main engine · propulsion system

MAN B&W 6G80ME C10.5

The MAN B&W 6G80ME-C10.5 is a large, low-speed, two-stroke crosshead marine diesel engine of the type used for the main propulsion of large ocean-going ships. It belongs to MAN Energy Solutions' ME series of electronically controlled engines, and the naming conveys a good deal about it: the 6 is the number of cylinders, the G marks it as one of the ultra-long-stroke Green series designed for high efficiency at lower speeds, the 80 is the cylinder bore in centimetres, and ME denotes electronic control of the engine. Low-speed two-stroke engines like this are the dominant form of main propulsion for large container ships, bulk carriers and tankers because they are highly efficient, can burn heavy fuel oil, and turn slowly enough (typically well under a hundred revolutions per minute) to drive a large, efficient fixed-pitch propeller directly, without any reduction gearbox. Their great stroke relative to bore, the hallmark of the G series, suits the slow propeller speeds that improve overall propulsive efficiency and fuel economy on long deep-sea voyages. The ME designation marks the shift from the older mechanically camshaft-controlled engines to electronic control. In an ME engine the timing of fuel injection and of the exhaust valve is governed by a computer system and hydraulically actuated, rather than fixed by a camshaft, which allows the engine to be optimised across its whole load range, improves fuel consumption and emissions, eases starting and manoeuvring, and provides monitoring and diagnostics. As a crosshead engine it separates the combustion space from the crankcase with a diaphragm and stuffing box, allowing the use of cylinder oil suited to heavy fuel above and clean system oil below. Engines of this size and type are the beating heart of a large merchant ship, and their reliability, efficiency and careful maintenance are central to the economics and safe operation of the vessel.