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CN-122016078-A - Temperature measurement method and system based on structured light-heat auxiliary fluorescence

CN122016078ACN 122016078 ACN122016078 ACN 122016078ACN-122016078-A

Abstract

The temperature measuring system consists of a laser module, a reflecting component, a refraction component, a structural light modulation module, a single-phase machine double-light-path signal acquisition module and a signal processing module, wherein the single-wavelength ultraviolet light source emitted by the laser module drives OH free radical thermal auxiliary fluorescence response, and the structural light modulation and single-phase machine double-light-path space-time synchronous acquisition are combined, so that the accuracy of filtering of scattered noise optical layers and double-band fluorescence is realized on the premise of not increasing the number of lasers and optical channels, and the stable operation of the system under severe conditions such as high temperature, vibration, limited installation space and the like is ensured.

Inventors

  • XU WENJIANG
  • KONG YINUO
  • YE YUAN
  • LIU BOHUA
  • HUANG YUE

Assignees

  • 厦门大学

Dates

Publication Date
20260512
Application Date
20260212

Claims (10)

  1. 1. The temperature measurement method based on the structured light-heat auxiliary fluorescence is characterized by comprising the following steps of: S1, outputting and shaping laser, namely converting green laser into ultraviolet light after the laser module outputs the green laser, using the ultraviolet light as a light source, adjusting the incident direction and the incident position of the ultraviolet light through a reflecting assembly, and shaping the ultraviolet light into a sheet-shaped light beam which is consistent with a preset height through a refracting assembly; s2, structural light modulation, namely modulating the sheet-shaped light beam into interference fringes with spatial phase information by utilizing a triangular prism element, wherein the modulation characteristics of the interference fringes can be kept by fluorescence; S3, acquiring a structural light fluorescence signal by using a single-camera double-light-path signal acquisition module, synchronously capturing fluorescence spectrums of OH free radicals (A2Σ+ & gtX 2 pi) in a (0, 0) wave band and a (1, 0) wave band by using a framing filter, and realizing signal synchronization by using a photoelectric detection module; S4, signal processing, namely processing the acquired fluorescence spectrum, decomposing a fluorescence signal of the fluorescence spectrum into a sine component and a cosine component, creating a reference signal containing modulation frequency, carrying out up-conversion on a stray light signal, filtering the stray light signal through a filter, and extracting to obtain a demodulated fluorescence signal; S5, inverting the temperature field, namely acquiring the relationship between the fluorescence intensity proportion and the temperature through a VET model based on a thermal auxiliary fluorescence technology, inverting the two-dimensional temperature field through the following formula to acquire a two-dimensional local temperature field, Where ΔE 10 is the energy difference between A-excited vibration level 1 and vibration level 0, k is the Boltzmann constant, T is absolute temperature, Q 1 is the rate of quenching and all other energy losses, V 10 is the rate of transfer of downward vibrations between A-excited vibration level 1 and vibration level 0, 、 The fluorescence signals from the A excited state vibration energy level 1 and the vibration energy level 0 to the X ground state energy level 0 after demodulation are respectively, A 00 is the spontaneous emission Einstein coefficient of the energy level transition of 0 to 0, and A 10 is the spontaneous emission Einstein coefficient of the energy level transition of 1 to 0.
  2. 2. The method of claim 1, wherein in step S2, the relationship formula between the spatial center height of the structured light, the distance between the structured light center and the incident surface of the triangular prism element, and the base angle of the triangular prism element is introduced when the triangular prism element performs the structured light modulation on the sheet-shaped light beam: wherein H represents the height of the structured light spatial center, L represents the distance between the structured light center and the incident surface of the triangular prism element, θ represents the base angle of the triangular prism element, n 1 represents the refractive index of the triangular prism element material at a specific light source wavelength, n 2 represents the refractive index of air, and n 1 /n 2 =1.485.
  3. 3. The method for measuring temperature based on structured light-thermal auxiliary fluorescence according to claim 1, wherein in step S3, a time sequence adjustment module is introduced to shorten the exposure time of the single-camera dual-optical-path signal acquisition module, and the fluorescence spectrum acquired by the single-camera dual-optical-path signal acquisition module adjusted by the time sequence adjustment module is transmitted to the photoelectric detection module.
  4. 4. A method of thermometry based on structured light-thermal assisted fluorescence according to claim 3, wherein the photodetection module comprises an image intensifier which can intensify the intensity of the fluorescence signal and a camera which can convert the fluorescence signal into digital image data.
  5. 5. The method of claim 4, wherein a signal correction step is performed on the fluorescent signal before step S4, the signal correction step including geometric distortion correction of the fluorescent signal using a calibrated checkerboard image and correction of the camera response using a standard light-emitting plate, thereby ensuring consistent signal intensity distribution.
  6. 6. The method for measuring temperature based on structured light-thermal assisted fluorescence according to claim 1, wherein step S4 comprises the steps of: s41, receiving the fluorescent signal transmitted from the single-camera double-light-path signal acquisition module, wherein the fluorescent signal comprises the stray light signal and an effective signal, and the relation expression of the effective signal and the stray light signal is as follows: Wherein, F X is the fluorescence signal, F S is the effective signal, F MS is the stray light signal, v is the modulation frequency, and Φ is the modulation spatial phase; s42, demodulating the signal to extract the effective signal, applying a phase demodulation algorithm to decompose the fluorescent signal into a sine component and a cosine component by using the Pythagorean triangle identity, and then obtaining the square root of the square sum by calculating the square root of the square sum To filter the stray light signal ; S43, matching the effective signals of the (0, 0) wave band obtained by demodulation in the step S42 with the effective signals of the (1, 0) wave band.
  7. 7. A temperature measurement system based on structured light-thermal assisted fluorescence, the temperature measurement system being applicable to a temperature measurement method based on structured light-thermal assisted fluorescence according to any one of claims 1 to 6, comprising: the laser module comprises a solid laser and a dye laser, wherein the solid laser outputs green laser, and converts the green laser into ultraviolet light through the dye laser, and the ultraviolet light is used as a light source; The reflecting assembly comprises a first reflecting mirror and a second reflecting mirror which are sequentially arranged, and the incidence direction and the position of the light source can be changed by the first reflecting mirror and the second reflecting mirror; The refraction component comprises a concave lens and a convex lens which are sequentially arranged, and the concave lens and the convex lens are matched to shape the light source into a sheet-shaped light beam from a cylindrical state; the structure light modulation module is a triangular prism element; the system comprises a single-camera double-light-path signal acquisition module, a signal processing module and a control module, wherein the single-camera double-light-path signal acquisition module comprises a framing filter and a photoelectric detection module, and the signal processing module comprises a computer.
  8. 8. The system of claim 7, wherein the cross section of the triangular prism element is in the shape of an isosceles triangle, the sheet-shaped light beams vertically enter from the bottom side of the isosceles triangle, two sections of sheet-shaped light beams are formed through refraction of the waist of the isosceles triangle, and the two sections of sheet-shaped light beams are crossed and fused to form the structured light with intensity changing brightness.
  9. 9. A structured light-thermal assisted fluorescence based temperature measurement system according to claim 8, wherein the structured light space where two segments of said sheet-like light beams are cross-fused has a diamond-shaped structure, and the central position of said structured light space is located in a flame measurement area above the combustion chamber.
  10. 10. The system of claim 7, wherein the frame filter comprises a rectangular filter and a neutral filter, the rectangular filter is only capable of transmitting fluorescent signals with wave bands (0, 0) and (1, 0), and the filtering areas of the wave bands (0, 0) and (1, 0) respectively occupy half of the rectangular filter.

