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.

scholarly journals Energy Balance and Local Unsteady Loss Analysis of Flows in a Low Specific Speed Model Pump-Turbine in the Positive Slope Region on the Pump Performance Curve

Energies ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1829 ◽  
Author(s):  
Guocheng Lu ◽  
Zhigang Zuo ◽  
Demin Liu ◽  
Shuhong Liu
Keyword(s):  
Discharge Coefficient ◽  
Guide Vane ◽  
Flow Patterns ◽  
Rotating Stall ◽  
Performance Curve ◽  
Positive Slope ◽  
Pump Turbine ◽  
Pump Performance ◽  
Loss Analysis ◽  
Low Specific Speed

The positive slope on the pump performance curve of pump-turbines suggests potential operational instabilities in pump mode. Previous research has indicated that the increase of the hydraulic loss caused by sudden changes of flow patterns in pump-turbines is responsible for the positive slope, however its detailed flow mechanism is still unclear. A low specific speed model pump-turbine was numerically investigated against experiments in the present study, by applying unsteady RANS (Reynolds-Averaged Navier–Stokes equations) simulations with a v2-f turbulence model. The mechanism of occurrence of the positive slope on the pump performance curve was discussed regarding the energy balance, as this region appears when the value of ∂ P u ∂ Q is larger than the critical value P u Q . An unsteady local loss analysis, derived from the energy equation, was conducted to illustrate the contribution of local flow patterns to the loss in corresponding hydraulic components. The variation of the kinetic energy of the mean flow was taken into account for the first time so that this method can be applied to highly time dependent flow patterns, e.g., a rotating stall in the present study. The investigations on the flow patterns revealed that some guide vane channels stalled with a larger discharge coefficient than the positive slope region. Several guide vane channels near the stalled channels were stalling with minor decrease of the discharge coefficient, leading to sudden increases of the input power and the loss. When the discharge coefficient slightly decreased in further, the pump-turbine operated into the positive slope region, and the rotating stall with 3 stall cells appeared, proven by the FFT (Fast Fourier Transform) and cross-phase analysis on the pressure fluctuations.

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.

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.

Effect of Interface Condition on the Hydraulic Performance of a Pump-Turbine at Various Guide Vane Opening Conditions in Pumping Mode

2019 ◽  
Author(s):  
Jun-Won Suh ◽  
Seung-Jun Kim ◽  
Young-Seok Choi ◽  
Jin-Hyuk Kim ◽  
Won-Gu Joo ◽  
...  
Keyword(s):  
Stokes Equations ◽  
Guide Vane ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Rotating Stall ◽  
Interface Condition ◽  
Navier Stokes ◽  
Pump Mode ◽  
Pump Turbine ◽  
High Flexibility

Abstract Nowadays, pumped-storage power stations require high flexibility and reliability in operation under off-design conditions, especially in the pump mode. When a pump-turbine operates under various part load conditions in pump mode, highly dynamic phenomenon such as stationary vortex and rotating stall occur. Therefore, the performance characteristics in pump mode are vital for the safe and effective operation. A number of studies have been conducted to investigate the flow characteristics in turbine or pump mode under different GVOs through numerical simulations. However, the studies about influence of the position of interface and interface condition on the pump characteristics of pump-turbines are not completely clear. In this paper, the three-dimensional steady and unsteady Reynolds-averaged Navier–Stokes equations were solved for a detailed analysis of the influence of interface conditions with various guide vane opening conditions in pump mode. To ensure the reliability of the numerical analysis, the numerical results were validated in comparison with the experimental data.

scholarly journals Experimental research on flow field of high head pump turbine based on PIV test

2021 ◽  
Vol 627 ◽  
pp. 012016
Author(s):  
D M Liu ◽  
L B Ma ◽  
N Li ◽  
Y Z Zhao ◽  
Huan Cheng
Keyword(s):  
Flow Field ◽  
Experimental Research ◽  
Pump Turbine ◽  
High Head

scholarly journals Simulation and Experimental Investigation of the Stay Vane Channel Flow in a Reversible Pump Turbine at Off-Design Conditions

2017 ◽  
Vol 61 (2) ◽  
pp. 94 ◽  
Author(s):  
Sandro Erne ◽  
Gernot Edinger ◽  
Anton Maly ◽  
Christian Bauer
Keyword(s):  
Transient Flow ◽  
Guide Vane ◽  
Low Frequency ◽  
Rotating Stall ◽  
Design Flow ◽  
Flow State ◽  
Mean Flow ◽  
Load Range ◽  
Pump Turbine ◽  
Stall Inception

