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Sunday, October 22, 2017

Voith Announces First Linear Jet Order

February 28, 2012

A new propulsor for 20 to 40 knots with the simplicity and efficiency of a propeller.

Voith has announced the first Voith Linear Jet order with Turbine Transfers UK for a 19 meter BMT Nigel Gee designed Wind Support Vessel. The Voith Linear Jet will provide for this application a substantial higher bollard pull without a requirement for increased installed power. This higher bollard pull will allow Turbine Transfers the safe transfer of personnel up to higher seastates. Turbine Transfers - a wholly owned subsidiary of Holyhead Towing Company - currently operates a fleet of over 20 fast catamarans that transport personnel and equipment to and from offshore wind turbines. Its long term customers include Siemens, RWE npower, Van Oord, Dong Energy, EnBW and Royal Boskalis Westminster.

The Voith Linear Jet (VLJ), a new ship propulsor, will give Naval Architects new ways to optimise their vessel designs. The VLJ employs the simplicity and efficiency of a conventional propeller installation, yet delivers the possibility to design for 40 knot top speeds without the shake, rattle and roll of an extreme power-dense propeller. Similar to a propeller, the efficiency is at a constant high level relative to the ship speed. This gives a VLJ equipped ship a considerable range advantage against its waterjet sister vessel. Typical VLJ applications will be any ship with a mixed operating profile between low speed cruising and sprint speeds like Navy and Coastguard vessels and Yachts. Ferries operating at Voith Turbo sustained speeds around 30 knots employing high-speed or medium speed Diesel or LNG engines will also benefit of this new propulsion option.

The Voith Linear Jet takes away some of the disadvantages of traditional waterjets, without compromising the vessel’s top and sprint speed ability. The considerable higher efficiency at low-end cruising speeds will provide a positive design spiral for light weight craft. Smaller fuel tanks for the same range, reduce vessel displacement resulting in increased hull efficiency with ensuing increased range and top speed. The low sensitivity for marine growth and the low installation complexity provides lower maintenance costs and high availability. With the VLJ now it is possible to safely replace the conventional propeller for high speed applications, delaying the necessity to switch to waterjets until the required ship design speeds are well above 40 knots.



The successful hull integration of any propulsor is of prime importance for a Naval Architect when issuing a speed guarantee to his customers. Hull interaction effects between propulsor and hull are difficult to predict, with issues like cavitation further complicating a reliable prediction. Assisting the Naval Architect with making the performance predictions, Voith has developed a powerful “Numerical Towing Tank” in Computational Fluid Dynamics (CFD) optimised for the performance prediction of the Voith Linear Jet in any hull form. The VLJ Numerical Towing Tank is validated with several hull forms, with cavitation tunnel tests at tank test institutes and with VLJ self propelled hulls. For any customer specific project the VLJ Numerical Towing Tank generates a full report including cavitation inception at various operating conditions, including hull sinkage and trim influences and also performance analysis for the various possible VLJ hull positions, integration depths and shaft angles. The aim is to assist the Naval Architect in optimising the vessel and to jointly pursue success for every project.

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