Description

Temperature measurement method and system based on structured light-heat auxiliary fluorescence Technical Field The invention relates to the technical field of fluorescence temperature measurement, in particular to a temperature measurement method and system based on structured light-heat auxiliary fluorescence. Background The research of temperature measurement for combustion has important significance for exploring the combustion process and mechanism, and has key effects on realizing low-pollution and low-energy consumption combustion technology. The non-contact laser diagnosis method has become an important research means in complex combustion environment due to small interference to a flow field, high measurement frequency and flexible arrangement of measuring points. Among many non-contact laser diagnosis techniques, a two-dimensional laser induced fluorescence (PLIF) technique can acquire information such as a transient two-dimensional structure of flame, a temperature field, and the like by analyzing fluorescence emitted from a specific component at the time of energy level transition. The two-dimensional laser-induced fluorescence technology mainly comprises an excitation wavelength scanning laser-induced fluorescence method, a double-line method and a thermal auxiliary fluorescence temperature measurement method, wherein the thermal auxiliary fluorescence temperature measurement method utilizes single-wavelength laser to excite molecules to a high energy state, the molecules are transferred to adjacent energy levels through thermal motion, the process is related to temperature, and the temperature can be inverted by analyzing fluorescence spectrums of different vibration energy levels. In addition, the structured light illumination plane imaging technology can effectively distinguish direct scattered photons carrying sample information from unordered multiple scattered noise by changing uniform sheet light into spatially modulated structured light. By means of a phase shifting algorithm and frequency domain demodulation, a two-dimensional quantitative image with a high signal-to-noise ratio can be extracted from the aliased signal. However, when two-dimensional temperature field measurement is performed in a strong scattering environment such as a closed combustion chamber, multiple scattering noise and effective signals are seriously aliased, so that temperature inversion accuracy is limited, and in order to realize high-accuracy measurement, the number of lasers is often required to be increased, a complex synchronous control system is provided, and the complexity and cost of the system are increased. Disclosure of Invention Aiming at the defects existing in the background technology, the invention aims to provide a temperature measurement method and a temperature measurement system based on structured light-heat auxiliary fluorescence, which aim to solve the problem that a two-dimensional quantitative image with high signal to noise ratio and high contrast is difficult to construct by using simple equipment in a two-dimensional temperature field. In order to achieve the above purpose, the present invention provides the following technical solutions: A temperature measurement method based on structured light-heat auxiliary fluorescence comprises the following steps: S1, outputting and shaping laser, namely converting green laser into ultraviolet light after the laser module outputs the green laser, using the ultraviolet light as a light source, adjusting the incident direction and the incident position of the ultraviolet light through a reflecting assembly, and shaping the ultraviolet light into a sheet-shaped light beam which is consistent with a preset height through a refracting assembly; s2, structural light modulation, namely modulating the sheet-shaped light beam into interference fringes with spatial phase information by utilizing a triangular prism element, wherein the modulation characteristics of the interference fringes can be kept by fluorescence; S3, acquiring a structural light fluorescence signal by using a single-camera double-light-path signal acquisition module, synchronously capturing fluorescence spectrums of OH free radicals (A2Σ+ & gtX 2 pi) in a (0, 0) wave band and a (1, 0) wave band by using a framing filter, and realizing signal synchronization by using a photoelectric detection module; S4, signal processing, namely processing the acquired fluorescence spectrum, decomposing a fluorescence signal of the fluorescence spectrum into a sine component and a cosine component, creating a reference signal containing modulation frequency, carrying out up-conversion on the stray light signal, filtering the stray light signal through a filter, and extracting to obtain a demodulated fluorescence signal; S5, inverting the temperature field, namely acquiring the relationship between the fluorescence intensity proportion and the temperature through a VET model based on a thermal auxili