scholarly journals Pressure Fluctuation and Flow Characteristics in a Two-Stage Double-Suction Centrifugal Pump

Symmetry ◽  
2019 ◽  
Vol 11 (1) ◽  
pp. 65 ◽  
Author(s):  
Zhicong Wei ◽  
Wei Yang ◽  
Ruofu Xiao
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Rotation Period ◽  
Flow Characteristics ◽  
Load Condition ◽  
Flow Distribution ◽  
Leading Edge ◽  
Rotation Frequency ◽  
Two Stage

Pressure fluctuation is the primary factor that affects the stability of turbomachines. The goal of the present work is to explore the propagation of pressure fluctuations in a two-stage double-suction centrifugal pump. The pressure fluctuation characteristics of each component of a two-stage double-suction centrifugal pump are simulated under four typical flow rates based on the SST k-ω turbulence model. It is shown that the pressure fluctuation frequency at blade passing frequency and its first harmonic is the same at the suction chamber, the leading edge, and the middle of the first-stage impeller, which is different from the rotor–stator interaction. Moreover, the uneven impeller inlet flow distribution will produce fluctuations with rotation frequency and its harmonics at the leading edge of the impellers in both stages. Finally, broadband frequency is found at the trailing edge of the impellers in both stages associated with the first harmonic of the rotation frequency, especially under the part load condition. The large size backflow vortex appears in the blade flow channel leading to the low-pressure zone between the impeller, the tongue, and the start of the partition. That is why the pressure drops significantly twice in one rotation period when the blades pass through the tongue and the start of the partition.

scholarly journals Experimental Investigation on Influence of Relative Positions Between Diffuser and Volute on Pressure Fluctuation at the Outlet of a Centrifugal Pump

2016 ◽  
Author(s):  
Wenjie Wang ◽  
Shouqi Yuan ◽  
Ji Pei ◽  
Giorgio Pavesi ◽  
Yandong Gu
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Load Condition ◽  
Dominant Frequency ◽  
Azimuthal Position ◽  
Open Test ◽  
Spectrum Density ◽  
Fluctuation Amplitude ◽  
Large Flow

To investigate the influence of relative positions between a radial diffuser and an annular volute on the unsteady pressure at the centrifugal pump outlet, experiment tests were carried out with five positions between the diffuser and volute in an open test rig. Statistical and frequency spectrum analyses were carried out to obtain the pressure fluctuation amplitude range and the frequency domain respectively. The results showed that the relative position has greater influence on the pressure at large flow rate than at part load condition. The dominant frequency and the Power Spectrum Density (PSD) values are affected by diffuser azimuthal position and the harmonic frequencies are determined by number of blades and vanes. The investigation can give a reference to optimize the relative angle between diffuser and volute to reduce the pressure fluctuations.

Cavitation-Vortex-Pressure Fluctuation Interaction in a Centrifugal Pump Using Bubble Rotation Modified Cavitation Model Under Partial Load

2020 ◽  
Vol 142 (5) ◽  
Author(s):  
Weihua Sun ◽  
Lei Tan
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Volume Fraction ◽  
Great Influence ◽  
Rotation Period ◽  
Rotation Frequency ◽  
Relative Vorticity ◽  
Calculation Model ◽  
Cavitation Model ◽  
Partial Load

Abstract Cavitation is a complicated phenomenon in the centrifugal pump. In this work, the improved unsteady calculation model based on bubble-rotation-based Zwart–Gerber–Belamri (BRZGB) cavitation model is used to investigate the cavitation-vortex-pressure fluctuation interaction in a centrifugal pump under partial load with experimental validation. Spatial–temporal evolution of cavitation can be classified into three stages: developing stage, shedding stage, and collapsing stage. The cavitation evolution period is found as 1/4T (T is impeller rotation period), corresponding to the frequency 4fi (fi is impeller rotation frequency). On the analysis of the relative vorticity transport equation, it is revealed that the cavity is stretched by the relative vortex stretching term (RVS) and developed by the relative vortex dilation term (RVD), and they have great influence on the cavity shedding. The peak value of pressure fluctuation intensity occurs near the vapor–liquid interface at cavity rear, and shifts downstream with the cavitation development. The hysteresis between the vapor volume fraction, vorticity, and pressure fluctuation is observed, and the variation of vapor volume fraction is the source of cavitation-vortex-pressure interaction.

Influence of T-shape tip clearance on performance of a mixed-flow pump

2017 ◽  
Vol 232 (4) ◽  
pp. 386-396 ◽  
Author(s):  
Tan Lei ◽  
Xie Zhifeng ◽  
Liu Yabin ◽  
Hao Yue ◽  
Xu Yun
Keyword(s):  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Rotation Frequency ◽  
Tip Clearance ◽  
Mixed Flow ◽  
Impeller Blade ◽  
Movement Trajectories ◽  
Blade Thickness ◽  
Flow Pump

Influence of original and T-shape blade end on performance of a mixed-flow pump is investigated by using experimental measurement and numerical simulation. The new proposed T-shape blade end is formed at 95%–100% blade height with a linear increase of blade thickness. In comparison with original blade end, the efficiency of pump with T-shape blade end increases by 1.86%, and the leakage flow decreases by 15.95%. Space streamlines across the blade tip clearance can be divided into three beams with different movement trajectories, and the swirl motions of streamlines directly correspond to the swirling strength. The highest amplitude of pressure fluctuation appears at the blade leading edge along the tip clearance. In comparison with original blade end, the highest amplitude of pressure fluctuation for T-shape blade end decreases by 27.45%. The dominant frequencies of the pressure fluctuations in tip clearance region for original blade end and T-shape blade end are both five times of the axis rotation frequency, corresponding to the impeller blade number of five.

