Effect of obstacle shape on the deflagration characteristics of premixed LPG-air mixtures in a closed tube

Abstract

In the present research, the deflagration behaviors of premixed LPG-air mixtures with volume fractions from 4% to 8% and various obstacles at a block ratio of 0.6 were experimentally investigated in a closed tube with a length-diameter ratio of 20.4. The parameters such as explosion pressure, explosion time, pressure rise rate, and revised deflagration index were obtained. Moreover, the flame propagation behaviors were recorded, and the structural evolution of the flame front and the corresponding flame speed were identified and then analyzed. The obtained results showed that the net square and perforated disc obstacles increase the flame speed the most, and the peak value reaches 256.2 m/s. When the flame front reaches close to the end of the tube, the combined effects of the reflected deflagration wave and the vortex-induced by the turbulence drive the unburned mixture to propagate to the burned zone, resulting in a backward flame. The maximum explosion pressure and the revised gas deflagration index of the LPG-air mixture increased for six kinds of obstacles with different shapes. The time to peak pressure was greatly reduced. The mesh square and perforated disc obstacles enhanced the pressure parameters the most. The obtained results are of significance in providing fundamental data on the explosion of LPG-air mixtures, providing theoretical guidance for the design of LPG-related devices and structures, and being useful to develop the corresponding explosion mitigation technology.