Interaction of a preexisting flame with flowing flammable fuel-air mixtures

Abstract The interaction of a preexisting stationary pilot flame with flammable fuel-air mixtures slowly moving in counterflow to the burnt pilot gas have been investigated as a function of the fuel concentration, the fuel-air mixture flow rate, and the characteristics of the pilot flame. Particular attention has been devoted to methane-air mixtures. Temperature profiles and concentration profiles of reactants and major final products have been measured and local flammability tests have been conducted in the combustion chamber to analyze the system. The results show that, under conditions which locally favor dilution and heating of the flammable fuel-air mixture by the burnt pilot gas, a combustion reaction burns the diffusing reactants in the upward flux of burnt pilot gas. This local reaction can either make nonflammable the surrounding atmosphere by liberating burnt gas, which increases the local dilution of unburnt gas, or ignite the remaining fuel-air mixture if both fuel and air are in proper proportions.