Prevention of Fuel Film Formation by Ultrasonic Activation of the Fuel Impingement Surface

This study considers one of the challenges that arise during conversion of gasoline SI engines to 'heavy fuel' feeding - worsening engine performance because of intensive fuel film formation on inner surfaces of the intake manifold. A main goal of this study was investigation of an interaction process of a single fuel drop and a fuel jet with the impingement surface. Ultrasonic (US) oscillation of the latter was applied to prevent fuel film formation. Diesel fuel was chosen for our experiments because it causes more problems of mixture formation in SI engines. In the series of experiments with a single drop, effects of the drop size, ultrasound performance and a type of the impingement surface on the drop behavior were studied using a high-speed photography. In experiments with a fuel jet the phenomena of fuel film formation and size distribution of the impinging and reflected droplets were studied using a high-speed photography and PDPA/LDV technique. Obtained results showed a possibility of preventing the diesel fuel-film formation by US-activation of the impingement surface at different impingement angles, as well as in the case of a static fuel film. Sauter mean diameter (SMD) of the reflected droplets was found to be 80-110 m and does not differ considerably from SMD of drops colliding with an activated as well as with a non-activated surface.