Effect of burst pressure and vented area on vented hydrogen explosions

The experiments were carried out in a 2.25-m-long shock tube with a flanged ball valve and investigated the effects of hydrogen concentration, vented area and bursting pressure on hydrogen explosive venting. The main peaks in typical pressure–time curves under different experimental conditions are explained by physical mechanisms and the temperature distribution of the secondary explosion flame is analyzed. Both the increase in bursting pressure and the decrease in vented area can cause an increase in the maximum explosion pressure inside the pipe. However, the maximum explosion pressure outside the pipe shows an opposite trend. The secondary explosion flame temperature decreases with decreasing vented area and hydrogen concentration, the highest temperature under thin film conditions followed by non-film and thick film, with a maximum value at 60% H₂. The maximum explosion pressure, both inside and outside the pipe, increases and then decreases with increasing hydrogen concentration, reaching a maximum at 40% H₂. In addition, the safety radius calculated using the thermal radiation criterion is larger than that calculated using the overpressure damage formula (PROBIT equation) under 50% and 60% H₂. It is safer to use PROBIT equations at 30% and 40% H₂ to evaluate the safety radius.