Effects of vessel height and ignition position upon explosion dynamics of hydrogen-air mixtures in vessels with low asymmetry ratios

The explosion characteristics of hydrogen-air mixtures in a wide range of equivalence ratios in closed vessels were investigated experimentally. The maximum explosion pressure, maximum pressure rise rate (along with deflagration index), explosion time and heat loss were evaluated. Three vessels with low asymmetry ratios (H/D) of 0.146, 0.244 and 0.341 were used to study the effect of vessel height on explosion parameters, in which H and D are the height and inner diameter of the vessel, respectively. In the H/D = 0.341 vessel, the effect of ignition position on explosion behaviors was also considered. The results show that, with the increase of the vessel height, the maximum explosion pressure increase correspondingly, and the explosion time decreases orderly. In the lowest height vessel (H/D=0.146), the ignitor-regulating column acts as a 'turbulence-generator'. Thus, the maximum rate of pressure rise could be increased significantly while the heat loss could be decreased. Compared with the central ignition scenario, both the maximum explosion pressure and maximum pressure rise rate are decreased for the asymmetrical ignition; meanwhile, the explosion time and the heat loss during the explosion are increased.