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  • 1. Andersson, Anders G.
    et al.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Papathanasiou, T.D.
    Department of Mechanical Engineering, University of Thessaly.
    Lundström, Staffan
    Flow through a two-scale porosity material2009Ingår i: Research Letters in Materials Science, ISSN 1687-6822, E-ISSN 1687-6830, artikel-id 701512Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    Flow through a two-scale porous medium is here investigated by a unique comparison between simulations performed with computational fluid dynamics and the boundary element method with microparticle image velocimetry in model geometries.

  • 2. Andersson, Anders G.
    et al.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Papathanasiou, Thanasis
    Lundström, Staffan
    Fluid flow through porous media with dual scale porosity2008Ingår i: Proceedings of the 19th International Symposium on Transport Phenomena (ISTP-19): Reykjavik, Iceland, August 17-21, 2008 / [ed] Sigurdur Brynjolfsson; Olafur Petur Palsson; Jong H. Kim, University of Iceland, Faculty of Industrial Engineering, Mechanical Engineering and Computer Science , 2008Konferensbidrag (Refereegranskat)
    Abstract [en]

    Flow in two scale porous media takes place in applications such as advanced composites manufacturing. Knowledge of this flow is of general importance and is crucial for filtration mechanisms when functional filler-particles are added to the liquid resin impregnating the fibrous preform. Means to model and experimentally visualise this flow is here investigated. In particular simulations performed with computational fluid dynamics and the boundary element method are compared to micro particle image velocimetry in a model geometry.

  • 3. Baart, Pieter
    et al.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Contaminant particle migration in a double restriction seal2013Ingår i: Proceedings of the STLE Annual Meeting and Exhibition 2013, Detroit MI, USA., STLE , 2013, s. 125-Konferensbidrag (Refereegranskat)
    Abstract [en]

    Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile.In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication

  • 4. Baart, Pieter
    et al.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    The influence of speed, grease type, and temperature on radial contaminant particle migration in a double restriction seal2011Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 54, nr 6, s. 867-877Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Microparticle image velocimetry (μPIV) is used to measure the grease velocity profile in small seal-like geometries and the radial migration of contaminant particles is predicted. In the first part, the influence of shaft speed, grease type, and temperatures on the flow of lubricating greases in a narrow double restriction sealing pocket is evaluated. Such geometries can be found in, for example, labyrinth-type seals. In a wide pocket the velocity profile is one-dimensional and the Herschel-Bulkley model is used. In a narrow pocket, it is shown by the experimental results that the side walls have a significant influence on the grease flow, implying that the grease velocity profile is two-dimensional. In this area, a single empirical grease parameter for the rheology is sufficient to describe the velocity profile. In the second part, the radial migration of contaminant particles through the grease is evaluated. Centrifugal forces acting on a solid spherical particle are calculated from the grease velocity profile. Consequently, particles migrate to a larger radius and finally settle when the grease viscosity becomes large due to the low shear rate. This behavior is important for the sealing function of the grease in the pocket and relubrication.

  • 5.
    Baart, Pieter
    et al.
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Green, Torbjörn
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Sealing improvements by grease selection in double lip seals and labyrinth seals2012Ingår i: 17th ISC: International Sealing Conference ; Stuttgart, Germany, Sept. 13 - 14, 2012, Frankfurt am Main: Fachverband Fluidtechnik im VDMA e.V , 2012Konferensbidrag (Refereegranskat)
  • 6.
    Barabash, Victoria
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Ejemalm, Johnny
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Kuhn, Thomas
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Milz, Mathias
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Molin, Sven
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Johansson, Jonny
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, EISLAB.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Masters Programs in Space Science and Engineering in Northern Sweden2017Konferensbidrag (Refereegranskat)
  • 7.
    Duenas Dobrowolski, Jan
    et al.
    Department of Design Fundamentals and Fluid-Flow Machinery, Wrocaw University of Technology, Wrocaw, Poland.
    Gawlinski, Marek
    Department of Design Fundamentals and Fluid-Flow Machinery, Wrocaw University of Technology, Wrocaw, Poland.
    Paszkowski, Maciej
    Department of Fundamentals of Machine Design and Tribology, Wrocaw University of Technology, Wrocaw, Poland.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Experimental Study of Lubricating Grease Flow inside the Gap of a Labyrinth Seal Using Microparticle Image Velocimetry2018Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, nr 1, s. 31-40Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this study, the flow of lubricating greases in a labyrinth seal geometry is studied using microparticle image velocimetry (µPIV). The aim is to evaluate the grease velocity distribution inside the gap of a labyrinth seal and to find a relationship between the grease consistency and the transferred speed from the rotating ring in order to choose the correct grease as a sealing medium. In addition, the grease flow characteristics are important for the understanding of fracture due to grease layer displacement. For these purposes, four greases with different rheological properties were used in µPIV experiments. It was found that the grease consistency plays a crucial role in speed development as well as the grease composition and presence of a slip effect at the grease–rotating wall interface.

