Empirical investigation and control-oriented modeling of n-butanol HCCI for improving combustion controllability

Engines operating in homogeneous charge compression ignition exhibit high thermal efficiencies and ultra-low emissions; however, the lack of effective control over combustion timing prevents practical engine application. In this work, experiments are performed to address the combustion control challenges, and a control-oriented, physics-based combustion model is developed using the first law of thermodynamics and semi-empirical correlations to further improve the controllability. Compression ignition of port-injected n-butanol is investigated on an advanced single-cylinder research engine. An array of steady state experiments is performed to investigate the influence of fueling amount, boost pressure and exhaust gas recirculation on the ignition and combustion of n-butanol HCCI. Valuable empirical correlations between combustion characteristics and control measures are thereafter quantified through detailed data analysis. A control-oriented simulation model is developed and validated to capture the combustion timing and influence from control measures with adequate accuracy. Finally, the model is used to provide guidance of combustion control strategies for enabling n-butanol HCCI under challenging high load operations.