Flow field characteristics and jet fan deflection angle at tunnel with over development
The tunnel with over development is a complex structure,which has a turbulent ventilation flow field,tunnel operation ventilation capacity is difficult to be guaranteed.It is important to expose the characteristics of the ventilation flow field and to optimize the tunnel fan arrangement parameters.In this paper,based on a Pearl River tunnel project in Guangzhou,numerical simulation method was used to explore the characteristics of tunnel ventilation flow field and fan boosting capacity under different fan deflection number and deflection angle conditions.The results are drawn as follows.The restricted installation position of fans in tunnels with over development and the large ventilation resistance of complex structures lead to uneven distribution of tunnel ventilation flow fields,poor pressure-raising capacity of fans,and difficulty for fans to provide reliable operational ventilation capacity.For the tunnel with over development,which is set three ceiling fans at the top,by reasonably setting the number of fan deflection and fan deflection angle,it can stabilize the tunnel ventilation flow field,increase the average wind speed and optimize the ventilation effect in the tunnel.When the three ceiling fans are all deflected or the fan deflection angle is greater than 5°,although it can increase the ventilation velocity on the side of the uninstalled fan,but also lead to uneven distribution of the air jet in the tunnel,the ventilation velocity on the side of the installed fan is reduced.Too much jet deflection will carry more kinetic energy to hit the tunnel wall,resulting in increased energy loss suffered by the air jet,which is not conducive to the stability of the tunnel ventilation flow field.Two ceiling fan deflection 2°～5°,the tunnel flow field distribution is uniform,fan pressure-rise coefficient is 0.7～0.8,the tunnel fan jet resistance loss of about 28～29 Pa.It can enhance the fan pressure-rise,reduce fan jet resistance loss,conducive to the tunnel with the operation of ventilation.The results of the study provide a reference for optimizing the layout of jet fans in tunnel with over development and ensuring operational ventilation effects.
safety engineeringroad tunnelover development of buildingsjet fanventilation flow field characteristics
万方数据
维普
