New generation quickly extends market reach
Regarded as the most significant development in the MAN low-speed portfolio since the introduction of the ME electronically-controlled generation of engines, the release of the ultra long stroke G-type has proved timely and apposite to market needs, writes David Tinsley.
Adopting the principles of the Mark 9 engine series introduced in 2006, and applying ME technology, the longer stroke encapsulated by the G-type reduces engine speed, contributing to the development of ship designs offering increased efficiency.
Following the launch of the G-type concept in October 2010, the range has been augmented this year by a clutch of new models, and the first orders have been announced.
The new generation of two-stroke diesels is intended for tankers, bulk carriers and also containerships which may be compatible with propellers of larger diameter than used in current designs, facilitating higher efficiencies following adaptation of the aftship hull form to accommodate the large propeller.
MAN suggests that such designs and propulsion arrangements offer the scope for fuel consumption savings in the order of 4-9%, with a corresponding reduction in CO2 emissions. At the same time, the engine itself can achieve a higher thermal efficiency using the latest combustion process parameters and design features.
The G-type came to market first in the shape of the G80ME-C9 model, giving 4,450kW/cylinder at its 68rpm L1 nominal maximum continuous rating (MCR), down to 3,040kW/cyl at just 58rpm on the L4 rating. Released in six- to nine-cylinder configurations, the engine accordingly provides for applications in the range of 26,700kW to 40,050kW, on the basis of L1 MCR. By comparison, the S80ME-C9 series covers the 27,060kW to 40,590kW band at an L1 running speed of 78rpm.
Although VLCCs were the original, main target of the G80ME-C9 development project, the debut contract sealed this year has emanated from the containership sector. Four such engines, in the six-cylinder version, have been specified by Greek owner Thenamaris for a quartet of 5,000TEU boxship newbuilds entrusted to Hyundai Heavy Industries. At the time of writing, other Greek interests were evaluating the G80ME-C9 for a series of 4,800TEU container vessels ordered from a Chinese yard, and the engine type was also being discussed for several possible VLCC newbuild projects.
In May 2011, the market reach of the G-generation was substantially expanded through the addition of new members of the family in the shape of the G70ME-C9, G60ME-C9 and G50ME-B9 models.
Delivering 3,640kW/cyl at 83rpm on the L1 rating, the G70 spans the 18,200kW to 29,120kW band in five- to eight-cylinder formats, while the G60 caters for applications from 13,400kW to 21,440kW through a maximum output of 2,680kW/cyl at 97rpm. The G50 takes the technology into further fields of the merchant vessel market, offering 1,720kW/cyl at 100rpm, giving 8,600kW in five-cylinder configuration up to 15,480kW in the nine-cylinder engine.
MAN has afforded owners, yards and designers further flexibility in G-engine usage by making two of the designs available at increased crankshaft speed, and higher output, with unaltered mean effective pressure (MEP).
Thus, a faster running variant of the G80ME-C9 can be supplied, whereby the L1 speed is 72rpm rather than the standard engine’s 68rpm, and the maximum power per cylinder is raised from 4,450kW to 4,710kW. The corresponding power span across the series is accordingly at a higher level of 28,260kW to 42,390kW.
The solution applied to the G50ME-B9 type takes the L1 speed from 100 to 108rpm, and commensurate power from 1,720kW/cyl to 1,860kW/cyl, increasing the application band to between 9,300kW and 16,740kW.
Technical papers issued by MAN relating to the adoption of G-type propulsion for VLCCs, and also handymax tankers and bulkers, point to the scope that these solutions offer in reducing EEDI (energy efficiency design index) values.
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