Range of turbines
GE has six propulsion gas turbines available, with power outputs from 4.6 MW to 52.7 MW (see Table 1).
This range enables provision of power to ships ranging in size from fast patrol boats, at around 200 tons displacement, through to amphibious ships, of around 45,000 tons displacement.
The Royal Canadian Navy is planning to replace the Iroquois-class destroyer and eventually replace the Halifax-class frigate. The Halifax-class frigates use the LM2500, which has proven to be a reliable and effective unit for the RCN. The fact that the RCN is already familiar with the system simplifies operation of these units, and training of the sailors on the units.
Currently there are two battle-ready designs being offered for the new Canadian surface combatant, built by the world’s leading shipyards, that are powered by GE LM2500 gas turbines:
■ The Spanish Navy’s F105 frigate Cristobal Colon, built by Navantia.
■ Alion is offering the Dutch De Zeven Provincien-class frigate.
The Navantia and Alion ships each employ two gas turbines, as does the Halifax class frigate. The employment of two gas turbines offers significant benefits, as this enables the ship to achieve greater speed and possess inherent redundancy. Should one gas turbine be lost, for whatever reason, the ship will still be able to operate at mission speeds of 70-80 per cent of maximum speed.
In addition, the United States Navy plans to purchase up to 20 new FFG(X) frigates as successors to the current Littoral Combat Ships (LCS). GE’s LM2500 family of gas turbines meets the requirements of the US Navy. GE currently provides 97 per cent of the commissioned propulsion gas turbines in the US Navy fleet, demonstrating experience at sea.
The US Navy’s request for information for the FFG(X) frigate outlined tiered ranking of key frigate attributes. GE analysed market data to better understand how its engines compare to the needs of past frigates. Amongst the findings were the following:
■ Gas turbines make up 80 per cent of the prime mover market, and are used in a variety of configurations, often in combination with diesel engines.
■ Gas turbines are preferred when lower weight and volume, higher availability, lower maintenance requirements, and lower noise are needed.
The average top frigate speed is 28- 30 knots, and this can be achieved with a gas turbine of 35 MW or smaller.
The US Navy ranked different attributes into three tiers, reflecting its view of the comparative importance of the attributes:
■ First tier (the most important): availability, reliability, service life, and survivability
■ Second tier (next in importance): manning accommodation, range, and thermal loads
■ Third tier: power density and sustained speed.
The US Navy survivability requirements states the propulsion system are to be Grade A shock tested. The LM2500 gas turbine family are the only gas turbines that have met these shock tests.
Elsewhere, there is also a great deal of interest in the larger power GE LM6000 gas turbine, which received naval certification in 2015 after successfully completing engine and module testing. There are over 1300 industrial engines in service, 17 in marine applications, with over 33 million operating hours. The LM6000 is being proposed for the South Korean FFX Batch 3 frigate. It is being also being considered in a generator set configuration for India’s IAC-2 aircraft carrier, which will leverage GE’s naval generator set packaging expertise.
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