Optimizing HSDI Diesel Combustion and Emissions Using Multiple Injection Strategies

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Optimizing HSDI Diesel Combustion and Emissions Using Multiple Injection Strategies

Reitz, Rolf D. / Liu, Yi

Multiple injection strategies have been experimentally and computationally studied for simultaneously reducing diesel engine NOx and particulate emissions. However, injection strategies featuring three or more pulses per engine cycle have not been sufficiently studied previously. The large number of parameters to be considered, in addition to the complicated interactions among them, challenge the capability of experimental hardware, computational models, and optimization methods. In the present work, multiple injection strategies including up to five pulses per engine cycle, are computationally investigated to optimize High Speed Direct Injection (HSDI) diesel engine combustion and emissions at a single part-load operating condition. The KIVA-3V code coupled with a Genetic Algorithm were used as the modeling and optimization tools, respectively. It was found that widely separated injection with two-stage combustion appears to provide optimal HSDI diesel performance at part load. More pulses per engine cycle can lead to better engine performance through the increased flexibility and control over the heat release and fuel/air mixing. With multiple injections, traditional diesel combustion phasing provides little advantage in engine performance, especially in the resulting high NOx emission levels.