Abstract: The piston wind would be produced when the vehicle is driving in the tunnel, the effective use of piston air could reduce the cost and energy consumption of mechanical smoke extraction system. In this paper, the theoretical analysis was carried out first, and then the smoke spread characteristics of the highway tunnel under piston wind were investigated by using the computational fluid dynamics software. Numerical simulation was carried out to explore the influence of different piston wind speeds on smoke layer movement, temperature field and velocity field distribution under different heat release rate (10,30, 50 MW) in the tunnel. The results showed that the recent and long- term piston wind speed attenuation model have the same variation rules of smoke layer movement, temperature field and flow velocity field under different heat release rates. With the heat release rate became larger, the time for smoke to return to the tunnel entrance was shorter, and the time for the flow velocity field to change was later.

Key words: fire, super- long highway tunnel, piston wind, fire characteristics, numerical simulation