Mitsubishi Heavy Industries Technical Review Vol. 46 No. 1 (Mar. 2009)15

Joint Development of 350/400 mm Bore Size Engineswith WÄRTSILÄ
POWER SYSTEMS HEADQUARTERS
INDUSTRIAL ENERGY POWER SYSTEMSDEPARTMENT 81-3-6716-3383

The Marine Diesel Business Unit of Kobe Shipyard & Machinery Works of Mitsubishi
Heavy Industries, Ltd. (MHI) together with Wärtsilä developed new small marine low-speed
diesel engines with bore sizes of 350 and 400 mm.

|1. Features of these engines
The outputs of the new engines are between 3,500 and 9,000 kW. The engines weredeveloped in order to offer optimal outputs and speeds for various small and intermediate-size
commercial ships below 30,000 DWT class, such as small bulk carriers, tankers,
freezing/refrigerator vessels, and feeder container ships. These ships are expected to be in highdemand, not only in East Asia, where the market for new ships is growing rapidly, especially in
China, Korea, Japan, and Vietnam, but also in other countries throughout the world.
The development took advantage of the expertise of both companies. MHI is responsible forthe development of various optimal structures for the small engines. They must be superior to theproducts of competing companies, and MHI will develop them by using its experience and databasefor small UE engines. MHI will market the mechanically controlled UEC-LSE, while Wärtsilä
develops the electronically controlled RT-flex and the mechanically controlled RTA. The first unit
with a bore size of 350 mm is scheduled to be launched in the first half of 2011, and the unit withthe first 400-mm-bore engine will be launched one year later. During the development process, wewill use a standardized modular design that considers the use of parts in common, and promotes thecommon use and standardization of parts in existing small UE engines and 350/400-mm-bore
engines.
The biggest advantages of the new engines are their lower fuel consumption, lower
consumption of cylinder oil, higher reliability, and longer overhaul interval. In addition, theseengines meet secondary regulations for air pollutant emissions (Tier II) of the International
Maritime Organization (IMO). We will improve our competitive strength by reducing
manufacturing costs, and, simultaneously offer optimal diesel engines for ships from the viewpointof output, propeller speed, size, weight, and electricity consumption.

|2. Principle details of the engines
The specifications of the engines are listed in Table 1. The UEC35LSE by MHI and theRT-flex 35 and RTA35 by Wärtsilä have a bore size of 350 mm and a piston stroke of 1,550 mm at
167 min-1, with a maximum continuous output per cylinder of 870 kW. The UEC40LSE and theRT-flex 40 and RTA40 have a bore size of 400 mm and a piston stroke of 1,770 mm at 146 min-1,with a maximum continuous output per cylinder of 1,135 kW. Engines with between five and eightcylinders are planned for both products. The UEC-LSE will be manufactured by MHI and its
licensees, while the RT-flex and RTA will be manufactured by licensees of Wärtsilä.
Table 1 Engine specifications
TypeBore size (mm)Piston stroke (mm)Output (kW/cyl.)
Number of revolutions (min-1)
Mean effective pressure (MPa)Mean piston speed(m/s)
Number of cylinders
Output range (kW)UEC35LSE

RT-flex35/RTA35
350
1 550
870
167 – 142
21.0
8.6
5–83 475 – 6 960

UEC40LSE

RT-flex40/RTA40400
1 770
1135
146 – 124
21.0
8.6
5–8
4 550 – 9 080