Velocity and Pressure Distributions in the Impeller Passages of Centrifugal Pumps

1980 ◽  
Vol 102 (4) ◽  
pp. 420-426 ◽  
Author(s):  
M. Murakami ◽  
K. Kikuyama ◽  
E. Asakura
Keyword(s):  
Flow Rate ◽  
Potential Flow ◽  
Flow Patterns ◽  
Surface Flow ◽  
Design Flow ◽  
Centrifugal Pumps ◽  
Velocity Measurements ◽  
Pressure Distributions ◽  
Insufficient Number ◽  
Good Agreement

The flow patterns in centrifugal pump impellers with three and seven blades, respectively, were measured using a cylindrical yaw probe and an oil surface flow method. The measured distributions of velocities and pressures for the seven (sufficient number) blade impeller at the design flow rate coincide well with the numerical solution obtained from the theoretical equation based on a potential flow. The flow patterns of the three (insufficient number) blade impeller deviate largely from those of the seven blade impeller both at the design and off-design conditions. The values of the slip factor deduced from the data of velocity measurements in the impeller passage were compared with those calculated by commonly-used formulae, and considerably good agreement was obtained for the seven blade impeller.

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.

Clocking effect in a centrifugal pump with a vaned diffuser

2020 ◽  
Vol 34 (26) ◽  
pp. 2050286
Author(s):  
Fen Lai ◽  
Xiangyuan Zhu ◽  
Yongqiang Duan ◽  
Guojun Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Loss ◽  
Total Pressure ◽  
Radial Force ◽  
Design Flow ◽  
Total Pressure Loss ◽  
Inlet Section ◽  
Centrifugal Pumps ◽  
Installation Angle

The performance and service life of centrifugal pumps can be influenced by the clocking effect. In this study, 3D numerical calculations based on the k-omega shear stress transport model are conducted to investigate the clocking effect in a centrifugal pump. Time-averaged behavior and transient behavior are analyzed. Results show that the optimum diffuser installation angle in the centrifugal pump is [Formula: see text] due to the minimum total pressure loss and radial force acting on the impeller. Total pressure loss, particularly in the volute, is considerably influenced by the clocking effect. The difference in total pressure loss in the volute at different clocking positions is 2.75 m under the design flow rate. The large total pressure loss in the volute is primarily caused by the large total pressure gradient within the vicinity of the volute tongue. The radial force acting on the impeller is also considerably affected by the clocking effect. When the diffuser installation angle is [Formula: see text], flow rate fluctuations in the volute and impeller passage are minimal, and flow rate distribution in the diffuser passage is more uniform than those in other diffuser installation angles. Moreover, static pressure fluctuations in the impeller midsection and the diffuser inlet section are at the minimum value. These phenomena explain the minimum radial force acting on the impeller. The findings of this study can provide a useful reference for the design of centrifugal pumps.

Surface flow of granular materials: model and experiments in heap formation

2001 ◽  
Vol 441 ◽  
pp. 255-264 ◽  
Author(s):  
D. V. KHAKHAR ◽  
ASHISH V. ORPE ◽  
PETER ANDRESÉN ◽  
J. M. OTTINO
Keyword(s):  
Flow Rate ◽  
Open Systems ◽  
Static Friction ◽  
Surface Flow ◽  
Two Dimensional ◽  
Surface Flows ◽  
Industrial Practice ◽  
Natural Systems ◽  
Closed Systems ◽  
Good Agreement

Granular surface flows are important in industrial practice and natural systems, but the understanding of such flows is at present incomplete. We present a combined theoretical and experimental study of quasi-two-dimensional heap formation by pouring particles continuously at a point. Two cases are considered: open systems and closed systems. Experimental results show that the shear rate in the flowing layer is nearly independent of the mass flow rate, and the angle of static friction at the bed–layer interface increases with flow rate. Predictions of the model for the flowing layer thickness and interface angles are in good agreement with experiments.

