Improving Propeller Efficiency Through Tip Loading

This paper examines the potential performance gains of tip loaded propellers (TLP) in general and presents specific findings for a sample case. Potential flow simulations, Reynolds-Averaged Navier-Stokes (RANS) viscous flow simulations and experimental methods were used to assess tip loaded propellers designed by the authors from the Naval Surface Warfare Center, Carderock Division (NSWCCD) and the Sistemar company, for the same performance requirements using different design approaches. A reference design of a conventional open propeller was also developed and assessed using potential flow and viscous RANS methods. The differences in performance between model and full scale were studied using a viscous flow RANS solver. The sources of the scaling effects are identified and differences between the scaling of conventional and TLPs are examined. Both TLPs designed by NSWCCD and Sistemar are predicted by the RANS flow solver to be more efficient than the conventional propeller at full scale. Relative to the conventional propeller, the NSWCCD-designed TLP is predicted to have higher efficiency at the design point as well as increased cavitation inception speed.