Experimental study of the characteristics of explosions generated by methane mixtures, as a function of the type of atmosphere and environmental conditions

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. This paper studies the ignition of different methane–air mixtures as a function of the type of mixture (methane–air, methane–nitrogen–oxygen), the kind of atmosphere (homogeneous, stratified) and the environmental conditions (initial temperature, pressure, and humidity). For this purpose, the Rock Dynamics research group of the University of Oviedo has designed and manufactured an explosive chamber, quasi-spherical in shape, instrumented with dynamic pressure sensors and accelerometers. With the results obtained after a laboratory-scale experimental campaign, pressure-concentration graphs were plotted, obtaining the explosion limits of the different mixtures. Higher oxygen concentrations (O2) have therefore been found to increase the upper explosive limit of mixtures. However, increasing methane (CH4) concentrations lead to different behaviours, depending on the type of mixture. The kind of atmosphere does not seem to affect the recorded pressures, as they are similar for homogeneous and stratified atmospheres. Finally, initial pressures above atmospheric lead to higher detonation pressures, while a high initial humidity content decreases the likelihood of explosion.