Two Dimensional Temperature And Carbon Dioxide Concentration Profiles Of Nitrogen Added Ethylene Co-flow Diffusion Flames Measured By Mid-Infrared Direct Absorption Spectroscopy

Temperature and gas concentration are important parameters in combustion diagnosis research.Real-time monitoring of these combustion parameters can evaluate the combustion performance and operation status of the burner,predict the tendency of the combustion process,and provide reference for the combustion burner desing.Co-flow diffusion flame is a widely used laboratory flame to study soot formation and oxidation.Measuring the temperature and concentration distribution of the gas phase molecules in the flame can be used to understand the flame structure and combustion chemistry.In this study,temperature distribution of axisymmetric ethylene-air coflow flame was measured by direct absorption spectroscopy at the bandhead of v3 band of carbon dioxide,which is sensitive to the temperature change and is free from background absorption.A room temperature continuous wave interband cascade laser(ICL)was used to scan wavelength at the bandhead region near 4.2μm.The path integrated absorption signal of the axisymmetric coflow diffusion flame was Abel inversed to local absorption coefficients that was then non-linear least square fitted with HITRAN database to reconstruct the temperature and carbon dioxide distributions in the flame.In order to increase the accuracy of Abel inversion,Tikhonov regularization method was used and its feasibility was verified through numerical simulation.The temperature distribution of coflow diffusion flame obtained in this research was compared with those obtained by two-line atomic fluorescence.