Study on Compact Pre-Swirl Duct for Slender Aft-Body Crude Oil Carrier

Abstract

This study is a parametric investigation of the application of a compact type of pre-swirl duct for a slender aft-body 158k crude oil carrier. The International Maritime Organization (IMO) has created the Energy Efficiency Design Index (EEDI), which is an index related to carbon dioxide emissions, to enforce regulations on newly built ships; many solutions have been proposed, including an increase in propulsion efficiency. In the present study, a new type of energy-saving device (pre-swirl duct), the so-called ring stator, is proposed for 158k crude oil carriers, the hull form of which has been developed as a slender after-body full form to reduce the resistance by delaying separation. A conventional pre-swirl duct is no longer effective at the slender aft-body hull forms because of the small radial flow to the propeller. A parametric study was conducted through Computational Fluid Dynamics (CFD) analysis using the commercial program Star-CCM+, and an improvement of approximately 3% in the propulsion efficiency was achieved in the present study. The efficiency gain was validated through a comparison with the experimental results. The developed ring stator may become applicable to container ships through further parametric studies in the near future.