Two-stroke low speed diesels dominate the main propulsion engine market, being selected for nearly 80% of all ocean-going vessels. The main reason is the simplicity of the direct-coupled installation, the high reliability and the high thermal efficiencies. Four-stroke medium speed engines take the last 20%, except on the LNG carrier propulsion field where steam turbines, while being threatened, still prevail. The occasional exception to the above is a few gas turbines in passenger (cruise) vessels. Recently, two-stroke low speed diesels have been developed for electronically controlled fuel injection systems, and such engines are now gaining momentum in the industry. The electronically (rather than cam) controlled fuel injection systems bring with it many operational benefits, which will be outlined in the paper. One such feature is the ability to inject very small fuel amounts safely through the same injectors as those able for full power operation. This paves the way for a more simple and safe version of large low speed dual fuel gas engines for propulsion of LNG carriers, representing significant fuel and gas saving possibilities, reducing CO2 emissions, and also opening new frontiers for low emission high-efficiency ship propulsion systems in other vessel types, including the largest types, as well as land based power generation. The paper will outline the technology, especially with a view of emission control and its economical and environmental potential.

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