Simultaneous Measurements of Concentration and Temperature Distribution in Unsteady Gas Jets by Laser-Induced Fluorescence of Ambient Gas

A new method to simultaneously measure temperature and concentration of gas in unsteady gas jet was established with an adaptation of LIFA (Laser-induced fluorescence of ambient gas). Iodine molecules were premixed into the ambient gas and excited by a sheet light of a Nd : YAG laser. Based on the temperature dependence of iodine fluorescence spectra, the local temperatures inside a jet can be determined by the ratio between the fluorescence of two visualized images with different wave length ranges. The images were simultaneously obtained by an image intensifier, and the jet concentration was quantified by the correlation between the quantum yield of iodine and the temperature. The experimental results showed that the temperature distribution in an unsteady gas jet was quite similar to the jet concentration distribution, and with increase in ambient gas temperature, overall jet concentration increased.