COMPIT 2010 in Gubbio - TUHH

Optimisation of Single and Multi-Component Propulsors
Markus Druckenbrod, Jochen Hundemer, Moustafa Abdel-Maksoud, TU Hamburg-Harburg,
Hamburg/Germany, m.abdel-maksoud@tu-harburg.de
Max Steden, Howaldtswerke-Deutsche Werft GmbH (HDW), Kiel/Germany
Abstract
The paper describes the optimisation of a conventional propeller and a multi-component propulsor.
The last one can be used to satisfy high acoustic requirements. Both propulsors are optimised
concerning efficiency and cavitation behaviour for a ship with a given resistance at a ship speed of 20
knots. As thrust-fluctuations of a single blade can cause vibration and acoustic emissions, the
optimisation criteria is extended to include the minimisation of the amplitude of the unsteady blade
thrust force during one revolution in the investigated wake field.
1. Introduction
Modern ships require efficient propulsors with low sensitivity to cavitation within their operation
range. Up to a certain ship speed the mostly used propulsor is the conventional propeller which
reaches high efficiencies, but encounters cavitation problems at high speeds. One of the most common
propulsors for high ship speeds is the waterjet, with good performance characteristics at high speeds
on the one hand but with a significantly decreasing efficiency at low velocities on the other hand. Kim
(2006) shows typical propulsive efficiencies of the mentioned propulsors and also of super-cavitating
and surface-piercing propellers. The latter two propulsors are not treated here, as they are just feasible
for small ships.
Between the operational speed ranges of conventional propellers and waterjet propulsors there is a
field, where multi-component-propulsors appear to be advantageous. Such a propulsor, sometimes
also called pumpjet or linearjet, is called multi-component-propulsor in the present study. It consists
of the four components, Figs.1 and 2: rotor, hub, duct and stator.
Fig.1: Five-bladed multi-component propulsor
Fig.2: Seven-bladed multi-component propulsor
In a certain way, a multi-component-propulsor can be treated as a combination of a conventional
propeller and a waterjet. The water passes through the propulsor without being lifted to a higher level
as in the case of the waterjet. Therefore the theoretically attainable efficiency of a multi-component-
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