MAN Diesel (former MAN B&W Diesel) has just launched a new and updated version of their K90ME/ME-C engines. The outputs have been boosted by 25 %, meaning that a K90 engine, on a cylinder-by-cylinder basis, will be able to replace contemporary larger bore engines, and thus be a much more cost effective alternative. Selecting a 90-bore engine instead of a higher-bore will give the ship more space for cargo. The new design features applied with reference to the higher rating and a strong emphasis on reliability are: (1) Cast or welded cylinder frame, (2) frame-box with triangular stay bolt tube design plates, (3) twin stay bolts and 360 deg thrust bearing, (4) W-seat, (5) exhaust valves, and (6) OROS piston. The mean effective pressure (MEP) of 20 bar has been chosen and, in order to offer a really attractive specific fuel oil consumption, the maximum firing pressure is 160 bar. These performance data together with a mean piston speed of 9 m/s yield a power per cylinder of 5720 kW/cyl. for the K90ME and 5730 kW/cyl. for the K90ME-C. The K90 engine series will be available with cylinder numbers from 6 to 12. As standard, the cylinder frame of the updated engines is of the cast design. A welded cylinder frame is optional. MAN sees a number of inherent advantages in the welded design, such as increased rigidity as well as reduced weight. The welded design makes it possible to integrate the scavenge air receiver in the cylinder frame, and the chain case is integrated as well, giving rise to a total weight saving of 30 %. In addition to this important feature, dimensions are smaller, thereby reducing the total engine height. The backbone of this Oros combustion chamber design is the piston and cylinder cover geometry, which concentrates the hot combustion gases around the fuel nozzles, and the high top land piston, which allows a low position of the mating surface between cylinder liner and cylinder cover, thereby reducing liner wall temperatures and giving controlled cold corrosion, which is good for refreshing the liner surface. In order to obtain a comfortably low piston temperature in service, the so called spray cooling insert is applied. The exhaust valve unit is of a modified type, implying the use of a low grade cast iron housing with water cooling around the spindle guide and bore cooled twin stud bosses.


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