Abstract: Numerical simulation was implemented to study the smoke spread distance, temperature distribution, smoke exhaust velocity and exhaust efficiency by considering the variation of the heat release rate（HRR）, interval of the adjacent exhaust vents, exhaust volume, exhaust vent dimension and tunnel height. The results indicate that the under a given HRR fire?induced smoke spread distance in the point extraction system is shortened as the smoke extraction volume increases, and the ceiling gas temperatures decrease. Besides, under a certain smoke extraction volume, a larger aspect ratio of the smoke vent can control the smoke within a shorter distance. It is also found that the interval of adjacent vent has slight effect on the smoke exhaust efficiency. Based on the results obtained in this work, the suggested values of the smoke exhaust volume and arrangement of the exhaust vent for the fire of 5 MW and 20 MW are given.

Key words: tunnel fire, point extraction system, smoke extraction volume, extraction vent dimension, smoke exhaust efficiency