bluuebunny/crossref_metadata_2025 huggingface dataset:
Evolutionary game analysis of recycling management of waste power batteries of new energy vehicles
Authors: Wang Cheng gong , Liu Juan juan
Published: June 2021

Based on the evolutionary game theory, this paper constructs a game model between the government and power battery manufacturers with the aim of promoting the innovation of recycling technology to achieve sustainable development of energy and environment. The effects of penalties and subsidies on the behavior of power battery manufacturers in adopting green innovation technology strategies under unilateral and bilateral government policies are compared. Numerical simulations are used to verify the validity of the model and conclude that: penalties and subsidies can change the final choice of power battery manufacturers only when a certain threshold is exceeded; penalties can make power battery manufacturers adopt green innovation technology strategies more steadily than subsidies at an earlier stage when the green innovation technology surplus is negative; the number of recycling and the degree of technological innovation are also important factors affecting the evolutionary process of power battery manufacturers. Meanwhile, the above conclusions can provide some suggestions for the government to effectively manage the recycling of waste power batteries.
The Development of Automated Testing Acquisition Terminal
Authors: Qing HE , Ge-wei Zhuang , Zhen GU , Hong-hong Zhang , Lei Zhou , Jing-yue Zhang
Published: June 2021

With the mature of single phase intelligent electric meter automation detection technology, concentrator and shift acquisition terminal also need to implement automated testing. The current domestic reality for some measuring equipment in the production of automated verification or a link in the test, which still have some technical problems. It combined with the necessary human intervention, virtually increased the cost and certain security hidden danger, make the lost of the role of automation and automated verification or testing is true meaning. However, how to realize the automation of collection terminal detection is mainly to solve the problem. For intelligent electricity information collection system construction, the problems arising from the use and application, put forward to realize the automatic acquisition terminal detection scheme, for the domestic intelligent electricity information acquisition terminal test provide beneficial guidance and reference.
Preparation and Properties of Rice Hull Ash as the catalysis supporter in the fluidized-bed reactor
Authors: Teng Zhaohui , Huang Shan , Xu Heng , Li Na , Zhou Qulan
Published: June 2021

This research focuses on the preparation and properties of rice hull ash(RHA). We prepared RHA from combustion of rice husk in the fluidized-bed reactor. The temperature field of the furnace was steady and bellow 850°C to keep SiO2 amorphous. XRD, BET and SEM were applied in the characterization tests to investigate the effect of flow rate(u), the higher primary-secondary wind ratio(i) and relative height of bed material. The optimal combustion condition for preparing RHA was discussed. RHA obtained from rice hull contains abundant amorphous SiO2 (>90%) and the characterization results of RHA show its potential to be a good catalyst supporter.
Research on tip clearance leakage flow field characteristics of tidal energy hydroelectric unit based on NACA0009 hydrofoil
Authors: Wang Xiaohang , Li Chenhao , Zhu Guojun
Published: June 2021

In the rotor passage of tidal energy hydroelectric unit, there is a tip leakage problem between rotor and runner chamber. In order to research the flow characteristics of tidal energy hydroelectric units and explore the control method of tip leakage, based on the experimental data of NACA0009 hydrofoil, the SST-CC turbulence model was used for numerical simulation and compared with the experimental results. The characteristics of tip leakage flow and vortex were analysed under different hydrofoil shapes and gap widths. The results show that the rounded hydrofoil can effectively control the generation of tip separation vortex, but the rectangular hydrofoil has higher vortices coefficient and lower pressure coefficient in the downstream section; the tip leakage amount will increase with the increase of gap width; the tip vortex intensity will increase first and then decrease, and cavitation may occur when the vortices is maximum. The results can provide reference for studying the control method of tidal energy hydraulic machinery clearance leakage.
Study on the response of ecosystem services to land use
Authors: Zhao LiLi
Published: June 2021

In recent years, the urbanization process in counties has been accelerated due to the support of national policies. The depth and breadth of land use changes in counties have been strengthened, and the value of ecosystem services has been significantly degraded. In order to realize the sustainable development of county ecological environment, it is especially urgent to grasp the impact of different land use types in the county on the value of ecosystem services within a certain period of time. Based on the interpretation of remote sensing satellite images to obtain county land use classification data, the changes in the value of ecosystem services in Nanping City between 1995 and 2015 were explored in depth. The results of the study showed that the total value of ecosystem services in each region changed significantly in different time periods, among which, in 1995, the total value of ecosystem service types in Jian’ou City was the highest. In 2015, the value of ecosystem services in Songxi County decreased the most, amounting to 13.98 billion yuan, while other regions had different degrees of increase. Each regional service type has the highest value of functions such as soil formation and protection, water conservation, gas regulation and biodiversity conservation, while all the food production functions have the lowest value.
Research on Multi-layer combined Mining of EGS based on Downhole Decoder Technology
Authors: zheng Huang , Yanting Zhang , Hao Zhang , Lin Wang , Jingyu XU , Guangzhi Zhang
Published: June 2021

