Shamit Bakshi

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.

The high-pressure multiple injections in common rail direct injection diesel engines offer a possibility of simultaneous reduction of exhaust smoke and oxides of nitrogen. The purpose of the present work is to develop a phenomenological model to enable parametric understanding of the combustion and emission characteristics of multiple-injection common rail direct injection engines. The model is based on a two-zone formulation comprising of fuel-air spray and the surrounding air. The model predictions for combustion and emissions are validated with measured results of different multiple-injection schedules available in the published literature. The effect of parametric variations of multiple-injection scheduling on emission characteristics are predicted using the proposed model. It is observed that the simultaneous reduction of oxides of nitrogen and smoke is possible with an optimized pilot fuel quantity and dwell between the injection pulses. © IMechE 2011.