Effect of Fire Source Elevation on the Smoke Spreading Characteristics in an Extra-Long Tunnel

In this work, the influences of fire source elevation on the smoke spreading characteristics involving thermal smoke stratification and temperature distribution upstream conducted experimentally in a full-scale tunnel were successively explored. The results indicate that Newman's hypothesized thermal smoke stratification based on the dimensionless temperature difference ratio agrees quite well with this measurement regardless of the elevation of the fire source. The relationship between the dimensionless temperature difference ratio and Froud number ( Fr ) is modified for various fire source elevations by substituting the effective height ( H ef ) for the tunnel height ( H ). Concerning the upstream characteristics of smoke temperature decay, the decay coefficient k exhibits a non-linear growing tendency in response to the dimensionless fire source elevation created by this work. Finally, a modified correlation based on Hu's model is constructed which can be used to forecast temperature distributions upstream at various fire source elevations. The current research helps us understand the smoke dispersion characteristics of different types of vehicles, which is extremely important in the design and evaluation of fire systems.