scholarly journals Pressure fluctuation study in the stages of a multistage pump at best efficiency points under various operating speeds

2021 ◽  
Author(s):  
Dhanasekaran Arumugam ◽  
◽  
Kumaraswamy Sivasailam ◽  
Keyword(s):  
Pressure Fluctuation ◽  
High Amplitude ◽  
Uniform Pressure ◽  
Submersible Pump ◽  
Linear Variation ◽  
Centrifugal Pumps ◽  
Reliable Operation ◽  
Flow Induced Vibration ◽  
Amplitude Variation ◽  
Multistage Pump

The interaction between the rotor and stator is a major source of high amplitude pressure fluctuation and flow-induced vibration in multistage centrifugal pumps. The pressure fluctuation is detrimental to the reliable operation of pumps. The sensitivity of vibration is severe if the number of stages is more. In the present experimental study, a vertical multistage centrifugal submersible pump is used to measure the pressure fluctuation level at Best Efficiency Points (BEP) and to determine the influence of stage and operating speed on pressure fluctuation. For this purpose, pressure fluctuation signals were captured at the delivery side of the pump at BEP at various speed settings. The characteristics of pressure fluctuation at BEP at various operating speeds were studied with the help of spectra, i.e., in the frequency domain. The amplitude variation of pressure fluctuation with harmonics of vane passing frequency at stages were studied. Results have indicated that variation of pressure fluctuation with stage and speed exhibited a non-linear variation. In addition, such a pressure fluctuation study will be helpful to modify the design to obtain a uniform pressure distribution in the stages of a multistage pump.

Experimental Investigation on Pressure Fluctuation Reduction in a Double Suction Centrifugal Pump: Influence of Impeller Stagger and Blade Geometry

2020 ◽  
Vol 142 (4) ◽  
Author(s):  
Yongshun Zeng ◽  
Zhifeng Yao ◽  
Fujun Wang ◽  
Ruofu Xiao ◽  
Chenglian He
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
High Amplitude ◽  
Operating Conditions ◽  
Center Frequency ◽  
Centrifugal Pumps ◽  
Pump Impeller ◽  
Axial Forces ◽  
Large Peak ◽  
Blade Geometry

Abstract The reduction in pressure fluctuation can suppress noise, balance the radial and axial forces, and restrain the vibration level of a centrifugal pump. Impeller stagger and blade geometry influence the pressure fluctuation characteristics of double suction centrifugal pumps. In the present investigation, the pressure fluctuation characteristics of the baseline impeller, the staggered impeller, and the blade geometry modified impeller were investigated experimentally under design and off-design operating conditions. The frequency spectrum was analyzed by fast Fourier transform (FFT) and continuous wavelet transform (CWT) methods. The broadband frequencies are defined quantitatively and analyzed emphatically. The significant linear relationship between the center frequency of the broadband frequencies and the flowrate is discovered for the first time. The center frequency decreases as the flowrate increases. The linearity varies below and above the design flowrate. When the discrete frequencies are in range of the broadband frequencies, a high amplitude of pressure fluctuation occurs. This could explain the large peak-to-peak value of the pressure fluctuation at 1.24Qn, which may be due to the coincidence between broadband frequencies and the components at the frequencies fr and 2fr. Both the staggered impeller and the blade geometry modified impeller can reduce the level of pressure fluctuation; in particular, it is reduced to 35% and 13% compared to that of baseline impeller near the volute tongue region under the design flowrate, respectively. The staggered impeller and the blade geometry can obviously affect the decreasing slopes between the center frequencies and the flowrate.

scholarly journals A New Proposed Return Guide Vane for Compact Multistage Centrifugal Pumps

2013 ◽  
Vol 2013 ◽  
pp. 1-11 ◽  
Author(s):  
Qihua Zhang ◽  
Weidong Shi ◽  
Yan Xu ◽  
Xiongfa Gao ◽  
Chuan Wang ◽  
...  
Keyword(s):  
Water Flow ◽  
Pressure Fluctuation ◽  
Design Method ◽  
Guide Vane ◽  
Rotation Frequency ◽  
Pump Efficiency ◽  
Cyclic Symmetry ◽  
Centrifugal Pumps ◽  
Cfd Simulations ◽  
Multistage Pump

For widely used multistage centrifugal pumps, their former structures are so bulky that nowadays growing interest has been shifted to the development of more compact structures. Following this trend, a compact pump structure is provided and analysed. To maintain the pump’s pressure recovery, as well as to meet the water flow from the impeller, a circumferential twisted return guide vane (RGV) is proposed. To validate this design method, the instantaneous CFD simulations are performed to investigate the rotor-stator interventions. Within the impeller, the pressure fluctuation is cyclic symmetry, where the impeller frequency dominates. At the zone where flow leaves impeller for RGV, the pressure fluctuation is nonperiodic, the impeller frequency is major, and the rotation frequency is secondary. Within RGV, the periodic symmetric fluctuation is recovered, where the rotation frequency is governing. The fluctuation decreases from seven cycles within impeller to two cycles within RGV, indicating that the flow from impeller is well handled by RGV. To examine the pump’s performance, a prototype multistage pump is designed. The testing shows that the pump efficiency is 57.5%, and the stage head is 9 m, which is comparable to former multistage centrifugal pumps. And this design is more advantageous in developing compact multistage centrifugal pumps.

