New heights for common rail

A 70-ton four-stroke marine diesel engine resting majestically amid the Austrian Alps is not something one sees everyday. MAN B&W Deisel recentlywent to the trouble of transporting the 32/40CR to the Hotel Gut Brandhof in Saalfelden in order to introduce the new medium-speed marine diesel engine and, in particular, its common rail injection technology.

Capable of operating on heavy fuel oil, the 32/40CR marks a leap in engine development technology, particularly with regard to fuel consumption and exhaust emissions. The common rail system, developed in-house MAN B&W, enables exact combustion control within the operating range of the engine flexibly.

The greater flexibility of common rail allows the optimum injection pressure and injection timing to be selected and also permits pilot and post-injections ? irrespective of the engine speed. Particularly for engines operating at variable speeds, this technology has now become standard in modern automobile and truck diesel engines, of which MAN Nutzfahrzeuge?s D20 truck engine series is a recent development. With new requirements concerning nitrogen and soot emissions, the development of common rail technology for large medium-speed diesel engines now also represents a breakthrough in marine applications.

A common rail injection system capable of operating on heavy fuel oil and controlled by a solenoid valve, as applied in the new MAN B&W 32/40CR four-stroke engine, is said to now open up further possibilities.

MAN B&W?s common rail is based on well-proven, conventional components, that are said to make it particularly reliabile. The cylinder head including the injection nozzle and the high-pressure pipes remain unchanged. Also, the sensitive electronic components are located far away from the hot temperature zones and are easily accessible.

The MAN injection system functions by means of conventional injectors. Rather than working with stroke-controlled injection, the engine has conventional injectors so the pressure at the injection needle is released by means of a solenoid valve located away from the cylinder head. The full pressure is not permanently on the needle seat adjoining the combustion chamber and the electronic components are protected.

The entire common rail system is fully redundant which means that there is a backup for every significant mechanical and electrical component. There are at least two high-pressure pumps (as with the 32/40CR) to every engine, and three pumps for seven or more cylinders. This safeguards the pressure generation necessary for injection, even if one pump fails.

The new MAN B&W common rail technology has been extensively tested since the beginning of this year as one of the five auxiliary engines of the 6600 TEU container vessel Cornelia Maersk is equipped with the new technology. The engine is said to have performed “with convincing results for more than 1200 operating hours”. The 32/40CR series engine will be available from 2005 onwards with both larger and smaller types are in the pipeline. Its modular design, means that the MAN B&W common rail system can also be retrofitted in almost all MAN B&W marine diesel engines.