Investigating the EGR rate and temperature impact on diesel engine combustion and emissions under various injection timings and loads by comprehensive two-zone modeling

The impact of exhaust gas recirculation (EGR) on combustion and emissions in direct injection (DI) diesel engine is examined in a predominately computational study, where the influence of EGR rate and temperature at various injection timings and loads is addressed using an in-house, comprehensive, two-zone model of diesel combustion, which divides the cylinder contents into a non-burning zone (air) and another in which fuel is supplied from the injector and burned with entrained air from the air zone. The validity of model computations is assessed favorably against pertinent experimental data, such as cylinder pressure and HRR diagrams, and NO and soot emissions, generated in this laboratory with tests on experimental, single-cylinder, 'Hydra' diesel engine, and also with relevant literature data. Various EGR rates and temperatures at different injection timings and loads were undertaken in the analysis. The numerical results provide insight into the local combustion and emissions formation mechanisms, and improve the understanding of important parameters dictating their behavior under various operating conditions. These results may be used for optimizing the NO - Smoke trade-off and efficiency, and pave the way for discussing the implications on the use of diesel fuels with diverse properties when fueling EGR-equipped diesel engines. (C) 2018 Elsevier Ltd. All rights reserved.