Combustion control of a small HCCI engine fuelled with DME using hot and cold EGR gas

Abstract

One of the main challenges with HCCI engines is structuring thhe systems to control combustion phasing to conduct the stable HCCI operation. Though some HCCI combustion control systems have been suggested, these systems are heavy and have the complex mechanism. In this study, for the development of a small HCCI engine fuelled with DME, a simple HCCI combustion control system was structured, and the control system and the algorithm were evaluated experimentally. In the control system, the ratio of three gases (stoichiometric premixture, hot EGR gas and cold EGR gas) was controlled by throttles. The result showed that combustion phasing was able to be controlled by changing the ratio of hot EGR gas and cold EGR gas with throttles in order to adjust mass-averaged in-cylinder gas temperature at intake valve closure. And IMEP was feedback (PI) controlled by fuel flow rate, and combustion phasing and equivalence ratio were feedback (PI) controlled by throttles. As a result, it enabled them to track the desired values.