Explosion characteristics of methane-air mixtures in a spherical vessel connected with a duct

With the aim of exploring explosion characteristics of methane–air explosive mixtures in a ducted vessel, a 20 l spherical vessel connected with a 2813 mm long duct was employed. The experimental setup was comprised of a wafer check valve, which kept the methane–air mixture initially confined and opened at the time of explosion. The system introduced turbulence to the gas mixture during operation and pyrotechnic igniters were employed in the investigation. This approach assisted to obtain data that can be correlated with real world ducted explosion accidents where the explosion initiates in the presence of strong ignition energies and in turbulent states of methane–air mixtures. This study shows that the explosion severity can be very high in the turbulent field of methane–air mixture and in the presence of strong ignition energies. The pressure rise in the vessel and the flame speed along the length of the duct were found to be higher in the present study when compared to data obtained with quiescent methane–air mixtures and low ignition energies. The impact of the duct length and pyrotechnic igniters’ energy on reduced peak explosion pressure was characterised. The rate of pressure rise, a parameter linked to the burning rate, increased from the ducted to the vented configurations of the explosion test units.