bluuebunny/crossref_metadata_2025_split huggingface dataset:
Research on State Evaluation and Prediction System of Hydraulic Turbine Based on Pressure Pulsation Parameters
Authors: Jiang Xiaoping , Gao Xiang , Hu Jiawei , Wang Ziting , Wang Lele 
Published: June 2021

Abstract
The pressure pulsation parameter of hydraulic turbine is one of the important indexes reflecting hydraulic stability of hydraulic turbine. Based on the pressure pulsation of the turbine, the health condition of the turbine unit is evaluated and predicted in this paper. Based on the measured data of pressure pulsation at four characteristic position of the hydraulic turbine, clustering was conducted by k-means method, and the health status of the hydraulic turbine unit was evaluated by finding the optimal k value for health status classification. The time series relationship of pressure pulsation was determined, and the evaluation result was taken as the prediction feature to establish the trend prediction model of pressure pulsation of hydraulic turbine set based on the time series change of long and short term memory network (LSTM). To realize real-time health assessment and prediction of unit running state and achieve quantitative assessment of equipment health state can provide technical basis for guiding unit maintenance.
Production flexibility of small run-of-river power plants: KWGO smart-storage case study
Authors: Münch-Alligné C , Decaix J , Gaspoz A , Hasmatuchi V , Dreyer M , Nicolet C , Alimirzazadeh S , Zordan J , Manso P , Crettenand S 
Published: June 2021

Abstract
In the framework of the new Swiss feed-in-tariff system for Small Hydropower Plants (SHP), the aim of the SmallFLEX project, led by HES-SO Valais and performed in collaboration with EPFL, WSL, EAWAG, PVE and FMV, is to show how SHP can provide winter peak energy and ancillary services, whilst remaining eco-compatible. The pilot and demonstrator site selected is the new SHP of Gletsch-Oberwald (KWGO) owned by FMV and commissioned end of 2017. This run-of-river power plant is equipped with two six-jets Pelton turbine units featuring a maximum power of 7.5 MW each while the average annual power is lower than 5 MW, with a maximum of production during the summer. The capacity of infrastructure, equipment, and other adaptation measures to produce in a flexible way is being assessed while measuring the impact of this new operation on the environment, production and revenues. The paper focuses on the two experimental campaigns and the numerical simulations carried out to assess the flexibility of the power plant by means of smart use of existing infrastructure as additional storage volumes: the settling basin, the forebay and the upper part of the headrace tunnel.
Effect of Inlet Section of Circular Section Spiral Case on Performance of Ultra-Low Specific Speed Diagonal Flow Turbine
Authors: Li Yanpin , Chen Xiaoyu 
Published: June 2021

Abstract
Variation of section area at volute inlet is a key factor affecting turbine performance. By changing the inlet section of the turbine volute, the inlet angle of the guide vane is changed, so the guide vane parameters will also be changed, which will affect the turbine performance. In order to study the influence of different volute inlet section areas on the overall hydraulic performance of ultra-low specific speed diagonal flow turbine, this paper redesigns the volute inlet section area of an ultra-low specific speed diagonal flow turbine. On the premise of applying the same runner, seven different volute inlet circular sections are designed. The numerical simulation of the full flow channel is carried out for each scheme, and the influence of inlet circular section area of different volutes on hydraulic performance of the ultra-low specific speed diagonal flow turbine is analyzed and compared. The results show that with the increase of flow rate, the calculated head and runner loss of the turbine increase, and the hydraulic efficiency of the turbine first increases and then decreases. When the turbine runs under small flow conditions (less than rated flow), the hydraulic efficiency of the turbine increases with the decrease of the diameter of the inlet circular section of the volute. When the turbine operates under high flow condition (greater than rated flow), the hydraulic efficiency of the turbine decreases with the decrease of the diameter of the inlet circular section of the volute. Through comparative analysis of seven schemes, the optimum radius of the inlet circular section of volute for the ultra-low specific speed diagonal flow turbine is 127mm and the corresponding inlet angle of guide vane is 32°. At this time, the efficiency of the turbine is 81.59% and the calculated head is 4.821m. The flow pattern inside the turbine is more uniform without whirlpools. It provides a reference for future design of similar type turbines and selection of suitable volute inlet circular section area.
Numerical investigation on a double suction twin-screw multiphase pump
Authors: Sun S H , Wu P B , Guo P C , Yi G Z , Kovacevic A , Zhang H, , Wu G K 
Published: June 2021

