Computational Study of Injection Rate-Shaping for Emissions Control in Diesel Engines

Present paper discusses the advantages and disadvantages of fuel injection rate shaping for a medium-duty diesel engine using computational analysis. The analysis was performed using three-dimensional (3D) Computational Fluid Dynamics (CFD) code KIVA-3V. Fuel injection rate-shape is parameterized and a Design of Experiments (DoE) is constructed. CFD simulations are performed at discrete DoE points to construct a statistical model, which is then used to predict the engine response for variation in injection shape parameters. Trends of NOx, soot, noise and Indicated Mean Effective Pressure (IMEP) are investigated to understand the impact and potential of injection rate-shaping on engine performance. It is found that slow increase in injection rate leads to reduction in NOx and IMEP, but has almost no effect on soot emissions. Effect of rate shaping during fall of injection rate does not show strong influence on emissions and performance. Effects of injection rate-shaping are found to be more significant at advanced injection timings compared to the retarded injection timings. Also, engine performance is more affected when rate-shaping is performed at higher injection pressures.