Showing papers on "Impeller published in 2003"

Flow in a Centrifugal Pump Impeller at Design and Off-Design Conditions—Part I: Particle Image Velocimetry (PIV) and Laser Doppler Velocimetry (LDV) Measurements

Abstract: Detailed optical measurements of the flow inside the rotating passages of a six-bladed shrouded centrifugal pump impeller of industrial design have been performed using particle image velocimetry (PIV) and laser Doppler velocimetry (LDV). Results include instantaneous and ensemble averaged PIV velocity vector maps as well as bin-resolved LDV data acquired in the midplane between hub and shroud of the impeller. The flow is surveyed at both design load and at severe off-design conditions. At design load, Q =Q d , the mean field of relative velocity is predominantly vane congruent, showing well-behaved flow with no separation. At quarter-load, Q=0.25Q d , a previously unreported two-channel phenomenon consisting of alternate stalled and unstalled passages was observed, with distinct flow congruence between every second of the six passages. A large recirculation cell blocked the inlet to the stalled passage while a strong relative eddy dominated the remaining parts of the passage. The stall phenomenon was steady, nonrotating and not initiated via the interaction with stationary components

Flow in a Centrifugal Pump Impeller at Design and Off-Design Conditions—Part II: Large Eddy Simulations

Abstract: The flow field in a shrouded six-bladed centrifugal pump impeller has been investigated using large eddy simulation (LES). The effect of the subgrid scales has been modeled through a localized dynamic Smagorinsky model implemented in the commercial CFD code FINE/Turbo. A detailed analysis of the results of LES at design load, Q =Q d , and severe off-design conditions, at quarter-load Q=0.25Q d , is presented. At design load LES reveals a well-behaved flow field with no significant separation. At quarter-load significant differences between adjacent impeller passages are revealed. A steady nonrotating stall phenomenon is observed in the entrance of one passage and a relative eddy develops in the remaining part of the passage. The stall unblocks the adjacent passage which exhibits a flow dominated by rotational effects. Velocities predicted by LES and steady-state Reynolds averaged Navier-Stokes (RANS) simulations based on the Baldwin-Lomax and Chien k-e turbulence models are compared with experimental data obtained from particle image velocimetry (PIV)

Liquid-phase mixing in stirred vessels: turbulent flow regime

Abstract: The published literature on the liquid-phase mixing in a turbulent flow regime has been critically reviewed and analyzed. Experimental techniques for mixing time have been described together with their relative merits. The effects of the impeller design (blade number, blade angle, blade and disk dimensions, and blade shape), the location of the impeller (off-bottom clearance, distance from the vessel center, i.e., eccentricity), and the vessel size on the liquid-phase mixing have been critically analyzed. The mixing performance dependency on the internals such as baffles (number, dimension, and position) and the draft tube has been presented in detail. Further, an extensive review on the mathematical models proposed for the liquid-phase mixing has been presented, and the utility of the computational fluid dynamics modeling for the mixing optimization has been illustrated. Finally, suggestions have been made for the selection of an energy-efficient impeller−vessel configuration, and directions have been gi...

Experimental and Numerical Studies in a Centrifugal Pump With Two-Dimensional Curved Blades in Cavitating Condition

Abstract: In the presented study a special test pump with two-dimensional curvature blade geometry was investigated in cavitating and noncavitating conditions using different experimental techniques and a three-dimensional numerical model implemented to study cavitating flows. Experimental and numerical results concerning pump characteristics and performance breakdown were compared at different flow conditions. Appearing types of cavitation and the spatial distribution of vapor structures within the impeller were also analyzed. These results show the ability of the model to simulate the complex three-dimensional development of cavitation in a rotating machinery, and the associated effects on the performance.

Electric blower and vacuum cleaner using the same

Abstract: An electric blower (37) includes a main body (47) incorporating therein a suction inlet (46) for suctioning dust and an electric blower for generating an air suction stream; an outlet (54) through which air discharged from the electric blower (37) is exhausted outside; a control unit (43) for controlling an operation of the electric blower, wherein the electric blower including an impeller (50) for generating the air suction stream by the rotation thereof, a casing (53) enclosing the impeller, and exhaust openings (51) formed in the casing through which a part of an air stream suctioned by the impeller (50) is discharged; and the control unit (43) is disposed on an air path (58) between the exhaust openings (51) and the outlet (47).

