Interaction of Propeller Pitch Distribution and Multiple Energy Saving Devices

-The Effect of Propeller Pitch Distribution and Stern Duct on the Flow Field around the Rudder -

Abstract

　Recent years, merchant ships are equipped not only with high performance propeller, but also with multiple ESDs (Energy Saving Devices) to recover energy losses, so propulsion performance has been greatly improved. There is a possibility that propulsion performance can be improved by integrating propeller and multiple ESDs.

　In our previous study, the self-propulsion test results with the multiple ESDs like stern duct and rudder bulb showed the highest energy-saving effect, namely 15.0% compared with bare hull. In addition, the maximum difference of BHP (Brake Horse Power) caused by differences in propeller position and pitch distribution was 4.9%. The PIV (Particle Image Velocimetry) measurement results confirmed that the flow field in front and behind the propeller changed depending on the propeller position and pitch distribution, and the interaction among the propeller and the ESDs also changed.

　After the previous study, additional self-propulsion tests including rudder resistance measurements were conducted using propellers having three different pitch distributions and the multiple ESDs. Furthermore, the flow field changes in front of the rudder due to the presence of stern duct and the difference of propeller pitch distributions were analyzed by PIV measurement results. In this paper, the authors focus on the thrust deduction factor and describe the energy-saving effect due to changes in rudder resistance.