Experimental investigation on smoke spread characteristics and smoke layer height in tunnels

Abstract

Summary A series of experiments were carried out in a model‐scale tunnel with dimension of 6.0 m × 1.0 m × 0.7 m to investigate the smoke spread behaviors and the typical smoke layer height. Alcohol was employed as fuel, and the heat release rate was set to be 9.5, 18.4, 30.1, and 63.5 kW, respectively. The temperature profile in the tunnel was measured, and the buoyant flow stratification conditions were visualized by a laser sheet. The experiment results show that the N percentage rule would greatly influence by subjective factors. As the N (10, 20, 30) value increases, the smoke layer height also increases. The results calculated by the buoyancy frequency method were more accurate. Fan's prediction method (Fan WC, Wang QG, Jiang FH. Concise Guide of Fire Science. He Fei: University of Science and Technology of China Press; 1995.161 p.) does not accurately evaluate the smoke layer thickness in tunnel fire. An enhanced empirical formula for predicting the smoke layer thickness in the one‐dimensional horizontal spread stage was proposed. It is shown that the empirical formula could well predict the smoke layer thickness by comparing with the experimental data of previous studies.

Study on the smoke back‐layering and critical ventilation in the road tunnel fire at high altitude

“…Meanwhile, the air entrainment during the fire plume rising in the lower pressure is weak, and the weak air entrainment means that the less cold air is entrained, which also results in the higher temperature of smoke gas beneath the ceiling in the near area above fire source. After all, most heat released by combustion is used to heat up the fire plume or the smoke gas . The primary reason for the decrease of ceiling temperature in the process of spreading horizontally is the heat loss from the smoke flow to the compartment boundary and ambient air.…”

“…After all, most heat released by combustion is used to heat up the fire plume or the smoke gas. 32 The primary reason for the decrease of ceiling temperature in the process of spreading horizontally is the heat loss from the smoke flow to the compartment boundary and ambient air. Much more heat is lost during the horizontal spreading is the reason for the fast decay of ceiling smoke temperature in the lower ambient pressure, and the detailed mechanism will be studied in the future.…”

Experimental Investigation on the Discharge of Pollutants from Tunnel Fires

“…A reduced-scale tunnel (1:10 scale) was used in this paper, as shown in Figure 2, which length, width, and height were 6.0 m, 1.0 m, and 0.7 m, respectively. This model tunnel was introduced in our previous research [32]. It was constructed by using a fireproof steel frame structure, fireproof slab, and fireproof glass.…”

Study on the heat exhaust coefficient and smoke flow characteristics under lateral smoke exhaust in tunnel fires

“…However, the fire safety issue of tunnel is receiving increasing attention . When a fire occurs in a tunnel, the smoke exhaust and heat dissipation conditions are poor, and the toxic smoke with high concentration and temperature is not easily discharged . The evacuation and firefighting are difficult, and the damage of tunnel is serious.…”

“…2 When a fire occurs in a tunnel, the smoke exhaust and heat dissipation conditions are poor, and the toxic smoke with high concentration and temperature is not easily discharged. [3][4][5] The evacuation and firefighting are difficult, 6,7 and the damage of tunnel is serious. Fires can cause traffic congestion and lead to serious casualties.…”