Numerical study on the cavitation phenomenon for the head drop and unsteady bubble patterns with a difference in the incidence angle of a mixed-flow pump

In this study, two types of mixed-flow pump models exhibiting different suction performances were investigated to understand the cavitation characteristics of head drop gradients due to the decrease in inlet pressure. Both models were designed with the same specifications except for the shroud inlet blade angle and inlet radius which directly affect the incidence angle. The steady- and unsteady-state analyses were performed using ANSYS CFX, and the results of both models were compared. Bubble generation and patterns were systemically represented at the design flow rate to observe their influence on suction performance. Furthermore, experimental tests were performed to validate the numerical results. From the results, the head drop gradient can determine the suction performance of mixed-flow pumps. The amount and shape of the bubbles concerning the suction performance of a mixed-flow pump exhibit significant differences with the changes in time and inlet pressure. The patterns of generated bubble are not stable even for each blade.

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A Numerical Study on the Improvement of Suction Performance and Hydraulic Efficiency for a Mixed-Flow Pump Impeller

Mathematical Problems in Engineering ◽

10.1155/2014/269483 ◽

2014 ◽

Vol 2014 ◽

pp. 1-17 ◽

Cited By ~ 6

Author(s):

Sung Kim ◽

Kyoung-Yong Lee ◽

Jin-Hyuk Kim ◽

Young-Seok Choi

Keyword(s):

Numerical Analysis ◽

Numerical Study ◽

Incidence Angle ◽

Meridional Plane ◽

Total Efficiency ◽

Hydraulic Efficiency ◽

Mixed Flow ◽

Design Variables ◽

Suction Performance ◽

Flow Pump

This paper describes a numerical study on the improvement of suction performance and hydraulic efficiency of a mixed-flow pump by impellers. The design of these impellers was optimized using a commercial CFD (computational fluid dynamics) code and DOE (design of experiments). The design variables of meridional plane and vane plane development were defined for impeller design. In DOE, variables of inlet part were selected as main design variables in meridional plane, and incidence angle was selected in vane plane development. The verification of the experiment sets that were generated by2kfactorial was done by numerical analysis. The objective functions were defined as the NPSHre (net positive suction head required), total efficiency, and total head of the impellers. The importance of the geometric design variables was analyzed using2kfactorial designs. The interaction between the NPSHre and total efficiency, according to the meridional plane and incidence angle, was discussed by analyzing the2kfactorial design results. The performance of optimally designed model was verified by experiments and numerical analysis and the reliability of the model was retained by comparison of numerical analysis and comparative analysis with the reference model.

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Effect of incidence angle on cavity blockage and flow stability in the net positive suction head drop of mixed-flow pumps

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406220973055 ◽

2020 ◽

pp. 095440622097305

Author(s):

Yong-In Kim ◽

Sung Kim ◽

Kyoung-Yong Lee ◽

Young-Seok Choi

Keyword(s):

Flow Pattern ◽

Flow Rate ◽

Pressure Fluctuation ◽

Incidence Angle ◽

Experimental Tests ◽

Design Flow ◽

Inlet Pressure ◽

Stable Flow ◽

Fft Analysis ◽

Design Flow Rate

The cavitation is an inevitable factor in pumps used in the whole industry, which is a major cause of energy loss and mechanical breakdown. In this study, the cavitation phenomena at the design flow rate were numerically analyzed for two pumps with different incidence angles. The design flow rate for both models was located near the best efficiency point (BEP). The incidence angle was determined with the impeller inlet diameter and the blade angle. A pump with a smaller incidence angle consistently showed a stable flow pattern as the inlet pressure decreased, whereas a pump with a larger incidence angle contained non-uniform flow streamlines despite a very small amount of the generated cavities. The flow pattern at the impeller inlet was handled by the shape and thickness of the generated cavities which could act as an additional blockage in the pumps. The inception and growth of the cavity with a decrease of inlet pressure were also inferred, which was specifically quantified as the blockage ratio. A pump with a larger incidence angle performed poor cavitation characteristics and obtained the pressure fluctuation and cavity oscillation. The magnitude of pressure fluctuation was indicated using the fast Fourier transform (FFT) analysis. The experimental tests were performed on both pumps to validate the numerical results.

