Spatial Layout Optimization of Jet Ventilation Fan for the Rectangular Large Section Underwater Tunnel

According to the rectangular large-section underwater tunnel has the characteristics of “ultra-wide and flatness,” its physical structure and the layout of jet fans in longitudinal ventilation are different form traditional road tunnel. To obtain the optimal boosting effect of jet fans longitude ventilation and clarify the optimal installation parameters of jet fans in the rectangular large section tunnel, relying on the Taihu Tunnel, the 3D longitudinal ventilation model of the jet numerical model is established by using the CFD software Fluent. Through the boosting influence coefficient of jet fans, the jet longitude ventilation quality is judged. Then the factors for the pressure rise of ventilation fans, including setting height of fans, transverse distance and longitudinal distance among fans, was discussed. The results show that the farther the distance from the jet fan to the top wall of the tunnel, the greater the boosting influence coefficient. When the transverse distance of the jet fan increases, the boosting influence coefficient of the jet fan first increases and then decreases. When the longitudinal distance of the jet fan increases, the booster coefficient of the jet fan first increases and then decreases. Finally, considering the tunnel building line, the jet fans should be located at 1.2∼1.4 times fan diameter from the upper wall for Taihu Tunnel, the transverse distance of jet fans should be set to 1.5∼2 times fan diameter and the longitudinal distance of jet fans should be set to 150∼170 m.