bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of the helical groove start angle on the flow drag and noise of a cylinder
Authors: Xu Mingyang , Hu Wulong , Yang Yi
Published: December 2024

The helical groove structure has emerged as a promising passive control technology for drag and noise reduction, with the potential to optimize the operational efficiency of underwater equipment and reduce energy consumption. This paper employs a hybrid numerical simulation method that combines the large eddy simulation method and Lighthill's acoustic analogy to investigate the effects of different helical groove starting angles on the drag and noise of a cylindrical flow at Reynolds numbers of 15 000, 45 000, 75 000, and 105 000. The results indicate that increasing the start angle of a helical groove promotes vortex expansion and accelerates the fluid transition to the turbulent state, achieving a maximum drag reduction of ∼30% and noise reduction of about 6 dB.
Turbulence distortion and leading-edge noise
Authors: Piccolo A. , Zamponi R. , Avallone F. , Ragni D.
Published: December 2024

The distortion of turbulence interacting with thick airfoils is analyzed with scale-resolved numerical simulations to elucidate its impact on leading-edge-noise generation and prediction. The effect of the leading-edge geometry is investigated by considering two airfoils with different leading-edge radii subjected to grid-generated turbulence. The velocity field is shown to be altered near the stagnation point, in a region whose extension does not depend on the leading-edge radius. Here, the deformation of large-scale turbulence causes the amplitude of the upwash velocity fluctuations to increase in the low-frequency range of the spectrum because of the blockage exerted by the surface. Conversely, the distortion of small-scale structures leads to an exponential decay of the spectrum at high frequencies due to the alteration of the vorticity field. The prevalence of a distortion mechanism over the other is found to depend on the size of the turbulent structures with respect to the curvilinear length from the stagnation point to the location where surface-pressure fluctuations and pressure gradient peak. This occurs at the curvilinear abscissa where the curvature changes the most. The same high-frequency exponential-decay slope observed for the upwash velocity is retrieved for surface-pressure spectra in the leading-edge region, suggesting that the airfoil unsteady response is induced by the distorted velocity field. This physical mechanism can be accounted for in Amiet's model by using a distorted turbulence spectrum as input and accounting for the increased amplitude of the distorted gust in the aeroacoustic transfer function, retrieving an accurate noise prediction for both airfoils.
Computational modeling of hydrogen behavior and thermo-pressure dynamics for safety assessment in nuclear power plants
Authors: Amponsah Joseph , Adorkor Emmanuel , Opoku David Ohene Adjei , Apatika Anthony Ayine , Kwofie Vincent Nyanzu
Published: December 2024

Following the Three Mile Island Nuclear Generating Station incident 1979, extensive research has focused on preventing hydrogen accumulation and explosions during nuclear power plant emergencies. We used advanced computational fluid dynamics (CFD) simulations to analyze hydrogen distribution, pressure dynamics, and the efficacy of safety measures across various containment structures under accident scenarios. Results indicate that smaller containment structures experience rapid hydrogen accumulation, reaching a peak pressure of 2.5 bars and a temperature of 120 °C within the first 30 s. Structural integrity is compromised at pressures around 3.8 bars, leading to failure within 10 min under sustained high pressure. In contrast, larger containment structures exhibit delayed pressure buildup, peaking at 2.3 bars with a corresponding temperature of 110 °C, and maintain integrity for up to 30 min. Fire scenarios demonstrate that smaller containment structures reach peak temperatures of 500 °C, which resulted in partial structural failure, whereas larger containments withstand up to 450 °C for 40 min without compromise. When hydrogen concentrations exceed 35%, and temperatures surpass 1430 °C, explosion risks increase substantially, which reduces the effectiveness of passive mitigation systems.
Impact of impeller wake on the energy fluctuation characteristics of centrifugal pumps under rotating stall condition
Authors: Gou Qiuqin , Song Dongmei , Wu Haokun , Wen Shiqi , Cai Mengjun
Published: December 2024

