Mermaid propulsion unit
The Rolls-Royce’ s podded propulsor developed by Kamewa and Alstom and available from 5 to 25MW. The MermaidTM hydrodynamically optimized outboard part is 360 degrees rotatable, or +/- 35 degrees hardover/hardover in transit, by a hydraulically operated steering gear. The synchronous type motor with brushless excitation has stator shrink fit into the pod housing in order to decrease pod diameter and maximize cooling effect from surrounding sea-water. Additional cooling is arranged by circulating air in a completely sealed circuit, with redundant water coolers and fans located in the pod room.
The Kamewa fixed pitch propeller can be either solid or with bolted blades. Mermaids are designed for underwater mounting/dismounting and supported by facilities allowing propeller and shaft sealing system replacement underwater.
The first Mermaid propulsors were installed onboard the 1950 passenger-capacity cruise vessel MILLENNIUM which was delivered by Chantiers de l’Atlantique to Celebrity Cruises.
The propulsion system comprises two Mermaid pod drives with power supplied by low emission gas turbine power plant. Each of the pod propulsors is rated at 19.5 MW and swings a 5.75m-diameter fixed pitch propeller.
The QUEEN MARY 2 has four Rolls Royce Mermaid podded propulsion systems, the first four-podded installation to date and the largest output for any podded-driven vessel. The system comprises two fixed and two azimuthing pod units delivering a combined output of more than 85 MW, which gives the ship a service speed of 30 kts.
See also Electric podded propulsors.