Showing papers on "Impeller published in 2007"

Heart assist device with expandable impeller pump

Abstract: An impeller includes a hub and a blade supported by the hub. The impeller has a stored configuration in which the blade is compressed so that its distal end moves towards the hub, and a deployed configuration in which the blade extends away from the hub. The impeller may be part of a pump for pumping fluids, such as blood, and may include a cannula having a proximal portion with a fixed diameter, and a distal portion with an expandable diameter. The impeller may reside in the expandable portion of the cannula. The cannula may have a compressed diameter which allows it to be inserted percutaneously into a patient. Once at a desired location, the expandable portion of the cannula may be expanded and the impeller expanded to the deployed configuration. A flexible drive shaft may extend through the cannula for rotationally driving the impeller within the patient.

Multidisciplinary Optimization of a Radial Compressor for Microgas Turbine Applications

Abstract: A multidisciplinary optimization system and its application to the design of a small radial compressor impeller are presented. The method uses a genetic algorithm and artificial neural network to find a compromise between the conflicting demands of high efficiency and low centrifugal stresses in the blades. Simultaneous analyses of the aero performance and stress predictions replace the traditional time consuming iterative design approach. The aerodynamic performance, predicted by a 3D Navier-Stokes solver, is maximized while limiting the mechanical stresses to a maximum value. The stesses are calculated by means of a finite element analysis and controlled by modifying the blade camber, lean and thickness at the hub. The results show that it is possible to obtain a significant reduction of the centrifugal stresses in the blades without penalizing the performance.© 2007 ASME

Compact low noise efficient blower for cpap devices

Abstract: The present invention relates to a blower comprising an electric motor having a shaft, said shaft defines a shaft axis; a housing having a housing inlet and a housing outlet between which is defined a flow path for gas; the housing outlet is structured to direct gas exiting the blower in a substantially axial first direction; the motor has a first side proximal said housing inlet, and a second side distal said housing inlet; a first impeller having a plurality of blades adapted to accelerate gas tangentially and to direct it radially outward and being attached to the shaft on the first side of the motor; a stationary portion including: a gas flow path defined between the motor external wall and a wall of the stationary portion, said flow path being of sufficient width to allow a flow of gas therethrough without introducing excessive pressure drop, said flow path directing gas to flow in a generally axial direction from the first side of the motor to the second side of the motor; a first stationary vane structure located downstream of the first impeller, the first stationary vane structure adapted to direct gas exiting the first impeller from flowing in a substantially tangential direction to flowing in both a radial and axial direction; and a shield constructed and arranged to provide a barrier between the first stationary vane structure and the blades of the first impeller to isolate leading edges of the first stationary vane structure from an impeller blade pressure pulse.

Numerical Flow Simulation in a Centrifugal Pump at Design and Off-Design Conditions

Abstract: The current investigation is aimed to simulate the complex internal flow in a centrifugal pump impeller with six twisted blades by using a three-dimensional Navier-Stokes code with a standard k-ε two-equation turbulence model. Different flow rates were specified at inlet boundary to predict the characteristics of the pump. A detailed analysis of the results at design load, Qdesign, and off-design conditions, Q = 0.43 Qdesign and Q = 1.45 Qdesign, is presented. From the numerical simulation, it shows that the impeller passage flow at design point is quite smooth and follows the curvature of the blade. However, flow separation is observed at the leading edge due to nontangential inflow condition. The flow pattern changed significantly inside the volute as well, with double vortical flow structures formed at cutwater and slowly evolved into a single vortical structure at the volute diffuser. For the pressure distribution, the pressure increases gradually along streamwise direction in the impeller passages. When the centrifugal pump is operating under off-design flow rate condition, unsteady flow developed in the impeller passage and the volute casing.

