Rocks & mirror
Encyclopedia of Marine and Energy Technology



Wärtsilä and Becker Marine Systems jointly developed the Energopac system. With both the propeller and rudder design integrated, each Energopac is entirely optimized for propulsive efficiency whilst not giving in on either manoeuvrability or comfort level. It consists of several components which vary in design and dimensions, adapted to the vessel: there is a propeller installation, a streamlined fairing cap and a rudder system with an efficiency bulb.

The rudder of the Energopac comes with a full spade blade and a flap mechanism. This provides excellent rudder balance and manoeuvring capabilities in the first place; secondly this allows for a smaller rudder area, resulting in lower rudder drag. The patented support system is used to design very slim rudder blades, also meaning low rudder drag; it also enables delivering any size of Energopac system to any size of vessel. The leading edge of the rudder is twisted and subsequently more aligned with the propeller slipstream, resulting in better inflow angles and improved cavitation behaviour of the rudder. The propeller is designed by Wärtsilä for high efficiency and is part of the Energopac solution. The fairing cap and efficiency bulb are specifically shaped to reduce the separation losses behind the propeller hub and increase total efficiency. The bulb has another effect; its bulbous shape reduces the water velocity through the propeller plane. Consequently the average wake fraction of the vessel is increased and thus also the hull efficiency goes up. The fairing cap is attached to the propeller hub; the efficiency bulb is fixed to the rudder blade.

Reduction on fuel consumption depends on the type of vessel and its operational profile. The performance improvements determined through computational fluid dynamics (CFD) calculations and/or model tests indicate power reduction values ranging from a minimum of 2% to a maximum of 9%. Recent trials of 17,700dwt vessels carried out in cooperation with the Spliethoff Group has shown that the Energopac saves nearly 4% power in design condition.