Study On Temperature Measurement Using Wavelength Modulation Based On Profile Function Second Harmonic Coefficient Estimation

In recent years,the country has attached great importance to the research of new types of ammunition,and explosion temperature is an important indicator for evaluating the performance of ammunition.In terms of explosion temperature measurement,traditional temperature measurement techniques are limited by response speed,range,and application conditions,making it difficult to accurately obtain explosion temperature parameters.Tunable laser absorption spectroscopy(TDLAS)technology can measure temperature,absorption component concentration and other information,and has the advantages of fast response,simple measurement system,wide range,strong anti-interference ability,etc.It has a great application prospect in the temperature measurement of explosion field.In temperature measurement using wavelength modulation method using TDLAS technology,the ratio of the second harmonic coefficient of the profile function of two spectral lines has a significant impact on temperature calculation,and in practice,the line type function is unknown,which increases the difficulty of temperature calculation.In response to the above issues,this article conducted research on wavelength modulation temperature measurement based on the estimation of the second harmonic coefficient of linear functions.Firstly,the effects of temperature,pressure,and concentration on the spectral line width and weight coefficient were analyzed through simulation,as well as the effects of spectral line width and weight coefficient on the ratio of the second harmonic coefficient of the profile function of two spectral lines;Secondly,a TDLAS temperature measurement simulation system is constructed using laser emission,spectral absorption,and transmission signal phase-locked detection models for line width measurement and temperature measurement simulation experiments;Once again,based on the properties of the fixed point passing through(the ratio R24 of the transmitted signal’s second to fourth harmonic signal and the constant curve of the modulation coefficient passing through the fixed point),the line width was successfully measured using the line width measurement method passing through the fixed point;Finally,based on the online width measurement,an estimation method for the ratio of the second harmonic coefficient of the profile function of two spectral lines is proposed,and this estimation method is verified through temperature measurement simulation experiments.The experimental results show that using the proposed method for estimating the ratio of the second harmonic coefficient of the profile function of two spectral lines in this paper,the error between the calculated temperature and the true value of the experimental temperature is within 10%.