Hydrogen cloud explosion evaluation under inert gas atmosphere

This paper is aimed at evaluating the hydrogen cloud explosion under inert gas atmosphere experimentally and numerically. The results demonstrate that only under Ar, N-2 and CO2 atmosphere, the lean and stoichiometric hydrogen flame tends to be unstable. The Markstein length of Ar, N-2 and CO2 is less than zero and the decreasing order is Ar, N-2 and CO2. Except for CO2, the average flame propagation velocity, maximum explosion pressure, maximum pressure rise rate, positive pressure impulse and explosion pressure attenuation decrease monotonously in the order of He, Ar and N-2. For various equivalence ratios and inert gases, the explosion pressure releases into the far field at the sound speed and attenuates with distance. Due to the fact that the explosion pressure is closely related to laminar burning velocity, the explosion pressure suppression by inert gas is revealed by analyzing the factors affecting laminar burning velocity. As equivalence ratio increases, the adiabatic flame temperature plays a more important role in affecting laminar burning velocity than thermal diffusivity. For different inert gases, the effect of thermal diffusivity on laminar burning velocity is obviously greater than adiabatic flame temperature. Besides, the third-body effect of various inert gases increases gradually until Phi = 1.4. and then decreases with increasing equivalence ratio. For a given equivalence ratio; the increasing order of third-body effect is He, Ar and CO2.