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Research Papers: Flows in Complex Systems

Computational Fluid Dynamics Investigation of Turbulent Flow Inside a Rotary Double External Gear Pump

[+] Author and Article Information
Jafar Ghazanfarian

Mechanical Engineering Department,
Faculty of Engineering,
University of Zanjan,
Zanjan, Iran
e-mail: j.ghazanfarian@znu.ac.ir

D. Ghanbari

Mechanical Engineering Department,
University of Zanjan,
Zanjan, Iran

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received February 14, 2014; final manuscript received August 4, 2014; published online September 10, 2014. Assoc. Editor: Frank C. Visser.

J. Fluids Eng 137(2), 021101 (Sep 10, 2014) (8 pages) Paper No: FE-14-1077; doi: 10.1115/1.4028186 History: Received February 14, 2014; Revised August 04, 2014

This article presents a numerical investigation of 2D turbulent flow within a double external gear pump. The configuration of the inlet and outlet ports is determined such that the double gear pump acts like the combination of two parallel pumps. The complex geometry of the double gear pump, existence of narrow gaps between rotating and stationary walls, and rapidly deforming flow domain make the numerical solution more complicated. In order to solve the mass, momentum, and energy conservation laws along with the k-ε turbulence model, a second-order finite volume method has been used over a dynamically varying unstructured mesh. The numerical results including pressure contours, velocity vectors, flow patterns inside the suction chamber, leakage paths, and time variation of volumetric flow rate are presented in detail. The flow rate characteristic curves with linear behavior are demonstrated at rotational speeds and outlet pressures in the range of 1500–4000 rpm and 2–80 bar, respectively. The effect of reducing the gear-casing gap-size on the augmentation of the net flow rate has been investigated. It is concluded that the minimum oil pressure within the gear pump occurs at the two places between contacting gears near the inlet ports. The contours of vapor volume fraction are also illustrated.

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Figures

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Fig. 1

Schematic geometry of the double gear pump

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Fig. 2

A sample snapshot of the deformed numerical grid used to simulate the flow within the gear pump during the rotation of gears. First row: the entire numerical domain; second row: grid close-ups (a) between the left driven and driving gears, (b) near the lower right outlet port, and (c) around the right driven gear.

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Fig. 3

Comparison of volumetric flow rate (l/min) for various outlet pressures obtained from present study and experimental data [32]: (a) default gap-size and (b) reduced gap-size

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Fig. 4

Pressure contours (Pa) within the pump and the qualitative directions of applied forces on the driven gears at Po = 40 bar and N = 2000 rpm

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Fig. 5

Four snapshots of streamlines, velocity vectors, and contours of velocity magnitude during a complete cycle between the entrance and exit of two adjacent gears through: (a)–(d) the upper-left discharge chamber, (e)–(h) the lower-left suction chamber, respectively, at Po = 40 bar and N = 2500 rpm. The track of two specified moving teeth on the driving and driven gears during the cycle are marked by two solid rectangles.

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Fig. 6

Snapshots of the pressure contours (bar) and the occurrence of the minimum and maximum pressures inside the pump: (a) offline operation, Po = 2 bar, (b) Po = 80 bar, and N = 2000 rpm

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Fig. 7

Time variation of total inlet and outlet volumetric flow rates (l/min) at Po = 80 bar and N = 2000 rpm

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Fig. 8

Characteristic curves of the gear pump, variation of the volumetric flow rate (l/min) as a function of pressure outlet for various rotational speeds

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Fig. 9

Contours of the velocity magnitude (m/s) and internal leakage of the gear pump between the left driving and driven gears at Po = 40 bar and N = 1500 rpm

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Fig. 10

Modified values of volumetric flow rate (l/min) after reducing the gap-size by 9 μm at Po = 40 bar and N = 2500 rpm

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Fig. 11

Contours of vapor volume fraction at an instant of time at Po = 40 bar and N = 4000 rpm

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