| Abstract | The paper presents preliminary results of an experimental study on the effect of gap distance on propulsive characteristics of puller podded propulsors in straight course and static azimuthing open water conditions. The gap distance is the axial distance between the rotating (propeller) and stationary (pod) part of a podded propulsor. The propeller thrust and torque, unit forces and moments in the threecoordinate directions of a podded unit were measured using a custom designed pod dynamometer in puller configurations with varied operating conditions. The model propulsor was tested at the gap distances of 0.3%, 1% and 2% of propeller diameter for a range of advance coefficients combined with the range of static azimuthing angles from +20° to -20° in a 10° increment. The results show that the gap distance does not have significant effect on propeller torque in straight course conditions, but has effects in azimuthing conditions. The propeller thrust and efficiency were influenced by the change of gap distance and the effects were more obvious at high azimuthing angles and high advance coefficient values. The unit thrust and efficiency, transverse and vertical forces, as well as moments in three coordinate directions were not influenced by the gap distance, taking into account the uncertainty in the measurements, both in straight course and azimuthing conditions. |
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