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.

scholarly journals Experimental Research on the Rotating Stall of a Pump Turbine in Pump Mode

Water ◽  
2019 ◽  
Vol 11 (11) ◽  
pp. 2426
Author(s):  
Xue ◽  
Liu ◽  
Lu ◽  
Gao ◽  
Meng
Keyword(s):  
Flow Field ◽  
Experimental Research ◽  
Flow Rate ◽  
Guide Vane ◽  
Rotating Stall ◽  
Dynamics Simulation ◽  
Positive Slope ◽  
Pump Mode ◽  
Pump Turbine ◽  
Pump Performance

The rotating stall is an unstable flow phenomenon of pump turbines in pump mode, which is of increasing concern to scientists and engineers working on pump turbines. However, at present, various studies are carried out based on CFD (computational fluid dynamics) simulation, while directly measured data and experimental research on flow fields are seldom reported. By utilizing PIV (particle image velocimetry) measuring equipment, the flow field within the guide vane zone of a low specific speed pump turbine in pump mode was measured. By measuring and analyzing the transient flow field, the evolutionary process of the rotating stall within the guide vane passages was determined. We found that for all three tested guide vane openings, regardless of whether the positive slope appeared or not, a pre-stall operating point was found for each opening in the process of decreasing the flow rate. The analysis of the loss within the flow field indicated that the dissipation-induced loss increased greatly after the rotating stall appeared. The pump performance curves at the three guide vane openings showed an inflection at the pre-stall point. When the flow rate is larger than that of the pre-stall point, the head of the pump turbine dramatically increases as the flow rate decreases. However, when the flow rate is smaller than the pre-stall point, such increases noticeably slows down.The research results showed that whether the positive slope on the pump performance curve occurred or not, instability caused by the rotating stall should be of great concern.

Influence of Guide Vane Setting in Pump Mode on Performance Characteristics of a Pump-Turbine

2017 ◽  
Vol 10 (2) ◽  
pp. 154-163 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Torbjørn K. Nielsen ◽  
Ruzhi Gong ◽  
Xianzhu Wei ◽  
...  
Keyword(s):  
Guide Vane ◽  
Performance Characteristics ◽  
Pump Mode ◽  
Pump Turbine

Computational Study of Pump Turbine: Partial Load Operations

2020 ◽  
Author(s):  
Muhannad Altimemy ◽  
Justin Caspar ◽  
Alparslan Oztekin
Keyword(s):  
Flow Rate ◽  
Draft Tube ◽  
Computational Study ◽  
Pressure Fluctuations ◽  
System Stability ◽  
Pump Turbine ◽  
Vortex Rope ◽  
Signal Velocity ◽  
Partial Load ◽  
Les Model

Abstract The performance of a pump-turbine under partial flow rates, 85%, 75%, and 65%, is studied using the LES model. The power signal, velocity, vorticity, and pressure field is presented over the blades and throughout the draft tube. Pressure fluctuations are probed at various locations over the wall of the draft tube. Examining the flow field in the blade region can provide further insights into the system performance. Flow-induced pressure fluctuations can disrupt system stability. For this turbine, a strong swirling region is observed around the draft tube walls, causing pressure fluctuations. The size and intensity of this region decrease with the flow rate. A vortex rope is present in all cases. At the design point, the strength is constant throughout the draft tube. However, at partial load, the rope is weakened along the draft tube. Between the region dominated by the vortex rope and the wall, there is a swirling shear layer, which moves closer to the wall as the flow rate decreases. Both the magnitude of pressure fluctuations at the wall and the pressure difference over the blade decrease with the flow rate. The decreased pressure differences over the blade represent less power produced, and the decline in fluctuation magnitude at the wall represents more system stability. For this turbine, there appears to be a trade-off between power and strength of pressure fluctuations.

