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Chemiluminescence and Fuel PLIF Imaging of Reactivity Controlled Compression Ignition (RCCI).
| Content Provider | Semantic Scholar |
|---|---|
| Author | Musculus, Mark Paul Blobaum Kokjohn, Sage L. Reitz, Rolf D. |
| Copyright Year | 2011 |
| Abstract | In recent years, many premixed compression ignition (PCI) strategies have demonstrated high-efficiency and low pollutant emissions. However, PCI operation is generally confined to low engine loads due to the rapid energy release resulting from volumetric combustion. Furthermore, the injection event is typically decoupled from the ignition event, which presents challenges for controlling the combustion phasing. One PCI strategy, dual-fuel reactivity controlled compression ignition (RCCI), has been developed to address the issues of combustion phasing and rateof-heat release control. The RCCI concept uses in-cylinder blending of two fuels with different auto-ignition characteristics to achieve controlled high-efficiency clean-combustion. Recent experiments conducted on an all metal heavy-duty diesel research engine have demonstrated that dual-fuel RCCI operation can offer high-efficiency with low engine-out pollutant emissions. However, the mechanisms controlling the energy release in RCCI combustion are not well understood. Accordingly, the present study explores the RCCI concept using an optically accessible, heavy-duty, single-cylinder research engine. The research engine is equipped with two fuel systems to allow for in-cylinder fuel blending. Iso-octane is delivered using a low-pressure (100 bar) gasoline direct injector (GDI) and n-heptane is delivered through a higher pressure (600 bar) common-rail (CR) diesel direct-injector. The first part of this study uses a CMOS high-speed camera to image the ensuing combustion luminosity, composed primarily of chemiluminescence. The chemiluminescence imaging shows that at the operating condition studied in the present work (4 bar IMEP and 1200 rev/min), ignition typically occurs first in the squish region. Subsequent combustion propagates inward towards the centrally mounted common-rail injector. The second part of this study investigates the charge preparation of the RCCI strategy using planar laser induced fluorescence (PLIF) of a fuel tracer under non-reacting conditions to image the fuel distribution prior to ignition. Ensemble-averaged fuel concentration measurements show that the fuel reactivity generally increases with increasing axial position from the common-rail injector. Thus, it appears that the ignition location is determined by a region of highfuel reactivity in the outer region of the combustion chamber. The observed progression of the reaction zone from the outer-to-inner region of the combustion chamber is at least partially controlled by the gradient in fuel reactivity. Corresponding author |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.ilass.org/2/conferencepapers/ILASS2011-168.PDF |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
