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"Sistemas de análises químicas em fluxo explorando multi-impulsão e detecção espectrofotométrica: aplicação a formulações farmacêuticas e a extratos de solos"; Multi-pumping flow systems with spectrophotometric detection: application to analysis of pharmaceuticals and soil extracts

Dias, Ana Cristi Basile
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 21/03/2006 PT
Relevância na Pesquisa
36.05%
Os sistemas de análises em fluxo com multi-impulsão (MP) empregam bombas solenóides como unidade propulsora de fluidos, as quais proporcionam um fluxo pulsante. Esta característica foi avaliada em função do funcionamento, operação e desempenho do sistema, das condições de mistura entre as soluções envolvidas e da dispersão da solução inserida. A avaliação geral dos sistemas MP envolveu estudos de precisão e exatidão volumétrica dos pulsos, bem como da robustez da unidade propulsora, os quais envolveram medidas gravimétricas. Ainda, dispersão envolvendo uma solução colorida como amostra foi espectrofotometricamente avaliada. Os resultados foram corroborados por meio de aplicações analíticas. Limitações quanto ao uso de bombas com maiores volumes de pulso (> 25 l) foram observadas a elevadas frequências de pulsação (> 4,0 Hz). Os volumes experimentalmente determinados concordaram com os valores esperados (erro relativo < 2,0 %). A dispersão da amostra foi menor relativamente àquela inerente a fluxo constante (sistema explorando multi-comutação, MC). O fluxo pulsante promoveu melhoria no desenvolvimento reacional devido principalmente à agitação dos elementos de fluido vizinhos. Este aspecto foi importante com relação à determinação espectrofotométrica de bromexina em fármacos. O método se fundamentou no acoplamento eletrofílico da bromexina com 3-metil-2-benzotiazolinona hidrazona (MBTH)...

Transient flow of the oil-refrigerant mixture through the radial clearance in rolling piston compressors

Gasche, José L.; Ferreira, Rogério T. S.; Prata, Álvaro T.
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Artigo de Revista Científica Formato: 119-127
ENG
Relevância na Pesquisa
36.28%
Unsteady flow of oil and refrigerant gas through radial clearance in rolling piston compressors has been modeled as a heterogeneous mixture, where the properties are determined from the species conservation transport equation coupled with momentum and energy equations. Time variations of pressure, tangential velocity of the rolling piston and radial clearance due to pump setting have been included in the mixture flow model. Those variables have been obtained by modeling the compression process, rolling piston dynamics and by using geometric characteristics of the pump, respectively. An important conclusion concerning this work is the large variation of refrigerant concentration in the oil-filled radial clearance during the compression cycle. That is particularly true for large values of mass flow rates, and for those cases the flow mixture cannot be considered as having uniform concentration. In presence of low mass flow rates homogeneous flow prevail and the mixture tend to have a uniform concentration. In general, it was observed that for calculating the refrigerant mass flow rate using the difference in refrigerant concentration between compression and suction chambers, a time average value for the gas concentration should be used at the clearance inlet.

Modelo de deslizamento para escoamento gás-líquido em bomba centrífuga submersa operando com líquido de baixa viscosidade; A drift-flux model for gas-liquid flow in electrical submersible pump operating with low viscous liquid

Jorge Luiz Biazussi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 06/06/2014 PT
Relevância na Pesquisa
36.33%
A bomba centrífuga submersa (BCS) é uma bomba de múltiplos estágios que tem recebido muita atenção nos últimos anos, devido à sua importância para a elevação artificial de petróleo em altas vazões. Como uma parte do sistema de Elevação Artificial, a BCS é geralmente instalada no interior do poço, a fim de aumentar a vazão ou até mesmo viabilizar a produção. A presença de gás livre no fluido na entrada da bomba provoca uma diminuição do ganho de pressão fornecido pela BCS e pode conduzir a instabilidades na curva de ganho de pressão versus vazão. O objetivo deste trabalho é desenvolver e avaliar o desempenho de um modelo de deslizamento para representar o ganho de pressão em uma ampla faixa de vazão de líquido de uma BCS. Para este propósito foram realizados testes experimentais em laboratório para três BCS diferentes que operam com misturas ar - água. Especificamente, o ganho de pressão e a potência de eixo foram medidos em diferentes vazões de líquido, de gás, de pressões de entrada e rotação. Os resultados dos testes de água monofásicos foram interpretados por ajuste dos dados com um modelo de correlação genérico para o ganho de pressão e potência, tentando descrever todos os fenômenos físicos envolvidos no escoamento nos canais rotativos. Os resultados dos testes bifásicos foram discutidos em termos dos efeitos da fração de vazio...

