Two-dimensional temperature field and concentration field imaging method based on Zernike polynomial fitting

Abstract

The invention relates to a two-dimensional temperature field and concentration field imaging method based on Zernike polynomial fitting, and the method mainly comprises the following steps: for a multi-angle laser absorption spectrum imaging sensor, arranging a certain number of detectors at equal intervals at each angle, enabling laser emitted by a laser device to pass through a to-be-detected area and to be received by a photoelectric detector, m pieces of laser absorption spectrum data are obtained; discretizing an area to be measured into N grids, and fitting local integral absorptivity distribution of an absorption spectral line in the discrete grids by using a K-term Zernike polynomial; a Zernike polynomial fitting coefficient is solved by utilizing the detected integral absorptivity, local integral absorptivity distribution of an absorption spectrum line is obtained by combining a Zernike polynomial matrix, and information of a temperature field and a concentration field in a to-be-detected area is obtained by utilizing a double-line method measurement principle. According to the method, the to-be-solved quantity is converted into the Zernike polynomial coefficient from the local integral absorptivity in the discrete grid, the number of unknown numbers is reduced, the equation morbidity is effectively reduced, and the method has important application value in the field of combustion dynamic monitoring.

Description

technical field [0001] The invention relates to a two-dimensional temperature field and concentration field imaging method based on Zernike polynomial fitting, and belongs to the field of laser absorption spectrum imaging. Using the prior information of the continuous distribution of flame temperature, the finite term Zernike polynomial is used to fit the local integral absorptivity distribution of different central frequency spectral lines in the area to be measured, and then the temperature field and concentration in the area to be measured are calculated according to the measurement principle of the two-line method. field. Background technique [0002] The temperature and component concentration distribution of the combustion gas are two very important parameters in the combustion process, and their parameters can reflect the fuel combustion efficiency and evaluate the performance of the burner. As a non-invasive, fast response and strong anti-interference optical detect...

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Problems solved by technology

[0003] In 2008, Cai et al. published an article titled "Application of simulated annealing for multispectral tomography" in "Computer Physics Communications" (Computer Physics Communications), Volume 179, Issue 4, Page 250-255 In this method, the inversion problem is transformed into a minimum optimization problem, and the simulated annealing algorithm is used to solve the minimum problem. This method makes full use of prior information to improve the ill-conditioned nature of the inversion problem. This method searches for an optimization algorithm that approximates the global optimal solution To solve the inverse problem, it often takes a long time to search for the optimal solution

Liu et al. published in "IEEE Sensors Journal" (IEEE Sensors Journal), Volume 19, Issue 5, Pages 1748-1755 in 2019, in the article entitled "Toward Customized Spatial Resolution in TDLAS Tomography" , on the basis of optimizing the beam arrangement, the Tikhonov regularization method was used to compare the effects of different angles and the number of detectors on the spatial resolution, but this method has a limitation on the number of reconstruction grids, that is, it can only solve a certain degree of ill-conditioned question

In 2020, Zhao et al. published in "IEEE Sensors Journal" (IEEE Sensors Journal), Volume 20, Issue 8, Pages 4179-4188, entitled "TDLAS Tomographic Imaging System Based on WMS for Inversion of Gas Concentration and Temperature Distribution in Dynamic Flame" In the article (A WMS Based TDLAS Tomographic System for Distribution Retrievals of Both Gas Concentration and Temperature in Dynamic Flames), the Joint Algebraic Reconstruction Algorithm (SART) method is used to monitor the gas concentration and temperature distribution of dynamic flames. Better results can be obtained when the number of grids is less, but the spatial resolution is lower at this time, and when the number of reconstruction grids increases, artifacts appear in the reconstructed image

In the same year, Huang et al published a paper titled "Frequency Division Multiplexing and Main Peak of TDLAS Tomography for Flame Monitoring" in "IEEE Transactions on instrumentation and measurement" (IEEE Transactions on instrumentation and measurement), pp. 9087-9096, volume 11, volume 69 In the article "Frequency-Division Multiplexing and Main Peak Scanning WMS Method for TDLAS Tomography in Flame Monitoring", the Landweber method is used to monitor the temperature field and concentration field of the dynamic Bunsen burner in real time. Acceptable low spatial resolution

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