Research On Two-dimensional Gas Concentration Detection Method Base On Infrared Laser Spectrum And Image Reconstruction Algorithm

Gas detection technology is very important for industry and environmental protection,tunable diode laser absorption spectroscopy(TDLAS)has been widely used in the field of on-site detection with the advantages of non-contact,high sensitivity,fast response and strong adaptability.TDLAS is a technology based on line of sight detection,the measurement results can only reflect the average concentration information of the measured area,and can not reflect the regional distribution characteristics of gas.In this paper,TDLAS technology combined with Computed Tomography(CT)is applied to reconstruct the two-dimensional distribution of gas concentration,and numerical simulation and experimental research are carried out.The image reconstruction algorithm of two-dimensional distribution of gas concentration is studied.Numerical simulation is carried out by using computer simulation technology,and the influence of initial value,signal error and relaxation factor on image reconstruction is studied.The reconstruction algorithm is optimized,mainly including three aspects:(1)A method of calculating the initial value is studied,which is helpful to shorten the time of reconstruction.(2)A method of using zero absorption optical path constraint reconstruction process is studied to reduce the reconstruction error.(3)An image reconstruction method based on progressive relaxation factor is proposed,which can reduce the reconstruction time significantly on the premise of guaranteeing the quality of the reconstruction.An infrared laser spectrum detection system for gas concentration two-dimensional distribution is designed.With CH4 gas as the detection target,a laser with a center wavelength of 1653.74 nm is used as the light source to build an experimental platform.In the Lab VIEW compiling environment,software for multi-channel spectral data acquisition and gas concentration distribution image reconstruction is compiled,and spectral data feature extraction and gas concentration distribution reconstruction are realized.Experimental study on two-dimensional gas distribution detection,several kinds of static gas distribution and flow gas distribution were detected respectively,and the image reconstruction results of concentration field distribution were analyzed,the effect and stability of gas two-dimensional distribution image reconstruction is verified.The result shows that the two-dimensional distribution image reconstruction algorithm and system based on infrared laser spectrum can be used to detect and reconstruct the twodimensional distribution of gas concentration,it can well reflect the gas distribution characteristics,and has good stability.