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.

Research on Characteristics of Fluid Exciting Force of Reactor Internals

2021 ◽  
Author(s):  
Zhipeng Feng ◽  
Liwen Deng ◽  
Xuan Huang ◽  
Pingchuan Shen ◽  
Shuai Liu ◽  
...  
Keyword(s):  
Pressure Fluctuation ◽  
Nuclear Reactor ◽  
Wide Band ◽  
Exciting Force ◽  
Design Stage ◽  
Response Analysis ◽  
Flow Induced Vibration ◽  
Analysis And Evaluation ◽  
Safety And Reliability ◽  
Force Characteristics

Abstract Flow-induced vibration is an important issue related to the safety and reliability of nuclear reactor, which need to be analyzed and evaluated in the design stage. In order to obtain the input loads and key parameters used in the calculation of flow-induced vibration of reactor vessel internals (RVIs) that need to satisfy the engineering requirements. The typical RVIs are selected as the research object, and the fluid exciting force characteristics are studied based on the computational fluid dynamics methods. The results show that the fluid exciting force acting on the RVIs is a wide-band stochastic process. For upper internal, the largest pressure fluctuation occurs at the guide tubes and support columns located near the outlet. Therefore, it is necessary to pay more attention to these guide tubes and support columns in response analysis. As for core barrel, the root mean square value of the pressure fluctuation changes drastically at the inlet and outlet location. For lower internal, the lower flow field of RVIs is relatively disordered, and its pressure fluctuation possesses irregular characteristics. Each component of lower internal need to be considered in analysis and evaluation.

Study on the Reduction of Pressure Fluctuation for a Double-Suction Centrifugal Pump With Staggered Blades

2018 ◽  
Author(s):  
Qian-qian Li ◽  
Da-zhuan Wu
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Cfd Simulation ◽  
Stokes Equations ◽  
Low Noise ◽  
Living Environment ◽  
Centrifugal Impeller ◽  
Fluctuation Analysis ◽  
Centrifugal Pumps ◽  
Vibration Performance

Due to the distinctive characteristic of massive flow rates, double-suction centrifugal pump has been extensively applied in lots of perspectives, such as drainage, irrigation, transportation projects and other hydraulic engineering realms. Nevertheless, the significance of the pressure fluctuation inside the double-suction centrifugal pump, which is getting more and more prominent under the soaring demands for low noise and comfortable living environment, could not be underestimated. Consequently, how to reduce the pressure fluctuation as far as possible and enhance the running stability of the pump is always the research hotspot. In this study, the double-suction centrifugal impeller with abominable vibration performance is redesigned to improve the internal flow and reduce the flow-induced noise. What’s addition, the two redesigned impellers wearing splitter blades were compared in staggered arrangement with different angles for the purpose of ulteriorly decreasing the pressure fluctuation. On the basis of Realizable k-ε model and SIMPLEC algorithm, the unsteady Reynolds-averaged Navier-Stokes equations (URANS) were resolved by means of CFD simulation and the flow performance and the vibration performance were validated with the experiments. The results illustrate that the redesigned impeller with multi-blade could raise the hydraulic performance and reduce the pressure fluctuation inside the pump. When the impeller of each side was laid with the staggered angle of 12 degrees, the pressure distribution tended to be more uniform and the pressure fluctuation was well ameliorated. Through the pressure fluctuation analysis in time domain and frequency domain, the pressure change inside the pumps could be evaluated quantitatively and accurately, hence different pumps could be contrasted in detail. The consequences of this paper could provide reference for pressure fluctuation reduction and vibration performance reinforcement of double-suction centrifugal pumps as well as other vane pumps.

Influence of Guide Ring on Energy Loss in a Multistage Centrifugal Pump

2018 ◽  
Vol 141 (6) ◽  
Author(s):  
Ren Yun ◽  
Zhu Zuchao ◽  
Wu Denghao ◽  
Li Xiaojun
Keyword(s):  
Energy Loss ◽  
Entropy Production ◽  
Evaluation Method ◽  
Guide Vane ◽  
Load Flow ◽  
Hydraulic Loss ◽  
Pump Efficiency ◽  
Centrifugal Pumps ◽  
Multistage Pump ◽  
Guide Ring

