Simulation Experiment Study On Gas Explosion Propagation In Interconnected Space Of Coal Mine

Gas explosion accounts for the highest proportion in major accidents in coal mines,which is highly destructive and seriously threatens the safety production of coal mining enterprises.In the process of underground mining,a large volume of goaf will be produced,and connected with the narrow and long roadway around it,forming an interconnected space similar to "vessel-duct".After the gas explosion in the goaf,the shock wave and flame can easily enter into the connected roadway to spread,resulting in the expansion of the disaster scope and the aggravation of the loss of personnel and property.The complexity of interconnected space will seriously affect the propagation process of gas explosion,and increase the difficulty of coal mine gas explosion accident prevention and control.Therefore,in this paper,laboratory experiments,theoretical analysis and numerical simulation are used to study the overpressure and flame propagation law of gas explosion in the connected space under different conditions,and reveal the flame transition process and accelerating propagation mechanism of gas explosion in the interconnected space;garry out gas explosion experiments under different concentration gradient and study the influence of concentration gradient on the propagation process of gas explosion in the interconnected space;analyze the phenomena of overpressure oscillation,flame backflow and secondary pressure-rise of gas explosion in connected space are analyzed,and reveal the generation process of secondary gas explosion in interconnected space.The main conclusions are as follows:The simulated gas explosion experimental system of “goaf-roadway”interconnected space was established.The effects of concentration,obstruction rate and end open/closed end on overpressure and flame propagation in the interconnected space were tested and analyzed.The results show: the peak value of overpressure,flame signal intensity and flame propagation velocity of gas explosion in the interconnected space near the sudden contraction of cross section are smaller than those of other measuring points;under the condition of obstacles,the peak overpressure and flame propagation velocity of gas explosion in the connected space increase significantly compared with those without obstacles,and the greater the blockage rate of obstacles,the greater the increase range;under the condition of closed end,the overpressure peak value of gas explosion in the connected space increases greatly under the reflection and superposition of shock wave,but the flame propagation velocity decreases obviously.The flame propagation process,gas flow process and overpressure propagation process of gas explosion in connected space are studied by numerical simulation,and the accelerating propagation mechanism of gas explosion flame in connected space is revealed.The results show that: when the gas explosion flame in the connected space enters into the duct through the cross-section sudden contraction structure,it will form the contraction flow beam,which will lead to the increase of gas velocity and the generation of velocity gradient,and then induce the generation of turbulence pulsation,promote the transition from laminar flame to turbulent flame,and finally lead to the acceleration of gas explosion flame propagation in the interconnected space.Gas explosion experiments under different concentration gradient were carried out to study the influence of concentration gradient on the temporal and spatial variation of overpressure and flame of gas explosion in interconnected space.The results show that: the change process of gas explosion overpressure with time in the explosion vessel of interconnected space is not only affected by its own internal gas concentration,but also related to the gas concentration in the propagation duct;when the gas concentration in the explosion vessel is the same,there is an optimal concentration gradient in the interconnected space,which makes the flame spread fastest and the gas explosion power maximum.The phenomena of overpressure oscillation,backflow flame and secondary pressure rise in gas explosion in interconnected space were aanlyzed,and the generation process of gas secondary explosion in the interconnected space was revealed.The results show: the overpressure oscillation of gas explosion in the explosion vessel of interconnected space belongs to Helmholtz oscillation,and its oscillation frequency is related to the volume of the explosion veasel,the gas concentration in the explosion vessel,the length and cross-sectional area of the duct;the reverse pressure difference between the gas combustion area and the explosion relief area in the interconnected space is the fundamental cause of flame backflow;the secondary pressure rise intensity of gas explosion in the propagation duct of interconnected space decreases gradually with the increase of propagation distance;the secondary gas explosion in the interconnected space is caused by the unstable combustion caused by the return of high temperature flue gas and the residual unburned gas in the low pressure area.The research results of this paper have important theoretical significance and practical value for further improving and enriching the transmission dynamics theory of gas explosion in complex space underground coal mine and improving the prevention and control level of gas explosion disaster in coal mine.There are 114 pictures,12 tables and 220 references in this paper.