Research On The Countercurrent Migration Process Of Gas And Its Influencing Factors

After a coal and gas outburst accident occurs in a coal mine,there will be a large amount of high-concentration gas influx into the roadway.When the gas outburst strength and gas emission are too large,the gas will migrate in the roadway countercurrently,and the gas countercurrent is easy to form gas.The accumulation caused a gas explosion.In-depth study of the law of gas countercurrent migration after gas outburst and its influencing factors will help reduce the possibility of secondary damage such as explosion caused by gas countercurrent after gas outburst and reduce the risk of personnel,which is of great significance to coal mine safety production.Based on this,this paper adopts the methods of theoretical analysis,similar experiments,numerical simulation and field verification to study the process and law of the countercurrent migration of gas in the tunnel and the factors affecting this process.The definition,classification,characteristics and formation conditions of gas countercurrent are summarized by collecting a large amount of literature data.On the basis of previous studies,the continuity equation,energy equation and momentum equation are further optimized in accordance with the assumptions made in this paper.The model of gas migration law and influence range in the tunnel after gas outburst is derived.In order to verify the accuracy of the theoretical model,a similar test system was established.The gas migration process after the explosion of black powder was used to simulate the gas countercurrent migration process after the gas outburst,and the concentration change of gas migration and diffusion and the effect of wind speed and gas volume on the migration process were studied.The effect of concentration changes.Then,a geometric model was established on the basis of similar experiments,and the process of gas migration in the ventilation state after gas outburst was simulated using FLUENT software,and different wind speeds,different gas emission amounts,different gas emission positions and different roadway inclination angles were analyzed.The effect of the gas countercurrent and the concentration change in the process of gas migration,and the accuracy of the research on the concentration change law of gas migration and diffusion and the influence of wind speed and gas volume on the concentration change during the migration process are verified.Finally,taking the gas concentration change monitoring after blasting in a coal mine in Guizhou as a process example,collecting gas countercurrent accident cases for analysis,further verifying the reliability of the previous research results,and putting forward some measures to prevent gas countercurrent on this basis.It is intended to provide assistance for coal mine safety production.Through the research of this paper,the following results are obtained:(1)Theoretical derivation has obtained the gas migration law,gas concentration change and influence range in the tunnel after gas outburst.On the basis of previous studies,the continuity equation,energy equation and component mass equation suitable for this study are optimized.The derivation has to consider the diffusion and diffusion effects,and the gas concentration distribution law when only the turbulent diffusion effect is taken into account.The equations are established according to the formation conditions of the gas countercurrent,and the law of the influence range of the gas countercurrent is derived.(2)Establish a similar test system to monitor the changes in gas concentration after the outburst and verify the gas concentration distribution law deduced above.Draw the law of the concentration change when the gas migrates in the tunnel,and use the Origin to fit the monitored concentration data and the former gas migration and diffusion concentration law,and the fitting effect is good.Through control experiments,it is concluded that the wind speed and gas volume have an impact on gas countercurrent migration.The larger the gas volume,the higher the gas concentration and the slower the concentration decrease rate;the greater the wind speed,the greater the concentration change amplitude and the faster the decrease rate.,The lower the concentration at the same time.(3)On the basis of similar tests,the geometric model of the roadway is established at a ratio of 1:1,and the FLUENT software is used for numerical simulation.The simulation conditions of different wind speeds,gas emission,roadway inclination and gas emission position are set,and different layouts The measuring points and measuring lines monitor the concentration change law in the process of gas counter-flow under different conditions,and the simulation results are compared and analyzed,and the effect of the above four factors on the gas counter-flow of gas outburst is obtained.(4)Blasting operation was carried out on the working face of a coal mine in Guizhou,monitoring the change of gas concentration under different wind speeds behind the gun,analyzing the accident cases of Qunli Coal Mine,Xinxing Coal Mine and Daping Coal Mine,verifying the reliability of the previous results,and proposed Recommendations for prevention and control of gas countercurrent.