Parametric Evaluation of Design and Operating Conditions of a Low Temperature Combustion Diesel Engine through 3-D Simulation 2011-01-0825

A low temperature combustion (LTC) diesel engine has been under investigation for reduction of NOx and soot with acceptable compromise in the efficiency through modification of the combustion process. In this paper computational simulation is performed as a preliminary step for development of an LTC diesel engine for off-highway construction vehicles. Validation is performed for major physical models against measurements in LTC conditions. The conditional moment closure (CMC) is employed to address coupling between chemistry and turbulence in KIVA-CMC. The Kelvin-Helmholtz/Rayleigh-Taylor (KH-RT) model is employed for spray breakup and a skeletal n-heptane mechanism for both low and high temperature chemistry. Parametric evaluation is performed for design and operating conditions including EGR rate and injection timing. Results are obtained for efficiency, IMEP, CO, NOx and PM emissions at intake boost pressures of 1, 2 and 3 bar. A possible range of the LTC operation is identified with understanding of the relevant physical phenomena in the given engine conditions. It was possible to reduce both NOx and PM with a high EGR rate for the selected baseline condition of 2 bar boosting and 64% EGR rate of the test engine.