Lubricant-Derived Ash – In-Engine Sources and Opportunities for Reduction

Diesel particulate filters (DPF) are an effective means for meeting increasingly stringent emissions regulations that limit particulate matter. Over time, ash primarily derived from metallic additives in the engine oil accumulates in DPFs. Lubricant-derived ash increases pressure drop and reduces fuel economy. After long time periods, the accumulation of ash may lead to irreversible plugging in DPFs, which necessitates periodic filter removal and cleaning. This thesis examines the sources for lubricant-derived ash in engines and explores potential opportunities to reduce ash emissions. The research studies changes in lubricant composition in the engine via advanced in-situ diagnostics and computer modeling of species transport in the power cylinder. These changes are directly related to ash emissions and the effectiveness of the lubricant in protecting engine components. In the first part of this thesis, sampling techniques are employed to determine the composition of the lubricant in critical locations in the engine system, where oil is lost by liquid oil consumption and vaporization. The first practical in-situ FTIR measurements of lubricant composition at the piston and liner interface are obtained with a novel diagnostics system employing Attenuated Total Reflection (ATR) spectroscopy. This information is used to create a mass balance for ash-related elements and a framework for modeling the distribution of ash-related species in the engine. In the second part of this thesis, a novel approach to condition the lubricant at a fixed station in the oil circuit is explored as a potential means to reduce ash emissions. This study examines the performance of an innovative oil filter that releases no additives into the lubricant, yet enhances the acid control function typically performed by detergent and dispersant additives. The filter has the potential to be used as a replacement for detergent additives in a lubricant formulation, or enhance additive effectiveness there-by allowing in an increase in oil drain interval. This research will assist in the development of new formulations for diesel lubricants that minimize detrimental effects on DPFs, while providing adequate protection to engine components. Thesis Supervisor: Victor W. Wong Title: Principal Research Scientist and Lecturer in Mechanical Engineering