Rotordynamic Effects of the Shroud-to-Housing Leakage Flow in Centrifugal Pumps

1994 ◽  
Vol 116 (3) ◽  
pp. 558-563 ◽  
Author(s):  
E. A. Baskharone ◽  
A. S. Daniel ◽  
S. J. Hensel
Keyword(s):  
Experimental Data ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Secondary Flows ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Pump Impeller ◽  
Rotordynamic Coefficients ◽  
Clearance Face ◽  
Complex Flow Structure

The fluid/shroud interaction forces acting on a pump impeller that is precessing around the housing centerline, are computed and the rotordynamic coefficients deduced. The numerical procedure utilized is an upgraded version of a finite-element-based perturbation model, initially devised for simple see-through annular seals. The computational model accounts for the complex flow structure in the shroud-to-housing secondary flow passage, which includes a tight-clearance face seal. The model also facilitates the mutual interaction between the primary and secondary flows near the impeller inlet and discharge stations. The numerical results are compared to existing experimental data, as well as the results of a simpler and widely used numerical model. Sources of discrepancies between the numerical results are identified, and a comprehensive assessment made in light of the experimental data.

Pressure Fluctuations Reduction in Centrifugal Pumps: Influence of Impeller Geometry and Radial Gap

2009 ◽  
Author(s):  
Moise´s Solis ◽  
Farid Bakir ◽  
Sofiane Khelladi
Keyword(s):  
Pressure Fluctuations ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Operating Conditions ◽  
Navier Stokes ◽  
Centrifugal Pumps ◽  
Virtual Sensors ◽  
Wall Functions ◽  
Blade Passage ◽  
Radial Gap

A numerical investigation was carried out in a volute type centrifugal pump to study the influence of splitter blades and radial gap and decrease the pressure fluctuations levels at the blade passage frequency for the same operating conditions. In this kind of turbomachinery, the strong interaction between the flow leaving the impeller and entering the volute casing generate pulsating pressures which propagate toward the inlet and the discharge of the pump. They are mainly associated to the blade passage frequency presenting high amplitudes near the tongue and at impeller discharge. Three configurations were considered in the numerical tests, the first hydraulic is the reference geometry to be optimized and the other two are the versions modified for decrease pressure fluctuations. The geometrical changes concern: adding splitter blades to the original impeller and increasing the radial gap between the splitter impeller and the volute tongue. The simulations for all configurations were performed at the same flow rate. It was necessary to decrease the rotational speed of the optimized configurations to reach the same operating point. The pressure signals were collected by virtual sensors placed at several locations of the pump mainly at the impeller-volute interface plus at inlet and at outlet ducts. Then they were treated and processed obtaining the frequency spectrum by means of the Fast Fourier Transform, so the numerical results were compared and discussed. A commercial CFD code has been used to predict the pulsating pressures and the Unsteady Reynolds Averaged Navier-Stokes (URANS) approach has been applied to solve the unsteady, incompressible and turbulent flow. The k-ω SST model was used to take into account the turbulence effects and the standard wall functions were applied. The numerical procedure employed for the unsteady simulations was determined after an investigation of the influence of boundary conditions on the pressure signals specially at the outlet duct, showing that the condition of outflow does not have influence on the numerical results.

Experimental and Numerical Study of Cavitation in Centrifugal Pumps

2010 ◽  
Author(s):  
Erfan Niazi ◽  
M. J. Mahjoob ◽  
Ardeshir Bangian
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Mass Flow Rate ◽  
Computer Simulations ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Numerical Results ◽  
Centrifugal Pumps ◽  
Cavitation Threshold

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

Numerical Solution of Inviscid Two-Dimensional Transonic Flow Through a Cascade

1987 ◽  
Vol 109 (1) ◽  
pp. 108-113
Author(s):  
J. Forˇt ◽  
K. Kozel
Keyword(s):  
Experimental Data ◽  
Weak Solution ◽  
Numerical Solution ◽  
Transonic Flow ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Two Dimensional ◽  
System Of Difference Equations ◽  
Flow Through ◽  
Turbine Cascades

The paper presents a method of numerical solution of transonic potential flow through plane cascades with subsonic inlet flow. The problem is formulated as a weak solution with combined Dirichlet’s and Neumann’s boundary conditions. The numerical procedure uses Jameson’s rotated difference scheme and the SLOR technique to solve a system of difference equations. Numerical results of transonic flow are compared with experimental data and with other numerical results for both compressor and turbine cascades near choke conditions.

scholarly journals Error Quantification of Nusselt Number Analysis in Miniature Heat Sinks: Verification and Validation Assessment

2021 ◽  
Author(s):  
Mahyar Pourghasemi ◽  
Nima Fathi
Keyword(s):  
Experimental Data ◽  
Water Flow ◽  
Heat Sink ◽  
Numerical Procedure ◽  
Numerical Results ◽  
Heat Sinks ◽  
Uniform Heat Flux ◽  
Microchannel Heat Sink ◽  
Order Of Accuracy ◽  
Nusselt Numbers

Abstract Solution verification is performed to quantify the numerical uncertainty of Nusselt numbers in micro-scale heat sinks obtained from 3-D numerical simulations. A numerical procedure is first developed to calculate local and average Nusselt numbers along 4 different miniature heat sinks. Validation process is performed by comparing the obtained numerical results experimental data. Fairly good agreement between numerical results and experimental data confirms the reliability and accuracy of the proposed numerical procedure. The observed order of accuracy for water flow in a micro-tube with constant uniform heat flux is 1.81 while the observed order of accuracy for conjugate heat transfer of water flow within a microchannel heat sink is estimated as 1.2. The numerical uncertainty for local Nusselt numbers within the investigated microchannel heat sink is estimated to be 0.13.

