Showing papers on "Impeller published in 2004"

Quiet vertical takeoff and landing aircraft using ducted, magnetic induction air-impeller rotors

Abstract: A hover aircraft employs an air impeller engine having an air channel duct and a rotor with outer ends of its blades fixed to an annular impeller disk that is driven by magnetic induction elements arrayed in the air channel duct. The air-impeller engine is arranged vertically in the aircraft frame to provide vertical thrust for vertical takeoff and landing. Preferably, the air-impeller engine employs dual, coaxial, contra-rotating rotors for increased thrust and gyroscopic stability. An air vane assembly directs a portion of the air thrust output at a desired angle to provide a horizontal thrust component for flight maneuvering or translation movement. The aircraft can employ a single engine in an annular fuselage, two engines on a longitudinal fuselage chassis, three engines in a triangular arrangement for forward flight stability, or other multiple engine arrangements in a symmetric, balanced configuration. Other flight control mechanisms may be employed, including side winglets, an overhead wing, and/or air rudders or flaps. An integrated flight control system can be used to operate the various flight control mechanisms. Electric power is supplied to the magnetic induction drives by high-capacity lightweight batteries or fuel cells. The hover aircraft is especially well suited for applications requiring VTOL deployment, hover operation for quiet surveillance, maneuvering in close air spaces, and long duration flights for continuous surveillance of ground targets and important facilities requiring constant monitoring.

Numerical Study of Unsteady Flow in a Centrifugal Pump

Abstract: Computational Fluid Dynamics analysis has been used to solve the unsteady three-dimensional viscous flow in the entire impeller and volute casing of a centrifugal pump. The results of the calculations are used to predict the impeller/volute interaction and to obtain the unsteady pressure distribution in the impeller and volute casing. The calculated unsteady pressure distribution is used to determine the unsteady blade loading. The calculations at the design point and at two off-design points are carried out with a multiple frame of reference and a sliding mesh technique is applied to consider the impeller/volute interaction. The results obtained show that the flow in the impeller and volute casing is periodically unsteady and confirm the circumferential distortion of the pressure distribution at the impeller outlet and in the volute casing. Due to the interaction between impeller blades and the tongue of the volute casing the flow is characterized by pressure fluctuations, which are strong at the impeller outlet and in the vicinity of the tongue. These pressure fluctuations are died away in the casing as the advancement angle increases. These reduced pressure fluctuations are spread to the discharge nozzle; the pressure fluctuations are also reflected to the impeller inlet and they affect the mass flow rate through the blade passages.Copyright © 2004 by ASME

Numerical Simulation of Turbulent Flow Characteristics in a Stirred Vessel Using the LES and RANS Approaches with the Sliding/Deforming Mesh Methodology

Abstract: Numerical predictions using the large eddy simulation (LES) and RANS methods have been performed on a mixing vessel stirred by a Rushton impeller at Re = 40,000. The finite volume method in an unstructured mesh consisting of around 490,000 computational cells was used. For the LES method, the subgrid-scale effects were modelled using the standard Smagorinsky model, while for the RANS method the standard k-ɛ model was used. The interaction between the rotating impeller and the static baffles was accounted for using the sliding–deforming mesh methodology. Comparisons were made between the predictions and previously reported phase-resolved LDA measurements of mean and rms velocities, as well as turbulent kinetic energy. The results obtained with the LES approach capture well both the overall as well as the detailed flow features (such as the trailing vortices) and show very substantial improvement in comparison to RANS predictions with the standard k-ɛ model. The global turbulent energy dissipation rate ( ɛ ) across the vessel volume was also well predicted by the LES, to within 15% of the measured value; in contrast, ɛ was underpredicted by 45% with the RANS model. The local values of ɛ in the impeller stream also compare well with measured values.

Wide blade, axial flow pump

Abstract: A blood pump comprises a pump housing; a rotor positioned in the housing and comprising an impeller having a hydrodynamic surface for pumping blood; and a motor including a plurality of magnets carried by the impeller, plus a rotor stator, including an electrically conductive coil located adjacent to or within the housing. The impeller comprises radially outwardly extending, bladelike projections that define generally longitudinally extending spaces between the projections. The shape of the projections and the spaces therebetween tend to drive blood in the spaces in an axial direction as the impeller is rotated. The spaces collectively have a total width along most of their lengths at the radial periphery of the rotor, that is substantially equal to or less than the collective width of the projections along most of their lengths at the radial periphery. Thus, the bladelike projections are thicker, achieving significant advantages.

