Study on Asymmetric Flow in Inclined Tunnel Fire Caused by Stack Effect

Abstract Limited by terrain and other factors, highway tunnels usually have a longitudinal slope. In inclined tunnel fires, the mechanisms of asymmetric smoke flow and its factors have only been studied to a limited extent. Therefore, the smoke flow characteristics in inclined tunnel fires are studied using numerical simulation. Smoke flows asymmetrically in the inclined tunnel because of the stack effect. The stronger the stack effect, the more smoke flows downstream, and the quantity of air supplied from the upstream portal also increases. The heat release rate, downstream length, and slope all impact the asymmetric flow phenomenon in the slanted passageway. The mass flow rate difference between smoke and air on the one side of the fire source is describes as the induced mass flow rate to quantify the asymmetric flow effect. The HRR, downstream length and tunnel slope are positively correlated with the induced mass flow rate.