Feature 8 | PROPULSION MT30 evolving to meet new requirements


Major US and British naval programmes are benefiting from the latest marine gas turbine from Rolls-Royce, the MT30, which is preparing to take on its great rival, GE Marine’s LM2500 family in a head-to-head contest.


American-designed prime mover has been a runaway success since it was installed in the Spruance class in the 1970s. Since then there have been a number of orders from the US Navy, where it equips the Ticonderoga class cruisers, Arleigh Burke class destroyers and Oliver Hazard Perry class frigates. Tese domestic orders have encouraged other navies, and 31 of them have received some 1300 engines. Rolls-Royce, which pioneered marine gas


M


turbines, has been less successful, although it does produce the AG9140 3MW gas turbine generators used in the Arleigh Burkes. However,


the MT30, which is


derived from the Trent gas turbine, has had some significant successes in GE’s domestic market, the US Navy, with the Zumwalt (DDG 1000) class destroyers and the Lockheed-Martin produced Freedom (LCS 1) class Littoral Combat Ships. In addition, it is the heart of the integrated electrical propulsion system selected for the British Queen Elizabeth or ‘QE’ class carriers. Te MT30 is a twin-spool, high pressure


ratio gas turbine which can be configured for axial intake plenum or compact rotatable radial intake. It has an eight-stage variable geometry intermediate pressure compressor and a six-stage high-pressure compressor. The


total module weight including


enclosure and ancillary components is some 27.8tonnes compared with 22tonnes for the basic LM2500 module (22.7tonnes for the latest version) fitting into a space 8.2m long, 2.74m wide (2m in the latest version) and 3.05m high (2.4m). Te LM2500 generates 25MW and GE


Marine has gradually increased this to 30.2MW in the LM2500+ and to 35.3MW in the fourth generation LM2500G4. However, the MT30 is rated-approved at 36MW flat rated to 38°C and 40MW at 15°C and maintains operating efficiency down to


34


25MW, and it is this growth potential which Rolls-Royce regards as a major sales point. Ship demand for electricity has been


growing steadily, in order to power the ever more sophisticated electronics on board modern vessels, but there is also a growing trend towards electrical propulsion, even away from the traditional propeller drive-shaft, and some vessels, such as France’s Mistral class amphibious ships, have Mermaid propulsion pods. Te potential of the MT30 is extremely


attractive but is balanced by higher unit costs and size, which meant France and Italy eventually selected the LM2500 as prime moved for the FREMM class frigates; although, the GE case was boosted by production facilities in France and Italy. Rolls-Royce is responding by designing


a compact single-MT30 package with enclosure and ancillaries designed to fit into the same space as the LM2500 (although it will weigh more than 30tonnes). Te compact package, whose design will


be completed later this year, will be qualified to civilian standards, including shock – to avoid export regulations, especially those of the US – but it will not be offered as a product. Instead shipyards will be offered the basic design which they can then adapt to meet the domestic requirement or requirements.


arine gas turbines are derived from aero-engines, the LM2500 coming from the CF 6. The


A compact, single MT30 package would have the same footprint as the LM2500.


Te package meets requirements for pure


gas turbine or combined gas turbine/diesel or gas turbine/diesel electric prime movers, but Rolls-Royce is also offering a hybrid system based on the compact package, in which the gas turbine would be linked to two direct-drive, shaft-mounted, electric motors with two diesel generators. Te latter is especially relevant in that Rolls-Royce is part-owner with Daimler of Tognum, whose MTU high-speed diesels are widely used by the world’s navies. The compact package is likely to be


accepted for the Royal Navy’s next generation Type 26 frigate, and is also being offered to South Korea for the FFX Batch 2 frigates. It might also be offered to the US Navy for the Arleigh Burke Flight III destroyers, which will require greater electrical power than earlier flights, and possibly the Flight IV if the US Navy decides to seek an electric drive or an integrated electrical propulsion system. Meanwhile, one major navy which might


be interested in the MT30 is Japan’s Maritime Self Defense Force, which is the largest user of Rolls-Royce marine gas turbines with an inventory of 144 Olympus, Tynes and Speys. Rolls-Royce has a close relationship with Kawasaki Heavy Industries and hopes to add the MT30 to Tokyo’s inventory in the original and compact form. WT


Warship Technology May 2012


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