Unsteady Flow Structure and Global Variables in a Centrifugal Pump

2006 ◽  
Vol 128 (5) ◽  
pp. 937-946 ◽  
Author(s):  
José González ◽  
Carlos Santolaria
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Flow Structure ◽  
Flow Model ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Operating Conditions ◽  
Local Flow ◽  
Global Variables ◽  
Wide Range

A relationship between the global variables and the dynamic flow structure numerically obtained for a low specific speed centrifugal pump is presented in this paper. A previously developed unsteady flow model is used to correlate the dynamic field with the flow characteristics inside the impeller and volute of a single-stage commercial pump. Actually, the viscous incompressible Navier-Stokes equations are solved within a 3D unsteady flow model. A sliding mesh technique is applied to take into account the impeller-volute interaction. After the numerical model has been successfully compared with the experimental data for the unsteady pressure fluctuations pattern in the volute shroud, a new step is proposed in order to correlate the observed effects with the flow structure inside the pump. In particular, the torque as a function of the relative position of the impeller blades is related to the blades loading, and the secondary flow in the volute is related to the different pressure patterns numerically obtained. Local flow analysis and qualitative study of the helicity in different volute sections is performed. The main goal of the study presented is the successful correlation of local and global parameters for the flow in a centrifugal pump. The pressure forces seem to be the main driven mechanism to establish the flow features both in the impeller and volute, for a wide range of operating conditions.

Viscous Flow Analysis in Mixed Flow Rotors

1980 ◽  
Vol 102 (1) ◽  
pp. 193-201 ◽  
Author(s):  
I. Khalil ◽  
W. Tabakoff ◽  
A. Hamed
Keyword(s):  
Viscous Flow ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Flow Characteristics ◽  
Laminar Flows ◽  
Operating Conditions ◽  
Field Analysis ◽  
Navier Stokes ◽  
Stream Channels ◽  
Wide Range

A method for analyzing the viscous flow through turbomachine rotors is presented. The field analysis is based on the solution of the full Navier-Stokes equations over the rotor blade-to-blade stream channels. An Alternating-Direction-Implicit method is employed to carry out the necessary numerical integration of the elliptic governing equations. The flow analysis may be applied to various types of turbomachine rotors. Preliminarily, only the case of laminar flows are considered in this paper. The flow characteristics within the rotors of a radial inflow turbine and a radial bladed compressor are investigated over a wide range of operating conditions. Excellent results are obtained when compared with existing experimental data. The method of this analysis is quite general and can deal with wide range of applications. Possible modification of the present study to deal with turbulent flow cases are also identified.

A One-Dimensional Unsteady Separable and Reattachable Flow Model for Collapsible Tube-Flow Analysis

1999 ◽  
Vol 121 (2) ◽  
pp. 153-159 ◽  
Author(s):  
T. Ikeda ◽  
Y. Matsuzaki
Keyword(s):  
Unsteady Flow ◽  
Flow Model ◽  
Stokes Equations ◽  
Flow Analysis ◽  
Separated Flow ◽  
Oscillatory Behavior ◽  
Separation Point ◽  
Navier Stokes ◽  
Two Dimensional ◽  
Collapsible Tube

Taking into account both flow separation and reattachment observed in available experimental results on flows in a quasi-two-dimensional channel, we present a onedimensional unsteady flow model, which is applicable to a flow in a collapsible tube. The flow model has been derived from the two-dimensional Navier–Stokes equations by introducing the concept of a dividing streamline, which divides a separated flow into a jet and a dead-water zone. We also present a criterion for the determination of a separation point. Numerical results show that the locations of the predicted separation points agree well with the experimental data. The predicted static pressure of the separated flow is almost constant downstream of the separation point and increases quickly just before the reattachment point, as observed in the experiment. Finally, using the present flow model and the separation criterion, we examine the oscillatory behavior of an unsteady flow in a symmetric channel whose walls move sinusoidally.

