The oil film around a cylindrical micropore in a sliding contact visualized by fluorescence microscopy on a tribometer. (January 2022) - Cheong, Jiyeon
Abstract: This work presents the oil film near a single surface texture in an optically accessible sliding contact reproducing the piston-ring/cylinder-liner contact in an engine. A micropore – a cylindrical depression with vertical walls – was laser-textured into the surface of the quartz-glass liner. The oil film thickness is imaged quantitatively at high magnification via laser-induced fluorescence. The results show that the pore carries oil to the starved outlet, creating a downstream "oil tail", whose morphology and volume are analyzed. Specifically, at low speed, the pore has a wider tail containing a higher oil volume than at high speeds. These suggest that in a reciprocating piston engine, porosity on the liner can yield advantageous tribological behavior in particular around the piston-motion reversal points. Highlights: The oil film near a laser-textured „micropore" in sliding contact was imaged by quantitative fluorescence microscopy. Pore diameter and depth as well as sliding speed and normal load were varied. Each micropore formed a downstream "oil tail" in the contact, and the tail's morphology and volume were analyzed. A pore with 200 µm diameter, 20–40 µm depth and 0.1 m/s speed was most efficient in carrying the oil into the starved outlet. The results suggest that such pores may be particularly effective near the reversal points of reciprocating sliding contact.