EXPERIMENTAL STUDY OF MICRO LUBRICATING OIL DROPLETS IMPACTING ADHERENT PARTICLES ON INCLINED WALL SURFACES

The presence of adherent particles on the metal wall during the impact adhesion process between trace lubricating oil droplets and the metal wall has a significant impact on the quality of lubricating oil film formation and the heat dissipation effect of the friction pair. The impact process of oil droplets and adherent particles on the inclined wall is observed and analyzed by high-speed camera experiments. The aim is to investigate the effects that oil droplet impact velocity, wall inclination angle and other factors have on the morphology evolution and spreading characteristics of oil droplets, as well as the dynamic characteristics of the adherent particles under the impact. The results reveal that the morphological evolution of oil droplets during impact spreading is jointly affected by factors such as wall inclination and impact velocity. Asymmetric spreading, unilateral neck jet fragmentation, or sliding spreading of wrapped particles may occur. When the particles don’t show significant slip along the inclined plane under the impact of oil droplets, an increase in the inclination angle promotes the spreading of the oil droplets forward, making it easier for a unilateral neck jet to break near the three-phase contact line at the leading edge. When particles slip, the slip velocity of particles increases with the increase of wall inclination angle, which shortens the length of the liquid film at the front end and suppresses the generation of jet phenomenon, resulting in the phenomenon of wrapped particles sliding and spreading. The impact speed has little effect on the variation of spreading factor during the post spreading process, while the maximum spreading factor during the pre-spreading process gradually increases with the increase of impact speed. The movement of particles attached to the wall is significantly affected by the impact velocity and inclination angle. An increase in the impact velocity or inclination angle can promote the sliding of particles wrapped in the impact oil droplets along the wall.