Feature 1 | CRUISESHIP TECHNOLOGY
Significant modifications were made
to hydrodynamic aspects of the podded propulsors installed onboard Celebrity Solstice. Pod redesign work done on this project has contributed to the development of ABB’s ‘next generation’ Azipod, which is due to be fully available in 2009. Tomi Veikonheimo, ABB lead engineer
hydrodynamics, said that there had been substantial cooperation between shipbuilder Meyer Werft and ABB to optimise pod geometry. Te profile of the strut has been changed to enhance drag performance, following CFD analysis, with the same section profile having been used in the modified fin section. Again, the aſter cone of the torpedo was redesigned to smooth flow separation. Azipod propulsion units to the same
design are being installed onboard the 360m long Oasis of the Seas and Allure of the Seas, Royal Caribbean’s International’s ‘Genesis’ project ships. In this case, and in an industry first, three azimuthing pods will be installed, where larger cruiseships to date have tended to feature two steerable pods and one fixed pod. Each pod will have a power rating of 20MW, and the fact that these ships will be 47m wide means that optimal positioning of the Azipod units can been assured, Mr Veikonheimo said, with the central unit being placed behind the centre line skeg. He added that model testing carried out at Marin in Te Netherlands had confirmed that the configuration would confer new levels of manoeuvrability. Also noteworthy is the fact that the pods
installed on Celebrity Solstice, and indeed Oasis of the Seas and Allure of the Seas, will feature five-bladed propellers, confirming a growing trend among cruiseship operators first witnessed in the case of Radiance of the Seas a decade ago. Mr Veikonheimo said that the
five-bladed configuration had become essential to meet modern cruiseship performance standards, where noise and vibration limit requirements in the aſt part of the ship, where huge theatres tend to be situated, dictate lower propeller excitations. Operating at 135revs/min, the inclusion of an extra blade did not lead to any loss in efficiency, he said, because, to achieve low noise and vibration using a four bladed propeller, it was necessary to work
38 ABB Azipod unit leaves ABB premises.
with extremely low loads at the propeller tip, which had severe consequences for efficiency. Te same noise and vibration performance could be achieved with a five bladed propeller with higher loads at the propeller tip, compensating for the increased blade area.
Celebrity Cruises vice president of
technical operation, Angelos Kokosoulis said: “Tese are the types of propellers first developed for submarines to achieve low noise, and it looks like it works – there is no cavitation to be transferred to the ship.” Captain Skylogiannis said that a
The Naval Architect February 2009 The first of class, state of the art cruiseship, Celebrity Solstice.
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