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Meng, Zhen
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A Computational Study of the Lubricant Transport into Oil Control Ring Groove

Sloan Automotive Laboratory, Massachusetts Institute of Tech-Tianshi Fang, Zhen Meng, Sebastian Ahling, Tian Tian
  • Technical Paper
  • 2019-01-2362
Published 2019-12-19 by SAE International in United States
Lubricant transport into an oil control ring (OCR) groove through the clearance between the lower flank of the OCR and the groove was studied. A primary driving force of such lubricant transport is a dynamic pressure on the outer end of the clearance. The magnitude of the pressure depends on the flow pattern in the skirt chamfer region. Computational Fluid Dynamics (CFD) was employed to simulate the multiphase flow involving lubricant and gas in a skirt chamfer region. A correlation to predict the dynamic pressure was proposed and validated. The amount of lubricant transport into an OCR groove was found remarkable in a high-speed full-load condition.
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Study of the Effects of Oil Supply and Piston Skirt Profile on Lubrication Performance in Power Cylinder Systems

Massachusetts Institute of Technology-Zhen Meng, Sebastian Ahling, Tian Tian
  • Technical Paper
  • 2019-01-2364
Published 2019-12-19 by SAE International in United States
In internal combustion engines, the majority of the friction loss associated with the piston takes place on the thrust side in early expansion stroke. Research has shown that the Friction Mean Effective Pressure (FMEP) of the engine can be reduced if proper modifications to the piston skirt, which is traditionally barrel-shaped, are made. In this research, an existing model was applied for the first time to study the effects of different oil supply strategies for the piston assembly. The model is capable of tracking lubricating oil with the consideration of oil film separation from full film to partial film. It is then used to analyze how the optimized piston skirt profile investigated in a previous study reduces friction. It was found that the profile is able to maintain a larger amount of lubricant between the lower part of the piston skirt and the cylinder liner during compression stroke, thereby generating more hydrodynamic pressure, instead of asperity contact pressure, to balance the lateral force from piston pin.
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Modeling of Oil Transport between Piston Skirt and Cylinder Liner in Internal Combustion Engines

SAE International Journal of Advances and Current Practices in Mobility

Massachusetts Institute of Technology-Zhen Meng, Sebastian Ahling, Tian Tian
  • Journal Article
  • 2019-01-0590
Published 2019-04-02 by SAE International in United States
The distribution of lubricating oil plays a critical role in determining the friction between piston skirt and cylinder liner, which is one of the major contributors to the total friction loss in internal combustion engines. In this work, based upon the experimental observation an existing model for the piston secondary motion and skirt lubrication was improved with a physics-based model describing the oil film separation from full film to partial film. Then the model was applied to a modern turbo-charged SI engine. The piston-skirt FMEP predicted by the model decreased with larger installation clearance, which was also observed from the measurements using IMEP method at the rated. It was found that the main period of the cycle exhibiting friction reduction is in the expansion stroke when the skirt only contacts the thrust side for all tested installation clearances. The main reason for lower skirt friction with larger clearance is greater amount of oil available during the expansion stroke.
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