Technical Brief

An Adsorption Model for Hydraulic Motor Lubrication

[+] Author and Article Information
Paul W. Michael

Fluid Power Institute,
Milwaukee School of Engineering,
1025 N. Broadway,
Milwaukee, WI 53202
e-mail: michael@msoe.edu

Shreya Mettakadapa

Fluid Power Institute,
Milwaukee School of Engineering,
1025 N. Broadway,
Milwaukee, WI 53202
e-mail: mettakadapas@msoe.edu

Shima Shahahmadi

Fluid Power Institute,
Milwaukee School of Engineering,
1025 N. Broadway,
Milwaukee, WI 53202
e-mail: shahahmadis@msoe.edu

1Corresponding author.

Contributed by the Tribology Division of ASME for publication in the JOURNAL OF TRIBOLOGY. Manuscript received March 29, 2015; final manuscript received July 21, 2015; published online September 3, 2015. Assoc. Editor: Jordan Liu.

J. Tribol 138(1), 014503 (Sep 03, 2015) (6 pages) Paper No: TRIB-15-1094; doi: 10.1115/1.4031139 History: Received March 29, 2015; Revised July 21, 2015

This paper describes an investigation of the effects of fluid properties on hydraulic motor efficiency through experimentation and modeling. Synthetic ester, straight-grade mineral oil, and VI improved hydraulic fluids were evaluated. Fluid properties, including viscosity, shear-stability, density, and traction coefficients, were characterized. A model for relating motor mechanical efficiency to fluid properties was developed. This model combines the viscosity parameter of Stribeck with the surface adsorption model of Michaelis–Menten. The results revealed that fluids with a low traction coefficient improved the low-speed efficiency of motors by transitioning out of the boundary lubrication region at a lower Stribeck number.

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Grahic Jump Location
Fig. 1

Michaelis–Menten curve depicting the relationship between the reaction constant Km and the rate of reaction. Km is equivalent to the substrate concentration [S] at 50% of the maximum reaction rate Prx.

Grahic Jump Location
Fig. 2

Flow from the pump is transmitted through the directional control valve to a bank of sensors at the motor inlet. The torque produced by the hydraulic motor is measured to determine efficiency.

Grahic Jump Location
Fig. 3

95% confidence interval of the mean torque losses for the axial piston motor and fluid A. The torque losses decreased as the speed increased.

Grahic Jump Location
Fig. 4

Traction curves for fluids under conditions of 50 N, 20–2000 mm/s, 20% slide-to-roll ratio, and 125 °C in the PCS minitraction machine

Grahic Jump Location
Fig. 5

Comparison of mechanical efficiency modeling and experimental results for the axial piston motor

Grahic Jump Location
Fig. 6

Comparison of mechanical efficiency modeling and experimental results for the orbital motor

Grahic Jump Location
Fig. 7

Comparison of mechanical efficiency modeling and experimental results for the radial piston motor



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