Characteristics of the combustion of mixtures of combustible gases with refrigerants during downward flame propagation

Abstract

An investigation of the limiting conditions of combustion in mixtures of hydrocarbons with refrigerants during downward flame propagation is described. The task undertaken was twofold: to determine whether mixtures at the extreme points of the ignition regions are stoichiometric during combustion to CO and H/sub 2/O, and to investigate the normal burning velocity of limiting mixtures as a function of the refrigerant content, including those refrigerants having an inhibiting effect on combustion. Propane and propylene were each mixed with 1,1,2-trifluorotrichloroethane and with 1,2-dibromotetrafluoroethane and ignited in a combustion chamber with a stabilizing screen and with photodiodes to record the normal burning velocity. The ignition region during downward propagation of the flame was found to be considerably narrower than in the case of upward propagation. Analysis of the compositions of the limiting mixtures corresponding to the stabilization points revealed that the concentrations of combustibles in them are close to stoichiometric. The investigation indicates that the mechanisms of flame extinguishment are probably different for downward and upward propagation, but further investigations are necessary to clarify this problem.