Saturation Dependence of Flame Thermometry Using Mid-IR Degenerate Four Wave Mixing.

Rasmus L Pedersen,Dina Hot,Anna-Lena Sahlberg,Zhongshan Li

doi:10.1177/0003702820955186

Abstract

It has previously been demonstrated that the ratio of the degenerate four wave mixing signal from two hot water line groups near 3231 cm–1 can be used for seedless flame temperature measurements. This paper presents an investigation of the impact of saturation effects on the measured signal intensity from each line group, as well as an estimation of the accuracy of the method. The saturation effects observed here would result in a large systematic error if they are not taken into account when using the degenerate four-wave mixing intensity of these water line groups to calculate the flame temperature.

Highlights

Temperature measurements are of high importance in combustion research
The degenerate four wave mixing (DFWM) water line thermometry technique introduced by Sun et al.[2] uses the ratio between water line groups II and III to determine the flame temperature
To investigate the saturation behaviour of line groups II and III, DFWM excitation scans over the lines were recorded for a range of different pulse energies, in Flame 2 (1781 K) and Flame 7 (1542 K), respectively

Summary

Introduction

Temperature measurements are of high importance in combustion research. Molecular line strengths are sensitive to temperature, so accurate temperature measurements are needed to accurately measure the concentration of molecular species. A variety of laser techniques have been developed for temperature measurements in combustion environments.[1] In this work, we use the relative intensity of two water line groups to determine the temperature.

Results

Conclusion