Large Area Propellers

Paper in proceeding, 2011

The high cost of fuel and the demanding regulations against the environmental impact of using fossil fuels are now encouraging new and more radical solutions when it comes to the propulsion systems of a ship. One possible way is to move the propeller aft behind the hull. This allows the propeller diameter to increase without risks of pressure pulses being transferred to the hull. An increase in efficiency may then be achieved, reducing environmental impacts and cost. This is referred to as the large area propeller (LAP) concept and is investigated in this paper. The CFD software SHIPFLOW with a zonal approach (RANS, potential flow and boundary layer methods) is used, and the propeller is represented by a lifting line method. The original propeller and a larger one are systematically moved aft, and the delivered power, as well as the propulsive coefficients, are computed. Results are compared with experimental data from SSPA. The results indicate a large reduction in delivered power both in CFD and EFD by moving the propeller aft and increasing the diameter by 22.7%. Compared to the original configuration, the reduction is around 10% in EFD and 14% in CFD; however, the trends are well captured in CFD. There is thus a large gain in total efficiency mainly due to increased hull and propeller efficiencies, even though no modifications of the hull and propellers were done to further improve the concept. By optimizing these, it could be possible to improve the concept even further.