Noise as an indicator of cavitation in a centrifugal pump

Abstract: One of the sources of instability in a centrifugal pump is cavitation within the pump. Cavitation of a centrifugal pump is the result of insufficient net positive suction head (NPSH) and can occur within the entire range of operating conditions. Cavitation may cause three different and undesirable effects: (1) a drop in head-capacity and efficiency curves, (2) damage to the impeller by pitting and erosion, and (3) structure vibration and resulting noise. Therefore, the cavitation process must be prevented by all means. To prevent the onset of cavitation we have to detect the beginning of the cavitation process in the pump. To detect the beginning of the cavitation process, the emitted noise can be used, among other possibilities. Specifically, a noise spectra structure can be used to detect the beginning of cavitation and its development. Experiments have shown that there is a discrete frequency tone, at 147 Hz, which is strongly dependent on the cavitation process and its development. Therefore, noise spectra can also be used to determine the NPSH required or the critical value, representing the upper limit of the permissible pump operation without cavitation.

Integrated turbine power generation system with catalytic reactor

Abstract: The invention provides integrated turbogenerators having a turbine wheel, a compressor impeller, and a motor generator mounted to or mechanically constrained to a common shaft, and improved components and configurations thereof.

Experimental and Numerical Study of Unsteady Flow in a Diffuser Pump at Off-Design Conditions

Abstract: An experimental and numerical study was developed for the unsteady phenomena at off-design conditions of a diffuser pump. Unsteady pressure measurements were made downstream of the impeller, and the pressure fluctuations were analyzed using the ensemble averaging technique as well as the statistical and chaotic time series analysis. The unsteady flow was classified into five ranges as a result of the statistical and chaotic time series analysis. And a two-dimensional vortex method was employed to investigate the unsteady flow structure due to the interaction between impeller and diffuser vanes in a diffuser pump at various off-design conditions

Investigation of Flow Through Centrifugal Pump Impellers Using Computational Fluid Dynamics

Abstract: With the aid of computational fluid dynamics, the complex internal flows in water pump impellers can be well predicted, thus facilitating the design of pumps. This article describes the three-dimensional simulation of internal flow in three different types of centrifugal pumps (one pump has four straight blades and the other two have six twisted blades). A commercial three-dimensional Navier-Stokes code called CFX, with a standard k – e two-equation turbulence model was used to simulate the problem under examination. In the calculation, the finite-volume method and an unstructured grid system were used for the solution procedure of the discretized governing equations for this problem.Comparison of computational results for various types of pumps showed good agreement for the twisted-blade pumps. However, for the straight-blade pump, the computational results were somewhat different from widely published experimental results. It was found that the predicted results relating to twisted-blade pumps were better than those relating to the straight-blade pump, which suggests that the efficiency of a twisted-blade pump will be greater than that of a straight-blade pump. The calculation also predicts reasonable results in both the flow pattern and the pressure distribution.

Centrifugal fluid pump assembly

Abstract: A centrifugal fluid pump assembly 1 includes a body section 5 and a control mechanism 6. The body section 5 includes a housing 20, an impeller 21 rotatable within the housing 20, and a motor 34 for rotating the impeller 21. The pump assembly 1 includes a motor current flow rate-related data storage section 60 for storing, for a plurality of different predetermined viscosities, predetermined viscosity-related flow rate data formed from a plurality of motor current flow rate relation data at a plurality of different impeller rotational speeds at predetermined fluid viscosity, a fluid measurement data inputting section 57, an impeller rotational speed measurement function, a motor current measurement function, and a flow rate calculating section 58 for using a fluid viscosity value, an impeller rotational speed value, a measured motor current and data stored in the motor current flow rate-related data storage section 60 to calculate a fluid flow rate.

Impeller for molten metal pump with reduced clogging

Abstract: One aspect of the invention is directed to an impeller made of a non-metallic, heat resistant material, comprising a generally cylindrical shaped body, first and second generally planar end faces and a side wall extending between the first and second faces. A plurality of passages have inlets circumferentially spaced apart from each other on the first face, outlets at the impeller sidewall, and connecting portions extending between the inlets and the outlets transverse to the central axis. Another aspect of the invention is directed to an impeller comprising a central hub portion and first and second impeller bases, including end faces, transverse to a central axis. Vanes extend from the central hub portion between the impeller bases. Cavities are formed between the impeller bases and between adjacent vanes. Molten metal inlets on the end faces for molten metal to reach the cavities. Pumps are also disclosed using the inventive impellers.

On the direct measurement of turbulence energy dissipation in stirred vessels with PIV

Abstract: The mean flow and turbulence fields and the turbulence energy dissipation rate (e) in a vessel stirred by a hydrofoil impeller were studied using particle image velocimetry (PIV). The vessel diameter was 100 mm, and it was stirred by an impeller of diameter D = T/3. The impeller Reynolds number was 40 000 to ensure fully turbulent flow in the vessel. Particular attention was paid to the effect of spatial resolution on the estimation of e, which was determined directly from its definition, i.e., by measuring the instantaneous spatial gradients of the Reynolds stresses. The data provide new information on the quantification and distribution of e in stirred vessels and indicate that estimates of dissipation based on a constant length scale across the vessel and the distribution of the turbulence levels may underestimate the maximum and overestimate the minimum levels of e present in a stirred vessel.

