Effect of N-2 and CO2 on explosion behavior of hydrogen-air mixtures in non-premixed state

In this paper, the suppression effects of non-premixed inert gas (N2, CO2) on hydrogen-air explosion behaviors are experimentally studied. The effects of N2 and CO2 addition on flame propagation, explosion pressure and flame length are analyzed. The results show that N2 and CO2 can effectively reduce the explosion hazard in nonpremixed state. The mixing process of non-premixed gases leads to the development of turbulent flame, but the suppression of inert gas on explosion exceeds the promotion of turbulent flame. Under the action of N2 and CO2, the energy of the flame decreases, and the front contour becomes blurred. When the fuel zone is only set at the ignition end, with the suppression of N2 and CO2, the maximum explosion pressure is reduced by 35.1% and 50.6%, respectively. It is worth noting that the high-frequency periodic oscillation and pressure soaring appear in the pressure histories, which are attributed to the rapid phase transition of water. Furthermore, the two inert gases can significantly reduce the chemical reaction rate and heat release rate during the explosion, which is reflected in the decrease of the maximum flame length. It is found that N2 and CO2 have different explosion suppression effects and mechanisms, but CO2 has better suppression performance on hydrogen-air explosion.