Simultaneous Control of Air/fuel Ratio and Intake, Exhaust Valve Timing for HCCI Operation

The control strategies of auto-ignition for homogeneous charge compression ignition and controlled auto ignition operations were investigated using a simple engine model. The fluctuations of auto-ignition characteristics during transients in variable timing of exhaust and intake valves were analyzed. When the valve timing changed stepwise, the characteristics fluctuated and differed slightly from these in steady state conditions because combustion in the prior cycle affected the gas exchange in the next cycle. To reduce such fluctuations, the control strategies of cylinder air mass, residual gas mass, fuel mass, air/fuel ratio were investigated for a simple engine dynamic model (a 4-cylinder, 4-stroke engine with total cylinder stroke volume of 2000 cm³), which could simulate the dynamics of gas exchange during transient valve timing in a wide dynamic range.