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Impeller

Distribution by Scientific Domains
Chemistry47%
Medical Sciences36%
Life Sciences8%
Engineering7%

Kinds of Impeller

  • reverse rotating impeller
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  • rotating impeller
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  • turbine impeller
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    Terms modified by Impeller

  • impeller speed
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    Selected Abstracts

    LDA Velocity Measurements of High-Viscosity Fluids in Mixing Vessel with Vane Geometry Impeller

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2007
    Lidija Slemenik Perse
    Abstract The object of this work was to measure the velocity field in non-Newtonian fluids inside mixing vessel. The six-bladed vane rotor used for mixing was designed from rotating vane geometry of a sensor system, commonly used for rheometrical measurements of complex fluids (Barnes and Nguyen, J. Non-Newtonian Fluid Mech. 98, 1-14 (2001); Schramm, 1994). During mixing, the viscosity was determined by measuring the torque at different impeller speeds, and compared to rheologically obtained shear dependent viscosity. The velocity field was determined by LDA measurements at twelve places inside mixing vessel. It was observed that axial and radial component of the velocity were insignificant at all measurement points. On the other hand, the results showed the periodic nature of tangential component of the velocity, which was confirmed with computer-aided visualization method. Ce travail avait pour objectif de mesurer le champ de vitesse dans des fluides non newtoniens dans un réservoir de mélange. Le rotor à six pales utilisé pour le mélange a été conçu d'après la géométrie des ailettes rotatives d'un système de senseurs, communément utilisés dans les mesures rhéométriques de fluides complexes (Barnes and Nguyen, J. Non-Newtonian Fluid Mech. 98, 1-14 (2001); Schramm, 1994). Lors du mélange, on a déterminé la viscosité en mesurant le couple à différentes vitesses de turbine, puis on l'a comparée à la viscosité de cisaillement obtenue rhéologiquement. Le champ de vitesse a été déterminé par des mesures LDA à douze positions dans le réservoir de mélange. On a observé que la composante axiale et radiale de la vitesse était négligeable pour tous les points de mesure. Par ailleurs, les résultats montrent la nature périodique de la composante tangentielle de la vitesse, ce qui est confirmé par une méthode de visualisation assistée par ordinateur. [source]

    Disposable MagLev Centrifugal Blood Pump Utilizing a Cone-Shaped Impeller

    ARTIFICIAL ORGANS, Issue 8 2010
    Wataru Hijikata
    Abstract To enhance the durability and reduce the blood trauma of a conventional blood pump with a cone-shaped impeller, a magnetically levitated (MagLev) technology has been applied to the BioPump BPX-80 (Medtronic Biomedicus, Inc., Minneapolis, MN, USA), whose impeller is supported by a mechanical bearing. The MagLev BioPump (MagLev BP), which we have developed, has a cone-shaped impeller, the same as that used in the BPX-80. The suspension and driving system, which is comprised of two degrees of freedom, radial-controlled magnetic bearing, and a simply structured magnetic coupling, eliminates any physical contact between the impeller and the housing. To reduce both oscillation of the impeller and current in the coils, the magnetic bearing system utilizes repetitive and zero-power compensators. In this article, we present the design of the MagLev mechanism, measure the levitational accuracy of the impeller and pressure-flow curves (head-quantity [HQ] characteristics), and describe in vitro experiments designed to measure hemolysis. For the flow-induced hemolysis of the initial design to be reduced, the blood damage index was estimated by using computational fluid dynamics (CFD) analysis. Stable rotation of the impeller in a prototype MagLev BP from 0 to 2750 rpm was obtained, yielding a flow rate of 5 L/min against a head pressure in excess of 250 mm Hg. Because the impeller of the prototype MagLev BP is levitated without contact, the normalized index of hemolysis was 10% less than the equivalent value with the BPX-80. The results of the CFD analysis showed that the shape of the outlet and the width of the fluid clearances have a large effect on blood damage. The prototype MagLev BP satisfied the required HQ characteristics (5 L/min, 250 mm Hg) for extracorporeal circulation support with stable levitation of the impeller and showed an acceptable level of hemolysis. The simulation results of the CFD analysis indicated the possibility of further reducing the blood damage of the prototype MagLev BP. [source]

    Improvement of Hemocompatibility in Centrifugal Blood Pump With Hydrodynamic Bearings and Semi-open Impeller: In Vitro Evaluation

    ARTIFICIAL ORGANS, Issue 10 2009
    Ryo Kosaka
    Abstract We have developed a noncontact-type centrifugal blood pump with hydrodynamic bearings and a semi-open impeller for mechanical circulatory assist. The impeller is levitated by an original spiral-groove thrust bearing and a herringbone-groove journal bearing, without any additional displacement-sensing module or additional complex control circuits. The pump was improved by optimizing the groove direction of the spiral-groove thrust bearing and the pull-up magnetic force between the rotor magnet and the stator coil against the impeller. To evaluate hemocompatibility, we conducted a levitation performance test and in vitro hemocompatibility tests by means of a mock-up circulation loop. In the hemolysis test, the normalized index of hemolysis was reduced from 0.721 to 0.0335 g/100 L corresponding to an expansion of the bearing gap from 1.1 to 56.1 µm. In the in vitro antithrombogenic test, blood pumps with a wide thrust bearing gap were effective in preventing thrombus formation. Through in vitro evaluation tests, we confirmed that hemocompatibility was improved by balancing the hydrodynamic fluid dynamics and magnetic forces. [source]

