Mechanical Properties of a Ferrofluid Seal: Three-Dimensional Analytical Study Based on the Coulombian Model

Lemarquand, Romain Ravaud and Guy

doi:10.2528/pierb09020601

Cited by 5 publications

(5 citation statements)

References 32 publications

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“…We present first the 3D analytical expression of the magnetic scalar potential created by a paralellepipedic magnet of various polarization direction: Such an expression is useful for the study of ferrofluids used with permanent magnets [29,30]. Indeed, the magnetic pressure of the ferrofluid seal requires the accurate knowledge of the magnetic potential in all points in space.…”

Section: Introductionmentioning

confidence: 99%

Magnetic Field Produced by a Parallelepipedic Magnet of Various and Uniform Polarization

Ravaud¹,

Lemarquand²

2009

PIER

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Abstract-This paper deals with the modeling of parallelepipedic magnets of various polarization directions. For this purpose, we use the coulombian model of a magnet for calculating the magnetic potential in all points in space. Then, we determine the three components of the magnetic field created by a parallepiped magnet of various polarization direction. These three components and the scalar magnetic potential are also expressed in terms of fully analytical terms. It is to be noted that the formulas determined in this paper are more general that the ones established in the literature and can be used for optimization purposes. Moreover, our study is carried out without using any simplifying assumptions. Consequently, these expressions are accurate whatever the magnet dimensions. This analytical formulation is suitable for the design of unconventional magnetic couplings, electric machines and wigglers.

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Section: Introductionmentioning

confidence: 99%

Magnetic Field Produced by a Parallelepipedic Magnet of Various and Uniform Polarization

Ravaud¹,

Lemarquand²

2009

PIER

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“…Regarding automotive applications, one of the most important characteristics of magnetic fluids is their behavior in magnetic fields. The majority of these applications are for seals [1], vibration damping [2] and torque transmission [3]. In most cases, the magnitude of an external magnetic field required to activate a fluid is on the scale where the M magnetization is no longer a linear function of the H field strength.…”

Section: Introductionmentioning

confidence: 99%

Nonlinear Magnetic Properties of Magnetic Fluids for Automotive Applications

Horváth¹,

Szalai²

2020

Hung. J. Ind. Chem.

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The external magnetic field required to activate a magnetic fluid in an industrial application is sufficiently large that magnetization is no longer a linear function of the external field strength, i.e. magnetic fluids exhibit nonlinear characteristics. The aim of our research was to develop a measuring system which is capable of determining the nonlinear AC susceptibility of magnetic fluids at discrete frequencies and in the presence of a high-intensity driving magnetic field. The measurement of susceptibility is based on the determination of the change in frequency of a low-intensity field, which is generated by an LC oscillator. The application of sinusoidal excitation to the material results in a variation in the susceptibility that modulates the frequency of the measured low-intensity field and in the appearance of higher-order harmonics of the driving field. The higher-order components of the nonlinear AC susceptibility are extracted from the measured response by Fourier analysis. By applying the measuring system, the nonlinear susceptibility of water-based ferrofluids (Ferrotec's EMG 700) and its dependence on the magnetic field strength were investigated.

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“…Ferrofluids are also used in electrodynamic loudspeakers in which they fulfill several functions: they ensure the airtightness, they play a heat transfer part and they work as a radial bearing. Furthermore, a ferrofluid seal can replace the loudspeaker suspension and leads to a better linearity of the cone movement [25]- [29].…”

Section: Introductionmentioning

confidence: 99%

Magnetic pressure and shape of ferrofluid seals in cylindrical structures

Ravaud

Lemarquand

2009

Journal of Applied Physics

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This paper presents a three-dimensional analytical model for studying the shape and the pressure of ferrofluid seals submitted to intense magnetic fields produced by permanent magnet ironless structures. This three-dimensional analytical approach is based on the exact calculation of the magnetic field components created by ring permanent magnets whose polarizations are either radial or axial. We assume that the ferromagnetic particles of the ferrofluid are saturated and the static behaviour of the ferrofluid seal depends on both the magnetic field produced by the permanent magnets and the saturation magnetization of the ferrofluid particles. In our applications, ferrofluid seals are always submitted to very high magnetic fields. Consequently, the accurate knowledge of the ferrofluid seal shape as well as the magnetic pressure inside the ferrofluid seal is very useful for the design of devices using both permanent magnets and ferrofluid seals. It is emphasized here that our structures are completely ironless and thus, there are no iron-base piston for these structures. Then, this paper makes a review of the main structures using ring permanent magnets and ferrofluid seals. For each ironless structure, the shape and the pressure of the ferrofluid seals are determined. To our knowledge, this way of characterizing the static behaviour of ferrofluid seals submitted to intense magnetic fields appears for the first time in the literature. Indeed, we think that a three-dimensional analytical model is interesting for such a study because it is simple to use and has a very low computational cost.

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Mechanical Properties of a Ferrofluid Seal: Three-Dimensional Analytical Study Based on the Coulombian Model

Cited by 5 publications

References 32 publications

Magnetic Field Produced by a Parallelepipedic Magnet of Various and Uniform Polarization

Magnetic Field Produced by a Parallelepipedic Magnet of Various and Uniform Polarization

Nonlinear Magnetic Properties of Magnetic Fluids for Automotive Applications

Magnetic pressure and shape of ferrofluid seals in cylindrical structures

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