Characterization of explosion propagation of coal dust deposited by gas explosion convolutions in closed pipelines

Abstract

To explore the propagation characteristics of gas explosion-induced coal dust detonations in enclosed pipelines, a custom-developed experimental system was employed for gas explosions involving accumulated coal dust. Various aspects were focused such as explosion pressure, flame dynamics, and the interplay between pressure and flame in the context of different gas and coal dust concentrations. Additionally, Fluent Numerical simulation software was utilized for analyzing the dispersion behavior of coal dust. The results reveal that the peak explosion pressure inside the closed pipeline is the highest at a 10% gas concentration, surpassing the maximum pressures observed at 12% and 8% concentrations. At a gas concentration of 10% and coal dust mass concentration of 250 g/m3, the explosion pressure exhibits a unique pattern: initially increasing, then decreasing, and subsequently rising again in the gas phase, followed by a continuous ascent in the coal dust phase. As the coal dust concentration increases, this pattern remains evident, with a persistent upward trend in the coal dust section. Conversely, at 8% and 12% gas concentrations, the maximum explosion pressure consistently rises with increasing coal dust concentrations, but shows a declining trend at 10% gas concentration. Furthermore, the time taken for the flame front to traverse the pipeline is positively correlated with the distance traveled. The flame front reaches various checkpoints more rapidly at a 10% gas concentration than at 12% and 8%. The flame’s propagation speed first increases and then decreases over distance, reaching its fastest at 10% gas concentration. The explosion pressure-time curve during a gas explosion in a closed pipeline showcases two peak values. The initial peak is caused by the shock wave preceding the gas explosion. As the flame advances into the coal dust section, the pressure concurrently begins to rise, reaching its second peak as it synchronizes with the flame’s peak. Following the flame signal’s disappearance, the pressure gradually diminishes until the reaction ceases. In the enclosed pipeline, the precursor shock waves and reflected waves contribute to the dispersion of coal dust, forming a “vortex-like” dust cloud. This formation enhances the interaction between the coal dust and the deflagration wave. When the coal dust concentration is fixed, the degree of dispersion at 10% gas concentration is more effective than at 12% or 8%. Furthermore, at a constant gas concentration, the dispersion degree of coal dust decreases as its mass concentration increases.

Keywords

• closed pipeline
• gas explosion
• coal dust explosion
• coal dust curling
• flame propagation characteristics
• pressure flame coupling