Effect of vent conditions on internal overpressure time-history during a vented explosion

Vented explosion experiments of ethylene-air mixtures were conducted in a custom-designed 2 × 1.2 × 0.6 m3 steel chamber under three vent conditions to study the effect of vent size and vent type on overpressure under different concentrations. The experiment results show that vented explosion behaviors are related to various vent conditions. The rupture pressure of vent film at different concentrations are the same with static vent pressure while the rupture pressure of vent panel increases as the concentration approaches the stoichiometric concentration. Double-peak pressure curves were recorded under small size vent conditions, while overpressure curves with only one peak were recorded under large size venting. Analysis indicates that the peak overpressure and rate of pressure increase under large size venting are mainly affected by the rupture pressure and the concentration of combustible gas, respectively. Moreover, secondary explosion, due to the backflow of external gas, will occur in high concentrations under large size vent conditions. In the case of small size vent condition, the value of first peak P1 is mainly determined by the rupture pressure, while the value of second peak P2, and the rates of increase to P1 and P2 are mainly affected by the concentration. There is a clear difference between the recorded values of P2 at two measurement points, which indicates that there is a pressure gradient induced by small size vent conditions due to the change of flow cross-section. This work provide a practical reference for the safety design of the explosion venting.