  • 8.
    Farré-Lladós, Josep
    et al.
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Voltas, Jordi
    Department of Graphic Expression, UPC - Technical University of Catalonia.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    The use of Rapid Prototyping techniques (RPT) to manufacture micro channels suitable for high operation pressures and µPIV2016Ingår i: Rapid prototyping journal, ISSN 1355-2546, E-ISSN 1758-7670, Vol. 22, nr 1, s. 67-76Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Purpose– This paper aims to present a new methodology to manufacture micro-channels suitable for high operating pressures and micro particle image velocimetry (μPIV) measurements using a rapid-prototyping high-resolution 3D printer. This methodology can fabricate channels down to 250 μm and withstand pressures of up to 5 ± 0.2 MPa. The manufacturing times are much shorter than in soft lithography processes. Design/methodology/approach– The novel manufacturing method developed takes advantage of the recently improved resolution in 3D printers to manufacture an rapid prototyping technique part that contains the hose connections and a micro-channel useful for microfluidics. A method to assemble one wall of the micro-channel using UV curable glue with a glass slide is presented – an operation required to prepare the channel for μPIV measurements. Once built, the micro-channel has been evaluated when working under pressure and the grease flow behavior in it has been measured using μPIV. Furthermore, the minimum achievable channels have been defined using a confocal microscopy study. Findings– This technique is much faster than previous micro-manufacturing techniques where different steps were needed to obtain the micro-machined parts. However, due to current 3D printers ' resolutions (around 50 μm) and according to the experimental results, channels smaller than 250-μm2 cross-section should not be used to characterize fluid flow behaviors, as inaccuracies in the channel boundaries can deeply affect the fluid flow behavior. Practical implications– The present methodology is developed due to the need to validate micro-channels using μPIV to lubricate critical components (bearings and gears) in wind turbines. Originality/value– This novel micro-manufacturing technique overcomes current techniques, as it requires less manufacturing steps and therefore it is faster and with less associated costs to manufacture micro-channels down to 250-μm2 cross-section that can withstand pressures higher than 5 MPa that can be used to characterize microfluidic flow behavior using μPIV.

  • 9.
    Farré-Lladós, Josep
    et al.
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    New solution to preent excessive wear in wind turbine gears2014Ingår i: Society of Tribologists and Lubrication Engineers Annual Meeting and Exhibition 2014: Lake Buena Vista, United States, 18 - 22 May 2014, Society of Tribologists and Lubrication Engineers , 2014, Vol. 2, s. 548-550Konferensbidrag (Refereegranskat)
  • 10.
    Farré-Lladós, Josep
    et al.
    Department of Mechanical Engineering, UPC - Technical University of Catalonia, KIC InnoEnergy S.E. - Location Iberia, Barcelona.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia, KIC InnoEnergy S.E. - Location Iberia, Barcelona.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    New Lubrication Device to Minimize Wear at the Pitch Gear2015Konferensbidrag (Refereegranskat)
  • 11.
    Farré-Lladós, Josep
    et al.
    Department of Mechanical Engineering, UPC - Technical University of Catalonia, KIC InnoEnergy S.E. - Location Iberia, Barcelona.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia, KIC InnoEnergy S.E. - Location Iberia, Barcelona.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    New Lubrication Device to Minimize Wear at the Pitch Gear2015Konferensbidrag (Refereegranskat)
  • 12.
    Farré-Lladós, Josep
    et al.
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casals-Terré, Jasmina
    Department of Mechanical Engineering, UPC - Technical University of Catalonia.
    Embedded Micro-nozzles in the Pitch Gear Deddendum to Minimize Wear at Zero Degree Position2015Konferensbidrag (Refereegranskat)
  • 13.
    Farré-Lladós, Josep
    et al.
    Mechanical Engineering Department, UPC - Technical University of Catalonia, Terrassa.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Casals-Terré, Jasmina
    Mechanical Engineering Department, UPC - Technical University of Catalonia, Terrassa.
    New method for lubricating wind turbine pitch gears using embedded micro-nozzles2017Ingår i: Journal of Mechanical Science and Technology, ISSN 1738-494X, E-ISSN 1976-3824, Vol. 31, nr 2, s. 797-806Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increase of power generated by wind turbines has increased the stresses applied in all of its components, thereby causing premature failures. Particularly, pitch and yaw gears suffer from excessive wear mainly caused by inappropriate lubrication. This paper presents a novel method to automatically lubricate the wind turbine pitch gear during operation. A micro-nozzle to inject fresh grease continuously between the teeth in contact was designed, manufactured, and installed in a test bench of a 2 MW wind turbine pitch system. The test bench was used to characterize the fatigue behavior of the gear surface using conventional wind turbine greases under real cyclic loads. Measurements of wear evolution in a pitch gear with and without micro-nozzle show a decrease of 70 % of the wear coefficient after 2×104 cycles.

  • 14.
    Green, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Baart, Pieter
    Westerberg, Lars-Göran
    Lundström, Staffan
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Li, Jinxia
    A new method to visualize grease flow in a double restriction seal using microparticle image velocimetry2011Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 54, s. 784-792Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A new method to visualize and quantify grease flow in between two sealing lips or, in general, a double restriction seal is presented. Two setups were designed to mimic different types of seals; that is, a radial and an axial shaft seal. The flow of the grease inside and in between the sealing restrictions was measured using microparticle image velocimetry. The results show that grease flow due to a pressure difference mainly takes place close to the rotating shaft surface with an exponentially decaying velocity profile in the radial direction. Consequently, contaminants may be captured in the stationary grease at the outer radius, which explains the sealing function of the grease.

  • 15.
    Green, Torbjörn
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Baart, Pieter
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Li, Jinxia
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Visualisering och kvantifiering av fettströmning i lagertätningar med µPIV2011Konferensbidrag (Övrigt vetenskapligt)
  • 16.
    Hamedi, Naser
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Modelling of Flexible Fibres in Viscous Fluid Flow2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    The current study relates to the development of a multiphase model of flexible fibre suspensions. An understanding of the rheology and dynamics of the deformation of such suspension is desirable in order to be able to fully disclose the flow behaviour from very low to very high shear rates. We present an approach for numerically simulating the dynamics of flexible fibres employing a particle-level method. This is performed by investigating the fibre dynamics against several orbit classes - i.e. rigid, springy, flexible and complex rotation of the fibres [1-3] enabling the model to have all degrees of freedom (translation, rotation, bending and twisting). The three-dimensional Navier-Stokes equations which describes the fluid motion are employed while the fibrous phase of the fluid is modeled as chains of fiber segments interacting with the fluid through viscous- and drag forces. The simulations are performed using OpenFOAM and the numerical outcomes are validated against experimental data.The purpose of the modelling framework applied in this work is to enable the numerical model to be extended to a 4-way coupling model, capturing shear thinning, shear thickening and the yield stress properties of a fibrous fluid suspension.

