Session: 06-15-01 Unsteady Hydrodynamics, Vibrations, Acoustics and Propulsion

Submission Number: 157189

Optimization of Propeller Boss Cap Fin Design Using Surrogate-Based Model and CFD Simulation 

The global shipping industry consumes huge amounts of energy annually. To reduce energy consumption of the ships, one of the strategies is to install an energy saving device behind the propeller, i.e., propeller boss cap fin (PBCF), to increase the overall propeller efficiency. The PBCF is fitted on the boss cap, the central part of the propeller, to reduce the energy loss caused by the hub vortex. This vortex is formed by the difference in pressure between the face and back of the propeller blades. The PBCF improves the efficiency of the propeller by disrupting this vortex, leading to a reduction in fuel consumption and an increase in propulsion efficiency. Additionally, it can reduce propeller-induced noise and vibrations. The PBCF is widely used in the maritime industry to enhance the environmental performance and economic efficiency of ships.

In this work, a design procedure of the PBCF is introduced. It involves airfoil and fin shape optimization and PBCF performance evaluation. The airfoil optimization is performed under the ship’s operating condition, i.e., given ship advance ratio and propeller rotating speed, using an engineering tool and surrogate-based optimization to achieve maximum net thrust. The Kriging model is adopted as the surrogate model of the force. The optimization has two phases: design of experiment process and refining process. The termination of the refining process is based on the convergence of the objective function or the total allowance of the simulation budget. The optimized airfoil demonstrates improved performance compared to the original design at the design point. The parameters describing the three-dimensional shape of the PBCF, such as fin height, twist angle, phase angle and cap shape, are then optimized one at a time through iterative adjustments. These adjustments are guided by performance data obtained from computational fluid dynamics (CFD) simulations. Thrust and torque on fin, cap and propeller are analyzed for better understanding of the force contribution from each component. Both straight for constant pitch angle and twisted fin with linearly increased pitch angle are investigated. CFD simulations show that the efficiency of the propeller equipped with the optimized PBCF can increase by up to 1.3% compared to the propeller without PBCF. Increase in propeller efficiency with an optimized straight fin is comparable to that achieved with an optimized twisted fin. With this design optimization framework, propeller performance can be improved, resulting in better fuel efficiency and cost savings.

Presenting Author: Xiaoqin Zhang Institute of high performance computing

Presenting Author Biography: Dr. Zhang Xiaoqin is a senior scientist at Institute of high performance computing, A*STAR, Singapore. Her research interests focus on offshore wind energy, marine propulsion system and design optimization.