Lorentz force particle analyzer

Abstract

International audienceA new contactless technique is presented for the detection of micron-sized insulating particles in the flow of an electrically conducting fluid. A transverse magnetic field brakes this flow and tends to become entrained in the flow direction by a Lorentz force, whose reaction force on the magnetic-field-generating system can be measured. The presence of insulating particles suspended in the fluid produce changes in this Lorentz force, generating pulses in it; these pulses enable the particles to be counted and sized. A two-dimensional numerical model that employs a moving mesh method demonstrates the measurement principle when such a particle is present. Two prototypes and a three-dimensional numerical model are used to demonstrate the feasibility of a Lorentz force particle analyzer (LFPA). The findings of this study conclude that such an LFPA, which offers contactless and on-line quantitative measurements, can be applied to an extensive range of applications. These applications include measurements of the cleanliness of high-temperature and aggressive molten metal, such as aluminum and steel alloys, and the clean manufacturing of semiconductors. Published by AIP Publishing

A theoretical model of Lorentz force particle analyzer: a potential flow perspective

“…By measuring the variation of the interaction with the magnet, the LFPA can count and size the inclusion. The feasibility of this method at various scales was verified in our previous work [16,17], where several prototype experiments and a numerical model were presented. The results demonstrate that an LFPA can, in principle, detect micron-sized particles in a solid or liquid metal.…”

“…However, an insulating particle within the liquid conductor results in a change in the reaction force. Thus, micron-sized particles can be measured and counted [16]. Given the substantial demand for the ability to analyze micron-sized inclusions in liquid metals, the particle considered in the present paper is sufficiently small relative to the thickness of the layer…”

“…All these transients vary remarkably across the region in which the physical quantities such as the magnetic field and eddy current accumulate. This region is termed the electromagnetic sensing zone (EMSZ) [16]. Clearly, from the viewpoint of surveying, we expect this force and torque to be as large possible to be detectable and measurable.…”

“…Recently, a method involving the placement of a small permanent magnet near the flow has been proposed and is termed Lorentz force particle analyzer (LFPA) [16,17], which is inspired by another exiting technique named Lorentz force velocimetry (LFV) [18,19]. The LFPA is a contactless method for particle inspection via magnetic induction.…”

“…The goal of the present work is to explain the physics underlying this method by formulating a theoretical model. Our previous papers introduced only the basic principles and experimental and numerical prototypes [16,17] and a two-dimensional elemental theoretical model. Several essential questions remain unanswered: (1) The secondary magnetic field can also actually be a measuring quantity, how does its distribution varies with the presence of the particle?…”