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Abstract

Background:

In an early design stage of ship and propeller or in a propeller retrofit case one may consider a pre-swirl stator (PSS) to recover rotational energy.

Objectives:

A model for the working principle of a PSS was to be developed and then to be applied for power saving estimates. This model should also support the PSS design procedure.

Methods:

The PSS ‘working principle model’ is based on a very fundamental quantity related to a propellers characteristic, namely the circulation distribution. An extended model addresses hub vortex contraction losses. In specific cases a BEM (Boundary Element Method) based propeller analysis is performed. To confirm actual PSS designs, a RANS/BEM coupling method is invoked.

Results:

Global parameters as $K_{T}$ and CTH rule the rotational losses of a propeller and determine the energy recovery potential of a PSS accordingly. The potential of a PSS is considerably enlarged, if it works properly against the hub vortex. Estimates for realistic power savings due to a PSS installation are 4–5% when the hub vortex suppression is included.

Conclusions:

The simple PSS ‘working principle model’ delivers very reasonable predictions. RANS results and available full scale trial measurements can be reproduced using this approach.

Keywords

Energy saving device propulsion retrofit propeller hub vortex propeller rotational losses

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