EGS system is a single-layer heat exchanger system. Because of its output requirements, the temperature drop of the heat exchanger layer is very significant in the expected production stage. At the same time, due to the uncontrollable conditions of the storage tank, the generation of calorific value can not be accurately controlled, so the optimization of the existing EGS heat transfer research is not comprehensive. The solution to this problem is to design a three-tube and six-control EGS technology, which is based on the structure of multi-layer heat exchangers. This technology can control the stratified flow, ensure the medium production, avoid the problem of large temperature gradient in the heat exchanger layer caused by large single layer flow, and provide some reference for conventional and unconventional oil and gas co-production technology.
The enrichment law of tight sandstone gas in member 2 of Xujiahe in Yingshan gas field, Sichuan Basin
Authors: youzhi Wang , Linna Wu , Simiao Zhu , Zhiguo Wang , Haiyan Wang , Jiayin He , Yunfeng Zhang
Published: June 2021

The enrichment law of desserts in Xujiahe formation of Sichuan Basin has become the core problem of tight sandstone gas reservoir. In view of this problem, taking the member 2 of Xujiahe Formation in Yingshan area of Sichuan Basin as an example, the author analyzes the main factors of enrichment of natural gas through the analysis of the basic geological features of sedimentary environment, reservoir, hydrocarbon source, structure and reservoir formation, and then discusses enrichment mode of natural gas. The results show that the reservoir forming conditions of member 2 in Yingshan area are superior, and the widely covered source rocks are developed, and the source rocks have good hydrocarbon generation potential. The sand bodies in the delta front with thick layers are deposited in member 2 of Xujiahe, which is distributed in large area, which lays the foundation for the development of high-quality reservoirs. The reservoir space types are various, mainly mainly including primary intergranular pores, dissolution pores and micro fractures, and the reservoir has good physical properties. The accumulation of natural gas in Yingshan structure is the result of coupling of the following factors: the development of high-quality reservoir controls the distribution of natural gas; the structural background is conducive to the enrichment of natural gas; the good matching relationship between faults and traps controls the differential accumulation of natural gas in the reservoir.
Study on night heating design of solar thermal storage system in winter based on CFD
Authors: Yu Zhang , Xue Wang , Ruoyu Wang
Published: June 2021

With the gradual maturity of solar heating system, more and more houses are equipped with solar heating equipment for heating. In view of the heating effect of the movable plate house, this paper selects the coldest monthly average temperature of -15 °C in Jinan as the external condition, designs the wall embedded heating coil with water as the medium, and uses CFD simulation software to establish the geometric model of the temperature distribution of the house in 7 hours after 10 pm. The simulation results show that when the overall wall is covered with heating coil, the nighttime temperature of the indoor personnel rest area is above 7 °C without considering the heat transfer effect between the personnel themselves and the internal space of the house. If the wall is covered with heating coil, the indoor average temperature will be no less than 12 °C. Solar energy contribution rate can reach more than 43.15 %, energy saving effect is obvious.
Review on research and application of phase change materials in cold storage refrigerator
Authors: Li Yang , Yang Dazhang , Xie Jing , Wang Jinfeng
Published: June 2021

Phase change material energy storage technology can effectively improve energy efficiency and alleviate environmental deterioration. Therefore, it is widely used in cold chain equipment such as cold storage refrigerators. In this paper, the low-temperature phase change materials (Tm<10°C) for refrigerators were reviewed, and the advantages, disadvantages and research of each phase change material were analyzed and compared. In addition, this paper reviews the effect of microcapsule technology on the properties of low-temperature phase change materials, and introduces the application of cold storage refrigerator in food and pharmaceutical cold chain. Finally, the research direction of cold storage refrigerator is prospected and the key problems to be solved are put forward.
Analysis of Influencing Factors of Groundwater Nitrate Nitrogen Driven by Sewage Reuse
Authors: Jing Ping , Wang Zuzheng
Published: June 2021

Groundwater safety issues directly affect human health and quality of life. Sewage reuse is the main source of nitrate nitrogen pollution. The influencing factors of groundwater nitrate nitrogen must be analyzed to reduce the pollution risk of nitrate nitrogen. Based on the analysis of the literature, the influencing factors are comprehensively analyzed in the process of nitrate-nitrogen migration and transformation, and the influence of natural factors are discussed such as landform characteristics, soil type and soil structure on the migration of nitrate-nitrogen. The impact of human factors such as Nitrogen application, sewage irrigation, land use types and land planting ways are also analyzed, and the research results provide theoretical and scientific basis to support the remediation of groundwater nitrate nitrogen pollution, and can be used as reference.
Degradation Performance of Petroleum-Hydrocarbon-Degrading Bacteria and its Application in Remediation of Oil Contaminated Soil
Authors: Wei Xiaona , Peng Pai , Meng Yao , Li TingTing , Fan ZhiPing , Wang Qiong , Chen JiaBo
Published: June 2021

