Homogeneous charge compression ignition: the future of IC engines?

The Homogeneous Charge Compression Ignition Engine, HCCI, has the potential to combine the best of the Spark Ignition and Compression Ignition Engines. With high octane number fuel, the engine operates with high compression ratio and lean mixtures giving CI engine equivalent fuel consumption or better. Owing to pre-mixed charge without rich or stoichiometric zones, the production of soot and NOx can be avoided. This paper presents some results from advanced laser diagnostics showing the fundamental behaviour of the process from a close to homogeneous combustion onset towards a very stratified process at around 20–50% heat released. The need for active combustion control is shown and possible means of control are discussed. Results with multi-cylinder engines using negative valve overlap, variable compression ratio, fast inlet temperature control as well as dual fuel are given.