Cylinder liner rotation (Rotating Liner Engine, RLE) is a new concept for reducing piston assembly friction in the internal combustion engine. The purpose of the RLE is to reduce or eliminate the occurrence of boundary and mixed lubrication friction in the piston assembly (specifically, the rings and skirt).
This paper reports the results of experiments to quantify the potential of the RLE. A 2.3 L GM Quad 4 SI engine was converted to single cylinder operation and modified for cylinder liner rotation. To allow examination of the effects of liner rotational speed, the rotating liner is driven by an electric motor. A torque cell in the motor output shaft is used to measure the torque required to rotate the liner. The hot motoring method was used to compare the friction loss between the baseline engine and the rotating liner engine. Additionally, hot motoring tear-down tests were used to measure the contribution of each engine component to the total friction torque.
The cycle-averaged motoring torque of the RLE represents a 23∼31% friction reduction compared to the baseline engine for hot motoring tests. In both cases, the 4 cylinder engine has only one piston, so the percentage friction reduction is a bit misleading. It is estimated that the friction reduction due to liner rotation would be 37.5-42.5% with all four pistons for hot motoring experiments. For firing operation, the benefits of liner rotation would be even more significant. Through tear-down tests, it was found that the piston assembly friction of the baseline engine is reduced by 90% at 1200 rpm and 71% at 2000 rpm through liner rotation.