Influence of Splitter Blades on the Flow Field of a Centrifugal Pump:Test-Analysis Comparison

Abstract: This work aims at studying the influence of adding splitter blades on the performance of a hydraulic centrifugal pump. The studied machine is an ENSIVAL-MORET MP 250.200.400 pump (diameter = 408 mm, 5 blades, specific speed = 32), whose impeller is designed with and without splitter blades. Velocity and pressure fields are computed using unsteady Reynolds-averaged Navier-Stokes (URANS) approach at different flow rates. The sliding mesh method is used to model the rotor zone motion in order to simulate the impeller-volute casing interaction. The flow morphology analysis shows that, when adding splitter blades to the impeller, the impeller periphery velocities and pressures become more homogeneous. An evaluation of the static pressure values all around the impeller is performed and their integration leads to the radial thrust. Global and local experimental validations are carried out at the rotating speed of 900 rpm, for both the original and the splitter blade impellers. The head is evaluated at various flow rates: 50 % , 80 % , 100 % , and 120 % of the flow rate at the best efficiency point (BEP). The pressure fluctuations are measured at four locations at the BEP using dynamic pressure sensors. The experimental results match the numerical predictions, so that the effect of adding splitter blades on the pump is acknowledged. Adding splitters has a positive effect on the pressure fluctuations which decrease at the canal duct.

Spike and Modal Stall Inception in an Advanced Turbocharger Centrifugal Compressor

Abstract: In turbocharger applications bleed air near the impeller exit is often used for secondary flow systems to seal bearing compartments and to balance the thrust load on the bearings. There is experimental evidence that the performance and operability of highly loaded centrifugal compressor designs can be sensitive to the amount of bleed air. To investigate the underlying mechanisms and to assess the impact of bleed air on the compressor dynamic behavior, a research program was carried out on a pre-production, 5.0 pressure ratio, high-speed centrifugal compressor stage of advanced design. The investigations showed that bleed air can significantly reduce the stable flow range. Compressor rig experiments, using an array of unsteady pressure sensors and a bleed valve to simulate a typical turbocharger environment, suggest that the path into compression system instability is altered by the bleed flow. Without bleed flow, the pre-stall behavior is dominated by short wavelength disturbances, or so called ‘spikes’, in the vaneless space between the impeller and the vaned diffuser. Introducing bleed flow at impeller exit reduces endwall blockage in the vaneless space and destabilizes the highly-loaded vaned diffuser. The impact is a 50% reduction in stable operating range. The altered diffuser characteristic reduces the compression system damping responsible for long wavelength, modal pre-stall behavior. A four-lobed backward traveling rotating stall wave is experimentally measured, in agreement with calculations obtained from a previously developed dynamic compressor model. In addition, a self-contained, endwall blockage control strategy was employed, successfully recovering 75% of the loss in surge-margin due to bleed flow and yielding a 1 point increase in adiabiatic compressor efficiency.Copyright © 2007 by ASME

Shrouded thrust bearings

Abstract: A rotary blood pump includes a casing defining a pumping chamber The pumping chamber has a blood inlet and a tangential blood outlet One or more motor stators are provided outside of the pumping chamber A rotatable impeller is within the pumping chamber and is adapted to cause blood entering the pumping chamber to move to the blood outlet The impeller has one or more magnetic regions The impeller is radially constrained in rotation by magnetic coupling to one or more motor stators and is axially constrained in rotation by one or more hydrodynamic thrust bearing surfaces on the impeller

Transient Behavior of Turbomachineries: Applications to Radial Flow Pump Startups

Abstract: A theoretical analysis of the fast transients of turbomachineries, based on the study of unsteady and incompressible fluids mechanics equations applied to an impeller, is proposed. It leads to internal torque, internal power, and impeller head of an impeller during transient periods. The equations show that the behavior of a pump impeller is not only depending on the acceleration rate and flow rate, as it is usually admitted, but also on velocity profiles and their evolution during the transient. Some hypotheses on the flow in a radial flow pump are proposed. They are validated by comparison with the experimental results of a single stage, single volute radial flow pump during some fast acceleration periods. The model is also used to analyze the behavior of the pump during a fast startup.

