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Research Papers

Fluid and Dynamics Analyses of a Gerotor Pump Using Various Span Angle Designs

[+] Author and Article Information
Chiu-Fan Hsieh

Department of Mechanical and
Computer-Aided Engineering,
National Formosa University,
64 Wunhua Road,
Huwei, Yunlin, Taiwan, 63201, ROC
e-mail: cfhsieh@nfu.edu.tw

1Corresponding author.

Contributed by the Power Transmission and Gearing Committee of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received November 14, 2011; final manuscript received August 23, 2012; published online October 19, 2012. Assoc. Editor: Prof. Philippe Velex.

J. Mech. Des 134(12), 121003 (Oct 19, 2012) (13 pages) doi:10.1115/1.4007703 History: Received November 14, 2011; Revised August 23, 2012

This paper examines how the span angle design of its tooth profile affects the motion and pumping performance of a gerotor pump whose outer rotor profile is formed by an epicycloid and hypocycloid and whose inner rotor profile is obtainable by the theory of gearing. When the outer rotors have the same volume, the sealing performance of the rotor profile can be assessed using the curvature difference method, which indicates that sealing remains the same across various span angle designs. The tooth profile is built using mathematical models of the rotor, and fluid and dynamics analyses are conducted to predict actual pump operation. The overall fluid analysis, which models both compressibility and cavitation, clearly illustrates the complexity of the fluid flow inside the pump. Comparisons of the results for three separate span angle designs then reveal that the larger the span angle, the higher the area efficiency, outlet pressure, outlet flow rate, outlet flow velocity, and gas volume. A subsequent dynamics analysis further suggests that different span angle designs may lead to diverse contact force distribution on the inner and outer rotors. Hence, the research results provide useful guidelines for rotor design.

Copyright © 2012 by ASME
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References

Figures

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Fig. 1

Design of the outer rotor profile

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Fig. 2

Coordinate systems of the gerotor pump

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Fig. 3

Definition of span angle (a) case 1: span 20, (b) case 2: span 30, and (c) case3: span 40

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Fig. 4

Rotors profiles of three cases

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Fig. 5

Sealing evaluation by the curvature difference analysis

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Fig. 6

Simulation positions for the flow analysis

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Fig. 7

Calculation of dynamic grid and pressure during operations (a), (b), (c), and (d)

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Fig. 8

Y-direction velocity of the seven positions inside the pump (a) P01-P04 and (b) P05–P07

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Fig. 9

Pressure of the seven positions inside the pump (a) P01 and P07, (b) P02 and P06, and (c) P03–P05

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Fig. 10

Y-direction velocity variation of the outlet

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Fig. 11

Pressure variation of the outlet

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Fig. 12

Flow rate variation of the outlet

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Fig. 13

Gas volume in the gerotor pump

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Fig. 14

Given the angular velocity curve of the inner rotor

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Fig. 15

Motion analysis of the outer rotor (a) angular velocity of the outer rotor and (b) angular acceleration of the outer rotor

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Fig. 16

Model of stress analysis in inner and outer rotors (a) inner rotor stress and (b) Outer rotor stress

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Fig. 17

Stress variation of the inner rotor

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Fig. 18

Stress variation of the outer rotor

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Fig. 19

Stress of the inner and outer rotors in span 20 and span 30

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