Package gives a good deal

Nine months after the genset engine made its debut, the propulsion version of the L27/38 has been launched by MAN B&W Alpha. At the same time the company has introduced a dedicated range of modular gearboxes and a new engine/gearbox monitoring system. At about 2MW, the 6L27/38 with its gearbox and PTO is over 2m shorter than an 8L28/32 with the old transmission. Both the new engine and gearbox range are available as separate items.

The HFO-burning 27/38 propulsion engine produces 340kW/cyl (at 800 rev/min) and comes in six to nine cylinder versions spanning the 2,000 to 3,000kW range. With a bore and stroke of 270 by 380mm, the engine has a BMEP of 23.5 bar and an SFOC of 185g/kWh (without attached pumps) and will eventually replace the L28/32. MAN B&W has no immediate plans to develop a vee version.

To cope with the L27/38?s P max of 200 bar, the main bearing tie bolts pass through the nodular cast iron block to ensure it is always under compressive forces. The high P max also dictates a requirement for a large diameter big end bearing journal meaning the lower end of the rod will not pass through the cylinder bore so a marine head connecting rod is used. A flame ring is included which keeps lub oil consumption to between 0.5 and 0.8 g/kWh.

The engines consist of front and rear boxes, a cylinder block and sump and a number of cylinder units. Unlike the genset version, the turbo-charger is positioned at the aft end complete with the charge air cooler. The front end box contains the lub oil pump, cooler and automatic filter along with the high and low temperature water pumps and related thermostats. To allow for use in a double-ended ferry, the full power of the engine can also be taken from the front end of the engine. External piping is kept to a minimum and there is no cooling water in the main engine block (although it is used in the top of the liners).

Overhaul intervals are set at 20,000 to 25,000 hrs and the engine uses the ?unit cylinder? design concept for ease of maintenance.

In designing the transmissions, MAN B&W Alpha were able to make both the engine and gearbox have a common foundation height for ease of installation at the shipyard. The single reduction transmissions are designed to fit as close to the engine as possible and minimise the overall length.

Four standard reductions are available – 2.79, 3.57, 4.43 and 5.57:1 – giving propeller speeds of 287, 224, 180 and 144 rev/min. This corresponds to propeller sizes of approximately 3, 3.25, 3.75 and 4.3m diameter ? a range identified by studying the data on ships in service. The degree of vertical offset depends on the ratio selected and ranges from 545mm (2.8 and 3.6:1) to 650mm with the 4.43:1 and 7.8mm with the 5.57:1 reduction.

Designed in association with Renk, also owned by the MAN group, the transmissions have case hardened helical cut alloy steel gears.