A wake singularity potential flow model for airfoils experiencing trailing-edge stall

1993 ◽  
Vol 251 ◽  
pp. 203-218 ◽  
Author(s):  
W. W. H. Yeung ◽  
G. V. Parkinson
Keyword(s):  
Potential Flow ◽  
Inviscid Flow ◽  
Near Wake ◽  
Trailing Edge ◽  
Pressure Distributions ◽  
Free Streamlines ◽  
Potential Flow Model ◽  
Theoretical Pressure ◽  
Simple Sequence ◽  
Good Agreement

An incompressible inviscid flow theory for single and two-element airfoils experiencing trailing-edge stall is presented. For the single airfoil the model requires a simple sequence of conformal transformations to map a Joukowsky airfoil, partially truncated on the upper surface, onto a circle over which the flow problem is solved. Source and doublet singularities are used to create free streamlines simulating shear layers bounding the near wake. The model's simplicity permits extension of the method to airfoil-flap configurations in which trailing-edge stall is assumed on the flap. Williams’ analytical method to calculate the potential flow about two lifting bodies is incorporated in the Joukowsky-arc wake-singularity model to allow for flow separation. The theoretical pressure distributions from these models show good agreement with wind-tunnel measurements.

Experimental Visualization of Gas-Liquid Flow Patterns in a Centrifugal Rotor

2019 ◽  
Author(s):  
Henrique Stel ◽  
Edgar Minoru Ofuchi ◽  
Rafael Fabrício Alves ◽  
Sergio Chiva ◽  
Rigoberto E. M. Morales
Keyword(s):  
Flow Rate ◽  
Liquid Flow ◽  
Volume Fraction ◽  
Flow Patterns ◽  
Centrifugal Pumps ◽  
Gas Volume Fraction ◽  
Gas Liquid Flow ◽  
Liquid Flows ◽  
Complex Phenomena ◽  
Gas Volume

Abstract Centrifugal pumps operating with gas-liquid flows can undergo severe performance degradation. This can be attributed to an effect of the gas phase on the liquid flow orientation in the pump impeller channels, which induces additional hydraulic losses that negatively affect the delivered head and flow rate. Effort to investigate the effect of many operating parameters on the pump performance under multiphase flows can be found on numerous experimental investigations. Few studies, however, bring together flow visualization to understand the physics behind the behavior of centrifugal pumps with gas-liquid flows. One issue is that pumps involve rotating parts, metallic casing and limited visual access, sometimes making it hard to interpret flow patterns and to understand complex phenomena, such as bubble breakup and coalescence. Such issues usually lead to unsatisfactory image quality, which in turn makes it difficult to extract quantitative data from the obtained images, such as gas volume fraction and bubble size distribution. In an attempt to overcome many difficulties of previous investigations, this work presents an experimental study aimed to visualize gas-liquid flow patterns in a centrifugal rotor prototype using a novel approach. The experimental apparatus uses a plane and transparent rotor, assembled with an intake pipe and a discharge chamber by means of a dynamic seal system that dismisses the use of an enclosing pump casing. This makes possible to use back illumination of the impeller for visualization, which in turn is done by using a camera attached to the impeller axis for filming in a rotating frame of reference. This setup, which is new in the open literature, provides high image contrast and sharpness for clear interpretation of the flow patterns found inside the rotor channels for a wide range of operating conditions. This advantage, in turn, allows using image processing for quantitative assessment of gas volume fraction distributions. Pressure rise versus flow rate curves are measured together to investigate the rotor performance degradation associated with the gas-liquid flow patterns for a range of liquid and gas flow rates. Information obtained with the designed experimental setup at controlled conditions help not just to bring further understanding to the complex phenomena involved with multiphase flows in rotating devices, but also in the direction of validating a numerical model for reliable simulations of gas-liquid flows in centrifugal pumps, which is lacking in the current literature.

