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  • Win Diesels
    Posted by Bill Sweetman 11:13 AM on May 19, 2011

    Rolls-Royce and Daimler announced a few weeks ago that they were planning to acquire Tognum AG, the holding company that also owns MTU. The likelihood is that MTU's aerospace and defense business would go to Rolls-Royce (MTU is already its partner in a number of ventures) while Daimler would take its automotive products.

    However, the move is important in naval propulsion, because MTU is the acknowledged driving force in a (fairly) quiet revolution in this realm over the past decade. At the IMDEX maritime defense show, going on this week in Singapore, that progress is clearly evident.

    The revolution has been brought about by a marked improvement in the power-to-weight ratio of high-speed marine diesels. (High speed in this context is relative to the Wartsila monsters that push freighters and cruise liners around, and means more than 1000 rpm -- Honda motorbikes these ain't.)

    This in turn had made it possible to build diesel-only warships with top speeds approaching or exceeding 30 knots. The Singapore Navy's Formidable-class frigates, with four of MTU's biggest diesels -- 9.1 MW V-20s, the size of a truck -- manage 27 knots and Kockum's FlexPatrol class is expected to reach 35 knots on diesel power.

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    Aside from metallurgy and other standard engineering technologies -- such as using three-dimensional aerodynamics to improve turbosupercharger design -- one of the keys to improved performance has been better electronic fuel injection. As in modern car diesel engines, the MTU marine engines use common-rail technology, with a single pump providing pressure and electronically controlled injectors feeding each cylinder. It's even possible to modulate the fuel flow during the firing stroke.

    Diesels are still heavier than turbines -- but may take up little more volume overall -- but they kick turbine butt on fuel efficiency, particularly at low power, which is where warships spend most of their time. The modern diesels, thanks to their fuel-injection systems, are very good at low-load situations and do not run into trouble with fouling and soot (which older diesels tended to do).

    So, as we point out in DTI this month, navies that have been wedded to the gas turbine for decades, since the gas turbines pushed out steam, are looking at another change. To switch or not? To diesel alone, or diesel for cruise and gas turbine for sprint (as done on Littoral Combat Ship, for example)?

    Rolls-Royce is clearly positioning itself to benefit, whichever the choice.

    Tags: ar99, rolls-royce, warships, IMDEX, mtu

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