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Mattia Contino
University of Naples, "Federico II", Naples, Italy

Alessandro Montanaro
Istituto Motori−CNR, Via G. Marconi 4, 80125, Napoli, Italy

Luigi Allocca
Istituto Motori−CNR, Via G. Marconi, Napoli, Italy

Gennaro Cardone
University of Naples, "Federico II", Naples, Italy

DOI: 10.1615/TFEC2018.emt.021990
pages 845-848

KEY WORDS: Spray-wall interaction, DISI engines, Thermal visualization.


Investigation about operating conditions in modern Gasoline Direct Injection (GDI) engines keeps awake the interest of car manufacturers in order to be respectful of the strict rules about pollutant emissions imposed by states' laws and regulations. It is well-known the strong influence of surface temperature on droplet-wall interaction and the resulting liquid film formation. On the other side, it is poor the quantitative knowledge about the temperature drop on impact zones and about detection of liquid and gaseous phases after the impact on piston head. The present study focuses on the application of infrared thermography about a multi-hole GDI injector generated spray impinging on a heated thin foil. Thermal images of the iso-octane fuel impacting on the heated thin foil are acquired at different delays starting from the impact time. Each acquisition is repeated in order to obtain phase-averaged images. A parametric study is driven about injection pressure at fixed wall temperature and nozzle-to-wall distance. The temperature difference maps and the temperature dynamic behavior on a single impact spot are presented. A threshold selection method (Otsu's method) is then applied on thermal images in order to distinguish the liquid wall film from the cooler dry regions. From temperature difference images, the temperature drop on the impact zones is of about 35°C starting from the first instants after the impact. As a matter, after about 0.5ms, the slipping of the fuel from the center of the impact area appears.

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