When trimming a centrifugal pump impeller can save energy and increase flow rate

This paper presents a large eddy simulation of a centrifugal pump impeller during a transient condition. The flow rate is sinusoidal and oscillates between 0.25Qd (Qd indicates design load) and 0.75Qd when the rotating speed is maintained. Research shows that in one period, the inlet flow rate will twice reach 0.5Qd, and among the impeller of one moment is a stall state, but the other is a non-stall state. In the process of flow development, the evolution of low-frequency pressure fluctuation shows an obviously sinusoidal form, whose frequency is insensitive to the monitoring position and equals to that of the flow rate. However, inside the impeller, the phase and amplitude in the stall passages lag behind more and are stronger than that in the non-stall passages. Meanwhile, the strongest region of the high-frequency pressure fluctuation appears in the stall passages at the transient rising stage. The second dominant frequency in stall passages is 2.5 times to that in non-stall passages. In addition, similar to the pressure fluctuation, the evolution of the low-frequency head shows a sinusoidal form, whose phase is lagging behind that by one-third of a period in the inlet flow rate.

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A Comparative Assessment of Spalart-Shur Rotation/Curvature Correction in RANS Simulations in a Centrifugal Pump Impeller

Mathematical Problems in Engineering ◽

10.1155/2014/342905 ◽

2014 ◽

Vol 2014 ◽

pp. 1-9 ◽

Cited By ~ 5

Author(s):

Ran Tao ◽

Ruofu Xiao ◽

Wei Yang ◽

Fujun Wang

Keyword(s):

Kinetic Energy ◽

Centrifugal Pump ◽

Flow Rate ◽

Comparative Assessment ◽

Turbulence Kinetic Energy ◽

Low Flow ◽

Pump Impeller ◽

Curvature Correction ◽

Centrifugal Pump Impeller ◽

Low Flow Rate

RANS simulation is widely used in the flow prediction of centrifugal pumps. Influenced by impeller rotation and streamline curvature, the eddy viscosity models with turbulence isotropy assumption are not accurate enough. In this study, Spalart-Shur rotation/curvature correction was applied on the SSTk-ωturbulence model. The comparative assessment of the correction was proceeded in the simulations of a centrifugal pump impeller. CFD results were compared with existing PIV and LDV data under the design and low flow rate off-design conditions. Results show the improvements of the simulation especially in the situation that turbulence strongly produced due to undesirable flow structures. Under the design condition, more reasonable turbulence kinetic energy contour was captured after correction. Under the low flow rate off-design condition, the prediction of turbulence kinetic energy and velocity distributions became much more accurate when using the corrected model. So, the rotation/curvature correction was proved effective in this study. And, it is also proved acceptable and recommended to use in the engineering simulations of centrifugal pump impellers.

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Effects of Near-Wall Vortices on Wall Shear Stress in a Centrifugal Pump Impeller

WSEAS TRANSACTIONS ON FLUID MECHANICS ◽

10.37394/232013.2021.16.5 ◽

2021 ◽

Vol 16 ◽

pp. 37-47

Author(s):

Salman Shahid ◽

Abdul Qader Hasan ◽

Sharul Sham Dol ◽

Mohamed S. Gadala ◽

Mohd Shiraz Aris

Keyword(s):

Centrifugal Pump ◽

Flow Rate ◽

Pressure Head ◽

Research Paper ◽

Shear Stresses ◽

Pump Impeller ◽

Wall Shear ◽

Pump Pressure ◽

Centrifugal Pump Impeller ◽

Near Wall

Boundary layer separation and vortex formation cause unappealing deterioration of pump pressure head. The purpose of this research paper is to correlate formation of vortices with near-wall shear stresses resulting in a loss of pump pressure head. This phenomenon is observed at the centrifugal pump impeller tip at various flow rates and impeller rotational velocities through CFD (Computational Fluid Dynamic) analysis. This research paper investigates internal flow in a shrouded centrifugal impeller that is modelled under design flow rate conditions using ANSYS Fluent as its simulation bases solving built-in Navier-Stokes equation, and 𝑘 − 𝜔 SST turbulence model under steady conditions. Numerical results revealed an increase in wall shear stresses with increasing flow rate ranging from 314.2 Pa to 595.60 Pa at increments that pulsate per flow rate. Flow characteristics, such as evolution of vortices and flow turbulence enhance wall shear stresses increasing the wall skin-friction remarkably leading towards a loss in pressure head. This paper analyzes the vortices and turbulence in flow structures with regards to their influence upon the impeller performance.

