The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is currently considered the largest reciprocating engine in the world, designed for large container ships, running on heavy fuel oil. It stands at 13.5 metres (44 ft) high, is 26.59 m (87 ft) long, and weighs over 2300 tonnes in its largest 14-cylinder version — producing 80080 kW.
The 14-cylinder version was put into service in September 2006 aboard the Emma Mærsk. The design is based on the older RTA96C engine, but revolutionary common rail technology has done away with the traditional camshaft, chain gear, fuel pumps and hydraulic actuators. The result is better performance at low revolutions per minute (rpm), lower fuel consumption, and lower harmful emissions.
The engine has crosshead bearings so that the always vertical piston rod allows a tight seal under the piston. As a consequence of this design the lubrication of the engine is split, with different lubricants for the cylinders and the crankcase, with each being specialised and dedicated to their role. The cylinders are lubricated by continual, timed injection of consumable lubricant which is formulated to protect the cylinders from wear and neutralise the acids formed during combustion of the high-sulfur fuels commonly used. The crosshead design reduces sideways forces on the piston, keeping diametral cylinder liner wear in the order of only about 0.03 mm per 1000 hours.
The descending piston is used to compress incoming combustion air for the adjacent cylinders which also serves to cushion the piston as it approaches bottom dead centre (BDC) to remove some load from the bearings. The engine is uniflow-scavenged by way of exhaust valves that are operated by electronically-controlled, common-rail hydraulics, thus eliminating the camshaft.
25 engines are in service with 86 on order.
Technical Data (as of 2008)
|Configuration||Turbocharged two-stroke diesel straight engine, 6 to 14 cylinders|
|Displacement||1,820 litres per cylinder|
|Engine speed||22–102 RPM|
|Torque||7,603,850 newton metres (5,608,310 lbf·ft) @ 102 rpm|
|Mean effective pressure||1.96 MPa @ full load, 1.37 MPa @ maximum efficiency (85% load)|
|Mean piston speed||8.5 meters per second|
|Specific fuel consumption||171 g/(kW·h)|
|Power||up to 5,720 kW per cylinder, 34,320–80,080 kW (46,680–108,920 BHP) total|
|Power density||29.6 to 34.8 kW per tonne, 2300 tonnes for the 14 cylinder version|
|Mass of fuel injected per cylinder per cycle||~160 g (about 6.5 ounces) @ full load|
|Crankshaft weight||300 tons|
^ “The world’s most powerful Engine enters service” (Press release). Wärtsilä Corporation. 2006-09-12.
^ “Increased power for the Sulzer RTA96C” (Press release). MarineLink.com. 2001-03-15.
^ a b c Hanlon, Mike. Most powerful diesel engine in the world GizMag. Accessed: 24 February 2011.