Abstract
Based on the dynamic mesh technology, the moving grids of the double-suction screw multiphase pump were generated by the software SCORG. Then the three-dimensional transient simulation model was established to investigate the two-phase flow mechanism inside the screw pump under different inlet gas volume fraction (IGVF). The results show that the pressure inside the working chamber increases step by step from inlet to outlet and is symmetrical. The pressure drops sharply at the inlet of circumferential clearance and then decrease linearly in the clearance. The curved flow in suction and discharge flow passage causes the gas separation and high gas volume fraction (GVF) area in suction and discharge chamber. Four vortices in cross section of discharge pipe cause four high GVF areas due to the centrifugal force produced by the vortices. The high GVF areas scatter in working chambers and change slightly with the rotation angle except the last chamber under the IGVF 10%. The two-phase leakage flow shows layered flow where the gas concentrates at the bottom of the gap. Thus, the high GVF areas on the surface of the rotors mainly exist at the position of gaps. The work will provide instructions for improving its performance under high IGVF.
Research and development of visual numerical simulation software for transient process of hydropower station
Authors: Guo Wencheng , Zhou Jianzhong , Wang Bingbao 
Published: June 2021

Abstract
Transient process is the basis of the safe and stable operation of hydropower station. The calculation of transient process is realized by professional numerical simulation software. This paper presents the research and development of the visual numerical simulation software for transient process of hydropower station. The software is designed and developed based on the Java language and the Eclipse and IntelliJ IDEA development environment. The research and development thought contains five aspects. Firstly, the mathematical model for the transient process of hydropower station is established and the algorithm is adopted. The program for numerical simulation is designed. Secondly, based on the modularization design principle, the object modules and operating condition modules are designed and encapsulated. Thirdly, the user-oriented visual interface of the software is designed and programmed. The visual interface includes menu bar, toolbar and plotting area, which realize the drawing of topology of hydropower station, input of parameters, setting of calculation conditions and post-processing of calculation results. Fourthly, the foreground and background interaction based on graphic interface is achieved to realize the recognition of topology, automatic coding of object modules and transfer of foreground data. Finally, the mathematical model, algorithm, object modules, operating condition modules, visual interface and foreground and background interaction are integrated and the development of the visual numerical simulation software is completed. The visual numerical simulation software for transient process of hydropower station is a general software and has a friendly user interface. Test and application of practical engineering prove the correctness, reliability and precision of the software. The visual numerical simulation software provides a simple, practical and efficient tool for the calculation of transient process of hydropower station.
Turbine mode start-up simulation of a FSFC variable speed pump-turbine prototype – Part I: 1D simulation
Authors: Alligné S , Béguin A , Biner D , Münch-Alligné C , Hasmatuchi V , Hugo N , Avellan F , Dujic D , Nicolet C, 
Published: June 2021

Abstract
Variable speed hydroelectric units equipped with full size frequency converter (FSFC) offer high operational flexibility enabling fast operating point transitions which increase grid regulation capacities. The XFLEX HYDRO H2020 European research project aims to demonstrate flexibility of such technology at prototype scale. The Z’Mutt pumping station, part of the Grande Dixence hydroelectric scheme located in Switzerland, is one of the demonstrators focused on the FSFC technology with a new 5 MW reversible Francis pump-turbine which will be commissioned in 2021. This paper, divided in two parts, aims to simulate the turbine mode fast start-up sequence made possible with the use of a FSFC and to assess the unit damage by means of 1D and 3D CFD simulations. The part I of this paper presents the 1D hydraulic transient simulation results of start-up sequences of unit U5 considering both conventional fixed speed technology and variable speed technology. The time evolution of the unit’s operating point is used as input data for 3D CFD simulations of part II, aiming to assess the impeller damage. Different control strategies to use the FSFC for turbine mode start-up sequence are analysed. Advantages and limits of each strategy are discussed, and recommendation is made for the Z’Mutt prototype demonstrator.
One-dimensional numerical simulation of cavitation surge in pumping system considering cavity response delay
Authors: Watanabe S , Tsujimoto Y 
Published: June 2021

Abstract
Cavitation instabilities such as rotating cavitation and cavitation surge often occur in high speed turbopumps. In the present study, numerical simulation of cavitation surge, which numerically solves the one-dimensional momentum and continuity equations with modelled dynamic cavitation characteristics, is conducted. The phase lag of cavity response against the inlet pressure and the suction flow rate variations is modeled in the form of the first-order lag system considering that the frequency of cavitation surge is small. Differently from linear stability analysis made in our previous study, the equations are solved in time domain with retaining some of non-linear terms. The method is validated through the comparison with the stability analysis. Then the effect of phase lags in dynamic cavitation characteristics is examined.
Investigations on fatigue curves in dependency of water quality for nickel-martensitic steels
Authors: Leibing B , von Locquenghien F , Rückle D , Schellenberg G 
Published: June 2021

