Ultrasound for the non-invasive measurement of IC engine piston skirt lubricant films

Measurements of piston skirt film thickness in-recoprocare are relatively scarce and generally require significant modification to a test engine. However, the trend of engine original equipment manufacturers to downsize capacities whilst maintaining power outputs, increases the demands placed on the piston components. As a result, the relative pressure loading on the piston skirt is increasing and requires that lubrication be optimised to maintain low friction. This paper outlines experimental skirt film thickness measurements obtained from a fired single cylinder engine using reflected ultrasound. The profile of the film structure is observed and an insight into some of the motions of the piston can be determined. This study shows that quantitative film thickness measurements can be made using ultrasound and which are comparable with other established techniques.