Laser Velocimeter Measurements in Shrouded and Unshrouded Radial Flow Pump Impellers

1987 ◽  
Vol 109 (1) ◽  
pp. 70-76 ◽  
Author(s):  
C. P. Hamkins ◽  
R. D. Flack
Keyword(s):  
Radial Flow ◽  
Axial Direction ◽  
Design Flow ◽  
Flow Coefficient ◽  
Wake Region ◽  
Flow Rates ◽  
Tip Leakage ◽  
Passage Vortex ◽  
Measured Position ◽  
Radial Flow Pump

Shrouded and unshrouded versions of a four-vaned radial flow impeller with a design flow coefficient of 0.063 were tested in a volute pump using a two-component frequency-shifted laser velocimeter. Velocity profiles were measured at six flow rates and at four radial and six circumferential positions in the volute. The variations of the velocity from blade to blade and in the axial direction were measured and are presented. A passage vortex caused by tip leakage and relative casing wall velocity was found in the unshrouded impeller. The tip leakage did not accumulate in the suction wake region; the suction wake region was only 30 to 50 percent as large in the unshrouded impeller as compared to the shrouded impeller. The slip was 30 percent higher in the unshrouded impeller and the variation of slip with flow rate is presented. At no measured position in the impellers did the slip factor reach unity; the closest approach was 0.90. Reverse loadings of the vanes at outer radii were found for flow rates below the impeller/volute matching point for both impellers.

Identification of Critical Net Positive Suction Head From Noise and Vibration in a Radial Flow Pump for Different Leading Edge Profiles of the Vane

2013 ◽  
Vol 135 (12) ◽  
Author(s):  
S. Christopher ◽  
S. Kumaraswamy
Keyword(s):  
Radial Flow ◽  
Leading Edge ◽  
Open Circuit ◽  
Experimental Results ◽  
Experimental Investigations ◽  
Flow Rates ◽  
Noise And Vibration ◽  
Operating Condition ◽  
Radial Flow Pump ◽  
Flow Pump

Experimental investigations concerning cavitation in radial flow pump for three different leading edge profiles of the vane were carried out in an open circuit system. The operating condition of the radial flow pump under cavitating case was understood by measurement of noise and vibration along with the pump parameters for various speeds and flow rates. The outcome of the experimental results revealed that the noise and vibration were better predictors of inception and development of cavitation. Further observation inferred from critical net positive suction head (NPSH) curve of 3% head drop and critical NPSH value of noise and vibration are presented.

Performance Evaluation of Contra-Rotating Fans Operating Under Different Speed Combinations

2019 ◽  
Author(s):  
Navjot Joshi ◽  
Manas Madasseri Payyappalli ◽  
A. M. Pradeep
Keyword(s):  
Numerical Study ◽  
Pressure Ratio ◽  
Axial Direction ◽  
Flow Coefficient ◽  
Suction Surface ◽  
Flow Angle ◽  
Tip Leakage Vortex ◽  
Stall Inception ◽  
Tip Leakage ◽  
Flow Mechanisms

Abstract One of the advantages of a contra-rotating fan is its possibility to operate both the rotors at different speeds. Owing to this possibility, the performance of a contra-rotating fan can be controlled by operating it at different speed combinations. A numerical study of a low aspect ratio contra-rotating fan in low subsonic regime is carried out under various speed combinations of the rotors. Both steady state and Nonlinear Harmonic (NLH) simulations are performed to identify the important flow mechanisms in the contra-rotating fan. The results show that the diffusion factor of rotor-2 is significantly high towards the hub region which implies that large separations are likely to occur at the hub. The wake of rotor-1 is observed to impinge on the suction surface of rotor-2. Rotor-2 generates a strong suction effect at high rotational speeds and thereby delays the stall inception in the whole stage and shows an improvement in the stage pressure ratio. The upstream effect strongly influences the performance of rotor-1. When rotor-2 rotates at higher rotational speed, due to the suction effect, the flow angle at the exit of rotor-1 decreases which allows the fan to operate at lower flow coefficient. When the suction effect is very strong, it pulls the tip leakage vortex of rotor-1 towards the axial direction. Due to the suction effect, the location of the appearance of tip-leakage vortex moves further downstream. The tip-leakage vortex makes a higher angle with the blade chord at near stall conditions for speed combination Nd – 1.5Nd in contrast to a lower angle for speed combination Nd – 0.5Nd. In summary, the paper describes the performance changes, flow physics and the rotor-rotor interaction mechanisms for different speed combinations of a contra-rotating fan.

