Influences of nonmetallic powders on premixed methane-air flame propagation in square tube

Two common powders in coal mine laneways, coal dust and rock dust, were spread evenly at the experimental tube bottoms, respectively. Subtle thermocouples and flame photoelectric sensors were adopted to obtain the premixed methane-air flame parameters including transient temperature, flame front position and flame propagating velocity in the tube. And the influencing mechanisms of the two powers on flame propagation were preliminarily analyzed. The experimental results show that the coal dust can accelerate the flame propagation in the tube, and the rock dust can suppress the flame propagation, but the mechanisms of acceleration or suppression are essentially different. When the coal dust is spread in the tube, the flame transient temperature curves at test points take on obvious twin-peak structural waves and the reaction zones widen. It reveals that the methane-coal dust composite flame is formed between the reactive coal dust and the methane. When the rock dust is spread in the tube, the transient temperatures at test points all decrease, and the temperature half-peak widths narrow. It can explain that spreading rock powder in coal mine laneways can prevent or mitigate the methane-coal dust explosion hazards to a certain extent.