Propeller conversions bring greater efficiencies and lower emissions

By Keith Henderson at June 07, 2011 02:54
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Rolls-Royce’s Promas integrated propeller and rudder system claims to offer gains in propulsive efficiency of between five to fifteen per cent for new builds and retrofits. The resulting benefit in practice depends on a number of factors, so each vessel needs to be considered on its merits however in most cases the payback period lies between 18 to 24 months.. Improvements can be made to FPP and CPP systems with single and multiple propellers. The largest gains in efficiency occurs where the operating profile of the vessel has changed, rendering the original propeller specification invalid, or if the propeller was designed without the benefits of CFD methods.

Promas Lite is the name given to a version of the Rolls-Royce Promas integrated propeller and rudder system that can be fitted to vessels already in service to improve their efficiency.

A special hubcap is fitted to the propeller, which streamlines the flow onto a Costa bulb that is welded to the existing rudder, effectively reducing flow separation immediately after the propeller. The result is an increase in propeller thrust as previously wasted energy is recovered from the flow.

A Promas Lite system can be installed during a scheduled drydocking and can normally be fitted within a week.. Promas adapted propeller blades, can be installed if the propeller is a Kamewa CPP or FPP unit. If it is a monoblock propeller, it can be replaced with a propeller of an improved design.

In addition to the financial benefits, improved propulsive efficiency delivers reduced exhaust emissions, therefore upgrading will also have a positive impact on the vessel's environmental footprint.

Caption: The picture shows a recent Promas upgrade of a twin-screw RoPax vessel
with semi-spade rudder and controllable pitch propellers (CPP).

Image credit: Rolls-Royce plc

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