Experimental Study On Nitrogen Curtain Preventing The Gas Explosion

The dominant position of coal in energy structure of China is difficult to change in a short period of time.In the production process of coal mines,there are still potential dangers,and the security situation is still not optimistic.The content of gas in the coal mine accumulates to the flammable limit,and the explosion occurs quickly under the action of ignition source.Due to the narrow space of the roadway,methane explosion flames,shock waves and harmful gases will spread rapidly along the roadway,which will often result in group deaths and group injuries.After the accident,how to ensure the safety of underground personnel and facilities has always been the focus of domestic and foreign scholars.This paper mainly studies the blocking and isolating explosion effect of nitrogen curtain.After the methane explosion in the pipeline,the active blocking and isolating explosive device is activated,nitrogen sprays out and a nitrogen curtain is formed to block and isolate the explosion flame.In the study on the influence of jet pressure on the blocking and isolating explosion effect of nitrogen curtain,it is found that when the nitrogen jet pressure is lower than the critical blocking and isolating explosion pressure of the nitrogen curtain,the methane concentration in the left side pipe area of the nozzle is not diluted below the methane flammability limit,and the explosion flame can always propagate to the left end of the pipeline,eventually failing to block and isolate the explosion.After the nitrogen injection pressure reaches the critical blocking and isolating explosion pressure of the nitrogen curtain,the methane concentration in the left side pipeline of the nozzle is diluted below the methane flammability limit.Due to the insufficient methane supply at the flame front,the explosion flame passing through the nozzle can be quickly extinguished by the nitrogen curtain.The nitrogen curtain successfully blocks and isolates the explosion.The nitrogen pressure can be a decisive role in the blocking and isolating of explosion.In the study of the influence of the detection position on the blocking and isolating explosion effect of nitrogen curtain,it is found that at a lower nitrogen pressure of 0.2 MPa,the detection position has a significant effect on the blocking and isolating.As the distance between the detection point and the initiation point increases,the jet time of nitrogen decreases,and the amount of nitrogen is reduced,nitrogen concentration in the nitrogen curtain decreases,and the nitrogen curtain changes from unstable blocking and isolating to failure of blocking and isolating.In study of the influence of nozzle arrangement on the blocking and isolating explosion effect of nitrogen screen,it is found that the nozzle arrangement determines the spatial distribution of nitrogen.The nitrogen is more concentrated in the location of the blocking and isolating explosion and more uniform distribution on the cross section of the pipeline,the stronger the blocking and isolating explosion ability of the nitrogen curtain.The overpressure and flame velocity history of explosion has two peak values.The first peak value appears when the vent is broken in explosion.The second peak value appears when the explosion flame arrives at the region of nitrogen curtain.The second peak value of overpressure and flame velocity are consistent to the ability of blocking and isolating explosion.The stronger the blocking and isolating explosion ability is,the smaller the second peak value.Under the same nitrogen injection pressure,nitrogen curtain shows different ability of blocking and isolating explosive due to different jet moments,nozzle arrangements and venting area.In this paper,The size order of degree of influence of jet pressure,jet moments,nozzle arrangements and venting area to block and isolate successfully explosion or not is jet pressure>venting area>nozzle arrangement> jet moment.