scholarly journals Dynamic Instability Analysis of a Double-Blade Centrifugal Pump

2021 ◽  
Vol 11 (17) ◽  
pp. 8180
Author(s):  
Denghao Wu ◽  
Songbao Yao ◽  
Renyong Lin ◽  
Yun Ren ◽  
Peijian Zhou ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Dynamic Instability ◽  
Flow Instability ◽  
Design Feature ◽  
Internal Flow ◽  
Low Flow ◽  
Pressure Pulsations ◽  
Frequency Spectra ◽  
Rotor Stator Interaction ◽  
The Time Domain

The flow instability of a double-blade centrifugal pump is more serious due to its special design feature with two blades and large flow passages. The dynamic instabilities and pressure pulsations can affect the pump performance and operating lifetime. In the present study, a numerical investigation of unsteady flow and time variation of pressure within a complete double-blade centrifugal pump was carried out. The time domain and frequency domain of pressure pulsations were extracted at 16 monitoring locations covering the important regions to analyze the internal flow instabilities of the pump model. The frequency spectra of pressure pulsations were decomposed into Strouhal number dependent functions. This led to the conclusion that the blade passing frequency (BPF) related vibrations are exclusively flow-induced. Large vortices were observed in the flow passages of the pump at low flow rate. It is noted that high vorticity magnitude occurred in the vicinities of the blade trailing edge and tongue of the volute, due to the rotor-stator interaction between impeller and volute.

scholarly journals Effect of the staggered impeller on reducing unsteady pressure pulsations of a centrifugal pump

2021 ◽  
Author(s):  
Ning Zhang ◽  
Junxian Jiang ◽  
Xiaokai Liu ◽  
Bo Gao
Keyword(s):  
Centrifugal Pump ◽  
Internal Flow ◽  
Simulation Method ◽  
Low Noise ◽  
Stable Operation ◽  
Pump Efficiency ◽  
Pressure Pulsations ◽  
Pump Design ◽  
Pump Head ◽  
Rotor Stator Interaction

Abstract High pressure pulsations excited by rotor stator interaction is always focused in pumps, especially for its control considering the stable operation. In the current research, a special staggered impeller is proposed to reduce intense pressure pulsations of a centrifugal pump with ns=69 based on alleviating rotor stator interaction. The numerical simulation method is conducted to illustrate the influence of staggered impeller on the pump performance and pressure pulsations, and three typical flow rates (0.8ФN-1.2ФN) are simulated. Results show that the staggered impeller will lead to the pump head increasing, and at the design working condition, the increment reaches about 3% compared with the original impeller. Meanwhile, the pump efficiency is little affected by the staggered impeller, which is almost identical with the original impeller. From comparison of pressure spectra at twenty monitoring points around the impeller outlet, it is validated that the staggered impeller contributes significantly to decreasing pressure pulsations at the concerned working conditions. At the blade passing frequency, the averaged reduction of twenty points reaches 89% by using the staggered impeller at 1.0ФN. The reduction reaches to 90%, 80% at 0.8ФN, 1.2ФN respectively. Caused by the rib within the staggered impeller, the internal flow field in the blade channel will be affected. Finally, it is concluded that the proposed staggered impeller surely has a significant effect on alleviating intense pressure pulsation of the model pump, which is very promising during the low noise pump design considering its feasibility for manufacturing.

scholarly journals Numerical Study on the Influence of Inlet Guide Vanes on the Internal Flow Characteristics of Centrifugal Pump

Processes ◽  
2020 ◽  
Vol 8 (1) ◽  
pp. 122 ◽  
Author(s):  
Peifeng Lin ◽  
Yongzheng Li ◽  
Wenbin Xu ◽  
Hui Chen ◽  
Zuchao Zhu
Keyword(s):  
Centrifugal Pump ◽  
Numerical Study ◽  
Flow Characteristics ◽  
Internal Flow ◽  
Low Flow ◽  
Hydraulic Loss ◽  
Inlet Pipe ◽  
Monitoring Point ◽  
Guide Vanes ◽  
Sst Turbulence Model

In order to make the centrifugal pump run efficiently and stably under various working conditions, the influences of the incoming vortex flow in the inlet pipe on the main flow in the impeller is studied numerically, based on the k − ω SST turbulence model. Some guide vanes with different offset angle were added to change the statistical characteristic of the internal flow in the inlet pipe of the centrifugal pump. Both contour distributions of internal flow and statistical results of external performance are obtained and analyzed. The results show that the existence of vanes can divide the large vortex because of the reversed flow from the rotating impeller at low flow rate conditions into small vortices, which are easier to dissipate, make the velocity and pressure distribution more uniform, improve the stability of the flow in the impeller, reduce the hydraulic loss, and improve the hydraulic performance of the pump. The pump with vanes of offset angle 25° has a small pressure pulsation amplitude at each monitoring point. Comparing with the performance of the original pump, the head increased by around 2% and efficiency increased by around 2.5% of the pump with vanes of offset angle 25°.

