The Influence Of Velocity Of Jet Fan Outlet On Internal Flow Characteristic In Tunnel

With the development of road traffic and tunnel total mileage in our country is increasing quickly, the issues in tunnel ventilation systems are also become more and more serious. Due to the advantages-low running cost, low equipment cost, simple flow control, convenient installation and maintenance, longitudinal ventilation system is mainly used in highway, rail and subway tunnel。The jet fan exit velocity file has a great influence on the internal tunnel ventilation. When the simulate analysis of internal flow of tunnel was done, the jet fan outlet velocity file is the real value, rather than ideal value in some study of literature. In China, jet fans for tunnel mostly supplied by domestic enterprises. And in the design of jet fan diff-user, export duct length is too short, this has led to the fan outlet structure into a resistance element which consumed energy, thus reducing the efficiency of jet fan unit, and increasing the energy loss. Studies are as follows:The first part, the optimization of jet fan cowl design. With FLUENT software used, internal flow of jet fan has been simulated. Fist of all, by changing the length of exit duct of jet fan without exit cowl, a series of numerical simulation research has been done, then change the angle of the exit cowl. The calculation results show that the length of exit duct and structure of exit cowl has obvious influence on jet fan aerodynamics performances and reasonable export structure can effectively improve jet fan aerodynamic performances.Part two, set the jet fan outlet velocity field as a boundary condition of jet fan working inside the tunnel, and the internal flow of tunnel has been simulated, in order to set the outlet velocity file as real value. When one jet fan and two jet fan and four jet is set inside tunnel respectively, with different jet fan outlet velocity, the numerical simulation research has been done. The calculation results show that the different jet fan outlet velocity file has a great influence, and according to outlet velocity file for simulating tunnel fan selection, the error could be caused.