Burning velocity evaluation from pressure evolution during the early stage of closed-vessel explosions

In the present paper, a comprehensive set of data on explosions in a spherical and a cylindrical vessel with central ignition was examined in order to check the validity of the cubic law, empirically found by many authors for explosions in small- and medium-size closed vessels. Experiments were performed on propylene–oxygen mixtures, in the presence of various additives (Ar, N2, CO2, CH2BrCl or exhaust gases), at total initial pressures p0 from 0.3 to 1.3 bar. For this pressure range, the cubic law was found valid for pressure rise Δp≤p0 and the cubic law constants were evaluated by a non-linear regression analysis. These constants were further used to compute the burning velocities of the examined systems according to the isothermal and adiabatic compression models. This simple and reliable method for burning velocity determination may find an useful application to complex systems, formed either by a composite fuel (landfill gas, gasoline, Diesel fuel) and air or by single fuel–air mixed with composite additives (i.e. their own exhaust gases).