Scale Effects in a Mixed Flow Pump: Part 1

1986 ◽  
Vol 200 (3) ◽  
pp. 173-179
Author(s):  
V Ramarajan ◽  
S Soundranayagam
Keyword(s):  
Reynolds Number ◽  
Scale Effects ◽  
Reynolds Numbers ◽  
Centrifugal Pumps ◽  
Mixed Flow ◽  
Operating Range ◽  
Experimental Range ◽  
Specific Speed ◽  
Flow Pump

The variation of efficiency and losses over a range of Reynolds numbers has been measured for a mixed flow pump of specific speed 118 r/min for a number of points covering its operating range. The losses have been separated into those of the impeller and volute. The efficiency is seen to show a steady rise throughout the experimental range in comparison with published results for centrifugal pumps which flatten out at higher Reynolds numbers. A distinct hump is seen in many of the efficiency variation curves as well as in the variation of head with Reynolds number. The hump in the efficiency curves seems to be connected with transition to a roughness dominated regime while that in the head variation appears to be connected to changes in circulation. They both occur at different Reynolds numbers and are unconnected with each other. The frictional component of the losses in the volute is small and the losses there seem to be largely independent of Reynolds number.

Scale Effects in a Mixed Flow Pump: Part 2

1986 ◽  
Vol 200 (3) ◽  
pp. 180-186 ◽  
Author(s):  
S Soundranayagam ◽  
V Ramarajan
Keyword(s):  
Reynolds Number ◽  
Scale Effects ◽  
A Priori ◽  
Scale Up ◽  
Practical Interest ◽  
Reynolds Numbers ◽  
Mixed Flow ◽  
Below The Knee ◽  
Number Curve ◽  
Flow Pump

The measured variation of losses in a mixed flow pump have been analysed to determine the fraction V of the losses that are dependent on Reynolds number and the exponent n that characterizes that dependence. The variation of the Reynolds number dependent fraction has been obtained for different operating points on the pump characteristic. It is shown that the experimentally determined points are fitted very well with several combinations of V and n within the experimental range and it is strongly suggested that the exponent n be chosen on the basis of a-priori theoretical grounds. The importance of specifying a model reference Reynolds number is pointed out. The present formulae used for efficiency scale-up are most useful in the region of rapidly changing efficiency below the knee in the efficiency–Reynolds number curve. They are not applicable in the region of most practical interest in Reynolds numbers above the knee where prototype pumps operate.

Performance of a Mixed Flow Pump with Varying Tip Clearance: Part 2

1996 ◽  
Vol 210 (4) ◽  
pp. 319-327 ◽  
Author(s):  
S Soundranayagam ◽  
T K Saha
Keyword(s):  
Close Agreement ◽  
Tip Clearance ◽  
Pump Efficiency ◽  
Centrifugal Pumps ◽  
Mixed Flow ◽  
Loss Distribution ◽  
Specific Speed ◽  
Flow Pump ◽  
Relative Flow

Measurements in a mixed flow pump of non-dimensional specific speed k = 1.89 [ NS = 100 r/min (metric)] are analysed to give loss distribution and local hydraulic efficiencies at different flowrates and values of tip clearance. Fairly close agreement is obtained between the relative flow angles leaving the blading as predicted by simple deviation and slip models and derived from the measurements. The head developed is broken up into two parts: that contributed by Coriolis action and that associated with blade circulation. It is suggested that lift coefficients based on blade circulation are of limited value in selecting blade profiles. The variation of pump efficiency with tip clearance is greater than that reported for centrifugal pumps.

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

2003 ◽  
Vol 125 (4) ◽  
pp. 670-679 ◽  
Author(s):  
J. F. Gu¨lich
Keyword(s):  
Reynolds Number ◽  
Reynolds Numbers ◽  
Physical Models ◽  
Wall Turbulence ◽  
Pump Efficiency ◽  
Hydraulic Efficiency ◽  
Centrifugal Pumps ◽  
Roughness Effects ◽  
Specific Speed ◽  
Near Wall Turbulence

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 fraction of scalable impeller/diffuser/volute losses is found to decrease with growing specific speed. Roughness effects in the diffuser/volute are stronger than in the impeller, but the dominance of the stator over the rotor decreases with increasing specific speed. The procedure includes all flow regimes from laminar to turbulent and from hydraulically smooth to fully rough. It is validated by tests with viscosities between 0.2 to 3000 cSt and Reynolds numbers between 1500 and 108. The hydraulic losses depend on the patterns of roughness, near-wall turbulence, and the actual velocity distribution in the hydraulic passages. These effects—which are as yet not amenable to analysis—limit the accuracy of any efficiency prediction procedure for decelerated flows.

