Reducing emissions by optimising the fuel injector match with the combustion chamber geometry for a marine medium-speed diesel engine

- An optimisation routine is shown to meet emission regulations and have best fuel economy.
- Injection-related parameters are more influential than combustion chamber geometries.
- Injection timing has the greatest impact on objectives, especially on NOx emissions.
- Low NOx emissions prefer a late injection and a low swirl.
- MOGA method is an effective way for optimising the matching problem of diesel engines.

The effects of seven matching parameters of a fuel injector and combustion chamber geometries on nitrogen oxide (NOx), soot and specific fuel oil consumption (SFOC) were investigated by means of a parametric study. The study was carried out on four different engine loads, i.e. L25 (25%), L50 (50%), L75 (75%) and L100 (100%) loads. The injection-related parameters were found to have more prominent influences as opposed to the combustion chamber geometries. Then, a multi-objective genetic algorithm (MOGA) method was proposed in order to identify a set of optimal designs for the L100 load. The emissions and performance of these optimal designs were also examined and compared on the other three engine loads. Finally, an optimal design which meets the IMO (International Maritime Organization) Tier II NOx emissions regulations (research shows it is impossible to meet Tier III NOx emissions regulations solely on the basis of the optimisation of the combustion progress) and which has the best fuel economy was singled out.

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