  • 17.
    Hamedi, Naser
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    On the deformation of fibrous suspensions2019Ingår i: Transactions of the Nordic Rheology Society, Nordic Rheology Society , 2019, Vol. 27Konferensbidrag (Refereegranskat)
    Abstract [en]

    An understanding of the rheology and dynamics of the deformation of fibrous suspension as a multiphase fluid is important in order to be able to fully disclose the flow behaviour from very low to very high shear rates. In this study, a flexible fibre model has been implemented in an open source Computational Fluid Dynamics code. The three-dimensional Navier-Stokes equations which describe the fluid motion are employed while the fibrous phase of the fluid is modeled as chains of fiber segments interacting with the fluid through viscous- and drag forces. The aim of this study is to investigate the fibre dynamics against several orbit classes - i.e. rigid, springy, flexible and complex rotation of the fibres1-3 enabling the model to have all degrees of freedom - translation, rotation, bending and twisting. The simulations are performed using the OpenFOAM open source software.

  • 18.
    Hamedi, Naser
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    On the Interaction of Side-By-Side Circular Cylinders in Viscoplastic Fluids2019Ingår i: Fluids, ISSN 2311-5521, Vol. 4, nr 2, artikel-id 93Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this paper, the static interaction of a train of three cylinders in a Bingham fluid is studiednumerically using Computational Fluid Dynamics. The variation of drag forces for the cylinders inseveral configurations is investigated. Positions of the particles in relation to the reference particleare recognized by the separation distance between the cylinders. A steady state field is considered,with Bingham numbers between 5 and 150. Several separation distances (d) were considered, such that2.0D d 6.0D where D is the cylinder diameter. The Reynolds number was chosen in the range of5 Re 40. In particular, the eect of the separation distance, Reynolds number and Bingham numberon the shape and size of the unyielded regions was investigated. The functional dependence of thisregion and the drag coecient is explored. The present results reveal the significant influence of thegap between the cylinders on the drag force and the shape of the unyielded regions surrounding thecylinders. It was found that there are several configurations in which the drag forces over the first andthe third cylinders are almost equal depending on variation of the Bi, Re and the separation distance.

  • 19. Johansson, Simon
    et al.
    Geza, Vadims
    Faculty of Physics and Mathematics, University of Latvia.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Jakovics, Andris
    Faculty of Physics and Mathematics, University of Latvia.
    Characteristics of flow and temperature distribution in a Ruthner process2010Ingår i: Proceedings of Modeling for Material Processing, 6th International Scientific Colloquium: Modelling for maerial processing, Rīga, September 16-17, 2010, University of Latvia Press, 2010, s. 317-322Konferensbidrag (Refereegranskat)
    Abstract [en]

    This study is devoted to CFD modelling of the gas flow and particle dynamics inside the reactor of a furnace used for regeneration of hydrochloric acid from iron chloride - a rest product from the pickling process in the steel industry. The understanding of the dynamics inside the reactor has shown to be of great importance in order to optimize the process. So far the process has been a black box, where only the inflow conditions are known together with the quality of the final product. In this work the gas flow is resolved together with the thermal distribution and the particle trajectory for the injected acid molecules.

  • 20.
    Johansson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Simuleringar av dyspositionens inverkan på flöde och temperturdistribution i en ruthner process2011Konferensbidrag (Övrigt vetenskapligt)
    Abstract [sv]

    Saltsyra (HCl) används inom stålindustrin för att beta järnoxider (Fe2O3) efter varmvalsning av plåt innan den förädlas i produktionslinan. Stora mängder HCl förbrukas, vilket både är kostsamt och miljöfarlig om den inte återvinns. Återvinningen sker oftast på stålverken med en metod som kallas Ruthner process. Den kan illustreras av en cylindrisk ugn med konisk nedre del, där det strax ovanför den koniska delen sitter naturgasbrännare tangentiellt till ugnen. Den förbrukade saltsyran, som består av vatten (H2O) och järnklorid (FeCl2), tillförs genom en till fyra dysor i toppen av ugnen. Återvinningen sker - något förenklat - genom att H2O först förångas från dropparna, därefter reagerar FeCl2 med syre (O2) och H2O och bildar HCl och Fe2O3. HCl återförs till betningsprocessen och Fe2O3 kan exempelvis säljas till elektronikindustrin.Denna studie syftar till att öka förståelsen av processen så att det i framtiden är möjligt att säkerställa god kvalité av restprodukten Fe2O3. Simuleringar görs i Ansys CFX med en tvåvägskopplad Euler/Lagrange-ansats där Eulerfasen består av gas och dropparna av förbrukad HCl är på Lagrangeform. Produkten från naturgasbrännarna ges som randvillkor till inloppet. I modellen är det första steget i återvinningsprocessen då droppar förångas implementerad. Även lyftkraft p.g.a. olika gastemperaturer, energiförluster genom väggar, och dragkraft på partiklar är implementerade i modellen. Som turbulensmodell används k-ε.Ur Figur 2 ses att både temperaturfördelning och hastighetsprofil förändras med olika dyspositioner. En korrelation mellan bilderna finns; i områden med låg temperatur är hastigheten riktad nedåt. Med dysan placerad 3,5 m från centrum förskjuts dock området för negativ vertikal hastighet bort från väggen. Detta beroende på att den varma gasen från brännare stiger längs väggen. De stora skillnaderna i temperaturfördelning är att dysposition 0.5 m från centrum ger en hög utloppstemperatur samt att dysposition 0.5 m och 3.5 m ger en högre temperatur i botten. Tendensen i hastighetsprofilen är lika för de tre fallen med dysan närmast väggen. När dysan placeras i mitten blir det ett kallras i centrum. För att få en klarare bild av processen krävs det även att partiklar analyseras samt att i framtiden även implementera kemiska reaktioner.

