Temperature measurements in a vapor axial deposition flame by spontaneous Raman spectroscopy

Abstract

Spontaneous Raman spectra of oxygen and nitrogen have been used to determine temperatures in flames produced by a vapor axial deposition (VAD) burner, both with and without silicon tetrachloride added to form silica particles. VAD flames in the absence of silicon tetrachloride contain steep temperature gradients in both the axial and radial directions. The addition of silicon tetrachloride produces substantial changes in flame structure, as characterized by the movement of an axial thermal front to a location higher in the flame. This indicates that the effects of silicon tetrachloride upon flame properties cannot be neglected in computational models designed to predict silica deposition rates. These results also show that spontaneous Raman scattering measurements are feasible in silica-laden VAD flames and can yield insight into the structure of such flames. Because of the presence of large thermal gradients, the high spatial resolution obtained in these measurements (0.6 mm of the laser beam was imaged) represents the minimum required to obtain accurate measurements of temperature and species concentrations in these complex diffusion flames.