| Gas and coal dust explosion accident is one of the most frequent disasters in coal mine production activities in China.Due to the special space environment in the coal mine,coal dust and gas produced in the roadway are easy to coexist in the process of coal mine operation.Once the fire source is exploded,it will cause great casualties and national property losses.In order to effectively control such disasters and accidents,it is the basis of accident prevention to master the mechanism of explosion shock wave in the process of propagation.However,the propagation of blast wave is limited by many factors,such as the nature of combustibles and the propagation space of roadway network,which makes the propagation process of blast wave more complex and the damage is more serious.Therefore,it is necessary to improve the propagation theory of shock wave in the complex roadway network,study the time-space evolution law of shock wave in the semi closed space under the coupling effect of various factors,and control and reduce the damage caused by shock wave in the propagation process.Aiming to solve the above problems in this article,we used the theories of explosion mechanics,air propagation dynnamics and hydrodynamics,a large-scale complex pipe network experiment system is built by ourselves to study the propagation law of explosion overpressure and flame in the non-premixed combustion area of shock wave of gas and gas-coal dust mixed explosion,and then through the numerical simulation,the main conclusions are as follows:(1)Based on certain assumptions,the coupling relation between the overpressure,the propagation distance and the velocity of the explosion shock wave after attenuation in the pipe network is established.Through analysis,it is found that explosion overpressure is inversely proportional to the square root of propagation distance and section area,and is proportional to the square root of initial energy of explosion.The coupling relationship between the overpressure and flow velocity and the initial gas parameters is obtained when the forward and reverse shock waves meet in the complex region.(2)The experimental system of explosion in diagonal pipe network was set up.The influence of gas concentration of 8%,9.5%and 11%on the propagation characteristics of explosion shock wave was carried out.It was found that the evolution process of shock wave overpressure in the non-premixed combustion zone with time can be divided into three stages:the first stage,the overpressure rose steadily,while in the second stage,the overpressure suddenly jumped and reaching the peak rapidly.Finally,the third stage,the overpressure decays rapidly and tends to atmospheric pressure.The results show that the shock wave is affected by the gas concentration in the process of propagation,and the peak value of overpressure,the propagation speed of flame surface and the propagation distance of flame reach the maximum when it is close to 9.5%(3)Based on the experimental study of the propagation characteristics of the gas explosion shock wave in the semi-closed diagonal pipe network,it is found that when the shock wave propagates in the parallel branch,with the increase of the propagation distance of the shock wave,the peak value of the overpressure and the propagation speed of the flame surface gradually decrease,while the flame duration first increases and then decreases,and the overpressure on both sides of the parallel branch and the flame change trend are the same.Besides,the maximum distance of flame propagation and the coupling relationship between overpressure and propagation distance are established.In addition,in the diagonal branch,because of the superposition of the opposite shock wave,the high-pressure region will be formed,and the signal generated by the flame is very weak,the diagonal branch is not affected by the flame,so the temperature is low.(4)Through the experiment of gas and coal dust mixed explosion in semi-closed diagonal pipe network,the influence of coal dust deposition and particle size on the propagation characteristics of shock wave is analyzed.It is found that there are two wave peaks in the wave form of shock wave explosion overpressure and flame,the first peak is produced by gas explosion,but the duration is relatively short,and the second peak with greater overpressure and stronger light signal is produced by coal dust participating in explosion.Therefore,the overpressure will increase significantly,and the flame duration will be longer in gas-coal dust mixed explosion.In addition,with the increase of coal dust quality,the peak value of overpressure and flame propagation speed as well as the flame duration increase first and then decrease;with the increase of coal dust particle size range,the peak value of overpressure and flame propagation speed at each measuring point increase first and then decrease,but the change of flame duration is not significant.(5)Through the comparison of gas and gas-coal dust mixed explosion,under the same conditions,it is concluded that the attenuation degree of shock wave overpressure before entering the parallel branch is similar,but in the parallel branch,the attenuation degree of shock wave overpressure before T10 measuring point(the propagation distance is less than 17m)is faster,and after T10 measuring point,the attenuation degree is slower.The peak value of coal dust overpressure and flame propagation speed with a mass of 20g and a particle size range of 64um-106um are the largest,and the attenuation of shock wave overpressure in the pipe network is the slowest.(6)Through numerical simulation,the propagation process of gas explosion shock wave in the diagonal pipe network is studied.It is found that there are two high-pressure areas in the diagonal pipe network,respectively in the middle of the corner branch and the end of the parallel branch.In addition,the middle of the diagonal branch is not affected by the flame.On this basis,the propagation characteristics of gas explosion in the diagonal pipe network under the condition of multi factors are simulated.It is found that the change of gas concentration,pipe network geometry and ignition position will improve the explosion intensity and change the increase area of overpressure,and the range of flame spread will also increase.(7)By combining the gas premixed combustion model with the solid non-premixed combustion model,the numerical simulation results of the gas-coal dust mixed explosion propagation are calculated.It is found that the explosion overpressure and the flame change trend in the simulation process are basically consistent with the experimental process,which well verifies the shock wave propagation process in the experiment.Under the same experimental and numerical simulation conditions,through comparative study,it is found that the gas-coal dust mixture explosion will have higher overpressure and temperature,the pressure duration will greatly increase,and the flame propagation distance in the pipe network is longer.In addition,with the increase of coal dust mass,the maximum explosion overpressure increased first and then decreased;while with the increase of coal dust particle size,the maximum explosion overpressure decreased gradually.The above research results are of great scientific value and practical significance to the prevention,control and relief of gas and gas-coal dust mixed explosion disaster in the complex tunnel of coal mine.Figure[83]table[23]reference[147]... |
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