Steady and Unsteady Radial Forces for a Centrifugal Pump With Impeller to Tongue Gap Variation

2005 ◽  
Vol 128 (3) ◽  
pp. 454-462 ◽  
Author(s):  
José González ◽  
Jorge Parrondo ◽  
Carlos Santolaria ◽  
Eduardo Blanco
Keyword(s):  
Centrifugal Pump ◽  
Numerical Results ◽  
Momentum Exchange ◽  
Unsteady Forces ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency ◽  
Wide Range ◽  
Radial Forces ◽  
Similarity Laws

Experimental and numerical studies are presented on the steady and unsteady radial forces produced in a single volute vaneless centrifugal pump. Experimentally, the unsteady pressure distributions were obtained using fast response pressure transducers. These measurements were compared with equivalent numerical results from a URANS calculation, using the commercial code FLUENT. Two impellers with different outlet diameters were tested for the same volute, with radial gaps between the blade and tongue of 10.0% and 15.8% of the impeller radius, for the bigger and smaller impeller diameters, respectively. Very often, pump manufacturers apply the similarity laws to this situation, but the measured specific speeds in this case were found to be slightly different. The steady radial forces for the two impellers were calculated from both the measured average pressure field and the model over a wide range of flow rates in order to fully characterize the pump behavior. Again, a deviation from the expected values applying the similarity laws was found. The data from the pressure fluctuation measurements were processed to obtain the dynamic forces at the blade passing frequency, also over a wide range of flow rates. Afterwards, these results were used to check the predictions from the numerical simulations. For some flow rates, the bigger diameter produced higher radial forces, but this was not to be a general rule for all the operating points. This paper describes the work carried out and summarizes the experimental and the numerical results, for both radial gaps. The steady and unsteady forces at the blade passing frequency were calculated by radial integration of the pressure distributions on the shroud side of the pump volute. For the unsteady forces, the numerical model allowed a separate analysis of the terms due to the pressure pulsations and terms related to the momentum exchange in the impeller. In this way, the whole operating range of the pump was studied and analyzed to account for the static and dynamic flow effects. The unsteady forces are very important when designing the pump shaft as they can produce a fatigue collapse if they are not kept under a proper working value.

Unsteady Radial Forces on the Impeller of a Centrifugal Pump With Radial Gap Variation

2003 ◽  
Author(s):  
Jose´ Gonza´les ◽  
Carlos Santolaria ◽  
Jorge Luis Parrondo ◽  
Joaqui´n Ferna´ndez ◽  
Eduardo Blanco
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Numerical Study ◽  
Unsteady Forces ◽  
Flow Rates ◽  
Blade Passage ◽  
Pressure Distributions ◽  
Dynamic Forces ◽  
Radial Forces ◽  
Radial Gap

An experimental and numerical study is presented on the unsteady radial forces produced in a centrifugal pump with volute casing. Two impellers with different outlet diameter were considered, which gave radial gaps between blade and tongue of 10% and 15.8% of the impeller radius, respectively. Firstly, the data from pressure fluctuation measurements was processed to obtain the dynamic forces at the blade-passage frequency, for a number of flow-rates. Afterwards, these results were used to check the predictions from a numerical simulation of the pump with the code Fluent. This paper describes the work carried out and summarizes the experimental and the numerical results, for both radial gaps. The steady and unsteady forces at the blade passing frequency obtained by radial integration of the pressure distributions in the shroud side of the pump volute are analysed in detail and similar trends are obtained.

Experimental Investigation of Pressure Fluctuations on Inner Wall of a Centrifugal Pump

2019 ◽  
Vol 36 (4) ◽  
pp. 401-410 ◽  
Author(s):  
Xiao-Qi Jia ◽  
Bao-Ling Cui ◽  
Zu-Chao Zhu ◽  
Yu-Liang Zhang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
High Flow ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Flow Rates ◽  
Pressure Distributions ◽  
Blade Passing Frequency

