Effects of fuel injection parameters on performance and emissions formation in a large-bore marine diesel engine (original) (raw)

2010, International Journal of Engine Research

Reductions in the emissions of nitrogen oxides (NO x) and soot from marine diesel engines can be supported by employing multiple-injection strategies, similar to those used in automotive engines. In the present computational study, the possibility of improving the operation of a large two-stroke marine diesel engine at full load by implementing an appropriate pilot injection is explored. A KIVA-3-based computational fluid dynamics code is used, coupled with an evolutionary algorithm. Multi-objective engine optimization is performed by parameterizing the fuel injection profiles in terms of four design variables, which fully define the pilot and main injections. Two objective functions are defined: the final NO x concentration and the specific fuel oil consumption (SFOC), both normalized by the corresponding values of a reference case of continuous injection. Three problem setups have been considered: first, an unconstrained problem; second, a problem constrained by the maximum cylinder pressure; third, a problem constrained by both the maximum pressure and the minimum work output per engine cycle. It is found that, in both the unconstrained and the one-constraint problems, the optimum solutions are characterized by substantial improvements in the NO x emissions (of the order of 15-20 per cent) and the SFOC (of the order of 2 per cent). The improvements are less pronounced when both constraints are imposed. A detailed sensitivity analysis of the effects of each of the design variables is presented.

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