Modeling the performance of the piston ring-pack with consideration of non-axisymmetric characteristics of the power cylinder system in internal combustion engines

摘要

The performance of the piston ring-pack is directly associated with the friction, oil consumption, wear, and blow-by in internal combustion engines. Because of non-axisymmetric characteristics of the power cylinder system, the performance of a ring varies along its circumference. Investigating these variations is of great interest for developing advanced ring-packs, but is out of the capabilities of the existing two-dimensional models. In this work, three separate but closely related numerical models were developed to study the performance of the piston ring-pack. The model for static analysis was developed to facilitate the design of piston rings. In this model, a finite beam element model is adopted with incorporation of a physics-based sub-model describing the interaction between the ring and the bore as well as the ring and the groove. A step-by-step approach is adopted to calculate the ring/bore and ring/groove conformability if the free shape of the ring is given. A method that can be used to determine the free shape as to achieve a specific tension distribution is also developed. Model results revealed the complex ring/bore and ring/groove interaction. A three-dimensional model for ring dynamics and blow-by gas flow was developed to address non-axisymmetric characteristics of the power cylinder system. In this model, the rings are discretized into straight beam elements. 3-D finite element analysis is employed to address the structural response of each ring to external loads. Physics-based sub-models are developed to simulate each ring's interactions with the piston groove and the liner. The gas flows driven by the pressure difference along both the axial and circumferential directions are modeled as well.