Wartsilä Corporation introduced two new low-speed marine diesel engines, of which the cylinder bores are 620 and 720 mm. They will be available as electronically-controlled common-rail engines. The power output covers 8,000 to 28,880 kW, extending the available low-speed engine range from Wärtsilä to higher powers but also to lower revolutions (see Enclosure 1), answering the market need of significantly reducing fuel consumption by improving both engine and propeller efficiency.

The targeted commercial vessels are from Mini-Capesize and Panamax bulk carriers, to Aframax tankers and Handysize container vessels for the RT-flex62 engine and Capesize bulk carriers, Suezmax tankers and Sub-Panamax to Panamax container vessels for the RT-flex72 engine.

The key benefits compared to products available in the market today are:
- Optimised installation at shipyards
- Lower speed and optimised stroke-to-bore ratio offering better engine and propulsion efficiency as well as favourable piston dismantling height 
- Wider de-rating possibilities, further improving engine internal and/or propulsion efficiency
- Optimised Total Cost of Ownership
- Reduced CO2, SOx and NOx emissions, offering yards excellent possibilities to fulfil EEDI definition
- Fully compliant with the NOx emissions regulation of Annex IV of the MARPOL 1973/78 convention Tier II and available with IMO Tier III solutions
- R1/R1+ concept offering the engines a wide range of application, and therefore also the same engine room can be used in different vessel types

Main engine parameters
The RT-flex62 engine has cylinder dimensions of 620 mm bore and 2658 mm piston stroke, and a maximum continuous power of 2660 kW/cylinder at 97 rev/min (R1 rating).
The RTflex72 engine has cylinder dimensions of 720 mm bore and 3086 mm piston stroke, and a maximum continuous power of 3610 kW/cylinder at 84 rev/min (R1 rating).
Both engine types will be available with four to eight cylinders, so that the RT-flex62 engine covers an overall power range of 8,000 to 21,280 kW at 84-103 rpm, while the RT-flex72 engine covers an overall power range of 10,800 to 28,880 kW at 72-89 rpm (see Enclosure 1).

The layout fields of both engines, as defined by the power/speed ratings R1, R2, R3 and R4, are extended to the rating R1+ at the same power as R1 but with increased shaft speed.

The extended fields offer a widened flexibility to select the most efficient propeller speed for lowest daily fuel consumption, and the most economic propulsion equipment, namely the propeller, shafting, etc. R1+ was successfully applied for the first time on Wärtsilä RTA/RTflex82 bore engines (see Figure
1).

Infomarine On-Line Technical Library

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HHI-TC004, The new WΓ¤rtsilΓ¤ RT-flex62 and 72 bore electronically-controlled en	The new Wartsilä RT-flex62 and 72 bore electronically-controlled engines	2613 Kb