Details

Confined and vented explosion tests were performed in an 8-m3 vessel with stoichiometric propane-air mixtures. Small vent areas consistent with the size of typical vessel-pipe connections were explored, ranging between 0.13 m2 and 0.0079 m2. These vent areas generated high reduced pressures, between 3.2 barg and 7.2 barg. Flame arrival times at the vent and the external flame shape were captured using highspeed video. Five distinct phases during the vented explosions were identified: (i) flame propagation from the point of ignition to the vent; (ii) external explosion consuming previously vented unburned mixture; (iii) short flame-jet; (iv) rapid increase in pressure and flame length up to peak explosion pressure; (v) decay of pressure and flame length. It was found that smaller vent areas result in later flame arrival at the vent, higher peak pressures, weaker external explosions, shorter flame-jets, and a smaller degree of combustion acceleration in phase (iv). A previously developed model for confined, simply-vented and pipe-vented explosions is compared against the experiments. It is shown that early pressure transients, and flame arrival times at the vent, are predicted with reasonable accuracy.