Optimization of Injection Characteristics in a Large Marine Diesel Engine Using Evolutionary Algorithms

The reduction of pollutant emissions of marine diesel engines can be achieved by employing multiple injection strategies, similar to the ones used in automotive engines. In the present work, the options for advanced injection strategies, in terms of pilot injections, are explored for a large two-stroke marine diesel engine operating at full load, by utilizing Computational Fluid Dynamics simulations coupled with an Evolutionary Algorithm. The goals of the present Multi-Objective constrained optimization are the minimization of nitrogen oxides (NO_x) emissions and engine specific fuel consumption. The constraint, imposed by structural limitations of the engine, is the maximum cylinder pressure. The design variables include parameters controlling the pilot and main injections, and the injected total mass. The problem is handled as a Multi-Objective Optimization Problem, and the final set of elite solutions is identified based on the Pareto dominance. The methodology yields two families of solutions, corresponding to early and late pilot injection, providing significant improvement, both in terms of NOX emissions and engine efficiency. The elite solutions are analyzed and interpreted by detailed processing of the simulation results.