Optimal Combustion Phasing Control of a Turbulent Jet Ignition Engine

The thermal efficiency of internal combustion engines can be affected by many factors. Combustion phase is one of these factors and attracted many researchers interest. Different from the conventional spark ignition engines, the combustion phase in turbulent jet ignition (TJI) engines is influenced by more control variables in both the pre- and main-chambers. Therefore open-loop map-based combustion phasing control becomes less robust to engine aging and requires more calibration effort for TJI engines. In this paper, a model based control strategy is proposed for a TJI engine using both the spark timing and the pre-chamber fuel injection quantity to regulate the combustion phase to the desired value. The feedforward controller is designed according to a previously developed TJI engine model. The feedback controller is a linear quadratic tracking controller considering output covariance constraint. With the proposed controller, the standard deviation of CA50 (crank location when 50% of fuel is burned) is reduced from 1.58 to 1.12 crank angle degree. Moreover, the proposed controller is able to achieve both fast tracking and good combustion stability, compared with the baseline controllers.