Study On The Effect Of The Aerodynamic Performance Of Axial Fan With Tip End-plate

The aerodynamic loss caused by tip clearance accounts for about one third of an axial fan.Hence,controlling the flow of blade effectively and improving the aerodynamic performance of the axial fan have always been research highlights.As one of a methods to passively control tip leakage,tip end-plate technology has already been studied and applied in other impeller machinery fields.Aiming at providing effective guidance and suggestions for axial fans installed by tip end-plate at design stage,the aerodynamic performance of axial fan influenced by installation position,width,length and installation angle of tip endplate are simulated using full-channel numerical simulation method.Control mechanism and influence law about structural parameters to complicated three-dimensional flow of axial fan’s tip clearance have been analyzed.(1)Tip end-plate installed in pressure and suction surface of axial fan can both extend tip leakage flow length,increase leakage flow resistance as well as reduce tip leakage flow rate effectively.In pressure surface,the core of tip leakage vortex offsets to suction surface and the vortex shedding point moves backward so that the axial fan can entrain much more low energy flow in suction surface as well as increase the intensity and scope of tip leakage vortex,which results in aerodynamic loss increasing.Tip end-plate in pressure surface worsens tip leakage flow.On the contrary,the position of leakage vortex core moves to the opposite direction and accelerates its shedding,decreases entrainment of low energy flow,so that it can decrease the intensity and scope of tip leakage vortex and aerodynamic loss as well.So that the design point tip leakage rate is reduced by 7.1%,total pressure efficiency increased by 0.58%.(2)With width increasing of tip end-plate in suction surface,the flow passage of tip leakage has been extended and its flow rate has also been reduced apparently.Meanwhile,the position of leakage vortex core offsets far away from suction surface and decreases entrainment of low energy flow.When the width of the winglet is 3 times the relative thickness of the blade,the leakage rate of the design point is reduced by 13.7% and the total pressure efficiency is improved by 0.73%.(3)Blade leakage vortex and tip end-plate leakage vortex are divided by tip leakage vortex due to different lengths of tip end-plate in suction surface.Both of them lead aerodynamic loss in interaction.With the extended length of tip end-plate,the tip end-plate leakage vortex increases while the blade leakage vortex decreases.Aerodynamic loss,tip leakage rate and the total pressure efficiency are almost the same between tip end-plates of 0.6c and c.Both of them have same effects on tip leakage flow’s improvement.(4)Tip end-plates in different installation angles can all reduce tip leakage flow,decrease intensity and scope effectively,and reduce aerodynamic loss of axial fan as well.It can also promote total pressure coefficient and efficiency at large flow area,while it decreases range with increasing of installation angle.