Experimental study on the effects of the blocking ratio and relative position of obstacles on the methane-air continuous explosion

To investigate the comprehensive effects of the blocking ratio and the relative position of obstacles on the continuous explosion characteristics of the methane-air mixture, a series of explosion experiments were conducted in a 1.2 m long experimental tube. Methane concentration in the two connecting tubes was maintained at 10-12 vol.%, with obstacle plates featuring varying blocking ratios (Br) installed in both sections. Experimental results indicate that variations in the position of the obstacles significantly influence the shape of flame propagation. When the obstacle is positioned in the forepart of the experimental tube, the flame shape evolves through three distinct stages: spherical flame, finger-shaped flame, and vortex flame. Both the maximum flame front speed and the maximum explosion overpressure (Pmax) increase with the increasing blocking ratio. Comparatively, when the obstacle is located in the latter part of the tube, the increased turbulence intensity of the flame leads to the formation of a 'cavity' downstream as the flame interacts with the obstacle. In this scenario, the obstacles have minimal impact on both the flame front speed (Vf) and the maximum explosion overpressure. The formation of a vortex flame is a direct consequence of the interaction between the flame and the vortex, with flame acceleration occurring as the flame transitions into turbulent combustion due to the influence of the vortex.