Experimental research on the inhibition of methane/coal dust hybrid explosions by the ultrafine water mist

This experimental study focused on the inhibition of ultrafine water mist on methane/coal dust hybrid explosions inside the closed vessel. Combined with the change of explosion parameter (including the flame propagation characteristics, explosion pressure, pressure rising rate and flame temperature), the corresponding relationship between the flame propagation and pressure rise of gas/dust hybrid explosions was clarified. And the influence factor and inhibition mechanism on two-phase hybrid explosions were analyzed. Results indicate that flame propagation and pressure rise inside the closed vessel were corresponding. The flame front appeared an obviously thermal diffusion instability and became an irregular structure after adding mist. Meanwhile, the hybrid explosions could be effectively inhibited by the mist. The explosion intensity, flame propagation velocity and temperature were reduced obviously and the inhibition effect was enhanced with increasing mist concentration. The v_max and △P_max were decreased by 57.06% and 18.97% respectively. And the (dP/dt)_first and (dP/dt)_second were reduced by 55.91% and 61.11% respectively. In particular, the flame temperature was also decreased by 50.18%. Besides, the concentration and diameter of coal dust could also obviously affect the inhibition effect of hybrid explosions. Explosion parameter presented a trend of rising firstly and then decreasing as coal dust concentration increased. However, an increasing trend was presented with decreasing coal dust diameter. The inhibition of mist on gas/dust two-phase hybrid explosions was attributed to the combination of physical and chemical effects.