Abstract:
In the present study, experiments of reactivity control
compression ignition (RCCI) combustion mode is
performed on a single cylinder automotive diesel engine
with development ECU (electronic control unit). For
achieving RCCI combustion mode, low reactivity fuel (i.e.,
gasoline/methanol) is injected into the intake manifold, and
high reactivity fuel (i.e., diesel) is directly injected into the
engine cylinder. Mass of fuel injection per cycle and their
injection events are controlled using ECU. This study
presents the experimental investigation on the effect of high
reactivity fuel injection timings on peak pressure rise rate
(PPRR) and combustion stability in RCCI engine. The
combustion parameters, i.e., PPRR, indicated mean effective
pressure (IMEP) and total heat release (THR) are calculated
from the in-cylinder pressure measurement data. In-cylinder
pressure is measured using a piezoelectric pressure transducer
installed on the engine cylinder head. A crank angle
encoder of 0.1 CAD resolution is used for determining the
crank position for cylinder pressure data logging.
In-cylinder pressure traces for 1000 consecutive engine
cycles are recorded for the investigation of cyclic variations
in IMEP, and THR. Statistical technique and wavelet transform
are used for combustion stability analysis. Wavelet
transform has a potential to analyze the non-stationary
signal in frequency as well as time domain simultaneously.
Diesel injection timing plays a significant role to achieve
stable RCCI operation and allows to operate an engine
within the limit of acceptable PPRR limit up to a specific
engine load-speed condition. Results indicate that the
advanced diesel injection timing leads to higher PPRR. The
IMEP time series data was also analyzed by fitting different
probability density functions. Generalized extreme value
(GEV) distribution is found to cover the entire range of
distribution shapes observed in IMEP ensemble at different
RCCI operating conditions.