To reveal the impact of impeller wake flow on the internal energy fluctuation of centrifugal pump, in this study, the performance and internal flow structures of centrifugal pumps under various operating conditions have been thoroughly analyzed by combining numerical simulations with experimental validation. The results indicate that the numerical simulation results are highly consistent with the experimental data in terms of head and efficiency, with an error of less than 5%, demonstrating the high accuracy of the simulations. Further investigation reveals a significant increase in entropy production loss under critical and deep stall conditions, primarily concentrated in the blade wake flow and the volute tongue interference region. Analysis of entropy production maps and pressure fluctuations under different operating conditions shows that the breakup of blade wake vortices and their interaction with the tongue are the main causes of high entropy production values. Coherence studies of pressure and entropy production fluctuations in the low-frequency range indicate a bidirectional interference mechanism between the two. Overall, this study provides important theoretical and data support for understanding the performance and loss mechanisms of centrifugal pumps under complex flow conditions.
Ultra-high carrier mobility and ultra-low lattice thermal conductivity in PdSSe monolayers with fully Stone–Wales defects
Authors: Peng Ke , Xiao Feng , Chen Bowen , Lei Wen , Ming Xing
Published: December 2024

The Stone–Wales (SW) defects have a critical impact on the physical properties of the carbon-based materials with pentagonal and hexagonal rings, which also emerge in other pentagon-based materials with the Cairo tessellation. However, scarce attention has been paid to SW defect engineering in two-dimensional (2D) pentagonal materials. In the present letter, we propose four unreported 2D PdSSe monolayers (designated as SW1–SW4) by introducing SW defects into the penta-PdSSe monolayer. The electronic structure, optical, electrical transport, and thermal transport properties of these SW defect structures have been systematically investigated based on first-principles calculations. SW1–SW4 retain the square-planar coordination as presented in the pristine penta-PdSSe, exhibiting excellent dynamical, thermal, and mechanical stability. Particularly, SW1 and SW2 exhibit direct bandgaps, which are more favorable for electronic transitions. The suitable band alignments meet the requirement of photocatalytic water splitting. Furthermore, the defect structures show high visible-light absorption coefficients (∼105 cm−1) and ultra-high carrier mobility (∼103 cm2V−1s−1). More excitingly, these defect structures display ultra-low anisotropic lattice thermal conductivities (lower than 2 Wm−1K−1 at room temperature). The suitable bandgap values, appropriate band edge positions, good optical absorption performances, and ultra-high carrier mobility concomitant with ultra-low lattice thermal conductivity render these PdSSe monolayers with SW defect structures as promising semiconductor materials for potential applications in nanoelectronics, optoelectronics, solar cell, photocatalyst, and thermoelectric energy conversions.
A mining code for regulating lunar water ice mining activities
Authors: Hubbard Kevin M. , Elkins-Tanton Linda T. , Masson-Zwaan Tanja
Published: December 2024

Despite the increasing number of space launches, growth of the commercial space sector, signing of the Artemis Accords, maturation of space mining technologies, the emergence of a regulatory environment through domestic legislation, and a comprehensive body of international law, an intergovernmental governing authority has yet to be established to manage mining activities on the Moon. We developed a Lunar Mining Code and mapping tool to regulate and manage prospecting and exploration activities for water ice at the Moon’s poles. The Lunar Mining Code is composed of a notification system to manage prospecting, a contract system for issuing exploration licenses to allotted areas on the Moon, and best mining practices and principles to promote equal access and safeguard the lunar environment.
Accelerated cell-type-specific regulatory evolution of the human brain
Authors: Joshy Dennis , Santpere Gabriel , Yi Soojin V.
Published: December 2024

