Paper Title
Understanding The Effects Of Residual Gas Trapping On Combustion Characteristics, Engine Performance And Operating Range In A HCCI Engine

In this study, experimental investigation was performed in order to determine the effects of residual gas fraction (RGF) using low lift cams in a single cylinder, four stroke gasoline HCCI engine. For this purpose, the test engine was equipped with variable valve lift mechanism including intake and exhaust cam with 5.5 and 3.5 mm valve lift. The experiments have been carried out to understand the effects of RGF with three pairs of cam mechanisms (IN 5.5-EX 5.5, IN 5.5-EX 3.5 and IN 3.5-EX 3.5). The test results showed the test engine was run between 800-1900 rpm at different air fuel ratios and inlet air temperatures on HCCI mode. It was found that IN 5.5-EX 3.5 cam mechanism presented the more reasonable results among the other cam mechanisms and HCCI operating range was extended when misfiring and knocking boundaries were examined. Higher RGF was obtained with IN 3.5-EX 3.5 cam mechanism. Indicated thermal efficiency was obtained 26.67 % for IN 3.5 EX 3.5 whereas 27.5 % for IN 5.5-EX 3.5 at stoichiometric ratio and 1000 rpm engine speed. As a result, it was seen that combustion phasing could be controlled with RGF and HCCI operating range could be extended trapping exhaust gases in the combustion chamber. Index Terms- HCCI, Combustion, Operating range, Residual gas fraction, Performance