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Three-objective optimization of a mixed-flow pump impeller for improved suction performance and efficiency

Advances in Mechanical Engineering ◽

10.1177/1687814019898969 ◽

2019 ◽

Vol 11 (12) ◽

pp. 168781401989896 ◽

Cited By ~ 1

Author(s):

Sung Kim ◽

Yong-In Kim ◽

Jin-Hyuk Kim ◽

Young-Seok Choi

Keyword(s):

Design Optimization ◽

Design Flow ◽

Meridional Plane ◽

Angle Distribution ◽

Blade Angle ◽

Mixed Flow ◽

Pump Impeller ◽

Design Variables ◽

Suction Performance ◽

Flow Pump

In this article, design optimization was carried out to improve the suction performance and efficiency of a mixed-flow pump impeller. Commercial computational fluid dynamics code and a response surface method were used in the optimization to design a mixed-flow pump impeller. When it comes to a mixed-flow pump, the two main research objectives namely efficiency and suction performance tend to contradict. It is very important that the design technology improves the suction performance while maintaining high efficiency. Meridional plane and vane plane development variables were defined in the design of the impeller. The meridional plane expresses the shapes and sizes of the blades, while the vane plane development describes the impeller inlet and outlet angles as well as the blade angle distribution. The blade angle distribution of the impeller was designed using the traditional method by which inlet and outlet angles are connected smoothly. The surface response method was applied to the design variables of the impeller inlet part in this design optimization because they influence the performance of the mixed-flow pump. Objective functions were set to satisfy the total head at the design flow rate as well as to improve efficiency and suction performance. Design variables of the impeller inlet part of the mixed-flow pump and the changes in performance were analyzed in order to produce the optimal shape. The performance of the optimally designed shape was verified by numerical analysis, and the reliability of the test result was checked by comparative analysis against the reference model.

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Effect of Tip Clearance on Suction Performance at Different Flow Rates in a Mixed Flow Pump

Volume 1B, Symposia: Fluid Machinery; Fluid-Structure Interaction and Flow-Induced Noise in Industrial Applications; Flow Applications in Aerospace; Flow Manipulation and Active Control: Theory, Experiments and Implementation; Multiscale Methods for Multiphase Flow; Noninvasive Measurements in Single and Multiphase Flows ◽

10.1115/fedsm2014-21207 ◽

2014 ◽

Author(s):

Yo Han Jung ◽

Young Uk Min ◽

Jin Young Kim

Keyword(s):

Performance Test ◽

Stokes Equations ◽

Flow Characteristics ◽

Tip Clearance ◽

Low Flow ◽

Tip Leakage Flow ◽

Mixed Flow ◽

Flow Rates ◽

Suction Performance ◽

Flow Pump

This paper presents a numerical investigation of the effect of tip clearance on the suction performance and flow characteristics at different flow rates in a vertical mixed-flow pump. Numerical analyses were carried out by solving three-dimensional Reynolds-averaged Navier-Stokes equations. Steady computations were performed for three different tip clearances under noncavitating and cavitating conditions at design and off-design conditions. The pump performance test was performed for the mixed-flow pump and numerical results were validated by comparing the experimental data for a system characterized by the original tip clearance. It was shown that for large tip clearance, the head breakdown occurred earlier at the design and high flow rates. However, the head breakdown was quite delayed at low flow rate. This resulted from the cavitation structure caused by the tip leakage flow at different flow rates.

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Transient characteristics of internal flow fields of mixed-flow pump with different tip clearances under stall condition

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650920962250 ◽

2020 ◽

pp. 095765092096225

Author(s):

Leilei Ji ◽

Wei Li ◽

Weidong Shi ◽

Ramesh Agarwal

Keyword(s):

Swirling Flow ◽

Internal Flow ◽

Flow Fields ◽

Design Flow ◽

Tip Clearance ◽

Tip Leakage Flow ◽

Mixed Flow ◽

Transient Characteristics ◽

Initial Starting ◽

Flow Pump

This paper investigates the influence of different tip clearances on the transient characteristics of mixed-flow pump under stall condition. The instantaneous internal flow fields of mixed-flow pump with four tip clearances (0.2 mm, 0.5 mm, 0.8 mm and 1.1 mm) are explored by conducting unsteady time accurate simulations. Reynolds-averaged Navier-Stokes (RANS) equations are employed in the simulations and the results of computations are compared with experimental data. The results show that the pump head decreases by 22.1% and the pump efficiency drops by 13.9% at design flow condition when the impeller tip clearance increases from 0.2 mm to 1.1 mm. The swirling flow occurs in the inlet pipe of the mixed-flow pump with different tip clearances under stall condition, and the initial starting point of the swirling flow gets further away from the impeller inlet with increase in tip clearance because of increase in circumferential velocity and change in momentum of the tip leakage flow (TLF). The high turbulent eddy dissipation (TED) regions in the flow are attributed to the TLF, swirling flow, back flow and stall vortex, and their intensity are affected by the change in tip clearance. The oscillating trend of time domain distribution of TED enhances first and then decreases with increase in tip clearance and it exhibits a propagation feature under the effect of stall vortex, while most of the energy in the frequency domain remains concentrated in the low frequency part under stall condition.

