Experimental Study of the Influence of an Asymmetric Tunnel Structure on the Maximum Ceiling Temperature in a V-Shaped Tunnel Fire

The smoke diffusion characteristics in an asymmetric V-shaped tunnel located at the slope change point were studied by experiments in a 1/20 small-scale tunnel. The influences of the slope composition of the V-shaped tunnel and fire heat release rate (fire HRR) on the fire-induced airflow velocity in the tunnel and maximum ceiling temperature rise were the focuses. The results show that due to the height difference between the two ports of the asymmetric tunnel, the resulting thermal pressure difference between the two sides of the tunnel drives the smoke to flow toward the large slope side and the inlet-induced airflow velocity increases with the increases in the slope difference and the HRR. The dimensionless inlet-induced airflow velocity v* is proportional to φ10.525H*0.634φ1−0.223Q*0.288. The maximum ceiling temperature rise increases with the increase in the HRR and decreases with the slope differences between the two side tunnels. An empirical model of the dimensionless induced airflow speed and the maximum temperature rise was proposed.