    New Centrifugal Blood Pump With Dual Impeller and Double Pivot Bearing System: Wear Evaluation in Bearing System, Performance Tests, and Preliminary Hemolysis Tests

    ARTIFICIAL ORGANS, Issue 4 2008
    Eduardo Bock
    Abstract:, A new dual impeller centrifugal blood pump has been developed as a research collaboration between Baylor College of Medicine and Institute Dante Pazzanese of Cardiology for long-term left ventricle assist device (LVAD). A design feature of this new pump is a dual impeller that aims to minimize a stagnant flow pattern around the inlet port. Several different materials were tested in order to adopt a double pivot bearing design originally developed by Prof. Dr. Yukihiko Nosé from Baylor College of Medicine. Hydraulic performance tests were conducted with two different inlet ports' angle configurations 30° and 45°. Pump with inlet port angle of 45° achieved best values of pressure ahead and flow after 1800 rpm. Preliminary hemolysis tests were conducted using human blood. The pump showed good performance results and no alarming trace of hemolysis, proving to be a feasible long-term LVAD. [source]

    CFD Simulation of Multicomponent Mixture of Ethanol and Glycerol in Stirred SBR with Anchor Type Impeller

    CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 8 2005
    L. Abu-Farah Dipl.-Ing.
    No abstract is available for this article. [source]

    Virtuelle Produktmodellierung am Beispiel eines Pumpenlaufrades

    CHEMIE-INGENIEUR-TECHNIK (CIT), Issue 1-2 2003
    F.-K. Benra Dr.-Ing.
    Abstract Durch die Verkürzung der Produktlebenszyklen werden die zur Verfügung stehenden Entwicklungszeiten entscheidend eingeschränkt. Es bleibt keine Zeit mehr für ein umfangreiches Erprobungsprogramm, bei dem die gewünschten Produkteigenschaften durch die Untersuchung und Abwandlung diverser Prototypen erzielt werden. Durch konsequenten Einsatz virtueller Techniken ist die Simulation der geforderten Produkteigenschaften und des Herstellungsprozesses möglich. Das Ergebnis einer so aufgebauten CAx-Prozesskette ist eine vollständige, durchgängig rechnerintegrierte Bauteilentwicklung. In diesem Beitrag wird ein derartiger Produktentstehungsprozess am Beispiel eines Kreiselpumpenlaufrades detailliert beschrieben. Durch die Schaffung eines Anwendungssystems für die Berechnung, Konstruktion und Fertigung von Pumpenlaufrädern lässt sich der Entwicklungsprozess enorm verkürzen. Gleichzeitig ist damit eine wesentliche Senkung der Entwicklungskosten für ein äußerst effektives und zuverlässiges Produkt verbunden. Virtual Modeling of Products with a Centrifugal Pump Impeller as an Example Shortening of the product life cycles means less time for the development of a technical product. There is no more time for an extensive testing program to obtain the desired product properties by investigation and modification of various prototypes. By careful application of virtual techniques the simulation of the required product properties and the production process is possible. The result of a CAx-System is a complete computer-integrated construction unit development. In this contribution the product developing process is described in detail for a centrifugal pump impeller. The creation of an application system for the computation, construction and manufacturing of pump impellers shortens the development process enormously. At the same time the development costs for an extremely effective and reliable product become substantially lower. [source]

    Development of an electrohydraulic total artificial heart system: Improvement of pump unit

    ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 9 2010
    Akihiko Homma
    Abstract An electrohydraulic total artificial heart (EHTAH) system has been developed. The EHTAH system consists of diaphragm-type blood pumps, and electrohydraulic actuator, an internal control unit, a transcutaneous energy transfer system (TETS), a transcutaneous optical telemetry system (TOTS), and an internal battery. The reciprocating rotation of the impeller generates oil pressure that drives the blood pumps at alternating intervals. The blood pumps and the actuator were successfully integrated into the pump unit without oil conduits. As a result of miniaturizing the blood pumps and the actuator, the displacement volume and weight of the EHTAH system were decreased to 872 ml and 2492 g, respectively. Furthermore, the maximum flow rate and efficiency increased up to 12 L/min and 15.4%. The pump units and the EHTAH systems were successfully implanted in 36 calves weighing from 55 to 87 kg. In the longest case, a calf with the pump unit survived for 87 days and a calf with the EHTAH system survived for 70 days. The EHTAH system was powered by the TETS, and was powered every day by the internal battery for 40 minutes. These results indicate that the EHTAH system has the potential to become a fully implantable cardiac replacement system. © 2010 Wiley Periodicals, Inc. Electron Comm Jpn, 93(9): 34,46, 2010; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.10220 [source]

    Comparison of velocity-log data collected using impeller and electromagnetic flowmeters