Numerical Simulation of the Dynamic Effects Due to Impeller-Volute Interaction in a Centrifugal Pump

2002 ◽  
Vol 124 (2) ◽  
pp. 348-355 ◽  
Author(s):  
Jose´ Gonza´lez ◽  
Joaquı´n Ferna´ndez ◽  
Eduardo Blanco ◽  
Carlos Santolaria
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Stokes Equations ◽  
Pressure Fluctuations ◽  
Flow Analysis ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Rate Dependent ◽  
Blade Passing Frequency ◽  
Wide Range

This paper shows the capability of a numerical simulation in capturing the dynamic and unsteady flow effects inside a centrifugal pump due to the impeller-volute interaction. The object of the study is a commercial centrifugal water pump with backward curved blades, which is built within a vaneless single tongue volute. For the numerical simulation, the viscous Navier-Stokes equations are handled with an unsteady calculation and the sliding mesh technique is applied to take into account the impeller-volute interaction. In keeping the unsteady terms of the equations active it is possible to correctly simulate the effects of the blade passage in front of the tongue and both the flow and pressure fluctuations induced. Time averaged numerical results are compared with the experimental performance curve and good agreement is found. The numerical flow analysis allows the study of different variables which are always difficult to measure experimentally. The dynamic variables obtained with the proposed numerical model are compared with the experimental data. In particular, the amplitude of the fluctuating pressure field at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Therefore, the main achievement of the work is in providing the modeling possibilities for the prediction of the dynamic interaction between the flow at the impeller exit and the volute tongue. Such effects at the blade passing frequency appear to follow a clear flow rate dependent spatial pattern around the volute.

A 3D Unsteady Flow Analysis in a Doubly Constricted Tube

2000 ◽  
Author(s):  
B. V. Rathish Kumar ◽  
T. Yamaguchi ◽  
H. Liu ◽  
R. Himeno
Keyword(s):  
Pressure Drop ◽  
Unsteady Flow ◽  
Stokes Equations ◽  
Vortex Formation ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
In Series ◽  
3D Unsteady Flow

Abstract Unsteady flow dynamics in a doubly constricted vessel is analyzed by using a time accurate Finite Volume solution of three dimensional incompressible Navier-Stokes equations. Computational experiments are carried out for various values of Reynolds number in order to assess the criticality of multiple mild constrictions in series and also to bring out the subtle 3D features like vortex formation. Studies reveal that pressure drop across a series of mild constrictions can get physiologically critical. Further this pressure drop is found to be sensitive to the spacing between the constrictions and also to the oscillatory nature of the inflow profile.

Theoretical and Experimental Investigation on the Flow Induced Vibrations of a Centrifugal Pump

2004 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Transient Flow ◽  
Stokes Equations ◽  
Computer Code ◽  
Numerical Approach ◽  
Experimental Investigations ◽  
Pump Operation ◽  
Pump Rotor ◽  
Wide Range

The transport of fluids which include a lot of impurities is often done by special single-stage pumps. In order to avoid clogging of the pumps, the impellers have only one blade. This minimum blade number brings strong disadvantages during the pump operation. The rotation of the impeller in the pump casing produces a strongly uneven pressure field along the perimeter of the casing. The resulting periodically unsteady flow forces affect the impeller and produce radial deflections of the pump shaft which can be recognized as vibrations at the bearing blocks or at the pump casing. These vibrations will also be transferred to the pump casing and attached pipes. In a numerical approach the hydrodynamic excitation forces of a single-blade pump were calculated from the time dependent flow field. The flow field is known from the numerical simulation of the three-dimensional, viscous, unsteady flow in the pump by using a commercial computer code determining the Reynolds averaged Navier-Stokes equations (URANS). The periodically unsteady flow forces were computed for a complete impeller revolution. This forces affect the rotor of the pump and stimulate it to oscillations. The computed forces were defined as external forces and applied as the load on the rotor for a structural analysis. The resulting oscillations of the rotor were calculated by a transient analysis of the rotors structure using a commercial FEM-Method. To verify the calculated results, experimental investigations have been performed. The deflections of the pump rotor were measured with proximity sensors in a wide range of pump operation. Measurements of the vibration accelerations at the pump casing showed the visible effects of the transient flow. To minimize the vibration amplitudes the energizing forces have been reduced by attaching a compensation mass at the impeller. This procedure can be used as “operational balancing” of the pump rotor for a certain point of operation.

