Wärtsilä Corporation has been awarded a contract by Mitsubishi Heavy Industries to supply eight Wärtsilä 12V46 medium-speed diesel engines for two new ferries ordered by Shin-Nihonkai Ferry of Osaka in Japan. The ferries are due for delivery from Mitsubishi's Nagasaki yard in mid 2004. They will employ a new propulsion concept known as CRP pod propulsion with a Combined Diesel-Electric and Diesel-Mechanical (CODED) machinery plant.
The new ferries will each have a single controllable-pitch propeller driven mechanically by two Wärtsilä engines, while an azimuthing pod drive immediately aft of the main propeller will be electrically driven from two Wärtsilä-engined generating sets. The pod drive is in contra-rotation to the main propeller, thus contra-rotating propeller (CRP) pod propulsion.
The ferries are designed for a trial speed of 31.5 knots. They measure 17,000 gross tons (Japanese domestic measurement) and have a length of 224.5 m.
The twin Wärtsilä 12V46C main engines used for mechanical drive of the main propeller have a combined output of 25.2 MW. The electrical power for the 17.6 MW azimuthing pod drive and the hotel load is supplied in each ferry by two similar Wärtsilä 12V46C engines in main generating sets and one smaller harbour generating set.
The CRP pod installation results in lower power demand than a conventional twin-shaft arrangement owing to the lower resistance of a single-skeg hull form and improved propulsion efficiency. The aft propeller takes advantage of the rotative energy left in the slipstream of the forward propeller when it turns in the opposite direction. The single-skeg hull also leads to a favourable wake field for the propellers.
The new CODED machinery with a CRP pod offers most of the benefits associated both with diesel-electric and diesel-mechanical machinery without their respective drawbacks. The result is a very competitive solution that provides outstanding technical and economical performance for fast RoPax vessels.
Wärtsilä has been involved in the development of this new efficient propulsion machinery solution for fast monohull RoPax vessels and presented the concept in 2001 (see Wärtsilä's Marine News magazine, No. 3-2001 which is available from Wärtsilä offices and also on the website http://www.wartsila.com).