bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effects of load reduction on forces and moments on the runner blades of a Kaplan turbine model
Authors: Nobilo Martina , Salehi Saeed , Nilsson Håkan 
Published: December 2024

Abstract
Today’s electric energy system includes more renewable sources than ever before, with a large increase in wind and solar power. The intermittency of wind and solar power brings certain challenges in maintaining the balance of the electric grid. Hydropower has shown great potential in solving the grid balancing problem. However, historically hydropower has had a completely different role, covering only the base load. The water turbines were designed to operate at the best efficiency point for most of their lifetime, and other kinds of operation may cause unpredictable shortening of the lifetime of the machines. Safe operation and planned maintenance are of great importance for both continuous energy distribution and human safety. In order to use the potential of hydropower to operate with highly variable loads, more comprehensive studies need to be made on the effects of transient operation of water turbines. An extensive series of studies have been made in recent years on the transient operation of Francis turbines and pump turbines. However, transient operations of Kaplan turbines require more in-depth studies. The present work analyses the flow-induced forces and resulting torques and bending moments on the U9-400 Kaplan turbine model runner blades during a load reduction sequence. New implementations in the OpenFOAM open-source CFD code have been developed to extract the forces, torques and bending moments on individual blades with respect to coordinate systems rotating with each individual blade.
A comparative analysis of CFD methodologies to predict the performance of Francis turbine
Authors: Mukherjee Arnab , Khullar Subodh , Zehab Ud Din Mohammad , Shekhar Pant Chandra , Kumar Arun 
Published: December 2024

Abstract
A Francis turbine’s flow characteristics strongly depend on the operating conditions. Accurately predicting the flow field within a turbine unit is challenging due to complex flow phenomena, such as separation around the turbine blades, pressure variations within the runner, and swirling flows in the draft tube. Various CFD methodologies can be employed to predict turbine performance. The present work evaluates the reliability of different CFD simulation methodologies in predicting turbine performance, focusing on the sensitivity of different turbulence models, grid types, and modeling approaches for accurate numerical solutions. Simulations are performed on a high-head Francis turbine under various operating conditions, including part load, Best Efficiency Point (BEP), and high load conditions, each representing a different turbine flow field. The simulation results are compared with experimental data from model tests to confirm the reliability of the numerical simulations for Francis turbines. The results show that the SST k-ω model with a hexahedral mesh (HH) is best suited for overall turbine performance prediction.
Combined air and water injection in Francis turbine draft tube at part load
Authors: Kumar Sandeep , Gandhi Bhupendra K 
Published: December 2024

Abstract
The flow instabilities and pressure pulsations at Part load (PL) are detrimental to the turbine’s life and performance. The present work reports the combined water and air injection in the draft tube (DT) cone. The water is injected through the center of the hub cone using a nozzle with a diameter of 12.7 mm. The air is admitted through the DT periphery. The water injection percentage 0.5% to 2% of the turbine inlet flow rate, and the air is injected at 0.5% to 2.5%. The spectral analysis assesses the pressure amplitude and dominating frequency affected by the combined water and air jet injection. The effect of combined air and water jet injection on synchronous (plunging) and asynchronous pressure pulsations (rotating) is analysed at two different measurement planes of the draft tube cone.
Experimental Investigations of Sediment Erosion in Guide Vanes of Francis Turbine
Authors: Poudel R , Chitrakar S , Qian Z , Guo Z , Thapa B 
Published: December 2024

Abstract
Guide vanes are the cascade of hydrofoil like structures surrounding the Francis turbine runner which guides the water from spiral casing and controls the flow to the turbine. A large portion of hydraulic energy of incoming flow is converted to kinetic energy within guide vanes. Sediment erosion causes deterioration of turbine components. Guide vanes are generally eroded due to sediments at the outlet region, facing plates, and clearance gap region. This research encompasses the study of erosion in guide vanes of a 2 kW capacity Francis turbine. The guide vanes were coated with four different coats of colour. The test rig was operated in maintaining erosive environment with an average concentration of sediment particles of 1400 ppm. The total time of operation was 36 hours and the observations were made at interval of each 4 hours. Observable patterns of erosion were seen at different location of guide vanes showing the areas prone to the effect of sediment erosion. The erosion was mostly observed at the trailing edge of the suction side of the guide vanes near to the top and bottom face. The pressure side of the guide vanes experienced a uniformly distributed erosion throughout the width at the leading edge. The causes of erosion were identified as high velocity and acceleration of sediment particles, vortex due to leakage flow and horse shoe vortices. The eroded weight of the guide vanes was recorded for 45 hours of rig operation in erosive environment. Cumulative erosion rate of 0.039 mg gm−1 hr−1 was quantified with an average percentage weight loss of 0.058% was observed in guide vanes.
Innovative Approaches to Hydraulic Turbine Advanced Condition Monitoring
Authors: Valentín D , Presas A , Egusquiza M , Egusquiza E , Drommi JL 
Published: December 2024

