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Propeller related measures

Propeller optimisation

The propeller of a ship can be optimised in order to reach a hydrodynamic design. By minimising the number of blades, the blade area is reduced, resulting in less resistance, but the reduction potential is mainly related to the diameter size and the amount of revolutions per minute (RPM). With a large propeller rotating at a low speed, high propeller efficiency can be reached. Propellers with a large diameter are mainly suited for deep-draught ships. An optimal design of a propeller can be limited by factors like the possibilities of enlarging the diameter and loading.

Propeller upgrade

To reach the above described propeller optimisation a new propeller has to be installed. In case this is not possible there are several ways to upgrade a propeller to optimise conditions and reduce emissions. Examples of propeller upgrades, mostly in the form of devices to be installed, are summarised in Table 1. A full description per measure can be found here – A and B.

Losses of propeller energy can be avoided by recovering the rotational energy in the flow from the propeller or by making use of pre-rotation of in the inflow before it enters the propeller. The reduction potential on average is between 5 and 10% of total ship propulsion power.

Table 1 Overview of examples of propeller upgrades

MeasureApplicabilityReduction potentialPayback timeCosts
Change of rudder profile and propellerTanker, container, RoRo2-6%Medium
Upgrading the tip of the propellerTankers0.5-3%Medium
Propeller boss cap with finsAll ship types1-3%Investment costs between USD 20,000 and USD 146,000
Optimisation of propeller bladesAll ship types< 2%Very short10-15% higher propeller costs
Contra-rotating propellersSingle-screw ships (very fast RoRo vessels or ice breakers)

3-6%Investments costs, but unknown
Free rotating vane wheel/Grim wheelCargo ships10%
Ducted propellerTankers, bulk carriers, tugs, offshore supply and service vessels5-20% (average 10%)
Pre-swirl devicesAll single-screw ships1-9%
Post-swirl devicesAll new ships1-9%
Integrated propeller and rudder unitsCargo vessels, RoPax vessels and container vessels operating at relatively high speed
Wing thrustersRoRo and ferries< 10%MediumInvestment costs, but unknown
Pulling thrustersRoRo and ferries< 10%MediumInvestment costs only (unknown)

Source: 2009 IMO Second IMO GHG Study 2009 (pages 171-173)

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