The maximum gas temperature rises beneath the ceiling in a longitudinal ventilated tunnel fire

This paper studies the maximum gas temperature rises beneath the ceiling in tunnel fires. The fire scenarios with higher longitudinal ventilation velocities are of key concern. This work was done in a 1/10 model-scale tunnel and propane gas burner was used as fire source. The variables include longitudinal ventilation velocity and heat release rate. In this study, the dimensionless longitudinal ventilation velocity varies from 0 to 0.84 and the dimensionless heat release rate is less than 0.15 in all tests, corresponding to a scenario of small fire. It is assumed that the maximum gas temperature rises in the longitudinal ventilated tunnel fires almost equals that in tunnels without longitudinal ventilation by use of the length of inclined path of plume as the effective tunnel height. By analyzing the length of inclined path of smoke plume that correlates the plume inclination angle, a piecewise model for predicting maximum gas temperature rises was developed, using the dimensionless longitudinal ventilation velocity of 0.42 as the dividing point. The comparisons between the calculations from this new model and the experimental results in this study as well as some data collected from other tests show a good agreement.