304 3-D Simulation of internal flow in Screw-Type Centrifugal Pump at Low Flow Rate

2000 ◽  
Vol 005.2 (0) ◽  
pp. 75-76
Author(s):  
Yasushi TATEBAYASHI ◽  
Kazuhiro TANAKA ◽  
Masamichi IINO
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Internal Flow ◽  
Low Flow ◽  
Low Flow Rate

Study of Pressure Pulsations in a Francis Turbine Designed for Frequent Start-Stop

2021 ◽  
pp. 1-24
Author(s):  
Chirag Trivedi
Keyword(s):  
Energy Demand ◽  
High Amplitude ◽  
Low Flow ◽  
Francis Turbine ◽  
Pressure Pulsations ◽  
High Rotational Speed ◽  
Rotor Stator Interaction ◽  
Efficient Option ◽  
High Flexibility ◽  
The Hill

Abstract The energy market aims for high flexibility that allows guaranteed power to the consumers with minimum carbon footprint. Over the last three decades, hydropower has been a reliable and an efficient option to meet the fluctuating energy demand as it allows high-ramping rate and quick start-stop. However, such critical operations bring certain challenges for hydro turbines, i.e., high-amplitude stochastic loading and the fatigue. Credible investigation of unsteady pressure pulsations and their signature is important to understand the consequences. The present work aims to study pressure pulsations in a model Francis turbine, which is designed for the frequent start-stop operations. A total of 112 numerical simulations, across the hill diagram, are conducted. Pressure pulsations in the vaneless space, blade channels and draft tube are investigated. The results show distinct patterns of rotor-stator interaction frequencies in the turbine. In the regions of high rotational speed and low flow rate, stochastic pulsations are predominant.

Influence of U-tube type casing treatment on pressure fluctuations of a centrifugal pump at low flow conditions

2021 ◽  
pp. 2150205
Author(s):  
Yuan Li ◽  
Hua Chen ◽  
Xiangjun Li ◽  
Minghe Jiang ◽  
Guinian Wang
Keyword(s):  
Centrifugal Pump ◽  
Test Performance ◽  
Pressure Fluctuations ◽  
Leading Edge ◽  
Radial Force ◽  
Low Flow ◽  
Pressure Pulsations ◽  
Casing Treatment ◽  
Tube Type ◽  
Pump Pressure

The existence of pressure pulsations greatly increases the vibration and noise of pumps and harms their service life. In this paper, a casing treatment was employed to explore its impact on the pressure pulsations. A U-tube type groove was created at the inlet end-wall of a centrifugal pump and front cover of the impeller to connect the impeller with the inlet pipe by passing impeller leading edge. An unsteady numerical investigation was launched of the pump with and without this casing treatment, to study its influence on the pressure pulsations inside the pump and the mechanisms behind. The numerical results of the pump without casing treatment was first compared with the test performance of the pump to validate the numerical method, and gave excellent agreements with the test results. The CFD results also showed that the casing treatment increases the head coefficient and efficiency of the pump. Pressure pulsations at a reduced mass flow condition were studied by monitoring unsteady pressure signals generated by the CFD at various locations inside the pump. A Fast Fourier transform (FFT) was performed on the signals. The pump employs a double tongues volute with each tongue covering 180[Formula: see text] circumference. However, the two tongues are not identical with regard to the discharge of the pump. These geometric features of the volute and the pump’s operating condition generate several pressure pulsations in the frequencies of [Formula: see text], [Formula: see text], [Formula: see text] in the original pump. Due to the circumferential unifying capability of the casing treatment and its improvement to the impeller flow, these pulsations at impeller inlet are weakened or disappear when the U-tube is present. The pressure pulsation inside the impeller is less affected by the treatment. The [Formula: see text] pulsation at volute tongues also decreases or disappears for the same reasons, but [Formula: see text] pulsation increases slightly and this is due to the improved pressure recovery in the volute by the treatment which increases the pressure difference across one of the volute tongues. The unsteady radial force of the impeller exerting on journal bearings becomes more uniform and smaller when the casing treatment is employed.

