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Iso-geometric shape optimization of magnetic density separators

Nguyen Dang Manh (Department of Applied Mathematics, SINTEF Information and Communication Technology, Oslo, Norway)
Anton Evgrafov (Department of Applied Mathematics and Computer Science, Technical University of Denmark, Copenhagen, Denmark)
Jens Gravesen (Department of Applied Mathematics and Computer Science, Technical University of Denmark, Copenhagen, Denmark)
Domenico Lahaye (Faculty of Electrical Engineering, Mathematics and Computer Science, TU Delft, Delft, The Netherlands)

Abstract

Purpose

The waste recycling industry increasingly relies on magnetic density separators. These devices generate an upward magnetic force in ferro-fluids allowing to separate the immersed particles according to their mass density. Recently, a new separator design has been proposed that significantly reduces the required amount of permanent magnet material. The purpose of this paper is to alleviate the undesired end-effects in this design by altering the shape of the ferromagnetic covers of the individual poles.

Design/methodology/approach

The paper represents the shape of the ferromagnetic pole covers with B-splines and defines a cost functional that measures the non-uniformity of the magnetic field in an area above the poles. The authors apply an iso-geometric shape optimization procedure, which allows us to accurately represent, analyze and optimize the geometry using only a few design variables. The design problem is regularized by imposing constraints that enforce the convexity of the pole cover shapes and is solved by a non-linear optimization procedure. The paper validates the implementation of the algorithm using a simplified variant of the design problem with a known analytical solution. The algorithm is subsequently applied to the problem posed.

Findings

The shape optimization attains its target and yields pole cover shapes that give rise to a magnetic field that is uniform over a larger domain.

Research limitations/implications

This increased magnetic field uniformity is obtained at the cost of a pole cover shape that differs per pole. This limitation has negligible impact on the manufacturing of the separator. The new pole cover shapes therefore lead to improved performance of the density separation.

Practical implications

Due to the larger uniformity the generated field, these shapes should enable larger amounts of waste to be processed than the previous design.

Originality/value

This paper treats the shapes optimization of magnetic density separators systematically and presents new shapes for the ferromagnetic poles covers.

Keywords

Acknowledgements

Nguyen Dang Manh gratefully acknowledges the financial support from the European Community's Seventh Framework Program FP7/2007-2013 under grant agreement number PITN-GA-2008-214584 (SAGA). Domenico Lahaye gratefully acknowledges Henk Polinder and Peter Rem for the many fruitful discussions during the course of this work. The authors thank the four anonymous referees for their valuable comments on the previous version of this work.

Citation

Dang Manh, N., Evgrafov, A., Gravesen, J. and Lahaye, D. (2014), "Iso-geometric shape optimization of magnetic density separators", COMPEL - The international journal for computation and mathematics in electrical and electronic engineering, Vol. 33 No. 4, pp. 1416-1433. https://doi.org/10.1108/COMPEL-07-2013-0234

Publisher

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Emerald Group Publishing Limited

Copyright © 2014, Emerald Group Publishing Limited

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