Showing papers on "Impeller published in 1999"

Large eddy simulations on the flow driven by a Rushton turbine

Abstract: Large eddy simulations were performed on the flow in a baffled stirred tank, drien by a Rushton turbine at Res 29,000. The simulation procedure consisted of a lattice ) Boltzmann scheme for discretizing the Naier ) Stokes equations, and a force- field technique for representing the action of the impeller on the fluid. The subgrid-scale model was a conentional Smagorinsky model with a Smagorinsky constant c s 0.12. s The uniform, cubic computational grid had a size of about 6 = 10 6 nodes. The com- puter code was implemented on a parallel, shared-memory computer platform. The results on the phase-resoled aerage flow, as well as on the turbulence characteristics, are compared with phase-resoled experimental data. The trailingortex structure in the ¤icinity of the impeller was well represented by the simulations.

Magnetically suspended fluid pump and control system

Abstract: A blood pump for assisting a heart is provided having a stator and a rotor. The rotor is magnetically radially supported creating a suspension gap between the stator and the rotor. The rotor can be supported axially by a Lorentz force bearing and can be magnetically rotated. The stator can have a single or double volute pump chamber and the rotor can have an impeller portion for pumping blood. The rotor can have a center bore as a primary blood flowpath. The suspension gap can be a secondary blood flowpath. The blood pump can also have an axial position controller and a flow rate controller. The axial position controller can cause the axial bearing to adjust the position of the rotor. The flow rate controller can have a member for measuring a dimension of a heart ventricle to control the flow rate to avoid overly distending or contracting the ventricle. A method of operating the flow rate controller to create a pulsatile flow rate is also provided. Additionally, the blood pump can be part of a cardiac assist and arrhythmia control system. Moreover, a method of operating the flow rate controller can be provided which reduces the amount of energy needed to treat fibrillation. The method can include operating the flow rate controller to reduce a radial dimension of the ventricle prior to delivering defibrillation energy such that the ventricle contains less blood which absorbs less energy so that a larger fraction of the energy is delivered to the heart.

Active magnetic bearing system for blood pump

Abstract: An implantable rotary blood pump including a rotor mounted for rotation within a pump housing. The rotor has a shaft portion and an impeller carried by the shaft portion. A rotor motor is provided, with the motor including a plurality of permanent magnets carried by the impeller and motor stators on opposite sides of the impeller. The motor is operable to transmit torque and also to provide an axial magnetic force that acts as an axial bearing.

Relation between flow pattern and blending in stirred tanks

Abstract: In the present work, the relationship between the flow pattern and blending has been investigated. The flow patterns generated by around 40 axial flow impellers have been examined. The impellers differed in blade angle, blade twist, blade width, impeller diameter, impeller location, and pumping direction. The mean-flow and turbulence characteristics generated by all of the impellers have been measured using laser doppler velocimetry (LDV). On the basis of available LDV data, the flow pattern throughout the vessel was established by employing computational fluid dynamics (CFD) and subsequently used for the simulation of the blending process. The predicted mixing times were found to be in excellent agreement with the experimental measurements. It has been shown that the dimensionless mixing time (θ) varies inversely with the secondary flow number of the impeller. Comparison of the impellers on the basis of equal power consumption per unit mass has shown that θmix ∝ NP1/3T2/3/NQS. The present CFD model has ...

Implantable centrifugal blood pump with hybrid magnetic bearings

Abstract: A pump for pumping sensitive fluids, such as blood, having no mechanical contact between the impeller and any other structure. The pump comprises a pump housing (4), an impeller (7) disposed within the pump housing, a magnetic bearing system (5, 6) for supporting and stabilizing the impeller (7) in five degrees of freedom, and a conformally shaped magnetically linked motor for rotating the impeller (7). The magnetic bearing system (5, 6) and motor advantageously comprise electromagnets and permanent magnets (18) for stability and control of the impeller (7) and to reduce size, weight and pump power consumption. Permanent magnets (18) and electromagnets are disposed on the pump housing (4) and permanent magnets (18) are disposed on the impeller (7) such that by controlling electric current through the electromagnets on the housing, the magnetically suspended impeller (7) functions as the rotor and the housing as the stator of a D.C. motor. The system advantageously allows for sensing of relative impeller position and dynamic properties without the need for additional sensors.