Abstract Affected by rotor–stator interaction and unstable inner flow, asymmetric pressure distributions and pressure fluctuations cannot be avoided in centrifugal pumps. To study the pressure distributions on volute and front casing walls, dynamic pressure tests are carried out on a centrifugal pump. Frequency spectrum analysis of pressure fluctuation is presented based on Fast Fourier transform and steady pressure distribution is obtained based on time-average method. The results show that amplitudes of pressure fluctuation and blade-passing frequency are sensitive to the flow rate. At low flow rates, high-pressure region and large pressure gradients near the volute tongue are observed, and the main factors contributing to the pressure fluctuation are fluctuations in blade-passing frequency and high-frequency fluctuations. By contrast, at high flow rates, fluctuations of rotating-frequency and low frequencies are the main contributors to pressure fluctuation. Moreover, at low flow rates, pressure near volute tongue increases rapidly at first and thereafter increases slowly, whereas at high flow rates, pressure decreases sharply. Asymmetries are observed in the pressure distributions on both volute and front casing walls. With increasing of flow rate, both asymmetries in the pressure distributions and magnitude of the pressure decrease.

Analysis of unsteady radial forces of multistage centrifugal pump with double volute

2018 ◽  
Vol 35 (3) ◽  
pp. 1500-1511 ◽  
Author(s):  
Baoling Cui ◽  
Xiaodi Li ◽  
Kun Rao ◽  
Xiaoqi Jia ◽  
Xiaolin Nie
Keyword(s):  
Numerical Simulation ◽  
Centrifugal Pump ◽  
Static Pressure ◽  
Radial Force ◽  
Radial Vibration ◽  
Flow Rates ◽  
Content Type ◽  
Blade Passing Frequency ◽  
Multistage Centrifugal Pump ◽  
Radial Forces

Purpose Radial vibration of horizontal centrifugal pump has a close association with radial exciting forces. The purpose of this paper is to analyze the unsteady radial force in multistage centrifugal pump with double volute in detail and investigate the relevance of static pressure, radial force and radial vibration. Design/methodology/approach The unsteady numerical simulation with realizable k-ε turbulence model was carried out for a multistage centrifugal pump with double volute using computational fluid dynamics codes Fluent. The performance tests were conducted by use of a closed loop system and performance curves from numerical simulation agree with that of experiment. Vibration tests were carried out by vibration probes instrumented on the bearing cover of pump near no-driven end. Fast Fourier transform was used to obtain the frequency components of radial forces on the impellers from numerical simulation, which are compared with ones of radial vibration from experiment in Y and Z direction. And the static pressure distributions in the impeller were analyzed under different flow rates. Findings The symmetrical double volute can effectively balance radial forces. The maximum radial force and vibration velocity appear at 0.6 Q among the three flow rates 0.6 Q, Q and 1.2 Q. The frequencies corresponding to relatively large amplitude of vibration velocities and radial forces on the impellers in Y direction are blade passing frequency of the impellers. Blade passing frequency of first-stage impeller and shaft frequency are predominating in Z direction. It indicates that the radial vibration of centrifugal pump is closely related to the unsteady radial force. Originality/value The unsteady radial forces of the impeller in multistage centrifugal pump with double volute were comprehensively analyzed. The radial forces should be considered to balance during the design of multistage centrifugal pump.

Investigations of the Effect of Annulus Taper on Transonic Turbine Cascade Flow

1986 ◽  
Vol 108 (2) ◽  
pp. 285-292 ◽  
Author(s):  
W. Bra¨unling ◽  
F. Lehthaus
Keyword(s):  
Surface Pressure ◽  
Theoretical Calculations ◽  
Three Dimensional ◽  
Computer Code ◽  
Numerical Results ◽  
Test Facility ◽  
Turbine Cascade ◽  
Pressure Distributions ◽  
Aspect Ratios ◽  
Wide Range

In a test facility for rotating annular cascades with three conical test sections of different taper angles (0, 30, 45 deg), experiments are conducted for two geometrically different turbine cascade configurations, a hub section cascade with high deflection and a tip section cascade with low deflection. The evaluation of time-averaged data derived from conventional probe measurements upstream and downstream of the test wheel in the machine-fixed absolute system is based on the assumption of axisymmetric stream surfaces. The cascade characteristics, i.e., mass flow, deflection, and losses, for a wide range of inlet flow angles and outlet Mach numbers are provided in the blade-fixed relative system with respect to the influence of annulus taper. Some of the results are compared with simple theoretical calculations. To obtain some information about the spatial structure of the flow within the cascade passages, surface pressure distributions on the profiles of the rotating test wheels are measured at three different radial blade sections. For some examples those distributions are compared with numerical results on plane cascades of the same sweep and dihedral angles and the same aspect ratios. The computer code used is based on a three-dimensional time-marching finite-volume method solving the Euler equations. Both experimental and numerical results show a fairly good qualitative agreement in the three-dimensional blade surface pressure distributions. This work will be continued with detailed investigations on the spatial flow structure.

