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

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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References

Betz, Zur Theorie der Leitapparate für Propeller, Ingenieur-Archiv9(6) (1938), 435–452(also available under ‘The theory of contra-vanes applied to the propeller’ in a NACA Technical Memorandum, No. 909, Sept. 1939). doi:10.1007/BF02083830.

N.E.

Fine and

S.A.

Kinnas, A boundary element method for the analysis of the flow around 3-D cavitating hydrofoils, Journal of Ship Research37(3) (1993).

T.W.F.

Hasselaar and

Xing-Kaering, Evaluation of an energy saving device via validation speed/power trials and full scale CFD investigation – pre-swirl stator evaluation on a bulk carrier, ISP (2015).

Nakamura, Estimation of propeller open-water characteristics based on quasi-continuous method, Journ. of the Soc. of Nav. Arch. of Japan157 (1985).

Streckwall, Description of a Vortex Lattice Method for Propellers in Steady and Non Steady Flow, Hamburgische Schiffbau-Versuchsanstalt GmbH, Report CFD No. 18/97, Hamburg, 1997.

Streckwall, Pre- and postswirl devices in view of their optimum adjustment to the propeller layout, in: XVIII International Conference HYDRONAV 2010, CTO S.A., Gdansk, Poland, 12–13 May 2010, 2010.

Xing-Kaeding,

Streckwall and

Gatchell, ESD design and analysis for a validation bulk carrier, ISP (2015).

G.J.

Zondervan,

T.J.C.

van Terwisgaet al., On the design and analysis of pre-swirl stators for single and twin screw ships, in: SMP11, 2nd Intern. Symp. on Marine Propulsors, Hamburg, Germany, June 2011, 2011.