Design of Mixing Systems for Plant Cell Suspensions in Stirred Reactors

Abstract: The properties of dense plant cell suspensions, such as high viscosity, shear sensitivity, cell aggregation, and tendency to foam, present significant technical challenges for bioreactor design and operation. As in all fermentation processes, reactors used for large-scale plant cell culture must provide adequate mixing and mass transfer at nondamaging levels of hydrodynamic shear. In stirred vessels, this means that the impeller must be operated with restricted power input and speed, while still achieving complete gas dispersion and solids suspension. Although many experimental studies of conventional and novel impellers have been carried out, no clear guidelines for impeller choice have emerged. In this paper, an engineering analysis is used to identify which agitators and operating regimes have greatest potential for high-density plant culture applications, irrespective of whether they have been tested experimentally. Ways of improving impeller performance by modifying internal reactor geometry are also discussed.

Three-dimensional LDA measurements in the impeller region of a turbulently stirred tank

Abstract: Three-dimensional, angle-resolved LDA measure- ments of the turbulent flow field (Re\2.9)104) in the vicinity of a Rushton turbine in a baffled mixing tank have been performed. For this goal, a procedure for accurate beam alignment, based on a submerged micro-mirror system, has been developed. Results on the average flow field as well as on the complete set of Reynolds stresses are presented. The anisotropy of the turbulence has been characterized by the invariants of the anisotropy tensor. The trailing vortex structure, which is characteristic for the flow induced by a Rushton turbine, is demonstrated to be associated with strong, anisotropic turbulent activity.

Magnetically-suspended centrifugal blood pump

Abstract: A magnetically levitated blood pump having a single inlet for accepting blood and tangential volute. The pump includes an impeller formed on a hub that is suspended radially by permanent magnet bearings and axially adjusted via and thrust coil. The hub is rotated by an axial gap permanent magnet DC motor having motor magnets mounted on the hub adjacent to the impeller, a stator formed in the area opposite to the motor magnets, and motor coils formed on the stator. The axial air gap of the motor is formed in the impeller blade path. The motor may have two separate stator members. The current in the thrust coil is controlled by feedback of the impeller axial position measured by sensors. The pump components are compactly configured within a housing.

The Unsteady Pressure Field in a High Specific Speed Centrifugal Pump Impeller— Part I: Influence of the Volute

Abstract: An experimental investigation is presented regarding the unsteady pressure field within a high specific speed centrifugal pump impeller ( vS 5 1.7) which operated in a double spiral volute. For this, twenty-five piezoresistive pressure transducers were mounted within a single blade passage and sampled in the rotating impeller frame with a telemetry system. The influence of varying volume flux on the pressure transducers was evaluated in terms of pressure fluctuation magnitudes and phase differences. The magnitude information reveals that the pressure fluctuations from the impeller-volute interaction grew as the volume flux became further removed from the best efficiency point and as the trailing edge of the impeller blade was approached. These fluctuations reached 35% of the pump head in deep part load. The upstream influence of the volute steady pressure field dominates the unsteady pressure field within the impeller at all off design load points. Acquired signal phase information permits the identification of the pressure field unsteadiness within the impeller passage as fundamentally synchronized simultaneously with the volute tongue passing frequency. Special emphasis was placed on the volume flux regime where the pump and impeller pressure discharge characteristic undergo hysteresis, as impeller inlet and outlet recirculation commence and cease. A synthesis of the rotating transducers was performed to obtain unsteady blade loading parameters. The value of the unsteady lift coefficient varies on the order of 200% for a single blade in part load operation (at 45% bep), an abrupt fluctuation occurring as the fore running blade suction side passes a volute tongue. The unsteady moment coefficient and center of pressure are also shown to vary significantly during the impeller-volute tongue interaction.

Blood pump using cross-flow principles

Abstract: A blood pump is provided which comprises a cross-flow pump head having an elongated generally cylindrical housing portion. The housing portion defines a blood inlet port on a surface thereof and a blood outlet port on an opposite surface thereof. An impeller within the housing portion provides cross-flow of the blood from the inlet port around and/or across the rotational axis of the impeller to the outlet, and a motor is provided for driving the cross-flow pump head. The blood pump may be small enough to permit percutaneous insertion of the pump into a patient's blood vessel, and thus may be utilizable as a left ventricular assist device. To this end, a collapsible polymeric outlow tube is coupled to the bood flow outlet and is adapted for directing the blood from the left ventricle to the aorta through the aortic valve.

