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Research Papers: Design of Energy, Fluid, and Power Handing Systems

Theoretical Analysis and Design of a Variable Delivery External Gear Pump for Low and Medium Pressure Applications

[+] Author and Article Information
Srinath Tankasala

Maha Fluid Power Research Center,
Purdue University,
1500 Kepner Dr,
Lafayette, IN 47905
e-mail: srinath.tank@gmail.com

Andrea Vacca

Maha Fluid Power Research Center,
Purdue University,
1500 Kepner Dr,
Lafayette, IN 47905
e-mail: avacca@purdue.edu

Contributed by the Design Engineering Division of ASME for publication in the JOURNAL OF MECHANICAL DESIGN. Manuscript received June 7, 2018; final manuscript received August 29, 2018; published online October 10, 2018. Assoc. Editor: Yu-Tai Lee.

J. Mech. Des 141(1), 013401 (Oct 10, 2018) (11 pages) Paper No: MD-18-1433; doi: 10.1115/1.4041351 History: Received June 07, 2018; Revised August 29, 2018

This paper describes a unique design concept that is capable of electronically controlling the flow delivered by an external gear pump (EGP). The principle used for varying the flow relies on the variable timing concept which has been previously demonstrated by the author's research team for EGP's operating at high pressures (HPs) (p > 100 bar). This principle permits to vary the flow within a certain range, without introducing additional sources of power loss. In this paper, the above concept has been applied to formulate a design for a variable delivery EGP for low pressure (LP) applications (p < 30 bar), suitable for direct electric actuation. Specific design principles for the gear and the flow variation mechanisms are introduced to limit the force required by the electric actuation, and for maximizing the flow variation range. Also, the low target pressure allows the variable timing principle to be realized with an asymmetric solution, with only one variable timing element present at one side of the gears. A detailed analysis concerning the relationship between the electrically commanded position of the flow varying element and the theoretical flow delivered by the pump is also presented. This analysis is used to formulate analytical expressions for the instantaneous flow rate and the flow nonuniformity of the pump. The paper details the design principle of the proposed variable flow pump and describes the multi-objective optimization approach used for sizing the gears and flow variation mechanism. The paper also discusses the experimental activity performed on a prototype of the proposed unit, able to achieve a flow variation of 31%.

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References

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Vacca, A. , and Devendran, R. S. , 2016, “ Variable Delivery External Gear Machine,” Purdue Research Foundation, West Lafayette, IN, U.S. Patent No. 15/121,586. https://patents.google.com/patent/US20160369795A1/en?oq=15%2f121%2c586
Devendran, R. S. , and Vacca, A. , 2017, “ Theoretical Analysis for Variable Delivery Flow External Gear Machines Based on Asymmetric Gears,” Mech. Mach. Theory, 108(Suppl. C), pp. 123–141. [CrossRef]
Tankasala, S. , and Vacca, A. , 2017, “ A Solution for an Electronically-Controlled Variable Delivery External Gear Pump,” ASME Paper No. FPMC2017-4328.
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Figures

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Fig. 5

Slider separating the fluid regions

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Fig. 4

Design principle of slider: (1) O-ring seal for maintaining pressures

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Fig. 3

Design exploded view: (1) flange; (2) Backcover +casing; (3) lateral plate; (4) gears; (5) Front cover; (6) front cover top; (7) slider; and (8) stepper motor

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Fig. 6

Design parameters of the slider

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Fig. 7

Section view of slider foot region

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Fig. 2

Operation of VD-EGP with respect to one TSV

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Fig. 1

VD-EGP concept of changing lateral groove position

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Fig. 8

VD-EGP prototype with linear stepper motor

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Fig. 9

Convention for measurement of u

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Fig. 10

Illustration of showing when the TSV is not considered as pumping, i.e., when it is exposed to suction

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Fig. 12

Illustration of the multilevel multi objective optimization approach

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Fig. 13

Profile of optimized gears from Ref. [16]

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Fig. 11

Gear parameters based on the rack cutter

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Fig. 15

Instantaneous flow rate at ω = 1500 rpm at different slider positions

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Fig. 16

Instantaneous flow rate at minimum and maximum displacements, ω = 1500 rpm

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Fig. 22

Flow rate versus slider position of the VD-EGP at 2000 rpm at various delivery pressures

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Fig. 17

Mean kinematic flow rate at different slider positions y, ω = 1500 rpm

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Fig. 14

Pareto plot between OF2 and OF3

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Fig. 18

Testing setup for the prototype VD-EGP

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Fig. 19

ISO schematic of test setup

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Fig. 20

Flow rate versus delivery pressure at maximum flow setting of the VD-EGP

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Fig. 21

Flow rate versus delivery pressure at minimum flow setting of the VD-EGP

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