Wärtsilä Corporation's diesel engine.

The Wärtsilä RT-14flex96C turbocharged two-stroke diesel engine is the largest prime mover in operation today. Wärtsilä Corporation, a Finnish enterprise that specializes in marine propulsion systems, manufactures the engine. The massive engine is designed to power very large container ships.

The engine is five stories high (13.5m), 27m long, and weighs over 2,300 metric tons in its largest 14-cylinder version, and can produce up to 80,800 kW (108,920 horsepower). RT-flex96C engines can meet the propulsion requirements of large, fast containerships up to about 12,000 twenty-foot equivalents (TEU) capacity at service speeds of around 25 knots. (TEU is the shipping industry's standard for measuring container size, ship capacity and volume. One 20-foot container is equal to one TEU).

The cylinder bore is just under 38" and the stroke length is about 98". Each cylinder displaces 111,143 cubic inches (1820 liters) and produces 7, 780 horsepower. Total displacement comes out to 1,556,002 cubic inches (25,480 liters) for the 14-cylinder version.

Fuel consumption at maximum power is 0.278 lbs per hp per hour (Brake Specific Fuel Consumption). Fuel consumption at maximum economy is 0.260 lbs/hp/hour. At maximum economy the engine exceeds 50% thermal efficiency. Even at its most efficient power setting, the 14-cylinder consumes 1,660 gallons of heavy fuel oil per hour.

Emma Maersk container ship. Credit: Christian Hansen.

The RT-flex96C has a waste heat recovery plant that the well-established concept of passing the exhaust gases of the ship's main engine through an exhaust-gas economiser to generate steam for a turbine-driven generator. The generated electrical power amounts to about 12 per cent of the engine power, and is used to assist ship propulsion or for supplying shipboard services. Heat is also recovered from the engine's scavenge air and jacket cooling water for feedwater heating. These heat recovery systems also reduce emissions of CO₂, SO_x and NO_x.

The first Wärtsilä RT-14flex96C was put into service in September 2006 aboard the Emma Mærsk, a container ship owned by the A.P. Moller-Maersk Group, a Danish shipping company. When she was launched, the Emma Mærsk was the largest container ship ever built, with a capacity of about 11,000 TEU.

Technical information

• 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

Sources

• Walke, Todd, The most powerful diesel engine in the world, University of Bath, Accessed 8 September 2008.
• Wärtsilä Corporation, The world's most powerful Engine enters service, Accessed 8 September 2008.
• Wärtsilä Corporation,Wärtsilä RT-14flex96, technical data tables. Accessed 8 September 2008.