Design and Testing of a Hybrid Shaft-Pod Propulsor for a High Speed Sealift Ship

Abstract

The hybrid shaft-pod contra-rotating propulsor configuration has been demonstrated to offer increased efficiency and maneuvering performance over conventional propulsor configurations. The design and testing of this propulsor concept for a large 39 knot high speed sealift application is described here and compared with the performance of a baseline shaft and strut mounted propulsor. This hybrid contra-rotating configuration uses twin tractor propulsion pods to power the aft propellers of the contra-rotating set, where the forward propellers are powered by conventional shaft lines. The design process used a number of design and analysis tools to develop a propulsor intended to operate at 39 knots while avoiding thrust breakdown. The propulsor geometry was manufactured and tested in open water at two different scales and used in powering and cavitation tests. Software predictions against the open water data demonstrated that performance predictions can accurately be made for this type of propulsor. The absence of thrust breakdown at speeds above the 39 knot design speed was demonstrated. The powering performance of the hybrid pod configuration will be discussed relative to experimental data obtained for a conventional shaft and strut design for the same hull form.