Homogeneous charge compression ignition (HCCI) combustion: Mixture preparation and control strategies in diesel engines

At present achieving fuel economy and reducing emissions are the two main targets set by the automotive industries. Homogeneous charge compression ignition (HCCI) technology is believed to be a promising one to be applied in both spark ignition (SI) and compression ignition (CI) engines in the near future. However, some challenges such as compromise combustion phase control, controlled auto-ignition, operating range, homogeneous charge preparation, cold start and emissions of unburned hydro carbon (UHC), and carbon monoxide (CO) need to be overcome for successful operation of HCCI engine. Extensive research on HCCI combustion with a homogeneous fuel–air mixture preparation is going on throughout the world. This paper reviews the strategies of different external and in-cylinder mixture preparation methods which were adopted and proposed in the recent years. The different strategies of controlled auto-ignition by HCCI combustion are also discussed in this paper.