Multi-objective optimization of cycloidal blade-controlled propeller: An experimental approach

In recent years, innovative naval propulsion systems have been investigated thanks to the growing development of unmanned underwater vehicles. Cycloidal propellers are promising alternative concepts to the usual screw propellers. As bio-inspired technology, these systems use mechanical energy from unsteady hydrodynamic forces generated by blades oscillation like natural marine animal swimmers. As an academic platform, the French Naval Academy Research Institute developed a large-scale experimental cycloidal propeller with the aim of running various pitch motions to evaluate performances of cross-flow propellers. Blades’ pitching is here performed by servo-motors in order to control each blade independently. While common cycloidal propellers use mechanical blade actuators which restrain the blade motion possibilities, this blade-controlled platform allows new investigations of interesting research area in marine propulsion. The platform is widely instrumented with load and torque sensors to measure instantaneous hydrodynamic forces during the rotation of the blades. Experiments, performed in a current flume tank, first reveal that for classical sinusoidal pitch laws, performances are depending on the operating point: the higher the advance parameter, the lower the sinusoidal amplitude must be for a better efficiency. These results confirm the requirement of an adaptable pitch control for cycloidal propeller to improve their performances regarding the operation mode. To go further, an experimental optimization, based on surrogate models (Efficient Global Optimization), is undertaken to surpass the performance of the propeller with parameterized pitch laws. This method authorizes a wide range of possible motion taking account of the platform speed limits. Multi-objective optimization is performed for total thrust and efficiency maximizing for two operating points. Results on the Pareto fronts show that a trade-off is necessary between thrust and efficiency concerning. However, optimized pitching laws reveal high hydrodynamic performances, with gains respectively from 10% to 20% on the hydrodynamic efficiency and the thrust in comparison with classic sinusoidal laws. This confirms the benefit of full electrical blade-controlled propeller and promises interesting further investigations on the experimental optimization. •Improving performances of cycloidal propeller.•Electrical Blade-controlled platform.•Multi-objective experimental optimization with gaussian pr