Transient Pressure Analysis of a Prototype Pump Turbine: Field Tests and Simulation

2018 ◽  
Vol 140 (7) ◽  
Author(s):  
Jinhong Hu ◽  
Jiandong Yang ◽  
Wei Zeng ◽  
Jiebin Yang
Keyword(s):  
Field Tests ◽  
Water Hammer ◽  
Hydropower Plant ◽  
Pressure Pulsations ◽  
Transient Pressure ◽  
Pump Turbine ◽  
Operation Conditions ◽  
Spiral Case ◽  
Transient Events ◽  
Transient Variations

The transient behaviors of a prototype pump turbine are very important to the safe operation of a pumped-storage power plant. This is because the water hammer pressure during transient events affects the pressure surges in the spiral case (SC) and the draft tube (DT). In addition, the transient pressure pulsations in the vaneless space (VL) are important in the evaluation of the life of the runner. Although several detailed studies have been conducted on the water hammer pressure of a hydropower plant, very few have considered the transient pressure pulsations that occur in the pump turbine. The objective of the present study was to determine the characteristics of the transient pressure pulsations of a 300-MW prototype Francis pump turbine during load rejection and power failure. For this purpose, the frequency features in the steady-state were first analyzed using fast Fourier transform. A Savitzky–Golay filter was then used to extract the water hammer pressure and pulsating pressure from the acquired raw pressure signals. Further, a one-dimensional (1D) method of characteristics (MOC) mathematical model of the pump-turbine was established and used to simulate the transient variations of the flow discharge during transient events, to enable the division of the transient operation conditions into several domains. Finally, the characteristics of the transient pressure pulsations in the SC, vaneless space, and DT were investigated in the time and frequency domains. This paper also discusses the causes of the pressure pulsations that occur under different modes of operation of a pump turbine.

Transient Pressure Pulsations of a Model Pump-Turbine During Power Failure

2017 ◽  
Author(s):  
Jinhong Hu ◽  
Wei Zeng ◽  
Jiandong Yang ◽  
Renbo Tang
Keyword(s):  
Rotational Speed ◽  
Guide Vane ◽  
Dynamic Pressure ◽  
Pressure Sensors ◽  
Open Loop ◽  
Operating Conditions ◽  
Pressure Pulsations ◽  
Transient Pressure ◽  
Pump Turbine ◽  
Power Failure

Pump-turbine can operate in either pump mode or turbine mode. The quick response to load changes as well as the ability to store energy makes it essential to the stability of power grid. When a pump-turbine works in different condition, flow-induced instabilities occur, including Rotor Stator Interaction (RSI) between the runner and vanes, vortex formations and back flow regions. To understand these complicated flow dynamics, experimental and numerical investigations have been conducted by many researchers. Among these researches, many experiments on model test rigs are mainly focused on steady state, and knowledge for instabilities during transients is still lacking. In this paper, power failure experiments with constant guide van opening are conducted on an open-loop test rig. During the process, the operating point of the pump-turbine in the 4 quadrant characteristics moves from pump region through the brake region, turbine region to turbine brake region. Finally the pump-turbine settled down at runaway rotational speed. In our experiments, flow rate, rotational speed, torque, pressure in the spiral casing and the draft tube inlet are measured. Especially, dynamic pressure sensors mounted in the guide vane channels are used to measure transient pressure pulsations. Measured data are analyzed in both time domain and frequency domain. Results indicate that during power failure pressure pulsations in the vane channels vary significantly with the operating conditions. In the pump region, pressure pulsations are mainly composed of RSI. In the brake region, intensive stochastic noises occur, and the amplitude of RSI rises. In the turbine region, the magnitude of pressure pulsations drops sharply as the noise intensity goes down. In the turbine brake region, significant noises appear, and the amplitude of RSI increases dramatically.

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.

