Direct measurement of piston friction of internal-combustion engines using the floating-liner principle

Piston–cylinder interactions account for a significant portion of frictional losses in an internal-combustion engine. This is mainly as the result of significant changes in the operating conditions (the load, the speed and the temperature) as well as the contact geometry and the encountered topography during a typical engine cycle. These changes alter the regime of lubrication which underlies the mechanisms of friction generation. The multi-variate interactive nature of the problem requires quite complex analyses which do not fully replicate the actual in-situ conditions. Therefore, there is a need for direct measurement of cyclic friction under controlled conditions. The paper describes the use of a novel floating-liner arrangement which is capable of direct measurement of friction, its transitory mechanisms, as well as determination of the regime of lubrication.