Reactivity of Particles from Gasoline Direct Injection Engine: Correlation of Engine Parameters and Particle Characteristics

With the introduction of the European emissions legislation for particle number and particle mass (Euro 6c stage), particulate emissions are currently a core issue in the development of Gasoline Direct Injection (GDI) engines. Due to the different mixing process of fuel and air GDI engines emit more particulates than engines with port fuel injection.The present development aims at the reduction of particulate emissions through exhaust gas aftertreatment, e.g. via gasoline particle filters (GPF). To minimize the technical complexity in the aftertreatment system the control of the burn-out of particulates within GPF has an enormous significance. The regeneration behavior of GPF is essentially dependent on the reactivity of the stored soot and its properties that in turn depend on the engine operation conditions. The main objective is the enhancement and control of the reactivity of the emitted soot particles by engine parameters.
The basic studies were carried out on a turbocharged 4-cylinder engine with direct injection by varying the engine operating parameters, e.g. engine speed, air fuel ratio, injection timing. The particles are investigated in terms of their reactivity, number and size distribution and microstructure by using thermogravimetric analysis (TGA-FTIR), engine exhaust particle sizer (EEPS) and high-resolution transmission electron microscopy (HR-TEM).
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The investigations show a direct and indirect impact of engine operation parameters on the soot reactivity and its properties. The results of the parameter variations showed that the reactivity of particles can be controlled and enhanced by the operation conditions of the engine. To maximize the soot reactivity further investigations must be performed.