A RATIONAL APPROACH TO THE DESIGN OF PROPELLER/STATOR COMBINATION

This study describes a detailed procedure for design of marine screw propeller in combination with a "retrofit" stator device, also known as fixed guide vane or pre/post swirl device, based on lifting line theory. The design procedure involves more realisticrepresentation of the propeller slipstream which is contracted form of helical vortices. The slipstream shape is allowed to deform and to align with the direction of local velocity which is the sum of the inflow wake velocity and induced velocity. As the slipstream deformation is the key parameter in the design of reaction type of performance improvement devices, the design methodology is applied to a stator device behind the propeller as a retrofit. The hydrodynamic performance of the combined propulsor is analysed in terms of effect of variation of the axial distance between the propeller and stator and the number of stator blades. Design studies for a torpedo unit, a SWATH vessel and a conventional ship are carried out to demonstrate the effect of the slipstream contraction as well as the efficiency gain by the systematic variation of the main design parameters of the propulsor system. Furthermore a qualitative correlation of the procedure based on limited experimental data available in the literature is presented.