2008 年 43 巻 6 号 p. 858-863
The IMO NOx regulation Tier 1 for marine engines came into effect on May 19, 2005. Further, more stringent regulation IMO Tier 2 and Tier 3 will become effective in 2011 and in 2016 respectively. Tier 2 NOx regulation shall be reduced by about 20% and Tier 3 NOx regulation shall be reduced by 80% in Emission Control Areas. To comply with these regulations, recent 4-stroke engines have been developed mainly with consideration to the environmental, but also taking economy, durability and maintainability, etc. into account. A concept of simultaneous reduction of both of NOx and BSFC was established by simulation analyses and engine tests by the Niigata Comp. back in the 1990s. This concept has been adopted to our engines to comply with present regulation. Furthermore, other advanced technologies have been studied to comply with future legislation, especially for IMO Tier 2 and Tier 3. Strategies for future emission standards, through developments and studies, are described for the medium speed engines.