Experimental Study On Gas Explosion Suppressed By Diluent And Ultra-fine Water Mist

Gas explosion is a more destructive accident in coal mine.Improving gas extraction rate is the main method to control gas currently.However,most of the gas concentration in the drainage pipes is within the explosion limit range,which is a potential danger for gas transportation in pipes.Therefore,a self-designed semi-closed transparent experimental system was used in this paper to carry out a series of gas explosion inhibition researches in pipeline with CO₂ and ultra-fine water mist,respectively and jointly.The gas explosion suppression rules and mechanism of CO₂ and ultra-dine water mist were also analyzed.The research results have a significant effect and meaningful guidance on gas transportation and explosion suppression.First of all,the suppression rules of gas explosion with CO₂ and ultra-fine water mist respectively were studied when methane volume fraction is 9.5%.By analyzing the flame structure,flame propagation velocity,explosion overpressure,average pressure rise rate,etc.it can be seen that: the effect of gas explosion suppression was not significant when CO₂ volume fraction was less than 6%.When CO₂ volume fraction was more than 6%,the suppression effect was significant.Furthermore,the rangeability of flame-front position,flame propagation velocity and explosion overpressure were slight with the increase of ultra-fine water mist amount when the volume of ultra-fine water mist reached to a certain value.And the obvious "marginal effect" appeared.Then the suppression rules of gas explosion with CO₂ and ultra-fine water mist jointly were studied when methane volume fraction is 9.5%.The results show that: the typical flame-front tulip-shaped flame appeared.The instantaneous and average velocity of flame propagation decreased considerably.The explosion overpressure and average pressure rise rate reduced considerably,too.When adding 6% CO₂ and 2.8ml ultra-fine water mist respectively,the decrement of explosion overpressure peak value was 5.7 kPa and 9.75 kPa separately,and the total decrement was 15.45 kPa.When adding 6% CO₂ and 2.8 ml ultra-fine water mist together,the decrement of explosion overpressure peak value was 18.16 kPa.All of the results above indicate that CO₂ andultra-fine water mist have a great synergistic effect on methane explosion.Finally,the effects on flame stability with CO₂,ultra-fine water mist and the synergistic effect of them were analyzed.It was considered that the large amount of ultra-fine water mist can improve flame instability,while CO₂ can improve flame stability.They work together and have a great synergistic effect on methane explosion.