CFD Analysis of Smoke Extraction in High-Altitude Highway Tunnel Fires with Vertical Shafts

This research aimed to study the impact of different altitudes on the flue gas temperature and thermal stratification in the highway tunnel with a vertical shaft, by establishing a full-sized tunnel model using the numerical simulation software Fire Dynamics Simulator (FDS). Simulation experimental results were analyzed and it was found: first, with the same heat release power of fire source, the vertical, transverse and roof temperatures of both fire source and non-fire source sections in the tunnel all increased to a certain extent along with the increase of altitude; second, the vertical, transverse and roof temperatures of the tunnel all increased with the increased heat release rate of fire source at the same altitude, and the temperature of the fire source section was higher than that of the non-fire source section as a whole; third, the average temperature and stratification intensity of vertical flue gas in both sections showed an increasing trend with the increase of altitude, indicating that the intensity of flue gas thermal stratification at high altitude was greater than that at low altitude, because a large amount of flue gas accumulated in the upper tunnel and led to the increase of the roof flue gas temperature at high altitude.