Motor driven centrifugal compressor/blower

Abstract: This invention provides a small, high efficiency, oil free motor driven compressor/blower suitable for providing pressurized, contamination-free gas and or air to transportation, industrial and aerospace fuel cell systems or other contaminant-intolerant applications. The motor driven compressor/blower rotor assembly is supported by foil air bearings and rotates at high speed by using a high frequency drive. The impeller is a centrifugal type design. The MDC can be easily integrated into the air management system of a fuel cell.

Gas−Liquid Flow Generated by a Pitched-Blade Turbine: Particle Image Velocimetry Measurements and Computational Fluid Dynamics Simulations

Abstract: Axial-flow impellers, like pitched-blade impellers, are being increasingly used for gas−liquid systems in stirred vessels. In this work we have used particle image velocimetry (PIV) and computational fluid dynamics (CFD) models to investigate gas−liquid flow generated by a downflow pitched-blade turbine. PIV measurements were carried out in a fully baffled stirred vessel (of 0.19 m diameter) with a dished bottom. Angle-resolved measurements of the flow field with and without gas dispersion were carried out. An attempt was made to capture key details of the trailing vortex, the accumulation of gas, and the flow around the impeller blades. A two-fluid model along with the standard k−e turbulence model was used to simulate dispersed gas−liquid flow in a stirred vessel. The computational snapshot approach was used to simulate impeller rotation and was implemented in the commercial CFD code, FLUENT 4.5 (of Fluent Inc., USA). The model predictions were verified by comparison with the PIV measurements and other ...

Disk friction losses of closed turbomachine impellers

Abstract: The power losses created by the shrouds of closed turbomachine impellers depends on Reynolds-number, surface roughness, rate and direction of leakage flow through the impeller side room and on the pre-swirl with which said leakage enters the side room. These parameters determine also fluid rotation between impeller and casing and axial thrust. While all of these effects have been treated in the literature, a generic procedure has been lacking, which would allow to predict, in a consistent and logical way, the impact of all of these boundary conditions on disk friction and fluid rotation. To fill this gap a method is presented and validated with test data. The formulae developed cover laminar, turbulent, smooth and rough flow regimes and ensure a smooth transition between these domains.

The Inlet Flow Structure of a Centrifugal Compressor Stage and Its Influence on the Compressor Performance

Abstract: The performance of centrifugal compressors can be seriously degraded by inlet flow distortions that result from an unsatisfactory inlet configuration. In this present work, the flow is numerically simulated and the flow details are analyzed and discussed in order to understand the performance behavior of the compressor exposed to different inlet configurations. In a previous work, complementary to this present work, experimental tests were carried out for the comparison of a centrifugal compressor stage performance with two different inlet configurations: one of which was a straight pipe with constant cross-sectional area and the other a 90-deg curved pipe with nozzle shape. Steady-state compressor stage simulation including the impeller and diffuser with three different inlets has been carried out to investigate the influence of each inlet type on the compressor performance. The three different inlet systems included a proposed and improved inlet model. The flow from the bend inlet is not axisymmetric in the circumferential and radial distortion, thus the diffuser and the impeller are modeled with fully 360-deg passages

Effect of Reynolds Number and Surface Roughness on the Efficiency of Centrifugal Pumps

Abstract: A procedure has been developed to predict the effects of roughness and Reynolds number on the change in efficiency from a model or baseline to a prototype pump (efficiency scaling). The analysis of individual losses takes into account different roughnesses of impeller, diffuser/volute, impeller side disks, and casing walls in the impeller side rooms. The method also allows to predict the effect of roughness and Reynolds number on the hydraulic efficiency. The calculations are based on physical models but the weighting of impeller versus diffuser/volute roughness and the fraction of scalable losses within impeller and diffuser/volute are determined empirically from the analysis of tests with industrial pumps. The procedure includes all flow regimes from laminar to turbulent and from hydraulically smooth to fully rough

Impeller and a pressure support system and method using such a method

Abstract: An impeller, a pressure generator using such an impeller, and a pressure support system and method using such a pressure generator to deliver a flow of breathing gas to a patient is disclosed. The impeller enables a pressure of a flow of breathing gas delivered by a pressure support system to a patient to remain substantially constant despite variations of the output flow rate. The impeller includes a plurality of impeller blades disposed on a face of the impeller body with an inlet area between each pair of adjacent blades being substantially equal a corresponding outlet area for each pair of adjacent blades.

