Modeling Inertia-Driven Oil Transport Inside the Three-Piece Oil Control Ring of Internal Combustion Engines

Abstract

The three-piece oil control ring (TPOCR), traditionally used in light-duty gasoline engines, is becoming a viable option for heavy-duty gas and hydrogen engines due to its ability to control lubricating oil consumption (LOC) under throttled conditions. Understanding the distribution of oil inside the TPOCR groove, as well as the effects of rail gap and drain hole positions, is critical for optimizing TPOCR and groove designs. In this work, a one-dimensional oil distribution model was developed to simulate inertia-driven oil transport in the TPOCR groove. A novel approach was proposed by first dividing the TPOCR into units composed of a pair of expander pitches. Then, the relationship between the oil outflow rate of the unit and its oil mass was established with the help of three-dimensional two-phase computational fluid dynamics (CFD) simulations. This relationship was then used to model one-dimensional oil transport along the circumference of the TPOCR groove. Incorporating the boundary conditions at the rail gaps and drain holes, this simple model can complete computations for 10,000 cycles within a few seconds, allowing for quick the evaluation of transient behavior and design iterations. Studies on low-load conditions show that the model, with reasonable adjustment for the boundary conditions, can match the oil distribution patterns observed in visualization experiments. This is the first step toward studying oil transport in the TPOCR groove before involving the effects of gas flows.