Three petroleum degrading strains were obtained from oily sludge and denoted as A2 (Pseudomonas putida), A4 (Acinetobacter calcoaceticus) and L5 (Sphingomona sp). Crude oil degradation experiments were conducted to investigate the degradation performances of the strains and their bacterial consortium(C) on crude oil. The petroleum degradation rates of A2, A4, L5, and C were 42.8%, 48.01%, 26.56%, and 81.07%, respectively, after 28 days of cultivation, illustrating the removal of petroleum hydrocarbons by the bacterial consortium had a synergistic effect. The bacterial consortium was used to remediate oil contaminated soil in laboratory and the remediation results of the different microbial addition methods-free bacterial consortium (TB), biochar-free bacterial consortium (TB-BC), and biochar-immobilized bacterial consortium (CTB) were compared. The results showed that biochar was beneficial to the colonization of degrading bacteria in the soil, and the number of microorganisms, dehydrogenase activity, and intensity of soil respiration in the CTB treatment were considerably improved compared with those in the other treatments. The removal rates of petroleum hydrocarbons were 18.0% and 32.51% higher than those of the TB-BC treatment and the TB treatment, respectively, indicating that the biochar-immobilized bacterial consortium had a synergistic mechanism of bioaugmentation and biostimulation for the removal of petroleum hydrocarbons.
Environmental Benefit Analysis of Hot Central Plant Recycling Asphalt Pavement Based on LCA
Authors: Zhu D L , Wang J , Gu L X
Published: June 2021

In order to determine the energy-saving and emission-reduction effects of the application of hot central plant recycling in the highway asphalt pavement maintenance project, this study selects a road section of overhaul project in Tongren as the analysis object, and adopt the environmental benefit analysis method based on life cycle assessment to analyze the energy consumption and environmental emissions of hot central plant recycling and hot mix asphalt. The comparison shows that the application of hot central plant recycling in highway asphalt pavement maintenance project has good energy saving and emission reduction benefits, and the aggregate and asphalt production stage are the main components. Moreover, under the condition of ensuring the road performance of recycled pavement, with the increasing proportion of reclaimed asphalt pavement, the environmental benefit of recycled pavement is higher. While with the increase of reclaimed asphalt pavement transportation distance, the environmental benefit presents a downward trend.
Optimization of biomass collection, transportation and storage processes empowered by blockchain technology
Authors: Xiaocong Zhang , Yang Yang , Zhilei Wu
Published: June 2021

As an important renewable alternative energy source, one of the most critical aspects that can be used reasonably is the improvement of the biomass energy supply chain. In view of the uncontrollable transportation process in the biomass energy supply chain, Blockchain technology(BT) is introduced to optimize the biomass energy collection, transportation, and storage processes. On this basis, the game model is applied to analyze the impact of BT on the members of the biomass supply chain and the overall profit of the supply chain. Research shows that the application of BT is beneficial to increase the profits of biomass energy supply chain members within the threshold range, and for the overall benefit of the supply chain, the overall benefit of the supply chain under centralized decision-making is the highest.
Feasibility study of biomass energy application in a project
Authors: Zhao Minmin , Zhang Wenwen
Published: June 2021

Combined with the characteristics of the project, this paper analyzes the application potential of biomass energy in the project area, introduces the technical route used in the project, studies the development and application of biomass gasification technology, and analyzes the economy of biomass energy application. This paper demonstrates the feasibility of biomass energy application in the project from the aspects of technology, social benefit, energy saving benefit and environmental protection benefit.
Advanced Optimization Tools for Hydro Turbine Runner Design
Authors: Lestriez R , Calvo D , Mendicino D
Published: June 2021

The objective of this work is to show how advanced optimization tools can be used for hydraulic turbine design, taking the example of a Francis runner design (new or refurbishment project). The public test case considered corresponds to a R&D turbine model of specific speed Ns = 0.5, originally developed at the Hydraulic Machinery Laboratory (LMH) of École Polytechnique Fédérale de Lausanne (EPFL). Firstly, a standard Computational Fluid Dynamics (CFD) process is used to predict performances, in the form of efficiency and cavitation behaviour. It features structured mesh for distributor (stay vane and guide vane), runner and draft tube. Automatic scripts are created to run computations for several guide vane openings and rotation speeds, covering the whole range of operating conditions, and allowing to obtain numerical hill charts of efficiency and minimum pressure to predict the occurrence of cavitation. Secondly, some operating points are purposefully selected for the optimization and objectives are defined to maximize efficiency while constraints are set for preventing cavitation. To continue with, a parametric blade model is defined: 3D blade shape is obtained from blade to blade sections and a stacking law. Sections are defined by camber and thickness. Finally, a Surrogate Based Optimization (SBO) with Evolutionary Algorithm (EA) is used for searching a global optimum. Design of Experiment (DOE) techniques are employed to efficiently define a database. Dynamic monitoring, data-mining and visualization tools are used; including Leave-One-Out (LOO), Analysis of Variance (ANOVA) and Self-Organizing Maps (SOM), with the objective of facilitating surrogate reliability assessment and a comprehensive understanding of key factors of the problem studied. This methodology is tested iteratively with the Francis Runner Hydraulic design: a first optimization is run, analysed and used to define a second optimization that shows increased benefits in particular for Best Efficiency Point. The results are analysed from a hydraulic point of view to identify the benefits and effects of the last optimization.
An experimental study on the upper part-load elliptical vortex instability in a Francis turbine
Authors: Amini Ali , Vagnoni Elena , Favrel Arthur , Yamaishi Kazuhiko , Müller Andres , Avellan François
Published: June 2021

