Becker Mewis Duct® Introduction

Becker Mewis Duct^® – simply saving power.

Becker Mewis Duct® – Introduction
Becker Mewis Duct® – Concept
Becker Mewis Duct® – Case Study
Becker Mewis Duct® – CO₂ savings

Introduction.

The Becker Mewis Duct® is a power-saving device developed for full-form slower ships that provides either significant fuel savings at a given speed or, alternatively, allows the vessel to travel faster at a given power level.

The Becker Mewis Duct® consists of two strong fixed elements mounted on the vessel: a duct positioned ahead of the propeller together with an integrated fin system within. The duct straightens and accelerates the hull wake into the propeller and also produces a net ahead thrust. The fin system provides a pre-swirl to the ship wake which reduces losses in propeller slipstream, resulting in an increase in propeller thrust at given propulsive power. Both effects contribute to each other.

The achievable power savings from the Becker Mewis Duct® are strongly dependent on propeller thrust loading, from 3% for multi-purpose ships up to 8% for tankers and bulkers. The power savings is virtually independent of ship draught and speed.

The Becker Mewis Duct® is ideally suited to both new-build and retrofit applications (e.g. Tankers, Bulkers and MPCs).

Improved propulsion
Proven fuel savings up to 8%
Reduced greenhouse gases (GHG)
No moving parts, no service necessary
Reduced vibrations & pressure pulses
Return on investment in approx. 1 year
Installation time approx. 4 days

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Energy-Saving Devices:

Becker Mewis Duct^®

Becker Twisted Fin^®

CO₂savings (BMD)

Concept.

High blocked ships have low propulsion efficiency. The reasons for this are the bad wake field and high propeller loading. Water inflow has such an unfavourable characteristic that the propeller must operate in bad inflow conditions. The Mewis Duct® harmonizes and stabilizes the flow and generates a pre-swirl to reduce rotational losses in the propeller slipstream.

The integrated fins have a stator effect by generating a pre-swirl counter to the direction of propeller operation. This generates more thrust. The fins are asymmetrically profiled and arranged to generate a perfectly homogenous flow distribution. Consequent propulsion improvement can only be achieved if several aspects of hydrodynamic performance are taken into account. The combination of the Mewis Duct® and a corresponding Becker Rudder® dramatically increases the efficiency of the system by means of wake field optimisation and less rudder resistance at improved manoeuvring performance.

The Becker bundle: Propulsion optimisation both in front of and behind the propeller.

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Case Study AS Vincentia.

In 2010, Becker Marine Systems was presented the unique opportunity to test the vessel AS Vincentia with and without the Becker Mewis Duct® installed. Both trials took place within five days and under identical conditions.

The AS Vincentia“ is a newly built 57,000 tdw supramax-bulker of the Dolphin class (more than 100 vessels of this ship type are in operation). After the general sea trial without the Becker Mewis Duct® the ship was docked again. Five days later, after the Becker Mewis Duct® was installed, the sea trial was repeated in the same sea area. The draught and trim of both trials were identical. The performance measurements were recorded by MARIN and the final reporting was done by HSVA, where the model test had already been carried out.

The measurements of the sea trial indicated a power saving of 5% at a speed of 14.4 kn. The result confirmed the positive model test results performed after the CFD design phase. This exellent correlation between the CFD, model test and sea trial are proof of the accuracy and technology.

Due to the number of propulsion tests for other vessels made with and without the Becker Mewis Duct® a reputable statistical statement can be formed. The average of fuel saved is at 6%. This also means 6% less emissions of greenhouse gases.

Combined with a Becker Rudder, the propulsion improvement and fuel saving could be further enhanced, with fuel savings of up to 8%. Compared to other types of fuel saving devices and experiences with similar devices this is a very good and positive result.

Other tests with and without a Becker Mewis Duct® with a 158,000 tdw bulk carrier showed a significant reduction in cavitation occurrance at the blade tips of the propeller and a significant reduction of harmonised vibrations up to 80% (almost eliminating them) during a pressure pulse measurement. Furthermore, an enhancement of the course-stability was proven during manoeuvering tests at SSPA with a 43,000 tdw bulk carrier in 2010.

(Pictures by kind permission of the Ahrenkiel Group.)

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