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

Abstract

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 C_d (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 S_ui. A qualitative interpretation of the results is given, based on the concept of additional heat release in the flame front by reactions involving hydrofluorocarbons.