Study On Real-time Temperature Monitoring Method Based On Tunable Semiconductor Laser Absorption Spectrum

Temperature as a physical quantity is particularly important in the diagnosis of combustion efficiency.By controlling the temperature in the combustion field,the combustion efficiency can be improved and the emission of harmful gases can be reduced.The traditional contact temperature measurement means will interfere with the combustion field,and the high temperature is also easy to damage the instrument,and the temperature measurement range is also very limited.Tuneable semiconductor laser absorption spectroscopy(TDLAS)technology,as a non-invasive measurement technology,has high sensitivity,fast response,strong real-time characteristics,and has great application prospects in combustion field temperature measurement and gas composition analysis.Taking TDLAS technology as the basic principle and water molecules as the target gas,we design a data acquisition and real-time waveform display software and design the main algorithm for data processing.Firstly,the basic principle of absorption spectrum temperature measurement is introduced,and the general principle of spectral line selection is described.Two water absorption spectra of 7182.9496cm-1 and 7179.7524cm-1 at different temperatures were simulated by using the data from HITRAN database.The simulation results show that these two spectra have good temperature sensitivity at 300-1100 K.The basic structure of TDLAS system is briefly introduced.Secondly,in software design,MFC single document mode is used to build a dual-interface software,data acquisition page and data playback page interface respectively.In the data acquisition interface,the multithreading method is used to solve the data acquisition,processing,display,wherein multithreading adopts the way of event synchronization;In the data playback page,the timer is used to realize the automatic data playback.After obtaining experimental data from steady-state environment measurement experiments,Matlab program was written on the basis of combining spectral line temperature measurement principle and processing the data.The relative error between the experimental results and the calibrated temperature was within the range of 300-1073 K,and the relative error gradually increased but did not exceed 10% as the temperature rose.The results are consistent with the simulation results to verify the feasibility of the algorithm.Then,the key problems such as baseline fitting,wavenumber conversion,integral absorption calculation and temperature inversion are discussed in order to realize the purpose of real-time temperature monitoring.Finally,the work of this paper is summarized and the shortcomings are pointed out to provide a certain direction for the follow-up research.