Optimization of a Hybrid Magnetic Bearing for a Magnetically Levitated Blood Pump via 3-D FEA

Cheng, Shanbao; Olles, Mark W.; Burger, Aaron F.; Day, Steven W.
Fonte: PubMed Publicador: PubMed
Tipo: Artigo de Revista Científica
Publicado em /10/2011 EN
Relevância na Pesquisa
26.2%
In order to improve the performance of a magnetically levitated (maglev) axial flow blood pump, three-dimensional (3-D) finite element analysis (FEA) was used to optimize the design of a hybrid magnetic bearing (HMB). Radial, axial, and current stiffness of multiple design variations of the HMB were calculated using a 3-D FEA package and verified by experimental results. As compared with the original design, the optimized HMB had twice the axial stiffness with the resulting increase of negative radial stiffness partially compensated for by increased current stiffness. Accordingly, the performance of the maglev axial flow blood pump with the optimized HMBs was improved: the maximum pump speed was increased from 6000 rpm to 9000 rpm (50%). The radial, axial and current stiffness of the HMB was found to be linear at nominal operational position from both 3-D FEA and empirical measurements. Stiffness values determined by FEA and empirical measurements agreed well with one another. The magnetic flux density distribution and flux loop of the HMB were also visualized via 3-D FEA which confirms the designers’ initial assumption about the function of this HMB.

NUMERICAL AND EXPERIMENTAL INVESTIGATIONS IN A VANED DIFFUSER OF SHF IMPELLER: FLUID LEAKAGE EFFECT

BAYEUL-LAINE, Annie-Claude; DUPONT, Patrick; CAVAZZINI, Giovanna; CHERDIEU, Patrick; BOIS, Gérard; DAZIN, Antoine; ROUSSETTE, Olivier
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
46.21%
The paper presents the analysis of the performance and the internal flow behaviour in the vaned diffuser of a radial flow pump using PIV technique, pressure probe traverses and numerical simulations. PIV measurements have been performed at different heights inside one diffuser channel passage for a given speed of rotation and various flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly, to cover the space between the leading edge of the impeller and the diffuser throat and secondly, to get a rather good evaluation of phase averaged velocity charts and “fluctuating rates “. Probe traverses have also been performed using a 3 holes pressure probe from hub to shroud diffuser width at different radial locations in between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 7.02.011 (at LML), ii-CFX 10.0 (at University of Padova). Fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for two flow rates. In this respect...

INVESTIGATIONS IN A VANED DIFFUSER OF SHF IMPELLER

BAYEUL-LAINE, Annie-Claude; DUPONT, Patrick; CAVAZZINI, Giovanna; DAZIN, Antoine; CHERDIEU, Patrick; BOIS, Gérard; ROUSSETTE, Olivier
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
Relevância na Pesquisa
46.3%
The paper presents the numerical and experimental analysis of performance and internal flow behaviour in the vaned diffuser of a radial flow pump (Fig. 1) using PIV technique (Fig. 2), pressure probe traverses and numerical simulations. PIV measurements have been performed at different heights inside one diffuser channel passage for a given speed of rotation and various mass flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly, to cover the space between the leading edge of the impeller and the diffuser throat and secondly, to get a rather good evaluation of phase averaged velocity charts and “fluctuating rates “. Hub to shroud directional probe traverses (Fig. 3) have also been performed using a 3 holes pressure probe along the diffuser width at different radial locations between the two diffuser geometrical throats. The numerical simulations were realized with the two commercial codes: i-Star CCM+ 7.02.011 (at LML), ii-CFX 10.0 (at University of Padova). Fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for different mass flow rates. In this respect...

