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Simultaneous Formaldehyde and Fuel-Tracer LIF Imaging in a High-Speed Diesel Engine With Optically Accessible Realistic Combustion Chamber
Technical Paper
2005-24-008
ISSN: 0148-7191, e-ISSN: 2688-3627
Sector:
Language:
English
Abstract
Simultaneous laser-induced fluorescence (LIF) imaging of
formaldehyde and a fuel-tracer have been performed in a high-speed
diesel engine. N-heptane and isooctane were used as fuel and
toluene was used as a tracer. This arrangement made it possible to
make simultaneous measurements of toluene by exciting at 266 nm and
detecting at 270-320 nm while exciting formaldehyde at 355 nm and
detecting at 400-500 nm.
The aim of this study is to investigate how traditional fuel
tracer and natural-occurring formaldehyde formed in the cool
chemistry are transported in the piston bowl. A range of ignition
delays were created by running the engine with different amounts of
EGR. During this sweep the area where the low-temperature reactions
take place were studied.
The measurements were performed in a 0.5-l, single-cylinder
optical engine running under conditions simulating a cruise-point,
i.e., about 2.2 bar imep. The ignition delay was elongated compared
to the normal mapping and the engine-out emissions of soot and NOx
were ultra-low.
It was found that the spatial location of LTR's does not
shift significantly for different EGR levels. The formaldehyde
signal overlaps the fuel signal in most cases before the onset of
the main heat release.