Analysis of Elastic Distortions of a Piston Ring in the Reciprocating Air Brake Compressor Due to the Installation Stresses

The objective of this paper is to present the results of an investigation of elastic distortions of split piston rings that are used in lubricated and non-lubricated air brake compressors. Concepts of advanced stress analysis and Finite Element Analysis (FEA) have been employed in this study.

The analysis of elastic distortions (twist) of piston rings due to the installation stresses has been quite poorly documented in the technical literature. As a result, unjustifiable engineering assumptions are some time made which result in misleading design solutions.

This paper demonstrates analytically and with the support of FEA the mechanical/geometrical parameters of a split ring which affect the twist of the ring during the installation in the cylinder bore, and the calculated magnitude of this twist along the ring circumference. This issue is addressed here, since ring manufacturers often propose an asymmetrical cross-section of a split ring as a way to obtain a controllable twist of the ring. This is done out of consideration that an expected ring twist would impart an edge contact of the ring with a cylinder bore that is beneficial for improvement of contact pressure of the ring and better sealing of ring/bore interface. This paper will help to quantify these industrial recommendations.

The results of a conducted investigation are important for design optimization of the piston rings from standpoint of control of gas flow and oil carry over.