scholarly journals Overall Performance of a Centrifugal Vaned Diffuser Pump for Different Flow Rates, Experimental and Numerical Comparisons

2020 ◽  
Vol 15 ◽  
Keyword(s):  
Numerical Data ◽  
Computer Code ◽  
Design Flow ◽  
Experimental Results ◽  
Vaned Diffuser ◽  
Flow Rates ◽  
Experimental Works ◽  
Overall Performance ◽  
Radial Flow Pump ◽  
Flow Pump

The article presents the analysis of the interactions between the impeller and the vaned diffuser of a radial flow pump. The tests were carried out on the so-called SHF impeller, coupled with a vaned diffuser, and working with air. The particularity of this machine is that the diffuser design flow rate corresponds to 80% of the impeller one. All experimental works were performed at the Fluid Mechanics Laboratory in ENSAM, Lille, France. Investigations have been made for five different flow rates. Global performances of the machine are evaluated thanks to pressure measurements and averaged velocities obtain with a three hole probe, at nine angular positions at diffuser inlet and outlet just as five radial positions in a middle section of a blade-to-blade passage. A post-processing procedure, based on statistical tools, was applied to the experimental results in order to reach a better understanding of the phenomena. In another approach, a numerical simulation of the flow inside the pump, for eight different relative angular positions of the diffuser relative to the impeller (Frozen rotor) was performed by the STAR-CCM+ software. The experimental results were compared to numerical data obtained with the help of STAR-CCM+ computer code.

Numerical Simulation of the Transient Flow in a Radial Flow Pump during Stopping Period

2011 ◽  
Vol 133 (11) ◽  
Author(s):  
J. Liu ◽  
Z. Li ◽  
L. Wang ◽  
L. Jiao
Keyword(s):  
Radial Flow ◽  
Transient Flow ◽  
Pressure Fluctuations ◽  
Pressure Rise ◽  
Flow Coefficient ◽  
Published Data ◽  
Crossover Point ◽  
Vof Model ◽  
Radial Flow Pump ◽  
Flow Pump

Three-dimensional (3-D) unsteady incompressible and non-cavitating flow in a radial flow pump during the rapid stopping period was numerically studied by CFD. The dynamic mesh (DM) method combined with non-conformal grid boundaries was applied to simulate the transient stopping process. In order to exclude the uncertainty of the unsteady inlet and outlet boundaries, a loop pumping system was established, which was composed of pipes, a reservoir with an air part on the top, and a driving pump. Simulations were performed based on the standard k-ɛ turbulence model and volume of fluid (VOF) model. Results showed that the air part in the reservoir approximated real conditions when using the VOF model. Pressure fluctuations were reduced and a sharp increase of pressure at the inlet of the pump was observed at the beginning of the stopping period. Specific transient characteristics, such as the flow-rate, head and efficiency, were analyzed during the deceleration period and compared with corresponding quasi-steady results. The deviation of the quasi-steady hypothesis in predicting the transient stopping process of radial flow pumps is thought to be caused by differences in the predicted vortex in the impeller. The transient curve showing the relationship between the instantaneous flow coefficient and total pressure rise coefficient was analyzed and compared with the quasi-steady curve. The two curves had a crossover point when the stall just occurs in the impeller during the transient process. Simulation results were also compared and validated using published data.

