While still in its testing phase, we may well see this new design on dynamic positioning vessels.

F/V Jette Kristine gained 23.5% more bollard pull

The propeller designers and PrimeServ staff at MAN Diesel Frederikshavn, Denmark could sit back satisfied on 12 October when a full-scale bollard-pull test on the Esbjerg-based fishing vessel ‘Jette Kristine’, showed an increase in bollard-pull performance of an impressive 23.5%.

The test thus verified a great propulsion upgrade advantage in relation to a „pre-test performed two weeks earlier based on the same vessel, exactly the same engine output and the original propeller and nozzle installation.

The preconditions for the test were the exact same position in Frederikshavn’s harbour basin, same water depth below keel, same draft and trim of the vessel – ensuring the realistic and best possible conditions for relative and comparative bollard pull recordings.

The two bollard pull tests of Jette Kristine gave the following results:
Measured before: 19.1 metric tonnes
Measured after: 23.6 metric tonnes
Corresponding to an increase of: 23.5%

General potential for greater efficiency
Propellers designed more than 10 years ago normally offer great improvement potential in retrofit projects, where fuel consumption reductions of up to 12.5% for free running propeller upgrades have been reported – simply by exchanging the existing propeller blades to today‟s optimised and advanced designs.

A relatively small investment with short payback time and radical impact on the ships future operational economy, fuel consumption and exhaust gas emissions. The green impact and environmental benefit of lower consumption is not to be neglected.

In this case with Jette Kristine and in similar cases with other fishing trawlers, offshore vessels, tugs and dredgers – bollard pull is the key performance parameter. MAN Diesel’s upgrade solutions can include bollard pull optimised propeller blades alone – or bollard pull optimised blades in connection with a propeller nozzle upgrade.

Optimised propeller blade profiles applied together with the newly designed high- efficient AHT (Alpha High Thrust) nozzle is the ultimate solution.

Optimising for bollard pull
Advanced CFD tools (Computated Fluid Dynamics) were used to develop MAN Diesel’s new AHT propeller nozzle series. The nozzle shows superior performance compared to the standard 19A propeller nozzles, which are common standard in the marine industry today.

The increased bollard pull achieved when using the AHT nozzle is not only a result of the optimised nozzle profile, which is double-curved on both the inner and outer diameter. Other contributing factors are the nozzle length/diameter ratio, nozzle support, aft ship lines, and tilting and azimuthing of the nozzle, among others.

The addressing of all these topics has been refined by MAN Diesel into a new systematic method, whereby the bollard pull can be increased by more than 12% compared to solutions with 19A nozzles. The achievements have been demonstrated both in various model tests and in full scale.