  • 21.
    Johansson, Simon
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Gas and particle flow in a spray roaster2014Ingår i: Journal of Applied Fluid Mechanics, ISSN 1735-3572, E-ISSN 1735-3645, Vol. 7, nr 2, s. 187-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the steel industry, waste hydrochloric acid is produced through the process to pickle steel slabs for removal of corrosion. Regenerated hydrochloric acid is obtained by separating the chloride gas from the waste product through spray roasting. This process also produces a by-product in the form of iron oxide which is sold to different industries. The present study is a continuation of a study arising from the need to better understand the dynamics inside the regeneration reactor, which in turn will improve possibilities to optimize the regeneration process, which to date has been manually adjusted by trial and error. In this study the velocity and temperature distribution inside the reactor is numerically modelled together with the droplet motion through the reactor. The main objective is to investigate the influence of a changed spray nozzle position on the flow characteristics of the continuous and dispersed phase, and the relation between temperature and energy efficiency and the regeneration process. Numerical models of the type of flow present in the regeneration reactor are not represented to any major extent in the literature, making the present study relevant to the engineers and researchers active in the steel industry and the application in question.

  • 22.
    Karami, Fatemeh
    et al.
    Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran.
    Nadooshan, Afshin Ahmadi
    Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Tadi Beni, Yaghoub
    Department of Mechanical Engineering, Shahrekord University, Shahrekord, Iran.
    Nano-fluid flow in a catheterized tapered artery: Consistent couple stress-theory and wall slip2019Ingår i: Journal of thermal analysis and calorimetry (Print), ISSN 1388-6150, E-ISSN 1588-2926, Vol. 137, nr 1, s. 327-342Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This study was conducted with the aim of investigating the Newtonian nanofluid flow in a catheterized tapered artery through using a completely consistent couple stress theory. In the process of carrying out this study, the slip condition at the arterial wall and the catheter, as well as, the permeability was taken into account. Further, the velocity, temperature, and concentration profiles were analytically modeled and the effect of the length scale on these profiles was well presented through the way it influences small-scale flows. The effect of the slip condition at the artery and catheter walls on the velocity was also investigated and revealed that any increase in the velocity leads to an increase in the slip velocity. Furthermore, the effect of other parameters such as the catheter diameter, shape, and height of the stenosis on these profiles was explored for all three artery geometries, i.e., diverging tapered artery, converging tapered artery, and non-tapered artery, respectively. The findings suggested that any increase in the catheter diameter and stenosis height can decrease the velocity and nanoparticle concentration profiles, while the temperature profile increases. It was also found that by increasing the stenosis shape parameter the velocity and concentration profiles increase and temperature decreases.

  • 23. Kluge, Jimmy
    et al.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Ljung, Anna-Lena
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nyman, Tony
    Saab Aeronautics, SE-582 54 Linköping, SWEDEN.
    An Experimental Study of Temperature Distribution in an Autoclave2016Ingår i: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, nr 7, s. 566-578Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, the temperature distribution on an industrial mold tool is monitored during autoclave runs with three settings. In one of the settings, the temperature and pressure follow a scheme used in real moldings, while in the other two cases, the temperature is increased as fast as possible with and without an applied pressure. The temperature difference over the tool is relatively large and varies between 29℃ and 76℃ validating a detailed investigation of the temperature at different points. Two results of this are that positions on the up-stream side of the tool are heated faster than positions down-stream and the heating over the tool is symmetric while that within is asymmetric. Roughly estimated heat transfer coefficients reveal that the temperature ramping has no significant effect on the local heat transfer coefficients while the applied pressure more than doubled them. In addition flow field measurements with particle image velocimetry are performed, revealing a very slow flow near the roof of the autoclave and a velocity peak near the floor of it, indicating that the flow profile within the autoclave and variation in heat transfer coefficients should be considered in autoclave simulations.

  • 24. Kluge, Jimmy
    et al.
    Lundström, Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nyman, Tony
    Saab Aeronautics, SE-582 54 Linköping, SWEDEN.
    Modelling Heat Transfer Inside an Autoclave: Effect of Radiation2016Ingår i: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 35, nr 14, s. 1126-1142Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this work, computational fluid dynamics simulations are performed to predict the temperature distribution on a part during an autoclave run. Data from an experimental study are used as input to the simulations and also for comparison with the numerical results. A conjugate heat transfer approach was used for the simulations, where best agreement with experiments was obtained from the simulation that included thermal radiation and utilized an experimentally obtained velocity profile as inlet velocity. A yet more detailed inlet velocity profile and more advanced turbulent model could result in an even better agreement.