Abstract
With the need for flexible operation, Francis runners are exposed to various operating conditions outside the traditional operating range. To grant sufficient fatigue life, a deep knowledge of both loads and material behavior is mandatory. With the change in operation diverse stress amplitudes and number of cycles have to be considered for the comparison with fatigue curves. Hydro power turbines are exposed to possible corrosion attack due to the surrounding water environment, which is a relevant impact on the fatigue curves. Therefore an overview of parameters that influence the corrosivity will be given. From an evaluation of a database that contains water quality data of worldwide hydro power projects, different water qualities are defined to perform fatigue tests with the influence of a corrosive medium. For selected water qualities, preliminary material test results will be presented.
Turbine mode start-up simulation of a variable speed Francis pump-turbine prototype – Part II: 3-D unsteady CFD and FEM
Authors: Biner D. , Alligné S. , Hasmatuchi V. , Nicolet C. , Hugo N. , Avellan F. , Dujic D. , Münch-Alligné C. 
Published: June 2021

Abstract
The Z’Mutt pumping station, part of the Grande Dixence hydroelectric scheme, is one of the demonstrators of the XFLEX HYDRO project. A 5 MW reversible pump-turbine prototype equipped with a full-size frequency converter (FSFC) is used to investigate dynamic variable speed operation in pumping and generating mode. Since the FSFC converter is always connected to the electrical grid, the full rotational speed range of the motor-generator can theoretically be exploited. Furthermore, this technology enables fast operating point transitions and therefore increased grid regulation capacities. The advantages of the FSFC technology in generating mode are compared to a conventional fixed speed start-up with a variable speed start-up. The operating point trajectories are extracted from 1-D hydraulic transient simulations. Detailed hydrodynamic and structural aspects of the pump-turbine during the two start-up scenarios are further studied. Simplified unsteady 3-D CFD simulations and transient structural FEM analyses of the pump-turbine prototype are carried out to assess the harshness of the flow and to anticipate runner fatigue. The present work aims to point out potential mitigation of partial runner damages during start-up in generating mode using FSFC technology.
Measurement and simulation of the dynamic characteristics of plain and profiled annular seals
Authors: Kuhr M M G , Ludwig G , Pelz P F 
Published: June 2021

Abstract
The performance and reliability of turbomachinery is often limited by shaft vibrations induced by fluid forces of (i) plain or profiled annular seals, (ii) pistons and (iii) journal bearings. The rotordynamic coefficients namely, stiffness, damping and inertia of plain annular seals are in general calculated using the bulk-flow approach developed by Childs. However, when applying the calculation method to profiled gaps, especially those with non-symmetrical profiles, large differences between simulation and experimental data are reported. Furthermore, reliable experimental data as well as large databases including experimental and simulation results from a single author are limited. To overcome this, the paper introduces a unique active magnetic bearing test rig, built and operated at the Technische Universität Darmstadt as well as the corresponding simulation method to determine the rotordynamic influence of annular seals. An extensive experimental study is carried out investigating plain, symmetrically profiled and non-symmetrically profiled annular seals within the relevant parameter range for turbulent flow in pumps. The results are compared to the simulation results showing a significant influence of profiled gaps on the dynamic characteristics in comparison to plain annular seals. Furthermore, it is shown that symmetric and non-symmetric profiles have a different influence on the dynamic quantities inertia, damping and stiffness.
Velocity Measurements in Kaplan and Propeller Turbines: a review
Authors: Sotoudeh N , Raisee M , Cervantes M J 
Published: June 2021

Abstract
Complex geometry and flow regimes are present in different sections of hydraulic turbines and most operating conditions. In the past two decades, many pressure measurements have been performed on different sections. Such measurements do not reveal the details of the flow distribution. Velocity measurements are needed to obtain more detailed information. The aim of the present paper is to review the velocity measurements performed in hydraulic turbines, especially axial turbines, and highlight the remaining challenges according to the operating condition.
CFD analysis of flow pattern in S-Shape region for low specific speed Francis turbine
Authors: Kobayashi Katsutoshi , Tamura Yuta 
Published: June 2021

