Effect of the Speed Factor On the Amplitude of the Blade Passing Frequency in the Vaneless Space of a Pump Turbine in Turbine Mode

2021 ◽  
Author(s):  
Jinhong Hu ◽  
Jiebin Yang ◽  
Wei Zeng ◽  
Jiandong Yang
Keyword(s):  
Strouhal Number ◽  
Goodness Of Fit ◽  
Guide Vane ◽  
Mathematical Relationship ◽  
Pump Turbine ◽  
Speed Factor ◽  
Blade Passing Frequency ◽  
Rotor Stator Interaction ◽  
Pumped Storage ◽  
Turbine Mode

Abstract An exponential expression describing the relationship between the amplitude of the blade passing frequency in the vaneless space of a pump turbine operating in the turbine mode and the speed factor is proposed based on statistical analysis. This mathematical relationship was discovered through signal processing of the data recorded during the emergency load rejection process of a prototype pump turbine. Subsequently, based on the pumped-storage test rig at Wuhan University, an experimental investigation was conducted to verify this mathematical relationship. The results indicated that, under the optimal guide vane opening of the model pump turbine, the goodness of fit of this mathematical relationship was quite high. As for the Francis pump turbine, the speed factor corresponds to the Strouhal number. Therefore, for this correlation, the underlying physical mechanism is the influence of the Strouhal number. This relation could inform the design and operation of pump turbines to control the intensity of pressure pulsations in the vaneless space. In addition, based on this mathematical relationship, the intensity of the rotor-stator interaction for different pump turbines can be compared quantitively.

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 On the Rotor Stator Interaction Effects of Low Specific Speed Francis Turbines

2019 ◽  
Vol 2019 ◽  
pp. 1-11 ◽  
Author(s):  
Einar Agnalt ◽  
Igor Iliev ◽  
Bjørn W. Solemslie ◽  
Ole G. Dahlhaug
Keyword(s):  
Guide Vane ◽  
Pressure Fluctuations ◽  
Angular Position ◽  
Pressure Sensors ◽  
Pump Turbine ◽  
Blade Loading ◽  
Loading Case ◽  
Rotor Stator Interaction ◽  
Low Specific Speed ◽  
Specific Speed

The rotor stator interaction in a low specific speed Francis model turbine and a pump-turbine is analyzed utilizing pressure sensors in the vaneless space and in the guide vane cascade. The measurements are analyzed relative to the runner angular position by utilizing an absolute encoder mounted on the shaft end. From the literature, the pressure in the analyzed area is known to be a combination of two effects: the rotating runner pressure and the throttling of the guide vane channels. The measured pressure is fitted to a mathematical pressure model to separate the two effects for two different runners. One turbine with 15+15 splitter blades and full-length blades and one pump-turbine with six blades are investigated. The blade loading on the two runners is different, giving different input for the pressure model. The main findings show that the pressure fluctuations in the guide vane cascade are mainly controlled by throttling for the low blade loading case and the rotating runner pressure for the higher blade loading case.

Flow Analysis of the Guide Vanes Region of Pump Turbine at the Slight Opening in the Pumping Startup Process

2016 ◽  
Author(s):  
Honggang Fan ◽  
Qingfeng Ji ◽  
Weili Liao ◽  
Haixia Yang
Keyword(s):  
Guide Vane ◽  
Flow Analysis ◽  
Three Dimensional ◽  
Main Flow ◽  
Three Dimensional Model ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Abrupt Changes ◽  
Dimensional Simulation ◽  
Pumped Storage

The unit of a Pumped Storage Power Station experienced abnormal noise and vibration in the guide vanes at the slight opening when the pump turbine was in the process of startup in the pumping mode. Based on this phenomena, the three dimensional model of the pump turbine was established, RNG k-epsilon two equations turbulence model was selected for the flow numerical simulation in the pump turbine because this model can simulate both the flow separation and vortex dynamics, and it is more accurate in the near wall areas. The governing equations were discretized with the finite volume method. The computation was carried out with three steps, 1.steady calculation, 2.unsteady calculation with constant guide vane opening, 3.unsteady calculations with the increase of the opening of guide vanes, by using the results of the last step as the initial condition. According to the three dimensional simulation results, the main flow between the guide vanes was deflected from attaching to the one vane to the other vane with the opening of the guide vanes. The calculation of complete 3D flow indicated that the deflections of the flows between the different adjacent guide vanes were basically the same, however, the deflections starting times had a few differences. The variation of the torque on the guide vane was also investigated, and the results shown the abrupt changes occurred during the deflection process of the main flow. When the torque produced by the servomotor cannot adapt quickly enough to the abrupt changes, the vibration and loud scrape noise might occur.