Periodically Unsteady Flow in a Single-Blade Centrifugal Pump: Numerical and Experimental Results

2005 ◽  
Author(s):  
F.-K. Benra ◽  
H. J. Dohmen ◽  
M. Sommer
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Sewage Water ◽  
Numerical Results ◽  
Experimental Results ◽  
Time Dependent ◽  
Pump Operation ◽  
Wide Range ◽  
Operating Points

The composition of sewage water with partially large portions of fibers and solids requires a special pump design, in order to avoid operational disturbances by clogging. In most applications for sewage water transport, single-stage pumps with single-blade impellers are used. With this special impeller geometry largest flow channels can be realized. So fibers and solids up to an appropriate size can be transported by the pump. This minimum impeller blade number however brings disadvantages for pump operation. The development of a pressure and a suction surface of the blade gives an asymmetric pressure distribution at the perimeter of the rotor outlet and a periodically unsteady flow field arises. In a numerical approach the time accurate flow in a single-blade centrifugal pump has been calculated by solving the 3-dimensional time dependent Reynolds averaged Navier-Stokes equations (URANS) in a wide range of pump operation. The investigation of the flow included all details between suction flange and pressure flange of the pump. The numerical results show a strong dependence from impeller position for all flow parameters. For the investigated operating points strong vortices have been obtained at particular impeller positions. Experimental results have been used to verify the numerical results of time dependent flow in the single-blade pump. The computed flow field has been compared to results which were obtained from optical measurements of flow velocities by Particle Image Velocimetry at different impeller positions. A very good qualitative agreement between measurements and calculations has been obtained for all investigated operating points.

scholarly journals Gradient Span Analysis Method: Application to the Multipoint Aerodynamic Shape Optimization of a Turbine Cascade

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Hadrien Montanelli ◽  
Marc Montagnac ◽  
François Gallard
Keyword(s):  
Cost Function ◽  
Optimization Problem ◽  
Stokes Equations ◽  
Single Point ◽  
Operating Conditions ◽  
Design Variables ◽  
Wide Range ◽  
The Cost ◽  
Multipoint Optimization ◽  
Utopia Point

This paper presents the application of the gradient span analysis (GSA) method to the multipoint optimization of the two-dimensional LS89 turbine distributor. The cost function (total pressure loss) and the constraint (mass flow rate) are computed from the resolution of the Reynolds-averaged Navier–Stokes equations. The penalty method is used to replace the constrained optimization problem with an unconstrained problem. The optimization process is steered by a gradient-based quasi-Newton algorithm. The gradient of the cost function with respect to design variables is obtained with the discrete adjoint method, which ensures an efficient computation time independent of the number of design variables. The GSA method gives a minimal set of operating conditions to insert into the weighted sum model to solve the multipoint optimization problem. The weights associated to these conditions are computed with the utopia point method. The single-point optimization at the nominal condition and the multipoint optimization over a wide range of conditions of the LS89 blade are compared. The comparison shows the strong advantages of the multipoint optimization with the GSA method and utopia-point weighting over the traditional single-point optimization.

Theoretical Analysis of Flow Through Two-Dimensional Centrifugal Pump Impeller by Method of Singularities

1971 ◽  
Vol 93 (1) ◽  
pp. 35-40 ◽  
Author(s):  
S. K. Ayyubi ◽  
Y. V. N. Rao
Keyword(s):  
Centrifugal Pump ◽  
Operating Conditions ◽  
Two Dimensional ◽  
Pump Impeller ◽  
Pump Operation ◽  
Wide Range ◽  
Hydrodynamic Method ◽  
Flow Through ◽  
Experimental Values ◽  
Centrifugal Pump Impeller

The hydrodynamic method of singularities is used to analyze the flow through two-dimensional centrifugal pump impellers with blades of an arbitrary geometry. Computed values of ideal head are compared with experimental values obtained for a commercial pump. The agreement between theory and experiment is very close over a wide range of pump operation. The discrepancies that occur at other operating conditions are attributed to the effects of inlet passage and volute casing.

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