Influence of Initial Pressure and Vessel's Geometry on Deflagration of Stoichiometric Methane-Air Mixture in Small-Scale Closed Vessels

In the present work, experimental data on closed vessel explosions of stoichiometric methane-air mixture are reported for mixtures at ambient initial temperature and various initial pressures between 0.2 and 1.2 bar for small-scale closed vessels. The data are collected as pressure-time records in a spherical vessel and two cylindrical vessels with central ignition. The influence of initial pressure and vessel size and shape on maximum rates of pressure rise and deflagration (severity) indices is examined. In each explosion vessel, a linear correlation of the maximum rate of pressure rise with the initial pressure is found. At all pressures, the rates of pressure rise and the severity factors reached in the spherical vessel exceed those reached in cylindrical vessels as a result of differences in heat losses within these enclosures. The experimental deflagration indices are compared with the adiabatic deflagration indices, calculated by means of peak explosion pressures and laminar burning velocities; the heat losses in various enclosures explain the observed differences. The peak explosion pressures and laminar burning velocities are also used to calculate the dimensionless deflagration indices, found to be less influenced by vessel's size and shape.