scholarly journals Internal Mechanism and Improvement Criteria for the Runaway Oscillation Stability of a Pump-Turbine

2018 ◽  
Vol 8 (11) ◽  
pp. 2193 ◽  
Author(s):  
Qin Zhou ◽  
Linsheng Xia ◽  
Chunze Zhang
Keyword(s):  
Energy Dissipation ◽  
Guide Vane ◽  
Flow Characteristics ◽  
Energy Dissipation Rate ◽  
Sharp Change ◽  
Pump Turbine ◽  
Oscillation Process ◽  
Internal Mechanism ◽  
Pumped Storage ◽  
Runaway Process

The runaway oscillation process of the pump-turbine in a high head pumped-storage power plant is usually unstable. The root cause of its instability is still unclear. In this paper, its internal mechanism and the improvement method were studied in depth. First, the flow characteristics in a model pump-turbine during the runaway process at four guide-vane openings (GVOs) were investigated by 3D transient numerical simulations. Then, the energy dissipation characteristics of different types of backflow vortex structures (BFVSs) occurring at the runner inlet and their impacts on the runaway stability were investigated by the entropy production theory. The results show that the location change of BFVSs between the hub side and the mid-span of the runner inlet around the no-load point leads to the sharp change in the energy dissipation rate, which makes the slope of dynamic trajectory positive and the runaway oscillation self-excited. If the occurrence of BFVSs at the hub side is suspended, the runaway process will be damped. Finally, the pump-turbine runner was improved to obtain a wider stable operating range.

scholarly journals Optimization of Pump Turbine Closing Operation to Minimize Water Hammer and Pulsating Pressures During Load Rejection

Energies ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 1000 ◽  
Author(s):  
Jiawei Ye ◽  
Wei Zeng ◽  
Zhigao Zhao ◽  
Jiebin Yang ◽  
Jiandong Yang
Keyword(s):  
Guide Vane ◽  
Water Hammer ◽  
Nsga Ii ◽  
Pump Turbine ◽  
Guide Vanes ◽  
Multi Objective ◽  
Spiral Case ◽  
Transitional Processes ◽  
Pumped Storage ◽  
Load Rejection Process

In load rejection transitional processes in pumped-storage plants (PSPs), the process of closing pump turbines, including guide vane (GVCS) and ball valve closing schemes (BVCS), is crucial for controlling pulsating pressures and water hammer. Extreme pressures generated during the load rejection process may result in fatigue damage to turbines, and cracks or even bursts in the penstocks. In this study, the closing schemes for pump turbine guide vanes and ball valves are optimized to minimize water hammer and pulsating pressures. A model is first developed to simulate water hammer pressures and to estimate pulsating pressures at the spiral case and draft tube of a pump turbine. This is combined with genetic algorithms (GA) or non-dominated sorting genetic algorithm II (NSGA-II) to realize single- or multi-objective optimizations. To increase the applicability of the optimized result to different scenarios, the optimization model is further extended by considering two different load-rejection scenarios: full load-rejection of one pump versus two pump turbines, simultaneously. The fuzzy membership degree method provides the best compromise solution for the attained Pareto solutions set in the multi-objective optimization. Employing these optimization models, robust closing schemes can be developed for guide vanes and ball valves under various design requirements.

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.

Numerical Simulation of the Unsteady Flow in a High-Head Pump Turbine and the Runner Improvement

2008 ◽  
Author(s):  
Hongjuan Ran ◽  
Xianwu Luo ◽  
Yao Zhang ◽  
Baotang Zhuang ◽  
Hongyuan Xu
Keyword(s):  
Numerical Simulation ◽  
Unsteady Flow ◽  
Guide Vane ◽  
Positive Slope ◽  
Pump Turbine ◽  
Operation Conditions ◽  
Partial Load ◽  
Discharge Curve ◽  
Rotor Stator Interaction ◽  
High Head

