Effects Of Longitudinal Ventilation On Temperature Distribution Characteristics Of Fire Smoke In Tunnels

As parts of transportation infrastructures, tunnels play vital roles in traffic. However, the challenges along with the convenience posed by the tunnel have been emerged, especially in fire accidents. Tunnel fire would cause disastrous consequences if it is not well controlled. The main fatal factor that causes casualties in fires is the toxic smoke produced by the combustion, that’s the reason the smoke control in tunnels is an important issue in the area of tunnel fire safety. Longitudinal ventilation is one of most common ventilation used in tunnels, researchers of abroad and home have taken into consideration that, but most of the researchers focus on few key engineering parameters, e.g. the critical velocity.Therefore, CFD numerical simulation, theoretical analysis and experimental comparisons are conducted on effects of longitudinal ventilation on temperature distribution characteristics of fire smoke in tunnels, the main work accomplished in this dissertation as follows:(1)A simple correlation of the critical velocity of longitudinal ventilation is theoretically presented on the basis of Richardson number. The CFD software, fire dynamics simulator (FDS) developed by NIST, is used for simulation in this dissertation with a recent version5.5.3, and the rationality and accuracy of the numerical model are analytical validation. The critical velocities of tunnel models adopted in the dissertation are comparative analysis with results obtaining from the simulation, experiment and prediction models.(2)The analysis of the maximum smoke temperature beneath the ceiling under longitudinal ventilation conditions is carried out. Furthermore, the evolved variation of the maximum temperature with longitudinal ventilation is obtained. The position of the maximum temperature is also discussed at the same condition.(3)The correlation of temperature distribution beneath the ceiling along tunnels is derived. In addition, the data acquired from the simulation and experiment of previous study is employed to study the effect of longitudinal ventilation on temperature distribution along tunnels, and the correlation of temperature distribution derived in this dissertation is adjusted further. At the same time, the quantitative analysis of the impact of longitudinal ventilation on temperature stratification in tunnels is carried out, and the smoke stratification regions defined by the Froude number (Fr) are determined.The accomplishments of this dissertation could provide technical references for longitudinal smoke control in tunnel fires.