Experimental Study on Smoke Spreading Laws for Tunnel Fires with Moving Fire Source

Compared with a stationary fire, the spread of smoke in a moving fire source is more complex, which means hazardous consequences. The study of smoke flow and distribution of ceiling temperature is essential for effective emergency response strategies and efficient execution of rescue operations. To study the smoke flow characteristics of a tunnel fire with a moving fire source, we constructed a 1:20 scale tunnel model and conducted experiments with a moving fire source. Six different moving velocities (0.1, 0.15, 0.3, 0.5, 0.8, and 1.0 m/s) were selected for the experiment. The focus of the experiment was to analyze the stability of the smoke and the temperature distribution of the tunnel ceiling under the moving conditions of different fire sources. The results show that when a fire source velocity is below 0.3 m/s, countercurrent smoke occurs in the tunnel. The smoke layer is stable, and the temperature in the center of the tunnel exceeds the sidewall temperatures. When the velocity reaches 0.3 m/s, smoke inversion disappears, the smoke layer begins to become unstable, and the temperature of the tunnel increases while a central zone of low temperature is formed. The faster the fire moves, the longer the central low-temperature zone will be in the tunnel.