UNSTEADY VELOCITY PIV MEASUREMENTS AND 3D NUMERICAL CALCULATION COMPATISONS INSIDE THE IMPELLER OF A RADIAL PUMP MODEL

CAVAZZINI, Giovanna; DUPONT, Patrick; DAZIN, Antoine; PAVESI, Giorgio; BAYEUL-LAINE, Annie-Claude; BOIS, Gérard
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
36.14%
PIV measurements were performed at mid hub section inside the impeller of a vaned diffuser pump model working with air. Several previous papers have already presented part of impeller flow characteristics mainly for vaneless diffuser and near nominal mass flow rate. This paper concerns the pump configuration where the diffuser blades interacted with the impeller flow. Each PIV measuring plane was related to one particular impeller blade to blade channel and analyzed according to different relative positions of the vaned diffuser. A fully unsteady calculation of the whole pump has been performed and comparisons between numerical and experimental results are presented and discussed for four different mass flow rates. The present analysis is restricted to the outlet section of the impeller blade to blade passage for one particular impeller blade position relative to the diffuser.

Data reduction problems using a 3 holes directional pressure probe to investigate mean flow characteristics in the vaneless gap between impeller and diffuser radial pump

CHERDIEU, Patrick; DUPONT, Patrick; BAYEUL-LAINE, Annie-Claude; DAZIN, Antoine; BOIS, Gérard
Fonte: 6 th international conference on pimps and fans with compressors and wind turbines Publicador: 6 th international conference on pimps and fans with compressors and wind turbines
EN
Relevância na Pesquisa
46.07%
Among several different measurement techniques that have been already performed and presented in a radial impeller pump model including PIV, a directional pressure probe has been used to obtain mean velocity field and stagnation pressure between impeller outlet and the inlet vaned diffuser sections. These measurements are supposed to get more information not only about global pump head coefficient including vaned diffuser ones but also about impeller performances itself. Pressure probe information is affected by rotor-stator interactions and impeller rotation, and this paper presents a way to explain and correct pressure probe indications in order to achieve a better evaluation of overall impeller mean performances. The use of unsteady RANS calculation results is found to be a useful way to perform better data reduction analysis for this purpose

Comparisons Between Numerical Calculations and Measurements in the Vaned Diffusor of SHF Impeller

BAYEUL-LAINE, Annie-Claude; DUPONT, Patrick; CAVAZZINI, Giovanna; CHERDIEU, Patrick; DAZIN, Antoine; BOIS, Gérard; ROUSSETTE, Olivier
Fonte: journal of drainage and irrigation machinery engineering Publicador: journal of drainage and irrigation machinery engineering
EN
Relevância na Pesquisa
66.3%
The authors wish to thank Region Nord-Pas de Calais and CNRS for their financial support in the frame of the CISIT program; The paper presents analysis of the performance and the internal flow behaviour in the vaned diffusor of a radial flow pump using PIV (Particle Image Velocimetry) and pressure probe traverses. PIV measurements have already been performed at mid height inside one diffusor channel passage for a given speed of rotation and various mass flow rates. These results have been already presented in several previous communications. New experiments have been performed using a 3 holes pressure probe traverses from hub to shroud diffusor width at different radial locations between the two diffusor geometrical throats. Numerical simulations are also realized with the commercial codes Star CCM+ 7.02.011 and CFX. Frozen rotor and fully unsteady calculations of the whole pump have been performed. Comparisons between numerical results, previous experimental PIV results and new probe traverses one’s are presented and discussed for one mass flow rate. In this respect, a first attempt to take into account fluid leakages between the rotating and fixed part of the pump has been checked since it may affect the real flow structure inside the diffuser

FLUID LEAKAGE EFFECT ON ANALYSIS OF A VANED DIFFUSER OF SHF

BAYEUL-LAINE, Annie-Claude; DUPONT, Patrick; MICCOLI, Lucio; CAVAZZINI, Giovanna; DAZIN, Antoine; PAVESI, Giorgio; BOIS, Gérard
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
46.14%
The paper presents the results of numerical analysis on the local and global internal flow behaviour at the inlet of the vaned diffuser of a radial flow pump model, taking into account the effect of fluid leakages for various flow rates and a given rotation of speed. For each flow rate, numerical calculations were performed both with two different boundary conditions: - Without any leakage effects. - With calculated leakage effects The numerical simulations were realized with the two commercial codes: i-Star CCM+ 8.02.011 (at LML), ii-CFX 10.0 (at University of Padova). RANS unsteady calculations, with a k- RNG model were performed with Star CCM+. Fully unsteady calculations of the whole pump were done with CFX with DES turbulentmethod (Cavazzini [1]). For each flow rate, different angular positions of the impeller are considered. First part of the paper shows global comparisons between numerical and experimental results already presented in ref [2-3], for which the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model were found to be interesting to be analysed. Second part is devoted to the local comparisons of flow structures at the inlet section of the diffuser, without and with leakages only with Star CCM+.