This paper presents preliminary results of an experimental study on the occurrence and development of the upper part-load instability in a reduced-scale Francis turbine. The study includes draft tube pressure measurements, high-speed flow visualization, and particle image velocimetry. Our results reveal that for an operating point within the range of the upper part-load instability (70 to 85 % of the nominal discharge), the vortex rope has a circular cross section in non-cavitating conditions, which is preserved even after the appearance of cavitation within the vortex core. It is only below a certain cavitation number that the vortex cross section turns into an ellipse, which is associated with an abrupt increase in the pressure fluctuations with a distinct peak in the frequency domain. A further decrease in the cavitation number results in a constant decrease in the activated frequency while the amplitude of these oscillations experience a rise followed by a quick drop. Phase-averaged velocity fields show that the occurrence and development of cavitation within the vortex rope result in a more diffused distribution of the angular momentum. The instantaneous velocity fields, on the other hand, reveal that the elliptical vortex has various states with either diffused or concentrated velocity distributions, which makes the use of the averaged velocity field for this point less relevant.
Mitigation of Draft Tube Pressure Pulsations by Radial Protrusion of Solid Bodies into the Flow Field: An Experimental Investigation
Authors: Shiraghaee Shahab , Sundström Joel , Raisee Mehrdad , Cervantes Michel J.
Published: June 2021

An experimental investigation of frequential protrusion of four solid rods into the draft tube of a propeller turbine operating under partial discharge has been undertaken. The effectiveness of mitigating the pressure fluctuations associated with the rotating vortex rope (RVR) has been quantified using pressure measurements on the wall of the draft tube cone. Three azimuthal configurations of the phase difference between the rods, and four protrusion lengths were investigated. It is shown that the rotating component of the RVR decreases, irrespective of the azimuthal configuration and protrusion length, with imposed phase differences in the same direction as the runner rotation being the most effective, reducing the amplitude of the rotating component by a maximum of 62%. However, for each azimuthal configuration, the plunging mode of the RVR is amplified for large protrusion lengths, with the smallest amplification occurring for the case of 180 degrees phase difference between protrusions. Therefore, to quantify the most efficient configuration in mitigating the harmful effects of the RVR, an overall assessment of its effects on the entire turbine must be made before a conclusion can be drawn.
Volute throat area and wall modelling influence on the numerical performances of a very low specific speed pump
Authors: Chabannes Lilian , Štefan David , Rudolf Pavel
Published: June 2021

Low specific speed pumps find applications in a broad range of domains, but suffer from a low efficiency and a risk of head instability close to shut-off. The numerical computations on these pumps performed in the last years have shown discrepancies with experimental results. Recent studies suggest that the use of wall-functions underpredicts the losses of these pumps, especially at overload. The reason has been attributed to a detachment zone downstream the volute tongue, not well captured with the wall-function approach. This paper focuses on the influence of the volute casing on a pump with a specific speed of 8.9 on two issues. First, the influence of the wall modelling approach relatively to the low-Reynolds number method on the performance prediction is discussed. The results are, as expected, an underprediction of the losses when the wall-function approach is used. With a larger volute, the difference between the two wall modeling approaches is smaller. Secondly, the influence of the volute throat area enlargement on the pump performances is discussed. Both the head and efficiency are improved at the design point and at overload with an increased volute throat area. However the part-load head decreases and the head flattens. The study of the flow at part-load, in the region at the outlet of the impeller reveals that with a larger volute, larger flow exchanges are present, contributing to additional mixing losses and head loss.
Developments in multiple-valve water-hammer control
Authors: Bergant A , Hässig S , Karadžić U , Urbanowicz K , Tijsseling A
Published: June 2021