    GROUND WATER, Issue 3 2005
    M.W. Newhouse
    Previous studies have used flowmeters in environments that are within the expectations of their published ranges. Electromagnetic flowmeters have a published range from 0.1 to 79.0 m/min, and impeller flowmeters have a published range from 1.2 to 61.0 m/min. Velocity-log data collected in five long-screened production wells in the Pleasant Valley area of southern California showed that (1) electromagnetic flowmeter results were comparable within ±2% to results obtained using an impeller flowmeter for comparable depths; (2) the measured velocities from the electromagnetic flowmeter were up to 36% greater than the published maximum range; and (3) both data sets, collected without the use of centralizers or flow diverters, produced comparable and interpretable results. Although either method is acceptable for measuring wellbore velocities and the distribution of flow, the electromagnetic flowmeter enables collection of data over a now greater range of flows. In addition, changes in fluid temperature and fluid resistivity, collected as part of the electromagnetic flowmeter log, are useful in the identification of flow and hydrogeologic interpretation. [source]

    Process Considerations for Trolling Borehole Flow Logs

    GROUND WATER MONITORING & REMEDIATION, Issue 3 2006
    Phil L. Oberlander
    Horizontal hydraulic conductivity with depth is often understood only as a depth-integrated property based on pumping tests or estimated from geophysical logs and the lithology. A more explicit method exists for determining hydraulic conductivity over small vertical intervals by collecting borehole flow measurements while the well is being pumped. Borehole flow rates were collected from 15 deep monitoring wells on the Nevada Test Site and the Nevada Test and Training Range while continuously raising and lowering a high-precision impeller borehole flowmeter. Repeated logging passes at different logging speeds and pumping rates typically provided nine unique flow logs for each well. Over 60 km of borehole flow logs were collected at a 6.1-cm vertical resolution. Processing these data necessitated developing a methodology to delete anomalous values, smooth small-scale flow variations, combine multiple borehole flow logs, characterize measurement uncertainty, and determine the interval-specific lower limit to flow rate quantification. There are decision points in the data processing where judgment and ancillary analyses are needed to extract subtle hydrogeologic information. The analysis methodology indicates that processed measurements from a high-precision trolling impeller flowmeter in a screened well can confidently detect changes in borehole flow rate of ,0.7% of the combined trolling and borehole flow rate. An advantage of trolling the flowmeter is that the impeller is nearly always spinning as it is raised and lowered in the well and borehole flow rates can be measured at lower values than if measurements were taken while the flowmeter was held at a fixed depth. [source]

    Solid,liquid mass transfer characteristics of an unbaffled agitated vessel with an unsteadily forward,reverse rotating impeller

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2008
    Shuichi Tezura
    Abstract To develop an enhanced form of solid-liquid apparatus, an unbaffled agitated vessel has been constructed, fitted with an agitation system using an impeller whose rotation alternates unsteadily in direction, i.e. a forward-reverse rotating impeller. In this vessel, solid-liquid mass transfer was studied using a disc turbine impeller with six flat blades. The effect of impeller rotation rate as an operating variable on the mass transfer coefficient was evaluated experimentally using various geometrical conditions of the apparatus, such as impeller diameter and height, in relation to the impeller power consumption. Mixing of gas above the free surface into the bulk liquid, i.e. surface aeration, which accompanied the solid-liquid agitation, was also investigated. Comparison of the mass transfer characteristics between this type of vessel and a baffled vessel with a unidirectional rotating impeller underscored the sufficient solid-liquid contact for prevention of gas mixing in the forward-reverse rotation mode of the impeller. Copyright © 2008 Society of Chemical Industry [source]

    Agitation requirements for complete solid suspension in an unbaffled agitated vessel with an unsteadily forward,reverse rotating impeller

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 7 2007
    Shuichi Tezura
    Abstract Background: To develop a new type of solid,liquid apparatus, we have proposed the application of an agitation system with an impeller whose rotation alternates direction unsteadily, i.e., a forward,reverse rotating impeller. For an unbaffled agitated vessel fitted with this system, the suspension of solid particles in a liquid was studied using a disk turbine impeller with six flat blades. Results: The effects of the solid,liquid conditions and geometrical conditions of the apparatus on the minimum rotation rate and the corresponding impeller power consumption were evaluated experimentally for a completely suspended solid. The power consumption for a just suspended solid with this type of vessel was comparable with that for a baffled vessel with a unidirectionally rotating impeller, taking the liquid flow along the vessel bottom into consideration. Conclusion: Empirical relationships to predict the parameters of agitation requirements were found. A comparative investigation demonstrated the usefulness of the forward,reverse rotation mode of the impeller for off-bottom suspension of solid particles. Copyright © 2007 Society of Chemical Industry [source]

    Design and operation of unbaffled aerated agitated vessels with unsteadily forward,reverse rotating impellers handling viscous Newtonian liquids

    JOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 4 2003
    Masanori Yoshida
    Abstract Design and operation of unbaffled aerated agitated vessels with multiple unsteadily forward,reverse rotating impellers (AJITERs) for viscous Newtonian liquids were studied. The effects of operating conditions such as gas sparging rate, agitation rate and the number of impeller stages, geometrical conditions such as the diameters of vessel and impeller, and the physical properties of liquids on the drag and added moment of inertia coefficients, necessary to predict the average and maximum power consumptions of the impellers in AJITERs, were evaluated and the empirical relationships which estimate values of each of these coefficients are presented. The effects of operating conditions, geometrical conditions and liquid physical properties on the gas hold-up, ,gD, and volumetric oxygen transfer coefficient, kLaD, were evaluated in relation to the total power input which is the sum of the average power consumption of impellers, ie average agitation power input, and aeration power input. Empirical relationships, useful for design and operation of AJITERs, were obtained for each viscosity range, where the dependences of ,gD and kLaD on the specific total power input and superficial gas velocity differed, to predict ,gD and kLaD respectively as a function of the specific total power input, superficial gas velocity and liquid physical properties. © 2003 Society of Chemical Industry [source]

    Discrete element simulation of free flowing grains in a four-bladed mixer

    AICHE JOURNAL, Issue 8 2009
    Brenda Remy
    Abstract Numerical simulations of granular flow in a cylindrical vessel agitated by a four-blade impeller were performed using the discrete element method. Velocity, density, and stress profiles within the mixer displayed a periodic behavior with a fluctuation frequency equal to that of the blade rotation. Blade orientation was found to affect flow patterns and mixing kinetics. For an obtuse blade pitch orientation, a three-dimensional recirculation zone develops in-front of the blade due to formation of heaps where the blades are present. This flow pattern promotes vertical and radial mixing. No recirculation zone was observed when the blade orientation was changed to an acute blade pitch. The system's frictional characteristics are shown to strongly influence the granular behavior within the mixer. At low friction coefficients, the 3-D recirculation in front of the obtuse blade is not present reducing convective mixing. Higher friction coefficients lead to an increase in granular temperature which is associated with an increase in diffusive mixing. Normal and shear stresses were found to vary with mixer height with maximum values near the bottom plate. Additionally, a strong dependence between the magnitude of the shear stresses and the friction coefficient of the particles was found. The stress tensor characteristics indicate that the granular flow in our simulations occurs in the quasi-static regime. At the same time, the averaged pressure was found to vary linearly with bed height and could be predicted by a simple hydrostatic approximation. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Design of a high-efficiency hydrofoil through the use of computational fluid dynamics and multiobjective optimization

    AICHE JOURNAL, Issue 7 2009
    N. Spogis
    Abstract A computational fluid dynamics (CFD) model is proposed, based on ANSYS-CFX tools coupled to optimization models inside the commercial optimization software modeFRONTIER in order to obtain an optimal design of a high-efficiency impeller for solids suspension. The analysis of impeller shape performance was carried out using the shear-stress transport (SST) turbulence model with streamline curvature correction. This turbulence model combined the advantages of the ,,, and ,,, models, ensuring a proper relation between turbulent stress and turbulent kinetic energy, allowing an accurate and robust prediction of the impeller blade flow separation. The multiple frames of reference and the frozen rotor frame change models were used for the rotor/stator interaction inside the mixing vessel. The optimization procedure used seven design variables, two nonlinear constraints and two objective functions. The objective functions chosen (among many other possible options) to evaluate the impeller performance were the maximum solid distribution throughout the vessel (homogeneous suspension) reflected by a low variance between local solid concentration and average solid concentration inside the vessel and the higher pumping effectiveness, which was defined as the quotient of the flow and power numbers. The first objective function searches for impeller configurations able to provide good solid suspension, since it aims to achieve homogeneous suspension. The second objective function aims to reduce power consumption for a high-pumping capacity of the impeller. These criteria were considered enough to characterize the optimized impeller. Results indicated that the optimized impeller presented an increase of the pumping impeller capacity and homogeneous solid suspension with low-power consumption, especially when compared with the PBT 45° impeller. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source]

    Mixing of shear-thinning fluids with yield stress in stirred tanks

    AICHE JOURNAL, Issue 7 2006
    P. E. Arratia
    Abstract Mixing of shear-thinning fluids with yield stress is investigated in a three-dimensional (3-D) flow both in experiments and in simulations. Experiments are conducted in a stirred tank using tracer visualization and velocity measurements. Bulk flow visualization shows the familiar cavern formation around the impeller with stagnant zones surrounding it. Detailed flow visualization inside caverns reveals the main ingredients of chaotic flow: lobe formation, stretching, folding, and self-similar mixing patterns. For multiple impeller systems, however, we find strong compartmentalization characterized by robust segregation between adjacent caverns, hindering mixing performance. Mixing efficiency is enhanced by moving the shaft off-center, which breaks spatial symmetry. The displacement of the shaft from the tank centerline has a beneficial effect on manifold structure: segregated regions are destroyed, separatrices are eliminated, and axial circulation is improved. Numerical simulations are performed by solving the incompressible Reynolds Averaged Navier Stokes equation with a Galerkin Least-Squares finite-element formulation and a macroscopic rheological model. Simulations are able to capture the main features of the flow and are used to investigate stretching statistics and scale behavior. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source]