Performance of a centrifugal pump running in inverse mode

Abstract: This paper presents the functional characterization of a centrifugal pump used as a turbine. It shows the characteristics of the machine involved at several rotational speeds, comparing the respective flows and heads. In this way, it is possible to observe the influence of the rotational speed on efficiency, as well as obtaining the characteristics at constant head and runaway speed. Also, the forces actuating on the impeller were studied. An uncertainty analysis was made to assess the accuracy of the results. The research results indicate that the turbine characteristics can be predicted to some extent from the pump characteristics, that water flows out of the runner free of swirl flow at the best efficiency point, and that radial stresses are lower than in pump mode.

Flow in an impeller‐stirred tank using an immersed‐boundary method

Abstract: The moderate Reynolds number flow developing in a cylindrical unbaffled stirred tank is studied using direct numerical simulation (DNS) and the results are compared with available experimental data and Reynolds Averaged Navier–Stokes (RANS) solutions. The geometry of the impeller is handled using an immersed-boundary procedure implemented in a solver written for cylindrical coordinates. This allows efficient simulation of the flow at a reasonable computational cost and accurate prediction of the mean and rms velocity fields. For this configuration, RANS performs poorly because of the low Reynolds and strongly unsteady and inhomogeneous nature of the flow: many different flow structures are produced, ranging from small-scale vortices generated at the blade tips to large-scale meridional recirculation. It is shown, in addition, that inaccurate results are produced by the wrong (computational) assumption that an impeller with n blades produces instantaneous fields with an n-fold symmetry. Because simple stirred-tank configurations (like the present one) have been recently used to assess the performance of several RANS closures, the main message of this study is that simple geometrical configurations and low Reynolds numbers are not benign parameters for such a task. © 2004 American Institute of Chemical Engineers AIChE J, 50: 1109–1118, 2004

Residence Time Distributions in a Stirred Tank: Comparison of CFD Predictions with Experiment

Abstract: Residence time distributions (RTD) are measured for both a baffled and an unbaffled laboratory reactor of the same size with several internal pipes and a Rushton turbine operating at different feed flow rates and impeller rpms. Ideal behavior as determined by the mean and the variance of the RTD was observed at an impeller Reynolds number of 2327 for the baffled tank and 3878 for the unbaffled tank both in the turbulent transition range. The experimental results for the baffled tank are compared to computational fluid dynamics (CFD) predictions of the RTD using the k−e turbulence model in Fluent for transitional flow regime in the tank, i.e., impeller Reynolds number between 10 and 10 000. All the qualitative aspects of the predicted RTDs are similar to those measured experimentally. The mean residence times as well as the variances of the residence time are accurately predicted by CFD in the transition flow regime.

A five-axis rough machining approach for a centrifugal impeller

Abstract: A clear trend shows that most products or mechanical components, especially those regarding aerospace applications, are designed to fit the requirements of free form surface features. When a 3-axis computer numerical controlled (CNC) machining centre is used to produce a typical centrifugal impeller, great difficulties, i.e., collisions between the cutting tool and impeller, need to be overcome. In this case, sophisticated five-axis machines have to be utilised. Presently, most commercial computer-aided manufacturing (CAM) systems for five-axis control are lacking generality, and functions for the rough tool-path generation are far less than required. The rough machining is recognised as the most important procedure influencing the machining efficiency and is critical for the success of the following finishing process. However, great difficulties are expected to arise in performing five-axis rough machining. The main objective of the present study is to overcome this problem by combining related machining technology. As a result, CL data based on the geometry model of blade and hub of the impeller are generated. Finally, the CL data is confirmed through software simulation. The results of verification prove the machining methodology and procedure to be successful.

