The ultimate propeller/rudder system upgrade for improved efficiency [image] Promas Lite upgrade

A propulsion system upgrade designed for reduced fuel consumption by integrating the design of rudder and propeller systems.

Promas Lite is a version of the successful Rolls-Royce Promas integrated propeller and rudder system, designed specifically as an upgrade for vessels already in service.

The upgrade consists of three main components;

  • a bulb which is attached to the forward edge of the rudder
  • a hubcap which is bolted to the rear of the propeller
  • a set of redesigned propeller blades

Each Promas Lite system is custom engineered to an individual vessel. We model each solution using the extensive in-house CFD (computational fluid dynamics) capabilities at the Rolls-Royce Hydrodynamic Research Centre to ensure that each design is matched to the hull and specified operating profile.

  • Reduced fuel consumption : improvements of up to 20% can be expected depending on the vessel’s operating profile.

  • Reduced environmental impact : corresponding reduction in emissions with lower emission taxes.

  • Short payback period : depends on vessel operating profile, but a payback is typically achieved in less than two years.

  • Simple, robust design : the design doesn’t rely on any complex mechanical features.

  • Simple and quick installation : can be normally fitted during a routine dry-docking.

  • Lower maintenance costs : reduced engine loads means less oil consumption and potentially reduced engine wear.

Promas Lite upgrade on Norwegian Cruise Line vessels Norwegian Sun and Norwegian Spirit

In August 2010, Miami based Norwegian Cruise Line placed an order with Rolls-Royce Marine for a Promas Lite upgrade on their cruise vessel Norwegian Sun. The  upgrade, which involved Norwegian Sun’s twin main propellers, was conducted during a regular dry docking in January 2011.

The existing 5.8 meter Rolls-Royce Kamewa controllable pitch propellers were upgraded with new fuel optimized propeller blades, specially designed hub caps and custom fit rudder bulbs. Sea trials were carried out before and after the dry docking and sophisticated onboard shaft torque measurements were used for verification of the efficiency gain.

A lot of time and effort was given by Antoine Gurrey, Norwegian Cruise Line Director, (Fuel Budgeting & Energy Conservation) along with Det Norske Veritas (DNV, retained as an independent third party for final calculations), knowing how critical these results would be for this ship as well as any future projects pursued for other electric propulsion vessels within the Norwegian Cruise Line fleet.

The official findings were presented by DNV at the end of February 2011 and showed an impressive efficiency gain of greater than 10% at the sailing speed range of 17-21 knots. The success of the upgrade on Norwegian Sun led Norwegian Cruise Line to place a follow-on order for their vessel Norwegian Spirit.

Norwegian Spirit was equipped with a pair of four bladed Kamewa mono-block propellers which were replaced with twin Rolls-Royce fixed bolted propellers as part of the Promas Lite upgrade. The 5.8 meter fixed bolted propellers had bronze propeller blades bolted to stainless steel propeller hubs.

Installation took place during Norwegian Spirit’s scheduled dry docking at the end of September 2011. Again the final calculation of efficiency improvement was conducted by DNV and the results this time showed an efficiency gain of 11%.

Following the upgrade of these two vessels, Brian Swensen (Norwegian Cruise Line Senior Vice President, Technical Operations and Refurbishment) said, “The installation of Promas Lite on these two vessels has significantly contributed to our efforts to reduce energy consumption. In addition, it has delivered a reduction of greater than 10% in NOx, SOx, CO2 and other emissions. In combination these improvements support our continuing commitment to Eco-Smart Cruising.”