Gas Movements in Front of Flames Propagating Across Methanol

Abstract

The gas velocity profiles in front of the leading edges of flames propagating across methanol at initial temperatures Ti from -5°C to 35°C were measured by using high-speed schlieren photography combined with a hot gas tracer technique. For T_l much lower than the flash point T_lf, any appreciable gas movement could not be observed in front of the leading flame edge. Therefore, as considered in previous studies, preheating in this case was supposed to be mainly caused by convection in the liquid phase. For T_l slightly lower than T_lf, the maximum value of the extrapolated gas velocity across the flame front was found to be a fairly high value. This result could be consistently intepreted by considering the increase of the methanol vapor concentration in front of the leading flame edge due to preheating. For T_l above T_lf, the experimentally predicted aspects of the gas movements near the leading flame edges were found to coincide with the theoretically predicted aspects for the flame propagation through layered mixtures.