HCCI Engines

Engines

J.P. Angelos, W.H. Green, M.A. Singer
Collaboration with W.K. Cheng
Sponsors: Ford Motor Co., BP

Homogeneous charge compression ignition (HCCI) engines have the potential for high efficiencies and low pollutant emissions. By comparison with spark ignition (SI) engines, for example, HCCI engines can yield a 15-20% increase in fuel economy while emitting lower levels of oxides of nitrogen (NOx). HCCI engines can also achieve thermal efficiencies comparable to diesel engines yet maintain near zero levels of particulate emissions. Despite these advantages, however, a number of technical issues must be resolved before HCCI engines become mainstream. Many of the complications stem from the fact that HCCI enginesĀ are more sensitive to the details of the combustion chemistry than SI and diesel engines. Hence, without a solid understanding of the physical and chemical processes taking place in HCCI engines, it is difficult to develop practical, efficient, and robust engines.

We are developing a fast, full-cycle HCCI engine simulator for gasoline engines that is fully automated and uses detailed chemical kinetic mechanisms. The simulator, which we call MITES (MIT Engine Simulator), is run on a desktop PC and is capable of using chemistry models that contains over 1000 species undergoing more than 4000 reactions (e.g., the mechanism for primary reference fuels). We are using the simulator to characterize the operating range of HCCI engines and to investigate the impact of transients (e.g., speed, fueling, valve timing) on engine performance.

In addition to the modeling and simulation efforts described above, we also partake in a complementary experimental program. In close collaboration with colleagues in the Sloan Automotive Laboratory at MIT, we are using experimental results to validate MITES and to gain further insight into engine design and performance characteristics. By combining experimental and numerical approaches, we seek to understand and control the physical mechanisms that underlie HCCIoperation. In doing so, we move closer to developing a robust prototype that demonstrates the feasibility of HCCI engines in the marketplace.