Power and Mixing Time Study Involving a Maxblend® Impeller with Viscous Newtonian and Non-Newtonian Fluids

Abstract: Physical investigations have been carried out to characterize the power consumption and the mixing time in a vessel equipped with a Maxblend ® impeller (Sumitomo Mechanical Equipment, Japan). The laminar, transition and turbulent flow regimes were investigated using viscous Newtonian and non-Newtonian shear-thinning fluids. For the determination of the mixing times, a discolouration method based on a fast acid-base reaction was used in conjunction with image analysis to generate mixing evolution curves. Three vessel sizes were used from which the influence of the scale on the mixing efficiency and the power consumption could be determined. With the geometrically similar mixers used here, it was clearly shown that power and efficiency do not depend on the scale, under certain conditions. The power consumption was found almost identical as that of an anchor but far lower than that of a double helical ribbon impeller. The power and shear constants, K p and K s , were found very sensitive to small variations in the bottom clearance. The K s value remained almost constant for a wide range of flow indices. The dimensionless mixing time, Nt m , decreased with the reciprocal of the Reynolds number in the laminar flow region. Based on data from the literature, a comparison with many different large impellers also indicated that the Maxblend technology makes better use of the mixing power in the upper part of the laminar regime and in the low turbulent regime.

Numerical Investigation on Pressure Fluctuations for Different Configurations of Vaned Diffuser Pumps

Abstract: Numerical simulations on impeller-diffuser interactions in radial diffuser pumps are conducted to investigate the unsteady flow, and more attention is paid to pressure fluctuations on the blade and vane surfaces. Calculations are performed at different operating points, different blade number configurations, and different radial gaps between the impeller and diffuser to examine their effects on the unsteady flow. Computational results show that a jet-wake flow structure is observed at the impeller outlet. The biggest pressure fluctuation on the blade is found to occur at the impeller trailing edge, on the pressure side near the impeller trailing edge, and at the diffuser vane leading edge, independent of the flow rate, radial gap, and blade number configuration. All of the flow rate, blade number configuration, and radial gap influence significantly the pressure fluctuation and associated unsteady effects in the diffuser pumps.

Disposable spinner flask

Abstract: The present invention relates generally to a cell culture stirring vessel and associated impeller. More particularly, it relates to a fully integrated, disposable spinner flask vessel having a suspended impeller assembly permanently integrated therein. The invention is particularly suitable for use in applications where cells are suspended within a liquid medium with minimal shear forces.

Turbocharger with variable nozzle

Abstract: A turbocharger (10) with a variable nozzle has a turbine impeller (2), a compressor impeller (4), a shaft (5) coupling the turbine impeller (2) and the compressor impeller (4), a bearing housing (6) rotatably supporting the shaft (5), and a turbine housing (7) accommodating the turbine impeller (2). The turbocharger further includes a variable nozzle mechanism (12), provided in a radial-direction outer side of the turbine impeller (2), for adjusting a flow rate of an exhaust gas directed to the turbine impeller (2). The bearing housing (6) has a radially expanded portion (6a) that extends to a radial-direction outer side to be coupled to the turbine housing (7) at a radial-direction outer side portion thereof such that the variable nozzle mechanism (12) is accommodated between the turbine housing (7) and the radially expanded portion (6a). Between the variable nozzle mechanism (12) and the radially expanded portion (6a), a heat shield plate (21) is provided for preventing a heat transmission between them.

Wear analysis of centrifugal slurry pump impellers

Abstract: Purpose – To design and fabricate a wear testing rig for a water pump impeller and to select a parameter that can be used to determine the wear rates of slurry pump impeller.Design/methodology/approach – A wear equipment was designed and fabricated in this study that of main rotating shaft, supported by two ball bearings, and main electric motor bully mechanism for the rotational speed torque needed. An impeller made of cast iron was selected. The wear medium selected consists of solid particles and water. The tests were conducted by letting the impeller to rotate in slurry. The wear data collection are divided into impeller's weight loss, impeller's diameter loss, impeller blade's thickness loss, impeller's blade height loss and impeller's thickness change.Findings – The major type of wear that takes place in this experiment is erosion. The weight loss of the impeller is due to the material removal from the impeller as result of erosion wear. The diameter loss of the impeller is attributed to the impinge...