This paper investigates multiple-valve closures in a simple reservoir-valve-pipeline-valve system. Multiple closing (or opening) of valves may induce large positive or low negative pressure waves due to wave interference (superposition of the waves). The effect of multiple-valve closure can be either beneficial or detrimental, with the outcome being entirely dependent on the position of the valves and the sequence and delay of the closures. Valves are incorporated as boundary conditions in the method of characteristics model. The staggered (diamond) grid with consideration of unsteady skin friction is applied. Experimental investigations of multiple-valve induced water-hammer have been performed in the University of Montenegro laboratory pipeline apparatus. The apparatus consists of an upstream end high-pressurized tank, horizontal steel pipeline (length 55.37 m, inner diameter 18 mm), four valve units positioned along the pipeline including the end points, and a downstream end tank. The transient event is initiated first by rapid closure of the downstream-end valve followed by the delayed closure of the upstream-end valve. Calculated and measured results are compared and discussed in the light of the effects of pressure wave interference.
Monitoring 4.0 of penstocks: digital twin for fatigue assessment
Authors: Dreyer M , Nicolet C , Gaspoz A , Gonçalves N , Rey-Mermet S , Boulicaut B
Published: June 2021

In Europe, the ambitious goal of targeting at least 64% of electricity production from renewables by 2050 requires some significant increase of power network ancillary services. A general extension of primary/secondary reserves is necessary to cope with the increasing penetration of stochastic renewable energies and maintain the grid vulnerability at acceptable levels. In this context, hydropower plants are called upon to play a major role due to their operational flexibility and ability to provide ancillary services. However, the provision of these services is not without consequences for the plant, as the increase of load variations and start/stop sequences enhances fatigue problems by soliciting the penstocks faster than originally expected. Given that the fatigue wear rate can be 10x higher when ancillary services are active, it is crucial to ensure the fitness-for-service of the penstocks by proper monitoring. Nevertheless, the number of sensors along the hydraulic circuit is often very limited, so that periodic stops of the plant and inspections are necessary to assess the health of the pipes. In this paper, we present how a digital twin of the power plant, namely the Hydro-Clone system, can be used to fill this gap by enabling real-time knowledge of the transient pressures throughout the water conduits. These pressures are correlated to the stress variations using either analytical formula or finite element modelling (FEM), depending on the geometry and embedding conditions of each penstock element. The validity of this approach is demonstrated by comparing the predicted stresses with measured values in the penstock of the 200 MW La Bâtiaz hydropower plant, owned by Electricité d’Emosson SA. To this end, strain gages are mounted at the bottom and top of the penstock, in front of the manifold and on the penstock protection valve. The appropriate conversion of pressure to stress at the strain gage location is derived through the analysis of FEM simulations. This work shows the benefits of using a digital twin for fatigue assessment and paves the way for real-time penstocks fatigue monitoring.
Influence of turbulent inlet conditions on the flow inside a bulb turbine draft tube using Large-Eddy Simulations
Authors: Véras P , Balarac G , Métais O , Georges D , Bombenger A , Ségoufin C
Published: June 2021

The head losses inside the draft tube of a bulb turbine can represent an important portion of the total energy losses due to the low heads at which these machines operate. However, the complexity of the flow makes it a numerical challenge to simulate. Previous studies have shown that Large Eddy Simulations (LES) based on mean inlet conditions improve flow prediction inside the draft tube’s cone but diverge further downstream [4]. Moreover, uncertainties and the lack of detailed experimental data at the inlet have been identified as the main reason for these discrepancies and precise measurements close to the walls are necessary to correctly validate the numerical simulations [8, 4]. Thanks to detailed experimental measurements, the objective of this paper is to enhance the accuracy of previous results by performing LES computations to numerically simulate the flow inside the draft tube of a bulb turbine, and to investigate the influence of inlet conditions using an innovative approach. A two-criteria based mesh adaptation [14] along with an element-wise masking strategy is used to assure a good spatial discretization level while reducing the computational cost. Partial experimental data imposed at the inlet are often not sufficient to achieve a proper downstream flow prediction with a LES. The real challenge thus consists in the economical generation of proper mean and fluctuating inlet flow fields. We first show that a simple homogeneous and isotropic synthetic turbulence field added to the mean experimental profiles may improve the prediction of the downstream flow, but this is only achieved through empirical adjustments. Therefore, we also investigate the use of machine learning procedure to automatically generate proper inlet mean and fluctuating fields.
Francis 99 CFD through RapidCFD accelerated GPU code
Authors: Molinero D , Galván S , Domínguez F. , Ibarra L , Solorio G
Published: June 2021