  • 25. Kluge, Jimmy
    et al.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Olofsson, Kurt
    Swerea SICOMP AB.
    Compression moulding of sheet moulding compound: Modelling with computational fluid dynamics and validation2015Ingår i: Journal of reinforced plastics and composites (Print), ISSN 0731-6844, E-ISSN 1530-7964, Vol. 34, nr 6, s. 479-492Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Compression moulding experiments of sheet moulding compound, visual observations of a vacuum test with prepregs and numerical models with two main approaches for computational fluid dynamics simulations of the mould filling phase are presented. One assumes that there are layers near the mould surfaces with much less viscosity and the other only use one viscosity model. The numerical experiments showed that the pressure could be accurately predicted with both approaches. The property necessary to predict correct pressure with altered mould closing velocities was that the bulk material had to obey shear-thinning effects. Preheating effects before compression were neglected, but altering the heating time until the prepreg was assumed to start flow had a significant effect. The experiments confirmed that the pressure is predominantly affected by the mould closing velocity. Regardless of the considered process settings, a first pressure top always appeared approximately at the logarithmic strain 0.25. A second top was associated with a slowdown of the press. The location of this was affected by the velocity and the vacuum, the latter indicating that vacuum assistance prevents a build-up of back pressure. Furthermore, heated prepreg above a critical temperature is observed to swell immediately as vacuum assistance is applied.

  • 26.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Grease Free Surface Flow on a Rotating Plate: a Combined Experimental and Analytical Analysis2014Konferensbidrag (Refereegranskat)
  • 27.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Green, Torbjörn
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Baart, Pieter
    µPIV measurement of grease velocity profiles in channels with two different types of flow restrictions2012Ingår i: Tribology International, ISSN 0301-679X, E-ISSN 1879-2464, Vol. 54, s. 94-99Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Grease is commonly used to lubricate various machine components such as rolling bearings and seals. In this paper the flow of lubricating grease passing restrictions is described. Such flow occurs in rolling bearings during relubrication events where the grease is flowing in the transverse (axial) direction through the bearing and is hindered by guide rings, flanges et cetera, as well as in seals where transverse flow occurs, for example during so-called breathing caused by temperature fluctuations in the bearing. This study uses a 2D flow model geometry consisting of a wide channel with rectangular cross-section and two different types of restrictions to measure the grease velocity vector field, using the method of Micro Particle Image Velocimetry. In the case of a single restriction, the horizontal distance required for the velocity profile to fully develop is approximately the same as the height of the channel. In the corner before and after the restriction, the velocities are very low and part of the grease is stationary. For the channel with two flow restrictions, this effect is even more pronounced in the “pocket” between the restrictions. Clearly, a large part of the grease is not moving. This condition particularly applies to the cases with a low-pressure drop and where high consistency grease is used. In practice this means that grease is not replaced in such “corners” and that some aged/contaminated grease will remain in seal pockets.

  • 28.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Zhmud, Boris
    Applied Nano Surfaces.
    Rheology of Lubricating Grease2015Ingår i: Lube Magazine, ISSN 1744-5418, Vol. 126, s. 12-18Artikel i tidskrift (Refereegranskat)
  • 29.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Green, Torbjörn
    Lundström, Staffan
    Lugt, Piet
    Baart, Pieter
    Measurements of grease flow in channels with restrictions using μPIV2010Ingår i: 14th Nordic Symposium on Tribology: NORDTRIB 2010 : Storforsen, Sweden, June 8-11, 2010, Luleå: Luleå tekniska universitet, 2010Konferensbidrag (Refereegranskat)
    Abstract [en]

    Grease is commonly used to lubricate various machine components such as rolling element bearings, open gears etc. Better understanding of the flow properties of grease will contribute to understanding the lubrication mechanism in bearings and flow in lubrication systems. In an earlier paper Micro Particle Image Velocimetry (μPIV) techniques were used to study the flow in a rectangular channel. The present paper is an extension of this work where restrictions were applied in such a channel, which creates a much more complex velocity field. The grease is seeded with fluorescent particles, which are illuminated by a double-pulsed laser. The test geometries that are used in this study are a channel with one flat restriction and one with two flow restrictions in a similar channel. The stationary grease mass-flow and the two dimensional velocity fields have been monitored for different pressure drops. For the channel with one flat restriction, the flow was measured to be symmetric at the inlet and outlet, and the distance for the flow to fully develop is comparable with the height of the channel; Slow motion was followed near the step corner at the inlet. For the channel with two flow restrictions, the vector profiles show that the maximum velocity appears at the restrictions; In-between the two restrictions, a part of the grease is not moving. This particularly applies to cases with low-pressure drop and where high consistency grease was used.

  • 30.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Experimental study of free surface grease flow subjected to centrifugal forces2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to improve the understanding of grease flow in various applications such as gears, seals and rolling bearings, the free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease was subjected to a centrifugal force. The grease flow and mass loss was measured for greases with different rheology on different surfaces and with surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type and yield stress, while the impact of the surface material and roughness is less pronounced. The mass loss is shown to be influenced both by the rheology of the grease and the surface material

  • 31.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    SKF ERC.
    Baart, Pieter
    SKF ERC.
    Lubricating Grease Shear Flow and Boundary Layers in a Concentric Cylinder Configuration2015Konferensbidrag (Refereegranskat)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study, grease flow is visualized using micro Particle Image Velocimetry (μPIV). The experimental setup includes a concentric cylinder configuration with a rotating shaft to simulate the grease flow in a double restriction seal geometry with two different grease pocket sizes. It is shown that the grease is partially yielded in the large grease pocket geometry and fully yielded in the small grease pocket. For the small grease pocket, it is shown that three distinct grease flow layers are present: a high shear rate region close to the stationary wall, a bulk flow layer, and a high shear rate boundary region near the rotating shaft. The grease shear thinning behavior and its wall slip effects have been identified. The μPIV experimental results have been compared with a numerical model for both the large and small gap size. It is shown that the flow is close to one-dimensional in the center of the small pocket. A one-dimensional analytical model based on the Herschel-Bulkley rheology model has been developed, showing good agreement with the measured velocity profiles in the small grease pocket. Furthermore, wall slip effects and shear banding are observed, where the latter imply that using the assumption of uniform shear in conventional concentric cylinder rheometers may result in erroneous rheological results.

