Recent Progress in HCCI Combustion for a Practical Usage as a Gasoline Engine
Gasoline engines are widely used for passenger cars as they feature low cost and clean exhaust gas with three way catalyst. As the number of cars is extremely increasing in the world, thermal efficiency in gasoline engines must be improved urgently with less expensive cost-up. To achieve this, downsizing with turbo charger is now getting popular while more improvement in thermal efficiency is required to meet future stringent regulations. Further downsizing causes issues to pre-ignition, knocking and ignition system which are very challenging to solve. The homogeneous charge compression ignition (HCCI) combustion system represents a promising and alternative combustion system to the spark ignition and has been studied by many engine researchers in the world owing to its inherent features of high thermal efficiency and low NOx emissions. The main issues of operating an engine in HCCI mode are the limited operational load range achievable and the difficulty in controlling ignition timing. Although many researchers have been studying this system to solve the challenging issues, the practical usage is still unclear.
The authors have developed the Blow Down Super Charging (BDSC) system and experimentally demonstrated wide load range HCCI operation. The concept of the blow-down supercharge (BDSC) system is to obtain a large amount of diluted mixture without an external supercharger for extending the high load operational limit of HCCI gasoline engines whilst keeping dP/d θ and NOx emissions low. A commercially available 2.0 L four-cylinder gasoline engine with a port fuel injection system (HONDA K20A) was used as a test engine.