Numerical Investigation of Pressure Fluctuation and Rotor-Stator Interaction in a Multistage Centrifugal Pump

2013 ◽  
Author(s):  
Ling Zhou ◽  
Weidong Shi ◽  
Ling Bai ◽  
Weigang Lu ◽  
Wei Li
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Maximum Amplitude ◽  
Leading Edge ◽  
Pulsation Period ◽  
Impeller Blade ◽  
Blade Passage ◽  
Multistage Centrifugal Pump ◽  
Sst Turbulence Model

The unsteady flow field in a multistage centrifugal pump was simulated with ANSYS-CFX code based on transient rotor-stator method, and Shear Stress Transport (SST) turbulence model to investigate the pressure fluctuations in the three stages passages. With the Fast Fourier Transform (FFT) analysis, the pressure fluctuations and frequency domains are analyzed and compared between stages. The numerical results show that the pressure fluctuates at the blade passage frequency, and the maximum amplitude of blade passage frequency occurs in the region from the rotor to the stator when the impeller blade gets close to the diffuser vane leading edge. The pressure pulsation period mainly associated with the number of impeller blades, but the influence gradually reduce when the fluids flow into the diffuser. The flow patterns and pressure fluctuation between stags are similar.

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.

Effects of short blades on performance and inner flow characteristics of a low-specific-speed centrifugal pump

2017 ◽  
Vol 231 (4) ◽  
pp. 290-302 ◽  
Author(s):  
Can Kang ◽  
Ning Mao ◽  
Chen Pan ◽  
Yang Zhu ◽  
Bing Li
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Low Flow ◽  
Back Surface ◽  
Flow Rates ◽  
Pump Operation ◽  
Low Specific Speed ◽  
Specific Speed

A low-specific-speed centrifugal pump equipped with long and short blades is studied. Emphasis is placed on the pump performance and inner flow characteristics at low flow rates. Each short blade is intentionally shifted towards the back surface of the neighboring long blade, and the outlet parts of the short blades are uniformly shortened. Unsteady numerical simulation is conducted to disclose inner flow patterns associated with the modified design. Thereby, a comparison is enabled between the two schemes featured by different short blades. Both practical operation data and numerical results support that the deviation and cutting of the short blades can eliminate the positive slope of pump head curve at low flow rates. Therefore, the modification of short blades improves the pump operation stability. Due to the shortening of the outlet parts of the short blades, velocity distributions between impeller outlet and radial diffuser inlet exhibit explicitly altered circumferential flow periodicity. Pressure fluctuations in the radial diffuser are complex in terms of diversified periodicity and amplitudes. Flow rate influences pressure fluctuations in the radial diffuser considerably. As flow rate decreases, the regularity of the orbit of hydraulic loads exerted upon the impeller collapses while hydraulic loads exerted upon the short blades remain circumferentially periodic.

Influence of wall roughness on the static performance and pressure fluctuation characteristics of a double-suction centrifugal pump

2018 ◽  
Vol 232 (7) ◽  
pp. 826-840 ◽  
Author(s):  
Zhifeng Yao ◽  
Min Yang ◽  
Ruofu Xiao ◽  
Fujun Wang
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Fluctuations ◽  
Design Flow ◽  
Experimental Investigations ◽  
Wall Roughness ◽  
Detached Eddy Simulation ◽  
Centrifugal Pumps ◽  
Eddy Simulation ◽  
Static Performance

The unsteady flow field and pressure fluctuations in double-suction centrifugal pumps are greatly affected by the wall roughness of internal surfaces. To determine the wall roughness effect, numerical and experimental investigations were carried out. Three impeller schemes for different wall roughness were solved using detached eddy simulation, and the performance and pressure fluctuations resolved by detached eddy simulation were compared with the experimental data. The results show that the effects of wall roughness on the static performance of a pump are remarkable. The head and efficiency of the tested double-suction centrifugal pump are raised by 2.53% and 6.60% respectively as the wall roughness is reduced by means of sand blasting and coating treatments. The detached eddy simulation method has been proven to be accurate for the prediction of the head and efficiency of the double-suction centrifugal pump with roughness effects. The influence of the roughness on pressure fluctuation is greatly dependent on the location relative to the volute tongue region. For locations close to the volute tongue, the peak-to-peak value of the pressure fluctuations of a wall roughness of Ra = 0.10 mm may be 23.27% larger than the case where Ra = 0.02 mm at design flow rate.