  • 32.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lugt, Piet
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lubricating grease shear flow and boundary layers in a concentric cylinder configuration2014Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 57, nr 6, s. 1106-1115Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rolling bearings, seals, and gears. Understanding the flow dynamics of grease is relevant for the prediction of grease distribution for optimum lubrication and for the migration of wear and contaminant particles. In this study, grease flow is visualized using microparticle image velocimetry (μPIV). The experimental setup includes a concentric cylinder configuration with a rotating shaft to simulate the grease flow in a double restriction seal geometry with two different grease pocket sizes. It is shown that the grease is partially yielded in the large grease pocket geometry and fully yielded in the small grease pocket. For the small grease pocket, it is shown that three distinct grease flow layers are present: a high shear rate region close to the stationary wall, a bulk flow layer, and a high shear rate boundary region near the rotating shaft. The grease shear thinning behavior and its wall slip effects have been identified. The μPIV experimental results have been compared with a numerical model for both the large and small gap size. It is shown that the flow is close to one-dimensional in the center of the small pocket. A one-dimensional analytical model based on the Herschel-Bulkley rheology model has been developed, showing good agreement with the measured velocity profiles in the small grease pocket. Furthermore, wall slip effects and shear banding are observed, where the latter imply that using the assumption of uniform shear in conventional concentric cylinder rheometers may result in erroneous rheological results.

  • 33.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Design of test rig for visualizations of cylindrical shear and pressure driven Couette flow using μPIV2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    Couette flow is often encountered in concentric cylinder application such as rheometers etc. Being able to visualize such flows is of interest both from a fundamental point of view to understand the dynamics of complex fluids, but also in specific applications such as lubricants flowing through seal geometries. In this study a concentric cylinder test rig has been designed to visualize Couette flow in both radial and axial direction using micro Particle Image Velocimetry. The rig allows for control of the flow motion; the rotating inner cylinder creates a peripheral flow and an applied pressure in the axial direction creates a pressure driven flow. Thus, a single flow direction or a combination of directions can be analyzed. To demonstrate the technique a flow of a non-Newtonian shear thinning fluid in the form of lubricating grease was investigated and discussed. It is found that it is possible to capture the yield behavior of the grease, with regions of fully and partially yielded flow visible. The influence of temperature creep flow is also presented. Grease with both high and low yield stress are measured and compared could be measured and compared in a pocket with variable size. Furthermore, non-homogeneous effects such as shear banding and wall slip can be visualized. The test rig has thus a high potential to investigate the influence of wall material and wettability between fluids and the housing on the flow and wall slip behavior as long as the fluid is optically transparent.

  • 34.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Grease free surface flow on a rotating plate2014Konferensbidrag (Refereegranskat)
    Abstract [en]

    In order to improve the understanding of grease flow in various applications such as gears, seals and rolling element bearings, free surface flow of different greases under different running conditions has been investigated. A rotating disc has been used to study grease flow as the grease is subjected to a centrifugal force. The adhesion and mass loss was detected for greases with different rheology on different surfaces and surface textures. It is shown that the speed at which grease starts to move is mostly determined by grease type, yield stress and bleeding properties rather than surface material. Also, the surface adhesion is shown to be influenced both by the rheology of the grease and the surface material.

  • 35.
    Li, Jinxia
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Baart, Pieter
    SKF Engineering & Research Center, Nieuwegein.
    Lugt, Piet
    SKF Engineering & Research Center, Nieuwegein.
    Lubricating grease shear flow and boundary layers in a concentric cylinder configuration2013Ingår i: Proceedings of the 3rd International Tribology Symposium of IFoMM (International Federation for the Promotion of Mechanism and Machine Science), Luleå, March 19-21, 2013, 2013Konferensbidrag (Refereegranskat)
    Abstract [en]

    Grease is extensively used to lubricate various machine elements such as rollingbearings, seals, and gears. Understanding the flow dynamics of grease is relevant forthe prediction of the grease distribution for optimum lubrication and the migration ofwear- and contaminant particles. In this study grease flow is visualized using themethod of micro Particle Image Velocimetry; the experimental setup comprises aconcentric cylinder with rotating shaft to simulate the grease flow in a DoubleRestriction Seal (DRS) geometry with two different grease pocket heights. It is shownthat grease may be partially yielded in the large grease pocket geometry and fullyyielded in the small grease pocket geometry. For the small grease pocket geometry, itis shown that three distinct grease flow layers are present: a high shear rate regionclose to the stationary wall, a bulk flow layer, and a high shear rate boundary regionnear the rotating shaft. The grease shear thinning behaviour and its wall slip effectshave been detected and discussed.

  • 36.
    Olsson, Jimmy
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Lundström, T. Staffan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Nyman, Tonny
    Saab Aeronautics, SE-582 54 Linköping, SWEDEN.
    Flow and heat transfer inside an autoclave2012Ingår i: Proceedings of the 11th International Conference on Flow Processing in Composite Materials, 2012Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    This work, that involves both experiments and numerical simulations, concerns autoclave molding. An autoclave is basically a pressure vessel, where the entrapped and often highly compressed gas is heated and circulated in order to heat the components that have been placed inside the vessel. In the autoclaveprocess, the desirable state would be that an even and optimal temperature existed in the whole part that is manufactured. Unfortunately, this is not always the case. All in all we need to get a better understanding of the flow inside an autoclave and the convective heat transfer from the heated gas to the composite components. In this work we have therefore investigated the flow behavior by performing qualitative measurements with particle image velocimetry inside an autoclave. The concept is to dope the gas within the autoclave with smoke and illuminate the smoke with a thin sheet of laser light. Captured images of the moving smoke are then cross correlated to give velocity fields. We have also investigated the heat transfer to the tool by measuring the temperature at multiple locations during heating. The obtained velocity field is used to produce inlet condition for the simulations, performed with Computational Fluid Dynamics, which subsequently are compared with the experimentally obtained tool temperature. The simulation technique may then be used to optimize both the tools, and the actual location of the tools inside the autoclave in order to improve quality and reduce costs.