Influences of wear-ring clearance leakage on performance of a small-scale pump-turbine

2019 ◽  
Vol 234 (4) ◽  
pp. 454-469 ◽  
Author(s):  
Jianru Yan ◽  
Zhitao Zuo ◽  
Wenbin Guo ◽  
Hucan Hou ◽  
Xin Zhou ◽  
...  
Keyword(s):  
Flow Rate ◽  
Total Pressure ◽  
Labyrinth Seal ◽  
Work Capacity ◽  
Small Scale ◽  
Leakage Flow ◽  
Pump Mode ◽  
Pump Turbine ◽  
Flow Angle ◽  
Turbine Mode

Wear-ring clearance leakage would affect performance of pump-turbine significantly. In this paper, the variation of the leakage and efficiency of flat ring seal and labyrinth seal are numerically studied on one pump-turbine when the width of clearance is 0.2 mm and 0.5 mm. The result shows that the effect of leakage flow cannot be neglected. The pump-turbine performance affected by leakage in turbine mode is more than that in pump mode at the same sealing structure and width of clearance. Each component’s proportion of total pressure loss hardly varies with flow rate at pump mode, which is opposite to that at turbine mode. Leakage does not change proportionally with system flow rate. When the width of clearance decreases to 0.2 mm, the leakage is reduced obviously because the maximum entropy occurs in the front pump chamber. The mixing of leakage flow and mainstream at impeller inlet at pump mode will increase the total pressure and decrease the flow angle and relative flow angle. Finally, it reduces the impeller’s work capacity.

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.

scholarly journals The Influence of Flow Rates on Pressure Fluctuation in the Pump Mode of Pump-Turbine with Splitter Blades

2020 ◽  
Vol 10 (19) ◽  
pp. 6752
Author(s):  
Ping Huang ◽  
Yajing Xiao ◽  
Jinfeng Zhang ◽  
Haikun Cai ◽  
Haiqin Song
Keyword(s):  
Pressure Fluctuation ◽  
Draft Tube ◽  
Guide Vane ◽  
Pump Mode ◽  
Pump Turbine ◽  
Flow Rates ◽  
Guide Vanes ◽  
Rotor Stator Interaction ◽  
Computational Fluid Dynamics Cfd ◽  
The Stability

This paper takes a pump-turbine as the research subject and, based on the Computational Fluid Dynamics (CFD) numerical method and combined with test data, investigates the pressure fluctuation characteristics in the pump mode and analyzes the pressure fluctuation characteristics at 0.75 Qd, 1.0 Qd and 1.25 Qd when the guide vane opening is 17.5°. The results showed that the protruding frequencies of pressure fluctuation in the bladeless region were mainly 5 fn, 10 fn and 20 fn, and the main frequencies in the runner area and near the outlet wall of the draft tube were 16 fn and 5 fn, respectively. At different heights for the guide vanes, the pressure fluctuation in the bladeless region had significant differences, and the pressure fluctuation near the bottom ring was the most intense. The amplitude of the rotor–stator interaction frequency continuously attenuates from the bladeless region to the outlet of the stay vanes, and the amplitude attenuation of each frequency is mainly concentrated in the area of the guide vanes. In this paper, the influence of different flow rates on the pressure fluctuation in the pump mode is analyzed, which provides a theoretical reference for the stability and further study of pump-turbines.

Experimental investigation of hysteresis on pump performance characteristics of a model pump-turbine with different guide vane openings

2020 ◽  
Vol 149 ◽  
pp. 652-663
Author(s):  
Deyou Li ◽  
Hong Chang ◽  
Zhigang Zuo ◽  
Hongjie Wang ◽  
Zhenggui Li ◽  
...  
Keyword(s):  
Experimental Investigation ◽  
Guide Vane ◽  
Performance Characteristics ◽  
Pump Turbine ◽  
Pump Performance

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.

