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Research Papers

Machinability and Optimization of Shrouded Centrifugal Impellers for Implantable Blood Pumps

[+] Author and Article Information
Gordon Paul, Amin Rezaienia, Eldad Avital

School of Engineering and Materials Science,
Queen Mary University of London,
London E1 4NS, UK

Theodosios Korakianitis

Professor
Parks College of Engineering,
Aviation and Technology,
Saint Louis University,
St. Louis, MO 63103
e-mail: korakianitis@alum.mit.edu

1Corresponding author.

Manuscript received June 29, 2016; final manuscript received March 14, 2017; published online May 3, 2017. Assoc. Editor: Marc Horner.

J. Med. Devices 11(2), 021005 (May 03, 2017) (7 pages) Paper No: MED-16-1250; doi: 10.1115/1.4036287 History: Received June 29, 2016; Revised March 14, 2017

This paper describes the use of analytical methods to determine machinable centrifugal impeller geometries and the use of computational fluid dynamics (CFD) for predicting the impeller performance. An analytical scheme is described to determine the machinable geometries for a shrouded centrifugal impeller with blades composed of equiangular spirals. The scheme is used to determine the maximum machinable blade angles for impellers with three to nine blades in a case study. Computational fluid dynamics is then used to analyze all the machinable geometries and determine the optimal blade number and angle based on measures of efficiency and rotor speed. The effect of tip width on rotor speed and efficiency is also examined. It is found that, for our case study, a six- or seven-bladed impeller with a low blade angle provides maximum efficiency and minimum rotor speed.

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Figures

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Fig. 1

Impeller geometry composed of N equiangular blades with thickness t and constant angle b, and inner and outer radii Rin and Rout

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Fig. 2

(a) Cutting from inside the hub to clean up the leading edge geometry, and (b) cutting in from the outer radius with three translational axes and one rotational

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Fig. 3

Increasing the blade angle until the cutter can no longer reach the LE suction side. (a) 50 deg and (b) 55 deg are machinable, and (c) 60 deg is not.

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Fig. 4

(a) θA–B, the angle between the LE and TE points on the blade's suction side, (b) θTE–LE, where the cutter is in contact with LE and TE, and (c) θLE–LE′, where the cutter is in contact with LE and LE′

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Fig. 5

Increasing the blade angle until the cutter can no longer reach the LE pressure side. The pressure side of (a) 60 deg and (b) 65 deg are machinable, and (c) 70 deg is not.

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Fig. 6

(a) θCD, the angle between the points where the clockwise edge of the cutter meets the rim and hub, (b) θTE–LE′, the minimum angle at which the cutter passes the TE to manufacture the suction side of LE′, and (c) θLE′–TAN, the angle required to machine the geometry at the suction side of LE′

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Fig. 7

The model used in the CFD analysis

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Fig. 8

The results for impellers with tip width optimized for maximum efficiency: left, rotor speed; right, efficiency

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Fig. 9

The effect of tip width on efficiency for a five-bladed impeller for all machinable blade angles

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Fig. 10

The effect of tip width on efficiency for a six-bladed impeller for all machinable blade angles

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Fig. 11

The results for impellers with tip width optimized for minimum rotor speed: left, rotor speed; right, efficiency

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Fig. 12

The effect of tip width on rotor speed for a five-bladed impeller and all machinable blade angles

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