Modeling the root causes of engine friction loss: Transient elastohydrodynamics of a piston subsystem and cylinder liner lubricated contact

In this study, the contact conjuction of a piston ring-pack and rough out-of-round cylinder is modeled to analyze the sources of engine friction loss. To achieve this objective, computational tools that combine tribology and dynamics are used to evaluate the ring conformability, ring modal behavior, skirt secondary dynamics, transient elastohydrodynamics of the ring liner contact, skirt liner contact, asperity contact analysis to determine the boundary friction, ring–liner wear, and gas blowby. Initially, an iterative technique is developed to solve the combined Reynolds equation and equation of rheology. Discretized forms of these equations are iterated to determine the error convergence for the computed pressure. Cyclic variations in lubrication performance parameters, such as the minimum film thickness, film hydrodynamic pressure, asperity contact pressure, wear rate, gas blowby, and oil consumption, are computed and analyzed using separate plots.