Multizone Phenomenological Modeling of Combustion and Emissions for Multiple-Injection Common Rail Direct Injection Diesel Engines

Common rail direct injection (CRDI) system is a modern variant of direct injection diesel engine featuring higher fuel injection pressure and flexible injection scheduling which involves two or more pulses. Unlike a conventional diesel engine, the CRDI engine provides simultaneous reduction of oxides of nitrogen and smoke with an injection schedule that has optimized start of injection, fuel quantity in each injection pulse, and dwell periods between them. In this paper, the development of a multizone phenomenological model used for predicting combustion and emission characteristics of multiple injection in CRDI diesel engine is presented. The multizone spray configuration with their temperature and composition histories predicted on phenomenological spray growth and mixing considerations helps accurate prediction of engine combustion and emission (nitric oxide and soot) characteristics. The model predictions of combustion and emissions for multiple injection are validated with measured values over a wide range of speed and load conditions. The multizone and the two-zone model are compared and the reasons for better comparisons for the multizone model with experimental data are also explored.