Fire Safety Science Digital Archive

An experimental investigation of the characteristics of combustion of rich near-limit gaseous mixtures hydrogen – oxidizer (mixture of oxygen and nitrogen) – diluent (trifluoromethane CF3H, pentafluoroethane C2F5H, perfluorobutane C4F10, AKM agent) in a closed vessel of volume 4.2 dm3 at oxygen contents in the oxidizer 15, 20.6 and 25% (vol.) was executed. Dependences of a maximum explosion pressure ?pmax and a maximum explosion pressure rise rate (dp/dt)max on a diluent concentration Crel have been determined. It was found that for the most part of the investigated gaseous mixtures the maxima in the dependences of ?pmax on Crel take place, but in the case of the dependences of (dp/dt)max on Crel the maxima take place for the pentafluoroethane C2F5H only. A qualitative interpretation of the observed results was given, which is based on two effects: a) an active participation of the diluents in a chemical conversion in a flame front (in many cases with an additional heat release); and b) an existence of two different kinetical regimes of chain-branching combustion processes. It was found that C4F10 and AKM are the most effective inhibitors in relation to a flame propagation in rich near-limit mixtures hydrogen – oxidizer – diluent.