Study on Combustion and Emission Characteristics of CNG Fueled RI-Engine 2007-01-3621

Improving the traditional combustion process and finding an alternative fuel are the dominant target for the future internal combustion engines. Many automotive manufacturers have developed various novel engines, such as CVCC, GDI engine and HCCI (being on the research stage). On the other hand, CNG (compressed natural gas) is promising the alternative fuel for automotive engine to meet the high efficiency and low emission requirements. The objective of this study is to investigate the characteristics of the RI-CNG engine having a sub-chamber over the main combustion chamber. Numerous former studies on RI technique were carried out, such as the CVC (constant volume combustor) study and RI gasoline engine study, etc. Based on these studies, a single-cylinder direct injection diesel engine was modified into an experimental RI-CNG engine and an optimized sub-chamber was employed. Compared with RI gasoline engine, the RI-CNG engine has solved its fatal demerit, i.e. RI-gasoline engine can't scavenge the residual gas in the sub-chamber from the former cycle. But RI-CNG engine was fueled into the sub-chamber directly instead of port fuel injection. By the way, RI-CNG engine could improve combustion and engine cycle stabilities. Besides, emission characteristics of RI-CNG engine were investigated.