A New Approach to Spatially Resolved Flame Temperature Measurements

Abstract

Spatially resolved flame temperatures are spectroscopically measured using the slope method, over small (≃0.7 μl), relatively homogenous volumes of flame gases. The spatial resolution is uniquely obtained by introducing Co as a thermometric species into isolated volumes via the use of a droplet injection technique. By this method the emission of light is restricted to a limited volume, whose position in the flame can be accurately determined and controlled. Vertical resolution is determined by the width of the entrance slit of the monochromator employed (100 μm in this study), and horizontal resolution is limited by the width of the emission cloud formed by the injected droplets (1 to 3 mm). The possibility of self-absorption effects are greatly reduced because of the short radiation path length involved. The performance of the method is illustrated by its application to the spatial temperature mapping of the secondary reaction zone of a cylindrical air-acetylene flame. The effects of N2 as a sheathing gas and flame stoichiometry on the radial and vertical temperature distribution of the flame are also investigated. It is determined that a large, virtually isothermal, central zone exists in the flame.