Piston Ring Design Consideration

While the first step is analysis and simulation which include numerical analysis, stress analysis, dynamic analysis and etc.

The design of new piston rings and creation of design and production drawings is based on databases in which all the important dimensions and properties are collected and stored. On the basis of these files, which are continuously updated, piston rings are drawn directly using computer-aided engineering (CAE). In addition to dimensions, piston ring drawings also contain certain functional characteristics, such as the specific contact pressure, tangential force, and cross section of the piston ring.

Piston rings are subjected to the greatest stress during installation, when they are stretched over the piston. The installation stress during the expansion (Sa) needed for assembly and the stress that arises in the cylinder in the installed state affected by following factors: 

●installation stress (expansion for assembly)

●Young’s modulus of the piston ring material

●radial distance from the neutral axis to the ring running surface

●free gap in relaxed state

●gap clearance in installed state

●nominal diameter of cylinder liner

●radial dimension of piston ring

●installation opening

For complex piston ring cross sections, such as two-piece oil control rings, the stresses are typically determined by finite element analysis.

Using a numerical simulation, it is possible to analyze the interplay of piston rings, piston, and cylinder. The piston ring pack can be optimized, for example, with regard to blow-by and reduction of lubricating oil consumption. Such analyses are composed of thermal FE analysis of the cylinder; thermal FE analysis of the piston; computation of piston and piston ring dynamics; simulation of the engine cycle.