Radial Forces in a Pump Impeller Caused by a Volute Casing

1962 ◽  
Vol 84 (4) ◽  
pp. 337-340 ◽  
Author(s):  
G. T. Csanady
Keyword(s):  
Radial Flow ◽  
Incidence Angle ◽  
Logarithmic Spiral ◽  
Design Flow ◽  
Angle Of Incidence ◽  
Pump Impeller ◽  
Flow Rates ◽  
Fluid Theory ◽  
Radial Forces ◽  
Good Agreement

The volute casing of a radial flow impeller is replaced by an “equivalent” logarithmic spiral which, at the design flow rate of the pump, does not exert a force on the fluid discharged by the impeller. At other flow rates there is a nonzero angle of incidence and the spiral, which may be regarded as the single blade of a radial flow cascade, exerts a “lift” force. This force is calculated by the methods of perfect fluid theory, first mapping the spiral onto a flat-plate cascade, then establishing the pressure distribution. Incidence angle and the magnitude of the absolute exit velocity from the impeller govern the lift forces and by a consideration of the velocity triangles at impeller exit some qualitative features of the behavior of radial forces on the impeller are deduced. Quantitative comparison with the experimental results of Iversen, et al., [4] also shows good agreement.

PIV Measurements in the Impeller and the Vaneless Diffuser of a Radial Flow Pump in Design and Off-Design Operating Conditions

2002 ◽  
Vol 124 (3) ◽  
pp. 791-797 ◽  
Author(s):  
G. Wuibaut ◽  
G. Bois ◽  
P. Dupont ◽  
G. Caignaert ◽  
M. Stanislas
Keyword(s):  
Radial Flow ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Experimental Program ◽  
Vaneless Diffuser ◽  
Test Rig ◽  
Flow Rates ◽  
Radial Flow Pump ◽  
Flow Pump ◽  
Relative Flow

This paper presents and discusses the results of an experimental program that has been made on an air test rig of a radial flow pump. The tested impeller is the so-called SHF impeller. Many experimental data have already been produced (tests in air and in water) on that geometry and these results are still used as databases for the validation of CFD codes. For the present study, an air test rig has been chosen for optical access facilities and measurements were realized with a vaneless diffuser. The 2D Particle Image Velocimetry technique has been used and measurements of flow velocities have been made simultaneously in the outer part of the impeller and in the vaneless diffuser. Measurements have been realized in five planes, in the hub to shroud direction, for various relative flow rates (design and off-design operating conditions). First, the paper focus on the evolutions of the phase averaged velocity charts in the impeller and the diffuser. Limitations of the phase averaging technique clearly appear in the very low partial flow rates and this will be related to previous pressure measurements analysis establishing the occurrence of rotating stall within the impeller for such operating conditions. The paper also proposes an analysis of the rates of fluctuations of the velocity charts and the evolutions in the various measuring planes as the relative flow rate becomes lower.

Analysis of the Rotor-Stator Interaction in a Radial Flow Pump

2009 ◽  
pp. 141-151 ◽  
Author(s):  
G. Cavazzini ◽  
G. Pavesi ◽  
G. Ardizzon ◽  
P. Dupont ◽  
S. Coudert ◽  
...  
Keyword(s):  
Radial Flow ◽  
Rotor Stator Interaction ◽  
Radial Flow Pump ◽  
Flow Pump

scholarly journals Laser-Doppler Velocimetry Measurements Inside a Backward Curved Centrifugal Fan

2001 ◽  
Vol 7 (3) ◽  
pp. 173-181
Author(s):  
Tong-Miin Liou ◽  
Meng-Yu Chen
Keyword(s):  
Flow Rate ◽  
Turbulence Intensity ◽  
Laser Doppler Velocimetry ◽  
Reverse Flow ◽  
Flow Region ◽  
Design Flow ◽  
Laser Doppler ◽  
Centrifugal Fan ◽  
Doppler Velocimetry ◽  
Flow Rates

Laser-Doppler velocimetry (LDV) measurements are presented of relative mean velocity and turbulence intensity components inside the impeller passage of a centrifugal fan with twelve backward curved blades at design, under-design, and over-design flow rates. Additional LDV measurements were also performed at the volute outlet to examine the uniformity of the outlet flow for the three selected flow rates. Complementary flow visualization results in the tongue region are further presented. It is found that the number of characteristic flow regions and the average turbulence level increase with decreasing air flow rate. For the case of under-design flow rate, there are a through-flow region on the suction side, a reverse flow region on the pressure side, and a shear layer region in between. The corresponding average turbulence intensity is as high as 9.1% of blade tip velocity.

