Influence of train speed and blockage ratio on the smoke characteristics in a subway tunnel

This paper focuses on the smoke characteristics in a subway tunnel when a subway train travels between two consecutive stations at different speeds and at different tunnel blockage ratios. The piston effect caused by the train movement significantly influences the airflow in the tunnel and at the stations. To simulate the blockage effect of a vehicle and to accurately describe the smoke flow characteristics, a 3-D full-scale computational model of a subway train, two stations and a tunnel was established. To study the influence of the blockage ratio on smoke flow in the tunnel, five different cross-sectional areas were modeled. The dynamic mesh technique was used to simulate train movement in the tunnel. The results show that the maximum temperature occurs at the same position for different blockage ratios when the train runs at the same speed. The maximum temperatures in cases 2-5 decrease by 21-55% relative to the maximum temperature in case 1 at 30 s and by 11-37% relative to the maximum temperature in case 1 at 270 s. For different train speeds, the maximum temperature occurs at different positions, and the maximum temperature of all the cases is 6 to 10 times higher than that of case 6 at 30 s. The influence of train speed on the smoke movement distance is much smaller than the influence of the blockage ratio.