Experiments on vented H2/air explosions with a hinged vent panel: Effects of surface density

The effect of inertial vent covers on deflagrations of fast-burning gases, such as hydrogen, has received limited attention, and recommendations for their safe venting are unavailable. To this end, experiments on vented explosion of H₂/air mixtures, ignited from the center of a 1-m³ chamber with a top vent covered by hinged aluminum plates of various surface densities ($W_s$), were performed at initial temperatures and pressures of 290 K and 100 kPa to investigate the effects of $W_s$ on the flame evolution and pressure profile within and outside the vented vessel. Three pressure sensors (PS1-PS3) were used to record internal overpressure and another pressure sensor (PS4) was employed to monitor external overpressure. Current tests showed some unexpected results, which were inconsistent with previous research and available models. In this study, $P_{\max }$, $P_{red}$, and $P_{ext}$ are focused on; $P_{\max }$ refers to the maximum internal overpressure recorded by PS1-PS3, $P_{red}$ represents the highest $P_{\max }$ monitored by PS1-PS3 for a certain $W_s$, and $P_{ext}$ denotes the maximum external overpressure obtained by PS4. Experimental results reveal that for a given $W_s$ , the highest and lowest $P_{\max }$ are always observed at the bottom and the center of the chamber, respectively. With the increase of $W_s$ from 0 to 18.9, $P_{ext}$ first increases and then decreases, and it reaches its highest value when $W_s$ is increased to 8.1 kg/m². As $W_s$ increases from 0 to 18.9, $P_{red}$ first increases with $W_s$ and reaches its maximum of 93 kPa at $W_s$ = 8.1 kg/m² and thereafter decreases when $W_s$ is increased to 13.5 kg/m², and a further increase in $W_s$ has a negligible effect on $P_{red}$. In comparison with an inertia-free vent cover, when a hinged vent panel is used, the external fireball looks more oblate, and the maximum flame length decreases with increasing $W_s$. The results of the study can provide a valuable reference for the explosion-proof design of inertial vent covers and hydrogen explosion risk assessment.