Comparaisons between numerical calculations and measurements in the vaned diffusor of SHF impeller

BAYEUL-LAINE, Annie-Claude; DUPONT, Patrick; CHERDIEU, Patrick; DAZIN, Antoine; BOIS, Gérard; ROUSSETTE, Olivier
Fonte: Arts et Métiers ParisTech Publicador: Arts et Métiers ParisTech
EN
Relevância na Pesquisa
36.18%
The paper presents analysis of the performance and the internal flow behaviour in the vaned diffusor of a radial flow pump using PIV technique and pressure probe traverses. PIV measurements have been performed at mid height inside one diffusor channel passage for a given speed of rotation and various mass flow rates. For each operating condition, PIV measurements have been made for different angular positions of the impeller. For each angular position, instantaneous velocities charts have been obtained on two simultaneous views, which allows, firstly ,to cover the space between the leading edge and the diffusor throat and secondly, to get a rather good evaluation of phase averaged velocity charts and “fluctuating rates “. Probe traverses have been performed using a 3 holes pressure probe from hub to shroud diffusor width at different radial locations in between the two diffusor geometrical throats. The numerical simulations were realized with the commercial codes: i-Star CCM+ 7.02.011, ii-CFX. Frozen rotor and fully unsteady calculations of the whole pump were performed. Comparisons between numerical and experimental results are presented and discussed for one mass flow rate. In this respect, the effects of fluid leakage due to the gap between the rotating and fixed part of the pump model are analysed and discussed.

Experimental and Numerical Investigation of Unforced unsteadiness in a Vaneless Radial Diffuser

PAVESI, Giorgio; DAZIN, Antoine; CAVAZZINI, Giovanna; CAIGNAERT, Guy; BOIS, Gérard; ARDIZZON, Guido
Fonte: EUROTURBO Publicador: EUROTURBO
EN
Relevância na Pesquisa
56.2%
The paper reports combined experimental and numerical investigations of unforced un- steadiness in a vaneless radial diffuser. Experimental data were obtained within the diffuser using stereoscopic time resolved Particle Image Velocimetry (PIV) recording three velocity components in a plane (2D/3C), coupled with unsteady pressure transducers. To characterize the inception and the evolution of the unsteady phenomena, spectral analyses of the pressure signals were carried out both in frequency and time-frequency domains and the PIV results were post processed by an original averaging method. Two partial flow rates were investigated in detail in this paper. A single unforced unsteadiness was identified for the lowest flow rate, whereas, two competitive intermittent modes were recognized for the higher mass flow. Numerical analyses were carried out on the same pump by the commercial code CFX. All the computations were performed using the unsteady transient model and the turbulence was modelled by the Scale-Adaptive Simulation (SAS) model. Numerical pressure signals were compared with the experimental data to verify the development of the same pressure fluctua- tions.

Transient behavior of a radial vaneless diffuser

DAZIN, Antoine; DUPONT, Patrick; CAIGNAERT, Guy; BOIS, Gérard
Fonte: ASME Publicador: ASME
EN_US
Relevância na Pesquisa
76.3%
The paper refers to the behavior of a radial flow pump vaneless diffuser during a starting period. Results obtained with a 1D numerical model are compared with some new experimental data which have been obtained using 2D/3C High repetition rate PIV within the diffuser coupled with unsteady pressure measurements. These tests have been performed on a test rig with a radial impeller matched with a vaneless diffuser. They have been made in air, on a test rig well adapted for studies on interactions between impeller and diffuser, as well as for the use of optical methods and especially Particle Image Velocimetry (PIV) as there is no volute downstream of the diffuser. The present study refers to new experiments combining pressure measurements and 2D/3C High Speed PIV at partial flow rates within a vaneless diffuser with a large outlet radius. Four Brüel & Kjaer condenser microphones are used for the unsteady pressure measurements. They were flush mounted on the shroud side of the diffuser wall and on the suction pipe of the pump. The sampling frequency was 2048 Hz. For PIV measurements, the laser sheet was generated by a Darwin PIV ND:YLF Laser at three heights within the diffuser. PIV snapshots have been recorded by two identical CMOS cameras. A home made software has been used for the images treatment. The results consist in fields of 80 x 120 mm2 and 81 x 125 velocity vectors with a temporal resolution of 250 velocity maps per second. For each flow rate and each laser sheet height in the diffuser...

