HCCI: The search for a better burn continues

A Bosch-led consortium sponsored by the U.S. DOE, and a research team at Sandia National Laboratories, are pushing to unlock the fuel-efficiency potential of the elusive homogeneous-charge compression ignition engine.

Homogeneous-charge compression ignition (HCCI) engines combine some of the combustion strategies of both diesel and spark-ignition (SI) engines in an attempt to achieve the high fuel efficiencies of diesels but without the oxides of nitrogen (NOx) and soot emissions they produce.

In a diesel engine, combustion begins when the fuel is injected with the piston near the top of the compression stroke and is controlled by the speed at which the fuel enters the chamber. By comparison, in a gasoline engine operating in HCCI mode the fuel has already been injected and mixed with air before the compression stroke begins. The dilute, premixed fuel/air charge then auto-ignites and burns “volumetrically” as a result of compression by the piston.