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Wärtsilä-Sulzer RTA96-C

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ConfigurationTwo-stroke straight-14
Cylinder bore96 cm (38 in)
Piston stroke2.50 m (98 in)
RPM range
Max. engine speed120
Fuel typeheavy fuel oil
Power output80,080 kW (107,390 hp)
Length26.59 m (87.2 ft)
Height13.5 m (44 ft)
Dry weightover 2,300 tons

The Wärtsilä RT-flex96C is a two-stroke turbocharged low-speed diesel engine designed by the Finnish manufacturer Wärtsilä. It is designed for large container ships that run on heavy fuel oil. Its largest 14-cylinder version is 13.5 meters high, 26.59 meters long, weighs over 2,300 tonnes, and produces 80.08 megawatts. The engine is the largest reciprocating engine in the world.

The 14-cylinder version first entered commercial service in September 2006 aboard the Emma Mærsk. The design is similar to the older RTA96C engine, but with common rail technology (in place of traditional camshaft, chain gear, fuel pump and hydraulic actuator systems). This provides maximum performance at lower revolutions per minute (rpm), reduces fuel consumption and emits lower levels of harmful emissions.

The engine has crosshead bearings so the always-vertical piston rods create a tight seal under the pistons. Consequently, the lubrication of the engine is split: the cylinders and the crankcase use different lubricants, each being specialised for its designated role. The cylinders are lubricated by continuous timed injection of consumable lubricant, formulated to protect the cylinders from wear and to 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 down to about 30 μm per 1,000 hours.[1]

As a piston descends, it compresses incoming combustion air for the adjacent cylinders. This also serves to cushion the piston as it approaches bottom dead centre, thereby removing some load from the bearings. The engine is uniflow-scavenged by way of exhaust valves that are operated by electronically controlled hydraulics, thus eliminating the camshaft.

As of 2006,[needs update] more than 300 RT-flex96C engines and older RTA96C engines were in service or on order.[2]

Technical data (as of 2008)[edit]

Configuration Turbocharged two-stroke diesel straight engine, 6 to 14 cylinders
Bore 960 mm (38 in)
Stroke 2,500 mm (8.2 ft)
Displacement 1,828.7 litres (111,597 CI) per cylinder
Engine speed 15–102 RPM[3]
Mean effective pressure 1.96 MPa @ full load, 1.37 MPa @ maximum efficiency (85% load)
Mean piston speed 8.5 meters per second
Brake specific fuel consumption 171 g/(kW·h)[3][a]
Power Up to 5,720 kW per cylinder, 34,320–80,080 kW (46,020–107,390 bhp) total
Torque Up to 7,603,850 N⋅m (5,608,310 lbf⋅ft) @ 102 rpm
Power density 29.6–34.8 kW (39.7–46.7 bhp) per tonne, 2,300 tonnes for the 14-cylinder version
Mass of fuel injected per cylinder per cycle ~160 g (5.6 oz) @ full load

(Whole engine uses up to 250 tons of fuel per day.)

Crankshaft weight 300 t (660,000 lb)[1]
Piston weight 5.5 t (12,000 lb)
Piston height 6 m (20 ft)

See also[edit]


  1. ^ 85% load, R2 operating point : max speed, lowest power


  1. ^ a b Hanlon, Mike. Most powerful diesel engine in the world GizMag. Accessed: 24 February 2011.
  2. ^ "The world's most powerful Engine enters service" (Press release). Wärtsilä Corporation. 2006-09-12.
  3. ^ a b "RTA-C Technology Review" (PDF). Wärtsilä. 2004. p. 23. Archived from the original on December 26, 2005.{{cite web}}: CS1 maint: unfit URL (link)

External links[edit]