An Experimental Study on the Effects of Three-Piece Oil Control Ring Design and Liner Finish on Lubricating Oil Consumption in a Hydrogen-Fueled Single-Cylinder Reciprocating Engine

Abstract

Reducing lubricating oil consumption (LOC) in reciprocating engines is an increasingly important objective in the pursuit of lower greenhouse gas emissions, longer maintenance intervals, and compliance with tightening environmental regulations. In 2022, the U.S. transportation sector alone was responsible for 29% of national greenhouse gas emissions, 87% of which originated from systems powered by reciprocating engines [1]. While significant progress has been made in fuel efficiency, oil consumption remains as a key contributor to carbon emissions. This research investigates the impact of design parameters in three-piece oil control rings (TPOCRs) and liner surface finish on oil consumption behavior.

Utilizing a hydrogen-fueled engine—where the only source of CO₂ emissions is from consumed lubricating oil—this study develops a high-fidelity, FTIR-based method for direct LOC measurement. A derivation of oil consumption based on air and fuel mass flow rates and measured CO₂ emissions is presented, alongside a sensitivity analysis which identified FTIR measurement uncertainty and ambient CO₂ variation as dominant error sources. All experiments were conducted at 2000 RPM under medium load (4 bar IMEP). The experimental results showed that under the tested condition, 1) increasing liner roughness increases the LOC and 2) changing the orientation of any rails with asymmetrical profile to favor up-scraping results in an elevation of LOC. Analyses applying liner vaporization and TPOCR models showed that the changes in liner oil film thickness brought by the TPOCR changes have negligible effect on the LOC from the oil evaporation. Increases in upper-rail up-scraping ability and the oil accumulation inside the TPOCR groove can both elevate the LOC although further investigation is needed to understand the oil transport paths leading to the LOC.

This work provides a foundation for future optimization of TPOCR design by highlighting key ring-liner interactions and oil transport mechanisms. Further study of asymmetric geometries and surface characteristics will provide further insights for reducing oil consumption in engine platforms.