The molecular basis of human brain evolution is a key piece in understanding the evolution of human-specific cognitive and behavioral traits. Comparative studies have suggested that human brain evolution was accompanied by accelerated changes of gene expression (referred to as “regulatory evolution”), especially those leading to an increase of gene products involved in energy production and metabolism. However, the signals of accelerated regulatory evolution were not always consistent across studies. One confounding factor is the diversity of distinctive cell types in the human brain. Here, we leveraged single-cell human and nonhuman primate transcriptomic data to investigate regulatory evolution at cell-type resolution. We relied on six well-established major cell types: excitatory and inhibitory neurons, astrocytes, microglia, oligodendrocytes, and oligodendrocyte precursor cells. We found pervasive signatures of accelerated regulatory evolution in the human brains compared to the chimpanzee brains in the major six cell types, as well as across multiple neuronal subtypes. Moreover, regulatory evolution is highly cell type specific rather than shared between cell types and strongly associated with cellular-level epigenomic features. Evolutionarily differentially expressed genes (DEGs) exhibit greater cell-type specificity than other genes, suggesting their role in the functional specialization of individual cell types in the human brain. As we continue to unfold the cellular complexity of the brain, the actual scope of DEGs in the human brain appears to be much broader than previously estimated. Our study supports the acceleration of cell-type-specific functional programs as an important feature of human brain evolution.
Recognizability and timing of infant vocalizations relate to fluctuations in heart rate
Authors: Borjon Jeremy I. , Sahoo Manash K. , Rhodes Katherine D. , Lipschutz Rebecca , Bick Johanna R.
Published: December 2024

For human infants, producing recognizable speech is more than a cognitive process. It is a motor skill that requires infants to learn to coordinate multiple muscles of varying functions across their body. This coordination is directly linked to ongoing fluctuations in heart rate; a physiological process that can scaffold behavior. We investigated whether ongoing fluctuations in heart rate coincide with vocal production and word formation in 24-mo-old infants. Infants were most likely to produce a vocalization when heart rate fluctuations reached a peak (local maximum) or trough (local minimum). Vocalizations produced at the peak were longer than expected by chance. Functionally, vocalizations produced just before the trough, while heart rate is decelerating, were more likely to be recognized as a word by naive listeners. Thus, for the developing infant, heart rate fluctuations align with the timing of vocal productions and are associated with their duration and the likelihood of producing recognizable speech. Our results have broad and immediate implications for understanding normative language development, the evolutionary basis and physiological process of vocal production, and potential early indicators of speech and communication disorders.
Unsettling vulnerability in the wake of violence
Authors: Volvach Natalia
Published: December 2024

In this essay, I write about the multifaceted dimensions and reverberations of violence (Navaro et al., 2021b) of Russia’s war against Ukraine, spanning from 2014 to the present day. Drawing on
previous studies of semiotic landscapes, which emphasize a relational approach to people and places (Peck et al., 2019), I analyze ethnographic materials in the form of field notes collected during research
in Crimea in 2019. This is done to reflect on the character of the violence to which people and landscapes become exposed. Three
analytical vignettes describe the remnants of violence, which take on various guises of Russia’s war
and highlight the vulnerability of both people and landscapes. At the end of the essay, I propose approaching these processes
poetically, and viewing them through the lens of mutual vulnerability — a concept that considers the
relationality of vulnerability as a phenomenon, encompassing the vulnerability of both people and landscapes.
Intralingual and interlingual effects in a pure language list
Authors: Broekhuis Lisan , Bernolet Sarah , Sandra Dominiek
Published: December 2024