This work presents the assessment of the mean flow field and low frequency disturbances in the stay vane channel of a model pump turbine using transient numerical simulations and LDV-based measurements. The focus is laid on transient CFD simulations of characteristic flow states in the stay vane channel when operating at off-design conditions in pump mode. Experimental and numerical investigations obtained a shifting velocity distribution between the shroud and hub of the distributor when continuously increasing the discharge in the part-load range. Simulations captured the occurrence of this changing flow state in the stay vane channel reasonably well. A further increase of the discharge showed a uniformly redistributed mean flow of both hub and shroud side. Monitoring points and integral quantities from measurements and transient simulations were used to interpret the development of transient flow patterns in the stay vane channel at the operating point of strongest asymmetrical flow. During simulation and measurement, a dominant rotating stall inception was observed near the design flow of the pump turbine. At this point where the stall becomes severe, a high level of correlation between the signals of the upper and lower stalled flow in the stay vane channel was calculated. Further simulations for different guide vane positions predicted a strong influence of the guide vane position on the structure of rotating stall.

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

scholarly journals Experimental Characterization of a Pump–Turbine in Pump Mode at Hump Instability Region

2015 ◽  
Vol 137 (5) ◽  
Author(s):  
J. Yang ◽  
G. Pavesi ◽  
S. Yuan ◽  
G. Cavazzini ◽  
G. Ardizzon
Keyword(s):  
High Speed ◽  
Dynamic Pressure ◽  
Load Condition ◽  
Rotating Stall ◽  
Pump Mode ◽  
Pump Turbine ◽  
Part Load ◽  
Time Frequency ◽  
Speed Flow ◽  
Dynamic Pressure Measurements

The unsteady phenomena of a low specific speed pump–turbine operating in pump mode were characterized by dynamic pressure measurements and high-speed flow visualization of injected air bubbles. Analyses were carried out on the pressure signals both in frequency and time–frequency domains and by bispectral protocol. The results obtained by high-speed camera were used to reveal the flow pattern in the diffuser and return vanes channels The unsteady structure identified in the return vane channel appeared both at full and part load condition. Furthermore, a rotating stall structure was found and characterized in the diffuser when the pump operated at part load. The characteristics of these two unsteady structures are described in the paper.

scholarly journals Numerical Study of Pump-Turbine Instabilities Under Pumping Mode Off-Design Conditions

2015 ◽  
Author(s):  
Uroš Ješe ◽  
Regiane Fortes-Patella ◽  
Matevž Dular
Keyword(s):  
Power Plants ◽  
Numerical Study ◽  
Guide Vane ◽  
Characteristic Curve ◽  
Rotating Stall ◽  
Electrical Network ◽  
Pump Turbine ◽  
Wide Range ◽  
Pumping Mode ◽  
And Performance

Pumped storage power plants, using reversible pump-turbines, are a great solution to maintain the stability of an electrical network. The continuous operating area of reversible pump-turbines machines is usually delimited by cavitation or a hydraulic instability called hump phenomena at part load. If the machine operates under these off-design conditions, it might be exposed to vibrations and performance losses. The paper focuses on the numerical analysis of the pumping mode regime and pays special attention to the prediction of the hump shaped characteristic curve and associated rotating stall. The investigations were made on a high head pump-turbine design (nq=27) at model scale for four different guide vane opening angles and a wide range of flow rates. Numerical simulations were performed and analyzed in LEGI and were compared to the global experimental data, provided by Alstom Hydro.

Velocity Measurements Downstream of the Impellers in a Multistage Centrifugal Blower

1994 ◽  
Author(s):  
G. L. Amulfi ◽  
D. Micheli ◽  
P. Pinamonti
Keyword(s):  
Flow Field ◽  
Unsteady Flow ◽  
Flow Rate ◽  
Rotating Stall ◽  
Operating Conditions ◽  
Field Analysis ◽  
Test Plant ◽  
Hot Wire ◽  
Centrifugal Blower ◽  
Ensemble Averaging

The paper presents the results of an experimental investigation on a four-stage centrifugal blower, having the aim of obtaining an accurate description of the flow field behind the impellers in several operative conditions and for different geometrical configurations. Actually, the test plant allows to change the turbomachinery characteristics assembling one, two, three or four stages and three different types of diffusers. In this first research step, the blower has been tested in the four-stage vaneless diffuser configuration. The unsteady flow field behind the impellers and in the diffusers has been measured by means of a hot-wire anemometer. A Phase Locked Ensemble Averaging Technique has been utilised to obtain the relative flow field from the instantaneous signals of the stationary hot-wire probes. Several detailed measurements sets have been performed using both single and crossed hot-wire probe, to obtain the velocity vectors and turbulence trends, just behind the blower impellers and in several radial positions of the vaneless diffusers. These measurements have been done at different flow rate conditions, covering unsteady flow rate phenomena (rotating stall) too. The results obtained allowed to get a detailed flow field analysis in the multistage centrifugal blower, in relation to the geometrical configuration and to the differing operating conditions.

Sign in / Sign up

Export Citation Format

Share Document