Francis turbines research and development (R&D) requires performance assessment through hydraulic laboratory model testing which can be assisted by auxiliary tools like computational fluid dynamics (CFD), widely used recently. CFD has a history of seeking and requiring ever higher computational performance (HPC) because of the parallelism where Graphics Processor Units (GPUs) have emerged as a major paradigm for solving complex computational problems. However, their implementation to CFD solvers is still a challenge and the tremendous computational power of the GPUs has been wasted. This work presents how the open source RapidCFD code, based on OpenFOAM and ported to Nvidia CUDA, enabled GPUs to be able of running almost entire simulations in thousands of parallel stream cores packed in small form factor hardware in order to solve the incompressible Reynolds-Average-Navier-Stokes (RANS) equations. The simulations were based on a full 3D Francis turbine case which consisted of a grid domain of 23 million cells, including spiral case with stay vanes, distributor, runner and draft tube. CFD results of shaft torque, static pressure and velocity components in steady state deploying a multiple reference frame (MRF) motion approach were compared with available experimental data for main operation conditions at different distributor opening angles: best efficiency operation point (BEP), part load operation point (PL) and full load operation point (HL). The obtained data showed that by transferring directly all the computations to the GPUs, it is possible to make CFD simulations faster compared with central processing units (CPUs). Thus, it is expected to obtain an affordable low computational cost in optimization processes or full range performance evaluations.
Investigation of sediment erosion phenomenon for different blade angle distribution in Francis runner
Authors: Acharya N , Trivedi C , Gautam S , Dahlhaug O G
Published: June 2021

Wear and tear of hydraulic turbine due to sediment erosion is one of the major problems in hydropower plants located in the Himalayan and Andes regions. High sediment concentration in water of such areas wears down the mechanical components rapidly which causes significant operational challenges. In the present work, a prototype high head Francis runner with speed number 0.32 has been considered as reference case and other designs have been obtained modifying the blade angle distribution with same hydraulic parameters. Full turbine steady state numerical calculations were carried out at the best efficiency point and corresponding performance and erosion pattern are observed. Hydraulic efficiency and sediment erosion rate density are compared for the different cases taken into consideration. Sediment erosion analysis gives an indication of relative erosion intensity and critical zones of erosion damage in runner. Erosion was observed at the inlet near hub and shroud region and was mostly concentrated at the outlet of runner blades for all cases, where relative velocity is higher. Numerical results from CFD are also compared with the actual eroded turbine from the powerplant.
3D numerical investigations of the swirling flow in a straight diffuser for the variable speed values of the rotor obtained with a magneto-rheological brake
Authors: Szakal RA , Muntean S , Bosioc AI , Susan-Resiga R , Vékás L
Published: June 2021

The self-induced instabilities developed in decelerated swirling flows lead to pressure fluctuations. The swirling flows generated under variable speeds of the rotor of a swirl generator using a magneto-rheological brake are numerically and experimentally investigated. Three-dimensional turbulent flow computation is performed for several rotor speeds. Two mean velocity components numerically computed are validated against LDV data on a survey axis located downstream to the rotor for two speed values. The torque on the rotor blade is examined for several speeds. The numerical results are checked against the design values to identify the benefits and limitations of the concepts applied to the design stage. The flux of moment of momentum is modified when the rotor speed is slow down. The circulation, the total pressure and the swirl free velocity are examined on a cross section located downstream to the rotor for all investigated speeds. As a result, the changes of the hydrodynamic flow field are quantified. The unsteady pressure measured on the cone wall at four levels is acquired. The Fourier spectra associated with different self-induced instabilities developed in the cone are examined revealing the distribution of both plunging and rotating components. A low frequency plunging component in a straight diffuser is determined on a speed range of the rotor.
Numerical study of flow behavior in a cavitation tunnel using RANS with Scale-Adaptive Simulation (SAS) turbulence model in an OpenFOAM framework
Authors: Hidalgo V , Suárez G , Erazo J , Puga D , Márquez D , Benavides I , Cando E , Valencia E , Luo X
Published: June 2021

The present paper focuses on the study of flow through a cavitation Venturi tunnel. Motivated by the results obtained in the studies of “Simultaneous observation of cavitation structures and cavitation erosion” and “Combined numerical and experimental investigation of the cavitation erosion process” by Dular et al. A structured mesh based on previous studies has been generated using the free software GMSH. The numerical study was performed using the Navier-Stokes equations with RANS approximation. For that, the k − ω − SST SAS turbulence model and the implemented Zwart-Gerber-Belamri have been applied in OpenFOAM. The results show that the phenomena in a vapor volume fraction where the formation, growth, detachment and collapse of the cavitation cloud can be appreciated. These results agree with the aforementioned studies. Furthermore, the results show the peak pressure formation corresponding to the detachment and collapse of the cloud during the cavitation cycle, which is the main reason for erosion. It is concluded that the model satisfactorily predicts the phenomena behavior on a Δt = 9 × 10−6[s] being suitable to capture adverse pressure gradients.
Water flows generating hysteresis on the S-shape
Authors: Nichele S , Bayle S , Vaillant Y , Janson E , Guillaume R , Houdeline JB
Published: June 2021

