Two-stroke electronically controlled engines have been successfully introduced in the marine segment, powering a large number of merchant vessels in the last decade. The fuel and exhaust valve actuation systems are key characteristics of this technology. From Wärtsilä side, the RT-flex family of engines has been designed, providing performance and operational advantages to ship owners and operators alike. The engines are equipped with an accumulator type fuel system where the injection pressure and start of injection can be individually selected at each operational point. Moreover, the timing of the exhaust valve movement is fully controlled through a dedicated actuation system providing additional operational flexibility. It has already been demonstrated that this flexibility provides significant advantages throughout the engine operational envelope. This flexibility will become even more significant in the future as the variability of fuel types and fuel quality are increasing and the exhaust gas emission legislation becomes more severe. Based on the current field experiences and the available technological advancements, new system architectures are proposed in the 30 cm to 50 cm bore segment. The systems are designed for low lifetime costs and high reliability. Stringent emission requirements can be fulfilled, with the engines fully prepared for future IMO Tier 3 emission legislation, without modifications of the above mentioned systems. Additionally, it is possible to make full use of existing system components and sub- systems which have demonstrated reliability and lifetime in other marine applications, using the same type of marine fuels and at severe operational conditions. This is important due to the challenging development schedules for the systems of new engine programs. The fuel system is characterized by: Two injectors per cylinder, each with embedded single circuit solenoid valve; Injection timing and quantity control embedded in the injector; An accumulator (common rail) system based on a volume optimized, multi- element, double wall rail; A fuel supply system based on engine driven, inlet throttle controlled, multi- element pumps validated for two- stroke applications; System pressure which is potentially up to 50 % higher than those currently applied on two- stroke engines. The exhaust valve actuation is characterized by: A 300 bar servo- oil actuating medium; Optimized solenoid valve actuation allowing continuous control of exhaust valve closure. Both fuel and valve actuation systems are supported by a new electronic control system. The proposed paper presents our experiences from the development of these critical systems by providing a detailed insight on the following: The market requirements and their fulfilment; The advancement between the current RT- flex technology on larger bore segments and the new system; The major sizing, design and development challenges; The hydraulic system analysis used for the complete, multi- cylinder engine; The system integration at engine level; The overall system and component performance.
A new fuel injection and exhaust valve actuation system for a two-stroke engine family in the 30 to 50 cm bore segment
2010
16 Seiten, 35 Bilder, 4 Tabellen, 5 Quellen
Aufsatz (Konferenz)
Datenträger
Englisch
Direct fuel injection for two-stroke SI engine exhaust emissions abatement
Kraftfahrwesen | 1986
|A study of exhaust emission control for direct fuel injection two-stroke engine
Kraftfahrwesen | 1999
|Engineering Index Backfile
|Engine combustion at large bore-to-stroke ratios
Tema Archiv | 1978
|New two-stroke small-bore engine from Mitsibishi
Tema Archiv | 1991