Tip-Driven Marine Propellers and Impellers-A Novel Propulsion Concept

Contemporary propulsors in tubes (waterjets, nozzles, side thrusters) are relatively cumbersome and definitely stem from simpler unshrouded installations. For shrouded installations, tip-driving is almost a natural solution. Although a novel concept, Mechanical Tip-Driven Propulsor (MTDP) is technically and economically feasible. Some noteworthy features of tip-driven propulsors are compact design, possibly higher efficiency, shrouded propeller, contra-rotation in the nozzle for steerable installations, etc. The TDP operates under undisturbed hydrodynamic conditions resulting in higher efficiency. The complete propeller disc is exploited for propulsion since the propeller shaft, the boss, the thrust column, etc. do not exist. Anticipated problems are sealing of the circular chamber and the gearbox. It is expected, however, that the gain in efficiency is to be larger than are the sealing frictional losses. A number of possible applications of TD concept in marine vessels are given, as for example contra-rotating lip-driven rudder-propeller, lip-driven waterjet, etc.