two stroke engines EcoCam cuts fuel
retrofit solution for mechanically- controlled MAN B&W MC low speed engines with single turbochargers is now offered by MAN Diesel & Turbo to optimise low load operation. Fuel savings of 2-5 g/kWh with short payback times are promised by MAN EcoCam as well as an increased Pmax cylinder pressure through adjustable exhaust valve timing.
consumption on MC engines A
“Slow steaming is now an established industry standard across all segments, including the tanker and bulker markets,” explains MAN Diesel & Turbo’s head of retrofit and upgrade, Christian Ludwig. “We continuously seek to further refine our technology and improve efficiency,” he said. “The MAN EcoCam adjusts the exhaust valve timing between 10 and 60 per cent load, giving a 2-5 g/kWh fuel saving with minimal- to-no interruption to a vessel’s schedule during installation," said Mr Ludwig.”
MAN EcoCam is based on a flexible cam profile, termed a virtual cam, which is controlled hydraulically by adjusting the amount of actuator oil in the hydraulic pushrod. Thoroughly tested, the system is initially rolling out on a number of 500mm-bore MAN B&W S50MC-C engines but will be progressively introduced to the mid- and large-bore programme. Low-load tuning has an impact on torsional vibration and NOx emissions. When a low-load tuning method is installed on an engine, the torsional vibration impact and NOx level must be taken into account to ensure that the engine is not harmed and that NOx emissions comply with IMO requirements, the designer explained. MAN EcoCam customers are supported by a new torsional vibration calculation and NOx amendment. Two independent testbed installations and a shipboard trial have reportedly verified the fuel consumption reduction effect.
Earlier closure of the exhaust valve yields a higher compression pressure, thereby delivering a higher combustion pressure and lower fuel consumption. Flexible exhaust valve timing has traditionally only been available on electronically- controlled engines.
A typical fuel saving in the 2-5 g/kWh range (depending on the engine load profile) from the EcoCam can underwrite a system payback period of as little as 18 months for smaller engines, such as a six-cylinder S50MC-C model with 6,000 annual running hours.
20 I Marine Propulsion I April/May 2014
• The low load operating capability of MAN B&W engines is also improved by slide fuel valves, which are standard on all new engines and retrofittable to MC engines in service. By mid-2013 some 20,000 valves had been retrofitted to enhance fuel economy and environmental performance. A slide fuel valve eliminates the sac volume associated with conventional valves, lowering fuel consumption and eliminating dripping from the valve nozzle; NOx emission reduction potential is also cited. The reduced sac volume leads to an improved combustion process, resulting in fewer deposits throughout the gasways and a reduction in overall emissions, such as HC, NOx and particulate matter; additionally, visible smoke conditions are greatly reduced.
EXHAUST VALVE OPENING DIAGRAMS FOR STANDARD CAM AND MAN ECOCAM An advantage is also reported for slide fuel
valves in engines running in slow steaming mode; an improved low load performance has benefits with respect to soot formation. The need to run at high rpm to clean exhaust channels is reduced or eliminated. Replacing standard fuel valves with slide
valves is straightforward, said MAN Diesel & Turbo, and can be carried out by ship staff after instruction or by MAN PrimeServ.
The benefits are summarised as: improved low load performance; better combustion; reduced fouling of gasways, exhaust gas boiler and piston top land; no sac volume/no drips; less visible smoke formation; and lower emissions of HC, NOx and PM. MP
Standard Cam MAN EcoCam
50 75 100 125 150 175 200 Crank Angle REDUCED FUEL CONSUMPTION AS A FUNCTION OF ENGINE LOAD
Reduction in consumption (g/kWh)
7,00
6,00 5,00 4,00 3,00 2,00 1,00 0,00
0 10 20 30 Load % 40 50 60 Delta
www.mpropulsion.com
MAN EcoCam Fuel Saving Example: 6S50MC-C8,1
225 250 275 300
mm Lift
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