Scale Modeling Studies on Smoke Control using Smoke Screens in a Titled Tunnel Fire

Abstract

Many tunnels, which are inclined to the horizontal, are built in Mainland China, Hong Kong and Taiwan. Smoke control systems are installed to minimize damage in tunnels in case of fire. However, the designs of smoke control systems were based on presumed smoke movement pattern without any experimental justification. Although smoke screens are always used for blocking smoke spread beneath the ceiling, the smoke movement in tilted tunnels with smoke screens is not fully understood. On the other hand, Computational Fluid Dynamics is widely applied to study smoke movement in big enclosures. Officers now have much better understanding on fire models. There are always challenges in the studies of smoke movement in fire hazard assessment, when only Computational Fluid Dynamics is adopted. Scale models are required to justify the numerical predictions.

In this paper, smoke movement pattern in a tilted tunnel model with smoke screens was studied. Data compiled from two sets of scale modeling experiments in tunnels, which are of same cross-sectional areas but in different shapes, were used. It was observed that smoke screens are not effective in blocking upward smoke movement in tunnels which are tilted to the horizontal by larger angles. This finding is very different from the smoke movement patterns assessed in many smoke management designs in tilted tunnels.