18 Gasoline CAI and Diesel HCCI: the Way towards Zero Emission with Major Engine and Fuel Technology Challenges 2002-32-1787

Engines and fuels for transport as well as off-road applications are facing a double challenge:

• bring local pollution to the level requested by the most stringent city air quality standard
• reduce CO2 emission in order to minimize the global warming risk.

These goals stimulate new developments both of conventional and alternative engines and fuels technologies. New combustion processes known as Controlled Auto-Ignition (CAI™) for gasoline engine and Homogeneous Charge Compression Ignition (HCCI) for Diesel engine are the subject of extensive research world wide and particularly at IFP for various applications such as passenger cars, heavy-duty trucks and buses as well as small engines.

Because of the thermo-chemistry of the charge, the thermal NOx formation and the soot production are in principle much lower than in flames typical of conventional engines. Indeed, these new combustion processes bring NOx to virtually zero (“1 digit” ppm) while maintaining a very high thermodynamic efficiency of the combustion.

The control of such combustion is very complex due to the number of engine and fuel parameters involved. Consequently, scientific methodology is necessary to road map their development up to practical application. The purpose of this paper is to describe these new combustion processes, the scientific tools such as optically transparent engine for combustion diagnosis and the use of CFD modeling tools for understanding and mastering their development, and finally their possible application to small engine technologies.

A number of questions remain open by these combustion processes related to the future of after-treatments and fuel formulation. Fuel parameters such as the octane of the gasoline or the cetane of the diesel fuel which are key quality data for conventional combustion might not have similar value for CAI and HCCI combustion. One further view could even raise the question of one unique fuel for a unique combustion process.