On the working principle of pre-swirl stators and on their application benefit and design targets

Issue title: Main results from the GRIP project

Guest editors: Henk Prins

Article type: Research Article

Authors: Streckwall, Heinrich^{; *} | Xing-Kaeding, Yan

Affiliations: Hamburg Ship Model Basin, Bramfelder Straße 164, D-22305 Hamburg, Germany

Correspondence: [*] Corresponding author. Tel.: +49 (0)40 69 203-335; Fax: +49 (0)40 69 203-345; E-mail: streckwall@hsva.de.

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 KT 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

DOI: 10.3233/ISP-170124

Journal: International Shipbuilding Progress, vol. 63, no. 3-4, pp. 87-107, 2017