Explosion characteristics of a methane/air mixture at low initial temperatures

In this paper, the explosion characteristics of a methane-air mixture at low initial temperatures (up to 113 K) and elevated pressures were measured. Various parameters, such as explosion pressure, rate of the explosion pressure rise, combustion duration and flame development duration were obtained for the initial temperature range of 123-273 K. The results indicated that the maximum explosion pressure and the maximum rate of explosion pressure rise reached peak values at the equivalence ratio of 1.1. With the increase in initial pressure, the maximum explosion pressure increased significantly, and the maximum rate of explosion pressure rise increased linearly because of a larger density of the flammable mixture within the explosion vessel. With the decrease in the initial temperature the maximum explosion pressure increased monotonically, whereas the effect of initial temperature on the maximum rate of explosion pressure rise was negligible because of two opposing aspects: an increase in the amount of flammable mixture and a decrease in the flame propagation speed. Both the combustion duration and the flame development duration increased with the increase in initial pressure and decreased with the increase in initial temperature. Finally, at an equivalence ratio of 1.0, two empirical correlations were obtained to calculate the combustion duration and the flame development duration.