Marine Low Speed 

MAN B&W Engines Set Sights on Tier-II Limits

MAN Diesel & Turbo continues program of engine development

At the beginning of 2010, MAN Diesel & Turbo launched the first so-called “Tier II fuel optimisation” for a limited number of MAN B&W low speed diesel engines.

The company has now looked at its complete engine programme and investigated if the same SFOC reduction could be achieved. Against this background, it has been established that SFOC can be lowered by 1-2 g/kWh for a number of engines, while still complying with Tier-II NOx limits.

In the first release of the MAN B&W Tier II Engine Programme, the SFOC on mechanically controlled engines had increased by up to 6 g/kWh (MC & MC-C), whereas the electronically controlled engines, designated ME, saw a fuel penalty of only up to 4 g/kWh, thanks to the much better possibilities on the ME types for adjustment and control of the fuel injection and the opening/closing of the exhaust valve.

These new, Tier-II SFOC reductions are obtained through a combination of several factors depending on engine type, such as:

  • increased scavenge-air pressure
  • reduced compression ratio (two-stroke Miller timing)
  • increased maximum combustion pressure
  • adjustments of compression volume and design changes

In order to distinguish between the different IMO Tier-II versions of fuel optimisation, another number is introduced after the Mark designation, whereas the IMO Tier-I engines have no additional number, that is:

  • S80ME-C8/9 = original Mk 8/9 engine that complies with Tier I
  • S80ME-C8.1/9.1 = original Mk 8/9 engine that complies with Tier II
  • S80ME-C8.2/9.2 = the new fuel-optimised version that complies with Tier II

Ole Grøne, Senior Vice President of MAN Diesel & Turbo Low Speed Promotion and Sales said: “The original Tier-II engines and the fuel-optimised versions correspond to what others refer to as ‘cost-optimised’ engines and ‘economy-optimised’ engines. In this context, we direct attention to the improved low-load optimising possibilities, made available for both standard and fuel-optimised versions of our Tier II engine programme.” This can be achieved by using the low-load package technologies corresponding to and matching what others refer to as ‘delta’ and ‘low-load tuning’:

  • exhaust Gas Bypass (EGB) for ME/ME-C, MC/MC-C and ME-B engines
  • variable turbine area (VTA) of turbochargers for ME/ME-C, MC/MC-C and ME-B types
  • part-load tuning of ME/ME-C engines
  • turbocharger cut-out

Documentation on low-load package technologies is currently being prepared and for issue. In the intervening period, MAN Diesel & Turbo is ready to support interested customers with case studies of low-load package solutions for specific projects.