Abstract
This research paper introduces advancements in hydraulic turbine condition monitoring through the implementation of vibration-based condition indicators. Conventional methods rely on vibration monitoring systems, triggering alarms or unit trips based on overall measured values at specific points. However, these methods may generate false alarms under changing operating conditions, such as variations in head or flow rate. In response, our study focuses on the development and validation of condition indicators derived from vibration data, considering the turbine’s operating conditions. Our methodology defines and validates these condition indicators, providing a detailed understanding of the hydraulic turbine’s condition. By employing an enhanced condition monitoring framework, our approach not only improves fault detection accuracy but also offers a comprehensive perspective on the overall health of the turbine. Experimental results from a prototype Kaplan turbine showcase the effectiveness of our methodology in detecting and characterizing faults, enabling proactive maintenance strategies. The Kaplan turbine studied is one of the demonstrators of the XFLEX HYDRO project. In conclusion, this research delivers a valuable tool for industry professionals and researchers involved in hydraulic turbine maintenance and optimization.
Investigating the Impact of Stagger Angle on Double Suction Pump Performance through Computational Fluid Dynamics
Authors: Sonawat A , Hwang D H , Kim J H , Roh M S , Kim Y S 
Published: December 2024

Abstract
The double suction pump (DSP) is a centrifugal pump variant widely utilized in applications requiring higher head (H) and volumetric flow rates of fluid, owing to its ability to deliver robust performance under such conditions. In this study, computational fluid dynamics (CFD) techniques were employed to evaluate the performance of a designed DSP using a steady-state approach. Specifically, the investigation focused on assessing the impact of impeller stagger angle (θ) on pump performance under designed conditions. A comparative analysis was conducted between pumps equipped with staggered and non-staggered impellers to gauge their suitability across a broad range of flow rates. The stagger angle ranged from θ=0° to θ=30°, with θ=0° denoting a non-staggered impeller configuration. Results from the CFD study revealed that utilizing a staggered impeller arrangement led to improved pump performance in terms of head and efficiency compared to non-staggered impellers. However, performance variations with stagger angle adjustments between θ=15° and θ=30° were marginal, suggesting that stagger angle alterations had minimal impact on hydraulic performance under designed conditions. This preliminary investigation laid the groundwork for future unsteady simulations aimed at comprehensively assessing and understanding the unsteady pressure pulsations inherent in the designed pump. Leveraging CFD has helped the efficient acquisition of results and provided insights into the fluid flow dynamics within the pump.
The effects of flow rate on the performance of centrifugal pump as turbine based on entropy production theory
Authors: Liu Yunqi , Wang Tao , Lei Lei 
Published: December 2024

Abstract
Centrifugal pumps as turbines (PATs), economically feasible and energy-saving technologies, are commonly used in energy-intensive industrial operations. The entropy production theory was applied to study a forward-curved blade PAT by experimental and numerical simulation techniques. The findings demonstrate that the hydraulic efficiency reaches 75.65% at the design flow rate. The impeller and volute are where the majority of the energy loss occurs. In the low-flow condition, the shear force and the significant velocity gradient are the primary causes of energy loss in the low-flow condition. In the high-flow condition, the shock loss is greater, increasing turbulent entropy production power. There is very little correlation between flow rate and entropy production in the draft tube, the loss is mainly from the incoming flow state and the viscosity effect of the tube wall. This study helps understand the energy conversion mechanism of PAT, which has reference value for the efficient and economical operation of the PAT.
Behaviour of cavitation characteristics for various vane leading edge shapes of radial flow pump impeller
Authors: Stephen Christopher , Sivasailam Kumaraswamy 
Published: December 2024

