scholarly journals Analysis of Performance Characteristics Predicted From Several Experimental Data and Conversion Methods for Pumps as Turbine Application Using Statistical Techniques

2020 ◽  
Vol 39 (2) ◽  
pp. 213-226
Author(s):  
Ombeni Mdee ◽  
Cuthbert Kimambo ◽  
Torbjorn Nielsen ◽  
Joseph Kihedu
Keyword(s):  
Experimental Data ◽  
Flow Rate ◽  
Performance Characteristics ◽  
Hydropower Plant ◽  
Rate Coefficients ◽  
Reverse Direction ◽  
Centrifugal Pumps ◽  
Pump Mode ◽  
Reverse Mode ◽  
Specific Speed

Different performance characteristics have been indicated when running centrifugal pumps in the reverse direction. The water flows from the discharge side of the pump to the suction side to run in the reverse direction and generate the mechanical rotational energy for the micro-hydropower plant. The current study evaluates the extent of variation of performance characteristics predicted by several experimental data from different pump-specific speeds and conversion methods. The performance characteristics discussed include the head, flow rate, efficiency and specific speed. The flow rate and head of a pump operating in pump mode divided with the characteristic of the pump operating in the reverse mode, at the best efficiency point, the resulting coefficient of determination (R 2 ) values were of 0.890 and 0.708, respectively. Also, the graph of head versus flow rate coefficients, which is a second- order polynomial function, has shown the value of R 2 of 0.954 for pump-specific speed ranging between 9 and 94 rpm. However, the pump in the reverse mode has smaller performance characteristics for efficiency and specific speed compared to the pump mode operation with R 2 of 0.966 and 0.999, respectively. Furthermore, schematic empirical statistical models were developed to predict the performance characteristics of several conversion methods using pump data obtained from the manufacturers.

Performance characteristics and internal flow patterns in a reverse-running pump–turbine

2011 ◽  
Vol 226 (3) ◽  
pp. 695-708 ◽  
Author(s):  
R Barrio ◽  
J Fernández ◽  
E Blanco ◽  
J Parrondo ◽  
A Marcos
Keyword(s):  
Stokes Equations ◽  
Internal Flow ◽  
Flow Patterns ◽  
Performance Characteristics ◽  
Centrifugal Pumps ◽  
Pump Mode ◽  
Modes Of Operation ◽  
Pump Turbine ◽  
Reverse Mode ◽  
Numerical Predictions

Vaneless centrifugal pumps are reversible turbomachines that can operate also as centripetal turbines in low and very low-head power plants. However, the general performance in reverse mode is difficult to predict since the internal flow patterns are different from pump mode and the performance characteristics are not usually provided by manufacturers. This article presents numerical and experimental investigations on the operation of a reverse-running pump–turbine. The numerical calculations were carried out by solving the full unsteady Reynolds-averaged Navier–Stokes equations with the commercial code Fluent for several flowrates between 20 per cent and 160 per cent of rated conditions and both modes of operation. A complementary series of experimental measurements were performed in a test rig in order to obtain the general characteristics of the machine in pump and turbine modes, with the purpose of validating the numerical predictions. Once validated, the numerical model was used to investigate the flow patterns at some significant locations by means of pressure and velocity contours, and also by vector maps. Additionally, the model allowed the estimation of the steady load on the impeller as a function of flowrate in both modes of operation. It was concluded that, while the radial load in reverse mode is three times smaller than in pump mode, the axial load can be up to 1.6 times larger.

