The maximum continuous power output of the RT-flex50 has been raised by 5.1 per cent from 1660 to 1745 kW/cylinder (2260 to 2375 bhp/cylinder) in the '-D' version at the same running speed of 124 rpm. Thus, with five to eight cylinders in-line, the RT-flex50 in the '-D' version covers a power range of 6100-13,960 kW (8300-19,000 bhp) at 99-124 rpm.
At the same time the brake specific fuel consumptions (BSFC) have been reduced by 2 g/kWh. Thus at the maximum continuous rating R1, the full-load BSFC has been reduced from 171 to 169 g/kWh. This fuel saving is made possible by employing the latest, higher-efficiency turbochargers in the "-D" version.
Wärtsilä says that the flexibility provided by the layout field for engine power and speed can be used to save money on fuel. For example, if a '-D' engine is derated to the same cylinder power output as the '-B' version, then the BSFC at full load is reduced by 4.5 g/kWh compared with the '-B' version.
For a typical bulk carrier with a six-cylinder RT-flex50 engine this can translate into annual savings of $76,000 when operating for 6000 running hours a year with heavy fuel oil costing $300 per tonne. The company says that even greater savings are possible if the engine is derated to a lower running speed (rpm) at the derated power to gain the benefits of a better propulsion efficiency.
The RT-flex50 incorporates the latest electronically-controlled common-rail technology for fuel injection and valve actuation. The new technology provides great flexibility in engine setting, bringing benefits in lower fuel consumption, lower minimum running speeds, smokeless operation at all running speeds, and better control of other exhaust emissions.
The first of these new engines entered service in January 2006 and by the end of August 2007, a total of 157 engines aggregating 1604 MW (2,180,900 bhp) were delivered or on order.
Engines have been ordered for newbuildings contracted for owners in various countries including China, Greece, Scandinavia, Germany, India, Japan and the Netherlands. They comprise 38 seven- and 119 six-cylinder engines, the newbuildings being mainly 50,000 to 80,000 dwt bulk carriers and 37,000 to 60,000 dwt product tankers, together with a number of feeder container ships, car carriers and LPG carriers.