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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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Oil Transport Phenomena during extreme load transients inside the power cylinder unit as investigated by HS-2DLIF (High-Speed 2D Laser-Induced Fluorescence)

Sloan Automotive Laboratory, Massachusetts Institute of Tech-Sebastian Ahling, Tian Tian
  • Technical Paper
  • 2019-01-2363
Published 2019-12-19 by SAE International in United States
This paper presents findings of optical investigations conducted via the HS-2DLIF (high-speed two-dimensional laser-induced fluorescence) technique under extreme transient conditions. These extreme conditions are a transition from WOT to closed throttle and vice versa. The goal is to gain a better understanding of oil transport magnitudes and timescales for transitions to and from extreme throttled conditions. These conditions are similar to the boundary conditions found during cylinder deactivation.The transients were conducted under motored conditions with injection and spark disabled in a speed range from 650 rpm to 3000 rpm. The load was transitioned from WOT to different low load conditions (closed, 150 mbar and 200 mbar), held at that low load for a variety of durations (10 sec - 600 sec), before going back to WOT. The experiments showed a strong dependence of oil transport on speed and load. The higher the speed, the faster the oil transport.When transitioning to WOT in cases with a lot of oil in the ring pack, a drastic blow-by increase could be measured. The cause of the phenomena could…
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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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Experimental Investigation of a RCCI Combustion Concept with In-Cylinder Blending of Gasoline and Diesel in a Light Duty Engine

FEV GmbH-Hans Rohs, Bastian Holderbaum
FEV Group Holding GmbH-Thomas Körfer
Published 2015-09-06 by SAE International in United States
Within this study a dual-fuel concept was experimentally investigated. The utilized fuels were conventional EN228 RON95E10 and EN590 Diesel B7 pump fuels. The engine was a single cylinder Diesel research engine for passenger car application. Except for the installation of the port fuel injection valve, the engine was not modified. The investigated engine load range covered low part load operation of IMEP = 4.3 bar up to IMEP = 14.8 bar at different engine speeds. Investigations with Diesel pilot injection showed that the dual-fuel approach can significantly reduce the soot/NOx-trade-off, but typically increases the HC- and CO-emissions. At high engine load and gasoline mass fraction, the premixed gasoline/air self-ignited before Diesel fuel was injected.Reactivity Controlled Compression Ignition (RCCI) was subsequently investigated in a medium load point at IMEP = 6.8 bar. Here, the impact of EGR, gasoline mass fraction and DI injection pressure and timing on emissions and combustion behavior were investigated. Despite elevated HC- and CO-emissions, it was possible to achieve a higher efficiency while simultaneously keeping the engine-out NOx-emissions below the EU-6.1 level.…
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