Numerical investigation on hub effects of hubless-rim driven propeller

Abstract

Since the beginning of humanity, various methods have been developed for the interaction of countries with each other. Therefore, people have developed various methods of transportation in order to strengthen political and economic relations, explore new places and access resources in new places. Maritime transportation is one of these prominent methods to create interactions among countries. Thanks to the developments in the field of maritime transport, humanity has made significant progress in numerous fields. Ships have been a widely used vehicles for transportation and ships are generally driven by the shaft-propeller mechanism. Energy occurred from fuel, nuclear or electrical is transferred to propeller via a transmission mechanism. During this drive movement, undesirable problems such as increased fuel consumption, reduced mechanical efficiency and noise may occur and these problems may cause irreversible damage to the shaft mechanism. Besides the effects of climate change dramatically continue to increase and marine transportation sector is one of the causes to emit more CO2 in the world. Therefore, hubless Rim Driven Propellers (RDP) has been developed and used for various marine vehicles in order to prevent above-mentioned problems. The working principle of RDP can be summarized as an electric motor driving the propeller with the help of the rim. However, since hubless RDP technology is a new field of marine researches, information on how changing the dimensions of the hub affects the hydrodynamic performance of the propeller is scarce. In this master's thesis, analyzes were made for hubless RDP design with five different hub ratios (0.05, 0.1, 0.15, 0.167, 0.25) by means of various dimensionless parameters to monitor the performance effects of the propeller. Ka4-70 propeller was selected for these five designs. They were solved numerically benefiting from Unsteady Reynolds Averaged Navier-Stokes equations (URANS) and Shear Stress Transform (SST) k-ω turbulence transport equations. Numerical operations were handled on the finite volume method solver Simcenter STAR-CCM+ solver, using the Rigid Body Motion (RBM) approach. The Computational Fluid Dynamics (CFD) results have been conducted in terms of non-dimensional parameters such as thrust coefficient (KT), torque coefficient (KQ), and efficiency (η) ranging from 0.1 to 0.6 advance ratio (J) for 600 rpm. It was monitored that KT, KQ, and η increased as the hub ratio increased under a certain rotation speed until the hub ratio =0.167. Due to no experimental data for hubless RDP, validation studies were able to conduct with hub type propeller. Accordingly, an ideal propeller configuration can be determined by comparing numerical results and experimental data.