Flame acceleration process of premixed hydrogen in confined space with different obstacle shapes

Obstacles can greatly stimulate the detonation power of gas, and have great research value in industrial safety and energy utilization. Thus, in this work, the combustion characteristics of hydrogen under different shape obstacles are investigated. The important parameters for the evaluation of the gas combustion characteristics are analyzed, including the flame structure, flame propagation velocity and explosion overpressure. The results show that it is difficult for the flame front to recover to the regular front after passing through grid-type obstacles with many voids. To further understand the influence of the obstacle shape on the flame structure evolution, the change in the flow field before and after the flame approaches the obstacle is analyzed. The results show that the flow field formed by the combustion products can be seriously unstable after the flame front passes through gridtype obstacles, resulting in a severe distortion of the flame front. Moreover, the influence of the obstacle shape on the flame propagation velocity under different blockage ratios is compared. The results show that the single-type obstacle has a better effect on the acceleration of the flame, and it is more sensitive to the increase in the blockage ratio. The grid-type obstacle can improve the sensitivity to the blocking rate by reducing the void area. Furthermore, by analyzing the pressure growth rate, it is found that the influence of the obstacle shape on the explosion overpressure under different blockage ratios is the same as that of the flame propagation velocity. This work can provide some guidance for industrial explosion prevention and control and energy power system design.