Research Papers

On Fluid Compressibility in Switch-Mode Hydraulic Circuits—Part II: Experimental Results

[+] Author and Article Information
James D. Van de Ven

Department of Mechanical Engineering,
Worcester Polytechnic Institute,
100 Institute Road,
Worcester, MA 01609

1Present address: University of Minnesota, 111 Church Street SE, Minneapolis, MN 55455, e-mail: vandeven@umn.edu.

Contributed by the Dynamic Systems Division of ASME for publication in the JOURNAL OF DYNAMIC SYSTEMS, MEASUREMENT, AND CONTROL. Manuscript received June 7, 2011; final manuscript received October 9, 2012; published online December 20, 2012. Assoc. Editor: Robert Landers.

J. Dyn. Sys., Meas., Control 135(2), 021014 (Dec 20, 2012) (7 pages) Paper No: DS-11-1178; doi: 10.1115/1.4023063 History: Received June 07, 2011; Revised October 09, 2012

In this paper, the author presents experimental work with a generic switch-mode hydraulic circuit that aims to validate a previously presented computational model, with primary focus on the energy loss due to fluid compressibility. While multiple previous papers have presented experimental works with switch-mode hydraulic circuits, the presented experimental system is unique due the capability of in-flow measurement of the entrained air in the hydraulic fluid. A designed experiment was run that varied the entrained air, system pressure, and volume of the fluid experiencing pressure fluctuations, defined as the switched volume. The calculated volumetric efficiency from these experiments ranged from to 61% to 75%, with efficiency increasing with decreased levels of entrained air, system pressure, and switched volume. These efficiency trends and the pressure profile in the switched volume agree well with the computational model presented in Part I of this two part set (Van de Ven, 2013, “On Fluid Compressibility in Switch-Mode Hydraulic Circuits—Part I: Modeling and Analysis,” ASME J. Dyn. Sys., Meas., Control, 135(2), p. 021013). Differences between the experimental results and the computational model include approximately 10% higher predicted efficiency and pressure oscillations found in the experimental work that were not predicted by the model.

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Fig. 4

Valve command and pressure in the switched volume with a switching frequency of 10 Hz and a duty cycle of 60%. Note the detected rising and falling edges used to find the period and duty cycle. The horizontal line at 142 kPa corresponds to the pressure where the check valve opens. These data are for a 20 cm3 switched volume, 6.9 MPa accumulator pressure, and air volume fraction of 2.5%.

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Fig. 5

Output power as a function of entrained air, switched volume, and accumulator pressure

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Fig. 6

Nondimensional high-pressure and compressed air power into the switched volume as a function of entrained air, switched volume, and pressure. The input powers are nondimensionalized by dividing them by the output power.

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Fig. 7

Input power from the low-pressure branch through the 3-way valve and the check valve

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Fig. 3

Photograph of the experimental system. Note, the switched volume between the 3-way valve and the motor is currently at the smallest volume, 20 cm3.

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Fig. 2

Schematic of the major components of the experimental system. The bold fluid volume between the 3-way valve and the motor is the switched volume.

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Fig. 1

Photograph of the low-pressure sight glass at 3.1% entrained air by volume. Note the small diameter air bubbles entrained in the fluid.

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Fig. 8

Volumetric efficiency as a function of the entrained air, switched volume, and accumulator pressure

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Fig. 9

Pressure in the switched volume with a switching frequency of 10 Hz, a duty cycle of 60%, a switched volume of 42 cm3, an accumulator pressure of 6.9 MPa, and an air volume fraction of 5.3%




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