Vericor - High Speed Naval Propulsion Package Solutions

Date: Issue 74 - May 2017

Today’s high speed marine platforms need power to execute their missions, plenty of power. And there is not always a lot of space on these ships for powerful machinery.  The twin gas turbine package that is offered by Vericor Power Systems is a popular solution and one that is being offered to shipbuilders in Turkey for programs here and in foreign markets.  

The TF Series marine gas turbines built by Vericor are in the 4000 kW class and have been used in a variety of fast and high performance ships and craft around the world.  Two of the most prominent applications are the US Navy Landing Craft Air Cushion (LCAC) and the Swedish Navy Visby class corvette.  (Figures 1 and 2)

Gas turbines are much smaller and lighter than traditional diesel engines of the same power and often have much longer operating lives.  Yet they use the same marine diesel fuel.

One of the most unique advantages of the Vericor marine gas turbines is the ability to mount the engines directly to the main reduction gear (MRG) without any other support structure.  This design feature has two very important effects.  It contributes significantly to the weight savings of the overall package by eliminating a heavy base frame or structure for the engine.   It also eliminates any relative motion between the gas turbine and the main reduction gear.  The gas turbines and gear box are essentially a “single machine” which can withstand the “g” loads of high speed marine service.

In the twin marine gas turbine package, this is particularly advantageous as the power of two engines can be delivered the ship drive shaft.   The Twin TF Package as it is known consists of two Vericor TF Series marine gas turbines coupled to a twin in / single out main reduction gear. This propulsion package delivers 8,000 kW or more  shaft power to the propeller or waterjet.  

As a comparison, this powerplant weighs about three times less than the diesel engine equivalent and is less than half the length.  For this reason, designers seriously considering options for high performance ships regularly investigate this kind of powerplant. This light power-to-weight package has allowed designers and builder to meet speed requirements fast ferries, naval ships and mega yachts. 

The entire line of TF series marine gas turbines were designed specifically to be fully mounted to an MRG without further support for sea going applications.  The ability to withstand heavy sea states has been proven not only on the Visby class corvette but also on some of the fastest open water mega yachts operating today.  Yachts of this type are capable of 50 kts speeds which can transmit tremendous force to the installed equipment.   Other gas turbines simply cannot be mounted in this way, needing instead the heavy base frames and skids.  Saving weight is critical in the high speed game, that why gas turbines are employed in the first place. 

There is also the added flexibility of single or twin engine gas turbine operation. The package can be operated on one or both gas turbines with ability to drop one engine off line and/or add an engine while the other engine is operating through the use of synchronizing clutches.  This provides redundancy, a notable safety factor but also increases overall efficiency of the powerplant at low speeds.

Diesels can also be added for a Combined Diesel or Gas Turbine (CODOG) package. While gas turbines can be operated throughout their power range, it can be very economical to add a small diesel to the package to be used for the lowest power ship operation such as maneuvering and docking or simply entering or leaving port.   The system on the Visby corvette is a CODOG system. 

The Twin Package can be configured with the engines side-by-side or with the engines mounted one over the other in a Vertical Twin configuration. Vericor Marine Sales Manager Tony Wilcoxson explains “We work with the main reduction gearbox supplier to achieve the ideal package design for the requirements of the ship, whether it is a narrow hull form or a low draft design”.  With the ability of companies such as Stork BV whose gear is shown in Fig. 2 to tailor the package, Vericor can meet stringent installation requirements.  The vertical Twin configuration has also been proven at high speed sea conditions.   This particular design allows adaptation to a variety of narrow hull forms including catamaran and trimaran. 

Vericor is the Original Equipment Manufacturer for the TF and ASE Series marine and industrial gas turbines and provides engineered systems and packages using these engines to customers and operators worldwide. Vericor’s TF50B engine is the commercial version of the engine that powers the US Navy LCAC air cushion vehicles and similar vehicles in Japan and Korea. TF engines power high performance fast ferries, mega yachts, fast patrol boats and corvettes. There are more TF Series marine gas turbines engines in propulsion service than any other in this size class.