scholarly journals Analyses of Hydrodynamic Radial Forces on Centrifugal Pump Impellers

1988 ◽  
Vol 110 (1) ◽  
pp. 20-28 ◽  
Author(s):  
D. R. Adkins ◽  
C. E. Brennen
Keyword(s):  
Theoretical Model ◽  
Centrifugal Pump ◽  
Substantial Effect ◽  
Operating Conditions ◽  
Pump Impeller ◽  
Pressure Distributions ◽  
Flow Disturbances ◽  
Radial Forces ◽  
Flow Through ◽  
Centrifugal Pump Impeller

Hydrodynamic interactions that occur between a centrifugal pump impeller and a volute are experimentally and theoretically investigated. The theoretical analysis considers the inability of the blades to perfectly guide the flow through the impeller, and also includes a quasi-one dimensional treatment of flow in the volute. Flow disturbances at the impeller discharge and the resulting forces are determined by the theoretical model. The model is then extended to obtain the hydrodynamic force perturbations that are caused by the impeller whirling eccentrically in the volute. Under many operating conditions, these force perturbations were found to be destabilizing. Comparisons are made between the theoretical model and the experimental measurements of pressure distributions and radial forces on the impeller. The theoretical model yields fairly accurate predictions of the radial forces caused by the flow through the impeller. However, it was found that the pressure acting on the front shroud of the impeller has a substantial effect on the destabilizing hydrodynamic forces.

Unsteady Flow Structure on a Centrifugal Pump: Experimental and Numerical Approaches

2002 ◽  
Author(s):  
Jose´ Gonza´lez ◽  
Carlos Santolaria ◽  
Eduardo Blanco ◽  
Joaqui´n Ferna´ndez
Keyword(s):  
Numerical Model ◽  
Centrifugal Pump ◽  
Pressure Field ◽  
Pressure Fluctuations ◽  
Side Wall ◽  
Relative Effect ◽  
Pressure Transducers ◽  
Unsteady Pressure ◽  
Blade Passing Frequency ◽  
Wide Range

Both experimental and numerical studies of the unsteady pressure field inside a centrifugal pump have been carried out. The unsteady patterns found for the pressure fluctuations are compared and a further and more detailed flow study from the numerical model developed will be presented in this paper. Measurements were carried out with pressure transducers installed on the volute shroud. At the same time, the unsteady pressure field inside the volute of a centrifugal pump has been numerically modelled using a finite volume commercial code and the dynamic variables obtained have been compared with the experimental data available. In particular, the amplitude of the fluctuating pressure field in the shroud side wall of the volute at the blade passing frequency is successfully captured by the model for a wide range of operating flow rates. Once the developed numerical model has shown its capability in describing the unsteady patterns experimentally measured, an explanation for such patterns is searched. Moreover, the possibilities of the numerical model can be extended to other sections (besides the shroud wall of the volute), which can provide plausible explanations for the dynamic interaction effects between the flow at the impeller exit and the volute tongue at different axial positions. The results of the numerical simulation are focused in the blade passing frequency in order to study the relative effect of the two main phenomena occurring at that frequency for a given position: the blade passing in front of the tongue and the wakes of the blades.

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 Investigations of the Effect of Annulus Taper on Transonic Turbine Cascade Flow

1985 ◽  
Author(s):  
W. Bräunling ◽  
F. Lehthaus
Keyword(s):  
Surface Pressure ◽  
Theoretical Calculations ◽  
Three Dimensional ◽  
Computer Code ◽  
Numerical Results ◽  
Test Facility ◽  
Turbine Cascade ◽  
Pressure Distributions ◽  
Aspect Ratios ◽  
Wide Range

In a test facility for rotating annular cascades with three conical test sections of different taper angles (0°, 30°, 45°), experiments are conducted for two geometrically different turbine cascade configurations, a hub section cascade with high deflection and a tip section cascade with low deflection. The evaluation of time averaged data derived from conventional probe measurements upstream and downstream of the test wheel in the machine-fixed absolute system is based on the assumption of axisymmetric stream surfaces. The cascade characteristics, i.e. mass flow, deflection and losses, for a wide range of inlet flow angles and outlet Mach numbers are provided in the blade-fixed relative system with respect to the influence of annulus taper. Some of the results are compared with simple theoretical calculations. To obtain some informations about the spatial structure of the flow within the cascade passages, surface pressure distributions on the profiles of the rotating test wheels are measured at three different radial blade sections. For some examples those distributions are compared with numerical results on plane cascades of the same sweep and dihedral angles and the same aspect ratios. The computer code used is based on a three-dimensional time-marching finite-volume method solving the Euler equations. Both experimental and numerical results show a fairly good qualitative agreement in the three-dimensional blade surface pressure distributions. This work will be continued with detailed investigations on the spatial flow structure.

