Experimental study and modal analysis of methane explosion-induced deposited coal dust participation

This study investigates the evolution of wave systems during methane explosions involving deposited coal dust in enclosed pipelines. The flame front velocity distribution was measured using schlieren image velocimetry. Proper orthogonal decomposition and dynamic mode decomposition techniques were applied to identify the primary flow structures and fluctuation frequencies in the flow field during the dust-lifting process. The experimental results indicate that while deposited coal dust does not significantly affect the shock wave, it notably increases flame velocity, with a maximum acceleration of up to 180 m/s, and extends flame propagation distance. The primary cause of flame enhancement is the interaction with reflected shock waves. The pressure gradient created by these reflected waves generates Archimedean forces on the particles, driving the coal dust toward the flame. This early contact between the coal dust and the flame intensifies the methane explosion. Modal analysis further reveals that the shear layer is the most critical flow structure during dust-lifting, with vortex shedding being the main driver of flow field oscillations.