Theoretical and Numerical Study of Performance Prediction of Centrifugal Pumps as Turbines

2013 ◽  
Vol 444-445 ◽  
pp. 579-587
Author(s):  
Xiao Hui Wang ◽  
Jun Hu Yang ◽  
Feng Xia Shi ◽  
Ren Hui Zhang
Keyword(s):  
Flow Rate ◽  
Performance Prediction ◽  
Numerical Study ◽  
Theoretical Method ◽  
Attractive Alternative ◽  
Centrifugal Pumps ◽  
Pump Mode ◽  
External Characteristic ◽  
Specific Speed ◽  
Theoretical Results

Pumps as turbines (PAT) is an attractive alternative for recovering the pressure-energy. Establishing an external characteristic correlation between pumps and turbines is essential in selecting the proper machine. In this study, a theoretical method was presented to predict the performance of PAT at best efficiency point based on pump’s characteristics (geometric and hydraulic). In order to verify the theoretical results, the pumps with specific speed 55, 86,128,180,200 were simulated in direct and reverse modes by FLUENT12.0. Using theoretical and numerical results, the characteristic correlation curves of pumps in direct and reverse modes were obtained. Deviations of theoretical results s in higher flow rate and head than pump mode, the best efficiency of PAT was 2%~6% lower than pump mode.

A correlation to predict the performance characteristics of centrifugal pumps handling slurries

1997 ◽  
Vol 211 (2) ◽  
pp. 147-157 ◽  
Author(s):  
K A Kazim ◽  
B Maiti ◽  
P Chand
Keyword(s):  
Experimental Data ◽  
Particle Size ◽  
Suspended Solids ◽  
Reduction Factor ◽  
Performance Characteristics ◽  
Centrifugal Pumps ◽  
Pump Performance ◽  
New Correlation ◽  
Effect Of Particle Size ◽  
The Individual

Centrifugal pumps are being used increasingly for transportation of slurries through pipelines. To design a slurry handling system it is essential to have a knowledge of the effects of suspended solids on the pump performance. A new correlation to predict the head reduction factor for centrifugal pumps handling solids has been developed. This correlation takes into account the individual effect of particle size, particle size distribution, specific gravity and concentration of solids on the centrifugal pump performance characteristics. The range of validity of the correlation has been verified by experiment and by using experimental data available from the literature. The present correlation shows better agreement with the experimental data than existing correlations.

Effect of the Section Area of Volute in Low Specific Speed Centrifugal Pumps on Hydraulic Performance

2009 ◽  
Author(s):  
Xiang Zhang ◽  
Yang Wang ◽  
Jianhui Fu ◽  
Cui Dai ◽  
Caihong Wang
Keyword(s):  
Flow Rate ◽  
Low Flow ◽  
Centrifugal Pumps ◽  
Blade Angle ◽  
Rate Condition ◽  
Section Area ◽  
Impeller Outlet ◽  
Low Specific Speed ◽  
Specific Speed ◽  
Experimental Researches

The volute of low specific speed centrifugal pumps has a great impact on the performance of the pump in that the highest efficiency can only be achieved when the impeller is matched with a well-designed volute. At off-BEP conditions, the performance of pumps declines as a consequence of a mismatch between characteristics of the impeller and the volute. The section area is the most important factor of volute. Numerical simulations and experimental researches have been carried out on the routine-designed impeller and the non-overloading designed impeller (different impeller outlet blade angle between two types of impellers) in the hope of finding out the effect of the section area of volute on low specific speed centrifugal pumps. It has been found that the uneven flow rate on different volute sections caused by the backflow between volute and impeller is one of the reasons for the efficiency decline of pumps at off-BEP conditions, especially in the low flow rate condition. It has also been found that the routine-designed impeller is more easily affected by the section area of volute than non-overloading designed impeller.

A One-Dimensional Numerical Model for Calculating the Efficiency of Pumps as Turbines for Implementation in Micro-Hydro Power Plants

Volume 1 ◽  
2004 ◽  
Author(s):  
Mario Amelio ◽  
Silvio Barbarelli
Keyword(s):  
Flow Rate ◽  
Power Plants ◽  
Renewable Energy Sources ◽  
Numerical Code ◽  
Geometrical Parameters ◽  
Centrifugal Pumps ◽  
Simple Method ◽  
Hydro Power ◽  
One Dimensional ◽  
Specific Speed