Streamlined unobstructed one-pass axial-flow pump

Abstract: A blood pump has an impeller rotatably disposed and magnetically suspended within a cavity of a stator by a plurality of magnetic bearings (passive permanent and active electromagnetic) having impeller magnets on the impeller and stator magnets or coils/poles on the stator. A motor includes impeller magnets on the impeller and coils/poles associated with the stator. A single, annular blood flow path extends axially through the cavity between the impeller and the stator, and between the impeller magnets on the impeller and the stator magnets or the coils/poles on the stator.

Axial-flow blood pump with magnetically suspended, radially and axially stabilized impeller

Abstract: A blood pump has an impeller rotatably disposed and magnetically suspended within a cavity of a stator by a plurality of magnetic bearings including an axial bearing to support the impeller axially in the cavity. The axial bearing includes adjacent impeller magnets and adjacent stator magnets with axially aligned polarities and reverse polarities with respect to adjacent magnets. A motor includes impeller magnets on the impeller and coils and poles associated with the stator. Radial permanent magnet and electromagnetic bearings are also included. The magnetic bearings and the motor have stator magnets or coils and poles disposed radially across the fluid passage from corresponding impeller magnets to define an annular gap positioned radially between the impeller and the stator, and positioned radially between all of the plurality of magnetic bearings, creating a straight through blood path without secondary flow paths.

Rotor and bearing system for a turbomachine

Abstract: A rotor and bearing system for a turbomachine. The turbomachine (10) includes a drive shaft (20), an impeller (36) positioned on the drive shaft, and a turbine (34) positioned on the drive shaft proximate to the impeller. The bearing system (44) comprises one gas journal bearing (46) supporting the drive shaft between the impeller and the turbine. The area between the impeller and the turbine is an area of increased heat along the drive shaft in comparison to other locations along the drive shaft. The section of the drive shaft positioned between impeller and the turbine is also a section of the drive shaft that experiences increased stressed and load in the turbomachine. The inventive bearing machine system positions only one radial bearing in this area of increased stress and load.

Porous pressure-sensitive paint for measurement of unsteady pressures in turbomachinery

Abstract: This work details the development and application of porous pressure-sensitive paint (PSP) for measuring unsteady surface pressures in turbomachinery. The advantages of porous PSP over conventional methods include global pressure measurement, fast response time, and instrumentation of thin turbomachinery components that are otherwise difficult or impossible to instrument. In this paper, the development, calibration, and application of porous PSP to turbomachinery are discussed. Porous PSP formulations were developed to ensure fast response times and good adhesion characteristics to rotating parts. Experimental methods such as phase-locking and image registration were developed to acquire quality data. Dynamic response calibrations of PSP with a fluidic oscillator were performed, indicating that porous PSP formulations have a response time of up to 40 kHz. For a turbomachinery application, the inlet wall and impeller blades of a turbocharger compressor were painted with fast-responding polymer/ceramic PSP. The turbocharger was operated at 100,000 rpm, corresponding to a blade-passage frequency (BPF) of 10 kHz. Even at this high speed and BPF, porous PSP was able to resolve the unsteady wall pressure distributions about the blade. In addition, a flow blockage was created to induce an inlet flow distortion on the compressor. Porous PSP was able to resolve the 1.67 kHz unsteady blade loading. Potential applications of porous PSP to unsteady turbomachinery testing include evaluations of rotor/stator interaction, flutter, inlet flow distortion, rotating stall, and surge.

A Study of Impeller-Diffuser-Volute Interaction in a Centrifugal Fan

Abstract: This paper reports velocity measurement data in the interaction region between the impeller and vaned diffuser and the results of numerical flow simulation of the whole machine (impeller vaned diffuser and volute) of a single stage centrifugal fan. Two-dimensional instantaneous velocity measurement is done using particle image velocimetry (PIV). Numerical simulation of impeller-diffuser-volute interaction is performed using CFX-Tascflow commercial code. A frozen rotor simulation model is used for the steady calculation and a rotor-stator simulation model is used for the unsteady calculation using the steady results as an initial guess. The simulation results show that the separated flow regime near the diffuser hub extends to the volute. Comparison between the unsteady computation and those of measurement indicates that the rotor/stator model employed in the simulation predicts essential characteristics of unsteady flow in the centrifugal fan. However, quantitative agreement remains rather poor.

