Effects of Fuel Post-Injection on the Performance and Pollutant Emissions of a Large Marine Engine

Abstract

Emission reduction from marine engines can be supported by implementing multiple injection strategies. In the present study, the effect of fuel post-injection on the performance and exhaust emissions of a large two-stroke marine diesel engine is investigated by using computational fluid dynamics (CFD). An optimization procedure is formulated by coupling a KIVA-3-based CFD code with an optimization tool based on evolutionary algorithms (EAs). A fuel-injection profile consisting of two pulses (main and post-injection) is considered and parameterized in terms of four design variables. The specific fuel oil consumption (SFOC) and the final concentration of nitric oxides (NOX) and soot constitute the objective functions. Using a parametric study, two multiobjective optimization problems are formulated, an unconstrained and a constrained one; in the latter, the work output per engine cycle and the maximum in-cylinder pressure are the problem constraints. For both problems, significant reductions in pollutant emissions are attained, in comparison with a reference case characterized by continuous injection; for the constrained problem, the reductions reach 23 and 32% for NOX and soot, respectively.