| dc.description.abstract | Ship propellers can be designed using composite (fibre-reinforced plastic) materials to achieve bending-induced twist deformation leading to automatic pitch adjustment in the blades during operation. Composite tailoring of propellers for improved performance has been around in prototyping since the 1970s and the 2000s in fluid-structure interaction simulations. Such adaptive composite propeller blades showing bend-twist behaviour have recently received increasing interest from hydrodynamic and structural engineers. The key advantages of bend twist propellers are that such propellers might be designed to have higher energy efficiency and emit less noise and vibration than conventional propellers when exposed to periodic loading conditions.
This thesis explored how tailoring the composite layup can achieve blades with desired deformations for periodic loading conditions from a composite engineering perspective. A computational method using Finite Element Analysis and a deformation mode analysis based on foil parameters were employed to explore and quantify how design choices improved the desired adaption while avoiding unwanted deformation modes. The overarching design challenge of this thesis was to counter the periodic variation operating condition of a propeller mounted on a propulsion thruster that is turned for steering the ship. A method to dimension the desired deformation characteristics in the propeller blades was adopted.
During the thesis work, four basic bend-twist design concepts were identified and explored: hollowing the blades, anisotropic surface laminates, internal support structures and freeing the tail of the blades at the root. Then, based on the findings, a blade design that applied all the design concepts to achieve twisting was made, also considering the constituent materials’ strengths.
A method to produce an adaptive composite propeller blade prototype and how to experimentally verify the predicted elastic response in the blade was made. A 600 mm-long hollow full-size blade was built and statically tested in the laboratory. The elastic response of the prototype was measured with digital image correlation and strain gauges. The twist angle agreed within 0.01 degrees of the designed deformation characteristics demonstrating that such propellers can be successfully built and modelled by finite element analysis.
The promising design concepts for adaptive propeller blades were applied to propose a bendtwist design in a typical metal propeller geometry. The design was dimensioned for the investigated periodic load case. It showed a significant amount of twist deformation, indicating that the design would mitigate the undesired effects of operating in periodic load variations. The suggested design also shows a bend-twist efficiency that is four times better than comparable designs in published literature, indicating significant bend-twist improvement. | en_US |
