Adaptive pitch control of full-scale ship composite propeller using shape memory alloy to enhance propulsive efficiency in off-design conditions

Abstract

In this study, we investigate the use of shape memory alloy for adaptive control of twist of the propeller blade for a full-scale marine composite propeller of actual blade geometry, to offset the reduction in its hydrodynamic efficiency in off-design conditions. A full-scale ship propeller of 4.2 m diameter, made of graphite–epoxy laminate integrated with Nitinol fibre–reinforced hybrid composite (shape memory alloy hybrid composite) patches, is considered. The shape memory alloy hybrid composite patches are placed such that the recovery stress induced on heating the pre-strained shape memory alloy fibres embedded in martensite phase to the austenite phase causes twisting deformation in the propeller blade. The open water performance is estimated from the flow solution obtained using the finite volume method considering viscous flow and fluid structure interaction, while the deformation analysis is performed using the finite element method based on the first-order shear deformation theory, considering the nonlinearity due to large deformation. It is shown for the first time for a ship propeller of actual size and shape that the heating of the shape memory alloy fibres generates sufficient twist in the propeller to cause appreciable improvement (up to 6.3%) in its hydrodynamic efficiency in off-design conditions with lower advance ratios, thereby enhancing its fuel efficiency.