Multiple explosions induced by the deposited dust layer in enclosed pipeline.

This paper presents a numerical model for simulating the progress of deposited dust explosion in the enclosed pipelines and the corresponding results. The model reveals the influence of the pipeline length-diameter ratio and the total amount of the deposited dust on the multiple explosions. In the enclosed pipelines with three different length-diameter (L/D) ratios: 50:1, 100:1 and 200:1, the gas explosion cannot spread to the end when igniting the local (7 vol. %) methane-air mixture. The two-phase explosion can be induced by the local gas explosion after adding the deposited coal dust. In the pipelines with 50:1 and 100:1 L/D ratios, an explosion is observed from the closed end to the ignition end defined as reverse explosion. The deposited dust amount has an important influence on the occurrence of reverse explosion. When the amounts of deposited dust are too large or too small, the reverse explosion cannot be observed in the closed pipeline. When the concentration of the suspended coal dust kicked up by the leading pressure wave is in the range of 0.2- 0.8 kg/m3, the reverse explosion is more likely to occur.