Reynolds Number and Impeller Diameter Effects on Instabilities in Stirred Vessels

Abstract: Flow instability phenomena in stirred vessels were studied with laser anemometry and flow visualization. The effects of fluid density and viscosity, impeller Reynolds number (Re), impeller design, diameter, and off-bottom clearance were investigated in order to quantify the frequencies (f) of the macroinstabilities stemming from precessional motions. The instabilities are characterized by two frequencies, one present at low Re, and another at high Re values. For intermediate Re values, both frequencies were present. In all cases, f was proportional to the impeller speed (N). The parameter f′ = f/N was shown to be linearly related to the impeller diameter in the low Re range; f′ was not affected by impeller clearance. At constant Re, a change in fluid density and viscosity did not affect f′. The energy contained in the instability frequencies was shown to vary across the vessel. The implications of the results mixing practice are discussed. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2050–2063, 2004

Modelling of Turbulence in Stirred Vessels Using Large Eddy Simulation

Abstract: The application of large eddy simulation (LES) to the prediction of large-scale chaotic structures in stirred tanks is investigated. Typical stirrer configurations representing different flow regimes are assessed: a single radial pumping impeller, single axial pumping impellers, multiple hydrofoil impellers, and a retreat curve impeller. The dynamic turbulent flow field in each configuration is calculated using LES. The impeller motion is explicitly modelled using the sliding mesh model. It is concluded that the flow fields in stirred vessels are very rich in structure and that a wide variety of flow regimes exist. The predicted flow patterns compare well with digital particle image velocimetry data reported in the literature, and exhibit the long time-scale instabilities seen in experiments reported in the literature.

Manual or pump assist fluid dispenser

Abstract: A chamber about an opening of an inverted container with an impeller within the chamber which, on rotation, dispenses fluid from the chamber.

CFD Analysis of Electric Submersible Pumps (ESP) Handling Two-Phase Mixtures

Abstract: The behavior of electric submersible pumps (ESP) handling two-phase flow is a subject of primary concern, especially in the petroleum industry, where significant amounts of free gas may be found in oil wells production. In the past, several attempts were made to predict the performance of such kind of pumps, nevertheless, limited success has been achieved due to the complex flow dynamics inside the impeller Geometry, gas void fraction (GVF) and suction pressure seem to be the main parameters affecting ESP performance. Furthermore, the higher the GVF of the mixture is, the higher the degradation of head that is experienced by the pump. So far, this complex phenomenon has not been well understood. In the present work, a two fluid model is used in three-dimensional (3D) CFD simulations to obtain the pressure, liquid and gas velocity fields as well as the GVF distribution inside an ESP impeller of known geometry; using flow rates, bubble diameter and GVF at the suction as independent variables and an incompressible fluid hypothesis. The gas pocket in the impeller blade reported by other researchers is obtained and comparison with experimental results shows good agreement. The obtained variables from the simulations are the cornerstone that allows the prediction of the performance curve of the pump for different GVF and such, lets the head degradation of the pump be estimated.

Coaxial Mixer Hydrodynamics with Newtonian and non-Newtonian Fluids

Abstract: The performance of several combinations of a wall scraping impeller and dispersing impellers in a coaxial mixer operated in counter- and co-rotating mode were assessed with Newtonian and non-Newtonian fluids. Using the power consumption and the mixing time as the efficiency criteria, impellers in co-rotating mode were found to be a better choice for Newtonian and non-Newtonian fluids. The hybrid impeller-anchor combination was found to be the most efficient for mixing in counter-rotating or co-rotating mode regardless of the fluid rheology. For both rotating modes, it was shown that the anchor speed does not have any effect on the power draw of the dispersing turbines. However, the impeller speed was shown to affect the anchor power consumption. The determination of the minimum agitation conditions to achieve the just suspended state of solid particles (N js ) was also determined. It was found that N js had lower values with the impellers having the best axial pumping capabilities.

