Evaluation of a Dynamic Positioning Thruster Performance Characteristics with and without a Nozzle

In an effort to provide experimental data on the performance of Dynamic Positioning (DP) thrusters, compares between the performance characteristics of open and ducted thruster and to investigate the contribution of duct to the performance of ducted DP thrusters under variable operating conditions, a series of experiments were performed on a DP thruster model, at the Institute for Ocean Technology (IOT) National Research Council of Canada (NRC), towing tank and at the Italian Ship Model Basin (INSEAN) large cavitation tunnel. The DP thruster performance characteristics were investigated at different propeller speeds, with and without a nozzle, and over a range of advance coefficient values including the bollard pull condition at the IOT towing tank. Detailed wake measurements test to the DP thruster model at a plane very close to the propeller blades were performed at INSEAN large cavitation tunnel, with and without a nozzle and at bollard pull and near bollard pull operating conditions using a Stereoscopic Particle Image Velocimetry (SPIV) system. The results of these tests provide insight information about the performance characteristics of the DP thruster at different loading conditions and its effects in the DP thruster wake hydrodynamic characteristics. The contribution of the duct thrust to the whole performance of the ducted DP thruster under variety of loading conditions were investigated and presented. This paper shows the advantages of using ducted thrusters at high loading operating conditions, and presents the change in duct thrust contribution as a function of thruster loading. Also, a comparison between the performance and wake hydrodynamic characteristics of ducted and open thruster is evaluated and discussed under varied high loading conditions.