Premixed methane/air gas deflagration simulations in closed-end and open-end tubes

The overpressures, flame velocities and flow speeds were investigated in closed-end and open-end tubes via numerical simulations. Our results suggest that the tube geometry influences the evolution of these parameters. The peak overpressure initially decreased and eventually increased with the aspect ratio in both types of tubes. The flow speed initially increased and then decreased with the propagation distance in the closed-end tube, but it increased with increasing distance in the open-end tube. Empirical equations relating the peak overpressure and the peak flow speed are presented. The flame velocities in the open-end tubes were always greater than those in the closed-end tubes, especially the maximum flame velocity. The open end promoted flame acceleration, while the closed end resulted in near-wall deceleration. The results provide a reference for future limited-space gas explosion studies.