Effects of Blade Tip Foil Thickening on Tip Vortexes in Ducted Propeller

Abstract

A thick tip foil blade was designed to reduce the tip leakage flow and weaken the tip vortexes in ducted propeller 19A/Ka4-55. The thick tip foil was constructed by normal extrusion of the original tip foil. The maximum thickness of the foil increased from 1.64% chord length to 7.64%. The commercial CFD code CFX was employed to simulate the flow field of the two ducted propellers. From the performance curves, it could be concluded that the tip foil thickening will not affect the thrust and torque of the ducted propeller much. The tip leakage vortex (TLV) in the thick tip foil propeller was obviously weaker than that in the original propeller. The pressure drop in TLV middle chord position decreased by 32.8%. In the tip clearance, both propellers have the tip clearance vortex. The difference is that the tip clearance vortex in the thick tip foil propeller could form an expansionary channel in the tip clearance, which made the tip leakage flow slow down, and hence weaken the TLV.