Determination of the explosion parameters of methane-air mixtures as function of the ignition source and the volume and shape of the explosion chambers

The combination of methane -air can cause potentially explosive mixtures, which in contact with an energy source can ignite, resulting not only in the destruction of infrastructure but also in the death of people. The aim of this paper is to study the ignition of methane -air mixtures with different concentration of methane, as a function of the ignition sources used and the volume and geometry of the explosion chamber. For this purpose, the 'Dynamic Behaviour of the Rock mass (DinRock)' research group of the University of Oviedo has designed and manufactured 3 explosion chambers of different sizes and shapes, instrumented with dynamic pressure sensors and accelerometers. In addition, the ignition process has been recorded with a high-speed camera. With the results obtained after a laboratory-scale experimental campaign, the maximum pressure reached, the pressure gradients and the acceleration of the pressure waves were analysed. Thus, it has been determined that the maximum pressure reached is independent of the ignition source used and the chamber volume, but not of the chamber geometry. Methane (CH4) concentrations between 8.0 and 9.0% generated the highest pressures between 1.5 and 2.5 MPa. A correlation between peak acceleration and peak pressure has also been established allowing to identify whether a deflagration or a detonation has occurred.