A practical Gasoline Compression Ignition (GCI) concept is presented that works
on standard European 95 RON E10 gasoline over the whole speed/load range. A
spark is employed to assist the gasoline autoignition at low loads; this avoids
the requirement of a complex cam profile to control the local mixture
temperature for reliable autoignition. The combustion phasing is controlled by
the injection pattern and timing, and a sufficient degree of stratification is
needed to control the maximum rate of pressure rise and prevent knock. With
active control of the swirl level, the combustion system is found to be
relatively robust against variability in charge motion, and subtle differences
in fuel reactivity.
Results show that the new concept can achieve very low fuel consumption over a
significant portion of the speed/load map, equivalent to diesel efficiency. The
efficiency is worse than an equivalent diesel engine only at low load where the
combustion assistance operates.
In this work, a detailed, dynamic longitudinal simulation model was created that
allows accurate CO2 emission and fuel consumption predictions for a
typical C-segment vehicle in the New European Drivecycle (NEDC), Worldwide
Harmonized Light-Duty Test Cycle (WLTC) and Real Driving Emissions (RDE) driving
cycles. Modelling and simulation were performed in the GT-Suite simulation
environment.
The vehicle simulation for the NEDC with its low load demand shows that the
outstanding fuel consumption at higher engine loads is more than compensated by
the poor efficiency at lower engine loads. For the WLTC and RDE cycles, the fuel
consumption improves relative to the NEDC due to the higher average load. In
order to take better advantage of the GCI concept’s performance at high loads, a
virtual engine map for a 4-cylinder engine was also created that is capable of
running in cylinder deactivation mode. Avoidance of low-load operating points in
this way leads to a significant improvement in cycle efficiency