Shape optimization of forward-curved-blade centrifugal fan with Navier-Stokes analysis

Abstract: The response surface method using a three-dimensional Navier-Stokes analysis to optimize the shape of forward-curved-blade centrifugal fan is described. For the numerical analysis, Reynolds-averaged Navier-Stokes equations with the standard κ-e turbulence model are discretized with finite volume approximations. The SIMPLEC algorithm is used as a velocity-pressure correction procedure. In order to reduce the huge computing time due to a large number of blades in forward-curved-blade centrifugal fan, the flow inside of the fan is regarded as steady flow by introducing the impeller force models. Four design variables, i.e., location of cutoff, radius of cutoff, expansion angle of scroll, and width of impeller were selected to optimize the shapes of scroll and blades. Data points for response evaluations were selected by D-optimal design, and a linear programming method was used for the optimization on the response surface

Mixing of complex fluids with flat-bladed impellers: effect of impeller geometry and highly shear-thinning behavior

Abstract: Mixing of rheological complex fluids was investigated using flat-bladed impellers as close-clearance agitators in the laminar regime. Two Newtonian and six highly shear-thinning fluids were used. The non-Newtonian fluids were adequately described by a power-law model with a flow index n between 0.1 and 0.4. Power draw analysis was used to explore the combined influence of pseudoplasticity and impeller geometry. Geometry was studied first by varying the column-to-impeller diameter ratio, and then by combining several similar mixing elements on the same shaft. For pseudoplastic fluid, the Rieger–Novak and the power curve methods as well as an original Couette analogy were used for estimating the effective shear rate and the proportionality constant K S . A good agreement was obtained between these three methods. K S was shown to be nearly independent of n : the Metzner–Otto assumption was shown to be valid for all the geometries studied. A generalized dimensionless power draw curve which took pseudoplasticity into account was obtained by shifting the non-Newtonian results to the Newtonian curve. The effectiveness of flat-bladed impellers for dispersive mixing in complex fluids proved in previous works was explained by the fact that the effective shear rate remained high even when power consumption dramatically decreased with n .

Computational Fluid Dynamics (CFD) study of the 4th generation prototype of a continuous flow Ventricular Assist Device (VAD).

Abstract: The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.

Pump without rotational shaft

Abstract: PURPOSE: A pump without a rotation shaft is provided to achieve a function of a submersible pump by installing an impeller in a fluid reservoir and positioning a pump body at an outer portion of the fluid reservoir. CONSTITUTION: A pump includes an electromagnetic force generating unit(2) generating electromagnetic force. An impeller(1) is positioned in an area subject to the electromagnetic force of the electromagnetic force generating unit(2) in such a manner that the impeller(1) is operated by means of the electromagnetic force of the electromagnetic force generating unit(2). As the impeller(1) is operated, fluid is introduced into the pump through an intake hole formed in a case(5). Fluid introduced into the pump is exhausted out of the pump through an exhaust port(4) formed in the pump.

Inverse Design Method for Centrifugal Impellers and Comparison with Numerical Simulation Tools

Abstract: A process that enables us to improve the design of 2D centrifugal and helico-centrifugal pumps is presented. First of all, the definition of the impeller geometry as well as the analysis of its global performances are carried out starting from the mean streamline method (1D), based at the same time on ideal models and experimental correlations. A second stage of optimisation is achieved from a quasi three-dimensional (Q3D) method, by studying the meridional flow and blade-to-blade flow. Finally, 3D flow solution is performed by CFD tools. Nowadays, we have a group of tools which help the designers improve the performance of new machines. These digital tools are built around two computer programs, HELIOX developed for design and performance analysis in any centrifugal and mixed flow pumps equipped with volute or deswirl vanes, and also the module REMIX that gathers the meridional flow analysis and the simplified blade-to-blade one. To validate this procedure, a centrifugal machine with a volute (NS32) was ...

Large Eddy Simulation of Turbulent Flow in a Rushton Impeller Stirred Reactor with Sliding-Deforming Mesh Methodology

Abstract: The unsteady turbulent flow in a mixing vessel stirred by a Rushton impeller is predicted using the Large Eddy Simulation technique. The interaction between the moving impeller and the static baffles is accounted for explicitly through a sliding-deforming mesh methodology, thus, eliminating approximations used to account for the effect of the moving impeller. Large-scale structures associated with the trailing vortices are assessed via the vorticity and the turbulent kinetic energy distributions. The phase-resolved predictions are compared with measurement data obtained by laser-Doppler anemometry and favourable agreement is reported both for mean as well as turbulence quantities.