Use of Toroidal Thrusters in Small and Medium-sized Ships

The use of B-series and Kaplan-series thrusters is extremely well-established in merchant shipping. In large ships, the thrusters are predominantly serious B thrusters. In the ship design phase, the selection of thrusters makes use of the Kt-Kq-J diagrams (thrust coefficient, torque coefficient and advance coefficient), obtained in called open water tests. In recent years, the use of toroidal-type thrusters has emerged, particularly in drones and some small vessels. These thrusters have a complex geometry, which makes their parameterization difficult. However, some important parameters can be identified such as pitch/diameter ratio, area ratio, rake and number of blades.
In this article, around 20 toroidal thrusters were analyzed. The meshes were generated from a mathematical model that was developed based on a series B thruster mesh generation model, in Python language. The analysis also includes testing in a test tank and CFD (Computational Fluid Dynamics) models. In the CFD, a k-epsilon turbulence model was used, with the intention of approximating the flow conditions of the numerical model and the test in a test tank. In the test tank test, the procedure recommended by the ITTC (International Towing Tank Conference) in the “Open Water Test” Procedure was followed. This resolution establishes the necessary conditions for testing propellants in test tanks, such as tank dimensions, dimensions of the tested propellants and incident flow velocity. Another approach to the work is to compare the performance of toroidal thrusters with similar series B thrusters (same pitch/diameter and area ratio). The Kt-Kq-J diagrams of the toroidal thrusters were obtained from CFD and test tank analysis and the resulting curves were compared. Finally, the article discusses the use of toroidal thrusters on small and medium-sized vessels.