Thermodynamic and Optical Investigations on Particle Emissions in a DISI Engine at Boosted Operation

The subject of this paper is the reduction of the particle number emissions of a gasoline DI engine at high engine load (1.4 MPa IMEP). To reduce the particle number emissions, several parameters are investigated: the large scale charge motion (baseline configuration, tumble and swirl) can be varied at the single cylinder engine by using inlays in the intake port. The amount of residual gas can be influenced by the exhaust backpressure. By using a throttle valve, the exhaust backpressure can be set equal to the intake pressure and hence simulate a turbocharger's turbine in the exhaust system or the throttle valve can be wide open and thus simulate an engine using a supercharger. Additionally, higher fuel injection pressure can help to enhance mixture formation and thus decrease particulate formation. Therefore, a solenoid injector with a maximum pressure of 30 MPa is used in this work. The fuel composition also has a strong influence on the combustion process and on particulate formation. In this work, alkylate fuel is used to reduce the particulate number emissions at high engine loads. In-cylinder spectroscopic measurements and high-speed visualization techniques are applied in the combustion chamber of the engine and the results are combined with measurement data taken with an FTIR in the exhaust of the engine. A conventional exhaust gas analyzer is also employed and cylinder pressure indication supports thermodynamic analysis. This one-dimensional, three pressure analysis (TPA) is performed using GT-Power.