Aerodynamically Induced Radial Forces in a Centrifugal Gas Compressor: Part 1—Experimental Measurement

1998 ◽  
Vol 120 (2) ◽  
pp. 383-390 ◽  
Author(s):  
J. J. Moore ◽  
M. B. Flathers
Keyword(s):  
Experimental Measurement ◽  
Operating Conditions ◽  
Design Flow ◽  
Centrifugal Pumps ◽  
Pressure Distributions ◽  
Pressure Fields ◽  
Radial Forces ◽  
Overall Efficiency ◽  
Improved Performance ◽  
Radial Loading

Net radial loading arising from asymmetric pressure fields in the volutes of centrifugal pumps during off-design operation is well known and has been studied extensively. In order to achieve a marked improvement in overall efficiency in centrifugal gas compressors, vaneless volute diffusers are matched to specific impellers to yield improved performance over a wide application envelope. As observed in centrifugal pumps, nonuniform pressure distributions that develop during operation above and below the design flow create static radial loads on the rotor. In order to characterize these radial forces, a novel experimental measurement and post-processing techniquesis employed that yields both the magnitude and direction of the load by measuring the shaft centerline locus in the tilt-pad bearings. The method is applicable to any turbomachinery operating on fluid film radial bearings equipped with proximity probes. The forces are found to be a maximum near surge and increase with higher pressures and speeds. The results are nondimensionalized, allowing the radial loading for different operating conditions to be predicted.

Theoretical and Numerical Analysis of the Pressure Distribution and Discharge Velocity in Flows Under Sluice Gates

2018 ◽  
Author(s):  
Philipp Epple ◽  
Michael Steppert ◽  
Michael Steber ◽  
Andreas Malcherek
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Surface Flow ◽  
Momentum Balance ◽  
Parameter Study ◽  
Bottom Pressure ◽  
Sluice Gate ◽  
Vena Contracta ◽  
Pressure Distributions ◽  
Discharge Velocity

The flow under sluice gates is well known in open channel hydraulics. There are theoretical, semi-empirical and empirical equations to determine the flow rate under a sluice gate Most of these formulas are based on the Bernoulli equation applied at the inflow cross section and in the vena contracta behind the gate. In 2017 Malcherek [1] showed that it is also possible to apply the integral momentum balance to the sluice gate. When assuming hydrostatic pressure distributions in the inflow cross section and on the weir’s plate then the simple formula VA=(3/4) g h0=0.6122 g h0 is obtained, which is in perfect agreement with the classical vena contracta theory for small opening ratios h0/a. In the outflow cross section under the gate the bottom pressure was assumed to be the mean of the hydrostatic bottom pressure before and behind the sluice gate. In this paper Malcherek’s momentum balance theory will be investigated in further detail with numerical CFD RANS computations of the free surface flow below sluice gate. The exact pressure distributions on the bottom as well as on the gate were obtained for different openings ratios and flow conditions at the sluice gate in a systematic parameter study. These pressure distributions have been introduced into the integral momentum equation and the discharge velocity as well as the flow rate at the sluice gate were investigated and compared with the pure numerical results. These results were also compared with the theoretical and empirical approaches of the literature and a detailed analysis is given.

Effects of Flow Patterns on Aerodynamic Forces of a Square Cylinder at Incidence

2011 ◽  
Vol 27 (3) ◽  
pp. 347-355 ◽  
Author(s):  
R. F. Huang ◽  
B. H. Lin
Keyword(s):  
Lateral Surface ◽  
Incidence Angle ◽  
Pressure Coefficient ◽  
Flow Patterns ◽  
Surface Flow ◽  
Square Cylinder ◽  
Pressure Distributions ◽  
New Findings ◽  
Drag And Lift ◽  
Critical Incidence