The unsteady flow in a high-head pump-turbine whose head-discharge curve has the positive slopes at high-partial-load operation condition was investigated. It is noted that the numerical methods is very important for predicting this kind of head-discharge curve with positive slopes, and better agreement between calculation results and experimental data was achieved by using Spalart-Allmaras turbulence model and mesh strategy with y+ controlling for numerical simulation. From the analysis of hydraulic losses at different parts in the pump turbine, it is found that the head loss at the flow passage of the guide vane and stay vane was not small at pump mode. In order to make clear the reason why the positive slopes at head-discharge curve occur, the flow between the impeller exit and the inlet of spiral casing was checked carefully. Much intensive vortex was observed near the impeller shroud, and there was strong rotor stator interaction for those operation conditions with positive slope. It is suspected the instability such as positive slope at head-discharge curve was resulted from the vortex formation near the flow channel wall. Based on the flow analysis, the runner optimization was conducted so as to mitigate the intensive rotor stator interaction. It is noted that the pressure fluctuation as well as the flow pattern was improved by applying the optimized impeller.

scholarly journals Analysis of Rotor-Stator Interaction of a Pump-Turbine with Splitter Blades in a Pump Mode

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1465 ◽  
Author(s):  
Haiqin Song ◽  
Jinfeng Zhang ◽  
Ping Huang ◽  
Haikun Cai ◽  
Puyu Cao ◽  
...  
Keyword(s):  
Radial Force ◽  
Stable Operation ◽  
Power Station ◽  
Pump Turbine ◽  
Main Frequency ◽  
Pulsation Amplitude ◽  
Depth Analysis ◽  
Rotor Stator Interaction ◽  
Guide Blade ◽  
Pumped Storage

The pump-turbine is the core component of a pumped storage power station. This paper considers an in-depth analysis of the rotor-stator interaction characteristics under computational fluid dynamics (CFD) and experimental measurements of pump-turbine with splitter blades used in a domestic pumped storage power station. The results show that as the guide blade opening increases, the rotor-stator interaction of the pump-turbine intensifies and the magnitude of the runner radial force and its pulsation amplitude as well as the magnitude of the guide blade water moment and its pulsation amplitude also increase. In addition, when the opening degree increases from 9.8° to 17.5°, the influence on the main frequency is mainly reflected in the phase change. While the opening degree increases from 17.5° to 24.8°, the influence on the main frequency is mainly reflected in the amplitude change. Moreover, the amplitude of 5fn at opening 9.8° and opening 24.8° is greater than the optimal opening 17.5°, indicating that deviation from the optimal opening will aggravate the difference of rotor-stator interaction between splitter blades and guide blades. In the paper, the influence of guide blade openings on the rotor-stator interaction between the splitter guide blade is studied, which provides a theoretical reference for the stable operation of the pump-turbine.

Mechanism and influence factors of hydraulic fluctuations in a pump-turbine

2021 ◽  
pp. 095765092110285
Author(s):  
Xiaolong Fu ◽  
Deyou Li ◽  
Hongjie Wang ◽  
Guanghui Zhang ◽  
Xianzhu Wei
Keyword(s):  
Guide Vane ◽  
Three Dimensional ◽  
Influence Factors ◽  
Simulation Method ◽  
Power Station ◽  
Pump Turbine ◽  
Available Energy ◽  
Exciting Forces ◽  
Pump Storage Power ◽  
Pumped Storage

Pumped-storage power technology is currently the only available energy storage technology in the grid net, and its reliability is receiving attention increasingly. However, when a pump-turbine unit undergoes runaway transitions, hydraulic fluctuations intensively affect the reliable operation of a pumped-storage power station. To reduce hydraulic fluctuations, this study investigated the formation mechanism of hydraulic fluctuations and explored its influence factors. In this study, a developed one-dimensional and three-dimensional (1 D-3D) coupling simulation method was adopted. Transient runaway transitions of a pump-turbine with three different inertias (0.5 J, 1 J, and 2.0 J) at three different guide vane openings (21°, 15°, and 12°, respectively) were simulated and compared. The results suggest that, at smaller guide vane openings (15° and 12°), water hammer owing to the increase in rotational speed is the primary unstable issue compared to the pulsation of radial hydraulic exciting forces on the runner. However, at a larger guide vane opening (21°), the latter owing to the back-flow near the runner inlet is the primary unstable issue. Moreover, it is found that a sufficiently large inertia improves the hydraulic fluctuations of the pump-storage power station, particularly in reducing the pulsation of radial hydraulic exciting loads on the runner. The findings of this study provide a valuable reference for determining suitable rotor inertia.

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