Asymmetric Preswirl Stator Design for U.S. Coast Guard Island Class Patrol Boats

摘要

This report presents the design of an asymmetric preswirl stator for the U.S.Coast Guard Island Class patrol boats. The purpose of the stator is to eliminate a cavitation erosion problem for the propellers. The methods used to analyzed the existing propeller and design the asymmetric stator employed extensions to the conventional lifting-line and lifting-surface techniques. The use of a non-axisymmetric lifting line program made it possible to determine the configuration and load distribution which best reduced the likelihood of cavitation erosion. A lifting surface program written specifically for non-axisymmetric stators was used to determine the design geometry. The two dimensional cavitation buckets with corrections for three dimensional effects were used for prediction of the blade surface cavitation inception. Also, a panel method was used for prediction of chordwise pressure distributions in a quasi-steady manner. The predicted cavitation inception at the radius of the erosion was increased by 3.5 to 5.5 knots; however, cavitation was not quite eliminated at the full power condition. No significant effect on powering was predicted.