For a given hydraulic design and a given guide vane opening, pump-turbine S-shape description in the turbine quadrant can be different depending on whether measurements are performed from the high discharge to the low discharge area or vice versa. A specific device for visualizing the flow field inside the runner has been developed in a scaled model of a medium head pump turbine machine in order to analyze and understand this hysteresis phenomenon. Windows, lights, high-resolution cameras and tracers have been combined to visualize the flow field. Flow field behavior has been studied in the runner and in the vaneless area located between the guide vanes and the runner. Two different methods of analyzing the flow field in the runner have been tested. Depending on the localization of the operating points and the direction of the S-shape description, different flow structures have been directly observed. In parallel, a study of the impact of this hysteresis on transient behavior in turbine mode has been carried out. Understanding this phenomenon is important to improve future design and to accurately measure the S-shape during model tests.
Selection and Optimization of Sensors for Monitoring of Francis Turbines
Authors: Valentín David , Presas Alexandre , Valero Carme , Egusquiza Mònica , Egusquiza Eduard
Published: June 2021

With the current demand of flexibility to hydraulic turbines, these are working under off-design conditions more than ever. Under these conditions different complex hydraulic phenomena appear, especially in Francis turbines, affecting the machine stability as well as reducing the useful life of its components. Hence, it is desirable to detect in real-time these hydraulic phenomena to assess the operation of the machine. In addition, the position and type of sensor to detect these phenomena is a key point for the monitoring of Francis units. In this paper, a large medium-head Francis turbine was instrumented with several sensors such as accelerometers, proximity probes, strain gauges, pressure sensors and a microphone. Results obtained with the different sensors in different locations are compared to know which hydraulic phenomenon is detected with every sensor. Furthermore, different signal analysis techniques are also compared. With this information, monitoring systems can be optimized with the most convenient sensors, locations and signal analysis techniques, reducing its difficulty to install and economic cost.
Analysis of hydro-abrasive erosion and efficiency changes measured on the coated Pelton turbines of HPP Fieschertal
Authors: Abgottspon A , von Burg M , Staubli T , Felix D
Published: June 2021

Geometrical changes and material loss of Pelton turbine runners as well as changes in turbine efficiency have been measured at HPP Fieschertal in Valais, Switzerland since 2012. The HPP is equipped with two horizontal axis Pelton units, with each 32 MW nominal power, 7.5 m3/s design discharge, 515 m head and two injectors. The nozzles and the buckets are hard-coated. Due to the relatively high hydro-abrasive erosion during the summer (sediment transport season), the splitters and cut-outs of the runner buckets are grinded and re-coated on-site usually every winter.

Turbine erosion was quantified based on repeated measurements on two runner buckets using 3d-scanning and a coating thickness meter. The detailed geometrical models showed amongst others that the splitter width distributions are similar for buckets of one runner, but differ considerably between runners. Changes in turbine efficiency were measured by the sliding needle procedure and continuously monitored based on operating data. From the efficiency monitoring over eight years of both turbines, efficiency differences were evaluated for each sediment season and for various refurbishment or replacement actions. The mean efficiency reduction was 0.4 % per sediment season. The on-site refurbishment works partly compensate the efficiency reductions due to erosion, leading to an efficiency drop of e.g. 2 % over six years, after which the runners are usually overhauled in the factory.
Fully automated multidisciplinary design optimization of a variable speed turbine
Authors: Tengs Erik , Charrassier Flora , Jordal Maria Rolstad , Iliev Igor
Published: June 2021

The future electricity market will have large contributions from renewable energy sources such as solar and wind. The intermittent nature of these energy sources creates a need for highly flexible operation of hydropower stations and changes the way we use hydraulic turbines to more off-design operation and more start-stop cycles. These changes challenge the structural integrity of the turbines in a way not seen before, and the next generation of hydro turbines will therefore have to be designed differently to meet this challenge. The goal of this article is to develop a framework for variable-speed Francis turbine design.

A fully automated multi-disciplinary design optimization procedure has been developed. As off-design operation is assumed, the runner do not only have to be optimized from a hydraulic point of view, the structural integrity is equally important. The design optimization is therefore based on a blending function of the hydraulic efficiency and the harmonic stress levels at a series of operating conditions. This is to ensure that the turbine is less prone to fatigue, even at off-design operation.

The process is fully automated, with no need for human interaction. A MATLAB design code is producing the raw design, every design is then meshed and tested at different operating points in a CFD solver. The pressure field from the fluid analysis is mapped onto the structure and evaluated in an acoustic-harmonic analysis to assess the fluctuating stresses in the turbine blades. A global optimization loop consisting of 15 design parameters is driving the process based on an overall optimization function.

