Influence of the oxygen content in the oxidizing medium on the combustion of fuel–oxidizing medium–hydrofluorocarbon near-stoichiometric mixtures

The effect of the oxygen content in the oxidizing medium (O2–N2 mixture) on the characteristics of the combustion of gaseous fuel (hydrogen, methane)–oxidizing medium–hydrofluorocarbon (trifluoromethane CHF3, pentafluoroethane C2HF5, or perfluorobutane C4F10) is experimentally studied. The oxygen concentrations in the oxidizing medium are 15, 20.6 (air), and 25 vol %. The dependences of the maximum explosion pressure ΔP max, maximum explosion pressure rise rate (dP/dt)max, and laminar burning velocity Sui on the hydrofluorocarbon content at various oxygen concentrations in the oxidizing medium are determined. It is shown that, at a relatively low deterrent content Cd (up to 30–50% of the minimum inhibitory concentration of the hydrofluorocarbon, i.e., up to 30–50% of the hydrofluorocarbon content at the “peak” point of the inhibition curve), the maximum explosion pressure is only slightly dependent on C d. It is demonstrated that the larger the molecule of the hydrofluorocarbon, the higher is its inhibitory ability in terms of (dP/dt)max and Sui. A qualitative interpretation of the results is given, based on the concept of additional heat release in the flame front by reactions involving hydrofluorocarbons.