Abstract
Cavitation is a dynamic phenomenon that degrades hydraulic machines performance. In a pump, the lowest static pressure occurs near the leading edge of the vane, which causes cavitation when it falls below the vapour pressure of the fluid at that prevailing temperature. For the cavitation studies, three different leading-edge profiles of the vane of a low specific speed pump are chosen. Plain, ellipse with semi-minor axis along vane course, and circular are the three leading edge profiles. The radial flow pump impeller was designed through point by point method to obtain the vane course from leading to trailing edge instead of single arc and double arc methods. In this method, smooth transitions of relative and meridional velocities were insisted from inlet to outlet radius. The leading edges of vanes as well as the vane course are cross verified through the coordinate measuring machine for its accuracy. Cavitation tests were performed at various constant flow rates and constant speeds by lowering the water level in the sump (which as 10 m deep from pump centre line) so that the pump transitioned from a non-cavitating to a cavitating state. Cavitation studies revealed that the leading edge has a significant impact on pump performance because the incidence flow angle is disturbed at the inlet. Although the leading-edge profile had little effect on overall performance, but it had a significant effect on cavitation. Detailed cavitation characteristics were arrived for different flow rates, speeds, and the leading edge profiles. It is reconfirmed that affinity law will not hold good for a pump with cavitation. Development of cavitation in impeller channel from the inception were visualised and compared for different leading edge profiles with reference net positive suction head. For all tested flow rates, the pump with a circular leading-edge impeller has a lower Net Positive Suction Head requirement than the pump with an ellipse or plain leading-edge impeller.
Estimate of the radial unsteady forces acting on a cavitating inducers from casing pressure measurements
Authors: Terrasse E , Roussette O , Queguineur M , Staudt H , Dazin A 
Published: December 2024

Abstract
This paper presents a methodology to estimate the radial forces acting on a cavitating inducers from the pressure signals measured at the machine casing by a set of sensors installed at different axial and azimuthal locations. The results of these methodologies are validated on the experimental data obtained on a water loop dedicated to the study of the performance and the unsteady phenomena in a cavitating inducer. The pressure and efforts are traced by unsteady pressure sensors on the pump casing and by a 6 components balance measuring efforts on the inducer shaft. For the validation, tests at two different rotating velocities were conducted during which a continuous pressure drop was imposed to the inducer, starting from a non cavitating operating point at given rotating speed and flow rate, down to a 20% pressure drop.
Preliminary design of adjustable Guide Vanes for PaTs in Pumped storage applications
Authors: Filannino Domenico , Stefanizzi Michele , Capurso Tommaso , Quattromini Rosada , Monteriso Rosario , Annese Francesco , Torresi Marco 
Published: December 2024

Abstract
Pumped-Storage Hydropower Plants (PSHPs) are a well-established technology for storing large amounts of energy and enhancing the power systems flexibility. In the framework of Micro and Mini Hydropower, Pumps as Turbines (PaTs) could represent a valid cost-effective solution also for PSHPs. Nonetheless, the lack of a control device could represent a problem, mainly with non-fixed operating conditions. Additionally, PaTs show generally a steep efficiency decrease at part load. Thus, since conventional PaTs do not present adjustable geometries, a preliminary sizing of an adjustable Inlet Guide Vane (IGV), referring to turbine mode, is proposed in this work. The aim of this work is to propose a methodology suitable to modify a baseline PaT introducing an adjustable IGV to perform a high efficient control in terms of flow rate and pressure drop. The machine selected for the proposed study is a centrifugal pump with a specific speed, nq
, equal to 16. The adjustable IGV are inserted between the volute cutwater and the impeller by reducing impeller diameter. To obtain an initial solution for the stationary blades row profile, a review of Francis turbines guide vanes design methods is conducted. Finally, a numerical study on the influence of guide vanes number is performed.
Experimental facility dedicated to detection and prediction of penstock fatigue induced by pressure oscillations
Authors: Hasmatuchi V , Rittiner R , Pires-Boyer S , Lecointre C L , Nicolet C , Münch-Alligné C , Rey-Mermet S 
Published: December 2024

Abstract
Hydroelectric powerplants play a vital role in the electricity production mix, especially during the ongoing energy transition towards renewable sources. However, they face operational challenges due to harmful stress loading of various components. Ensuring safe operation remains essential for people’s safety, electricity supply, and costs avoidance. The study focuses on penstocks and pipelines material damaging caused by fatigue, crack initiation and propagation. These critical components are often several decades old and expensive to refurbish or replace. Cycling loading, induced by pressure oscillations during start-stop or transient operations, accelerates material fatigue. Steel lining corrodes over time, and welds may contain original defects. To address this, a new testing facility that generates controlled cyclic pressure oscillations using the water hammer effect has been built. This specific closed-loop circuit allows accelerated fatigue testing of material probes, providing insights into crack initiation and propagation. The test rig operating principle is described while its 1D numerical model is introduced and validated with measurement data. The prediction of crack incipience and rupture of a tubular specimen with a pre-machined longitudinal weakening is in the end compared with the results of a fatigue test conducted on the test bench.
A machine learning based analysis of bearing vibrations for predictive maintenance in a hydropower plant
Authors: Lang Xiao , Nilsson Håkan , Mao Wengang 
Published: December 2024

