Research Papers: Flows in Complex Systems

Three-Dimensional Numerical Simulation of an External Gear Pump With Decompression Slot and Meshing Contact Point

[+] Author and Article Information
R. Castilla

Department of Fluid Mechanics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: castilla@mf.upc.edu

P. J. Gamez-Montero

Department of Fluid Mechanics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: pjgm@mf.upc.edu

D. del Campo

Department of Aeronautics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: david.del.campo@upc.edu

G. Raush

Department of Fluid Mechanics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: gustavo.raush@upc.edu

M. Garcia-Vilchez

Department of Fluid Mechanics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: mercedes.garcia-vilchez@upc.edu

E. Codina

Department of Fluid Mechanics,
Universitat Politècnica de Catalunya,
Terrassa, Barcelona 08222, Spain
e-mail: ecodina@mf.upc.edu

1Corresponding author.

Contributed by the Fluids Engineering Division of ASME for publication in the JOURNAL OF FLUIDS ENGINEERING. Manuscript received April 10, 2014; final manuscript received November 12, 2014; published online January 13, 2015. Assoc. Editor: Bart van Esch.

J. Fluids Eng 137(4), 041105 (Apr 01, 2015) (10 pages) Paper No: FE-14-1184; doi: 10.1115/1.4029223 History: Received April 10, 2014; Revised November 12, 2014; Online January 13, 2015

Recently several works have been published on numerical simulation of an external gear pump (EGP). Such kinds of pumps are simple and relatively inexpensive, and are frequently used in fluid power applications, such as fluid power in aeronautical, mechanical, and civil engineering. Nevertheless, considerable effort is being undertaken to improve efficiency and reduce noise and vibration produced by the flow and pressure pulsations. Numerical simulation of an EGP is not straightforward principally for two main reasons. First, the gearing mechanism between gears makes it difficult to handle a dynamic mesh without a considerable deterioration of mesh quality. Second, the dynamic metal–metal contact simulation is important when high pressure outflow has to be reproduced. The numerical studies published so far are based on a two-dimensional (2D) approximation. The aim of the present work is to contribute to the understanding of the fluid flow inside an EGP by means of a complete three-dimensional (3D) parallel simulation on a cluster. The 3D flow is simulated in a linux cluster with a solver developed with the openfoam Toolbox. The hexahedral mesh quality is maintained by periodically replacing the mesh and interpolating the physical magnitudes fields. The meshing contact point is simulated with the viscous wall approach, using a viscosity model based on wall proximity. The results for the flow rate ripples show a similar behavior to that obtained with 2D simulations. However, the flow presents important differences inside the suction and the discharge chambers, principally in the regions of the pipes' connection. Moreover, the decompression slot below the gearing zone, which can not be simulated with a 2D approximation, enables a more realistic simulation of a contact ratio greater than 1. The results are compared with experimental measurements recently published.

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Fig. 1

Working principle of an EGP. Fluid is carried from the inlet port to the outlet port in the interteeth spaces between gears and case.

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Fig. 2

Scheme of the meshing region between gears, showing the LA, and the pressure angle

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Fig. 3

Picture of the lateral plate with the decompression slot machined en the outlet port

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Fig. 4

Scheme showing the gear contact region and the flow rate in a case where contact ratio is greater than unity

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Fig. 5

Computational domain with gears, suction pipe and chamber, impulsion pipe and chamber, and decompression slot

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Fig. 6

Mesh for the 2D simulation and detail of the gearing zone

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Fig. 7

3D gear pump mesh. Symmetry plane view.

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Fig. 8

Detail of decompression slot mesh connecting teeth space and impulsion chamber

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Fig. 9

Flowchart of mesh replacement and interpolation

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Fig. 10

The speed-up of the simulation scalability

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Fig. 11

The logistic function for k = 5 and k = 40, with kd = 3, compared with the normal distribution

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Fig. 12

Backlash clearance without contact

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Fig. 13

Flow rate time series in inlet for ɛ=1.0 and ɛ=1.4

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Fig. 14

Flow rate time series in outlet for ɛ=1.0 and ɛ=1.4

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Fig. 15

Velocity vx time series for one gearing cycle in the point Pinlet

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Fig. 16

Pressure time series for one gearing cycle in the point Pinlet

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Fig. 17

Pressure time series for one gearing cycle in the point Poutlet

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Fig. 18

Streamlines for 2D simulation for ɛ=1.4

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Fig. 19

Streamlines for 3D simulation in the symmetry plane, and comparison with experimental results, from Ref. [34]

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Fig. 20

3D view of the streamlines for the numerical simulation



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