Flame propagation characteristics of methane explosion under different venting conditions

Abstract

Air mixed with methane commonly causes explosion accidents. Explosion vents can discharge the explosion pressure and release energy to reduce the explosion impact. Explosion vents are widely applied to gas transportation pipelines and other pressure equipment. To determine the influence of explosion vent areas and types on dynamic characteristics of methane flame propagation, in this study, an explosion pipe system was established to explore the effects of the 22.89-cm2 circular (1#), 15.20-cm2 circular (2#), 9.07-cm2 circular (3#), and 15.20-cm2 cross-shaped (4#) vents on flame propagation of methane explosion and to compare these effects with those of a closed pipe. The experimental results indicated that the explosion vent accelerated flame propagation velocity (v) and considerably reduced explosion pressure (P) and flame temperature (T) compared with the closed pipe results. v, T, and P reached maximum values at 10 vol% methane concentration. As the vent area increased, the v of the three circular vents increased. Flame propagation velocity in 1#, 2#, and 3# increased by 23.13 %, 21.57 %, and 4.55 % compared with that of the closed pipe (13.40 m/s), respectively. Compared with the closed pipe values of 0.973 MPa and 1678.13℃ for P and T, decreases of 10.30 %, 12.50 %, 38.00 %, and 1.82 %, 10.53 %, 11.22 % were observed in 1#, 2#, and 3#, respectively. Under equal explosion vent areas (15.20 cm2) but different vent types (2# circular and 4# cross), as the equivalent diameter of vents increased, P and T decreased by 12.50 %, 20.91 %, and 10.53 %, 10.01 %, and v increased by 21.57 % and 12.61 %.