ABSTRACTThe pressure distributions around a square cylinder in a crossflow were experimentally studied in a wind tunnel. The subject of study was conventional, but the results presented new findings. The experiments were performed by using a home-made linear pressure scanner. The ranges of Reynolds number and incidence angle were 2 × 104- 9.4 × 104and 0° - 45°, respectively. According to the topological flow patterns, the flows around the square cylinder at incidence showed three characteristic regimes: The subcritical, supercritical, and wedge flows. A critical incidence angle αcri= 15° separated the regimes of subcritical and supercritical modes. The results of current study provided information regarding the effects of the topological flow patterns on surface pressure distribution, drag, and lift characteristics. The pressure distributions, drag, and lift presented different characteristics in different characteristic flow regimes and had close correlations with the flows. At the critical incidence angle 15° which separated the subcritical and supercritical regimes, the surface-averaged pressure coefficient on each face displayed local extreme value—The drag coefficient attained a minimum of 1.6, the lateral force coefficient reached a maximum of 0.9. The appearance of the minimum drag at the critical incidence angle was attributed to the reduction of wake width which was induced by two surface flow phenomena: (1) reattachment of the separated boundary layer on the lateral surface facing windward at the critical incidence angle and (2) flow pattern change on the lateral surface facing leeward.

Hydraulic Axial Thrust in Multistage Centrifugal Pumps

1980 ◽  
Vol 102 (1) ◽  
pp. 64-69 ◽  
Author(s):  
T. Iino ◽  
H. Sato ◽  
H. Miyashiro
Keyword(s):  
Boundary Layer ◽  
Computer Program ◽  
Flow Rate ◽  
Theoretical Study ◽  
Experimental Results ◽  
Leakage Flow ◽  
Centrifugal Pumps ◽  
Axial Thrust ◽  
Pressure Distributions ◽  
Annular Seal

An experimental and theoretical study is performed with a single stage pump. The influence of the flow rate, the axial displacement of the impeller, and annular seal clearances on the hydraulic axial thrust is investigated. Pressure distributions measured in the space between the impeller and the casing agree with those calculated by the Kurokawa-Toyokura method when the leakage flow is inward in the space. It is clarified that the method is sometimes not available for the outward leakage flow because of the large thickness of the boundary layer in the space. A computer program for calculating the axial thrust in multistage centrifugal pumps is developed based on the method and experimental results. Axial thrusts measured in prototype multistage pumps agree with the calculation.

Rotating Instability in a Centrifugal Pump Impeller

2005 ◽  
Author(s):  
Giorgio Pavesi ◽  
Guido Ardizzon ◽  
Giovanna Cavazzini
Keyword(s):  
Flow Rate ◽  
Design Flow ◽  
Tip Clearance ◽  
Wake Flow ◽  
Common Belief ◽  
Centrifugal Pumps ◽  
Tip Leakage Flow ◽  
Unsteady Pressure ◽  
Radial Pump ◽  
Rotating Instability

The objective of the study was the experimental and computational investigation of the unsteady flow in the centrifugal pumps. This paper analysed the effect of the vaneless stator interference on the exit flow field of a radial pump operated in the DIM facility. High-response pressure transducers were used to determine unsteady pressure field at three planes at the pump and at diffuser inflows. The experimental data showed that unsteady pressure disturbances modes change when the flow was reduced. Detailed analysis showed that disturbances occur at distinct frequencies and that these rotated in the circumferential direction. Comparison of the pressure signals measured at two circumferential locations on the casing confirmed the characteristic frequency pattern to be a so called “rotating instability”. This unsteady phenomenon was highlighted both at design flow rate and at low flow rates. The azimuthal distributions exhibited significant nonuniformities. The amplitude of this non-uniformity was sensitive to the flow rate. A simple model showed that, contrary to the common belief, the transport of the vane wake and secondary flows across the rotor was not enough to explain the magnitude of the variations. In this paper numerical investigations of the unsteady three-dimensional flow through the pump stage were also presented. Turbulence was modelled both by the k-ω transport equations model, and Reynolds Stress Model based on the ω-equation. The effects of the tip leakage flow were considered by meshing the tip clearance between rotor blade and casing. Results showed the jet-wake flow pattern induced an unstable vortex, which influenced flow discharging from the adjacent passage and destabilised jet-wake flow in the passage. Both calculations and measurements detected the periodic fluctuations at impeller discharge which were found to be coherent from blade to blade and possessed a rich harmonic content.

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