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Determining locations at which knocking events appear frequently is a very important tool for optimizing the efficiency of S.I.-Engines. The knock behavior of two Direct-Injection Engines (one with wall guided fuel delivery - Mitsubishi GDI-engine - and a single-cylinder test engine with narrow arrangement of spark plug and injector) was tested and the location of appearing knocking was detected by the use of optical fiber technique. The optical investigations were conducted using a spark plug equipped with 8 optical sensors evenly distributed in a ring on the ground electrode of the standard spark plug. The intensity of flame radiation in the observing area of the optical sensors were measured. As knocking combustion produces pressure waves exciting gas oscillations, each compression of residual exhaust gas causes a steep increase of the measured flame intensity curve.

In this paper optical investigations of a gasoline direct injection engine with narrow spacing arrangement of spark plug and injector are presented. For the combustion analysis spectroscopy techniques based on the fiber technique are used. With this measurement technique information about soot formation and temperature progression in the combustion chamber is obtained. Furthermore a validation of numerical simulation of the stratified combustion with data obtained experimentally, is performed and discussed.

In this paper an estimation of efficiency potential of the engine process with Gasoline Direct Injection (GDI) is presented as well as both the advantages and todays problems of different mixture preparation concepts for the GDI engine. Furthermore examples of combustion analysis with optical measurement methods like Particle Image-Velocimetry (PIV) and spectroscopy techniques, which are important for future development steps in GDI, are shown and discussed. A validation of the numerical simulation of the stratified combustion process with data, obtained experimentally from a GDI engine, is performed and discussed. Consequently the combination of experimental and numerical methods provides both a better understanding of mixture preparation and combustion processes in GDI engines as well as an efficient development procedure for an optimized mixing and combustion process for future GDI engines.