Effects of ignition location and vent area on the external explosion in vented hydrogen explosions

Abstract

In the current study, effects of vent area and ignition location on vented stoichiometric hydrogen-air mixture explosion were experimentally and numerically investigated. Internal and external pressure-time curves and flame behavior were focused. For low vent coefficient Kv = 4, the maximum internal pressure results from the vent rupture for front ignition and the external explosion for center ignition and rear ignition. The maximum internal pressure for IL4 is larger than those for other ignition locations. The maximum internal pressure is induced by the internal chemical reaction and increases monotonically with Kv for different ignition locations, and the maximum internal pressure occurs at center ignition as Kv ＞ 4. Mach disk in external flame begins to appear when Kv increases to 12.75 for front ignition and 8.65 for other ignition locations. External pressure histories show two pressure peaks P1 and P2 for center and rear ignitions. Although the pressure peak P1 results from the leading pressure wave, the pressure peak P2 is induced by the venting flame and external explosion for center ignition and rear ignition, respectively. Only one pressure peak was recorded for center ignition. For front ignition and IL2, the maximum external pressure increases with Kv while it firstly increases and then decreases for center ignition, IL4 and rear ignition, the critical value is Kv = 17.36 for center ignition and IL4 while it is Kv = 8.65 for rear ignition.