Effects of Multiple Injections on Engine-Out Emission Levels Including Particulate Mass from an HSDI Diesel Engine
Journal article, 2007
The effects of multiple injections on engine-out emissions
from a high-speed direct injection (HSDI) diesel
engine were investigated in a series of experiments
using a single cylinder research engine.
Injection sequences in which the main injection was
split into two, three and four pulses were tested and
the resulting emissions (NOx, CO HC and particulate
matter), torque and cylinder pressures were compared
to those obtained with single injections. Together
with the number of injections, the effects of
varying the dwell time were also investigated. It was
found that dividing the main injection into two parts
lowered the engine-out particulate and CO emissions
and increased fuel efficiency. However, it also resulted
in increased NOx emissions. Further, using
double injections reduced the peak rate of heat
release (RoHR) and increased RoHR in the later
stages of the combustion without changing the combustion
duration, resulting in a more even distribution
of RoHR during the combustion, which is believed to
be the main reason for the changes in fuel consumption
and engine-out emission levels. When the number
of injections was increased to three or four and the
dwell time was prolonged the RoHR decreased, the
combustion duration increased and the CA50 was retarded.
Consequently, NOx emissions were reduced
but the fuel efficiency also declined, and emissions of
particulate mater, CO and HC rose.