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.

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.

Comparison of Experimental and Numerical Obtained Velocity Fields in a Single-Blade Centrifugal Pump

2006 ◽  
Author(s):  
Friedrich-Karl Benra ◽  
Hans Josef Dohmen ◽  
Marcel Zwingenberg
Keyword(s):  
Numerical Simulations ◽  
Centrifugal Pump ◽  
Transient Flow ◽  
Stokes Equations ◽  
Reverse Flow ◽  
Strong Dependence ◽  
Time Dependent ◽  
Wide Range ◽  
Operating Points ◽  
Blade Pump

The development of a pressure and a suction surface of a single-blade pump impeller leads to a strong asymmetric pressure distribution at the perimeter of the rotor outlet. The interaction of the impeller flow with the pump casing produces a flow field which is periodic with the impeller turning. In a numerical approach the transient flow in a complete single-blade centrifugal pump has been calculated by solving the 3-dimensional time dependent Reynolds averaged Navier-Stokes equations (URANS) with a commercial CFD code for a wide range of pump operation. A strong dependence from the impeller position has been recognized for all flow parameters. Especially at off-design conditions the flow in the impeller and in the casing showed stall and reverse flow at particular impeller positions. Experiments have been used to validate the numerical investigations of the time dependent flow in the single-blade pump. The submersible pump, completely made of transparent plastic, has been investigated in detail by the Particle Image Velocimetry. The phase averaged 2D-velocity field inside the pump was measured for the same operating points which were investigated by numerical methods in advance. Measurement planes near the hub and the shroud disc and also at mid-span of the blade were chosen to expose the 3D-character of the flow inside the pump. The measured velocities were compared to the results from numerical simulations in detail. The good agreement between measurements and calculations, which was obtained for all investigated operating points, certifies the numerical simulations a high accuracy.

Numerical predictions of ship motions at high forward speed

1991 ◽  
Vol 334 (1634) ◽  
pp. 241-252 ◽  
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Steady Flow ◽  
Added Mass ◽  
Numerical Results ◽  
Experimental Results ◽  
Ship Motions ◽  
Forward Speed ◽  
Numerical Predictions

A theory for ship motions at high forward speed is presented. The theory includes interaction between the steady and unsteady flow field. Numerical results for the steady flow and added mass and damping are compared with experimental results.

Study on Radial Load in a Centrifugal Pump with Slope Volute Using CFD

2012 ◽  
Vol 229-231 ◽  
pp. 571-575
Author(s):  
Ning Zhang ◽  
Min Guan Yang ◽  
Bo Gao ◽  
Zhong Li
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Empirical Formula ◽  
Numerical Results ◽  
Radial Load ◽  
Flow Rates

Unsteady flow field in a centrifugal pump causes significant radial load on the impeller leading to the vibration in consequence. In order to reduce radial load, a special slope volute was proposed. The full 3D-URANS equations were solved for several flow rates between 60%~150% of rated conditions. The magnitude of average radial load was estimated by empirical formula. It was found that the numerical results agree with the results obtaining from empirical formula quite well. When adopting slope volute, the radial load on the impeller is much smaller compared with conventional spiral volute. So it is convinced that the radial load can be reduced significantly when using slope volute.

scholarly journals DQ-Frame Admittance Estimation of Three-Phase Converters with a Wide Range of Operating Points

2021 ◽  
Author(s):  
Hong Gong ◽  
xiongfei wang ◽  
Dongsheng Yang
Keyword(s):  
Error Estimation ◽  
Closed Loop ◽  
Estimation Method ◽  
Experimental Results ◽  
Multidimensional Interpolation ◽  
Three Phase ◽  
Wide Range ◽  
Linearized Model ◽  
Operating Points ◽  
Error Estimation Method

The <i>dq</i>-frame admittance of closed-loop controlled three-phase converters is a linearized model that is dependent on the operating points of the system. Yet, it is impractical to measure the converter admittance at all operating points. This paper, thus, proposes an approach to estimating the <i>dq</i>-frame admittance of three-phase converters at a wide range of operating points. The method applies multidimensional interpolation to a given set of admittance data, which is measured from the pre-defined operating points. The accuracy of interpolation is then evaluated by using the posterior error estimation method. The number of pre-defined operating points is next adjusted to find a good compromise between the accuracy and efficiency of the approach. Simulations and experimental results verify the effectiveness of the approach.<div><br></div>

Numerical Study of Rotor–Stator Interaction of a Centrifugal Pump at Part Load With Special Emphasis on Unsteady Blade Load

