Study Of The Influence Of Natural Ventilation Shaft Structure On Smoke-ejection Effect Of Fire In Subway Tunnel

Usually, conventional mechanical smoke exhaust mode was adopted for smokeejection to dispersing people when there is fire emergence in subway tunnel. The energyconsumption of ventilation system is a very important part of overall consumption. Thus,if natural ventilation can be adopted, much money, including operation costs in nights,construction costs for fans and ventilation pipes and accidental fan costs, would besaved. As a result, study on the natural ventilation of subway tunnel and its effect isattracting more and more attentions.This paper studys of the Influence of NaturalVentilation Shaft Structure on Smoke-ejection Effect of Fire in Subway tunnel.Based on Froude similarity criterion, a model that is14times smaller than theactual tunnel was made to simulate the real conditions. Different shaft structures weresimulated to study on the temperature and smoke distribution. By the simulation result:Ceiling area above the fire source between two ventilation shaft of the smoketemperature is high, up to180℃and most smoke could be ejected from the two shafts.Then, the temperature decreased evidently. The deepness of the shafts had greatinfluence on the temperature and smoke distribution; whereas the open form of themhad relatively less effect.Besides,numerical simulation software FDS was also used to simulate the realconditions. simulation result of experiment was very similar to that of the softwaresimulation, suggesting that the FDS software could be used in fire simulation properly.Lastly, by the numerical simulation of actual-size tunnel natural ventilation, threecontrol parameters were gotten: smoke temperature at the height if human eyes shouldbe less than66℃; CO thickness at the same height should be less than250ppm; visibility at this height should be more than8m. Based on these three variables, smokedistribution and human safety was analyzed. The final conclusion is that the deeper ofthe shafts, the better of its effects and that vertical shafts had a better effect than shaftswith other angles.