Counterrotating axial blower

Abstract: A counterrotating axial blower capable of providing larger air volume and higher static pressure than conventionally possible. The blower comprises a first single unit axial blower (1) and a second single axial blower (3). The first single axial blower (1) has a first case (5), a first impeller (7), and webs for fixing a first motor to the case (5). The second single axial blower (3) has a second case, a second impeller, and webs for fixing a second motor to the second case. The first case and the second case are connected to form a housing (59). The webs of the first single unit axial blower (1) and the webs of the second single unit axial blower (3) are combined to structure stationary blades arranged in the housing (59). The number of forward blades (28) provided on the first impeller (7) is five, the number of the stationary blades is three, and the number of backward blades (51) provided on a second impeller (35) is four.

Active feed paintball loader with flexible impeller

Abstract: A paintball loader has a motor-driven impeller with a plurality of resilient arms that engage and move paintballs in the loader housing The resilient arms preferably are spaced to accommodate paintballs therebetween The arms are sufficiently flexible to yield so as not to rupture the paintball shells

Effects of Volute Design and Number of Impeller Blades on Lateral Impeller Forces and Hydraulic Performance

Abstract: A comparison is made between the characteristics of the measured lateral impeller forces and the hydraulic performances of a four- and a five-vane impeller, each operating in a spiral volute, a concentric volute, and a double volute. The pump's rotor was supported in magnetic bearings. In addition to supporting and controlling the rotor motion, the magnetic bearings also served as active load cells and were used to measure the impeller forces acting on the pump's rotor. The lateral impeller force characteristics, as a function of a normalized flow coefficient, were virtually identical in the four- and five-vane impellers in each respective volute type. The measured impeller forces for each volute type were compared with correlations in the literature. The measured forces from the double volute configurations agreed with the forces from a correlation model over the full flow range. Single volute configurations compared well with the predictions of a published correlation at high flow rates, ϕ/ϕn>0.5. Concentric volute configurations compared well with a published correlation at low flow rates, ϕ/ϕn<0.4. The head-versus-flow characteristics of the four-vane impeller in each volute type were stable over a greater flow range than the corresponding characteristics of the five-vane impeller. At higher flow rates in the stable region of the head's characteristic curves near the best efficiency point, the five-vane impeller produced higher head than did the four-vane impeller in each volute type.

Air-applying device having a case with an air inlet port, a cooling unit having the air-applying device, and an electronic apparatus having the air-applying device

Abstract: An air-applying device has an impeller having a center of rotation, and a case which contains the impeller. The case includes a first edge defining an inlet port of air which exposes the center of rotation, a second edge defining an outlet port of air, and a high-pressure region which presents upon operational rotation of said impeller. The high-pressure region is located within the case along a peripheral portion of the impeller. A distance between the center of rotation of the impeller and the first edge is shorter in the direction from the center of rotation to a center of the high-pressure region than from the center of rotation to region other than the high-pressure region.

Optimizing rotary impact collectors

Abstract: The present invention relates to optimizing the configuration of rotary impact collectors and devices in which such rotary impact collectors are employed. Rotary impact collectors are formed out of base plate upon which a plurality of vanes are mounted. One aspect of the present invention is a combined impact collector and fan in which the ratio of vane height to impeller diameter is in the range of about 0.01 to about 0.2. Preferably, the vanes are evenly spaced around the impeller so as to present a balanced load to the motor. Other performance enhancing elements include the use of truncated vanes, configurations optimized for injection molding fabrication, controlling the orientation of the vanes to reduce the formation of vortex forces, and enhancements configured to increase the ability to collected particles rinsed off such impellers.

Discrete passage diffuser

Abstract: A centrifugal compressor (10) includes an impeller (12) and a diffuser (14). The impeller (12) has an inner integral hub (22) with vanes (24) thereon, is adapted to rotate within an outer shroud (16) about a central longitudinal axis (18), and has a defined hub-to-shroud distribution of fluid exit angles. The diffuser (14), downstream from the impeller (12), comprises a plurality of circumferentially spaced discrete passages (34) at least partially defining fluid paths through the diffuser, and angled such that adjacent discrete passages (34) intersect each other to form an annular semi-vaneless diffuser inlet space (30). The discrete passages (34) downstream of the semi-vaneless space (30) each have an inlet (31) therefrom and an outlet (33) with a greater cross-sectional area than the inlet (31). The intersection of the annular semi-vaneless space (30) and each discrete passage (34) defines a leading edge thereof. Each discrete passage (34) is defined by a wall bounding a cross-sectional area, the wall comprising at least a first substantially rectilinear portion (42) and a second opposed convexly curved portion (44); the first substantially rectilinear portion is adjacent the hub (22) of the impeller (12) and the second opposed convexly curved portion (44) is adjacent the outer shroud (16). The leading edge of each discrete diffuser passage (34) provides a close incidence angle match with the fluid exit angles of the impeller (12).