Effects of altitude on smoke movement velocity and longitudinal temperature distribution in tunnel fires

Abstract

The objective of this present study is to explore the effect of altitude on smoke movement velocity and longitudinal temperature distribution in tunnel fires. A series of tunnel fire simulation experiments with different HRRs (heat release rate) and altitudes were carried out using Fire Dynamics Simulator (FDS). The results show that the velocity of smoke movement is proportional to the altitude and the HRR of afire, and due to heat loss during smoke movement, the velocity decays exponentially along the longitudinal direction of the tunnel. Based on dimensionless analysis and experimental data, an empirical formula is proposed to predict the distribution law of smoke velocity in tunnel fires. The motion velocity of smoke increases with altitude, and the thermal convection between smoke and the tunnel wall is enhanced, thus increasing the heat loss of smoke, so the longitudinal temperature attenuation is faster at higher altitudes, and dimensionless temperature is distributed as the sum of two exponential functions.