Multistage centrifugal pumps are highly efficient and compact in structure. Pump efficiency can be improved by an effective understanding of hydraulic behavior and energy loss, however, the traditional hydraulic loss evaluation method does not readily reveal the specific locations of energy loss in the pump. In this study, a guide ring was imposed in multistage pumps, and an entropy production theory was applied to investigate irreversible energy loss of a multistage pump with and without guide ring. Detailed distributions of energy losses in the pumps were calculated to determine the respective entropy production rates (EPRs). The EPR values as calculated are in close accordance with actual hydraulic loss values in the pumps. EPR values were higher in the multistage pump with the guide ring than the pump without a guide ring under part-load flow conditions (0.2Qd). However, the vortex flow in the pump was weakened (or eliminated) by the guide ring as flow rate increased; this reduced energy loss in the chambers. Flow passing the chamber was stabilized by the guide ring, which decreased shock and vortex loss in the chamber and guide vane. Under both designed flow condition and overload conditions, the EPR values of the guide ring-equipped multistage pump were lower than those without the guide ring. Furthermore, minimum efficiency index (MEI) values were also calculated for the two chamber structures; it was found that overall efficiency of pump with guide ring is better than that without.

scholarly journals Pressure Fluctuation Reduction of a Centrifugal Pump by Blade Trailing Edge Modification

Processes ◽  
2021 ◽  
Vol 9 (8) ◽  
pp. 1408 ◽  
Author(s):  
Bin Huang ◽  
Guitao Zeng ◽  
Bo Qian ◽  
Peng Wu ◽  
Peili Shi ◽  
...  
Keyword(s):  
Centrifugal Pump ◽  
Pressure Fluctuation ◽  
Pressure Side ◽  
Centrifugal Pumps ◽  
Trailing Edge ◽  
Impeller Blade ◽  
Blade Passing Frequency ◽  
Impeller Outlet ◽  
Edge Profile ◽  
Edge Trimming

The pressure fluctuation inside centrifugal pumps is one of the main causes of hydro-induced vibration, especially at the blade-passing frequency and its harmonics. This paper investigates the feature of blade-passing frequency excitation in a low-specific-speed centrifugal pump in the perspective of local Euler head distribution based on CFD analysis. Meanwhile, the relation between local Euler head distribution and pressure fluctuation amplitude is observed and used to explain the mechanism of intensive pressure fluctuation. The impeller blade with ordinary trailing edge profile, which is the prototype impeller in this study, usually induces wake shedding near the impeller outlet, making the energy distribution less uniform. Because of this, the method of reducing pressure fluctuation by means of improving Euler head distribution uniformity by modifying the impeller blade trailing edge profile is proposed. The impeller blade trailing edges are trimmed in different scales, which are marked as model A, B, and C. As a result of trailing edge trimming, the impeller outlet angles at the pressure side of the prototype of model A, B, and C are 21, 18, 15, and 12 degrees, respectively. The differences in Euler head distribution and pressure fluctuation between the model impellers at nominal flow rate are investigated and analyzed. Experimental verification is also conducted to validate the CFD results. The results show that the blade trailing edge profiling on the pressure side can help reduce pressure fluctuation. The uniformity of Euler head circumferential distribution, which is directly related to the intensity of pressure fluctuation, is improved because the impeller blade outlet angle on the pressure side decreases and thus the velocity components are adjusted when the blade trailing edge profile is modified. The results of the investigation demonstrate that blade trailing edge profiling can be used in the vibration reduction of low specific impellers and in the engineering design of centrifugal pumps.

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.

Calculating Cutoff Speeds of a Multistage Pump Rotor Taking into Account Lomakin Effect in the Front Seal of the Impeller

2020 ◽  
pp. 59-67
Author(s):  
D.G. Svoboda ◽  
A.A. Zharkovskii ◽  
E.A. Ivanov ◽  
I.O. Borshchev
Keyword(s):  
Hydrodynamic Forces ◽  
Centrifugal Pumps ◽  
Pump Rotor ◽  
Operating Modes ◽  
Flow Parameters ◽  
Ansys Cfx ◽  
Vibrational Characteristics ◽  
Shaft Deflection ◽  
Multistage Pump ◽  
Quantitative Impact

Studies of dynamic frequencies are an important stage in designing multistage vane pumps. This research aimed to confirm the rigidity and vibrational reliability of the pump rotor. Based on the recommendations of J.F. Gülich, the nominal rotational speed of the rotor shaft should differ from the cutoff speed by no less than 25 %. The Lomakin effect supposes taking into consideration the hydrodynamic forces acting in the gap seals and having a damping effect on the pump rotor. This research solved the problem of developing and verifying a numerical method of calculating hydrodynamic forces, which arise in seals of vane pumps at critical speeds. The studies were conducted on a ‘dry’ model of the rotor using ANSYS Mechanical software package. During computational modeling of bearings and seals, the COMBIT214 ele¬ment was used where the stiffness coefficient values were set. These values were determined by calculating the flow parameters in the gap seal using ANSYS CFX. The proposed method was verified using the experimental data obtained. The seal rigidity was calculated for different operating modes of the pump. It was shown that the hydrodynamic forces which arose in the gap seals had a significant influence on the rotor’s critical speed. Accounting for these forces increased the main own frequency of the rotor by approximately 44 %. This fact had a significant qualitative and quantitative impact on the vibrational characteristics of the pump. This study showed that the value of the hydrodynamic force was influenced by several factors: shaft deflection, differential pressure and geometry of the gap seal. The proposed method is recommended for use for multistage centrifugal pumps.

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