Coupling effects of venting and inerting on hydrogen-air explosions at elevated static activation pressures

Abstract

The effect of varying CO2 addition ratios (λ) on the internal and external pressure characteristics of vented hydrogen-air explosions with an equivalent ratio of 1.5 at elevated static activation pressures (Pstat) of 0.5–2.5 bar was experimentally investigated. The results showed that the inerting effect of CO2 improved the effectiveness of the venting and allowed equilibrium venting at small vent areas and elevated Pstat, further improving the stability and reliability of the hydrogen-air explosive venting technique. However, it was recognized that increasing the CO2 content beyond 10–15% tended to decrease the effectiveness of the maximum pressure rise rate reduction. For external pressure, the peak external explosion pressures decreased significantly as the λ increased. At a fixed λ, the peak external explosion pressure increased and then decreased as the Pstat increased, reaching a peak at 2.0 bar. Based on the laminar flame venting mechanism, a predictive model for the equilibrium venting area with coupled inerting and venting effects was developed. The pseudo-source theory was introduced to establish a model that allowed estimating the peaks of external explosion pressures at elevated Pstat.