In various English lexical decision tasks (LDTs), bi-/multilinguals have evinced shorter response times (RTs) for
cognates (i.e., words with the same meaning in two languages, e.g., the Dutch-English water) and longer RTs for
interlingual homographs (IHs; words with distinct meanings in two languages, e.g., the Dutch-English map)
compared to monolingual controls (e.g., Biloushchenko, 2017). This suggests that
multilinguals automatically activate lexical representations from multiple languages (Dijkstra
et al., 1998). To further investigate language (non-)selectivity, in our English LDTs, we compare the processing of
cognates and IHs to intralingual words that are similar but only exist in English (i.e., cognates to metonyms like
chicken, which can refer to the animal and the closely-related sense “chicken meat”, and IHs to homonyms like
bat, which has two meanings: “baseball bat” and “nocturnal flying animal”). Half of our cognates and IHs only
exist in our native Dutch participants’ non-native languages (English-French) to avoid any potentially confounding effects of the
supposed “special status” (Midgley et al., 2011) of L1. Significant inhibition was
found for homonyms and significant facilitation for metonyms and native (Dutch-English) cognates but not for non-native
(English-French) cognates. These results are discussed in relation to the language non-selective hypothesis (Dijkstra et al., 1998).
Talking it through with teachers
Authors: Gorp Koen Van , Branden Kris Van den , Newton Jonathan , Coss Matthew D.
Published: December 2024

This interview with Jonathan Newton explores key issues in task-based language teaching (TBLT), focusing on the relationship between TBLT and textbooks, and the potential for TBLT teacher development building on existing practices and materials. Newton challenges the wholesale rejection of textbooks in TBLT, arguing for “taskification” of existing materials as a pragmatic approach for teachers. He discusses the utility and limitations of task criteria (Meaning, Gap, Own Resources, Outcome — “MGOO”) as a heuristic for teachers, emphasizing the need for clearer conceptualization and application across different task types. The interview highlights the importance of building on teachers’ existing practices when introducing TBLT principles, rather than approaching TBLT from a highly theoretical angle. Newton reflects on TBLT implementation in Asian contexts, noting the diversity of educational settings and the potential of TBLT to enhance student motivation and agency. The interview underscores the value of teacher-researcher collaboration in developing practical, context-appropriate TBLT approaches.
A journey of sustainable TBLT curricular development
Authors: Kim YouJin
Published: December 2024

Task-based Language Teaching (TBLT), introduced in the early
1980s, has significantly matured through the integration of theories and
research from instructed second language acquisition (ISLA) and educational
practice, effectively addressing the growing need for efficient programs.
Although many initial criticisms have been treated as non-issues using evidence
from empirical research (Ellis, 2017;
Long, 2016), program-wide
adoption of TBLT is less widespread than might have been expected by now (Long & Ahmadian, 2022). The three
areas that I see as needing improvement are (1) long-term collaboration with
various stakeholders for different roles, (2) producing TBLT ambassadors through
teacher education, and (3) documenting TBLT programs in action. This paper
begins by reviewing different collaboration models for developing and
maintaining TBLT curricula and sharing sample TBLT programs in action. I then
present a sample case study demonstrating work with various stakeholders,
particularly focusing on novice teachers, and fostering TBLT ambassadors. The
paper concludes by suggesting six principles for developing and maintaining
sustainable TBLT curricula at the programmatic level.
Ultra-broadband non-degenerate guided-wave bi-photon source in the near and mid-infrared
Authors: Roeder F , Gnanavel A , Pollmann R , Brecht O , Stefszky M , Padberg L , Eigner C , Silberhorn C , Brecht B
Published: December 2024

The latest applications in ultrafast quantum metrology require bright, broadband bi-photon sources with one of the photons in the mid-infrared and the other in the visible to near infrared. However, existing sources based on bulk crystals are limited in brightness due to the short interaction length and only allow for limited dispersion engineering. Here, we present an integrated PDC source based on a Ti:LiNbO3 waveguide that generates broadband bi-photons with central wavelengths at

860

nm

and

2800

nm

. Their spectral bandwidth exceeds

25

THz

and is achieved by simultaneous matching of the group velocities (GVs) and cancellation of GV dispersion for the signal and idler field. We provide an intuitive understanding of the process by studying our source’s behavior at different temperatures and pump wavelengths, which agrees well with simulations.
Optimized energy storage configuration considering joint operation of multiple parks
Authors: Tan Liping , Zhang Wenyuan , He Jing , Chen Qing , Zhang Shijie , Huang Yicheng
Published: December 2024

