Pre-Swirl Stator and Propeller Design for Varying Operating Conditions

Over the last two decades, an increasing number of studies have been conducted to develop and improve energy saving devices (ESDs) in order to increase the propulsive efficiency. One well-known example is the pre-swirl stator (PSS), which consists of an often asymmetric arrangement of fixed stator blades ahead of the propeller. This paper describes the hydrodynamic design of a pre-swirl stator with radially variable pitch, paired with a conventional propeller. The aim is to achieve the highest possible efficiency in various operating conditions, and to avoid efficiency penalties in off-design operation. To investigate the propeller and stator designs and configurations in different operating conditions, the computationally inexpensive vortex-lattice method is used as a first step to optimize the geometry in an initial parameter study. Then the flow over hull, stator and propeller is simulated in a CFD-based approach to confirm the results obtained in the first stage.