    Hydrodynamic investigation of USP dissolution test apparatus II

    JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 9 2007
    Ge Bai
    Abstract The USP Apparatus II is the device commonly used to conduct dissolution testing in the pharmaceutical industry. Despite its widespread use, dissolution testing remains susceptible to significant error and test failures, and limited information is available on the hydrodynamics of this apparatus. In this work, laser-Doppler velocimetry (LDV) and computational fluid dynamics (CFD) were used, respectively, to experimentally map and computationally predict the velocity distribution inside a standard USP Apparatus II under the typical operating conditions mandated by the dissolution test procedure. The flow in the apparatus is strongly dominated by the tangential component of the velocity. Secondary flows consist of an upper and lower recirculation loop in the vertical plane, above and below the impeller, respectively. A low recirculation zone was observed in the lower part of the hemispherical vessel bottom where the tablet dissolution process takes place. The radial and axial velocities in the region just below the impeller were found to be very small. This is the most critical region of the apparatus since the dissolving tablet will likely be at this location during the dissolution test. The velocities in this region change significantly over short distances along the vessel bottom. This implies that small variations in the location of the tablet on the vessel bottom caused by the randomness of the tablet descent through the liquid are likely to result in significantly different velocities and velocity gradients near the tablet. This is likely to introduce variability in the test. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96: 2327,2349, 2007 [source]

    The change in characteristics of microcrystalline cellulose during wet granulation using a high-shear mixer

    JOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2001
    Tatsuya Suzuki
    The objective of this study was to investigate the mechanism of hard granule formation and to demonstrate the applicability of X-ray diffraction methods for studying the polymeric pharmaceutical excipients. Using a high-shear mixer, microcrystalline cellulose (MCC) was granulated with water as the granulating liquid. The hardness of the MCC granules increased with granulation time and the amount of water added. The specific surface area measured by the N2 adsorption method was reduced during the process. Crystallite size of cellulose, calculated by Scherrer's equation adapted for wide angle X-ray diffraction method, decreased with granulation time and with increasing amounts of water added. Debye plots for X-ray small scattering patterns suggested that the average magnitude of the continuous solid region in MCC granules became significantly greater, whereas the specific surface area of the MCC granules, calculated from Debye plots, became smaller in comparison with that of intact MCC. These findings suggested that the long-chain structures in MCC were disrupted, resulting in smaller units with shorter chain lengths due to the strong shear force of the impeller. These smaller units then form a network within the granules. Thus, MCC granules are strengthened with longer granulation time and greater amounts of water, resulting in a more intricate network. The change in MCC chain length and physical structure can be experimentally detected using the small-angle X-ray scattering and wide-angle powder X-ray diffraction methods. [source]

    Effect of agitation intensity on the exo-biopolymer production and mycelial morphology in Cordyceps militaris

    LETTERS IN APPLIED MICROBIOLOGY, Issue 6 2002
    J.P. Park
    Aims:,The influence of agitation intensity on Cordyceps militaris morphology and exo-biopolymer production was investigated in a 5 litre stirred vessel using a six-blade Rushton turbine impeller. Methods and Results:,The mycelial morphology of C. militaris was characterized by means of image analysis, which included mean diameter, circularity, roughness and compactness of the pellets. The morphological parameters of the pellets grown under different stirring conditions were significantly different, which correspondingly altered exo-biopolymer production yields. Conclusions:,The compactness of the pellets was found to be the most critical parameter affecting exo-biopolymer biosynthesis; more compact pellets were formed at 150 rev min,1 with maximum exo-biopolymer production (15 g l,1). Significance and Impact of the Study:,The results of this study suggest that morphological change of pellets is a good indicator for identifying the cell activity for exo-biopolymer production. [source]

    The comparison of wear properties of different Fe-based hardfacing alloys in four kinds of testing methods

    LUBRICATION SCIENCE, Issue 4 2008
    E. Badisch
    Abstract Iron-based hardfacing alloys are widely used to protect machinery equipment. A strong correlation is given between microstructure and chemical composition of welding deposit with the resulting wear behaviour. Concerning precipitation of metallurgical hard phases and synthetic added hard particles, the bonding strength of the hard phases in the metallic matrix seems to play a dominating role to obtain high wear resistance. The main objective of this study was to evaluate the wear behaviour for pure abrasion, combined impact/abrasion and high impact wear, respectively, for four different Fe-based hardfacing alloys. Tests were performed with a standard ASTM G65 dry-sand/rubber-wheel tester. An impeller,tumbler apparatus enabled investigation of impact abrasion wear tests. Additional wear tests with high impact loading were performed on a drop hammer apparatus. Fracture surface analysis was carried out after drop hammer testing and results were correlated with microstructure and interfacial bonding behaviour of precipitations in metallic matrix. Copyright © 2008 John Wiley & Sons, Ltd. [source]

    A comparison of algebraic Reynolds stress models for the prediction of the turbulent flow inside a turbomachine rotor

    PROCEEDINGS IN APPLIED MATHEMATICS & MECHANICS, Issue 1 2003
    Marco Antonello Dr.
    An algebraic Reynolds stress model has been developed and tested simulating the turbulent flow inside a centrifugal impeller. The prediction of the model are compared with those of other algebraic turbulent stress models, in order to analyse the capability of properly account for effects such as flow curvature, flow separation, and solid wall rotation. [source]

