Wärtsilä-Sulzer RTA96-C

The Wärtsilä RT-flex96C turbocharged two-stroke diesel engine is currently considered the largest reciprocating engine in the world, designed for large container ships, running on heavy fuel oil. It is five stories high (13.5 m), 27 m long, and weighs over 2300 tonnes in its largest 14-cylinder version producing more than 80 MW (109,000 bhp). It was put into service in September 2006 aboard the Emma Mærsk. [cite press release | title = The world's most powerful Engine enters service | publisher = Wärtsilä Corporation | date = 2006-09-12 | url = http://www.wartsila.com/,en,press,0,tradepressrelease,8F51527F-00A3-4C5F-ABEA-B543789ACA1B,26EE6684-06C9-48B3-920A-3B238B7C302A,,.htm] The design is based on the older RTA-96C 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 RPM, lower fuel consumption and lower harmful emissions. As of 2008, the power output of the 14 cylinder version has been increased to 84.42 MW (114,800 bhp).

Crosshead bearings

The engine has crosshead bearings. One of the reasons that the large two stroke diesels use this design is so that the lubrication in the combustion area is separated from the crank case oil, which stays clean from combustion products. The upper portion is lubricated by continuous injection of consumable lubricant which is formulated to stand up to high temperatures and high sulfur.

Another reason is that the always vertical piston rod allows a tight seal under the piston. 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 center (BDC) to remove some load from the bearings.

Technical data (as of 2008)

; Configuration : turbocharged two-stroke diesel straight engine, 6 to 14 cylinders; Cylinder bore : 960 mm (37.79 inches); Piston stroke : 2500 mm (98.42 inches) ; Displacement : 1820 liters per cylinder (111,063 cubic inches); Speed : 92–102 rpm; Mean effective pressure : 1.96 MPa @ full load, 1.37 MPa @ maximum efficiency (85% load); Mean piston speed : 8.5 m/s; Specific fuel consumption : 171 g/(kW·h) (126 g/(bhp·h)) @ full load : 163 g/(kW·h) (120 g/(bhp·h)) @ maximum efficiency; Power : up to 6030 kW per cylinder, 36,180 to 84,420 kW (49,200 to 114,800 bhp) altogether; Power density : 29.6 to 34.8 kW per tonne, 2301 tons for the 14 cylinder version; Amount of fuel injected in a single cycle of single piston : ~160 g @ full load

Efficiency

The Specific fuel consumption efficiency of the RTA96 is 5% worse than the best piston engines. The minimum 163 g/kW·h translates to 3.6 MJ/kW·h / 0.163 kg/kW·h = 22.1 MJ/kg of work from chemical energy. With a 42.7 MJ/kg fuel, the efficiency is 22.1 MJ/kg / 42.7 MJ/kg = 51.7%. The Man S80ME-C7 [ [http://www.manbw.com/engines/TwoStrokeLowSpeedPropMEEngines.asp?model=S80ME-C7 Man Diesel Se - Marine ] ] is substantially better than this at 155 g/kWh.

References

External links

* [http://www.wartsila.com/ Wärtsilä homepage]
* [http://www.wartsila.com/Wartsila/global/docs/en/ship_power/products/2str/2008/main-data-wartsila-rtflex96c-rta96c.pdf Wärtsilä Ship Power Systems brochure 2008]
* [http://www.bath.ac.uk/~ccsshb/12cyl/ The Most Powerful Diesel Engine in the World] , Todd Walke