Chain explosion behaviors induced by discontinuous methane/air distribution

Abstract

A chain explosion of combustible gas is common and more violent, resulting in greater casualties and property losses, but few researches on its explosive behavior in the large-scale tunnel have been done. Based on the fluid dynamics and combustion theories, a numerical model for simulating the process of flame and shock wave of upstream explosion inducing the downstream gas explosion was proposed to understand the mechanism of chain explosion. Accordingly, the chain explosion propagation of methane was examined by CFD simulations, emphasizing on the peak pressure and temperature, flame front, and flame propagation velocity. The results revealed that the chain explosion significantly increased the hazard scopes of death and thermal damage. Fuel-rich (v/V) chain explosions with the small middle air area (Lmid) were more destructive. However, the volume of upstream explosion zone (Vup) had little influence on the hazard range within 240 m but a great effect on the peak pressure and flame velocity. Furthermore, the unique finding was that the large middle air area (Lmid) didn't reduce the thermal damage range unless it exceeded a threshold. These findings have important reference value for comprehending the mechanism of sustaining multiple explosions in an accident and its prevention measures.