Numerical Simulation Study On Emergency Ventilation System In Subway Stations

Convenient and fast subway system with large capability is the important part of amodern city. However, the complicated underground structure and the enclosed areadiscount its advantages. As a distributing center, the subway station faces hardship ofevacuation once emergencies occurred, which give disastrous consequence to life andproperty. All the incidents happened home and abroad make people lay more stress onthe environmental control and fire protection system.Low costs, quick and detailed information are the characteristics of numericalsimulation. Selecting the suitable turbulence model, good grid generation and rationalconvergence index are critical to the preciseness of the numerical calculation. ReliableCFD results can play a good role in the project application. However, because of thecomplication of this issue and the limitation of the computational fluid dynamics,some hypotheses are inevitable during computing. So we have to validate it beforeapplying the information to the full-scale subway station. For this case-fire in subwaystation, measuring on site is almost impossible, then, the reduced-scale model is theremedy. Scale model experiment is used to compare with the computational results.Several investigations on fire incidents have shown that the major reason for deathis the poisonous gas and hot smoke, which cripples the evacuation abilities ofpassengers. Different from other study on this issue, we solve the concentration fieldof carbon monoxide, which is more poisonous in combustion products of fire.Combining it with the velocity and temperature as the index to analysis the efficiencyof different smoke control schemes and evaluate the performance of safety system.This thesis simulates two typical subway stations, one is two-floor island platform andthe other is one-layer side platform, where one of the train carriages is on fire. Fire isrepresented as a source of heat and mass. Special emphasis is placed on the evolutionof smoke propagation under smoke control, to find out the effective smoke controlscheme, which either confined the smoke to a small region or evacuate it from thestation, so that passengers can evacuate the station smoothly. The detailed informationcan be used to aid design of the reversible ventilation and emergency planning.