USE OF A COUETTE HIGH-SHEAR-RATE VISCOMETER FOR MEASURING THE VISCOSITY OF ENGINE LUBRICANTS
A Couette viscometer is described that can measure engine lubricant viscosity at a temperature of 150 degress C and for a range of shear rates. In this instrument, the heat generation rate can be minimized by making the annular gap very small. The main technical difficulty involves uncertainties in annular gap dimensions measured by an electrical capacitance method; gap size is averaged in the correct way to measure the viscosity of Newtonian fluids. The annular gap varies considerably, depending on rotation speed and sample injection pressure. Temperature rise due to viscous energy dissipation, estimated by viscosity measurements on Newtonian oils, correlates with the rate of energy input (rotation speed times torque). The temperature rise estimated viscometrically, however, is much larger than that predicted by considering heat generation and thermal conductivity of oil. Possible reasons for this discrepancy include rotor metal surface heating and stator and non-Newtonian flow characteristics of supposedly Newtonian fluids. A method of correcting measured viscosity for estimated temperature rise is proposed, and viscometric data for some single-grade oils and multigrade oils are presented.
- Also published in HS-028 993 (SAE-SP-460), "The Relationship between Engine Oil Viscosity and Engine Performance, Pt. 5 and Pt. 6," Warrendale, Pennsylvania, 1980 p 1-12. Presented at SAE Congress and Exposition, Detroit, 25-29 February 1980.
Warrendale, PA United States 15096
- Wright, B
- Mather, J
- Publication Date: 1980
- Features: References;
- Pagination: 12 p.
- TRT Terms: Engine oils; Measurement; Temperature; Viscometers; Viscosity
- Subject Areas: Safety and Human Factors;
- Accession Number: 00393484
- Record Type: Publication
- Source Agency: National Highway Traffic Safety Administration
- Report/Paper Numbers: SAE 790212, HS-028 994
- Files: HSL, USDOT
- Created Date: Mar 29 1985 12:00AM