Experimental investigation and analysis of the diffusion flames and maximum temperature characteristics of rectangular burner with weak and strong plumes in a bifurcated tunnel

The rectangular energy source like automobile fire in bifurcated tunnels may contribute to the complexity of flame morphology and temperature characteristics, while deficient efforts have been undertaken in this area. The diffusion flames and maximum temperature characteristics of the rectangular burner with weak and strong plumes in a bifurcated tunnel, where the burner aspect ratio, effective ceiling height, and the energy heat release rate are varied, were investigated in this work through a series of experiments. The results indicate that the flame generated by the weak plume is somewhat tilted towards the sidewall due to asymmetric air entrainment. The height and width of the flame were significantly affected by the burner aspect ratio. A simplified model was developed to predict the flame height. The extension length of the ceiling flame driven by the strong plume along the ramp side is slightly larger than that on the sidewall direction. The flame extension length decreases with the increasing burner aspect ratio and effective ceiling height. A prediction model of ceiling flame extension length was derived using dimensional analysis and experimental data. The coefficient of the power function is 0.38 which approximates the value of 2/5 in previous models. The maximum excess temperature of the ceiling jet in both the non-continuous flame zone and the continuous flame zone can be articulated. Analyzing the prior models yields a modified correlation of the maximum excess temperature.