Blood pump without bearing

Abstract: Disclosed is a blood pump having a pump housing (10) in which an impeller (16) is arranged without housing. An external magnetic drive device (33) turns the impeller (16) via a magnetic coupling (32, 36). The lower side (30) of the wings (19) of the impeller is configured as a support surface (30) which slopes at the following end. A hydrodynamic supporting effect is thus obtained during rotation. Said effect raises the impeller (17) from the bottom surface of the pump housing (10). As the pump housing does not comprise bearings and seals, the thrombosis risk and the danger of penetration of foreign bodies into the blood by attrition is reduced.

Steady and Unsteady Computations of Turbulent Flows Induced by a 4/45° Pitched-Blade Impeller

Abstract: The present paper summarizes steady and unsteady computations of turbulent flow induced by a pitched-blade turbine (four blades, 45° inclined) in a baffled stirred tank. Mean flow and turbulence characteristics were determined by solving the Reynolds averaged Navier-Stokes equations together with a standard k-e turbulence model. The round vessel had a diameter of T = 152 mm. The turbine of diameter T/3 was located at a clearance of T/3. The Reynolds number (Re) of the experimental investigation was 7280, and computations were performed at Re = 7280 and Re = 29,000. Techniques of high-performance computing were applied to permit grid sensitivity studies in order to isolate errors resulting from deficiencies of the turbulence model and those resulting from insufficient grid resolution. Both steady and unsteady computations were performed and compared with respect to quality and computational effort. Unsteady computations considered the time-dependent geometry which is caused by the rotation of the impeller within the baffled stirred tank reactor. Steady-state computations also considered neglect the relative motion of impeller and baffles. By solving the governing equations of motion in a rotating frame of reference for the region attached to the impeller, the steady-state approach is able to capture trailing vortices. It is shown that this steady-state computational approach yields numerical results which are in excellent agreement with fully unsteady computations at a fraction of the time and expense for the stirred vessel configuration under consideration.

Molten metal impeller

Abstract: An impeller (101) for a molten metal pump (32) has a cylindrical body (103) comprised of a refractory material. The cylindrical body includes generally coplanar top (105) and bottom surfaces. A central bore (111) is provided in the top surface to provide a point for mating with a shaft (109). A plurality of circumferentially spaced passages (115) extend from the top or bottom surface to a side wall (117) of the impeller, each of the passages being separate and preferably having an inlet opening which is equal to or less than the corresponding outlet opening in size. A recess (107) is optionally formed in the top or bottom surface, forming the initial inlet to the passages.

Developments of the two-point workability test for high-performance concrete

Abstract: An improved version of the Tattersall two-point workability apparatus has been developed for the study of the rheology of high-performance concrete mixes. The improvements include a more compact arrangement of motor, impeller and bowl and the computer logging of the speed/torque data so that the flow curve can be obtained in a continuous sweep of about 30 s. Two impeller systems were used—an axial interrupted helix and an H-shaped impeller driven in a planetary motion with an offset gear, that is corresponding to the MH and LM systems on the previous apparatus. Both impeller systems were calibrated to enable the Bingham parameters of yield stress and plastic viscosity to be expressed in fundamental units. The performance of the apparatus was assessed by tests on a range of moderately high-performance mixes incorporating superplasticizers and cement replacement materials. The offset H impeller system was found to be suitable for testing concrete with slumps ranging from about 50 mm up to collapse, and for ...

Numerical Simulation of Impeller–Volute Interaction in Centrifugal Compressors

Abstract: A numerical procedure to predict the impeller-volute interaction in a single-stage centrifugal compressor is presented. The method couples a three-dimensional unsteady flow calculation in the impeller with a three-dimensional time-averaged flow calculation in the volute through an iterative updating of the boundary conditions on the interface of both calculation domains. The method has been used to calculate the flow in a compressor with an external volute at off-design operation. Computed circumferential variations of flow angles, total temperature, and pressure are shown and compared with measurements. The good agreement between the predictions and measurements confirms the validity of the approach.

