bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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

Abstract
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.