Reliability and applicability of empirical equations in predicting the reduced explosion pressure of vented gas explosions

Abstract

Explosions caused by the rapid release of energy from the expansion of burnt gases, along with an associated pressure rise, in an enclosure can be mitigated by venting. Many empirical equations have been derived based on vented gas deflagration phenomena. In the present paper, four empirical equations for gas venting were reviewed, i.e., NFPA 68, the European Standard (EN 14994), Molkov et al. and Bradley and Mitcheson in order to assess their reliability and applicability for predicting the reduced explosion pressure (Pred) of propane-air, methane-air and hydrogen-air mixtures at three different chamber-scale volumes. The results showed that the NFPA 68 correlation is the most appropriate method for predicting Pred, while Bradley and Mitcheson gave values closer to those of experimental data for propane-air mixtures in medium and larger chambers, respectively. However, none of the predicted correlations was able to provide a reasonable prediction of Pred in a hydrogen-air explosion. In addition, these predicted correlations showed greater discrepancies in Pred values in the presence of vent area, ignition position and obstacles.