EXPERIMENTAL INVESTIGATION OF PREMIXED FLAME CHARACTERISTICS AND STABILITY IN RADIANT BURNER

Abstract

In radiant burners, the flame stability plays a much significant role. Effects of Flame speed, excess air ratio, and firing rate on the flame stability were investigated. Combustion characteristics and stability of premixed LPG-air mixture in a porous media radiant burner are studied experimentally. A1Os and SiC were used as porous media in this work. The main objective behind this study is to determine factors affecting the flame stability and to develop empirical correlations for combustion characteristics and flame stability limits in porous media. An apparatus was built and measurements under steady state conditions were carried out. Experiments are conducted for different firing rates and excess air. ratios, as well as for two different thermal properties of the porous medias and two different porous layer thicknesses. A series of tests had been conducted and the data are presented. Results indicate that when a reaction front is stabilized within porous medium, flame characteristics are quite different from those of a free flame. The location of the flame front is influenced by the excess air ratio and firing rate. For rich fuel mixtures, flame is located above burner surface, while for lean fuel mixtures the flame is either embedded within the porous layer or located close to the surface. It has been confirmed that the solid thermal conductivity plays a significant role in the flame stabilization in porous media. Compared with free flames; the higher heat transfer leads to a faster flame propagation, which hampers flame stabilization in porous media. Heat dissipation, which depends on material properties, affects both flame position and propagation. Analysis of measurements made it possible to determine flame location in porous media for different excess air ratios and firing rates. For Ai0, flame is usually stabilized at the middle of the porous layer.