This content is not included in your SAE MOBILUS subscription, or you are not logged in.
A Comparison of the Total Capacitance and Total Resistance Techniques for Measuring the Thickness of Journal Bearing Oil Films in an Operating Engine
ISSN: 0148-7191, e-ISSN: 2688-3627
Published February 01, 1988 by SAE International in United States
Annotation ability available
Bearing oil film thickness (BOFT) values were determined for the front sain bearing of a four-cylinder engine at different engine speeds, loads, and oil temperatures using two different measurement techniques. The total resistance technique assumes the oil film can be modelled as a simple ohmic resistor. The total capacitance technique assumes the oil film can be described as a simple capacitor. A comparison of results determined using both methods for a set of single-grade oils demonstrates that, although the methods agree quantitatively for certain combinations of engine test conditions and oils, the level of precision with the total capacitance technique is greater than with the total resistance technique. This difference is attributed to the fact that the oil dielectric constant, which is needed for calculating BOFT values in the total capacitance method, can be measured more precisely than can the oil conductivity, which is needed in the total resistance method. Of the two methods, the total capacitance technique is superior for measuring bearing oil film thickness in an operating engine.
CitationSpearot, J. and Murphy, C., "A Comparison of the Total Capacitance and Total Resistance Techniques for Measuring the Thickness of Journal Bearing Oil Films in an Operating Engine," SAE Technical Paper 880680, 1988, https://doi.org/10.4271/880680.
- Stone J.M. Underwood, A.F. “Load Carrying Capacity of Journal Bearings,” SAE Quarterly Transactions 1 1 1947 56
- Sims, W.D. “Measuring the Oil Film Thickness in a Crankshaft Main Bearing of a V-8 Engine,” Lubrication Engineering 17 1961 123
- Goodwin, G. Holmes, R. “On the Continuous Monitoring of Oil Film Thickness in an Engine Bearing,” Proc. Inst. Mech. Engrs. 192 1978 371
- Ishihama, M. Hayashi, Y. Kubozuka, T. “An Analysis of the Movement of the Crankshaft Journals During Engine Firing,” SAE Paper No. 810771
- Craig, R.C. King, W.H. Appeldoorn, J.K. “Oil Film Thickness in Engine Bearings - The Bearing as a Capacitor,” SAE Paper No. 821250
- Girshick, F. Craig, R.C. “Oil Film Thickness in a Bearing of a Fired Engine - Part III: The Effects of Lubricant Rheology,” SAE Paper No. 831691
- Schilowitz, A.M. Waters, J.L. “Oil Film Thickness in a Bearing of a Fired Engine -Part IV: Measurements in a Vehicle on the Road,” SAE Paper No. 861561
- Spearot, J.A. Murphy, C.K. Rosenberg, R.C. “Measuring the Effect of Oil Viscosity on Oil Film Thickness in Engine Journal Bearings,” SAE Paper No. 831689
- Bassoli, C. Cornetti, G. Bilei, M. “A System for Assessing the General Conditions of Lubricated Crankshafts,” RIVISTA ATAT January 1978
- Bates, T.W. Williamson, B. Spearot, J.A. Murphy, C.K. “A Correlation Between Engine Oil Rheology and Oil Film Thickness in Engine Journal Bearings,” SAE Paper No. 860376
- ASTM Data Series Publication 62 “The Relationship Between High-Temperature Oil Rheology and Engine Operation,” December 1984
- King, W.H. “Method for Determining Minimum Lubricating Oil Film Thickness Under Operating Engine Conditions Using Electrical Capacitance” U.S. Patent 4,443,754 April 1984
- Cryvoff, S.A. 1987
- du Parquet J. Godet, A. “Assessment of Lubrication Conditions in a Big-End Bearing by Temperature Measurements - Correlation with High-Shear Viscosity,” SAE Paper No. 780980