Modeling the lubrication, dynamics, and effects of piston dynamic tilt of twin-land oil control rings in internal combustion engines

A theoretical model was developed to study the lubrication, friction, dynam ics, and oil transport of twin-land oil control rings (TLOCR) in internal c ombustion engines. A mixed lubrication model with consideration of shear-th inning effects of multigrade oils was used to describe the lubrication betw een the running surfaces of the two lands and the liner. Oil squeezing and asperity contact were both considered for the interaction between the flank s of the TLOCR and the ring groove. Then, the moments and axial forces from TLOCR/liner lubrication and TLOCR/groove interaction were coupled into the dynamic equations of the TLOCR. Furthermore, effects of piston dynamic til t were considered in a quasi three-dimensional manner so that the behaviors of the TLOCR at different circumferential locations could be studied. As a first step, variation of the third land pressure was neglected The model p redictions were illustrated via an SI engine. One important finding is that around thrust and anti-thrust sides, the difference between the minimum oi l film thickness of two lands can be as high as several micrometers due to piston dynamic tilt. As a result, at thrust and anti-thrust sides, signific ant oil can pass under one land of the TLOCR along the bore, although the o ther land perfectly seals the bore. Then, the capabilities of the model wer e further explained by studying the effects of ring tension and torsional r esistance on the lubrication and oil transport between the lands and the li ner. The effects of oil film thickness opt the flanks of the ring groove on the dynamics of the TLOCR were also studied. Friction results show that bo undary lubrication contributes significantly to the total friction of the T LOCR.