Evaluating the Temperature Profile in a Branched Tunnel Fire with Various Ramp Slopes: An Experimental Study

This study conduct a set of small-scale experiments to examine the combined impact of ramp slopes and bifurcation angles on the longitudinal temperature profile beneath the ceiling of a model of branched tunnel. A Liquefied Petroleum Gas (LPG) fire was used to simulated car fires. The range of heat release rates for the experiments was 2.57 kW to 7.70 kW. The experiments also encompassed three bifurcation angles (5 degrees to 15 degrees) and five ramp slopes (0%, 3%, 5%, 7%, and 9%). A simple model was developed to analyze the steady fire-produced ceiling jet in the branched tunnel. It has been found that the longitudinal temperature decay was not affected by the ramp slopes and bifurcation angles. However, the longitudinal temperature decay varied across different tunnel regions due to the dimensions of the tunnel cross section and the branched structure resulting in smoke divergence flow. In addition, the study established a modified model of longitudinal temperature decay based on the experimental results. The results could be used as a point of reference in developing smoke extraction tactics for branched tunnels.