Using computational fluid dynamics modeling and ultrasonic doppler velocimetry to study pulp suspension mixing

Abstract: In this study, the flow field of a cylindrical pulp mixing chest equipped with a side-entering impeller was modeled using commercial computational fluid dynamics (CFD) software (Fluent) with the rheology of the pulp suspension approximated using the Herschel-Bulkley model. To validate the model, CFD results for the power and velocity field were compared to experimental data. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure pulp suspension velocity. In order to calculate the mixing time, an unsteady state solver in Fluent was applied to monitor the tracer species concentration as a function of time in the tank. The validated CFD model provided useful information regarding the mixing time and the formation of the cavern around the impeller in the mixing of pulp suspension. The size of cavern predicted by the CFD model was in good agreement with that calculated using Solomon's model.

Experimental and Numerical Analysis of Power Consumption for Mixing of High Viscosity Fluids with a Co-Axial Mixer

Abstract: An experimental and numerical programme has been carried out to explore and determine design and mixing performance characteristics of co-axial agitation systems. Power consumption analyses in Newtonian and non-Newtonian fluids in laminar regime for a co-axial mixer configuration for chemical processes are discussed. An anchor impeller was used in combination with a dual set of pitched blade turbines in co-rotating mode. It was demonstrated that the power consumption of the proximity impeller is affected by the tip speed ratio, but no influence of the proximity impeller speed on the power drawn by the pitched blade turbines was observed. Computational fluid dynamics (CFD) was employed to calculate the flow field created by the co-axial mixer. CFD was able to predict well the power consumption of the co-axial mixing system. Power and Reynolds number were adapted to obtain the power characteristics of co-axial mixers. The approach employed to obtain a single master power curve succeeded for the investigated co-axial mixer configuration and is a useful engineering tool to predict the power consumption of co-axial mixing systems.

Air Entrainment in Baffled Stirred Tanks

Abstract: The impeller speed at which air is first entrained from the surface of a stirred tank ( N E ) is an operational limit. Where air entrainment is desirable, it is a lower limit, but where air entrainment is detrimental it is an upper limit. This study (1) determines parameters which affect N E and (2) develops a mechanistic model of air entrainment. Experiments were conducted to determine the effect of impeller submergence, impeller diameter, baffle geometry, and the physical properties of the fluid on N E for an up-pumping (PBTU), and a down-pumping pitched blade turbine (PBTD). Mean and RMS velocity profiles were measured for selected cases using laser Doppler velocimetry (LDV). Using this data, air entrainment in stirred tanks and at other free surfaces is compared and is found to depend on the balance between gravity, surface tension and surface turbulence. There must be sufficient turbulence at the surface to overcome surface tension and form bubbles. The entrained bubble size is determined by the mean flow below the surface, which acts to pull the bubbles into the tank. It is shown that impeller variables, such as the power number, impeller speed and diameter, cannot predict the point of air entrainment at the surface. The key predicting variable is the ratio of u , the RMS velocity at the surface, to the mean downward velocity U . At the point of air entrainment, this velocity ratio just balances the physical properties of the fluid.

Heart assist device

Abstract: A heart assist device comprising a rotary pump housing having a cylindrical bore, a pumping chamber and a motor stator including an electrically conductive coil located within the housing and surrounding a portion of the cylindrical bore. A rotor has a cylindrical shaft, at least one impeller appended to one end of the shaft, and a plurality of magnets located within the shaft. The rotor shaft is positioned within the housing bore with the magnets opposite the motor stator, and the impeller is positioned within the pumping chamber. The housing bore is closely fitted to the outer surface of the shaft forming a hydrodynamic journal bearing, with the pumping chamber and journal bearing connected by a leak path of blood flow between the pumping chamber and the journal bearing. A backiron of the motor stator attracts the rotor magnets to resist longitudinal displacement of the rotor within the housing during operation. The relative orientation of positions of the inflow, outflow, and leakage flow paths may be varied within the pump, such as to accommodate different intended methods for implantation and/or use.