Fan Performance Scaling With Inlet Distortions

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
J. J. Defoe ◽  
M. Etemadi ◽  
D. K. Hall
Keyword(s):  
Design Flow ◽  
Flow Coefficient ◽  
Axial Fan ◽  
Fan Performance ◽  
Physical Mechanisms ◽  
Viscous Losses ◽  
Performance Scaling ◽  
Large Distortion ◽  
Stator Blade ◽  
Primary Focus

Applications such as boundary-layer-ingesting (BLI) fans and compressors in turboprop engines require continuous operation with distorted inflow. A low-speed axial fan with incompressible flow is studied in this paper. The objectives are to (1) identify the physical mechanisms which govern the fan response to inflow distortions and (2) determine how fan performance scales as the type and severity of inlet distortion varies at the design flow coefficient. A distributed source term approach to modeling the rotor and stator blade rows is used in numerical simulations in this paper. The model does not include viscous losses so that changes in diffusion factor are the primary focus. Distortions in stagnation pressure and temperature as well as swirl are considered. The key findings are that unless sharp pitchwise gradients in the diffusion response, strong radial flows, or very large distortion magnitudes are present, the response of the blade rows for strong distortions can be predicted by scaling up the response to a weaker distortion. In addition, the response to distortions which are composed of nonuniformities in several inlet quantities can be predicted by summing up the responses to the constituent distortions.

EFFECT OF AXIAL CASING GROOVE GEOMETRY ON ROTOR-GROOVE INTERACTIONS IN THE TIP REGION OF A COMPRESSOR

2021 ◽  
pp. 1-54
Author(s):  
Subhra Shankha Koley ◽  
Huang Chen ◽  
Ayush Saraswat ◽  
Joseph Katz
Keyword(s):  
Rotor Blade ◽  
Leading Edge ◽  
Secondary Flows ◽  
Low Flow ◽  
Flow Angle ◽  
Flow Rates ◽  
Piv Measurements ◽  
Tip Leakage ◽  
Large Vortex ◽  
Blade Leading Edge

Abstract This experimental study characterizes the interactions of axial casing grooves with the flow in the tip region of an axial turbomachine. The tests involve grooves with the same inlet overlapping with the rotor blade leading edge, but with different exit directions located upstream. Among them, U grooves, whose circumferential outflow opposes the blade motion, achieve a 60% reduction in stall flowrate, but degrade the efficiency around the best efficiency point (BEP) by 2%. The S grooves, whose outlets are parallel to the blade rotation, improve the stall flowrate by only 36%, but do not degrade the BEP performance. To elucidate the mechanisms involved, stereo-PIV measurements covering the tip region and interior of grooves are performed in a refractive index matched facility. At low flow rates, the inflow into both grooves, which peaks when they are aligned with the blade pressure side, rolls up into a large vortex that lingers within the groove. By design, the outflow from S grooves is circumferentially positive. For the U grooves, fast circumferentially negative outflow peaks at the base of each groove, causing substantial periodic variations in the flow angle near the blade leading edge. At BEP, interactions with both grooves become milder, and most of the tip leakage vortex remains in the passage. Interactions with the S grooves are limited hence they do not degrade the efficiency. In contrast, the inflow into and outflow from the U grooves reverses direction, causing entrainment of secondary flows, which likely contribute to the reduced BEP efficiency.

Sign in / Sign up

Export Citation Format

Share Document