September 24, 2008
Rolls-Royce introduces new waterjet range
Rolls-Royce is introducing a new series of waterjets, the Kamewa S3 range,
The line draws on experience from the popular SII series but incorporates numerous improvements made possible by advanced design calculation methods and testing and production techniques.
Kamewa S3 waterjets offer a significant increase in efficiency. This translates into reduced fuel consumption for a given workload and thus reduced CO2 emissions. At the same time there is a reduction in size, weight and life-cycle costs.
For most applications, an S3 unit one size smaller than its predecessor will give the same performance. The result is a 25% reduction in the weight of the waterjet and its entrained water, together with a 12% smaller transom flange diameter.
If the same frame size as before is specified, the Kamewa S3 offers a higher top speed; alternatively either a larger payload, or less installed power and reduced fuel consumption, while maintaining the original speed.
These advantages for the customer are achieved through a variety of developments.
At the heart of the waterjet is the mixed flow pump located aft of the transom flange.
The impeller of the SII has been significantly improved, in particular its cavitation margin, by using the latest computational fluid dynamics (CFD) techniques combined with extensive testing in the cavitation tunnels at the Rolls-Royce Hydrodynamics Research Center.
Optimizing the whole pump unit and inlet duct gives a gain in propulsive efficiency of 2%-3%, compared with the SII series. An improved bearing design gives ideal running conditions for the shaft seal, reducing wear and tear, and provides close control of the clearance between the impeller and the pump housing, so maintaining high pump efficiency over a long period.
The pump unit, nozzle and steering/reversing bucket are in stainless steel, and with the bucket now of a lighter but robust cast design incorporating an improved feedback system.
Kamewa S3 waterjets can be supplied as a steering and reversing units, or as simpler boosters giving ahead thrust only. This enables the ideal system to be configured for multi-jet installations or combinations of waterjets and CP propellers.
As before, the inlet duct is fabricated by the shipyard to Rolls-Royce drawings and specifications, and the waterjets are optimised for the particular installation, covering a wide variety of vessel types and operating conditions.
A range of frame sizes is being introduced progressively, covering pump diameters from 50 centimeters to 2 meters, and a power range from 2,000 kW for the smallest S3-50 up to 40,000 kW for the largest S3-200, the maximum power rating for very high speed vessels.
Waterjets are supplied with the latest developments in Rolls-Royce control systems, from the human/machine interface to hydraulic cylinders for steering and maneuvering.
The first vessel to use the fully developed Kamewa S3 technology will be a 56 m long fast yacht, the Leopard 56 from the Rodriguez group.
While the Kamewa S3 range covers a wide power band, it is just a part of the overall Rolls-Royce waterjet portfolio. For lower powers customers can specify the FF series of axial flow aluminum jets, and between these and the S3-series come the A-series aluminum units. A new A3 range is under development, and the first frame size A3-56 is now being introduced, incorporating the same mixed flow pump technology as the Kamewa S3 and an integrated bolt-in or weld-in aluminum construction.
At the top end of the power range come the SL-series. These propel several of the largest fast ferries and take Rolls-Royce waterjet capability up to and beyond today's demands.