To-date, the rim drive concept has mainly been applied to thrusters, but main propulsor applications also exist, such as on this ferry
driven propulsion. For most propulsion arrangements, thrust is produced through the rotational motion of blades, achieved through the use of a propeller (open or ducted) or pump jet propulsor (for submarines). In either case the blades are driven by a motor, located in the hub or via a shaſt. In a rim driven propulsion arrangement,
is constrained by the diameter of the hull. Te result is high material stresses in the gearing, leading to high manufacturing and maintenance costs as well as reduced reliability. It is thought that current reduction gearings are reaching their material limits. If future requirements
include further reductions in shaſt rpm (lower TPK) then these issues will only become more apparent.
Future propulsion One technology that has been identified as a potential for use on future SSNs is rim
the outer duct and blades themselves form part of an electric motor. The stator of this motor is located in the duct and the rotor is a band that encompasses what are traditionally the blade tips. Tis rotor band is usually recessed into the duct. Te blades are rotated from their outer edge as opposed to from a central hub, hence the name ‘rim driven’. In this way, the blade tips become the blade roots and vice versa, there is no longer any tip clearance and a hub is no longer mechanically required (but may still be included for flow alteration or structural support purposes).
RINA - Lloyd’s Register Maritime Safety Award
The safety of the seafarer and protection of the maritime environment begins with good design, followed by sound construction and effi cient operation. Naval architects and engineers involved in the design, construction and operation of maritime vessels and structures can make a signifi cant contribution to safety and the Royal Institution of Naval Architects, with the support of Lloyds Register, wishes to recognise the achievement of engineers in improving safety at sea and the protection of the maritime environment. Such recognition serves to raise awareness and promote further improvements.
The Maritime Safety Award is presented annually to an individual, company or organisation that in the opinion of the Institution and Lloyd’s Register, is judged to have made an outstanding contribution to the improvement of maritime safety or the protection of the maritime environment. Such contribution may have been made by a specifi c activity or over a period of time. Individuals may not nominate themselves. Nominations are now invited for the 2014 Maritime Safety Award.
Nominations of up to 750 words should describe the nominee’s contribution to: • safety of life or protection of the marine environment, through novel or improved design, construction or operational procedures of ships or maritime structures
• the advancement of maritime safety through management, regulation, legislation or development of standards, codes of practice or guidance
• research, learned papers or publications in the fi eld of maritime safety • education, teaching or training in maritime safety issues
The closing date for nominations is 31 Dec 2014. The Award will be announced at the Institution’s 2015 Annual Dinner.
Nominations may be made by any member of the global maritime community and should be forwarded online at
www.rina.org.uk/ MaritimeSafetyAward or by email to
MaritimeSafetyAward@rina.org.uk
Queries about the Award should be forwarded to the Chief Executive at
hq@rina.org.uk
Warship Technology October 2014 17
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