| Recent years, with the development of traffic, the tunnel fire accidents occur frequently. And due to the fire often can’t be controlled effectively, make a great loss of person and property safety in tunnel. The statistics show that the main factor of causing casualties is the poisonous gas that incomplete combustion produces in the fire. Therefore, this paper based on the fully research of the advantages and disadvantages of the tunnel ventilation system at home and abroad, according to the characteristics of the semi-transverse ventilation system in tunnel fire, researched the smoke properties of tunnel fire under the semi-transverse ventilation system by the method of combining theoretical analysis and numerical simulation.Semi-transverse ventilation system exhaust rate is an important parameter, so this paper study the effect of exhaust rate to the highest temperature distribution of fire smoke in tunnel by the method of combining theoretical analysis and numerical simulation. Results show that when the exhaust fan tunnel is shut up, the vault temperature distribution can be divided into two areas: the high temperature area near the fire and the smoke temperature slow attenuation and one-dimensional free spreading area which is far away from fire source. Combined with previous research analysis and simulation results, no smoke tunnel vault temperature attenuation formula was gotten. When the smoke exhaust rate is small the fire smoke temperature distribution is continuous, with the spreading distance increases the smoke temperature decreases. Smoke spread distance along with the smoke exhaust rate can be divided into three stages: the stage of heat removal, flue gas reflux suppression and exhaust smoke completely. According to the simulation results and the dimensionless analysis, a model which is related the source of power, the highest flue gas temperature of smoke exhaust rate was proposed to predict the smoke highest temperature in the personnel evacuation area behind the exhaust port.Due to the randomness of tunnel fire, the research of the smoke temperature distribution under the different transverse distribution of fire is important. Mainly analyze the variation of the highest temperature of the tunnel vault caused by the effect of limitation of the tunnel wall under different fire location. At the same time, this article analyzes the influence of smoke port and the fire source transverse layout to the smoke exhaust effect, the smoke flue gas concentration distribution was studied.Due to the tunnel usually has a certain slope, the smoke spreading regularity in the different direction is different. To make smoke exhaust system can both make full use of smoke vent and reduce the energy consumption of the fan when the fire broke out, this paper did a large number of numerical simulation of different slope tunnel fire to get a reasonable smoke exhaust strategy. The flue gas flow distance and fan heat extraction efficiency were both taken into account for the choice of exhaust strategy. Results show that when the tunnel slope is increased to 1.5%, unilateral smoke strategy can be used. Due to the continuous enhancement of stack effect, when tunnel slope increased to 3%, the longitudinal ventilation with semi-transverse ventilation should be adopted. The above research results can give a certain guidance for fire rescue plans of tunnel fire and ventilation and smoke exhaust design. |
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