Abstract: A rotating friction test device was set up based on the GB13813 to investigate the ignition regularities of methane， air and coal dust. The observation via high speed camera and infrared thermography shows that the methane/air mixture is ignited by titanium particle spark during the friction process of A3 steel and titanium bar. A set of experiments， using lignite， bituminous and anthracite with 3 kinds of particle diameters， were conducted to test the influence of coal dust on the ignition of methane/air mixture. It is found that the ignition delay time gets longer when introducing coal dust and smaller particle can cause longer delay time. The ignition delay time for the three kinds of coal from short to long is bituminous， anthracite and lignite， which accords with the water content in the sample. The delay time has nothing to do with the volatile of the coal.

Key words: methane, coal dust, rotating friction spark, particle diameter, ignition delay time