Internal Flow Analysis And Optimization Design In Single-stage Subway Axial Fan

Axial fans have a wide range of use in national life.In recent years,with the development of underground transportation,it has achieved large-scale development.However,the energy consumption of fans is relatively large,accounting for about 15%of the total domestic coal consumption.Thus,it's beneficial to improve the energy use efficiency of fans,which has a significant contribution to the economy and environment.What's more,Improving the aerodynamic performance and design level of axial fans plays an important role in facilitating the rational distribution of current resourcesThe paper takes a single-stage subway axial flow fan as the research object and numerical simulation of the original axial fan model is conducted.The numerical simulation results are compared with the experimental data,ensuring the accuracy and the rationality of the simulation According to above simulation results,the further studies of the internal flow characteristics on the fan are analyzed.On the basis of that,the influence of dynamic and static structure on the performance of the fan are studied,including the tip-clearance structure and inlet and outlet pipes Finally,a new multi-element optimization scheme is proposed,and new model is built for numerical simulation verification.The results drawn in this paper are as follows(1)The effect of grooved blade tip on the aerodynamic performance of a single-stage axial fan is studied.The results show that the shape of the grooves,the number of grooves and the depth of the grooves affect the flow in the tip region.After the blade tip on the groove,the tip-leakage flow field and flow loss distribution are both improved.In contrast,the stepped-groove tip model has good aerodynamic performance,but as the depth of the groove increases,the rectangular-groove has a more stable working range.The grooved blade tip changes the relative height of the blade tip clearance,which reduces the tip-leakage flow and losses.(2)The effect of pipe structure including inlet pipe and outlet pipe on the performance of the fan is studied.The results show that 90° inlet bend adds the uniformity of the inflow when shortening the axial length of inlet pipe.The fluid inside the elbow is easy to flow and separate,forming a recirculation zone and reducing fan performance.Adding a diffuser to the fan outlet section saves a lot of space on the basis of ensuring the aerodynamic performance of the fan.The diffuser can reduce the kinetic energy of and increase the static pressure efficiency of the fan outlet.The diffuser optimal enlargement coefficient of cross-section is 2.35.The diffuser baffle plays a role of secondary rectification,improving the flow conditions,reducing the secondary flow and turbulence at the outlet,and making the wall loss decreased(3)The impeller and guide vane of the axial fan are mainly studied,and the blade installation angle,leading vane,impeller speed and tip clearance height are selected as optimization parameters.The aerodynamic performance of the fan is improved by orthogonal optimization tests,especially at low flow conditions.The flow conditions near the optimized blade root are improved,and the energy loss of flow are greatly reduced.At the same time,the directional pressure fluctuation on the middle of the blade is weakened by this way.