CFD investigation into diesel fuel injection schemes with aid of Homogeneity Factor

A modified parameter named "Homogeneity Factor (HF) of in-cylinder charge" has been introduced as a new measure for supporting the understanding of the air-fuel mixing and combustion process in diesel engines. The effects of this parameter on engine performance and pollutant emissions have been studied using various EGR and split injection schemes on a DI diesel engine. In this study, twelve different injection strategies for which two injection pulses with different fuel amount for each pulse (up to 30% for the second pulse) and different separation between two pulses (up to 30 degrees CA) were evaluated using CFD modeling. Results show the higher Homogeneity Factor will result in higher rate of air-fuel mixing and more complete combustion process. It was found when the dwell delay between injection pulses becomes longer, as it leaves more time for the air-fuel mixing during the late compression stroke, the maximum amount of Homogeneity Factor will be obtained at a later stage of combustion process and it can caused a reduction of NOx formation. This suggests, by optimizing split injection configurations accompanied with appropriate EGR rate, pollutant emissions can be decreased and controlled more accurately. (c) 2013 Elsevier Ltd. All rights reserved.