Feature 2 | MEDIUM-SPEED ENGINES
For the future, Rolls-Royce plans to add
a gas-fuelled version to the C-series range. First deliveries of gas-burning models of the in-line C-type are expected within two years. Te company has already achieved notable market successes in the small-ship field with K- and B-series Bergen medium- speed engines.
LEE technology Caterpillar’s MaK Low Emissions Engine (LEE) technology was extended during 2008 to the M32C medium-speed marine diesel series, ensuring compliance with the upcoming IMO II emission regulations. In addition to its application to new engines, LEE technology can be retrofitted to all existing M32C installations and to the other members of the latest generation of MaK medium-speed diesels, namely the M20C, M25C and M43C. Te first use of LEE was in a retrofit project, undertaken during 2007 on the M43C propulsion engine of a small chemical tanker. By combining an increase in
compression ratio with the adoption of the Miller cycle, NOx emissions can be reduced by as much as about 30% without sacrificing engine efficiency. However, to avoid consequential poor load pick-up and also visible soot emissions at part-load, the LEE concept uses proprietary Flexible Camshaſt Technology (FCT) to achieve low NOx emissions, good load pick-up and invisible smoke at all engine loads. FCT enables variation of the fuel system and the air system at part-load operation, and is claimed to reduce soot emissions at part-load by 75% while improving engine performance during transient operation. Caterpillar Motoren stated in September
2008 that existing engines of the latest MaK generation can be converted to LEE standard at about 15-20% of the cost of a new IMO II-compliant engine. It estimated that, by 2010, around half of all MaK M20C, M25C, M32C and M43C marine engines built would be of LEE design.
Power and safety Originally designed in the UK at the former Ruston works as the RK280 medium-speed engine, the improved 28/33D type is now produced by MAN’s fountainhead Augsburg plant in Germany. Te 28/33D is claimed to be the highest- powered engine of 1000rpm running speed available worldwide, and is offered in 12-, 16- and 20-cylinder configurations serving the 5400-9000kW output band. Due to its high power density, the design is finding favour in naval applications as well as in the commercial fast ferry market. Current orders from the naval domain
include shipsets of two such engines apiece for three patrol boats for Trinidad and Tobago, and four patrol boats for the Netherlands. Trinidad’s 90.5m offshore patrol vessels are to be constructed at VT Shipbuilding’s Portsmouth site for coastguard deployment. Each 25kt-capable newbuild has been specified with two 16V 28/33D engines, driving controllable-pitch propellers through reduction gearboxes. A new technological milestone in
the ongoing 28/33D development programme is MAN Diesel’s advanced, compact SaCoSone safety and control system, for direct mounting on the engine structure. Together with the 28/33D’s fuel injection system incorporating solenoid valve-controlled injectors, SaCoSone will
An engine of the HiMSEN H32/40 type at HHI-EMD’s Ulsan production facilities (credit: Hyundai Heavy Industries).
Caterpillar Motoren’s Kiel Engine Centre assembly hall, one of two German factories producing MaK medium-speed diesels (credit: Caterpillar).
allow very precise ‘shaping’ of the rate and timing of fuel injection and, hence, greater control over the combustion process. Tis technology will form an important aspect of the measures to remain within future IMO Tier II NOx emission limits. Te bid to ensure smoke-free exhaust gases under all operating conditions, moreover, has special significance for the fast ferry market and other spheres of passenger shipping.
Common rail injection Common rail injection is one of the key technologies that have transformed the four-stroke engine category in recent years. The system affords an unprecedented degree of flexibility to suit a ship’s varied operating profile and power demands, and allows for a better trade-off of NOx emissions versus engine efficiency. For example, combustion can be optimised to achieve lower exhaust emissions where local controls so dictate. As a pioneer in computer-controlled
common rail fuel injection systems for heavy fuel oil usage, Wärtsila has progressively extended the application of the technology through its medium-speed diesel range. Now the smallest engine in the portfolio, the 200mm-bore W20 series, is entering service in CR configuration. A significant difference in the W20CR relative to other Wärtsila medium-speed common rail engines is the location of the fuel pumps at the end of the engine. Tis has helped achieve a compact design.
26 Ship & Boat International March/April 2009
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