Gas separation with split stream centrifugal turbomachinery

Abstract: A gas separation system for separating a feed gas mixture into a first gas component and a second gas component comprises a stator, and a rotor rotatably coupled to the stator. The stator includes a first stator valve face, a second stator valve surface, and a plurality of function compartments opening into the stator valve surfaces. The rotor includes a first rotor valve surface in communication with the first stator valve surface, and a second rotor valve surface in communication with the second stator valve surface. The rotor also includes a plurality of rotor flow paths for receiving gas adsorbent material therein for preferentially adsorbing the first gas component in response to increasing pressure in the rotor flow paths in comparison to the second gas component. Each rotor flow path includes a pair of opposite ends opening into the rotor valve faces for communication with the function compartments. Centrifugal turbomachinery is coupled to a portion of the function compartments, and includes an impeller which has a plurality of impeller flow paths for exposing each rotor flow path to a plurality of discrete pressures as the rotor rotates for separating the first gas component from the second gas component.

Prediction of flow fields in a dual-impeller stirred vessel

Abstract: Numerical simulations were conducted for the flow field in a baffled tank stirred by a dual Rushton impeller. For this geometry, LDV measurements show a characteristic dependence of the flow patterns upon the position of the impellers. Two advanced modeling approaches were tested. In the first, the vessel was divided into two concentric blocks, coupled by a sliding grid technique, and simulations were conducted in time-dependent mode. In the second approach, the vessel was modeled as two partially overlapping regions, the inner one rotating with the impeller and the outer one stationary; simulations were run in steady-state mode for each of the two regions, while information was iteratively exchanged between them after azimuthally averaging and transforming for the relative motion. A third set of simulations was conducted for comparison purposes by using a more conventional method, in which the impellers were not explicitly simulated, while their effects were modeled by imposing suitable values of velocities and turbulence quantities (derived from single-impeller experiments) at the blade periphery. The first two techniques gave similar predictions and successfully reproduced the dependence of the flow patterns on the position of the impellers. The latter method required far less computational effort. On the other hand, the impeller boundary conditions technique failed to reproduce the experimental flow patterns, because of the inadequacy of single-impeller boundary conditions for the present geometry.

Design of Gas-Inducing Reactors

Abstract: A gas-inducing impeller enables efficient recycling of gas from the headspace into the liquid. Historically, these impellers were used for the first time in froth flotation machines. The various designs of gas-inducing impellers (including those used in froth flotation) could be classified into three categories, depending on the flow pattern coming into and leaving the impeller zone. These are denoted as type 11, type 12, and type 22 systems. The critical impeller speed for the onset of gas induction (NCG) is governed by a balance between the velocity head generated by the impeller and the hydrostatic head above the impeller. A number of correlations (for types 11 and 22) are based on this balance (Bernoulli's equation). The rate of gas induction (QG) for the type 11 system can be accurately determined by equating the pressure difference (between the impeller zone and the headspace) generated by the impeller and the pressure drop required for the flow of gas. For type 22 systems, the correlations for QG a...

Centrifugal blood pump apparatus

Abstract: A centrifugal impeller-type pump for transporting blood has a new and improved design in the impeller, to allow for the elimination of stagnant flow areas, and a geometrical design that minimizes damage to the blood components. A system for controlling and stabilizing the speed of centrifugal-type pumps used in a human cardiovascular system is also provided. Further provided are methods of corrosion protection and enhancing thromboresistance, rejection of waste heat, and methods to connect the artificial heart to the cardiovascular system as a Left Ventricle Assist Device (LVAD) and as a Total Artificial Heart (TAH).

Contactless hermetic pump

Abstract: A hermetic pump includes a housing having a bore, an inlet, and an outlet for channeling a fluid therethrough. A shaft is disposed coaxially in the bore, and includes a journal and an impeller spaced apart therefrom. The shaft is hermetically rotated to pump the fluid through the bore from the impeller and around the journal for developing a hydrodynamic journal bearing. In one embodiment, the pump may be used in a closed loop cooling circuit.

Low speed high pressure ratio turbocharger

Abstract: A low speed high pressure ratio turbocharger incorporates a compressor impeller having impeller blades for a first stage of compression mounted on a first side of the wheel and impeller blades for a second stage of compression mounted on a second side of the wheel. Driving the dual sided compressor impeller on a common shaft from the turbine wheel allows reduction in rotational speeds while increasing compression ratio of the turbine. The scroll inlet and outlet volute for the second stage inducer are integrated with the compressor housing or other portions of the turbocharger case for compact packaging.

