سال انتشار: ۱۳۸۴

محل انتشار: چهارمین همایش موتورهای درونسوز

تعداد صفحات: ۱

نویسنده(ها):

V Hosseini – Alberta University, Alberta, Canada
Babak Omidi Kashani –
M.D Checkel –

چکیده:

Homogenous Charge Compression Ignition (HCCI) engines are defined as a hybrid of SI and CI engines. A mixture of homogenous air and fuel inducted into the cylinder (similar to SI engines) and ingites by compression (similar to CI engines). The combustion is dominated by auto-ignition rather than by flame propagation because the mixture initiates at several sites inside the cylinder and propagates through any remaining unburned mixture will small, local flames. Pressure rise tends to be sudden and the rate of heat release, it is required to induct mixtures which are highly diluted with excess air and residual exhaust gas (EGR). By eliminating part-load throttling and maintaining fast combustion, the thermal efficiency is higher than conventional engines. The highli diluted mixture and spontaneous combustion lowers the combustion temperature and as a result the oxides of nitrogen (NOx) output is minimal.
The problem of HCCI engines is combustion control. Since the combustion is spontaneous, there is no dorect control method for combustion timing. Also, the operating region is narrow, limited by severe knock at the rich side and misfire/partial burning at the lean side. The greatest challenge in HCCI implementation is to control the onset of combustion while expanding the operating region.
This paper examines the basic characteristics of HCCI combustion through experimental analysis in a single cylinder CRF engine. A comparison between SI and HCCI in terms of pressure trace, P-V diagrams, cyclic variation, heat release, efficiency and emission has been made. The results show the lower specific power output and narrow operating range of HCCI engine but also the promise of extremely low NOx emission in this restricted range.