The park’s growing reliance on photovoltaic and wind power faces challenges due to their intermittent and peak-opposite nature, causing a mismatch with load demand and highlighting the issue of energy consumption. This paper addresses this by proposing an optimized energy storage configuration method for multi-park joint operation, considering demand differences. It involves designing a joint operation mode with energy storage and an operation method for energy storage under joint demand. An optimization model is developed to minimize configuration costs while adhering to system and energy storage constraints. The paper’s method is validated through case studies.
Calculation of forces exerted on to the preformed helical fittings of transmission lines
Authors: Chen Keji , Sun Yongjun , Li Xinchun
Published: December 2024

The preformed fittings, as a crucial component of overhead lines, directly impact the safe and stable operation of the entire transmission line. In recent years, preformed fittings in ultra-high voltage transmission lines have frequently encountered issues such as strand separation, misalignment, and breakage, posing potential threats to the stability of the power grid. To comprehensively assess the performance of preformed fittings and enhance the accuracy of analysis, this paper first employs an explicit solution method for quasi-static analysis to thoroughly investigate the impact of different analysis time steps on system energy and solution outcomes. During this process, a monitoring mechanism for the ratio of kinetic energy to internal energy is specifically established to ensure the accuracy and reliability of the analysis results. Based on the aforementioned research, this paper further focuses on the contact pressure, deformation, and slippage between the preformed fittings and the conductors, conducting a detailed analysis. Through this study, it is expected to gain a deeper understanding of the mechanical behavior of preformed fittings during actual operation and provide a solid theoretical foundation for their optimized design.
Troubleshooting of wind turbine gearboxes
Authors: Shao Luchuan , Zhao Bing
Published: December 2024

Qinghai Province is rich in wind power resources, actively building wind power generation clean energy highland, large installed capacity, and in the rapid expansion, how to achieve the safe and stable operation of the wind power base is particularly critical. Wind turbine gearboxes operate 24 hours a day under poor working conditions, and key components are prone to failure, accounting for the highest proportion of maintenance costs, so it is of great significance to research intelligent assessment methods and key technologies for the health status of wind turbine gearboxes. A dynamic model of wind-machine-network coupling in wind turbine transmission chain is established to investigate the failure mechanism and dynamic evolution of transmission chain gearboxes under variable wind load. A time-frequency energy concentration algorithm based on a synchronous extraction operator is found to explore the mapping relationship between fault sources and signs. Using a multi-source signal fusion strategy and migration learning method for order spectral analysis, a system fault characteristic parameter identification model is established to implement online monitoring and fault prediction of the wind turbine operation condition, and to improve its operation reliability.
Application of RBF neural network PID control on buck DC-DC converter
Authors: Pan Ning , Wu Guitai , Li Renlong
Published: December 2024

A structure to solve low control accuracy and poor tracking performance in traditional PID controlled DC-DC converters when input voltages and load currents fluctuate has been proposed: combining PID control with Radial Basis Function (RBF) neural networks. To optimize the PID controller’s parameters, this approach makes use of the RBF neural network’s approximation capability for nonlinear functions. Under different test conditions, the neural network takes the output voltage and its deviation from the reference value as inputs. The hidden layer employs Gaussian activation and adjusts by gradient descent. The output layer computes the PID controller’s Proportional (Kp), Integral (Ki), and Derivative (Kd) by the linear combination of hidden layer node outputs. Simulation results using MATLAB/Simulink demonstrate that, under different test conditions, the system employing RBF neural network-PID control exhibits a smaller overshoot compared to traditional PID control systems. Furthermore, in steady-state circumstances, the settling time is shortened by around 1/2 and is decreased by roughly 1/4 in the presence of disturbance signals. These results unequivocally demonstrate that, in the presence of fluctuating test conditions, the new structure of this combination greatly improves the control precision and tracking performance of DC-DC converters.
The dynamic power sharing method for hydrogen-battery-supercapacitor hybrid energy storage system in DC microgrid
Authors: Zhou Shun , Zhang Xibeng , Luo Yupeng , Zhang Yanyu , Lu Yang
Published: December 2024

