Spectroscopic Survey of Energy Distributions of OH, C2, and CH Radicals in Low Pressure Acetylene-Oxygen Flames

Abstract

Rotational and vibrational ``temperatures'' from electronic transitions of OH, C2, and CH radicals have been measured in detail as functions of position in low pressure acetylene-oxygen flames. Pressures were varied from 0.8 to 6.0 mm Hg. Trends of ``temperature'' are presented as functions of mixture, pressure, position, mass flow rate, and burner size. Abnormalities in ``temperature'' are discussed. Evidence is presented for the existence of a newly discovered region at the base of the flame. This region is about 110 the visible flame thickness and is characterized by strong emission of C2 and CH relative to OH and by relatively high ``temperatures'' of C2 and CH. Just above this region the OH rotational ``temperature'' is very high, about 9000°K, and is independent of pressure.