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This study presents a methodology to predict particle number (PN) generation on a naturally aspirated 4-cylinder gasoline engine with port fuel injection (PFI) from wall wetting, employing numerical CFD simulation and fuel film analysis. Various engine parameters concerning spray pattern, injection timing, intake valve timing, as well as engine load/speed were varied and their impact on wall film and PN was evaluated. The engine, which was driven at wide open throttle (WOT), was equipped with soot particle sampling technology and optical access to the combustion chamber of cylinder 1 in order to visualise non-premixed combustion. High-speed imaging revealed a notable presence of diffusion flames, which were typically initiated between the valve seats and cylinder head. Their size was found to match qualitatively with particulate number measurements. A validated CFD model was employed to simulate spray propagation, film transport and droplet impingement.

Increasing oil prices and emission legislation have forced car manufacturers and suppliers to investigate new methods and technologies to improve the efficiency of current spark ignition engines. In order to follow these trends and to yield a contribution in the development of modern combustion concepts, spark plugs with improved ignition performance are required. Reliable ignition and inflammation in operating points employing stratified and lean air/fuel charge is thereby a challenging task. In this study we are using a full 3D model of the engine which is offering a possibility to conduct a virtual replacement of the spark plug. With this modeling concept we are able to investigate the influence of different spark plug designs on the ignitability of the air/fuel mixture at the ignition time.

The paper discusses spray characteristics of fuel injectors with multi-hole nozzle (MHI) for DISI engine applications with homogeneous combustion and optional turbocharger (down-sizing concepts). Depending on the engine's operating mode the predominantly influencing spray parameters change. Although several injection concepts are available for DISI engines multi-hole injectors provide high spray flexibility to meet the requirements. The work presents a methodology called spray targeting for adapting the MHI adequately to the engine and tap its full potential. This requires fundamental knowledge of the influencing parameters on spray formation. A study using a DOE approach is introduced to identify the main influencing parameters on spray characteristics, e.g. nozzle geometry, operating parameters, and injection timing parameters.