2020 ◽  
Vol 142 (8) ◽  
Author(s):  
Nicolas Casimir ◽  
Xiangyuan Zhu ◽  
Markus Hundshagen ◽  
Gerhard Ludwig ◽  
Romuald Skoda
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Measurement Data ◽  
Load Flow ◽  
Secondary Outcome ◽  
Pump Design ◽  
Part Load ◽  
Unsteady Characteristics

Abstract Three-dimensional (3D) unsteady Reynolds-averaged Navier–Stokes (URANS) flow simulations are conducted to investigate the highly unsteady flow field at part load operation of a centrifugal pump. By the availability of unsteady flow field measurement data in the impeller wake region, a thorough validation of the simulation method is performed. Grid independence of the results is ensured. Unsteady characteristics in terms of head and shaft power as well as transient blade loads are evaluated to assess the unsteady pump performance. Significant mis-loading of the blading is revealed when one blade passes the volute tongue and associated with the strong unsteady and 3D flow field in the impeller-volute tongue region. Negative radial velocity in the tongue region is the origin of a vortex at the blade pressure side and a subsequent pressure drop that leads to even temporally negative blade loading. The results provide a detailed insight in the complex part load flow field that might be utilized for an improved pump design. As a valuable secondary outcome, a comparison of results obtained by two widely used computational fluid dynamics (CFD) codes for pump flow simulation is provided, i.e., the commercial code ansyscfx and the branch foam-extend of the open source software openfoam. It is found that the results of both methods in terms of unsteady characteristics as well as local ensemble-averaged velocity field are consistent.

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.

Three-Dimensional Wake Decay Inside of a Compressor Cascade and Its Influence on the Downstream Unsteady Flow Field: Part II—Unsteady Flow Field Downstream of the Stator

1991 ◽  
Vol 113 (2) ◽  
pp. 190-197 ◽  
Author(s):  
C. Poensgen ◽  
H. E. Gallus
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Turbulent Flows ◽  
Velocity Vector ◽  
Three Dimensional ◽  
Time Dependent ◽  
Major Influence ◽  
Hot Wire ◽  
Compressor Cascade ◽  
Turbulent Flow Field

A measuring technique based on multisensor hot-wire anemometry has been developed to determine the unsteady three-dimensional velocity vector and the structure of turbulent flows. It then has been applied to the passage and the exit flow of an annular compressor cascade, which is periodically disturbed by the wakes of a cylinder rotor, located about 50 percent of blade chord upstream. In Part I of this paper the decay of the rotor wakes has been described first without stator and secondly through a stator passage. The time-dependent turbulent flow field downstream of this stator is discussed in Part II of this paper. The rotor wakes have a major influence on the development of three-dimensional separated regions inside the compressor cascade, and this interaction will be addressed in both parts of the paper.

The Unsteady Pressure Field in a High Specific Speed Centrifugal Pump Impeller—Part II: Transient Hysteresis in the Characteristic

1999 ◽  
Vol 121 (3) ◽  
pp. 627-632 ◽  
Author(s):  
Kevin A. Kaupert ◽  
Thomas Staubli
Keyword(s):  
Flow Field ◽  
Centrifugal Pump ◽  
Pressure Fluctuations ◽  
Rate Of Change ◽  
Nonlinear Dependence ◽  
Pump Impeller ◽  
Impeller Blade ◽  
Pump Operation ◽  
Stationary Frame ◽  
Specific Speed

Hysteresis in a pump characteristic results from instability phenomena involving complex three dimensional flow with recirculation. The unsteady flow field on the top and bottom branches of a hysteresis loop in a high specific speed (ωs = 1.7) centrifugal pump characteristic was experimentally evaluated. A hypothesis for recirculation zones and prerotation as power dissipaters is proposed for explaining the discrepancy in the pressure and shaft power hysteresis. The experimental investigation was performed in both the rotating and stationary frame. In the rotating frame 25 miniature pressure transducers mounted in an impeller blade passage were sampled with a telemetry system. In the stationary frame a fast response probe was implemented. The changing impeller flow field manifested itself between the two branches of the hysteresis with increasing stochastic pressure fluctuations. Using this information the position, size, and strength of the impeller recirculation was quantitatively determined. Theoretically the rate of change of useful hydraulic power in the hysteresis regime during transient pump operation was found to be a function of throttling rate. Quasi-steady behavior existed for slow throttling, |dφ/dt| < 0.005 s−1. A second-order nonlinear dependence on the throttle rate was determined for the change of useful flow power during the commencement/cessation of the impeller recirculation.

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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