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1
Content available Method of Research on the Dynamic Viscosity of Magnetic Fluids at High Shear Rate
Szczęch Marcin, Horak Wojciech
Tribologia
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2021
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nr 1
53--63
EN
Magnetic fluids have an important position in the design of technical systems due to their unique properties. They are used primarily in mechanical energy dissipation systems, i.e. brakes and vibration dampers, as well as in the design of seals. In many applications, the magnetic fluid operates at high flow velocities through narrow slots. Therefore, there is a need to determine the rheological properties of this type of substance at high shear rates. Due to the high density of magnetic fluids and the associated occurrence of mass forces, as well as the requirements regarding the distribution of the magnetic field, the measurement of the viscosity of magnetic fluids at high shear rates is extremely difficult when conventional measuring systems are used. The paper presents a proposal for a new measuring system and a method to determine the viscosity of magnetic fluids at high shear rates, as well as the results of research on the possibility of using the presented structure in the case of ferrofluids.
PL
Ciecze magnetyczne ze względu na swoje unikatowe właściwości mają ugruntowaną pozycję w konstrukcji układów technicznych. Znalazły zastosowanie przede wszystkim w systemach dyssypacji energii mechanicznej, tj. hamulcach i amortyzatorach drgań, jak również w konstrukcji uszczelnień. W wielu aplikacjach ciecz magnetyczna pracuje w warunkach wysokich prędkości przepływu przez wąskie szczeliny. W związku z tym istnieje potrzeba wyznaczania właściwości reologicznych tego typu substancji przy wysokich szybkościach ścinania. Ze względu na znaczną gęstość cieczy magnetycznych i związane z tym występowanie sił masowych, jak również wymagania odnośnie do przestrzennego rozkładu pola magnetycznego pomiar lepkości cieczy magnetycznych w wysokich szybkościach ścinania w przypadku zastosowania konwencjonalnych układów pomiarowych jest istotnie utrudniony. W pracy przedstawiono propozycję nowego układu pomiarowego, metody pomiaru lepkości cieczy magnetycznych w wysokich szybkościach ścinania oraz wyniki badań dotyczących możliwości wykorzystania przedstawionej konstrukcji w przypadku ferrocieczy.
2
Content available Experimental analysis of the stability of ferrofluids based on Iron Oxide powder
Ząbek Daniel, Grzebielec Andrzej, Cmok Luca, Hribar Boštjančič Patricija, Mertelj Alenka
Inżynieria Bezpieczeństwa Obiektów Antropogenicznych
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2021
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Nr 2
1--6
EN
Ferrofluids most often consist of three components, they are: solid particles, the liquid in which they are dissolved and a substance that is supposed to prevent sedimentation - called surfacant. The biggest problem with ferrofluids is their stability. Mixtures in which one of the phases is a solid phase have a natural tendency to sedimentation. As a result, physical properties change during the use of such materials. As part of the research, it was decided to check which ferrofluid composition would be most resistant to continuous evaporation and condensation processes. Three different mixtures were analyzed. As a result of the experiment it was found that the best behavior was mixture of: iron-oxide with n-heptane and fatty acid as surfacant.
3
Content available New designs of centrifugal magnetic fluid seals for rotating shafts in marine technology
Matuszewski Leszek
Polish Maritime Research
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2019
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nr 2
33--46
EN
The centrifugal magnetic fluid seals have important advantage over the conventional centrifugal seals. They maintain very good sealing capacity at static, medium and high speeds of shaft rotation, with the increased seal lifetime, and minimum torque and static friction. These seals are particularly useful in cases when the angular shaft velocity varies and sometimes decreases to nearly or exactly zero, such as in flywheel applications, ship propeller main shafts, etc. Unique properties of the magnetic fluid give rare opportunities for application in marine design, where perfect sealing together with reliable lubrication are required. The paper presents a typical design and operation principle of a centrifugal magnetic fluid shaft seal, along with new design solutions. Not only in ocean technology and underwater robotics. Some cases of application of centrifugal magnetic fluid seals in modern sealing technology are included.
4
Content available The impact of electromagnetic radiation on the degradation of magnetic ferrofluids
Pavlík M., Kruželák L., Mikita M., Špes M., Bucko S., Lisoň L., Kosterec M., Beňa L., Liptai P.
Archives of Electrical Engineering
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2017
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Vol. 66, nr 2
361--369
EN
This article deals with magnetic nano-fluids, which are the part of transformer oil ITO 100 and their behavior is influenced by a permanent magnetic field. We performed an IRC analysis in the time domain on the three different samples. Measurements were made before and after radiation of an electromagnetic field. The main objective was to examine changes in the properties of the samples due to the influence of the electromagnetic field. The measurements depend on the orientation of the external magnetic field. This behavior occurs especially during the structuring of the nanoparticles in the sample exposed to the magnetic field. These processes change the polarization of the liquid because the nanoparticles concentration is contained in the fluid.
5
Content available Controllable fluids : materials with the ability to changing their physical properties
Bik T.
