Study On Smoke Temperature And Flow Characteristics Of Underwater V-shaped Slope Tunnel Fire

The underwater tunnel has a considerable slope and special V-shaped slope,which make the smoke movement in the tunnel more complicated and cause the smoke control in the tunnel more difficult.The numerical simulation and theoretical analysis are used to study the temperature distribution and propagation characteristics of smoke in the underwater V-shaped slope tunnel.The key parameter of reasonable control of smoke in underwater V-shaped slope tunnel are obtained.The main research work and conclusions are as follows:(1)A correlation is presented for predicting the smoke temperature decay in the longitudinal direction of the V-shaped slope tunnel under natural ventilation conditions.Numerical simulations are conducted to study the temperature and velocity distribution in different slope tunnels.The results show that the temperature decay rate of the V-shaped slope tunnel is between the upstream and downstream of the single-slope tunnel,the dimensionless temperature rise of the V-shaped slope tunnel is proportional to 0.6 power of the dimensionless heat release rate and there is a certain nonlinear relationship with the tunnel slope.(2)The mechanism of the influence of the fire source location on the smoke competition is clarified under the coupling of the double slope of the V-shaped slope tunnel.Theoretical analysis and numerical simulation in a V-shaped slope tunnel are carried out to indicate that the tunnel port near the source side became the outlet of smoke and the other became the air inlet.Combined with the smoke propagation length and mass flow distribution,the smoke movement in the V-shaped tunnel can be divided into the double slope control zone,transition zone and single slope control zone.When the height of the fire source and the slope point is greater than 2.1m,the smoke movement is in the single slope control zone.The mass flow is the largest in the transition zone,and dimensionless mass flow is proportional to the power of 0.3 of the dimensionless heat release rate,which is proportional to the slope of the tunnel.(3)The formula for calculating the critical velocity of the V-shaped slope tunnel is developed.The numerical simulations are performed to analyze the smoke velocity and temperature distribution of different slope tunnels at different fire source locations,and determin the critical velocity of different slope tunnels.The dimensionless analysis shows that the dimensionless critical velocity of V-shaped slope tunnel is proportional to1/3 power of the dimensionless heat release rate,and is proportional to the distance of the fire source from the slope point of-0.021,which is proportional to the 0.21 power of the tunnel slope.