Experimental Study Of L Type Podded Propulsor In Open Water Conditions

Since the 21^st century, the environmental awareness is growing in most industries including the marine. The standards concerning the energy consumption control have been enhanced with the establishment of EEDI. As an outstanding representative among all the electric propulsions,the podded propulsor has not only a good hydrodynamic performance, but also the better efficiency in propulsion, fuel consumption and energy saving. At present, it has been widely used in luxury passenger liners, icebreakers, ferries etc., and will have more types and more functions in the near future with the updating and development. L-type podded propulsor-Azipod CO series pod has gained its population from many clients in the recent years, but in the meanwhile, related researches and experiments have been seldom seen especially in China. This paper, under such a background of shortage of related researches and facility in China, has taken the preliminary study on the open-water performance of the L-type podded propulsor based on the self-developed experiment facility by combining the PIV measurement technique and CFD method.In this study,a corresponding open-water hydrodynamic performance test device for one specific L-type podded propulsor has been designed.The thrust force and the torque of the propeller,the push force and the lateral force of the podded propulsor unit, together with the plane steering torque, all have been measured respectively in the direct, azimuthing and dynamic azimuthing conditions of the podded propulsor. At the same time, the flow field characteristics of three sections-the back of blade, side of strut and behind the pod has been analyzed by the methods of PIV and CFD.As for the test, the test plan corresponding to the podded propulsor has been designed based on both taking fully consideration of the ITTC’s recommendations and specific condition of the Towing Tank in HEU. Some issues concerning the test which should be paid attentions to have been briefly introduced in the paper. In various advance coefficient of test, emphasis has been put on the comparison on the propeller’s thrust,global load,the unit’s global push force,lateral force and steering torque and other types of the hydrodynamic performance between the normal condition, azimuthing conditions with small or large angles so as to find the general characteristic at changing forward angles. The azimuthing speed and the direction are another two important factors that have been discussed in the analysis. As for the flow field, by combining the PIV accurate measurement technique and CFD method, the flow field’s characteristic at stright,azimuthing and other non-design conditions has been analyzed. In addition, as a more straight way to show the global performance of the podded propulsor, another comparison has been carried out among the specific regional flow fields, including the flows behind the propeller, beside the strut,and also the tail flow field behind podded propulsor unit.