Internal Flows and Force Matrices in Axial Flow Inducers

Bhattacharyya, Abhijit
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em //1994
Relevância na Pesquisa
35.98%
Axial flow pump runners known as inducers are subject to complex internal flows and fluid-induced lateral and rotordynamic forces. The internal flows in inducers are three dimensional and are characterized by complicated secondary flows. The current research investigates the boundary layer flows on the blades, hub and housing of unshrouded and shrouded axial flow inducers using flow visualization techniques. Rotordynamic and lateral force data on unshrouded inducers were also obtained under varying conditions of flow and whirl. Studies on the internal flows showed that the blade boundary layer flow had strong radial components at off-design conditions. The flow remains attached to the blade surface of unshrouded inducers at all flow coefficients tested. The origin of the upstream swirling backflow was found to be at the discharge plane of the inducer. In addition, flow reversal was observed at the suction side blade tip near the leading edge in a shrouded inducer. Re-entry of the hub boundary layer flow (a downstream backflow) into the blade passage area was observed at flow coefficients below design. For unshrouded inducers the radially outward flow near the blade tip mixed with the tip clearance leakage flow to form the upstream backflow. These observations provide a better understanding of the internal flows and the occurrence of upstream backflows in inducers. The rotordynamic forces acting on an inducer due to an imposed whirl motion was also investigated. It was found that the rotordynamic force data at various whirl frequency ratios does not allow a normal quadratic fit; consequently the conventional inertial...

Effect of the Volute on Performance of a Centrifugal-Pump Impeller

Bowerman, R. D.; Acosta, A. J.
Fonte: American Society of Mechanical Engineers Publicador: American Society of Mechanical Engineers
Tipo: Article; PeerReviewed Formato: application/pdf
Publicado em /01/1957
Relevância na Pesquisa
35.93%
An experimental study of volute influence on radial flow-impeller performance was conducted by operating a single impeller with three different sets of volute vanes. In each case, over-all performance was measured and an internal-flow study within the volute was made. The results show that at their respective design flow rates the influence of the volutes is least and the deviation of performance from the free-impeller operation is small. At off-design flow rates there are major changes in the impeller performance resulting from the presence of the volutes. Large real fluid effects, coupled with a nonuniform velocity pattern at the impeller exit, result in a flow through the volute that does not resemble a potential flow. Even so, the fluid losses through the volute are comparatively small.

Evaluation of a Two Dimensional Centrifugal Pump Impeller

Beveridge, John H.; Morelli, Dino A.
Fonte: Instituto de Tecnologia da Califórnia Publicador: Instituto de Tecnologia da Califórnia
Tipo: Conference or Workshop Item; NonPeerReviewed Formato: application/pdf
Publicado em //1950
Relevância na Pesquisa
45.95%
The two-dimensional radial flow pump impeller has significant advantages for the study of the transfer and diffusion of energy. It is well adapted to experimental investigation and permits accurate and economical design modifications. The present study was undertaken to evaluate the essential limitations of a special series of two-dimensional impellers by photographic and hydrodynamic techniques which are described in the present paper and elsewhere. The head-capacity characteristics, losses and efficiency, are discussed in the light of visual evidence available from high speed motion pictures of the relative and absolute flow. The dominant influence of the inlet angle on the impeller performance is demonstrated.

The Design of Axial Flow Pumps

Bowerman, R. D.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em /04/1956
Relevância na Pesquisa
36.05%
A design procedure for axial-flow pump impellers is presented that accounts for induced interference effects in the prediction of performance. Induced interference velocities at an impeller blade have been calculated using a three-dimensional model that includes the effects of the other blades and of the total downstream vorticity along the center line of the pump. The design method considers improvement of cavitation conditions by specifying the radial variation of the design parameters such that the pressure distributions on all radial sections are similar. An analysis of optimizing the impeller geometric parameters for cavitation conditions is presented to permit the initial choices of the quantities appearing in the design procedure. Experimental work on a two-bladed impeller has yielded results that give good support to all aspects of the design method.

