An Investigation of Oil Supply Mechanisms to the Top of the Liner in Internal Combustion Engines

Protecting the piston ring and liner interface is critical to the proper operation of internal combustion engines. Specifically, the dry region, which is the portion of the liner above the Top Dead Center (TDC) of the Oil Control Ring (OCR), needs proper lubrication to reduce wear and to maintain sustainability. However, the mechanisms by which oil is distributed to such region have not been investigated. This paper presents the first attempt to understand dry region lubrication by means of the oil-gas interaction below the top ring gap through a combination of experimental and modeling approaches.

An optical engine with 2D Laser Induced Fluorescence (2D-LIF) technique was applied to visualize the oil flow below the top ring gap. It was observed that the two vortices downstream the top ring gap can cause oil bridging towards the liner, providing lubrication to the ring-liner interface. On the modeling side, a 3D machine learning model was developed to predict the vortex flow pattern for different pressure boundary conditions. It was found that the size and the strength of the vortex grows with increasing ratio of the upstream and downstream pressure. The combination of modeling and experimental results identified that oil bridged towards the liner by vortex is the major contributing factor to dry region lubrication.