Study On Synergistic Inhibition Of Nitrogen Curtain And Combined Porous Media On Gas Explosion

Gas explosion,as one of the main disasters affecting coal mine safety in China,causes serious harm to underground staff.In the process of coal mining,it is inevitable to produce gas.The accumulated gas cannot be effectively discharged.When the ignition source is encountered,which leads to serious accidents and causes personnel and property losses.So it is particularly important to explore effective methods to suppress gas explosion.In this paper,an experimental study on the synergistic suppression of gas explosion by nitrogen curtain and combined porous media was carried out in a visual explosion pipeline.The characteristic parameters such as flame structure,flame propagation velocity and explosion overpressure are analyzed emphatically.The law of the synergistic suppression of gas explosion by nitrogen curtain and combined porous media is obtained.This study has better theoretical significance for the prevention of underground gas explosion accidents in coal mines.Firstly,the whole process of gas explosion suppression by combined porous media is studied by self-built experimental platform.All kinds of characteristic parameters before and after quenching explosive flame in combined porous media are analyzed.The result shows that the peak flame propagation velocity,explosion overpressure and pressure rise rate of copper foam are lower than those of iron and nickel foam only.The intensity of reburning flame is weakened after quenching the explosion flame.It shows that reasonable combination of porous media with different characteristics can reduce explosion risk and improve flame quenching performance of porous media.Secondly,a nitrogen curtain generator is added to the visualization pipeline system to study the influence of nitrogen curtain position on the suppression of gas explosion by single porous media.The results show that the nitrogen curtain has a turbulent acceleration effect on the flame,which promotes the flame to accelerate forward in a broken shape,but the broken flame is more easily quenched.In addition,the nitrogen curtain can eliminate the reburning phenomenon after quenching the explosive flame.The formation of the nitrogen curtain leads to a bimodal pressure curve,and the peak value depends on the nitrogen curtain position and the pore density of porous media.The closer the nitrogen curtain position to the ignition end and the larger the pore density of the porous medium,the larger the second overpressure peak.Finally,on the basis of chapters three and four,the effect of nitrogen curtain and combined porous media on the suppression of gas explosion is studied.The results show that reasonably changing the combined porous media can improve the effect of suppressing gas explosion together with the nitrogen curtain.In the optimal nitrogen curtain position,the combination of nickel foam in the first layer and iron copper foam in the second layer can reduce the strength of the flame to reach the porous medium and reduce the overpressure peak.At the same time,it can prevent the quenching failure caused by the deformation of copper foam with low stiffness.The mechanism of synergistic suppression of gas explosion by nitrogen curtain and combined porous media is obtained:nitrogen curtain makes the flame structure broken,and dilutes the combustible concentration at the upstream end of the porous medium.Thereby reducing the flame propagation velocity.Moreover,many nitrogen molecules remain in the pore structure of porous media.The probability of destruction caused by the collision of pore structure or three-body collision with nitrogen molecules by high-energy free radicals involved in combustion reaction is greatly increased.The combustion reaction can not continue in the porous medium,and the porous medium is easier to quench the explosive flame.