Effect of the Volute on Performance of a Centrifugal Pump Impeller

Bowerman, R. D.
Fonte: California Institute of Technology Publicador: California Institute of Technology
Tipo: Report or Paper; PeerReviewed Formato: application/pdf
Publicado em /03/1955
Relevância na Pesquisa
35.95%
An experimental study of volute influence on radial flow impeller performance was conducted by operating a single impeller with three different sets of volute vanes. In each case, over-all performance was measured and internal flow study within the volute was made. The results show that at their respective design flow rates the influence of the volutes is least and the deviation of performance from the free impeller operation is small. At off-design flow rates there are major changes in the impeller performance due to the presence of the volutes. Large real fluid effects, coupled with a quite nonuniform velocity pattern at the impeller exit, result in a flow through the volute that does not resemble a potential flow. Even so, the fluid losses through the volute are comparatively small. It is also shown that at off-design conditions, the flow cannot be irrotational and therefore potential flow theories cannot be used in describing the flow or predicting performance.

The Acceleration of the Diffusion-Limited Pump-and-Treat Aquifer Remediation with Pulsed Pumping that Generates Deep Sweeps and Vortex Ejections in Dead-End Pores

Kahler, David Murray
Fonte: Universidade Duke Publicador: Universidade Duke
Tipo: Dissertação
Publicado em //2011
Relevância na Pesquisa
36.32%

Clean water is a critical natural resource. We do not have much available: only 2.5% of water on Earth is freshwater and of that only 31% is in liquid form. 96% of the liquid fresh water is groundwater. Unfortunately that resource is subject to contamination by hazardous materials accidentally or illicitly spilled, leaked, or deposited in or on the ground. Among the methods to remediate these disasters, pump-and-treat (P&T) is the most common. The vertical circulation well (VCW) is a P&T configuration with extraction and injection sites within the same well. It can be adapted to many remediation techniques and has been gaining popularity since the 1990s and is often a better alternative to conventional P&T. Conventional P&T and VCWs are typically run with steady flow.

The major bottleneck to steady flow remediation is that contaminants become trapped in dead-end pores. In an aquifer there are two types of pores: pass-through pores and dead-end pores. The flow in former completely sweeps through the pore space while the flow does not enter the later; however, the flow through the pass-through pore induces a vortex in the dead-end pore. Under steady flow the only mechanism for contaminants to escape the dead-end pores is molecular diffusion.

A similar problem is encountered in the removal of surfactants in the manufacture of semiconductor and the removal of oil residue build-up in small ducts. Manufacturers discovered that pulsed flow would accelerate the mass transfer between the cavities and grooves on these surfaces and the external flow. This was because the unsteady ramp-up in flow rate initiated a deep sweep of the cavities. The unsteady ramp-down in flow rate initiated a vortex ejection where the sequestered vortex is no longer constrained and protrudes from the cavity.

We hypothesized that just as pulsed flow improves cleaning of grooved surfaces in several manufacturing procedures...

3-D CFD analysis of flow in a mixed-flow pump diffuser

Zhao, Yi
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
EN_US
Relevância na Pesquisa
46.22%
The primary goal of the project was to gain insight into the flow pattern in a mixed flow pump diffuser by using FLUENT CFD code and k-e turbulence model, and improve the design of a diffuser for higher pump efficiency. The diffuser chosen in this thesis is used in a mixed flow multi-stage pump which collects the nearly radial flow (water) at impeller discharge and converts it to a nearly axial flow at the inlet of the following pump stage. A three-dimensional computational model was developed for three different diffuser designs labeled as Diffuser A, Diffuser B and Diffuser C. CFD results indicated that Diffuser C had better pressure recovery characteristics than both Diffuser A and Diffuser B. These results were confirmed by comparing with the experimental data for these diffusers provided by the pump manufacturer. The major conclusion resulting from the flow pattern study for Diffuser A, B and C is that the exit angle of the mean flow near the hub side of the diffuser has a strong effect on the diffuser performance. The greater the flow exit angle, the higher the degree of secondary flow formation which tends to reduce static pressure recovery. Based on that finding, several different diffuser geometries were modeled in an effort to reduce the exit flow angle. It can be concluded from this work that FLUENT CFD code can be used to model internal subsonic flows with a high degree of confidence. There was good correlation between model results and manufacturer's test data.