Abstract
This study employs machine learning techniques to model bearing vibrations for predictive maintenance within a hydropower plant, utilizing over three years of full-scale vibration measurement data. Operational parameters, including turbine speed, guide vane opening, and generator active power, serve as input features to predict vibrations in both upper guide and turbine guide bearings. The models, developed from datasets across different periods, aim to predict and analyze discrepancies in future monitoring data to evaluate potential performance degradation. When the statistical distribution of the future monitoring data closely aligns with the training data, the models demonstrate a capacity to predict gradual bearing performance degradation effectively. However, when future monitoring data diverge significantly from the training set, traditional machine learning models produce irrational predictions, leading to unreasonable trends. To overcome these challenges, the adoption of more sophisticated machine learning approaches is recommended to enhance the reliability of predictive maintenance in the face of unseen data scenarios.
Water hammer control of pumped-storage power plant with two units under hydraulic short circuit operation
Authors: Cui Zilong , Guo Wencheng , Liu Yang , Cao Rui , Chen Zi , Wang Le , Bai Qijian , Zheng Yiming 
Published: December 2024

Abstract
This paper investigates the water hammer control of pumped-storage power plant (PSPP) with two units under hydraulic short circuit operation (HSCO). Firstly, the numerical model of PSPP with two units is established. Based on the sequences of accident shutdown of units under HSCO, two combined operating conditions (COCs) are presented. Then, the control objectives of water hammer pressure are designed to verify the safety of PSPP under HSCO. The superposition time is selected as the decision variable, and the values of control objectives are obtained by the whale optimization algorithm. Finally, the extreme water hammer pressures of two COCs, successive load rejections and successive pump outages are compared. The results indicate the sequences of accident shutdown of two units under HSCO have an impact on the water hammer control. For the two COCs, when the initial operating condition is load rejection, the maximum draft tube pressure and minimum draft tube pressure are more dangerous. The minimum volute pressure is almost not affected. During the actual operation of the PSPP, the COC should be avoided. Compared with successive load rejections and successive pump outages, the accident shutdown under HSCO is the most unfavourable for the control of maximum draft tube pressure.
Increasing grid flexibility through ancillary services – Virtual Inertia and Fast Frequency Response implementation and testing in a PSPP with double-fed induction machines
Authors: Merbeth (né Sarodnik) R , Schönborn B , Bruns M , Jung A R 
Published: December 2024

Abstract
This paper describes the implementation and testing of Virtual Inertia (VI) and Fast Frequency Response (FFR) at the Frades 2 pumped storage power plant (PSPP) in Portugal to verify preceding numerical investigations and to demonstrate the potential of these ancillary services. This work was part of the activities of the EU-funded H2020 project XFLEX HYDRO. Frades 2 is equipped with two reversible Francis-type pump turbines, each coupled to a 420 MVA double-fed induction machine. The test results are compared to numerical simulations for various grid frequency scenarios in generating and pumping mode. It is shown that a single unit in VI mode can inject or extract a peak load of ±110 MW within less than 500 ms in to support the grid in the case of a sudden frequency change. In FFR mode the units can provide control energy of 40 MW in less than 2000 ms. The impact of these modes on wear and tear of the asset is analysed by means of strain gauge and shaft torque data collected during the site test campaign.
CFD Simulation of the turbine start-up of a pump-turbine with investigation of the usage of a porous domain for modelling very small guide vane angles
Authors: Zorn M , Riedelbauch S 
Published: December 2024

Abstract
With increasing number of transient operations, such as start and stop procedures in pump-turbines, CFD simulations of these sequences have become more important to understand the occurring flow phenomena and evaluate their impact on the pump-turbines lifetime. In the present work, the numerical setup for transient CFD simulations is discussed and a CFD simulation of a turbine start-up using a 29 million node mesh and the SBES turbulence model is carried out. The results demonstrate reasonable accuracy when comparing the overall trends with the available measurement data. However, significant underestimation of torque fluctuations as well as draft tube pressure fluctuations during the initial phase of the start-up is observed. In a subsequent study, the modelling of very small guide vane angles by a porous domain is investigated. An analytical function for the loss coefficient of the porous domain is applied up to different threshold values of the guide vane angle. A guide vane angle of 1° is identified as the best option regarding accuracy and computational effort.
Optimization of a diffuser augmented kinetic turbine with the island model
Authors: Tismer A , Riedelbauch S 
Published: December 2024

Abstract
An augmented kinetic turbine with a sectioned diffuser parameterized with thirty degrees of freedom is optimized using computational flow field simulations combined with the island model for parallelizing the optimization. The geometry and mesh generation is performed with an in-house design framework. The parallel optimization and the necessary database for migration are implemented in Python. For all runs an evolutionary optimization algorithm is used. Three different groups of runs with different initializations and migration strategies are investigated. The study shows good speedup values for a diverse initialization in combination with the database migration. Moreover, for several runs, a superior speedup value is observed. Additionally, the database migration handles homogeneous initializations better than commonly used strategies.