-correlation processing of two or more images, a velocity field, a temperature and a temperature of a gas can be obtained through a PIV method, Quantitative information such as turbulence energy, acceleration field and the like. Wherein, the small ice crystals generated by spontaneous desublimation are in micron order or nanometer order, and the followability is good. Further, the flow rate of supersonic cryogenic jet 702 can be controlled by controlling the pressure of high-pressure gas 701 output by first pressure storage tank 501, so as to change the mixing ratio of supersonic cryogenic jet 702 and air 703, that is, the density ratio of ice crystal tracer particles 706 in the test gas flow. Meanwhile, the larger the outlet area/throat area of the supersonic nozzle 601 is, the lower the temperature of the supersonic low-temperature jet 702 at the outlet of the supersonic nozzle 601 is, the larger the temperature difference with the air 703 is, the larger the particle size of the ice crystal tracer particles 706 obtained by mixing and quenching is, and therefore, by replacing different supersonic nozzles 601, the ice crystal tracer particles 706 with different particle sizes can be obtained.
Referring to fig. 5, in order to generate the ice crystal tracing particles 706 spontaneously in the second embodiment, the flow field velocity in this embodiment is greater than or equal to mach 2, the compressed and complete mixed gas flow 707 (the dispersed gas 705 is mixed with the easily-desublimed gas 704) is directly used as the gas source of the supersonic flow field, i.e. the ice crystal tracing particles 706 can be generated spontaneously, and the uniformity and following performance of the spontaneously-generated ice crystal tracing particles 706 are ensured to the maximum extent. Specifically, in this embodiment, particle generation assembly 60 includes supersonic nozzle 601; the fluid generating assembly 50 comprises a second pressure storage tank 502 and a third pressure storage tank 503, wherein the second pressure storage tank 502 is provided with high-pressure easy-to-desublimate gas 704, and the third pressure storage tank 503 is provided with high-pressure dispersing gas 705; the output end of the second pressure storage tank 502 and the output end of the third pressure storage tank 503 are both communicated with the input end of the supersonic velocity spray pipe 601, so that the easily desublimed gas 704 and the dispersed gas 705 are subjected to accelerated depressurization in the supersonic velocity spray pipe 601 to generate quenching, and the easily desublimed gas 704 is spontaneously condensed to generate ice crystal tracer particles 706; the output end of supersonic nozzle 601 is communicated with the input end of test section 10. Wherein the desublimating gas 704 includes, but is not limited to, CO2And freon, the dispersion gas 705 is inert gas or gas such as nitrogen gas or dehydrated air which does not participate in the reaction.
The working process of the second embodiment is as follows: after the pressure of the easily desublimated gas 704 and the dispersed gas 705 is regulated by the second pressure storage tank 502 and the third pressure storage tank 503, the easily desublimated gas 704 and the dispersed gas 705 are mixed at the inlet of the supersonic velocity spray pipe 601, and the mixed gas is fully mixed and then passes through the supersonic velocity spray pipe 601(Ma is more than or equal to 2), when the speed of the mixed gas 707 is too high, the temperature of the corresponding mixed gas 707 is lower than the desublimated temperature of the corresponding easily desublimated gas 704 under the current mixed partial pressure, the easily desublimated gas 704 molecules in the mixed gas 707 can be spontaneously condensed to generate ice crystal tracer particles 706, the particle arrangement uniformity generated by the spontaneous condensation is good, the gas flow containing the tracer particles accelerated by the supersonic velocity spray pipe 601 can be directly used as a test incoming flow to enter the test section 10, the ice crystal tracer particles 706 obtained by the spontaneous generation of the particles are lightened by the laser sheet light 201 in the test section 10, a high-resolution flow field visible light image can be obtained by the first camera 301, and can be used as qualitative information of an NPLS image analysis flow field structure and the like, quantitative information such as a velocity field, a turbulent motion energy, an acceleration field and the like can be obtained by the PIV method through the mutual correlation processing of two or more images. Wherein, the density distribution of the ice crystal tracer particles 706 in the flow field can be controlled by changing the mixing ratio of the dispersed gas 705 and the easily desublimed gas 704, thereby achieving the purpose of dynamic regulation. Test fluids with different incoming flow speeds can also be obtained by replacing different supersonic nozzle 601.
In the above two embodiments, the self-generated ice crystal tracer particles 706 can be analyzed and detected by capturing the visible light image of the flow field, so as to perform dynamic adjustment. Taking the NPLS image as an example, by placing a shock wave generator in the test section 10, it can be detected whether the particle size of the ice crystal tracer particles 706 can reach a nanometer level through the change of the ice crystal tracer particles 706 before and after the shock wave (refer to the monograph "ultrasonic flow field NPLS fine measurement test technique and typical application"). In the detection process, the shock wave generator generates shock waves, if the fluid static temperature behind the shock wave surface is increased and the ice crystal tracing particles 706 disappear, the particle size of the ice crystal tracing particles 706 reaches the nanometer level, the following performance of the ice crystal tracing particles meets the requirement of a hypersonic speed experiment, and the flow field characteristics of the shock waves, the vortexes and the like in a hypersonic field can be well expressed. And performing gray level analysis and image recognition on the obtained NPLS image, analyzing the average brightness of the image, the light-dark contrast of particles and the background and the number of noise points, acquiring image information such as the signal-to-noise ratio of the NPLS image, the image imaging sharpness and tolerance and the like, analyzing the structure such as shock waves, vortexes and the like in the image by combining with hydrodynamics, comprehensively evaluating the image, further adjusting the density and the particle size of the tracer particles, and dynamically optimizing the image.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention, and all modifications and equivalents of the present invention, which are made by the contents of the present specification and the accompanying drawings, or directly/indirectly applied to other related technical fields, are included in the scope of the present invention.
