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Courtesy of Finnlines Oy, photographed by Hannu Laakso.

Combined model tests and CFD calculations have been performed for a series of 6 RoRo vessels on order.

MORE EFFICIENT PROPULSION SOLUTIONS WITH ENERGOPAC Energopac is an optimised propulsion and manoeuvring solution for coastal and seagoing vessels. Its key objective is to reduce a vessel’s fuel consumption by integrating propeller and rudder design. Each Energopac is designed for a particular vessel and to meet your specific requirements; this allows Energopac to be optimised for energy efficiency, without compromising on manoeuvrability or comfort. Combined model tests and CFD calculations have been performed for a series of 6 RoRo vessels on order.

Energopac is a registered trademark.

OPTIMISING ENERGY EFFICIENCY The price of fuel represents the dominant factor in the operational costs of seagoing vessels. Wärtsilä is continuously looking to improve the energy efficiency of its propulsion solutions. A vessel’s energy efficiency is the result of the interaction between all main components. These need to form a single integrated design for optimal performance. This also holds true for the interaction between the vessel’s propeller and rudder. The energy-saving capacity of Energopac is based on this interaction, and in addition the system is customised to meet your requirements. The result is a reduction in fuel consumption of several per cent. This also gives an equal reduction in CO2 emissions. WÄRTSILÄ AND BECKER MARINE SYSTEMS TEAM UP Energopac is the result of co-operation between Wärtsilä’s propulsion specialists and the rudder experts at Becker Marine Systems. The combined experience and track record of these companies in optimising ship

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CFD capabilities within Wärtsilä are state-of-the-art.

Example arrangement of a typical Energopac solution, showing all the main components.

efficiency is significant and widely appreciated in the industry. Combining propulsion expertise with manoeuvring knowhow is the strong point of this co-operation. This makes it now possible to design a sophisticated propulsion and manoeuvring solution that is optimised for energy efficiency. The basis for this high efficiency rudder technology dates back to the 1990s when Wärtsilä started making energy-saving rudders. Since then over 30 vessels have been equipped with the concept, and all of them have proven to be very successful in saving fuel. One example of this is a series of chemical tankers, which has achieved a fuel saving of 5% at 17 knots; another example is a series of general cargo vessels, with a 4% fuel saving at 23 knots. DESIGN PROCESS At Wärtsilä, we design our propulsion solutions to meet your requirements and to tackle your

propulsion problems, utilising readily available experience and modern CFD techniques. The reduction in fuel consumption when applying Energopac depends very much on the vessel type, on the operational profile of the vessel and also on the reference propeller and rudder. So we can give a good estimation of the annual fuel savings potential only after we have examined the vessel design and the alternative propulsion solutions in detail. We will then optimise Energopac for the vessel, and finally present a unique solution to you. Our in-house CFD (computation fluid dynamics) capabilities are state-of-the-art and they are fully utilised during the engineering process. This means we are able to customise the equipment for any vessel, tailored to any operational profile and other requirements, in a fairly short time. ENERGOPAC IN DETAIL Energopac consists of several components which

vary in design and dimensions and are modified to each other and for the vessel: a propeller, a streamlined fairing cap, and a rudder system with a rudder bulb for efficiency. Energopac includes a sophisticated full-spade rudder. Firstly, this provides excellent rudder balance and manoeuvring performance; secondly it allows for a smaller total rudder blade area, which results in lower rudder drag. It also requires only relatively small steering angles to keep the vessel on course when in transit. The patented KSR support system is used to construct a slim rudder profile, resulting in low resistance; The support system also allows the Energopac to be installed on any size of vessel, which is truly unique when it comes to large vessels. The leading edge of the rudder is twisted to align it more closely with the propeller’s slipstream: this results in better water inflow angles and improves the cavitation behaviour of the rudder.

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Rudder resistance (% of propeller thrust)

25% Wärtsilä Energopac

For more details visit or callStandard 0871 8732404 semi-spade rudder 20%




0% -100% -80% -60% -40% -20% 0% 20% 40% 60% Rudder steering force (% of prop. thrust)

80% 100%

Energopac yields a much lower resistance force than a standard rudder, for the same steering force (manoeuvring effort).


Vibration level (amplitude in kPa)


Design configuration


Full scale Energopac Model scale Energopac Improved propeller design Reference design

4 2.9

3 2

2.8 2.7

1.9 1.8

1.8 0.9

1 0.3

0.3 0

1.2 1.1





Vibration frequency (n harmonic of blade passage)

Available CFD was used to visualise the turbulent kinetic energy in the flow, which is a measure for the energy losses. The rudder bulb of Energopac (bottom) shows a significant reduction when compared to a standard rudder (top).

