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Experimental and Numerical Investigations on the Mechanisms Leading to the Accumulation of Particulate Matter in Lubricant Oil
Abstract:
The accumulation of particulate matter in lubricant oil can become an important issue in Diesel engines where large amounts of Exhaust Gas Recirculation (EGR) are used at medium to high load operating conditions. Indeed, the transport and subsequent accumulation of particulate matter in the engine oil can negatively impact the oil lubricant properties which is critical to ensure mechanical durability and limit the vehicle Total Cost of Ownership (TCO) by reducing the servicing intervals. The objective of this investigation was to gain an improved understanding of the underlying mechanisms that are responsible for the accumulation of particulate matter in the lubricating oil, and ultimately provide design guidelines to help limit this phenomenon.
The present study presents the development and validation of experimental and numerical tools used to investigate this phenomenon. Several advanced diagnostic techniques were developed and applied on an optically-accessible single cylinder Diesel engine to detect the presence of particulates and quantify their concentration in two particular zones: (1) in the upper part of the cylinder liner where particulate matter is believed to be absorbed into the oil film and (2) in the engine blow-by gases where particulates can be transported via the piston ring-pack to the oil sump reservoir. The accumulation of soot particulates on the surface of the upper part of the cylinder liner was characterized using a modified Laser Extinction Method (LEM), while the concentration of particulates in the engine blow-by gases was measured using a DMS500 soot sensor. In parallel to the experimental study, 3D numerical computations were performed and provided additional information to the experimental results. In the present paper, the various experimental and numerical methods are presented and first validation results are discussed.