Effect of burst pressure on vented hydrogen-air explosion in a cylindrical vessel

Effect of vent burst pressure on internal pressure and flame evolution is experimentally investigated during explosion venting of rich hydrogen-air mixtures with equivalence ratio of 2 in a cylindrical vessel with a neck. Experimental results show that four pressure peaks are observed at the vessel exit under low vent burst pressures, corresponding to the following four successive stages: the vent failure, the venting of the burned gases, the maximum production rate of burned gas in vessel and the suction of gases into vessel. But under high vent burst pressure, the second and third pressure peaks disappear and the first one becomes dominant. The fourth pressure peak due to suction is kept around several kilopascals. The pressure in vessel is always characterized by single pressure peak which increases with the increase of the vent burst pressure. Under low vent burst pressures, the oscillation of internal flame due to flame-acoustic interaction results in oscillation of pressure rise rate in about 2000 Hz, and the oscillation nearly disappears under high vent burst pressures. The external flame speed does not decrease monotonously as the increase of distance away from the vent, and the maximum length of external flame is nearly independent of vent burst pressure.