Abstract
The combination of physical models, such as a combustion model, a gas exchange model, etc., was proposed to obtain sophisticated combustion control in HCCI (Homogeneous Charge Compression Ignition) engines, which have variable intake, exhaust valve timing control systems and turbo-charging systems. Control strategies of cylinder air mass, air/fuel ratio (A/F), charge temperature, residual gas fraction which affect HCCI operation were investigated using simulations with a simple engine dynamic model (a
4-cylinder, 4-stroke engine with total cylinder stroke volume of 2000 cm 3 ). The combustion sub-model in the model estimated auto-ignition characteristics, torque and exhaust gas temperature. The gas exchange sub-model in the model estimated air mass and residual gas mass. Control variables such as fuel mass, intake valve closing timing (IVC) and exhaust valve closing timing (EVC) to keep HCCI operation stable were investigated. The strategies with which the control variables were determined according to operating conditions are very effective for HCCI operations not only in steady state conditions, but also in the transient conditions and can be used to extend HCCI operations to the region of high speed and high load.