    Charge generation during filling of insulated tanks

    PROCESS SAFETY PROGRESS, Issue 3 2002
    Migvia Vidal
    This research involves charge generation measurements for various flammable fluids during filling of insulated tanks and relating static charging with flow rate and physicochemical parameters, especially changes in electrical conductivity. The objective is to correlate static charge measured inside baffled metal and polyethylene tanks as a function of impeller, Reynolds number, and the electrical conductivity of both the hydrocarbon and the dispersed water phase for a variety of flammable liquids. A product of the research is a correlation for polyethylene and other plastic insulated tanks for transfers of low conductivity liquid fuels. Also, a universal (dimensionless) correlation that relates the charging data to the colloidal nature of the mixture will be developed for static charge generation during impeller mixing of light hydrocarbons containing various concentrations of water in cylindrical tanks. The correlation of electrostatic data from this research will help make it possible to control electrostatic charges, and, as a result, greatly improve safety of operations involving flammable fluids in industry. [source]

    Effect of impeller clearance on liquid flow within an unbaffled vessel agitated with a forward,reverse rotating impeller

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 6 2009
    Masanori Yoshida
    Abstract For an unbaffled agitated vessel with an unsteadily forward,reverse rotating impeller whose rotation proceeds with repeated acceleration, deceleration, and stop,reverse processes, liquid flow was studied through visualisation and measurement using particle tracking velocimetry (PTV). A disk turbine impeller with six flat blades was used with varied height settings. The impeller clearance and its forward,reverse rotation cycle characterised the impeller region flow: the radially outward flow in the deceleration process for the larger clearance relative to the vessel diameter of 1/3, and the axially downward flow in the acceleration process for the smaller clearance relative to the vessel diameter of 1/8. The flow patterns within the vessel resulting from the impeller's larger and smaller clearances were outlined, respectively, by double loops and a single loop of circulation, resembling the pattern produced by unidirectionally rotating turbine-type impellers. The discharge flow was revealed to contain a comparable level of periodic circumferential velocity component, irrespective of the impeller clearance. On a étudié l'écoulement liquide par visualisation et mesure en utilisant la vélocimétrie avec poursuite de trajectoire pour une cuve non compartimentée et agitée avec un agitateur rotatif avant-arrière non stable dont la rotation est composée de périodes répétées d'accélération, de ralentissement et d'arrêt-marche arrière. Un agitateur à six pales plates a été utilisé avec quatre réglages de hauteur différents. Le dégagement de l'agitateur et son cycle de rotation avant-arrière caractérisaient l'écoulement liquide dans la région de l'agitateur : l'écoulement radial vers l'extérieur dans le processus de décélération pour le dégagement le plus important par rapport au diamètre de la cuve de 1/3 et l'écoulement axial vers le bas dans le processus d'accélération pour le dégagement le plus petit par rapport au diamètre de la cuve de 1/8. Les modèles d'écoulement intérieurs de la cuve résultant du plus grand et du plus petit dégagements de l'agitateur ont été décrits, respectivement, par des doubles boucles et une simple boucle de circulation, ce qui ressemble au modèle produit par des agitateurs à hélice unidirectionnels. On a révélé que l'écoulement de sortie contenait un niveau comparable de vélocité périodique périphérique, indépendamment du dégagement de l'agitateur. [source]

    Mechanisms of solids drawdown in stirred tanks

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 4 2008
    Oscar Khazam
    Abstract Agitated tanks are used in several industrial processes to achieve complete drawdown of floating solids in liquids. The design requirements for this process are not completely defined, and are currently limited to heuristics regarding the use of a surface vortex and the effect of wettability on the difficulty of mixing, along with several initial studies in the literature. In this study, the effect of the type of impeller, particle size and shape, solids concentration, impeller submergence, and baffle configuration on the minimum drawdown speed (Njd) are investigated. It was found that the formation of a large surface vortex acts to hold particles close to the surface. Suppression of the surface vortex is recommended. In baffled tanks where the formation of a large surface vortex is suppressed, the intensity of turbulence and mean circulation velocity of the liquid are responsible for solids drawdown and distribution in the tank. The submergence of the impeller relative to the liquid surface and the pumping mode of the pitched blade turbine (PBT) were found to be the controlling parameters. CFD simulations were carried out to obtain a better understanding and interpretation of the flow patterns and drawdown mechanisms for the different baffle configurations. Les réservoirs agités servent dans plusieurs procédés industriels pour réaliser l'immersion complète des solides flottant sur les liquides. Les besoins de conception pour ce procédé ne sont pas complètement définis et sont actuellement limités à une approche heuristique utilisant un vortex de surface et à l'effet de la mouillabilité sur la difficulté de mélange, en complément de plusieurs études initiales dans la littérature scientifique. Dans cette étude, l'effet du type de turbine, de la taille et de la forme des particules, de la concentration de solides, de la submersion de la turbine et de la configuration des chicanes sur la vitesse d'immersion (Njd) est étudié. On a trouvé que la formation d'un vortex de surface important a pour effet de garder les particules proches de la surface. La suppression du vortex de surface est recommandée. Dans les réservoirs munis de chicanes où la formation du vortex de surface important est supprimée, l'intensité de la turbulence et la vitesse de circulation moyenne du liquide sont responsables de l'immersion des solides et de leur distribution dans le réservoir. On a trouvé que la hauteur d'immersion de la turbine par rapport à la surface du liquide et le mode de pompage de la turbine à pales inclinées (PBT) étaient les paramètres gouvernants. Des simulations en CFD ont été menées pour une meilleure compréhension et interprétation des profils d'écoulement et des mécanismes d'immersion pour différentes configurations de chicanes. [source]