Abstract
In this research, a Francis turbine with low specific speed was analyzed by unsteady numerical simulation in case of S-Shape region appearing model test. It was found that S-Shape characteristics curve was caused by an increase of head. Firstly, the head was decreased in accordance with a decrease of flow rate. However, once a centrifugal force became larger, then a reverse flow appeared between guide vane and runner and the head was increased. And then, head was decreased with flow rate decreasing. In this research, operating conditions of flow rate were defined as three regions, first half of S-Shape region, just S-Shape region and last half of S-Shape region. The operating condition, where the head was decreased in accordance with the decrease of flow rate, was defined as the first half of S-Shape region. The operating condition, where the head was just being increased in accordance with the decrease of flow rate, was defined as the just S-Shape region. The operating condition after passing of the just S-Shape region was defined as the last half of S-Shape region. It was revealed that those three operating conditions showed a spectrum distribution of pressure fluctuation differently each other. A flow visualization analysis with numerical results was conducted to investigate the difference of pressure spectrum in three operating conditions. At the first half of S-Shape region, two groups of reverse flow were caused at chamber between guide vane and runner and revolving in same direction as runner rotation. At the just S-Shape, the reverse flows were circumferentially connected to build a long curved string. At the last half of S-Shape, the reverse flows were fully connected to build a round ring shape.
Analysis of Dynamic Stresses of Pump-Turbine Runner during Load Rejection Process in Turbine Mode
Authors: Chen Funan , Yang Xiaolong , Bi Huili , Mao Zhongyu , Luo Yongyao , Liujingshi  , Fan Hongang , Wang Zhengwei 
Published: June 2021

Abstract
During load rejection process, the rotation rate, head and discharge change a lot and the internal flow of the runner is complex, leading to fatigue cyclic loads on the runner. In some cases, fatigue cracks appear at the stress concentration location of the runner. This paper studied the dynamic stresses of a pump-turbine runner during load rejection process in turbine mode using finite element method. The hydraulic loads were obtained from CFD analysis, and the clearance flow was taken into consideration in the CFD simulation. The variation of performance characteristics was calculated through the one-dimensional method of characteristic (1D-MOC). The results show that the pressure on outer surfaces of runner changed the stress of the runner, and the rotation rate had a great influence on the dynamic stresses of the runner.
Parametric Design Tool for Development of a Radial Guide Vane Cascade for a Variable Speed Francis Turbine
Authors: Stojkovski Filip , Lazarevikj Marija , Markov Zoran 
Published: June 2021

Abstract
Hydropower as a part of the family of renewable energy sources represents an engineering and scientific field which inspires researchers to work on development of the systems and sub-systems in a way of optimizing the whole energy transformation process to obtain more efficient, flexible and reliable hydropower operation with the best possible water to energy ratio. This research is part of a Horizon 2020 HydroFlex project by the Norwegian University of Science and Technology (NTNU), where the main goal is development of a flexible hydropower generation. The guide vane cascade is one of the most crucial stationary sub-systems of the hydraulic turbine and is a subject of this study. Its re-design for obtaining a quality “flow-feeding” of a variable speed high head Francis turbine is developed. Having this goal in mind, a MATLAB code was generated, based on several key parameters, such as initial energy conditions as net head and turbine discharge at best efficiency point (BEP). Turbine runner geometrical constraints are taken into account during this process, while using recommendations for some initial guide vane calculations such as their number, inlet and outlet diameter, guide vane axis diameter, delivery angles etc. Using an inverse Euler turbine equation, the operating range of the turbine was calculated for a variable speed and discharge conditions, keeping the shock-free flow for all states at the runner’s inlet, as it is the most favourable inflow condition. For those operating points, the flow streamlines angles were obtained at the guide vanes leading and trailing edges. With an interpolating mathematical functions between the angles of the leading and trailing edges, the camber lines of the hydrofoils were obtained for further guide vane cascade geometry development. This algorithm can be implemented on any given runner geometry. The guide vane design is then exported into ANSYS Workbench for further numerical tests, such as CFD simulations for verifying the hydrodynamic characteristics and FEM analysis for verifying the structural integrity of this sub-system for variable speed operating conditions.
Numerical Investigation of flow instabilities in Speed No-Load operation of a Bulb turbine
Authors: Yamamoto K , Roubaty M , Morisod M , Coulaud M , Houde S 
Published: June 2021

Abstract
When operating in Speed-No-Load (SNL), turbines function at their synchronous rotating speed with a fraction of discharge at best efficiency point, ready for electrical grid connection. The flow in SNL condition is characterized by high swirling component leading to complex flow structures inside the runner, which generate wide-band pressure fluctuations. When operating in SNL condition, high specific speed turbines, such as axial turbines, can be damaged by significant pressure oscillations attributed to rotating vortex phenomena, alike rotating stall. However, understanding the fundamental flow dynamics behind the phenomena in SNL condition remains challenging due to the stochastic nature of flow. The present research highlights unsteady flow characteristics and flow instabilities in SNL condition of a bulb turbine by URANS simulations based on scale-resolving techniques. The simulation results provide evidence that the development of a rotating vortex array in precession with the runner is a major source of pressure oscillations and torque fluctuations in SNL operation of this bulb turbine.