1998-02-23

Improvements of GDI-Injector Optimization Tools for Enhanced SI-Engine Combustion Chamber Layout 980494

The suggestions for upcoming Euro 2000 clean air act puts an increasing legislative pressure for lower specific fuel consumption in order to reduce the emission of CO2 and thereby decrease the impact of the “green house” effect. One of the possible suggestions to meet these requirements for SI-engines is the gasoline direct injected (GDI) power unit.
One of the key points of the success of a layout of a GDI system is the optimization of the fuel injector and combustion chamber charge formation parameters. A brief description of the basic GDI-system used during the study is given. Hereafter are outlined the computational and experimental optimization tools which have been used to produce, on a reasonable industrial time scale, the main indications to optimize the design of a given injector/chamber configuration.
The paper discusses in detail the results produced by the latest enhancements introduced into the 3D multi-phase computational approach, NCF-3D. These are a fully implemented combustion sub-model as well as a sub-model for an auto-ignition mechanism.
Three different injector nozzle geometries are evaluated in the same combustion chamber. The computional and experimental results, obtained with different injector positions, are compared for the given combustion chamber of a 4 cylinder 16 valves 2 liter engine.
An alternative ignition strategy, the multi-spark concept, is discussed.

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