Numerical study on lateral centralized smoke extraction in immersed tunnel with a new-style inclined smoke barrier

In road tunnel fires, it is essential to keep high smoke extraction efficiency, especially for the immersed tunnels. A new-style inclined smoke barrier was proposed for the improvement of lateral smoke extraction. A series of fire scenarios were investigated with different barrier heights, fire sizes, vent aspect ratios and included angles between smoke barrier and tunnel sidewall. Results show that installing an inclined smoke barrier can improve lateral smoke extraction effectively. Overall, a higher inclined smoke barrier contributes to the lateral smoke extraction, and the smoke extraction improvement is better for those cases under smaller fire size; meanwhile the inclined smoke barrier shows a higher efficiency with the narrow and high lateral exhaust vent. The lateral smoke extraction efficiency curve can be divided into three regions along with included angles, namely the rapidly increasing region (0°<θ≤30°), the stable region (30°<θ≤75°), and the slightly decreasing region (75°<θ≤90°). Better smoke extraction efficiency can be guaranteed when 30°<θ≤75°. To further explore the lateral smoke extraction efficiency, an empirical description model is developed to predict the smoke extraction efficiency improvement (IE). The outcomes could offer a basic guidance for the design of lateral smoke extraction system in immersed tunnel.