DYNAMICS AND CONTROL OF DI AND HCCI COMBUSTION IN A MULTI-CYLINDER DIESEL ENGINE

Homogeneous Charge Compression Ignition (HCCI) is a new combustion concept that, in the last few years, has attracted more and more attention for its potential to reduce NOx and PM emissions without penalizing the engine efficiency. HCCI is a viable technology that combines the advantages of both compression ignition and spark ignition engines to meet future stringent emissions regulations. It can be accomplished using both gasoline and Diesel fuels, and it is based on the combustion of a homogeneous charge without using external ignition devices. Because of the great complexity of the control issues related to this process, further investigation is still required to apply the technology to automotive engines. The present work deals with a novel engine concept based of integrating the traditional Common Rail direct injection with an innovative external injection based on a highly effective atomization device. An optimized control of these injection strategies allows the engine to run in pure HCCI mode at low loads, with a consistent reduction of exhaust emissions, as well as in conventional DI mode at high loads without compromising performance. In addition, the possibility of simultaneously controlling both injection modes allows an operating range where the advantages of HCCI can be extended to medium loads. The paper presents an experimental analysis that proves the effectiveness of this new concept and constitutes a valid reference for further modeling and control studies.