Numerical Simulation Study On Fire Smoke Spread In Double-deck Bus

With the increasing number of double-deck bus, double-deck bus fire accidents happened all over the country attract social concern on double-deck bus fire. Because of large passengers capacity,strong human mobility, confined space and complex traffic environment, when the fire accidents happened, double-deck bus has the characteristics of rapid combustion, large harmfulness, easy to flash over,difficult to evacuate, hard to rescue,lead to large seismic casualty,huge property damage and terrible social influence.Therefore, by checking large number of documents, analyzes the research theory and research progress of double-deck bus fire accidents at home and abroad, determines the research content and methods.Because of the shortage research of double-deck bus fire full-scale test and numerical simulation at home and abroad, due to constraints, hard to have full-scale test, so this paper simulate and analyze the fire spread of double-deck bus by fire simulation software FDS. This paper has a systematic research on the fire spread effect from fire source position and the doors and windows open or close of double-deck bus.This paper simulates 24 working conditions of different fire source position and condition of doors and windows of double-deck bus,finds that when the doors and windows keep opened,fire source has biggest heat release rate in the forward and backward of first layer,which is the same as second layer.The temperature will be 60℃ near the fire area firstly,visibility will down to 10m firstly,the concentration of CO and CO2 will be 0.05% and 3% firstly. When the fire happened in the second layer,there is no change of the temperature,visibility and concentration of CO and CO2 in the first layer,but the fire area will be 0.1%,when the fire happened in the forward and backward of second layer.When the fire happened in the middle part,the forward and backward will be 0.1% firstly,the concentration is lowest in stable condition,the concentration increases in the direction to forward and backward. When the fire stays fixed position:doors and windows are closed,heat release rate decrease rapidly in 150s,as long as the doors and windows are opened in the first layer,will the first layer fully buming,not affected by the ventilation in the second layer.The temperature will be 60℃ in 50s of different working conditions.The time that the visibility appeal to zero has no relationship with ventilation in the second layer,but affected by the working conditions in the first layer. When the bus keep closed,the concentration of CO will be 0.05% and 0.1% firstly,but can not be 0.2%.And the concentration of CO2 will be 0.3% firstly,the time that the concentration up to 3% increases as the distance to fire increases.The simulated result and analysis result can provide help to fire protection design of double-deck bus, passenger safety evacuation and fire cause investigation.