Study On Fire Smoke Characteristics Of Double Slope Coupled Tunnel

Slope is a common parameter in tunnel engineering,especially in mountains and underwater tunnels.The slope and slope shape changes in the tunnel seriously affect the fire smoke movement.Therefore,the characteristics of the tunnel fire smoke movement characteristics with large slope and complex slope shape change are worthy of attention.Among them,the flue gas temperature and the movement characteristics of the flue gas are scientific issues closely related to tunnel disaster prevention and rescue.In this paper,numerical simulation and theoretical analysis are used to study the fire smoke characteristics of a double-slope coupled tunnel.The main research work and results are as follows:(1)Established an empirical prediction model for the maximum temperature rise parameters of the tunnel roof under natural ventilation conditions.Through the numerical simulation of the temperature distribution on longitudinal centerline of the fire tunnel,it revealed that changes in the slope shape and fire source location of the tunnel have an effect on the fire plume and the maximum temperature of the tunnel roof.It is concluded that the dimensionless maximum temperature rise parameter increases with the increase of the dimensionless fire source position.And the dimensionless maximum temperature rise parameter is proportional to the 0.8th power of the dimensionless heat release rate,and first decreases and then increases with the increase of the tunnel slope.(2)Clarified the influence of tunnel slope and fire location change on the spread of smoke in the tunnel.This paper analyzes the fire smoke force in the V-shaped tunnel,studies the influence of the tunnel slope and fire source location changes on the fire wind pressure,determines the basic characteristics of the smoke movement,uses numerical simulation to verify the smoke movement characteristics.The results show that when the fire smoke spreads to the left tunnel of the slope point,the smoke layer upstream of the fire source is parallel to the tunnel roof;when the smoke cannot spread to the slope point,the smoke upstream of the fire source is parallel to the horizontal plane.The back-layering length increases with the increase of tunnel slope,when the tunnel slope is greater than7%,the back-layering length is basically not affected by the location of the fire source.(3)Proposed a dimensionless parameter Ri to measure whether the flue gas can reach the point of slope change after the smoke spreads stably.Numerical simulation is used to study the influence of double-slope coupled tunnel slope length change on smoke temperature,smoke spread and the back-layering length.The results show that increasing the slope of the double-slope coupled tunnel or the length of the side slope of the fire source is helpful to reduce the length of the back-layering length;when the dimensionless parameter Ri>10,the back-layering cannot reach the tunnel slope point when it flows backward,and when Ri<10,the back-layering can reach the slope point.During the stable period of smoke movement,the disappearance time of back-layering on the left side of the slope change gradually decreases with the increase of slope,and gradually increases with the increase of slope length.