The explosion overpressure field and flame propagation of methane/air and methane/coal dust/air mixtures

The explosion of the methane/air mixture and the methane/coal dust/air mixture under 40J center spark ignition condition was experimentally studied in a large-scale system of 10m³ vessel. Five pressure sensors were arranged in space with different distances from the ignition point. A high-speed camera system was used to record the growth of the flame. The maximum overpressure of the methane/air mixture appeared at 0.75m away from the ignition point; the thickness of the flame was about 10mm and the propagation speed of the flame fluctuated around 2.5m/s with the methane concentration of 9.5%. The maximum overpressure of the methane/coal dust/air mixture appeared at 0.5m. The flame had a structure of three concentric zones from outside were the red zone, the yellow illuminating zone and the bright white illuminating zone respectively; the thickness and the propagation speed of the flame increased gradually, the thickness of red zone and yellow illuminating zone reached 3.5cm and 1cm, the speed reached 9.2m/s at 28ms.