IFP Energies Nouvelles Approach for Dual Fuel Diesel-Gasoline Engines 2011-24-0065
Compared to Spark Ignition (SI) engines, Compression Ignition
(CI) engines are more efficient because of the higher compression
ratios and leaner operation. However, thanks to stoichiometric air
fuel ratio, SI engines allow efficient pollutants after treatment,
particularly for NOx emissions. In this context, IFP Energies
nouvelles (IFPEN) has developed the concept of diesel-gasoline
combustion in order to combine the advantages of both fuels and
both combustion processes.
Focusing on a passenger car application, experiments have been
performed using a modified DI turbocharged small diesel engine (the
combustion chamber has been redesigned and port fuel injectors have
been added). In-Cylinder Fuel Blending (ICFB) using
port-fuel-injection of gasoline and optimized direct injection of
diesel was used to control combustion phasing and duration. This
modified engine can still run on diesel alone. ICFB mode is
considered, either with a lean mixture, or at stoichiometric
air-fuel ratio to perform NOx aftertreatment via a 3-way catalyst.
The objective is to control the NOx emissions over the whole
operating range of the engine, while maintaining attractive fuel
efficiency.
In this paper, IFP Energies nouvelles describes the main results
of diesel-gasoline combustion, in order to understand what would be
the best approach in terms of technological feasibility, fuel
efficiency and pollutant emissions. The potential of the dual fuel
concept has been investigated on several part load operating
conditions, focused on a 2000 rpm engine speed. The operable range
of load in ICFB combustion is extended from 7 to 16.5 bar IMEP.
BSFC at part load is as low as that of a diesel engine. At higher
load, NOx emissions are very low (≺0.5 g/kWh at 10 bar IMEP) and
allow lean mixture operation until 14 bar IMEP. Outside of this
ICFB operating range, the performance in full diesel mode remains
totally acceptable.