| |
|
 |
Lund Institute of Technology,
Dept. Of Heat & Power
Engineering (LU)
 The
combustion engines division within the Department of
Heat and Power Engineering at the Lund Institute of
Technology has been a pioneer within the HCCI research
community. The HCCI research in Lund started already
in 1996, and Lund has been the research leader within
the field ever since. All the disciplines associated
with HCCI engine research are covered; basic experimental
work, engine control, laser based combustion diagnostics
and combustion modeling based on chemical kinetics.
Basic Experimental Work
An extensive investigation into how various fuel properties
affect the HCCI combustion has been performed resulting
in an operating surface in the space of intake temperature,
fuel octane rating and compression ratio. The influence
of Exhaust Gas Recirculation (EGR) has also been studied.
Crevice volumes and their influence on combustion and
unburned hydrocarbon emissions has been studied showing
that most of the unburned hydrocarbons from HCCI combustion
comes from crevices. The combustion retarding influence
of turbulence has been studied and a conceptual model
taking this into account has been formulated. Recent
engine experiments with multiple pressure sensor locations
within the combustion chamber have provided insight
into how homogeneous HCCI combustion really is. Current
similar multi-point measurements of ion current should
provide further insight into the inhomogeneity of the
combustion process.
Engine Control
Since HCCI combustion lacks a direct means of combustion
initiation, unlike SI and Diesel engines, closed loop
combustion control is important in order to maintain
desired combustion phasing. The worlds first HCCI engine
operating under closed loop combustion control was a
modified Scania heavy-duty engine. Since then a number
of studies have been performed. The first observation
of unstable HCCI operation was also made in Lund. The
instability is caused by thermal interaction between
the cylinder charge and the cylinder walls. The feasibility
of using ion current measurements for combustion phasing
feedback has also been studied and the results have
been accepted for publication. Recent system identification
studies aim at constructing dynamic HCCI models for
improved control system design. Further studies on this
subject have also been submitted for publication.
Laser Based Combustion
Diagnostics
Pioneering work has been conducted on near-wall chemiluminescence
imaging showing that HCCI combustion consumes the fuel
all the way to the cylinder walls which is very important
when shrinking the size of the combustion chamber. Fuel
and OH LIF measurements have been performed showing
the heterogeneity of the HCCI combustion even with perfectly
homogeneous charge. Time resolved LIF measurements using
multi-YAG laser setup allowed crank angle resolved imaging
of HCCI combustion. Same technique was also applied
for one-shot 3D-imaging of the fuel distribution during
HCCI combustion. Of interest is also some two-stroke
work which has been conducted where a chain saw engine
was converted for optical access through the cylinder
head as well as through the exhaust ports. SI as well
as HCCI operation with optical access at 17000 RPM was
demonstrated.
Combustion Modeling based
on Chemical Kinetics
Pioneering work has been conducted in the area of HCCI
combustion modeling. Recent work has focused on integrating
chemical kinetics code with engine cycle simulating
software such as GT Power. Much effort has also been
put into efficient reduction of the chemical combustion
mechanisms. |
|
|