The work has been performed as part of the HydroFlex project, and has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 764011.
Influence of flow patterns on the performance of straight-through labyrinth seals. Numerical study and validation against experimental data
Authors: Rocca A , Troyer S , Casetta A
Published: June 2021

When numerically simulating the performance of a complete Francis turbine, it is common practice to omit the seals to save computing power. Volumetric and friction losses are usually taken into account using empirical values. There is abundant literature on the topic, but all analytic formulations rely on widely variable empirical coefficients. To overcome the uncertainty in determining volumetric losses, a detailed analysis of the sealing is necessary. Focusing on straight seals and configurations with cavities, in-house experimental data and numerical simulations have been used to show that few geometric parameters play a fundamental role in defining the flow patterns inside the clearance and even more so inside and between cavities. As is to be expected, the seals effectiveness is heavily influenced by these flow structures. It is also shown that certain methods of dealing with near-wall flow structures are better suited than others for the estimation of the discharge behaviour when compared to experimental results. Even though in the framework of the RANS equations CFD has proven to be a reliable tool for a wide range of geometries, further investigations are necessary on deep cavities. For aspect ratios above 0.75, the flow patterns inside the cavity change drastically, leading to bad convergence rates of the solver and, more important, to a considerable misalignment between numerical and experimental results. Lid-driven cavity flow is known to be a complex problem in 2D domain, and in this case, the flow becomes three-dimensional due to the tangential velocity induced by rotation. However, the reasons behind the problems in CFD analysis are not entirely clear. Given the observed variations of the flow structures inside sealings with different geometric parameters, it becomes clear why a simplified, generic formulation is very difficult to obtain, if not by adopting empirically defined coefficients which are needed to tune the analytical model.
Numerical simulations of Pelton turbine flow to predict large head variation influence
Authors: Alimirzazadeh S , Decaix J , Avellan F , Crettenand S. , Münch-Alligné C.
Published: June 2021

In the framework of the new feed-in-tariff system in Switzerland 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 small hydropower plant of Gletsch-Oberwald (KWGO) owned by FMV and commissioned end of 2017. This run-of-river power plant is equipped with two six-jet Pelton turbine units featuring a maximum power of 7 MW each.

The addition of flexibility can be reached by using existing volumes of the power plant: the settling basin, the forebay chamber as well as part of the headrace tunnel. By consequence, the turbine head will undergo variations. To ensure that these variations will not cause any damages to the Pelton runner, the influence of the available head is investigated by numerical simulations. The simulations are carried out using two different software. OpenFOAM, which is based on a Finite Volume Method (FVM), is used for computing the flow inside the distributor until the jet. GPU-SPHEROS, which is based on Arbitrary Lagrangian-Eulerian (ALE) Finite Volume Particle Method (FVPM) is utilized to compute the interaction between the jet and Pelton buckets.

Mixing the two aforementioned approaches, i.e. mesh-based FVM and particle-based FVPM, the overall torque T of the present six-jet Pelton runner can be reconstructed for different rated heads and discharges. The predicted torque fluctuations can then be considered for an estimation of the structural fatigue damage of the runner.
Application of particle-based numerical analysis to the practical design of Pelton turbine
Authors: Kumashiro Takashi , Alimirzazadeh Siamak , Avellan François , Tani Kiyohito
Published: June 2021

For the design optimization of the Pelton turbine, it is highly demanded to investigate the flow inside the turbine casing, which includes the water jet from the nozzles, the interaction between the jet and rotating runner, and the flow ejected from the bucket outlet, in various operating ranges. The behavior of the flow, however, is very complicated due to its unsteadiness and free surface. Further, the experimental observation in the model test is challenging because of the high time resolution requirement and the obstruction by the splashing water inside the turbine housing. In this regard, the numerical analysis is considered as a powerful method to approach the flow behavior in the Pelton turbine. Conventionally, the grid-based numerical analysis is applied to the calculation of the flow for its practical design. However, with the gird-based methods, a huge amount of fine elements is required to capture the unsteady behavior of the water free surface and the tiny splashing water particles. Increasing the number of elements directly results in higher computational costs, which makes it difficult to consider the splashing water in the process of practical design. From this point of view, the GPU-accelerated finite volume particle method is applied to the investigation of the flow in this research. It is firstly confirmed that the particle-based numerical result has a good agreement with the experimental result by the comparison of the turbine characteristics. Furthermore, several evaluations of the flow based on the analysis for the practical design are introduced in the paper.
Research of Turbine Efficiency Test by Current-Meter Method in Circular Pipe
Authors: Zhou Ye , Cao D F , Ge X F , Tan L J
Published: June 2021

For absolute discharge and efficiency measurement of turbine with medium and low water head, the current-meter method has high precision, good reliability, and wide application range. For rectangle flow channel, it is easy to lift down a gate frame with current meters to measure the flow velocity, but for circular pipe, due to the high stress, possible deformation, and strict safety requirement, the design, installation, and implementation of the support bracket is the key to the measurement by current-meter method. In this paper, we made the research of key technology for current-meter method in circular pipe. By building a numerical model for circular pressure pipe and flow measuring bracket, we analysed the influence of meters arrangement, the force and deformation of support pole with CFD, and fluid-solid coupling method, Finally, an optimized reinforcement bracket is proposed, with combined smooth and stress calculation, the measuring bracket is verified it can withstand the flow stress and has good safety characteristics, which can provide a reference for other similar turbine efficiency tests.