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.