JUNE 27, 2012 — Looking for fuel savings, lower operating costs and lower emissions, more owners of smaller merchant vessels are opting for two-stroke, low speed engines over their four-stroke counterparts.
To meet this demand, Wärtsilä has successfully tested a new RT-flex50 version D low-speed engine with the turbocharger on the driving end side (see earlier story). With the addition of this engine, Wärtsilä now has an additional two-stroke engine that can be fitted to smaller vessel types. The space-saving design opens the way for the fuel-saving engine type to be offered for ship designs with slim stern sections, including smaller tankers, bulk carriers and "handysize" container vessels.
The new layout sees an A170-L turbocharger unit from ABB Turbo Systems positioned directly above the fly wheel at the driving end of the engine. Wärtsilä licensee Hyundai Heavy Industries (HII), South Korea, recently completed the first shop tests on an RT-flex50 version-D engine to feature an A170-L turbocharger unit from ABB in the new lay-out.
The HHI tests verified that the configuration provides a viable alternative to other engine types featuring a smaller cylinder bore and higher speed. The first engine to pass the test will be installed on a newbuld at HHI's Ulsan shipyard for an undisclosed owner.
According to Alexander Mutter, ABB Turbo Systems Ltd. Manager Sales Engineering Marine: "The D version engine is one of Wärtsilä's latest generation 'high efficiency' RT-flex models, and is designed for optimised performance over the full load range."
"''High efficiency' here means consuming 1g/kWh less fuel over the whole engine load range when compared to the previous standard engine version, in line with fulfilling the International Maritime Organization's TIER II NOx requirements," says Mr. Mutter. "For derated engines and special tunings, efficiency gains are even greater. Depending on the engine load, efficiency gains of up to 4.5 g/kWh are possible according to the Wärtsilä layout data for this engine. Lower fuel consumption always reduces CO2 emissions."
Mr Mutter said that the A170-L needed to accommodate pressure ratios of up to 4.8, and achieve efficiency as high as 68 percent at full load, and as much as 3 percent more at part load.
For ABB Turbocharging, the HII shop tests focused on achieving the correct scavenging air pressure and confirming efficiency over the whole engine load range. Stability against surging was also verified, as was the turbocharger's ability to operate below set speed and temperature limits.
Mr Mutter said that, as well as confirming the configuration's fuel saving and NOx emissions reducing attributes, the shop tests confirmed that the D engine working with the A170 unit achieved smokeless operation, especially at low loads. He added that the new lay-out gave more space to service on the turbocharger.