Investigation on the characteristics of fire burning and smoke spreading in longitudinal-ventilated tunnels with blockages

The present study investigated the ventilation and blockage effect on fuel burning rate, the maximum temper-ature, critical velocity, and smoke back-layering length in longitudinally ventilated tunnels. Quantitative analysis was carried out by analyzing massive experimental measurements from the published literature. Three typical blockage modes were extracted to illustrate the blockage effect. Results indicated that fuel burning rate exhibited different responses towards the longitudinal ventilation, wherein burning rate of acetone, gasoline, ethanol, heptane, and wood crib increased when the wind velocity increased from 0.0 m/s to 3.0 m/s while burning rate of methanol pool fire firstly decreased and then increased. Prediction of the maximum temperature in tunnels without blockage by using previous correlations agreed well with the literature data. However, the maximum temperature was poorly estimated when the blockage effect was introduced. Modified correlations were thus established considering different blockage ratios. Meanwhile, empirical formulae to calculate the critical velocity and smoke-back-layering length in tunnels with and without blockages were also proposed, presenting good agreement with the measurements from previous literature.