Increasing interest in renewable energy sources makes attractive the exploitation of many small power hydraulic resources (micro-hydro – less than 100 kW). However, the high cost of hydraulic turbines hinders the actual realization of micro-hydro plants. An alternative cheaper solution could be to replace the turbine with a reverse-mode centrifugal pump, developing therefore a pump as turbine (PAT) system. Unfortunately, although a wide number of centrifugal pumps are commercially available for micro-hydro engineering plant, manufacturers do not provide information regarding the performance of centrifugal pumps in turbine mode. In this paper, a simple method based on a one-dimensional numerical code is presented for deriving the turbine efficiency of commercially available centrifugal pumps. The code estimates a sizing of the component using information such as impeller diameter, specific speed, head and flow rate at pump BEP, machine overall dimension which are provided in manufacturer catalogues, to deduce geometrical parameters of the machine, calculating the losses and thus determining PAT performances. The method was validated by a comparison of the predicted characteristic curves with some experimental measurements available on PATs working in a range of specific speed (Head in meters and flow rate in m3/s) from 9 to 65. The numerical code calculations effectively predicted the measured efficiency of PATs. At BEP, the efficiency was estimated with a relative error of ±10% which is a value much lower than one obtained by using the available in literature correlations. A prediction within this error range is generally accepted for this kind of application.

Experimental and Numerical Study of Cavitation in Centrifugal Pumps

2010 ◽  
Author(s):  
Erfan Niazi ◽  
M. J. Mahjoob ◽  
Ardeshir Bangian
Keyword(s):  
Experimental Data ◽  
Numerical Model ◽  
Mass Flow Rate ◽  
Computer Simulations ◽  
Mass Flow ◽  
Flow Rate ◽  
Numerical Study ◽  
Numerical Results ◽  
Centrifugal Pumps ◽  
Cavitation Threshold

Cavitation in pumps is one of the most important causes of damage to pumps impellers/inducers. A numerical model is developed here to simulate the pump hydraulics in different conditions. Experiments are also conducted to validate the computer simulations. To verify the numerical model, the h–m˙ (head versus mass flow rate) of the model is compared with the experimental data. The system is then run under cavitation state. Two methods are applied to monitor the cavitation threshold: first by using stroboscope and observing cavitation bubbles through the transparent casing of the pump and second by checking the NPSHA value for cavitation based on ISO3555. The paper then compares the experimental and numerical results to find the strengths and weaknesses of the numerical model.

scholarly journals Theoretical, Numerical and Experimental Research of Single Stage, Radial Discharge Centrifugal Pump Operating in Turbine Mode

2019 ◽  
Vol 8 (12) ◽  
pp. 1265-1270
Keyword(s):  
Centrifugal Pump ◽  
Experimental Research ◽  
Performance Prediction ◽  
Experimental Analysis ◽  
Numerical Results ◽  
Pump Mode ◽  
Characteristic Curves ◽  
Reverse Mode ◽  
Specific Speed ◽  
Turbine Mode

In this study, the best efficiency point of end suction, radial discharge, centrifugal pump operated in turbine mode was arrived applying numerical and experimental analysis. The pump was simulated both in direct and turbine modes using Star CCM+ CFD software. Characteristic curves were developed for the pump in direct and turbine modes. A monoblock centrifugal pump of specific speed 35.89 (m, m3 /s) was used for this study. The pump was tested experimentally in turbine and pump mode .The theoretical and numerical results were verified by those obtained through experimentation. Some of the correlations proposed by earlier researchers for performance prediction of pump in reverse mode were also tested

Dynamic Stall Inception and Evolution Process Measured by High-Frequency PIV System in Low Specific Speed Impeller

2021 ◽  
Author(s):  
Xiaodong Liu ◽  
Yaojun Li ◽  
Zhuqing Liu ◽  
Wei Yang
Keyword(s):  
Flow Rate ◽  
Flow Separation ◽  
High Frequency ◽  
Suction Side ◽  
Dynamic Stall ◽  
Channel Inlet ◽  
Centrifugal Pumps ◽  
Stall Inception ◽  
Low Specific Speed ◽  
Specific Speed