    Scalar mixing measurements in a continuously operated stirred tank

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2001
    Markus F. W. Distelhoff
    Abstract An LIF (Laser induced flourescence) line scan system was used to obtain unobtrusive scalar concentration measurements in a continuously operated stirred tank agitated by a radial flow Rushton turbine and an axial flow 60°-pitched blade impeller. A better blending process was generally achieved in the axial flow field, with macro- and micromixing in the radial flow field being most complete with fluid injected into the radial discharge jet, and in the axial flow field with fluid injected from above into the rotating impeller. Local concentration levels and fluctuations scaled with the feed pipe flow rate, and the degree of concentration uniformity throughout the tank scaled with the impeller speed and increased with the cube of the power input. On a utilisé un scanneur LIF (fluorescence induite par laser) afin d'obtenir des mesures non invasives de concentration scalaire dans un réservoir agité par une turbine Rushton à écoulement radial et une turbine à pales inclinées à 60° à écoulement axial fonctionnant en continu. On obtient généralement un meilleur procédé de mélange dans le champ d'écoulement axial, le macro et micro-mélange dans le champ d'écoulement radial étant plus complet lorsque le fluide est injecté dans la zone de refoulement radial, et dans le champ d'écoulement axial lorsque le fluide est injecté au-dessus de la turbine. Les niveaux de concentration locaux et les fluctuations sont corrélés au débit de la conduite d'alimentation, et le degré d'uniformité des concentrations dans le réservoir est fonction de la vitesse de la turbine et augmente avec le cube de l'apport de puissance. [source]

    Estimation of gas hold-up in aerated vessels

    THE CANADIAN JOURNAL OF CHEMICAL ENGINEERING, Issue 2 2000
    Alessandro Paglianti
    Abstract An attempt to produce a simple equation for gas hold-up in stirred tank reactors has been made. This new semi-empirical equation, based on the mass balance for the gas phase, predicts the observed effem due to the tank and impeller diameters and physical properties reasonably well. It can be used both for tanks working with a single Rushton impeller as well as with multiple Rushton impeller systems. The equation has been validated using both data found in literature and from our experiments. On a tenté de produire une équation simple pour la rétention de gaz dans des réacteurs à réservoir agité. Cette nouvelle équation semi-empirique, reposant sur le bilan massique de la phase gazeuse, prédit raisonnablement bien les effets observés dus aux diamètres et aux propriétés physiques du réservoir et de la turbine. Celle-ci peut çtre utilisée aussi bien pour les réservoirs munis d'une turbine Rushton unique que pour des systèmes munis de plusieurs turbines Rushton. L'équation a été validée à l'aide de données provenant de la littérature scientifique ainsi que de nos expériences. [source]

    Evaluation of the Impeller Shroud Performance of an Axial Flow Ventricular Assist Device Using Computational Fluid Dynamics

    ARTIFICIAL ORGANS, Issue 9 2010
    Boyang Su
    Abstract Generally, there are two types of impeller design used in the axial flow blood pumps. For the first type, which can be found in most of the axial flow blood pumps, the magnet is embedded inside the impeller hub or blades. For the second type, the magnet is embedded inside the cylindrical impeller shroud, and this design has not only increased the rotating stability of the impeller but has also avoided the flow interaction between the impeller blade tip and the pump casing. Although the axial flow blood pumps with either impeller design have been studied individually, the comparisons between these two designs have not been conducted in the literature. Therefore, in this study, two axial flow blood pumps with and without impeller shrouds were numerically simulated with computational fluid dynamics and compared with each other in terms of hydraulic and hematologic performances. For the ease of comparison, these two models have the same inner components, which include a three-blade straightener, a two-blade impeller, and a three-blade diffuser. The simulation results showed that the model with impeller shroud had a lower static pressure head with a lower hydraulic efficiency than its counterpart. It was also found that the blood had a high possibility to deposit on the impeller shroud inner surface, which greatly enhanced the possibility of thrombus formation. The blood damage indices in both models were around 1%, which was much lower than the 13.1% of the axial flow blood pump of Yano et al. with the corresponding experimental hemolysis of 0.033 g/100 L. [source]