Evaluation of Blade Passage Analysis Using Coarse Grids

2000 ◽  
Vol 122 (2) ◽  
pp. 345-348 ◽  
Author(s):  
Steven M. Miner
Keyword(s):  
Rotational Speed ◽  
Stokes Equations ◽  
Axial Flow ◽  
Measured Data ◽  
Flow Coefficient ◽  
Design Parameters ◽  
Mixed Flow ◽  
Specific Speed ◽  
Coarse Grids ◽  
Flow Pump

This paper presents the results of a study using coarse grids to analyze the flow in the impellers of an axial flow pump and a mixed flow pump. A commercial CFD code (FLOTRAN) is used to solve the 3-D Reynolds Averaged Navier Stokes equations in a rotating cylindrical coordinate system. The standard k−ε turbulence model is used. The meshes for this study use 22,000 nodes and 40,000 nodes for the axial flow impeller, and 26,000 nodes for the mixed flow impeller. Both models are run on a SPARCstation 20. This is in contrast to typical analyses using in excess of 100,000 nodes. The smaller mesh size has advantages in the design environment. Stage design parameters for the axial flow impeller are, rotational speed 870 rpm, flow coefficient ϕ=0.13, head coefficient ψ=0.06, and specific speed 2.97 (8101 US). For the mixed flow impeller the parameters are, rotational speed 890 rpm, flow coefficient ϕ=0.116, head coefficient ψ=0.094, and specific speed 2.01 (5475 US). Evaluation of the models is based on a comparison of circumferentially averaged results to measured data for the same impeller. Comparisons to measured data include axial and tangential velocities, static pressure, and total pressure. A comparison between the coarse and fine meshes for the axial flow impeller is included. Results of this study show that the computational results closely match the shapes and magnitudes of the measured profiles, indicating that coarse CFD models can be used to accurately predict performance. [S0098-2202(00)02202-1]

scholarly journals Unstable Performance of a Low Specific Speed Mixed Flow Pump (1st Report, a Diffuser Rotating Stall Behavior)

2006 ◽  
Vol 72 (722) ◽  
pp. 2481-2487
Author(s):  
Masahiro MIYABE ◽  
Akinori FURUKAWA ◽  
Hideaki MAEDA ◽  
Isamu UMEKI ◽  
Yoshinori JITTANI
Keyword(s):  
Rotating Stall ◽  
Mixed Flow ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Flow Pump

Development and numerical analysis of low specific speed mixed-flow pump

2012 ◽  
Vol 15 (3) ◽  
pp. 032017 ◽  
Author(s):  
H F Li ◽  
Y W Huo ◽  
Z B Pan ◽  
W C Zhou ◽  
M H He
Keyword(s):  
Numerical Analysis ◽  
Mixed Flow ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Flow Pump

Unstable head-flow characteristic generation mechanism of a low specific speed mixed flow pump

2006 ◽  
Vol 15 (2) ◽  
pp. 115-120 ◽  
Author(s):  
Masahiro Miyabe ◽  
Hideaki Maeda ◽  
Isamu Umeki ◽  
Yoshinori Jittani
Keyword(s):  
Flow Characteristic ◽  
Generation Mechanism ◽  
Mixed Flow ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Flow Pump

scholarly journals Prediction of the Propeller Performance at Different Reynolds Number Regimes with RANS

2021 ◽  
Vol 9 (10) ◽  
pp. 1115
Author(s):  
João Baltazar ◽  
Douwe Rijpkema ◽  
José Falcão de Campos
Keyword(s):  
Reynolds Number ◽  
Turbulence Model ◽  
Scale Effects ◽  
Open Water ◽  
Reynolds Numbers ◽  
Navier Stokes ◽  
Transition Model ◽  
Sst Turbulence Model ◽  
Propeller Performance ◽  
Selection Of

In this study, a Reynolds averaged Navier-Stokes solver is used for prediction of the propeller performance in open-water conditions at different Reynolds numbers ranging from 104 to 107. The k−ω SST turbulence model and the γ−R˜eθt correlation-based transition model are utilised and results compared for a conventional marine propeller. First, the selection of the turbulence inlet quantities for different flow regimes is discussed. Then, an analysis of the iterative and discretisation errors is made. This work is followed by an investigation of the predicted propeller flow at variable Reynolds numbers. Finally, the propeller scale-effects and the influence of the turbulence and transition models on the performance prediction are discussed. The variation of the flow regime showed an increase in thrust and decrease in torque for increasing Reynolds number. From the comparison between the turbulence model and the transition model, different flow solutions are obtained for the Reynolds numbers between 105 and 106, affecting the scale-effects prediction.

LES of Internal Flows in a Mixed-Flow Pump With Performance Instability

2002 ◽  
Author(s):  
Chisachi Kato ◽  
Hiroshi Mukai ◽  
Akira Manabe
Keyword(s):  
Flow Rate ◽  
Moving Boundary ◽  
Tangential Velocity ◽  
Design Tool ◽  
Low Flow ◽  
Flow Rate Ratio ◽  
Internal Flows ◽  
Mixed Flow ◽  
Specific Speed ◽  
Flow Pump

This paper describes large eddy simulation (LES) of the internal flows of a high-specific-speed mixed-flow pump at low flow-rate ratios over which measured head-flow characteristics exhibits weak instability. In order to deal with a moving boundary interface in the flow field, a form of the finite-element method in which overset grids are applied from multiple dynamic frames of reference has been developed. The method is implemented as a parallel program by applying a domain-decomposition programming model. The predicted pump heads reproduce the instability and agree quantitatively well with their measured equivalents although the predicted stall takes place at somewhat lower flow-rate ratio than in the measurements. The phase-averaged distributions of the meridional- and tangential-velocity components at the impeller’s inlet and exit cross-sections were also compared with those measured by a Laser-Doppler velocimetry (LDV). Reasonably good agreements have been obtained between the computed and measured profiles. The developed LES program thus seems to be a promising design tool for a high specific-speed mixed-flow pump particularly for off-design evaluations.

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