The Hydraulics of Oil Scraping

This paper is a preliminary evaluation of theoretical models and a report of an initial series of experiments investigating the scraping effect and film-reducing capabilities of edges and sliders with cross sections similar to those of piston rings.

Three basic types of scrapers or sliders are described: the hydrodynamic wedge between inclined, straight, or curved surfaces; a parallel slider that also produces lift; and a blade without a nominal bearing width.

The theoretical treatment of an oil ring with two geometrically equal rails indicates that it will only scrape with its leading rail, while the trailing ran will ride a velocity wave without a scraping effect. The validity of this theory and its amplification has been experimentally supported.