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The Effects of Oil Aeration on the Reliability of Engine Bearings During High Speed Cornering Conditions
Published October 17, 1994 by Society of Automotive Engineers of China in China
This paper presents a new approach for determining the allowable limit of the oil aeration rate which will not be detrimental to the engine bearing reliability. This approach is based on the measurement of minimum oil film thicknesses (MOFTS) of bearings and crankshaft temperatures according to the change of oil aeration rate. Oil is likely to be aerated under high speed cornering conditions and that results in the drop of main gallery pressure. This level of oil aeration is duplicated in an engine dyno test by the use of a special air injection device and monitoring with on-line aeration measurement system. Bearing reliability is evaluated by the measured results of MOFTS in bearings and the surface temperatures of the crankshaft, and especially the linkage system was used for measuring MOFT in the connecting rod bearing. Consequently, the oil aeration rate lower then 30% (under the any main gallery oil pressure) was verified to be allowable in preserving the oil film on a bearing. Based on this guideline, the problem of the connecting rod bearing failure which occurred during high speed cornering of a vehicle, can be improved by modification of the oil pan and strainer.