MEASUREMENT OF INVERSE DIFFUSION FLAME QUENCHING LIMITS

Abstract

Quenching limits of inverse diffusion flames were measured for different conditions. The flames were laminar and axisymmetric and were obtained by injecting various oxidizers into fuels. Burner inside diameters were 0.75, 1.53, 3.02, 4.56, and 10.1 mm. Oxygen mole fractions were 0.21, 0.3, 0.4, and 1, and the balance was nitrogen. Fuels were methane, ethylene, and propane. The flames were observed in a weak co-flow of fuel inside a glass chimney. The flames were ignited at relatively high oxidizer flow rates, after which the oxidizer flow was reduced until extinction. The typical heat release rate of quenching inverse flame ranged from 1 - 2 W, compared to a typical heat release rate of quenching normal hydrocarbon flames of 3 W. The quenching limits of inverse flames were generally independent of burner diameter, were proportional to the fuel quenching distance in premixed flames, and scaled with oxygen mole fraction to the power of -1.5. The results may help assess the hazards of firefighter respirator leaks in underventilated fires.