Effect of tip clearance, winglets, and shroud height on the tip leakage in axial flow fans

•Winglets increase the efficiency of the partially shroud-covered axial fan.•Winglets decrease the efficiency of the 100% shroud-covered axial fan.•The fan efficiency is not the highest with 0 tip clearance in partial shroud.•The fan efficiency is the highest with certain tip clearance in partial shroud. This study is concerned with the improvement in efficiency of axial flow fans that are being used in numerous fields including outdoor units of air conditioners. The tip leakage flow occurring between a blade tip and shroud is one of the major losses in the axial flow fan. A well-known method used to control such tip leakage flow is locating winglet on the suction side of blade tips. Only a few articles have studied the impact of tip clearance on the flow structure of tip leakage flow of axial flow fans with winglet. In this study, the flow structure occurring on the blade tip due to the location of a winglet was analyzed. We confirm the existence of an optimal tip clearance which results in the maximum efficiency for an axial flow fan with a shroud height measuring 30% of the axial chord length.