The Effect of Impeller Cutback on the Fluid-Dynamic Pulsations and Load at the Blade-Passing Frequency in a Centrifugal Pump

2008 ◽  
Vol 130 (11) ◽  
Author(s):  
Raúl Barrio ◽  
Eduardo Blanco ◽  
Jorge Parrondo ◽  
José González ◽  
Joaquín Fernández
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Dynamic Load ◽  
Fluid Dynamic ◽  
Low Flow ◽  
Maximum Magnitude ◽  
Flow Rates ◽  
Numerical Predictions ◽  
Blade Passing Frequency ◽  
Radial Gap

A study is presented on the fluid-dynamic pulsations and the corresponding dynamic forces generated in a centrifugal pump with single suction and vaneless volute due to blade-volute interaction. Four impellers with different outlet diameters, obtained from progressive cutbacks (trimmings) of the greatest one, were successively considered in the test pump, so that the radial gap between the impeller and the volute ranged from 8.8% to 23.2% of the impeller radius. The study was based on the numerical computation of the unsteady flow through the machine for a number of flow rates by means of the FLUENT code, solving the 3D unsteady Reynolds-averaged Navier–Stokes equations. Additionally, an experimental series of tests was conducted for the pump with one of the impellers, in order to obtain pressure fluctuation data along the volute front wall that allowed contrasting the numerical predictions. The data collected from the numerical computations were used to estimate the dynamic radial forces and torque at the blade-passing frequency, as a function of flow rate and blade-tongue radial gap. As expected, for a given impeller diameter, the dynamic load increases for off-design conditions, especially for the low range of flow rates, whereas the progressive reduction of the impeller-tongue gap brings about corresponding increments in dynamic load. In particular, varying the blade-tongue gap within the limits of this study resulted in multiplying the maximum magnitude of the blade-passing frequency radial force by a factor of about 4 for low flow rates (i.e., below the nominal flow rate) and 3 for high flow rates.

Pressure Distributions in a Single and Two Versions of a Double Volute of a Centrifugal Pump

1992 ◽  
Author(s):  
W. de Ojeda ◽  
R. D. Flack ◽  
S. M. Miner
Keyword(s):  
Centrifugal Pump ◽  
Leading Edge ◽  
Pressure Measurements ◽  
Flow Rates ◽  
Pressure Drops ◽  
Pressure Distributions ◽  
Single Discharge ◽  
Repeated Pattern ◽  
Specific Speed

Pressure measurements were recorded around the impeller and along the casing wall of a centrifugal pump, 0.60 (1583 US units) specific speed, assembled with a single volute/single discharge, and two versions of a double volute/single discharge. The latter comprised a splitter positioned in the second half of the discharge (i) midway between the impeller and casing, and (ii) along a spiral symmetric to the first–half casing section. The objective of such double volute casings is to reduce forces on the impeller and thus provide longer lives. Flow rates tested ranged from 20% to 105% of design. A repeated pattern consisted of pressure increasing from the first cutwater to the splitter leading edge at which the pressure drops and thereafter increases to the discharge. This pattern was noted at all flow rates with the symmetric volute geometry and only at flow rates higher than 60% for the centered splitter. By integration of the pressures static forces were found. Time averaged static forces ranged from 6.2 N at design to 33.0 N at 20% flow for the single volute. Both double volute configurations showed considerable thrust reduction throughout but for a few exceptions. Reductions ranged from 26% at 30% flow to 62% at 90% flow for the center splitter, and from 52% reduction at 20% flow to 72% at 80% flow for the symmetric splitter. For comparison of performance of the different configurations, at flow rates above 85% of design the head was 8% and 9% less for the double volutes than for the single volutes. At flows below 40% of design the head was 3% and 4% higher for the double volutes than for the single volute.

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