Numerical investigation on vibration and pressure fluctuation characteristics in a centrifugal pump under low flow rate

2020 ◽  
pp. 095440622096972
Author(s):  
Like Wang ◽  
Jinling Lu ◽  
Weili Liao ◽  
Pengcheng Guo ◽  
Guojun Zhu ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Reverse Flow ◽  
Leading Edge ◽  
Low Flow ◽  
Main Shaft ◽  
Unstable Flow ◽  
Tip Leakage ◽  
Flow Vortex ◽  
Tip Separation Vortex

Vibration characteristic is an important factor in evaluating operation stability of centrifugal pump. The vibration of main shaft was measured using a laser vibrometer, internal flow field was simulated via the shear stress transport turbulence model, and distribution law of vibration and pressure fluctuation in the impeller were analysed to explore the induction factor of vibration and the inherent relationship with pressure fluctuation in a semi-open centrifugal pump under low flow rate condition. Results of the numerical simulation are consistent with the experimental data. In addition to rotation frequency caused by impeller rotation, vibration frequency also includes characteristic frequency with high amplitude induced by unstable flow. The complex vortex in the impeller is composed of tip leakage vortex (TLV), reverse flow vortex, passage vortex and tip separation vortex. The primary tip leakage vortex (PTLV) formed by the streamline spills from 0 to 0.2λ where λ is the dimensionless distance from leading edge to trailing edge collides with tip leakage flow, the leading edge overflow and reverse flow vortex at the frequency of 1.6 fn ( fn is the rotating frequency) and 2.2 fn appear, respectively. The tip separation vortex formed in the tip clearance induced a frequency of 1.2 fn. The frequency of unstable flow phenomenon was consistent with the vibration frequency of main shaft, which induced the vibration of centrifugal pump.

scholarly journals Pressure fluctuation–vortex interaction in an ultra-low specific-speed centrifugal pump

2018 ◽  
Vol 38 (2) ◽  
pp. 527-543 ◽  
Author(s):  
Cong Wang ◽  
Yongxue Zhang ◽  
Zhiwei Li ◽  
Ao Xu ◽  
Chang Xu ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Leading Edge ◽  
Experimental Results ◽  
Vortex Interaction ◽  
Trailing Edge ◽  
Pressure Surface ◽  
Baroclinic Torque ◽  
Low Specific Speed ◽  
Specific Speed

To provide a comprehensive understanding of the pressure fluctuation–vortex interaction in non-cavitation and cavitation flow, in this article, the unsteady flow in an ultra-low specific-speed centrifugal pump was investigated by numerical simulation. The uncertainty of the numerical framework with three sets of successively refined mesh was verified and validated by a level of 1% of the experimental results. Then, the unsteady results indicate that the features of the internal flow and the pressure fluctuation were accurately captured in accordance with the closed-loop experimental results. The detailed pressure fluctuation at 16 monitoring points and the monitoring of the vorticity suggest that some inconsistent transient phenomena in frequency spectrums show strong correlation with the evolution of vortex, such as abnormal increasing amplitudes at the monitoring points near to the leading edge on the suction surface and the trailing edge on the pressure surface in the case of lower pressurization capacity of impeller after cavitation. Further analysis applies the relative vortex transport equation to intuitionally illustrate the pressure fluctuation–vortex interaction by the contribution of baroclinic torque, viscous diffusion and vortex convection terms. It reveals that the effect of viscous diffusion is weak when the Reynolds number is much greater than 1. Pressure fluctuation amplitude enlarges on the suction side of blade near to the leading edge due to the baroclinic torque in cavitation regions, whereas the abnormal increase of pressure fluctuation after cavitation on the pressure surface of blade approaching the trailing edge results from the vortex convection during vortices moving downstream with the decrease of available net positive suction head at the same instance.

scholarly journals Flow Characteristics in Volute of a Double-Suction Centrifugal Pump with Different Impeller Arrangements

Energies ◽  
2019 ◽  
Vol 12 (4) ◽  
pp. 669 ◽  
Author(s):  
Yu Song ◽  
Honggang Fan ◽  
Wei Zhang ◽  
Zhifeng Xie
Keyword(s):  
Centrifugal Pump ◽  
High Efficiency ◽  
Pressure Fluctuations ◽  
Flow Characteristics ◽  
Weighted Average ◽  
Complex Flow ◽  
Suction Pump ◽  
Impeller Outlet ◽  
Large Flow ◽  
Dominant Frequencies

As an important type of centrifugal pump, the double-suction pump has been widely used due to its high efficiency region and large flow rate. In the present study, the complex flow in volute of a double-suction centrifugal pump is investigated by numerical simulation using a re-normalization group (RNG) k-ε model with experimental validation. Axial flows are observed in volute near the impeller outlet and compared with four staggered angles. The net area-weighted average axial velocities decrease as the staggered angle increases. The axial flows are mainly caused by the different circumferential pressure distribution at the twin impeller outlet. The dominant frequencies of the axial velocities for different staggered angles are fBP and its harmonic. The pressure fluctuations in most regions of the volute are obtained by superimposing the pressure generated by the two impellers.

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