CORRECTION OF LIF TEMPERATURE-MEASUREMENTS FOR LASER-ABSORPTION AND FLUORESCENCE TRAPPING IN A FLAME - APPLICATION TO THE THERMAL PERTURBATION STUDY INDUCED BY A SAMPLING PROBE

A computational method is described in order to correct OH LIF tempera ture measurements for absorption of laser energy and trapping of fluor escence. Calculations are performed in a large range of flame conditio ns and can be used as a correction data base both in case of (0-0) and (1-0) excitations. Comparison of corrected temperatures profiles obta ined in a 40 Torr methanol/air flame, for both kinds of Laser-Induced Fluorescence (LIF) excitations shows a very good agreement. This metho d is applied to measure the temperature profile of a methanol flame pe rturbed by a sampling probe. The LIF collection volume is located at t he actual probe sampled volume using an experimental procedure already described. Spatial resolution and sensitivity of temperature measurem ents are sufficiently efficient to highlight, for the first time by LI F, an indubitable cooling effect due to the probe presence that induce s important OH profile change. According to flame chemical modelling, it is shown that both effects are strongly correlated.