PERFORMANCE AND EMISSION CHARACTERISTICS OF DUAL INJECTION IN COMPRESSION IGNITION (CI) ENGINE

The continuously stringent emission regulations and the fast depleting primary energy resources have forced the researchers to explore the environment friendly and more efficient combustion concepts. One such combustion concept called Homogeneous Charge Compression Ignition (HCCI) technology has shown promises to reduce oxides of nitrogen (NOx) and particulate matter (PM) emissions simultaneously while maintaining the thermal efficiency comparable with that of conventional compression ignition direct injection (CIDI) diesel engine combustion. But the main problems of HCCI are the combustion phasing and the ignition timing control. Recently, a combustion concept called compound HCCI or HCCI-DI has been presented, which is a compromise to full HCCI. In HCCI-DI concept, only a part of the total fuel inducted is premixed through port injection and the remaining part is injected directly into the combustion chamber. This mode can overcome the problems of the combustion phasing and the ignition timing control. The objective of the present study is to investigate the effects of the port injection timings on the performance and the emission characteristics of HCCI-DI combustion mode on a single cylinder CIDI engine. The fuel used for both port as well as direct injection is diesel. HC and CO and the NOx emissions for HCCI-DI mode were found to be higher, whereas the smoke emissions were found to be lower than those of conventional CIDI. For HCCI-DI, the indicated specific fuel consumption (ISFC) was lower, whereas the brake specific fuel consumption (BSFC) was higher relative to those of CIDI. The indicated thermal efficiency (ITE) and the brake thermal efficiency (BTE) were higher and lower respectively for HCCI-DI than those of CIDI mode.