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TECHNICAL PAPERS: Internal Combustion Engines

Analysis of Oil Film Thickness and Heat Transfer on a Piston Ring of a Diesel Engine: Effect of Lubricant Viscosity

[+] Author and Article Information
Yasuo Harigaya, Michiyoshi Suzuki, Fujio Toda

Department of Technology Education,  Utsunomiya University, Utsunomiya, Japan

Masaaki Takiguchi

Department of Mechanical Engineering,  Musashi Institute of Technology, Tokyo, Japan

J. Eng. Gas Turbines Power 128(3), 685-693 (Sep 24, 2004) (9 pages) doi:10.1115/1.1924403 History: Received January 20, 2003; Revised September 24, 2004

The effect of lubricant viscosity on the temperature and thickness of oil film on a piston ring in a diesel engine was analyzed by using unsteady state thermohydrodynamic lubrication analysis, i.e., Reynolds equation and an unsteady state two-dimensional energy equation with heat generated from viscous dissipation. The oil film viscosity was then estimated by using the mean oil film temperature and the shear rate for multigrade oils. Since the viscosity for multigrade oils is affected by both the oil film temperature and shear rate, the viscosity becomes lower as the shear rate between the ring and liner becomes higher. Under low load conditions, the viscosity decreases due to temperature rise and shear rate, while under higher load conditions, the decrease in viscosity, is attributed only to the shear rate. The oil film thickness between the ring and liner decreases with a decrease of the oil viscosity. The oil film thickness calculated by using the viscosity estimated by both the shear rate and the oil film temperature gave the smallest values. For multigrade oils, the viscosity estimation method using both the mean oil film temperature and shear rate is the most suitable one to predict the oil film thickness. Moreover, the heat transfer at ring and liner surfaces was examined.

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Copyright © 2006 by American Society of Mechanical Engineers
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Figures

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Figure 1

Lubrication model between ring and liner

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Figure 2

Configuration of top ring sliding surface (experimental values)

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Figure 3

Cylinder liner surface temperatures (oil: SAE 30, experimental values)

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Figure 4

Relation between viscosity and temperature (low shear rate)

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Figure 5

Relation between viscosity and shear rate for multi grade oil (SAE 10W50a)

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Figure 6

Temperature distributions in oil film between ring and liner (oil: SAE 10W50a, 1600 rpm, full load). (a) CA=30deg. (b) CA=270deg.

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Figure 7

Temperature distributions (μ=f(Tm,γ), TL=TR=30°C, Oil: SAE 10W50a, 800 rpm, no load) (a) CA=30deg. (b) CA=270deg.

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Figure 8

Oil film temperature, shear rate, viscosity, and thickness under low temperature condition (TL=TR=30°C, oil: SAE 10W50a, 800 rpm, no load). (a) Oil film temperature. (b) Shear rate. (c) Viscosity. (d) Oil film thickness.

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Figure 9

Oil film temperature, shear rate, viscosity, and thickness (TL, TR; measured values, oil: SAE 10W50a, 1600 rpm, no load). (a) Oil film temperature. (b) Shear rate. (c) Viscosity. (d) Oil film thickness.

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Figure 10

Oil film thickness (TL, TR; measured values, oil: SAE 10W50a, 1600 rpm, full load)

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Figure 11

Oil film thickness (TL, TR; measured values, oil: SAE 10W50a, 2800 rpm, full load)

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Figure 12

Oil film temperature, shear rate, viscosity, and thickness (Comparison of various lubricants TL, TR; measured values, 2800 rpm, full load). (a) Oil film temperature. (b) Shear rate. (c) Viscosity. (d) Oil film thickness.

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Figure 13

Oil film viscosity and thickness (comparison of multigrade lubricants TL, TR; measured values, 2800 rpm, full load). (a) Viscosity. (b) Oil film thickness.

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Figure 14

Heat transfer, heat convection, and viscous heating in oil film 2800 rpm, full load, oil: 10W50a). (a) Heat transfer at ring and liner surfaces. (b) Heat convection and viscous heating.

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