  • 37.
    Sarkar, Chiranjit
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Höglund, Erik
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    Lundström, Staffan T.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Numerical simulations of lubricating grease flow in a rectangular channel with and without restrictions2018Ingår i: Tribology Transactions, ISSN 1040-2004, E-ISSN 1547-397X, Vol. 61, nr 1, s. 144-156Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This article presents numerical simulations of the laminar flow of lubricating greases in a channel with rectangular cross section. Three greases with different consistencies (NLGI grades 00, 1, and 2) have been considered in three different configurations composed of a rectangular channel without restrictions, one rectangular step restriction, and one double-lip restriction. The driving pressure drop over the channel spans from 30 to 250 kPa. The grease rheology is described by the Herschel-Bulkley rheology model, and both the numerical code and rheology model have been validated with analytical solutions and flow measurements using micro-particle image velocimetry.

  • 38.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics.
    Gunell, Herbert
    Department of Physics, Umeå University, Umeå, Sweden. Belgian Institute for Space Aeronomy, Brussels, Belgium.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Maskinelement.
    De Spiegeleer, Alexandre
    Department of Physics, Umeå University, Umeå, Sweden.
    Ebihara, Yusuke
    Research Institute for Sustainable Humanosphere, Kyoto University, Japan, Gokasho, Uji, Kyoto.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Slapak, Rikard
    EISCAT Scientific Association, Kiruna, Sweden.
    The fate of O+ ions observed in the plasma mantle and cusp: particle tracing modelling and Cluster observations2019Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576Artikel i tidskrift (Refereegranskat)
  • 39.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instiutet for rymdfysik, Kiruna, Sweden.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Instiutet for rymdfysik, Kiruna, Sweden.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, M
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Westerberg, Lars Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Relative outflow enhancements during major geomagnetic storms: Cluster observations2017Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 5, nr 6, s. 1341-1352Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The rate of ion outflow from the polar ionosphere is known to vary by orders of magnitude, depending on the geomagnetic activity. However, the upper limit of the outflow rate during the largest geomagnetic storms is not well constrained due to poor spatial coverage during storm events. In this paper, we analyse six major geomagnetic storms between 2001 and 2004 using Cluster data. The six major storms fulfil the criteria of Dst 100 nT or Kp 7C. Since the shape of the magnetospheric regions (plasma mantle, lobe and inner magnetosphere) are distorted during large magnetic storms, we use both plasma beta and ion characteristics to define a spatial box where the upward OC flux scaled to an ionospheric reference altitude for the extreme event is observed. The relative enhancement of the scaled outflow in the spatial boxes as compared to the data from the full year when the storm occurred is estimated. Only OC data were used because HC may have a solar wind origin. The storm time data for most cases showed up as a clearly distinguishable separate peak in the distribution toward the largest fluxes observed. The relative enhancement in the outflow region during storm time is 1 to 2 orders of magnitude higher compared to less disturbed time. The largest relative scaled outflow enhancement is 83 (7 November 2004) and the highest scaled OC outflow observed is 2 1014 m2 s1 (29 October 2003).

  • 40.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna.
    Slapak, Rikard
    EISCAT Scientifc Association, Kiruna.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics, Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Dandouras, Iannis
    IRAP, Université de Toulouse, CNRS, UPS, CNES, Toulouse, France.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Earth atmospheric loss through the plasma mantle and its dependence on solar wind parameters2019Ingår i: Earth, Planets and Space, Vol. 71, nr 70Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Atmospheric loss and ion outfow play an important role in the magnetospheric dynamics and in the evolution of the atmosphere on geological timescales—an evolution which is also dependent on the solar activity. In this paper, we investigate the total O+ outfow [s−1 ] through the plasma mantle and its dependency on several solar wind param‑ eters. The oxygen ion data come from the CODIF instrument on board the spacecraft Cluster 4 and solar wind data from the OMNIWeb database for a period of 5 years (2001–2005). We study the distribution of the dynamic pressure and the interplanetary magnetic feld for time periods with available O+ observations in the plasma mantle. We then divided the data into suitably sized intervals. Additionally, we analyse the extreme ultraviolet radiation (EUV) data from the TIMED mission. We estimate the O+ escape rate [ions/s] as a function of the solar wind dynamic pressure, the interplanetary magnetic feld (IMF) and EUV. Our analysis shows that the O+ escape rate in the plasma mantle increases with increased solar wind dynamic pressure. Consistently, it was found that the southward IMF also plays an important role in the O+ escape rate in contrast to the EUV fux which does not have a signifcant infuence for the plasma mantle region. Finally, the relation between the O+ escape rate and the solar wind energy transferred into the magnetosphere shows a nonlinear response. The O+ escape rate starts increasing with an energy input of approxi‑ mately 1011W.

