Phenomenological Modeling and Experiments to Investigate the Combined Effects of High Pressure and Multiple Injection Strategies with EGR on Combustion and Emission Characteristics of a CRDI Diesel Engine

Nowadays, due to stringent emission regulations, it is imperative to incorporate modeling efforts with experiments. This paper presents the development of a phenomenological model to investigate the effects of various in-cylinder strategies on combustion and emission characteristics of a common-rail direct-injection (CRDI) diesel engine. Experiments were conducted on a single-cylinder, supercharged engine with displacement volume of 0.55 l at different operating conditions with various combinations of injection pressure, number of injections involving single injection and multiple injections with two injection pulses, and EGR. Data obtained from experiments was also used for model validation. The model incorporated detailed phenomenological aspects of spray growth, air entrainment, droplet evaporation, wall impingement, ignition delay, premixed and mixing-controlled combustion rates, and emissions of nitrogen oxides (NOx) and diesel soot. The detailed spray configuration provided an edge to the present model in predicting engine combustion and emission characteristics accurately. Results showed that a simultaneous reduction of NOx and soot is possible with an optimized combination of EGR and dwell period between multiple injections at high injection pressure particularly for low operating loads.