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Investigation of the Motion of Bubbles in a Centrifugal Pump Impeller

Journal of Fluids Engineering ◽

10.1115/1.4041230 ◽

2018 ◽

Vol 141 (3) ◽

Cited By ~ 11

Author(s):

Henrique Stel ◽

Edgar M. Ofuchi ◽

Renzo H. G. Sabino ◽

Felipe C. Ancajima ◽

Dalton Bertoldi ◽

...

Keyword(s):

Centrifugal Pump ◽

Flow Rate ◽

Liquid Flow ◽

Liquid Flow Rate ◽

Operating Conditions ◽

Impeller Speed ◽

Pump Impeller ◽

Pump Performance ◽

Liquid Flows ◽

Centrifugal Pump Impeller

Centrifugal pumps operate below their nominal capacity when handling gas–liquid flows. This problem is sensitive to many variables, such as the impeller speed and the liquid flow rate. Several works evaluate the effect of operating conditions in the pump performance, but few bring information about the associated gas–liquid flow dynamics. Studying the gas phase behavior, however, can help understanding why the pump performance is degraded depending on the operating condition. In this context, this paper presents a numerical and experimental study of the motion of bubbles in a centrifugal pump impeller. The casing and the impeller of a commercial pump were replaced by transparent components to allow evaluating the bubbles' trajectories through high-speed photography. The bubble motion was also evaluated with a numerical particle-tracking method. A good agreement between both approaches was found. The numerical model is explored to evaluate how the bubble trajectories are affected by variables such as the bubble diameter and the liquid flow rate. Results show that the displacement of bubbles in the impeller is hindered by an increase of their diameter and impeller speed but facilitated by an increase of the liquid flow rate. A force analysis to support understanding the pattern of the bubble trajectories was provided. This analysis should enlighten the readers about the dynamics leading to bubble coalescence inside an impeller channel, which is the main reason behind the performance degradation that pumps experience when operating with gas–liquid flows.

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The PIV Measurements on the Flow Fields in an Unshrouded Centrifugal Pump

Volume 1 ◽

10.1115/esda2004-58565 ◽

2004 ◽

Author(s):

Chao Liu ◽

Fangping Tang ◽

Sun Sun ◽

Li Cheng ◽

Jiren Zhou

Keyword(s):

Flow Field ◽

Centrifugal Pump ◽

Flow Rate ◽

Flow Fields ◽

Pressure Side ◽

Pump Impeller ◽

Lower Velocity ◽

Piv Measurements ◽

Velocity Zone ◽

Centrifugal Pump Impeller

PIV was applied to the measurements of flow field in an unshrouded centrifugal pump impeller. Three windows were selected for the measurements. Three operation points of the pump were taken during the measuring. The ratios (Q/QBEP) of the flow rate for measuring are 0.6, 1.0, and 1.4, respectively. The velocity distributions in blade-to-blade passages obtained at different windows give the evidence that the velocity distributions are asymmetric even under the design operation point. A lower velocity zone existed at middle of blade-to-blades passages near the pressure-side of the blade.

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Analisis Kinerja Pompa Sentrifugal pada Variasi Trim Diameter Menggunakan Simulasi Numerik

Jurnal Rekayasa Mesin ◽

10.21776/ub.jrm.2021.012.02.23 ◽

2021 ◽

Vol 12 (2) ◽

pp. 467-474

Author(s):

Joko Waluyo ◽

◽

Kevin Mahardhika ◽

Rahmat Waluyo

Keyword(s):

Numerical Simulation ◽

Centrifugal Pump ◽

Flow Rate ◽

Performance Prediction ◽

Blade Angle ◽

Pump Impeller ◽

Pump Performance ◽

Blade Passage ◽

Dimension Ratio ◽

Centrifugal Pump Impeller

Diameter trimming is one of the most common modification on centrifugal pump impeller aimed to keep conformity between pump performance and required head and flow rate. In its application, centrifugal pump performance with trimmed diameter could be predicted by using affinity equations which based on geometrical similarity between pre- and post-trimming impeller. However, diameter trimming also alter the dimension ratio in blade passage which prompt further investigation on performance prediction of pump with trimmed impeller diameter. This research is carried out by using numerical simulation to analyze performance of pump with trimmed impeller diameter. The simulation is conducted on radial-type centrifugal pump with impeller diameter 105 mm, inlet blade angle 200, outlet blade angle 280, and operating on mass flow rate 1.5 kg/s at rotational speed 2800 rpm. RNG k-e model is used to model turbulence while trimmed diameter values are 100 mm and 95 mm. Results indicate that there is significant differences on head and consumed power between predicted value by simulation and predicted value obtained by employing affinity equations.

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