Journal of KONES
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2016
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Vol. 23, No. 2
45--51
EN
Controllable fluids (smart liquids) are the substances that change their properties under the influence of external physical fields. Changes of these liquids properties take place in a controlled manner and they are fully reversible. The ability to changing nature of work is a very important aspect that determines their vast application possibilities. It also makes they are occupying significant place in the modern engineering. Content of this report has been in turn devoted to systematization information on the properties and work of magnetically activated controllable fluids. There have been highlighted some commonalities and differences between two basic types of magnetic fluids (ferro- and magnetorheological fluids). Essential areas of controllable fluids application and their production methods have also been presented within this notice. It seems to be more than reasonable to explore this title issue using new methods of research and observations. They in fact directly create another chances for discovery unknown features or simply adapting the existing ones to current technical expectations. What are also important, smart liquids can be threaten as highly advanced materials which synthesis cover manipulation on the already known substances and do not cause any environmental pollution. Discovered over sixty years ago, they still signalize a great potential to development.
6
Content available remote Ciecze sterowalne i ich aspekt nanotechnologiczny
Bik T.
Mechanik
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2015
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R. 88, nr 11
845--849
PL
Przedstawiono charakterystykę cieczy sterowalnych ze szczególnym uwzględnieniem cieczy ferromagnetycznych, które ze względu na swój nanotechnologiczny charakter mają spory potencjał rozwojowy w ramach inżynierii mechanicznej.
EN
Properties of magnetically controllable fluids are addressed with particular attention paid to ferrofluids, which seem to promise remarkable progress in mechanical engineering due to their nanotechnological profile.
7
Content available Linear stability analysis for ferromagnetic fluids in the presence of magnetic field, compressibility, internal heat source and rotation through a porous medium
Kumar K., Singh V., Sharma S.
Journal of Theoretical and Applied Mechanics
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2015
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Vol. 53 nr 4
1067--1081
EN
The effects of magnetic field and heat source strength on thermal convection of a compressible rotating ferromagnetic fluid through a porous medium are investigated theoretically using linear stability theory. A normal mode analysis method is employed to find solutions for the fluid layer confined between parallel planes with free boundaries. The cases of stationary and oscillatory instabilities are discussed. For the stationary state, compressibility, medium porosity and temperature gradient due to heat source have destabilizing effects, whereas rotation and ratio of magnetic permeability delay the onset of convection. The magnetic field and medium permeability have both stabilizing and destabilizing effects under certain conditions. The variations in the stationary critical thermal Rayleigh number and neutral instability curves in (Ra1, x)-plane for various values of physical parameters are shown graphically to depict the stability characteristics. The sufficient conditions for the non-existence of overstability are obtained and the principle of exchange of stabilities holds true in the absence of magnetic field and rotation under certain conditions.
8
Content available remote A novel approach to measurement of permeability of magnetic fluids
Mayer D., Polcar P.
Przegląd Elektrotechniczny
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2012
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R. 88, nr 7b
229--231
EN
This paper deals with problems of permeability measurement of magnetic fluids. The low permeability of magnetic fluids bring certain problems to adequately measure their magnetic properties due to leakage flux, their liquid state makes the process even more difficult. Our approach to measure the permeability and measured properties of several fluids is presented.
PL
W artykule analizowano możliwość pomiaru przenikalności cieczy magnetycznych. Problemem są: mała przenikalność, duże strumienie rozproszenia, stan płynny. Zaprezentowano metodę pomiaru na przykładzie kilku cieczy.
9
Content available remote Nanofluid and ferrofluid slip flow in rectangular and circular microchannels and miniehanneis
Avsec J., Vitrič P., Naterer G.
Przegląd Elektrotechniczny
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2011
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R. 87, nr 3
5-8
EN
This paper has developed a formulation of fluid motion and entropy production in microchannels. We have developed the formulations for pressure driven flow, flow under electric forces and flow under ferromagnetic forces. Friction, thermal and electromagnetic irreversibilities have significance in energy efficiency of microfluid systems. The results indicate that entropy and the Second Law have practical significance in electrokinetic liquid transport through microchannels.
PL
W artykule pokazano rozwój sformułowania ruchu płynu i entropii produkowanej w mikrokanalikach. Rozwinięte zostały sformułowania dla przepływów poddanych ciśnieniu, przepływów w polu elektrycznym i przepływów poddanych siłom ferromagnetycznym. Ciśnienie, cieplna i elektromagnetyczna nieodwracalność mają istotne znaczenie dla efektywności energetycznej systemów mikroprzepływowych. Wyniki wskazują, że entropia i drugie prawo termodynamiki mają praktyczbe znaczenie w transporcie płynów elektrokinetycznych przez mikrokanaliki.
10
Ultrasonic wave propagation in magnetic composite : magnetically soft porous material fully saturated with water-based ferrofluid
Kazimierska-Drobny K., Kaczmarek M.
Elektronika : konstrukcje, technologie, zastosowania
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2007
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Vol. 48, nr 2
6-9
EN
This paper presents the results of investigation of ultrasonic wave propagation in the composite consisted of magnetically soft porous material fully saturated with water-base ferrofluid. The influence of the magnetic field on the amplitude and phase of ultrasonic waves is studied and compared to the parameters observed during wave propagation in the magnetic fluid itself.
PL
W pracy przedstawiono wyniki badań ilościowych dotyczących pomia­rów fal ultradźwiękowych, propagujących się w cieczy magnetycznej oraz w układach ciecz magnetyczna - materiał porowaty magnetycz­nie miękki. Z uwagi na obserwowany znaczny wzrost tłumienia sygna­łu ultradźwiękowego w materiale porowatym nasyconym cieczą mag­netyczną w stosunku do sygnału w samej cieczy można wnioskować, że proponowany układ jest ośrodkiem, który umożliwia sterowanie zmianami za pomocą pola magnetycznego.
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