scholarly journals Hydraulic torque on the guide vane within the slight opening of pump turbine in turbine operating mode

2014 ◽  
Vol 22 (3) ◽  
pp. 032050 ◽  
Author(s):  
H G Fan ◽  
H X Yang ◽  
F C Li ◽  
N X Chen
Keyword(s):  
Guide Vane ◽  
Operating Mode ◽  
Pump Turbine

Investigation of the Flow Instabilities of a Low Specific Speed Pump-Turbine: Part 1 — Experimental and Numerical Analysis

2020 ◽  
Author(s):  
Sabri Deniz ◽  
Armando Del Rio ◽  
Martin von Burg ◽  
Manuel Tiefenthaler
Keyword(s):  
Experimental Data ◽  
Guide Vane ◽  
Turbulence Models ◽  
Operating Mode ◽  
Rotating Stall ◽  
Flow Instabilities ◽  
Pump Turbine ◽  
Flow Features ◽  
Low Specific Speed ◽  
Specific Speed

Abstract This is the first part of a two-part paper focusing on the flow instabilities of low-specific pump turbines. In this part, results of the CFD simulations and experiments of the research carried out on a low specific speed model pump-turbine at HSLU (Lucerne University of Applied Sciences) Switzerland are presented. The requirements of a stable and reliable pump-turbine operation under continuously expanding operating ranges, challenges the hydraulic design and requires new developments. Previous research at the HSLU [1] analyzed the instabilities of a medium specific speed (i.e. nq = 45) pump turbine. This paper presents the results of experimental (model pump-turbine at the test rig) and numerical (CFD) investigations of the pump-turbine instabilities of a low specific speed (nq = 25) pump-turbine in the turbine operating mode in the region of S-shaped characteristics (that is where the pump-turbine is synchronized and oscillations may occur during load rejection). The four-quadrant characteristics of a low specific speed model pump-turbine with two similar runners differentiating in the size (diameter) are measured. Testing of both runners with the same guide vane system provided information about the effects of the increased vaneless space (the distance between the guide vanes and runner) on the pump-turbine performance and stability both in turbine- and pump operating modes. A CFD methodology by using different numerical approaches and applying several turbulence models is developed in order to accurately predicting the characteristics of the reversible pump-turbines in the S-shaped region (speed no load conditions) as well as analyzing the flow features especially at off-design conditions. This CFD model is validated against the experimental data at 6° and 18° guide vane openings in turbine operating mode. With the measured data of the unsteady pressure measurements and detailed investigation of unstable ranges on the pump-turbine characteristics, flow instabilities in the low-specific speed model pump-turbine are analyzed. Relevant frequencies such as rotating stall, steady and unsteady vortex formations are determined. Based on the analysis of the experimental data and CFD results focusing especially on the flow features in the vaneless space and at the runner inlet, the onset and development of the flow instabilities are explored.

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.

scholarly journals Hysteresis Characteristic in Hump Region of a Pump-Turbine Model

2016 ◽  
Author(s):  
Deyou Li ◽  
Hongjie Wang ◽  
Jinxia Chen ◽  
Torbjørn K. Nielsen ◽  
Daqing Qin ◽  
...  
Keyword(s):  
Guide Vane ◽  
Pressure Sensors ◽  
Low Frequency ◽  
Rotational Frequency ◽  
Hysteresis Phenomenon ◽  
Pump Turbine ◽  
Hysteresis Characteristic ◽  
Hydraulic Losses ◽  
Measurement Direction ◽  
Turbine Model

The hump characteristic is one of the major instabilities in pump-turbines. When pump-turbines operate in the hump region, strong noise and serious fluctuations could be observed, which are harmful to the safe and stable operations and even destroy the whole unit as well as water conveyance system. In this paper, a low specific speed (nq = 36.1 min−1) pump-turbine model was experimentally investigated. Firstly, the hump characteristic was obtained under 19 mm guide vane opening. More interestingly, when the hump characteristic was measured in two directions (increasing and decreasing the discharge), the hysteresis characteristic was found during the hump region. The analysis of performance characteristics reveals that the hump instability is resultant of Euler momentum and hydraulic losses, and different Euler momentum and hydraulic losses in the two development processes lead to hysteresis phenomenon. Then, 12 pressure sensors were mounted in the different parts of the pump-turbine model to obtain the time and frequency characteristics. The analysis of fast Fourier transform confirms that the hump characteristic is related to the low-frequency (0.04–0.15 times rotational frequency) vortices. The occurrence and cease of vortices depend on the operating condition and measurement direction, which contribute to the hysteresis characteristic. Finally, the type of the low-frequency vortices was analyzed through the cross power spectrum.

scholarly journals Evolutions of guide vane moment of a pump-turbine during runaway transient process after pump trip

2019 ◽  
Vol 240 ◽  
pp. 072033 ◽  
Author(s):  
Z Y Yang ◽  
Y G Cheng ◽  
L S Xia ◽  
W W Meng ◽  
L W Gao ◽  
...  
Keyword(s):  
Transient Process ◽  
Guide Vane ◽  
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.

Investigation on reversible pump turbine flow structures and associated pressure field characteristics under different guide vane openings

2019 ◽  
Vol 62 (11) ◽  
pp. 2052-2074
Author(s):  
Maxime Binama ◽  
WenTao Su ◽  
WeiHua Cai ◽  
FengChen Li ◽  
XianZhu Wei ◽  
...  
Keyword(s):  
Pressure Field ◽  
Guide Vane ◽  
Flow Structures ◽  
Pump Turbine

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

GS0520 A Numerical Simulation on the Effects of Guide Vane Opening on a Pump-Turbine Performance

2016 ◽  
Vol 2016.22 (0) ◽  
pp. _GS0520-1_-_GS0520-2_
Author(s):  
Mayuko NAGASHIKI ◽  
Kazuhiko YOKOTA ◽  
Donghyuk KANG
Keyword(s):  
Numerical Simulation ◽  
Guide Vane ◽  
Pump Turbine ◽  
Turbine Performance

Domain Partitioned Transformation of Pump-Turbine Characteristic Curves in 3-D Space

2014 ◽  
Author(s):  
Wei Zeng ◽  
Jiandong Yang ◽  
Yongguang Cheng
Keyword(s):  
Guide Vane ◽  
Theoretical Method ◽  
Transformation Method ◽  
Measured Data ◽  
Pump Turbine ◽  
Characteristic Curves ◽  
Hydraulic Transient ◽  
Transient Simulations ◽  
Pumped Storage ◽  
Conventional Representation

Pump-turbine characteristic curves are the most important boundary condition in the hydraulic transient simulation of a pumped-storage hydropower station. Conventional representation of them, however, has serious defects, For instance, the “S” and “hump” shapes, composed of multiple values and steep twists, lead to the difficulty in interpolation between known guide-vane opening curves, which is necessary in hydraulic transient simulations. Here, a new transformation method was figured out to settle this problem thoroughly and to improve the accuracy of interpolation between the constant opening curves. Prior to the transformation, the characteristic curves are partitioned into eight domains. Curves of each domain were transformed through different formulae that fit the curves well. Eight characteristic surfaces in the 3-D space can be obtained by adding the guide vane opening as the coordinate axis. The theoretical method has been validated by the excellent agreements achieved by comparing the curves interpolated on the characteristic surfaces with the measured data.

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.

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