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Diagonal Flow Pump Impeller With NACA65 Series Blade (Correction of Blade Geometry)

ASME-JSME-KSME 2011 Joint Fluids Engineering Conference: Volume 1, Symposia – Parts A, B, C, and D ◽

10.1115/ajk2011-22037 ◽

2011 ◽

Author(s):

Yoichi Kinoue ◽

Norimasa Shiomi ◽

Toshiaki Setoguchi ◽

Kazuhiro Sawamura ◽

Hideaki Maeda

Keyword(s):

Rotor Blade ◽

Design Flow ◽

Numerical Calculations ◽

Navier Stokes ◽

Minimum Pressure ◽

The One ◽

Suction Performance ◽

Flow Pump ◽

Better Than ◽

Blade Geometry

Using the design method based on the design for axial-flow type turbomachine, the diagonal flow pump impellers were designed for two cases of the centrifugal effect parameter a. In addition, three-dimensional Navier-Stokes numerical calculations for single-phase were conducted in order to examine the tendency of the suction performance as well as the head performance. The head increases from the NS calculation of the impeller are the same between for a = 0.4 and for a = 1.0 because major specification are the same between for a = 0.4 and for a = 1.0. For the minimum pressure on the rotor blade, however, there is a difference between for a = 0.4 and for a = 1.0. The value of minimum pressure for a = 0.4 is −324 kPa, whereas the value for a = 1.0 is −294 kPa. The blade geometry for a = 1.0 is better than the one for a = 0.4 in terms of the suction performance because the trough of the minimum pressure is shallower for a = 1.0 than a = 0.4. Furthermore, Navier-Stokes numerical calculations were also conducted for off-design flow rate. For all cases in this paper, the minimum pressure on the rotor blade occurred at both near the leading edge and near the tip on the suction side of the blade. In addition, for all cases in this paper, the blade geometry for a = 1.0 is better than the one for a = 0.4 in terms of the suction performance.

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Influence of tip leakage flow and inlet distortion flow on a mixed-flow pump with different tip clearances within the stall condition

Proceedings of the Institution of Mechanical Engineers Part A Journal of Power and Energy ◽

10.1177/0957650919863622 ◽

2019 ◽

Vol 234 (4) ◽

pp. 433-453 ◽

Cited By ~ 7

Author(s):

Leilei Ji ◽

Wei Li ◽

Weidong Shi

Keyword(s):

Internal Flow ◽

Energy Performance ◽

Rotating Stall ◽

Design Flow ◽

Tip Clearance ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Mixed Flow ◽

Tip Leakage ◽

Flow Pump

In order to investigate the effect of impeller tip clearance on internal flow fields and the rotating stall inception impacted by tip leakage vortex and inlet unsteady flow in a mixed-flow pump, mixed-flow pump models with tip clearances of 0.5 mm, 0.8 mm, and 1.1 mm were numerically calculated, and then the energy performance curves and internal flow structures were obtained and compared. The results show that the pump efficiency and the internal flow fields of numerical calculation are in good agreement with experimental results at design flow rate and near-stall condition. A portion of the positive slope segment appears in the energy performance curves under different tip clearances. The lowest head of the mixed-flow pump in the positive slope region decreases with the increase of the tip clearance while the highest head shows an opposite situation indicating that mixed-flow pumps are easier to stall under small tip clearance. At the design flow rate condition, the tip leakage vortex is relatively stable under different tip clearances and appears as a “snail shell” shape, whereas in rotating stall conditions, the “snail shell” shape disappear and the tip leakage flow on blade front forms a “flat” vortex structure. The inlet swirl flow not only affects the tip leakage flow in rotating stall conditions under different tip clearances, but also blocks the fluid from the inlet pipe. Under the circumstance of the same tip clearance, the main frequency amplitude of pressure pulsation coefficient gradually shifts away from blade passing frequency (96.67 Hz) to the axial frequency (24.17 Hz) when the pump operates in the stall condition.

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