The Study On Smoke Spread And Main Influencing Factors In Typical Mine Tunnel Exogenous Fire

Mine fire is one of the five major hazards in mine.There are lots of dangerous combustibles in the mine and tunnel space is narrow and closed,so fire burst rate is high and the difficulty of fighting mine fire is much larger than that of the ground fire.In mine fire,the fire spread rapidly,its mechanism is complicated and changeable,and the scope of the hazard is wide.It will not only burn up a large number of production facilities,equipment and coal resources,but also pollute the working area of the workers,and threaten the life and health of the downhole personnel.In China,10%to 15%coal mine fires are exogenous fire,and the proportion of major malignant fire hazards accounted for more than 90%.65%of the total number of casualties in coal mines are caused by exogenous fires.Exogenous fire develops fast due to the large number of ignition sources and abundant supply of air flow in exogenous fire,so the property loss and casualties caused by it are quite serious.Therefore,there are a lot of benefits to study on the law of fire smoke spread and the main influencing factors in mine exogenous fires.It can not only help people to understand the fire development,the law of fire smoke spread,the destruction effect and influence scope of fire under different conditions in advance,but also it is beneficial for improving the mine fire management and making effective prevention and rescue decision and improving emergency rescue technology in the fire.This paper mainly adopts the method of numerical simulation.Through the simulation of mine tunnel fire,this paper summarizes the law of fire smoke spread and the influence on fire hazard and the gas migration of three main factors(the wind speed,the scale of the fire and the slope of the tunnel).The following is the main content and conclusions:(1)A fire model of the inlet tunnel,working face and return airflow tunnel has been established by FDS,and the t~2 fire source model has been selected.in the model.The total simulation time is 800s,and the maximum heat release rate is10MW at 575s.The dynamic spread diagram of smoke and the data of slicing and measuring points are obtained.At last,the simulation data are analyzed from three aspects of temperature,visibility and CO volume fraction.It is concluded that in tunnel fires,The further away from the fire,the smaller effect of the fire.The downwind area under fire source is mainly affected,the smoke spreads along the wind direction,and gathers in the upper layer of tunnel,then gradually drops to the lower layer of tunnel,the upper layer of the tunnel is more polluted than the lower layer,so the people should away from the fire area quickly and escape along the return airflow tunnel,keeping the bending posture to avoid breathing too much smoke.In the development of mine fire,the greatest threat to personnel escape is the rapidly decline in visibility,due to black smoke.(2)A single tunnel fire model has been established to study the influence of wind speed,fire source scale and tunnel inclination on the smoke spread in tunnel.It is concluded that properly increasing the wind speed of the tunnel can effectively prevent smoke flowing back and make the upwind area of the fire source become a safe area which is not affected by fire and smoke.With the increase of the fire source scale,the smoke concentration gets bigger,the smoke spread and smoke layer falling become faster,the area affected by the fire is bigger,the degree of hazard is more serious,and personnel escaping is more dangerous.Under the condition of no mechanical air flow in the tunnel,the smoke spread is affected by the tunnel inclination,so the affected areas in the tunnel are different.The smoke movement in the inclined tunnel is affected by the fire pressure and the height of tunnel.In the horizontal tunnel,the upwind area and the downwind area of the fire source are affected by the smoke.