The Effect of Contact Pressure on Piston Ring Twist

The paper is a step in an ongoing work targeted at the development of an engineering methodology to estimate sealing properties of a piston ring, and for the development of ring design guidelines. This work is necessary because the sealing properties of a ring significantly affect oil passing and blow by in the reciprocating air compressors and engines.

It is known that the sealing function of a piston ring depends on the ring's ability to elastically deform in its plane under its own tension by conforming to the deviations of the cylinder bore. At the same time, if it has an asymmetrical cross section, the ring fitted in the cylinder bore is subjected to the additional, three-dimensional, distortions called twist. This type of cross section is usually imparted to the ring to further improve its sealing functions by interlocking (because of twist) between the piston groove and the cylinder wall. However, there is no available engineering recommendation that relates ring design parameters to the twist.

This paper is an extension of the authors' previous works and demonstrates analytically the effect of contact pressure between the piston ring and cylinder wall on the piston ring twist, using the shape of the cross section and the mechanical characteristics of the ring as input.