Simulation, controller design and field tests for a hydropower plant—A case study

Automatica ◽  
1990 ◽  
Vol 26 (3) ◽  
pp. 475-485 ◽  
Author(s):  
Karl Heinz Fasol ◽  
Georg Michael Pohl
Keyword(s):  
Controller Design ◽  
Field Tests ◽  
Hydropower Plant

Field Tests of Guide Vanes and Runner Blades of a Large Bulb Turbine for Output Deficiency Diagnosis

2012 ◽  
Vol 212-213 ◽  
pp. 1057-1061 ◽  
Author(s):  
Zhong Liu ◽  
Zhu Qing Huang ◽  
Shu Yun Zou ◽  
Hong De Rao
Keyword(s):  
Field Tests ◽  
Economic Loss ◽  
Hydropower Plant ◽  
Test Results ◽  
Guide Vanes ◽  
Factors Affecting ◽  
Runner Blade ◽  
Main Factors ◽  
Theoretical Analyses ◽  
Bulb Turbine

The 3# bulb turbine in Hongjiang Hydropower Plant has faced the problem of output deficiency since its commission in Sept. 2003, which caused a large economic loss. Following simple theoretical analyses on the main factors affecting the turbine’s output and efficiency, the field test schemes were determined to measure the shapes and intervals of guide vanes and runner blades of the 3#, 5# and 6# turbines. The test results discover that the average blade intervals of the 3# turbine are generally less than those of the 5# one. Suggestions on runner blade installation adjustment and combined curve modification are given.

scholarly journals Water Hammer Control Analysis of an Intelligent Surge Tank with Spring Self-Adaptive Auxiliary Control System

Energies ◽  
2019 ◽  
Vol 12 (13) ◽  
pp. 2527 ◽  
Author(s):  
Wuyi Wan ◽  
Boran Zhang ◽  
Xiaoyi Chen ◽  
Jijian Lian
Keyword(s):  
Control Function ◽  
Water Hammer ◽  
Control Device ◽  
Control Analysis ◽  
Surge Tank ◽  
Transient Pressure ◽  
Supply Pipe ◽  
Proposed Model ◽  
Vertical Size ◽  
Self Adaptive

The water hammer can cause great risks in water supply pipe systems. A surge tank is a kind of general water hammer control device. In order to improve the behavior of the surge tank, a self-adaptive auxiliary control (SAC) system was proposed in this paper. The system can optimize the response of the surge tank according to the transient pressure. The numerical model and the matched boundary conditions were established to simulate the improved surge tank and optimize the SAC system. Then, various transient responses were simulated by the proposed model with different parameters set. The proposed system is validated by comparing the water hammer process in a river-pipe-valve (RLV) system with and without SAC. The results show that the SAC can greatly improve the water hammer control of the pipeline and the water level oscillation of the surge tank. With the SAC system, the required vertical size of the surge tank can be significantly reduced with the desired water hammer control function.

Mechanism of Fast Transition of Pressure Pulsations in the Vaneless Space of a Model Pump-Turbine During Runaway

2019 ◽  
Vol 141 (12) ◽  
Author(s):  
Xiaoxi Zhang ◽  
Wei Zeng ◽  
Yongguang Cheng ◽  
Zhiyan Yang ◽  
Qiuhua Chen ◽  
...  
Keyword(s):  
Transient Flow ◽  
Characteristic Curve ◽  
Three Dimensional ◽  
Low Frequency ◽  
Vortex Structures ◽  
Pressure Pulsations ◽  
Pump Turbine ◽  
Whole Process ◽  
Time Variations ◽  
Flow Vortex

The pressure pulsations in the vaneless space of pump-turbines are extremely intense and always experience rapid time variations during transient scenarios, causing structural vibrations and even more serious accidents. In this study, the mechanism behind the rapid time variations of the vaneless space pressure pulsations in a model pump-turbine during runaway was analyzed through three-dimensional (3D) numerical simulations. These results show that the high-frequency pressure pulsation components originating from rotor–stator interactions (RSI) are dominant during the whole process. These components fluctuate significantly in frequency when the working point goes through the S-shaped region of the characteristic curve, with the amplitudes increasing. Meanwhile, some low-frequency pulsations are also enhanced and become obvious. These features can be attributed to the transitions of the inter blade vortex structures (IBVSs) to the forward flow vortex structures (FFVSs) and the back flow vortex structures (BFVSs) at the impeller entrance, when the pump-turbine operates in the region with S-shaped characteristics. The FFVSs mainly cause decreases in frequency and introduce low-frequency pulsations, while the BFVSs are responsible for the unstable fluctuations. These findings contribute to the understanding of how transient flow patterns evolve and may provide new ideas about avoiding severe pressure pulsations caused by rotating stalls in the pump-turbine during transient scenarios.