Establishing & Estimating Gas-Liquid Performance Characteristics of Multiphase Pumps

2021 ◽  
Author(s):  
Chidirim Enoch Ejim
Keyword(s):  
Flow Rate ◽  
Rotational Speed ◽  
Volume Flow Rate ◽  
Volume Flow ◽  
Operating Conditions ◽  
Gas Content ◽  
Two Phase ◽  
Pump Performance ◽  
Multiphase Pump ◽  
The Difference

Abstract Multiphase electric submersible pumps (ESPs) are used to produce gas and liquid in wells with high gas content. These pumps are operated at different speeds, and designed to handle flows with various gas volume fractions (GVFs). This study uses gas-liquid dimensionless parameters to obtain and compare the performance of conventional multiphase pumps. Knowledge of such techniques is important for production engineers, field operators and application engineers to ascertain pump performance for given gas-liquid operating conditions. Gas-liquid performance data for two multiphase pumps with 8.00-inch and 8.62-inch housing diameters were obtained from open literature. The inlet pressure, GVF and rotational speed ranges were 100 to 300 psig, 0 to 0.57, and 3000 to 3600 revolutions per minute (RPM), respectively. The total flow rates varied from 15000 to 60000 barrels per day (BPD). Euler turbomachinery principles for gas-liquid flows were applied to the data to obtain required dimensionless parameters and two-phase dimensionless performance curves for the pumps. The method was tested using dimensionless curves for a given operating condition to obtain pump performance at another operating condition. The results showed that for each rotational speed, the difference in dimensionless pressure between the multiphase pump discharge and inlet decreased with increasing mass-quality-weighted volume flow rate. For each weighted volume flow rate, the difference in pump discharge and inlet dimensionless pressures decreased with increasing intake GVF. The decrease with increasing intake GVF can range between a factor of 3 and 4, depending on the magnitude of the weighted volume flow rate. Using the 3000 RPM data, a two-phase (gas-liquid) dimensionless performance curve was obtained for one of the multiphase pumps with intake GVF and dimensionless volume flow rate parameter as the independent variables. The curve was used to estimate pump performance at 3600 RPM and then compared with the actual reference test data. For the second multiphase pump, two datasets at different intake pressures were used to obtain the effects of intake pressure. The performance for this multiphase pump was a function of dimensionless volume flow rate, intake GVF and intake gas-liquid density ratio. The maximum error in the estimated performance data was within 7%. Overall, the performance of multiphase pumps can be estimated using the technique in this study for the flow conditions analyzed. This study highlights the importance of obtaining dimensionless two-phase performance characteristics of multiphase pumps. Given that these pumps are frequently used in oilfield production operations, capability to determine the pressure boosting performance of the pumps, for given operating conditions, is important to field operating personnel and design engineers. This knowledge benefits the operator to optimally produce hydrocarbons from high gas-content wells and maximize the economic bottom line from the field asset.

Impact of guide vane opening angle on the flow stability in a pump-turbine in pump mode

2016 ◽  
Vol 231 (13) ◽  
pp. 2484-2492 ◽  
Author(s):  
Di Zhu ◽  
Ruofu Xiao ◽  
Ran Tao ◽  
Weichao Liu
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Flow Regime ◽  
Flow Rate ◽  
Guide Vane ◽  
Low Flow ◽  
Opening Angle ◽  
Pump Mode ◽  
Pump Turbine ◽  
Hydraulic Losses

In the pump mode (storage mode) of a pump-turbine, unstable head variations occur as the flow rate decreases, leading to unstable, unsafe operation. Thus, the hydrodynamics of pump-turbines in the unstable operating range should be investigated to improve their designs. This study presents experimental and numerical studies of the hydrodynamics. The experiments investigated the external characteristics with the head instabilities captured by both the model tests and the computational fluid dynamics simulations. The computational fluid dynamics model used detached eddy simulations to study the flow details which showed that hydraulic losses were the reason for the unstable head variations and the poor flow regime was the source of the losses. In the unstable, low flow rate range, the flow direction is no longer consistent with the guide vane direction, so undesirable flow structures develop in the passages. Therefore, appropriate guide vane opening angles are needed to improve the flow regime and reduce the hydraulic losses. These will enhance the operating stability and safety in engineering applications.

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