ASHRAE - American Society of Heating@ Refrigerating and Air-Conditioning Engineers@ Inc.
Scope
INTRODUCTION In a tunnel environment@ development of fire and smoke spread are affected by the fire set-up and ventilation conditions in the tunnel. During normal traffic operation@ smoke can be diluted or pushed away from the detection system by the normal ventilation system@ which is designed to maintain acceptable levels of contaminants in the tunnel (Beard and Carvel 2005). It can create conditions that may challenge the ability of detectors to detect and locate the fire in the early stage if the fire is enclosed in a vehicle or located behind an obstruction. In order to achieve early detection of fires in a tunnel@ it is essential to understand how fire develops and smoke spreads during the initial stage of fire under various conditions. An extensive Computational Fluid Dynamics (CFD) study was carried out as part of the International Road Tunnel Fire Detection Research Project (Liu et al. 2006a)@ which aimed at investigating the detection performance of current fire detection technologies. The CFD study included simulations of full-scale tests conducted by the National Research Council of Canada (NRCC) in the Carleton University laboratory tunnel and a series of simulations to examine effects of various fire scenarios and different ventilation schemes. Findings of this CFD study were (Kashef et al. 2008 and Ko et al. 2008); ? Simulated results exhibited relatively good agreement with laboratory test results. ? Temperature development inside the tunnel was considerably affected by fire scenarios@ such that temperature rise near the ceiling was less significant for fires enclosed by a vehicle body than that for open fires. ? The simulations agreed with the laboratory test results in that the longitudinal airflow affected the burning behaviour of the fire and smoke spread in the tunnel. Moreover@ the impact depended on the relative size of fire to the airflow velocity@ as well as the fire scenario. In general@ the ceiling temperature decreased with an increase of airflow. ? The development of temperature depended on the ventilation scheme (longitudinal@ semi-transverse and fullytransverse ventilation systems) inside the tunnel. ? The length of the tunnel did not have a significant impact on the temperature development near the ceiling close to the fire location. Thus@ the results found in the laboratory tunnel scale can reasonably be extrapolated to longer tunnels. In order to further investigate and verify these results@ field tests were conducted in an operating tunnel environment. This paper reports the CFD study carried out to simulate the field tests conducted in Tube A of the Carr??-Viger Tunnel in Montreal. As well@ the paper presents the results of the study and comparisons between model predictions and experimental data.