Centrifugal pump with solids cutting action

Abstract: A centrifugal pump has an impeller rotatable by means of a drive shaft. The impeller has a plurality of radially extending vanes connected to a hub and a partial back shroud with sharpened leading edges. The pump has a pump casing with a back plate adjacent to the back side of the impeller. Spiral grooves on the back plate interact with the sharpened edges on the back shroud to aid in protecting the area between the back plate and the impeller by cutting of solids and expulsion of solids through an output port. Cutting bars on the front plate of the casing project into the pump intake and interact with front edges of the vanes to cut incoming solids in a liquid mixture. A preferred form of impeller has vanes with sharpened leading edges that extend in a generally radial plane. These vanes sweep backwardly from their leading edges and each vane is given a double twist between the leading edge and its trailing edge. This form of impeller has both an effective slicing action and an efficient transmission of kinetic energy to the fluid.

Computational fluid dynamics analysis to establish the design process of a centrifugal blood pump: second report.

Abstract: To establish an efficient design process for centrifugal blood pumps, the results of computational fluid dynamics (CFD) analysis were compared to the results of flow visualization tests and hemolysis tests, using the Nikkiso centrifugal blood pump. CFD analysis revealed that the radial gap greatly affected the shear stress in the outlet diffuser. The hemolysis study also indicated a similar tendency. To see the flow behind the impeller, we conducted a comparative study between models with and without washout holes using the CFD technique. CFD analysis indicated that flow and pressure distributions behind the impeller were different between both models, and a particle was observed to remain longer behind the impeller in the model without washout holes. In the future, CFD analysis could be a useful tool for developing blood pumps in comparison to flow visualization tests and hemolysis tests.

Effects of high-shear granulation on granulate homogeneity.

Abstract: This study considers the effects of particle size of the powder constituents, and of impeller speed on the homogeneity of drug distribution on granulations produced in high-speed mixers. When a micronized low-dose steroid hormone was granulated together with unmicronized lactose in a Vactron 75 high-shear granulator at 250 rpm, strong inhomogeneities of the drug distribution arose. The coarse particle size fractions of the granules were found to be superpotent up to 150% of the mean drug content, whereas the fine size fraction showed a corresponding subpotency of 50%. Both particle size and impeller speed attributed to this phenomenon. At an impeller speed of 75 rpm, a significantly better drug distribution was obtained. Results show that the inhomogeneities found are mainly a consequence of the balance between the impact pressure as exerted by the impeller on the one hand and the shear resistance of the nuclei on the other hand. At a speed of 250 rpm, the tensile strength of 3× 103 N/m2 of the initially ...

Rotary blood pump with ceramic members

Abstract: An implantable rotary blood pump including a rotor mounted for rotation within a pump housing. The rotor has a shaft portion and an impeller carried by the shaft portion. A rotor motor is provided, with a motor including a plurality of permanent magnets carried by the impeller and motor stators on opposite sides of the impeller. Structural members are provided between the impeller and stators to provide structural support and hermetical sealing. The structural members comprise biocompatible, corrosion resistant, electrically non-conducting ceramic material, which alleviate eddy current losses.

Turbine engine with cooled p3 air to impeller rear cavity

Abstract: An air distribution system for an impeller rear cavity (30), including an air bleed (46) at the compressor impeller (22) tip for bleeding pressurized air into the rear cavity, and a second stream of P3 air is passed into the rear cavity area (30) after having been cooled by a heat exchanger (36). The mixing of the cooled P3 air (46) with the bleed air from the impeller tip reduces the temperature of the pressurized air in the rear cavity to reduce degradation of the impeller as well as to provide a flow of cooling air for the central bearing.

Low noise fan

Abstract: A collectorless vacuum fan for floor maintenance machines has a backplate with an inlet plate attached thereto in spaced relationship, and an impeller between the backplate and inlet plate Both the backplate and the inlet plate extend radially beyond the periphery of the impeller A shaft mounts the impeller for rotation The inlet plate has a central opening providing air to the hub of the impeller Vanes on the impeller discharge air out through a diffuser channel defined by the space between the inlet plate and the backplate outside the periphery of the impeller Attachment elements for mounting the inlet plate on the backplate leave the diffuser channel substantially unobstructed so that air is discharged about the entire periphery of the impeller The fan has increased air flow compared to a conventional fan having an integral collector housing and decreased noise compared to a fan having a 360 degree discharge and no diffuser