Study on Friction Coefficient of Spiral Case with Cushion Layer in Large-Scale Hydropower Plant

2011 ◽  
Vol 71-78 ◽  
pp. 4248-4251
Author(s):  
Jian Wei Zhang ◽  
Yi Na Zhang ◽  
Shu Fang Yuan
Keyword(s):  
Coefficient Of Friction ◽  
Large Scale ◽  
Water Pressure ◽  
Structural Type ◽  
Hydropower Plant ◽  
Finite Element Program ◽  
Spiral Case ◽  
Element Program ◽  
Cushion Layer ◽  
Elastic Cushion

Elastic cushion layer between the steel spiral case and surrounding concrete is often used as a structural type in large-scale hydropower plant in China. In view of the uncertainty of the optimal elastic coefficient of friction and the transfer mechanism of internal water pressure to the surrounding concrete, Spiral case with cushion layer of large-scale hydropower plant is simulated with ANSYS nonlinear finite element program, considering the slip contact characteristics between steel spiral case and the surrounding concrete, the more reasonable coefficient of friction between the steel spiral case and concrete is studied. This provides reliable theoretical analysis for the design of large-scale hydropower plants.

Application of Pressure Regulating Valve in the Hydraulic Transients of Hydropower Plant

2008 ◽  
Author(s):  
Jian Zhang ◽  
Shibo Ma ◽  
Jianyong Hu ◽  
Xiaodong Yu ◽  
Fulin Cai
Keyword(s):  
Guide Vane ◽  
Sudden Change ◽  
Pressure Rise ◽  
Hydropower Plant ◽  
Hydropower Station ◽  
Hydraulic Transients ◽  
Effective Measure ◽  
Spiral Case ◽  
Water Conveyance ◽  
Turbine Guide Vane

In the operation of the hydropower station, the sudden change of load in the large range often happen, the emergency closing law of turbine guide vane is difficult to control speed-rise and pressure-rise to the extent permitted for the length of pressure pipeline longer and discharge larger. With the development of the surge chamber of alternative technique, the pressure regulating valve is used to reduce the large pressure and speed-rise of the unit in hydraulic transients as the effective measure to saving investments. The layout of water conveyance system and process of hydraulic transients of a certain hydropower in China are analyzed, and the pressure regulating valve is installed in the spiral case inlet to meet the hydraulic regulation calculation guarantee after technical and economic comparison, for the joint action of valve and turbine guide vane, the pipeline water hammer pressure and unit speed-rise are reduced effectively. The pressure regulating valve diameter and opening and closing law in combination with the turbine guide vane are discussed in the power station, as well as the possible problems may be caused by the using of the pressure regulating valve is pointed out in theory. The achievements to scheme decision of adopting the pressure regulating valve to replace the surge chamber in high-head hydropower station with longer pressure water conveyance system can be for reference and provide the certain technological supply.

Hydraulic Stability Analysis of a Large Prototype Francis Turbine Based on Field Test

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Weiyu Wang ◽  
Qijuan Chen ◽  
Donglin Yan
Keyword(s):  
Full Range ◽  
Pressure Fluctuations ◽  
Field Tests ◽  
Francis Turbine ◽  
Operation Conditions ◽  
Amplitude Increase ◽  
Long Time ◽  
The Time Domain ◽  
Frequency Band Energy ◽  
Hydraulic Stability

Long time field tests of a 200 MW prototype Francis turbine over its full range of operation were conducted. From the experimental data, the time domain and frequency domain characteristics of the pressure fluctuations in the Francis turbine at different operation conditions were analyzed. Furthermore, the reason for the amplitude increase of pressure fluctuations and the correlation between the vibration and the pressure fluctuation was studied by using a multidimensional frequency band energy ratio analysis method. Based on the above analysis, some hydraulic stability characteristics of the large prototype Francis turbine are found, and other results are also obtained.

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