    Disposable MagLev Centrifugal Blood Pump Utilizing a Cone-Shaped Impeller

    ARTIFICIAL ORGANS, Issue 8 2010
    Wataru Hijikata
    Abstract To enhance the durability and reduce the blood trauma of a conventional blood pump with a cone-shaped impeller, a magnetically levitated (MagLev) technology has been applied to the BioPump BPX-80 (Medtronic Biomedicus, Inc., Minneapolis, MN, USA), whose impeller is supported by a mechanical bearing. The MagLev BioPump (MagLev BP), which we have developed, has a cone-shaped impeller, the same as that used in the BPX-80. The suspension and driving system, which is comprised of two degrees of freedom, radial-controlled magnetic bearing, and a simply structured magnetic coupling, eliminates any physical contact between the impeller and the housing. To reduce both oscillation of the impeller and current in the coils, the magnetic bearing system utilizes repetitive and zero-power compensators. In this article, we present the design of the MagLev mechanism, measure the levitational accuracy of the impeller and pressure-flow curves (head-quantity [HQ] characteristics), and describe in vitro experiments designed to measure hemolysis. For the flow-induced hemolysis of the initial design to be reduced, the blood damage index was estimated by using computational fluid dynamics (CFD) analysis. Stable rotation of the impeller in a prototype MagLev BP from 0 to 2750 rpm was obtained, yielding a flow rate of 5 L/min against a head pressure in excess of 250 mm Hg. Because the impeller of the prototype MagLev BP is levitated without contact, the normalized index of hemolysis was 10% less than the equivalent value with the BPX-80. The results of the CFD analysis showed that the shape of the outlet and the width of the fluid clearances have a large effect on blood damage. The prototype MagLev BP satisfied the required HQ characteristics (5 L/min, 250 mm Hg) for extracorporeal circulation support with stable levitation of the impeller and showed an acceptable level of hemolysis. The simulation results of the CFD analysis indicated the possibility of further reducing the blood damage of the prototype MagLev BP. [source]

    Shape Optimization of the Diffuser Blade of an Axial Blood Pump by Computational Fluid Dynamics

    ARTIFICIAL ORGANS, Issue 3 2010
    Lailai Zhu
    Abstract Computational fluid dynamics (CFD) has been a viable and effective way to predict hydraulic performance, flow field, and shear stress distribution within a blood pump. We developed an axial blood pump with CFD and carried out a CFD-based shape optimization of the diffuser blade to enhance pressure output and diminish backflow in the impeller,diffuser connecting region at a fixed design point. Our optimization combined a computer-aided design package, a mesh generator, and a CFD solver in an automation environment with process integration and optimization software. A genetic optimization algorithm was employed to find the pareto-optimal designs from which we could make trade-off decisions. Finally, a set of representative designs was analyzed and compared on the basis of the energy equation. The role of the inlet angle of the diffuser blade was analyzed, accompanied by its relationship with pressure output and backflow in the impeller,diffuser connecting region. [source]

    Numerical Study of a Bio-Centrifugal Blood Pump With Straight Impeller Blade Profiles

    ARTIFICIAL ORGANS, Issue 2 2010
    Guoliang Song
    Abstract Computational fluid dynamic simulations of the flow in the Kyoto-NTN (Kyoto University, Kyoto, Japan) magnetically suspended centrifugal blood pump with a 16-straight-bladed impeller were performed in the present study. The flow in the pump was assumed as unsteady and turbulent, and blood was treated as a Newtonian fluid. At the impeller rotating speed of 2000 rpm and flow rate of 5 L/min, the pump produces a pressure head of 113.5 mm Hg according to the simulation. It was found that the double volute of the pump has caused symmetrical pressure distribution in the volute passages and subsequently caused symmetrical flow patterns in the blade channels. Due to the tangentially increasing pressure in the volute passages, the flow through the blade channels initially increases at the low-pressure region and then decreases due to the increased pressure. The reverse flow and vortices have been identified in the impeller blade channels. The high shear stress of the flow in the pump mainly occurred at the inlet and outlet of the blade channels, the beginning of the volute passages and the regions around the tips of the cutwater and splitter plate. Higher shear stress is obtained when the tips of the cutwater and splitter plate are located at the impeller blade trailing edges than when they are located at the middle of the impeller blade channel. It was found that the blood damage index assessed based on the blood corpuscle path tracing of the present pump was about 0.94%, which has the same order of magnitude as those of the clinical centrifugal pumps reported in the literature. [source]

    Intravascular Mechanical Cavopulmonary Assistance for Patients With Failing Fontan Physiology

    ARTIFICIAL ORGANS, Issue 11 2009
    Sonya S. Bhavsar
    Abstract To provide a viable bridge-to-transplant, bridge-to-recovery, or bridge-to-surgical reconstruction for patients with failing Fontan physiology, we are developing a collapsible, percutaneously inserted, magnetically levitated axial flow blood pump to support the cavopulmonary circulation in adolescent and adult patients. This unique blood pump will augment pressure and thus flow in the inferior vena cava through the lungs and ameliorate the poor hemodynamics associated with the univentricular circulation. Computational fluid dynamics analyses were performed to create the design of the impeller, the protective cage of filaments, and the set of diffuser blades for our axial flow blood pump. These analyses included the generation of pressure,flow characteristics, scalar stress estimations, and blood damage indexes. A quasi-steady analysis of the diffuser rotation was also completed and indicated an optimal diffuser rotational orientation of approximately 12°. The numerical predictions of the pump performance demonstrated a pressure generation of 2,25 mm Hg for 1,7 L/min over 3000,8000 rpm. Scalar stress values were less than 200 Pa, and fluid residence times were found to be within acceptable ranges being less than 0.25 s. The maximum blood damage index was calculated to be 0.068%. These results support the continued design and development of this cavopulmonary assist device, building upon previous numerical work and experimental prototype testing. [source]