Abstract
To extend the available load range and obtain higher thermal efficiency in natural-gas PCCI engines, the strategy for controlling direct-injection combustion was discussed. Experimental results from single-cylinder engine tests show the possibility of extending load range by direct fuel injection. Reduced nozzle orifice size and reduced injection angle provide higher combustion efficiency; however, promotes knock because of the formation of locally rich mixture. From the discussions based on the prediction by CFD code considering mixture heterogeneity, it is suggested that controlling PDF of fuel concentration could be a means to control the rate of pressure rise.
