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The present study extends the recently developed HIDECS-GA computer code to optimize diesel engine emissions and fuel economy with the existing techniques, such as exhaust gas recirculation (EGR) and multiple injections. A computational model of diesel engines named HIDECS is incorporated with the genetic algorithm (GA) to solve multi-objective optimization problems related to engine design. The phenomenological model, HIDECS code is used for analyzing the emissions and performance of a diesel engine. An extended Genetic Algorithm called the ‘Neighborhood Cultivation Genetic Algorithm’ (NCGA) is used as an optimizer due to its ability to derive the solutions with high accuracy effectively. In this paper, the HIDECS-NCGA methodology is used to optimize engine emissions and economy, simultaneously. The multiple injection patterns are included, along with the start of injection timing, and EGR rate.

The objective of this paper is to summarize experimental results which were previously reported by the authors and to derive many useful empirical equations concerning the diesel fuel sprays. The empirical equations for break-up length, spray angle, spray tip penetration and drop size distribution of the diesel sprays are introduced to discuss the internal structure of the spray. According to the effect of injection pressure and ambient pressure on the break-up length and drop size of the diesel spray, the spray structure can be divided into two categories; incomplete and complete sprays. The equations which express the break-up length and mean diameter of the incomplete and complete sprays were obtained using different techniques according for the dominance of one or more break-up mechanisms.