Analysis of the Pressure Pulsation and Vibration in a Low-Specific-Speed Centrifugal Pump

2020 ◽  
Vol 143 (2) ◽  
Author(s):  
Baoling Cui ◽  
Yingbin Zhang ◽  
Yakun Huang
Keyword(s):  
Centrifugal Pump ◽  
Flow Rate ◽  
Vortex Core ◽  
Pressure Pulsation ◽  
Radial Force ◽  
Design Flow ◽  
Low Flow ◽  
Pressure Pulsations ◽  
Low Specific Speed ◽  
Specific Speed

Abstract Unsteady pressure pulsation and fluid force induced by flow instabilities in the centrifugal pump is an important cause of vibration, which is detrimental to the safe operation of the pump. In this study, we numerically investigated the pressure pulsation and radial force in a low-specific-speed centrifugal pump by using the detached-eddy simulation method. We also performed a vibration displacement experiment on the shaft of the centrifugal pump. The vortex identification method was introduced to clarify the internal correlation between unsteady flow structures with pressure pulsations. The results showed that the pressure pulsations at the impeller outlet were closely associated with the periodic vortex shedding from the blade pressure surface. The rotor–stator interaction between a relatively big trailing vortex core and volute tongue generated larger pressure pulsation and radial force in the pump at a low flow rate. Under a large flow rate, the trailing vortex core was easily broken and dispersed, and this resulted in smaller pressure pulsation and radial force compared with that at a low flow rate. Under the design flow rate, the pressure pulsation intensity and the radial force in the impeller were smaller than that under the off-design flow rate. Compared with the spectra between the radial force on the impeller and radial displacement on the shaft, they both presented higher amplitude at the shaft frequency. The vibration of the pump shaft was closely related to the radial force on the impeller.

scholarly journals Improvement of Internal Flow Performance of a Centrifugal Pump-As-Turbine (PAT) by Impeller Geometric Optimization

Mathematics ◽  
2020 ◽  
Vol 8 (10) ◽  
pp. 1714
Author(s):  
Jian Xu ◽  
Longyan Wang ◽  
Stephen Ntiri Asomani ◽  
Wei Luo ◽  
Rong Lu
Keyword(s):  
Centrifugal Pump ◽  
Pressure Pulsation ◽  
Internal Flow ◽  
Geometric Optimization ◽  
Numerical Results ◽  
Operating Conditions ◽  
Maximum Efficiency ◽  
Stable Operation ◽  
Operating Range ◽  
Rotor Stator Interaction

Rotor-stator interaction (RSI) in the centrifugal pump-as-turbine (PAT) is a significant source of high amplitude of the pressure pulsation and the flow-induced vibration, which is detrimental to the stable operation of PAT. It is therefore imperative to analyze the rotor-stator interaction, which can subsequently be used as a guideline for reducing the output of PAT noise, vibration and cavitation. In addition, it is important for a PAT to have a wide operating range preferably at maximum efficiency. In order to broaden the operating range, this work proposes a multi-condition optimization scheme based on numerical simulations to improve the performance of a centrifugal PAT. In this paper, the optimization of PAT impeller design variables (b2, β1, β2 and z) was investigated to shed light upon its influence on the output efficiency and its internal flow characteristics. Thus, the aim of the study is to examine the unsteady pressure pulsation distributions within the PAT flow zones as a result of the impeller geometric optimization. The numerical results of the baseline model are validated by the experimental test for numerical accuracy of the PAT. The optimized efficiencies based on three operating conditions (1.0Qd, 1.2Qd, and 1.4Qd) were maximally increased by 13.1%, 8.67% and 10.62%, respectively. The numerical results show that for the distribution of PAT pressure pulsations, the RSI is the main controlling factor where the dominant frequencies were the blade passing frequency (BPF) and its harmonics. In addition, among the three selected optimum cases, the optimized case C model exhibited the highest level of pressure pulsation amplitudes, while optimized case B reported the lowest level of pressure pulsation.

scholarly journals Investigation of unsteady flow in a centrifugal pump at low flow rate

2016 ◽  
Vol 8 (12) ◽  
pp. 168781401668215 ◽  
Author(s):  
Yi Li ◽  
Xiaojun Li ◽  
Zuchao Zhu ◽  
Fengqin Li
Keyword(s):  
Unsteady Flow ◽  
Centrifugal Pump ◽  
Flow Rate ◽  
Internal Flow ◽  
Low Flow ◽  
Experimental Result ◽  
Vortical Structures ◽  
Visualization Experiment ◽  
Rate Ratios ◽  
Low Flow Rate

Due to the characteristics of unsteady flow in the centrifugal pump at low flow rate is not revealed well, a simulation of the internal flow at different flow rates is carried out with renormalization group k–ε turbulence model and multiple reference frame. For analyzing the influence of flow rate, ratios of flow rate ( Q/ Qd) are set to 0.1, 0.3, 0.6, and 1.0 at this study. The hydraulic performance of the centrifugal pump obtained by numerical calculation has matched well with the corresponding experimental result. From the characteristics of the internal flow captured by the numerical simulation, it can be seen that backflow occurs in the inlet of impeller at low flow rate, which prevents fluid discharging into impeller passages and leads to vortical structures in suction region. With further decrease in flow rate, the strength of backflow has been intensified, and the number of vortex has significantly increased. A visualization experiment of the backflow evolution in suction pipe is carried out to validate the unsteady simulated results. Results show that the prerotation is an important factor for the deterioration of centrifugal pump performance.

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