  • 41.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics (IRF), Kiruna, Sweden .
    Slapak, Rikard
    EISCAT Scientific Association, Kiruna.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik. Swedish Institute of Space Physics (IRF), Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics (IRF), Kiruna.
    Dandouras, Iannis
    Université de Toulouse, CNRS, UPS, CNES, Toulouse, France.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Earth atmospheric loss through the plasma mantle and its dependence onsolar wind parameters2019Konferensbidrag (Refereegranskat)
  • 42.
    Schillings, Audrey
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Slapak, Rikard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Atmospheric loss during major geomagnetic storms: Cluster observations2017Konferensbidrag (Refereegranskat)
  • 43.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Swedish Institute of Space Physics, Kiruna.
    Schillings, Audrey
    Swedish Institute of Space Physics, Kiruna.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Dandouras, Iannis
    CNSR, Institut de Recherche en Astrophysique et Planetologie, Toulouse.
    Atmospheric outflow from the terrestrial magnetosphere: implications forescape on evolutionary time scales2017Konferensbidrag (Refereegranskat)
  • 44.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    A statistical study on O+ flux in the dayside magnetosheath2013Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 31, s. 1005-1010Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Studies on terrestrial oxygen ion (O+) escape into the interplanetary space have considered a number of different escape paths. Recent observations however suggest a yet insufficiently investigated additional escape route for hot O+: along open magnetic field lines in the high altitude cusp and mantle. Here we present a statistical study on O+ flux in the high-latitude dayside magnetosheath. The O+ is generally seen relatively close to the magnetopause, consistent with observations of O+ flowing primarily tangentially to the magnetopause. We estimate the total escape flux in this region to be ~ 7 × 1024 s−1, implying this escape route to significantly contribute to the overall total O+ loss into interplanetary space.

  • 45.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Eriksson, Anders
    Swedish Institute of Space Physics / Institutet för rymdfysik.
    Observations of oxygen ions in the dayside magnetosheath associated with southward IMF2012Ingår i: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 117Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We present a case study of high energy oxygen ions (O+) observed in the dayside terrestrial magnetosheath, in the southern hemisphere. It is shown that the presence of O+ is strongly correlated to the IMF direction: O+ is observed only for Bz<0. Three satellites observe O$^+ immediately at both sides of the magnetopause and about 2 RE outside the magnetopause. These conditions indicate escape along open magnetic field lines. We show that if outflowing O+ is heated and accelerated sufficiently in the cusp, it takes 15-20 minutes for it to reach the magnetopause, allowing the ions to escape along newly opened field lines on the dayside. Earlier studies show evidence of strong heating and high velocities in the cusp and mantle at high altitudes, strengthening our interpretation. The observed magnetosheath O+ fluxes are of the same order as measured in the ionospheric upflow, which indicates that this loss mechanism is significant when it takes place.

  • 46.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Larsson, Richard
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    O+ transport in the dayside magnetosheath and its dependence on the IMF direction2015Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 33, s. 301-307Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent studies have shown that the escape of oxygen ions (O+) into the magnetosheath along open magnetic field lines from the terrestrial cusp and mantle is significant. We present a study of how O+ transport in the dayside magnetosheath depends on the interplanetary magnetic field (IMF) direction. There are clear asymmetries in the O+ flows for southward and northward IMF. The asymmetries can be understood in terms of the different magnetic topologies that arise due to differences in the location of the reconnection site, which depends on the IMF direction. During southward IMF, most of the observed magnetosheath O+ is transported downstream. In contrast, for northward IMF we observe O+ flowing both downstream and equatorward towards the opposite hemisphere. We observe evidence of dual-lobe reconnection occasionally taking place during strong northward IMF conditions, a mechanism that may trap O+ and bring it back into the magnetosphere. Its effect on the overall escape is however small: we estimate the upper limit of trapped O+ to be 5%, a small number considering that ion flux calculations are rough estimates. The total O+ escape flux is higher by about a factor of 2 during times of southward IMF, in agreement with earlier studies of O+ cusp outflow.

  • 47.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales2017Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 35, nr 3, s. 721-731Artikel i tidskrift (Refereegranskat)
  • 48.
    Slapak, Rikard
    et al.
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Schillings, Audrey
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Nilsson, Hans
    Luleå tekniska universitet, Institutionen för system- och rymdteknik, Rymdteknik.
    Yamauchi, Masatoshi
    Swedish Institute of Space Physics, Kiruna.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Corrigendum to Atmospheric loss from the dayside open polar region and its dependence on geomagnetic activity: Implications for atmospheric escape on evolutionary time scales, published in Ann. Geophys., 35, 721–731,20172018Ingår i: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576Artikel i tidskrift (Refereegranskat)
  • 49.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    Modelling of Lubricating Grease FlowUsing Computational Fluid Dynamics2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    In this paper, numerical simulations of lubricating grease flow usingComputational Fluid Dynamics is presented. The grease is treated as asingle-phase Herschel-Bulkley fluid, where three different rheologicalproperties, corresponding to NLGI grade 00, 1 and 2, respectively, havebeen considered in two different configurations comprised by arestricted straight channel, and a double restriction seal with andwithout ring. The numerical code and rheology model have beenvalidated with analytical solutions and flow measurements using microparticleimage velocimetry. The grease velocity distribution in thegeometries are obtained and the motion of contaminant particlesinserted into the flow is investigated. The latter is of special interest inseal geometries which intend to protect the moving mechanicalcomponents from contamination.

  • 50.
    Westerberg, Lars-Göran
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Strömningslära och experimentell mekanik.
    MR-fluid Technology for Reduced Wear in Windturbine Bearings2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    Magnetorheology (MR) is a technology to enable active control of the viscosity of a material - typically afluid, but also semi-solid materials such as lubricating greases. Magnetic particles of nano to micron scale aremixed with the fluid and when subjected to a magnetic field the particles are aligned with the field, inducing ashear resistance - i.e. the effect of an increased viscosity - if applied in appropriate direction. This technology isfor example used in active dampers in sports cars, where electromagnets activated by a sensor systemcontrols the viscosity of the damper oil and the pressure in the dampers. This paper proposes a method ofusing MR technology to reduce wear in wind turbine bearings by enhancing the lubricant film in the maximumHertzian contact. Electromagnets are used to control the sequence of demagnetization and magnetization ofthe lubricant. Here the wear particles existing in the lubricant acts as guiding particles.

12 1 - 50 av 85
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