Claims (8)
1. A visible light-infrared light coupling flow field measurement system based on image processing is characterized by comprising a test section, a laser assembly, an imaging assembly and an image processing module, wherein the test section is internally provided with a flow field with tracer particles;
the top of the testing section is provided with a light-transmitting window, the laser assembly is used for generating laser sheet light, and the laser sheet light illuminates a flow field imaging surface in the testing section through the light-transmitting window;
the molding assembly comprises a first camera and a second camera, the first camera and the second camera focus on the flow field imaging surface:
a first optical filter which can only pass visible light is arranged on one side of the test section, and the first optical filter is positioned between the flow field imaging surface and a lens of the first camera, so that the first camera can acquire a flow field visible light image;
a second optical filter which only can pass through infrared light is arranged on the other side of the test section, and the second optical filter is positioned between the flow field imaging surface and a lens of the second camera, so that the second camera can acquire a flow field infrared light image;
the image processing module is in communication connection with the first camera and the second camera to complete full measurement and collection of flow field information based on the flow field visible light image and the flow field infrared light image, wherein the flow field visible light image and the flow field infrared light image are acquired in time synchronization.
2. The image processing-based visible light-infrared light coupling flow field measurement system according to claim 1, wherein the image processing module performs a full measurement and collection process of flow field information as follows:
obtaining a velocity field and a temperature field of the flow field based on the flow field visible light image and the flow field infrared light image;
obtaining a Mach number field based on a velocity field and a temperature field of a flow field:
Ma＝v/c
in the formula, Ma is a Mach number field of a flow field, v is a velocity field of the flow field, c is local sound velocity, gamma is an adiabatic index, R is a gas constant, and T is a temperature field of the flow field;
obtaining a static pressure distribution field based on a Mach number field of a flow field:
wherein P is the static pressure distribution field of the flow field, P0Is the total pressure of the fluid in the flow field;
obtaining a density field based on a static pressure distribution field and a temperature field of a flow field:
wherein rho is the density field of the flow field, and M is the unit molecular mass.
3. The visible light-infrared light coupling flow field measurement system based on image processing according to claim 1 or 2, wherein the first optical filter is quartz optical glass.
4. The image processing-based visible light-infrared light coupling flow field measurement system according to claim 1 or 2, wherein the second optical filter is a germanium-coated glass.
5. The visible light-infrared light coupling flow field measurement system based on image processing according to claim 1 or 2, characterized by further comprising:
a fluid generation assembly for generating a fluid;
the particle generation assembly is connected with the fluid generation assembly and is used for accelerating pressure reduction of the fluid so as to reduce the temperature and desublimate the fluid to generate micron-scale or nanometer-scale ice crystal tracer particles;
the particle generating assembly is coupled to the test section to deliver a fluid with ice crystal tracer particles into the test section.
6. The image processing-based visible light-infrared light coupling flow field measurement system according to claim 5, wherein the particle generation assembly comprises a supersonic nozzle, an injection quenching section and a particle generation mixing section;
the fluid generation assembly comprises a first pressure storage tank with high-pressure gas, and the output end of the first pressure storage tank is communicated with the contraction end of the supersonic velocity spray pipe so as to input high-pressure fluid into the supersonic velocity spray pipe, so that the high-pressure fluid is converted into supersonic velocity low-temperature jet flow after being accelerated and depressurized and is output through the expansion end of the supersonic velocity spray pipe;
the input end of the injection quenching section is communicated with the expansion end of the supersonic velocity spray pipe, and the input end of the injection quenching section is provided with an air injection port for injecting air to the injection quenching section;
the input end of the particle generation mixing section is communicated with the output end of the injection quenching section and is used for mixing air with the supersonic low-temperature jet flow so that water vapor in the air is quenched to generate the ice crystal tracing particles, and the output end of the particle generation mixing section is communicated with the input end of the testing section.
7. The image processing based visible light-infrared light coupling flow field measurement system of claim 5, wherein the particle generation assembly comprises a supersonic nozzle;
the fluid generation assembly comprises a second pressure storage tank and a third pressure storage tank, wherein the second pressure storage tank is internally provided with high-pressure easily-desublimed gas, and the third pressure storage tank is internally provided with high-pressure dispersed gas;
the output end of the second pressure storage tank and the output end of the third pressure storage tank are communicated with the input end of the supersonic velocity spray pipe, so that the easily desublimated gas and the dispersed gas are subjected to accelerated depressurization in the supersonic velocity spray pipe to generate rapid cooling, and the easily desublimated gas is spontaneously condensed to generate the ice crystal tracer particles;
and the output end of the supersonic velocity spray pipe is communicated with the input end of the test section.
8. The image processing based visible light-infrared light coupling flow field measurement system according to claim 7, wherein the gas prone to sublimation includes but is not limited to CO2And freon.
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