| Summary: | The Lubrication Oil Consumption (LOC) has been a critical issue for vehicle and engine manufactures for a long time. It can generate harmful Oil Emission (OE) as well as deteriorate the aftertreatment system. During transient engine operations, an increase of OE can be introduced but some of the mechanisms remained unclear. Thus, a throughout understanding of oil transport in the ring pack is needed to improve engine design.
In this work, an optical engine with 2D Laser Induced Fluorescence (2D-LIF) technique was applied to the oil transport in a ring pack equipped with Three-Piece Oil Control Ring (TPOCR). It was found that an engine load results in zero blowby is the separation line to divide two drastically different oil flow patterns. Running the engine with a load lower than this line can result in an increase of oil accumulation inside TPOCR groove, followed by oil upwards transport into the third land, the second land and finally oil droplets through top ring gap. The time needed for oil leakage to pass different rings was investigated with the combination of numerical models, which can analyze the ring dynamics, gas flow and oil gas interaction. Given long enough time running under the blowby separation line, a sudden increase of engine load can result in increase of oil leakage to the combustion chamber, coming from the oil accumulated in the second land and top ring groove. Furthermore, the effect of drain holes and the relative location between ring gaps was studied to examine oil local distribution and overall LOC. One obvious practical takeaway is either to always run the engine with a positive blowby or to limit the duration of time with zero blowby. These findings can help improve the engine design and calibration to minimize the LOC as well as OE in Spark Ignition (SI), hydrogen and gas engines equipped with TPOCR.
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