Abstract Stall in centrifugal pumps is a complicated flow phenomenon, which is detrimental to the pumps' safety and stable operation. Using a high-frequency PIV system (f=10k Hz) and a bench-scale refractive index matching experimental setup, two measurement methods are introduced to observe the dynamic stall inception and evolution. In the first method, the flow rate was continuously reduced at an interval of 0.005Qd and the experiment was carried out under stable flow rate condition. It shows the flow adjacent to the blade suction side gradually evolved from the flow separation into a broken vortex. The stall vortex moved toward the impeller's inlet and continuously grew, and resulted in significant changes in the main flow direction at the channel inlet. The formation and development of the other vortex structures in channel were closely related to the stall vortex at the inlet. The second method is the dynamic flow rate measurement and the results show that the stall is not caused by the increase in the relative inflow angle. It was obtained that the velocity value in the stall channel near the suction side rapidly decreased; however in the non-stall channel, the velocity value increased at the channel inlet. By analyzing the velocity distribution in both flow channels before and after the stall, the mechanism of alternating stall is well explained. Meanwhile, it was obtained that the stall was more likely to originate from the flow separation near the blade suction side for low specific speed impeller

Numerical Simulation on Pump Transient Characteristic in a Model Pump Turbine

2019 ◽  
Vol 141 (11) ◽  
Author(s):  
Deyou Li ◽  
Yonglin Qin ◽  
Zhigang Zuo ◽  
Hongjie Wang ◽  
Shuhong Liu ◽  
...  
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Performance Characteristics ◽  
Transient Processes ◽  
Pump Mode ◽  
Pump Turbine ◽  
Pump Performance ◽  
Acceleration And Deceleration ◽  
The Difference ◽  
Hysteresis Characteristics

Pump performance characteristics of pump turbines in transient processes are significantly different from those in steady processes. In the present paper, transient processes of a flow rate that increased and decreased in the pump mode of a model pump turbine were simulated through unsteady simulations using the shear stress transport (SST) k–ω turbulence model. The numerical results reveal that there is a larger hysteresis loop in the performance characteristics of the increasing and decreasing directions of the flow rate compared with those of steady results. Detailed discussions are carried out to determine the generation mechanism of obvious hysteresis characteristics using the methods of entropy production and continuous wavelet analysis. Analyses show that the states of the backflow at the draft tube outlet and the vortices in the impeller and guide/stay vanes are promoted or suppressed owing to the acceleration and deceleration of the fluid. This contributes to the difference in pump performance characteristics of the pump turbine.

Vortex Pump as Turbine—A Type Turbine for Energy Generation or Recovery Based on Computational Fluid Dynamics Prediction

2019 ◽  
Vol 141 (10) ◽  
Author(s):  
Wenguang Li
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Structure ◽  
Conversion Factor ◽  
Pressure Profile ◽  
Reverse Direction ◽  
Centrifugal Pumps ◽  
Cavitation Performance ◽  
Vortex Pump ◽  
Specific Speed

An experimental vortex pump with a specific speed of 76 is investigated to get its performance and flow structure under noncavitation and cavitation conditions when the pump operates as turbine in the reverse direction by using computational fluid dynamics (CFD) method. A method is proposed to extract hydraulic, volumetric, and mechanical efficiencies for the first time. It is shown that a vortex pump can operate as turbine but it is subject to poor cavitation performance. The performance conversion factors of flow rate and head are 2.33 and 2.74 which are much larger than existing centrifugal pumps as turbine with the same specific speed. The conversion factor of efficiency is 0.98, which agrees with the conversion factor of efficiency for a centrifugal pump as turbine. There are a rope cavity and a vortex flow in the same rotational direction of the impeller. It is shown that flow structure is complex in the impeller in pump and turbine modes, particularly on the blade-to-blade surface, while static pressure profile in the volute and impeller as well as the space between the casing and the impeller is simple. The flow in the space between the impeller and the casing cannot be regarded as a forced vortex in both modes. The cavitation performance improvement and rope cavity control may be key issues in the future.

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