Experimental Study Of The Effect Of Obstruction On Methane-Coal Dust Explosion Intensity

More and more explosions of gas and coal-dust occurred frenquently in recent years. There are lots of obstructions such as apparatus and machines etc. almost in all explosions locales. The obstructions make explosion more powerful and loss greater. In order to prevent the explosions of coal-dust and combustible gas, the explosion power and characteristics of the mixtures must be confirmed firstly. But the studies on the mixtures explosion especially the explosive effect of obstruction on methane-coal dust mixtures are few. The explosion characteristics of methane-coal-dust aiming at having obstructions and having no obstructions were studied experimentally in this paper. The main work and conclusions are as follows:(1) The experimental system of obstruction twitched coal-dust-gas explosion equipment was set up according to the standard. The equipment could control coal-dust, methane and obstruction parameters, explosion pressure, the maximum pressure rising rate and explosion time etc.(2)The obstructions accelerated remarkabaly the explosion of coal-dust-methane. Comparing with no obstruction, the explosion time decreased from 70ms to 20ms; accelerating mechanism of pressure wave in pipeline is that the positive feedback between overfall obstruction inducing and inflammation.(3) The effects of structure, position, amount, block-rate of obstruction on the maximum explosion pressure, the maximum pressure rising rate and explosion time in the pipeline were studied. In six different shapes obstructions, the square has the most ability to accelerate and the rotundity has the least ability and the triangle has the middle ability to accelerate. When the distance of obstructions is approaching to the diameter of the pipeline, the pressure rising rate reached the maximum. When the amount of obstructions is 15, the pressure and the pressure rising rate both reached the maximum, respectively. When the block-rate of obstruction reach 0.5, the pressure and the pressure rising rate also both reached the maximum, respectively.(4) The effects of composion of methane and coal-dust on explosion were studied. With coal-dust particular size decreasing, the maximum explosion pressure and maximum pressure rising rate increased, and; with coal dust concentration increasing, the maximum explosion pressure and maximumrate pressure rising rate increased first then decreased, and when the concentration was 500g/m~3, the both reached the maximum; with the methane concentration increasing, the maximum explosion pressure and maximum pressure rising rate increased first then decreased, and when the methane concentration was 6-7%, the maximum explosion pressure and maximum pressure rising rate reached the maximum.The main ideas are presented in this paper are as follows:(1) The paper has studied the explosion characteristics of methane-coal dust mixtures with obstructions in the pipeline, and the explosion characteristics affected by shapes, size and amount etc. of obstruction has been gotten. In six different shapes obstructions, the square has the most ability to accelerate and the rotundity has the least ability and the triangle has the middle ability to accelerate. When the distance of obstructions is approaching to the diameter of the pipeline, the pressure rising rate reached the maximum. When the amount of obstructions is 15, the pressure and the pressure rising rate both reached the maximum, respectively. When the block-rate of obstruction reach 0.5, the pressure and the pressure rising rate also both reached the maximum, respectively.(2) The results indicated the smaller coal-dust particular was, the bigger the explosion power, and when the concentrations of coal-dust and methane were 500g/m~3 and 6-7%, respectively, the explosion power was the most.