Propeller Erosion Reduction with an Asymmetric Preswirl Stator

Abstract

This paper presents the results of a series of model-scale tests of the erosion-reduction capabilities of a partial-span asymmetric preswirl stator on the propeller of a large United States Coast Guard (USCG) patrol boat. The propeller and stator were tested at one-third scale (A - 3 .2) in the DTRC 36-inch Variable Pressure Water Tunnel (VPWT). A single shaft strut upstream of the propeller and a shaft inclination of 9.25° simulated the full-scale propeller flow field. Cavitation erosion tendency was investigated using an erodable coating painted on the propeller blades. Stator performance was evaluated in a series of model tests at 30 knots, both with and without the currently- installed cavitation relief holes, using three different series of stator blade angle of attack settings These high Reynolds number experiments showed that the blade root erosion tendency was almost completely eliminated by the preswirl stator with the cavitation relief holes at the propeller blade root closed. A lesser degree of erosion relief was provided by the preswirl stator with the cavitation relief holes open.