The fairing cap and rudder bulb are specifically designed to reduce the separation losses behind the propeller hub and increase overall efficiency. The propeller design is adapted to the propulsion requirements; however the design is also optimised to both the rudder and the rudder bulb. This means even higher propeller efficiency can be achieved when applying Energopac. WORKING PRINCIPLES Energopac reduces fuel consumption because it effectively reduces flow separation behind the propeller hub. Extended studies show that for the same course-keeping capabilities, Energopac creates less drag than conventional rudder systems. This is illustrated in the graph in the top right corner of this page. Streamlining the flow significantly reduces separation losses from the propeller hub. A comparison of this effect is made in the CFD

Pressure pulse measurements on the ship’s hull reveal a reduction in vibration levels onboard the vessel; on full scale this is even more noticeable.

images above. This is achieved by the efficient design of the rudder bulb, particularly when integrated with the propeller and the rudder profile. The impact is most noticeable when a large part of the rudder bulb is behind the propeller hub. This means that the highest fuel savings are achieved when the vessel is in transit, since the rudder angles required for course-keeping are only minimal. Energopac has proved to be better in fuel saving than a conventional system in course-keeping mode. Especially when using small forces for correction and steering to keep the vessel on course, the difference in rudder resistance is significant. The high-lift performance of Energopac requires smaller steering angles and consequently reduces rudder resistance. MORE DESIGN FREEDOM The application of Energopac gives a vessel’s

designer greater freedom in optimising opposing requirements: It will increase propulsion efficiency and/or it will reduce vibration levels. The effect has been measured and this is illustrated in the bar graph above. A standard propeller-rudder design is compared with an improved design and with Energopac, on both model and full scale. The reduction in pressure pulses, (which is the result of a more homogeneous water inflow into the propeller) results in lower vibration and increased comfort onboard the vessel. High performance propeller designs are often a design compromise between increased efficiency and reduced vibration levels. Energopac allows for a propeller design that optimises these requirements. At Wärtsilä we have the experience to advise our customers on the best solution for their specific combination of requirements.

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SUMMARY OF BENEFITS Here is a list of the most important benefits from applying Energopac. They all add up to significantly reduced fuel consumption, lower „ „ „ „ „ „

Patented rudder support system Streamlined rudder bulb and hub cap design Slim rudder profile design Flap mechanism, reducing steering angles Twisted leading edge rudder profile Propeller design adapted to rudder and bulb

TYPICAL APPLICATIONS FOR ENERGOPAC The Energopac will effectively reduce the operational costs for any vessel with a considerable share of free sailing time in its operational profile. It works very well for propellers with a relatively large propeller hub. The potential savings are largest for vessels with highly loaded controllable pitch propeller systems such as RoRo-vessels, ferries, container / multipurpose vessels and vessels with an ice class notation. Due to the larger propeller hub diameters, the hub losses would be significant for a conventional system. With the application of Energopac these losses can largely be avoided. However for any coastal or ocean-going vessels with considerable transit times, Energopac will show a favourable return on investment. MONEY SAVINGS ON ACCOUNT OF ENERGOPAC The reduction in fuel consumption depends very much on the vessel type, the operational profile of the vessel and also on the reference propeller and rudder. Wärtsilä can estimate the power savings for any application, based on the vessel design, the operational profile and other requirements. Proven savings due to Energopac vary between 2% and 9% in the required power for a vessel’s trial speed. Since the actual reduction in power depends on the propulsion alternatives, the examples below

vibration levels onboard, excellent coursekeeping and superior manoeuvring.

à à à à à à à

Allows for the largest rudder sizes Reduction of propeller hub losses Low rudder resistance Course-keeping with lowest rudder drag Minimised risk of rudder cavitation erosion Highest propeller efficiency Best comfort levels onboard

give the annual savings in fuel costs for each percentage point in power reduction (based on fuel prices in August 2008): Case 1: A 20,000 dwt cargo vessel with an 8000 kW main engine and a CPP installation will benefit greatly from Energopac in terms of power reduction. Depending on the operational profile of the vessel, the annual savings can be up to USD 45,000 for each percentage point reduction in power. Case 2: A RoPax ferry typically has a high power density propulsion system with additional noise requirements. This is an excellent situation to consider the Energopac solution. With an installed power of around 25,000 kW and a twin screw CPP installation, Energopac can reduce power significantly. The fuel cost savings can exceed USD 125,000 a year per percentage point in power reduction. Case 3: Large container vessels sail large distances at relatively high speeds. A vessel with a capacity of more than 5000 TEU usually has 50,000 kW installed on a single fixed pitch propeller. Applying Energopac will save roughly USD 300,000 a year on fuel for each percentage point in power reduction.

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09.2008 / Bock´s Office / Litoset

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Wärtsilä enhances the business of its customers by providing them with complete lifecycle power solutions. When creating better and environmentally compatible technologies, Wärtsilä focuses on the marine and energy markets with products and solutions as well as services. Through innovative products and services, Wärtsilä sets out to be the most valued business partner of all its customers. This is achieved by the dedication of more than 17,000 professionals manning 160 Wärtsilä locations in 70 countries around the world. Wärtsilä is listed on The Nordic Exchange in Helsinki, Finland.

WÄRTSILÄ is a registered trademark. Copyright © 2008 Wärtsilä Corporation.

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Wärtsilä Corporation - Brochure Energopac  

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