Improvement of the efficiency for rim-driven thrusters through acceleration of gap flow

Abstract

Efficiency optimization of the rim-driven thruster (RDT) has emerged as a prominent research topic in recent years. In this work, the Reynolds-averaged Navier-Stokes (RANS) solver is employed for simulating open water performance of RDTs, aiming at improving the efficiency of RDTs. Specifically, a series of RDTs are obtained by modifying the Ka4-70 propeller with a 19A duct, and their thrust and torque components, as well as efficiency and gap flow, are thoroughly examined. The investigation commences by exploring the impact of different rim sizes on RDT efficiency. A comparison is conducted between the open water performance of RDTs and the ducted propeller. Subsequently, a case with relatively high efficiency is identified, serving as a basis for the development of a series of modified RDTs equipped with acceleration devices. These devices facilitate accelerated axial flow in the gap, thereby enhancing the thrust generated by the duct, while simultaneously reducing the torque exerted on the rim through accelerated circumferential gap flow. Comparative analysis reveals that the improved RDTs can achieve an open water efficiency increase of up to 10.9% when the advance coefficient is set to 0.6, resulting in an efficiency value of 0.519. The findings presented in this paper introduce a novel direction for optimizing the efficiency of RDTs, contributing to the advancement of this field of study.