Numerical Investigation of Back Vane Design and Its Impact on Pump Performance

2017 ◽  
Vol 139 (12) ◽  
Author(s):  
Farzam Mortazavi ◽  
Alireza Riasi ◽  
Ahmad Nourbakhsh
Keyword(s):  
Flow Characteristics ◽  
Outer Radius ◽  
Design Parameters ◽  
Centrifugal Pumps ◽  
Complex Flow ◽  
Axial Thrust ◽  
Axial Forces ◽  
New Findings ◽  
Pump Head ◽  
Complex Flow Structure

Adding back vanes to the rear shroud of centrifugal pumps is sometimes practiced in order to alleviate large axial forces. Effective design and flow characteristics of back vanes remain obscure due to lack of knowledge associated with experimental complexities in study of this area. In this study, various design parameters of the conventional noncurved rectangular back vanes are evaluated using computational fluid dynamics (CFD). Furthermore, the complex flow structure at the rear chamber of these pumps is illustrated and discussed with the advantage of CFD which is a highly costly and taxing job if one chooses to capture it using experimental methods. Effect of back vanes outer radius, width, clearance, thickness, vane angle, and number of vanes on pump characteristics and axial thrust has been investigated. New findings of this study show that back vanes are capable of canceling the axial thrust in a large range of flow rates without a penalty to the machine efficiency, provided that suitable design parameters are selected. In addition, the best efficiency point (BEP) will not be affected by usage of back vanes. The rear chamber’s flow pattern suggest that back vanes have a repumping effect causing increased pump head at longer back vane configurations.

Secondary Flows in a Transonic Cascade: Comparison Between Experimental and Numerical Results

1989 ◽  
Vol 111 (4) ◽  
pp. 369-377 ◽  
Author(s):  
F. Bassi ◽  
C. Osnaghi ◽  
A. Perdichizzi ◽  
M. Savini
Keyword(s):  
Experimental Data ◽  
Secondary Flow ◽  
Three Dimensional ◽  
Numerical Results ◽  
Secondary Flows ◽  
Streamwise Vorticity ◽  
Flow Angle ◽  
Flow Phenomena ◽  
Contour Plots ◽  
Flow Vortex

The paper presents a comparison between numerical results and experimental data about the secondary flow development in a linear transonic turbine cascade. Computations are carried out by using a three-dimensional inviscid Euler code, based on a Runge-Kutta explicit finite volume method. The experimental inlet total pressure distribution is imposed as inlet boundary condition to simulate the incoming endwall boundary layer. The comparison is made in four planes downstream of the cascade where detailed experimental data obtained in a transonic wind tunnel are available. For each of these planes secondary velocities and streamwise vorticity contour plots are presented and discussed. Moreover pitchwise mass averaged flow angle distributions showing overturning and underturning regions are shown. The comparison shows that an Euler code can predict the essential features of secondary flow phenomena like passage vortex location and intensity but a certain disagreement is found in the overturning and underturning angles evaluation. Numerical results also allow for the investigation of the development of secondary flows inside the blade channel. The investigation is carried out for three different Mach numbers: M2is = 0.5, 1.02, 1.38, in order to show the influence of compressibility on the flow vortex structure.

Modelling of catalyst pellet deactivation

1985 ◽  
Vol 50 (11) ◽  
pp. 2381-2395
Author(s):  
Alena Brunovská ◽  
Ján Buriánek ◽  
Ján Ilavský ◽  
Ján Valtýni
Keyword(s):  
Experimental Data ◽  
Numerical Results ◽  
Benzene Hydrogenation ◽  
Alumina Catalyst ◽  
Temperature Changes ◽  
Catalyst Pellet ◽  
Model Equations ◽  
Catalytic Poison

The diffusion and the shell progressive models of deactivation caused by irreversible chemisorption of a catalytic poison are presented for a single catalyst pellet. The method for solution of the model equations is proposed. The numerical results are compared with experimental data obtained by measuring concentration and temperature changes due to thiophene poisoning in benzene hydrogenation over a nickel-alumina catalyst.

scholarly journals Low-cost Solutions for Velocimetry in Rotating and Opaque Fluid Experiments using Ultrasonic Time of Flight

2021 ◽  
Author(s):  
Fabian Burmann ◽  
Jerome Noir ◽  
Stefan Beetschen ◽  
Andrew Jackson
Keyword(s):  
Acoustic Waves ◽  
Flow Measurement ◽  
Low Cost ◽  
Time Of Flight ◽  
Zonal Flow ◽  
Gravitational Acceleration ◽  
Complex Flow ◽  
Ultrasonic Time ◽  
Theoretical Predictions ◽  
Complex Flow Structure

AbstractMany common techniques for flow measurement, such as Particle Image Velocimetry (PIV) or Ultrasonic Doppler Velocimetry (UDV), rely on the presence of reflectors in the fluid. These methods fail to operate when e.g centrifugal or gravitational acceleration leads to a rarefaction of scatterers in the fluid, as for instance in rapidly rotating experiments. In this article we present two low-cost implementations for flow measurement based on the transit time (or Time of Flight) of acoustic waves, that do not require the presence of scatterers in the fluid. We compare our two implementations against UDV in a well controlled experiment with a simple oscillating flow and show we can achieve measurements in the sub-centimeter per second velocity range with an accuracy of $\sim 5-10\%$ ∼ 5 − 10 % . We also perform measurements in a rotating experiment with a complex flow structure from which we extract the mean zonal flow, which is in good agreement with theoretical predictions.

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