Numerical simulation of an axial blood pump.

Abstract: The axial blood pump with a magnetically suspended impeller is superior to other artificial blood pumps because of its small size. In this article, the distributions of velocity, path line, pressure, and shear stress in the straightener, the rotor, and the diffuser of the axial blood pump, as well as the gap zone were obtained using the commercial software, Fluent (version 6.2). The main focus was on the flow field of the blood pump. The numerical results showed that the axial blood pump could produce 5.14 L/min of blood at 100 mm Hg through the outlet when rotating at 11 000 rpm. However, there was a leakage flow of 1.06 L/min in the gap between the rotor cylinder and the pump housing, and thus the overall flow rate the impeller could generate was 6.2 L/min. The numerical results showed that 75% of the scalar shear stresses (SSs) were less than 250 Pa, and 10% were higher than 500 Pa within the whole pump. The high SS region appeared around the blade tip where a large variation of velocity direction and magnitude was found, which might be due to the steep angle variation at the blade tip. Because the exposure time of the blood cell at the high SS region within the pump was relatively short, it might not cause serious damage to the blood cells, but the improvement of blade profile should be considered in the future design of the axial pump.

Using CFD and Ultrasonic velocimetry to Study the Mixing of Pseudoplastic Fluids with a Helical Ribbon Impeller

Abstract: A commercial CFD package was used to simulate the 3D flow field generated in a cylindrical tank by a helical ribbon impeller. The study was carried out using a pseudoplastic fluid with yield stress in the laminar mixing region. Ultrasonic Doppler velocimetry (UDV), a noninvasive fluid flow measurement technique for opaque systems, was used to measure xanthan gum velocity. From flow field calculations and tracer homogenization simulations, power consumption and mixing time results were obtained. The torque and power characteristics remain the same for upward and downward pumping of the impeller, but the mixing times are considerably longer for the downward pumping mode. Overall, the numerical results showed good agreement with experimental results and correlations developed by other researchers. From the power and mixing time results, two efficiency criteria were utilized to determine the best pumping mode of the impeller.

Studies on the Influence of Various Blade Outlet Angles in a Centrifugal Pump when Handling Viscous Fluids

Abstract: In this study the centrifugal pump performances with different blade outlet angles are tested when handling water and viscous oils as Newtonian fluids. Also, this study shows a numerical simulation of the three-dimensional fluid flows inside the centrifugal pump with different blade outlet angles. For these numerical simulations the SIMPLEC algorithm is used for solving governing equations of incompressible viscous/turbulent flows through the pump at different operating conditions. The k-e turbulence model is adopted to describe the turbulent flow process. These simulations have been made with a steady calculation using the multiple reference frames (MRF) technique to take into account the impeller- volute interaction. Numerical results are compared with the experimental characteristic curve for each viscous fluid. The results show that when the outlet angle increases, the centrifugal pump performance handling viscous fluids improves. This improvement is due to decrease of wake at the exit of impeller. Also the results show that the well-known jet/wake flow model is not found in the impeller simulations.

Numerical investigation of performance of an axial-flow pump with inducer

Abstract: The interaction of flow through the inducer and impeller of an axial-flow pump equipped with an inducer has significant effect on its performance. This article presents a recent numerical investigation on this topic. The studied pump has an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of the impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. A computational fluid dynamics code was used to investigate the flow characteristics and performance of the axial-flow pump. For turbulence closure, the RNG k-e model was applied with an unstructured grid system. The rotor-stator interaction was treated with a Multiple Reference Frame (MRF) strategy. Computations were performed in different cases: 7 different relative circumferential angles (Δθ) between the inducer blade trailing edge and the impeller blade leading edge, and 3 different axial gaps (G) between the inducer and the impeller. The variation of the hydraulic loss in the rotator was obtained by changing Δθ. The numerical results show that the pressure generated is minimum in the case of (G = 3% D), which indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances were predicted and compared to the experimental measurements. Recommendations for future modifications and improvements to the pump design were also given.