Inerting effect of the combustion products on the confined deflagration of liquefied petroleum gas–air mixtures

Measurements on pressure evolution during the deflagrative combustion of liquefied petroleum gas (LPG)–air gaseous mixtures in the presence of their own exhaust gas, made on flammable mixtures with variable initial pressure, fuel/oxygen ratio and exhaust gas concentration, afforded determination of several flammability parameters: the maximum (peak) explosion pressure, pmax, the time to peak pressure, θmax, the maximum rate of pressure rise (dp/dt)max and the explosion index, KG. For the examined mixtures, the adiabatic explosion pressures and flame temperatures of isochoric and isobaric combustion were also calculated, assuming chemical equilibrium is reached. Adiabatic values of the explosion index were calculated from peak explosion pressures and normal burning velocities, available from the same sets of data by evaluation of p(t  ) records in the early stage of propagation (Δp≤p0Δp≤p0), according to a recent model. The scope of experiments and calculations is the examination of the exhaust gas inerting effect on flammability parameters. Their values are basic input values for evaluation of hazards associated to gaseous deflagrations and for design of safety devices.