Numerical study on the ceiling gas temperature in a subway train with different fire locations

Ceiling gas temperature rise is an important evaluation indicator determining the level of risk in a subway tunnel fire. However, very little literature has been found that has addressed the emergency when a fired subway train with lateral multiple openings stops in the interval tunnel. Hence, a battery of full-scale numerical simulations were employed to address the impact of train fire location on the gas temperature beneath the train ceiling. Numerical results showed that the ceiling gas temperature rise is affected by the pressure difference on both sides of fire source and the backflow from the end wall, which depends on the heat release rate and the fire location. The ceiling gas temperature rise decays exponentially in the process of longitudinal spread, and it can be predicted by a dimensionless model with a sum of two exponential equations. Finally, based on a critical fire location ( $L_{\mathrm{c}\mathrm{r}}^{\ast }=0.667$), two exponential equations were developed to quantitatively express the influences of the fire size and the fire location on the maximum ceiling gas temperature. The research results can be utilized for providing an initial understanding of the smoke propagation in a subway train fire.