gas turbines
Compact power for warship gensets and propulsion
Gas turbine solutions are favoured for diverse naval applications but growing interest in LNG-fuelled installations could stimulate commercial shipping business
by Doug Woodyard
contract to power the US Navy’s future fleet of hovercraft, the Ship-to-Shore Connector (SSC), specifies Rolls-Royce MT7 marine gas turbines derived from the group’s successful AE1107 engine. Only minor variations from the aero parent, which powers the US Marine Corp’s Bell Boeing V-22 Osprey tilt-rotor aircraft, are required for the SSC application, resulting in more than 90 per cent component commonality. Among the refinements are a new engine
A
controller, bleed system and power take-off shaft to suit the requirements of the hovercraft. Rolls-Royce – whose hovercraft propulsion pedigree includes the world’s largest, the SRN 4, during the 1960s and 1970s – will work with Textron Marine & Land Systems to design and manufacture the intake and exhaust architecture as well as the mounting system. US-based Textron is developing the SSC and will build the initial craft in a programme that could extend to 73 units. The fleet will replace the US Navy’s current Landing Craft Air Cushion (LCAC) hovercraft over the next 20 years for rapidly deploying personnel and vehicles between surface ships and the shore. Four MT7 gas turbines in each SSC will be connected to an advanced gearbox system to provide both propulsion and lift. “Our gas turbine technology will increase the power of the hovercraft by 25 per cent compared with the previous generation, enabling each to transport up to 74 tonnes of cargo at speeds over 35 knots,” reported Andrew Marsh, Rolls-Royce president-naval. “At the same time, our engines will improve fuel efficiency by 11 per cent.” “The AE1107 is the ideal choice for several noted SSC programme manager
reasons,”
Paul Jones. “The marinisation of an aero gas turbine would normally require some special blade coatings so the engine can withstand the maritime environment. But the Osprey is designed to fly from ships and has accumulated
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over 170,000 operating hours, so development risk is minimised. The MT7 will undergo endurance testing to become type-certified to ABS’ Naval Vessel Rules.”
The MT7’s twin-shaft axial design incorporates a 14-stage compressor followed by an effusion-cooled annular combustor, a two-stage gas generator turbine and a two- stage power turbine. The cold end-drive engine features six stages of variable compressor vanes, a dual channel full authority digital electronic control system, modular construction and an ‘on-condition’ maintenance capability. Fuel and oil systems that are fully
integrated on the engine assembly contribute to compactness and lightness. Significant in-service benefits in terms of spares holdings and maintenance training are anticipated from the V-22 Osprey aircraft deployed by the US Navy ships that will carry the SSC hovercraft. A fully developed suite of component repairs, special tools and publications are available from the aircraft engine to support the MT7. AE family upgrades – which have been previously carried out on the engine across a range of aircraft – could increase the available power of the MT7 by up to 20 per cent or extend its life. The power growth capability would
Rolls-Royce MT7 turbines – four per shipset – will power the US Navy’s SSC hovercraft fleet
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