Ultrasound for the non-invasive measurement of internal combustion engine piston ring oil films

Increasingly stringent legislation controlling vehicular emissions is motivating research to maximise engine efficiency. The frictional power loss associated with the ring pack–cylinder interface is one such focus. In addition to this, increased reliance on simulation to predict the lubrication characteristics requires that numerical codes model the physical situation accurately and reliably. Experimental validation provides the crucial role of assessing performance and lubricant film thickness provides a key comparable parameter. This paper outlines oil film thickness results obtained from the compression ring–cylinder interface of a fired, single-cylinder gasoline engine using a method based on ultrasonic reflection. The magnitudes of the film are discussed and compared with work published by other experimental investigators using alternative techniques.