Abstract:
Increase in the air pollution has driven the research towards
the cleaner combustion technology for reciprocating
engines. To tackle the challenge of the trade-off between
the NOx and soot emissions from a conventional diesel engine,
premixed low-temperature combustion (LTC) strategies are
potential technologies. Among the LTC strategies, reactivity
controlled compression ignition (RCCI) strategy has a better
combustion phasing control along with higher fuel conversion
efficiency and lower NOx and soot emissions. The present
study investigated the nano-particle emissions from RCCI
engine fueled with a port injection of gasoline/methanol (low
reactivity fuel) and direct injection of diesel (high reactivity
fuel). The RCCI combustion experiments were performed on
a modified single cylinder compression ignition engine with
development ECU. The mass of injected fuel per stroke for the
port as well as the direct injection is controlled through ECU.
A differential mobility spectrometer (DMS) is used for the
measurement of particle concentration along with their
size-number distribution (particle mobility diameter range:
5 nm to 1000 nm). The effect of single and double injection
strategy of high reactivity fuel on particle emission has been
investigated at constant engine load for gasoline/diesel and
methanol/diesel RCCI combustion. The results indicate that,
in RCCI combustion strategy, the nucleation mode particles
are in relatively higher concentration as compared to accumulation
mode particles. Most of the particles emitted from
the RCCI combustion are in size range of 5 nm to 300 nm,
and large size particles (500 nm to 1000 nm) are also emitted
in significant concentration. In double diesel injection
strategy, the nucleation size particles are significantly higher
as compared to the single diesel injection strategy the while
accumulation mode particles are relatively lower. Results also
depict that the diesel injection timings has no significant effect
on the particle mass having a diameter less than 20 nm for
gasoline/diesel RCCI operation. However, the mass of the
particles above the 20 nm diameter range increased with
advanced diesel injection timing.