Recently, the electric-hydrogen hybrid system has gained widespread adoption as a means of enhancing the efficiency of photovoltaic power dissipation. However, optimizing power allocation among various energy storage systems presents a significant challenge. In this paper, we will propose an adaptive droop control strategy for Electric-Hydrogen Hybrid Energy Storage System (EHESS) within DC microgrids. This strategy takes into account the state of charge (SOC) of the battery and the state of hydrogen (SOH) within the hydrogen storage tank. Through simulation analysis, we will evaluate the efficacy of the method and demonstrate its effectiveness in facilitating collaborative power allocation within EHESS.
Optimized design and magneto-thermal coupling simulation analysis of automotive permanent magnet synchronous motor
Authors: Wu Zengyan , Li Shiliang , Bai Peng
Published: December 2024

This paper presents an optimized design for automotive permanent magnet synchronous motors (PMSM) focusing on expanding their operational speed range and improving efficiency. The issues of high losses and low efficiency in standard built-in fractional-slot PMSMs, which impact the stable operation of vehicle motors, are identified and addressed., Three innovative rotor magnetic circuit structures are proposed utilizing electromagnetic theory and finite element analysis. These designs are simulated and analyzed to reduce overall motor losses to 59% of the original levels and to ensure thermal characteristics meet the demands of wide-speed automotive motors. The study establishes a three-dimensional transient temperature field simulation model to predict temperature rise and distribution across motor components. The optimized rotor structures enhance performance and serve as a reference for future thermal design in PMSMs.
Study on interleaved parallel and secondary coupled switched inductance Boost converter
Authors: Lv Xiao
Published: December 2024

In recent years, with the worsening of environmental problems, photovoltaic power generation technology has become more and more widely used. In this paper, the output voltage level of a photovoltaic power generation system cannot meet the requirements of grid connection, and a scheme is proposed. An interleaved parallel and secondary coupled switching inductance Boost converter is proposed by combining secondary coupled switching inductance, coupling inductance, interleave-parallel technique, and capacitor-diode (CD) unit. The operating mode and steady-state performance are analyzed in detail, and the voltage gain and the voltage and current stress of each component are calculated. The model is built on the PSIM simulation platform, and the correctness of the theoretical analysis is verified by the simulation results. The results show that the voltage gain is improved effectively, and the voltage stress of each component is reduced, which accords with the theoretical analysis.
Study on the reliability verification method of electronic transformer under multi-physical field coupling effect
Authors: Qiu Keyue , Zhu Jianyang , Zhong Runfeng , Li Bowen , Feng Qihui , Wang Yu
Published: December 2024

With the development of smart grid technology, electronic transformers play an important role in substations, but their reliability is affected by a variety of environmental factors, such as temperature, humidity, and electromagnetic interference. Existing test standards fail to comprehensively simulate the operation of electronic transformers in real environments, resulting in their insufficient reliability. In this study, we propose a reliability verification method for electronic transformers that considers the effects of multiple physical fields, which mainly includes an electrical fast transient pulse group interference immunity test with temperature and humidity considerations, a conducted interference immunity test with radio frequency induction, and a surge interference immunity test. The test results show that the immunity of the collector is greatly affected when the electronic transformer is subjected to electromagnetic interference superimposed on temperature and humidity field changes and is prone to failure in extreme cases. This study provides a practical basis for the scenario application of electronic transformers.
Establishment method of IGBT thermal network model based on electrothermal coupling simulation and parameter identification
Authors: Wu Hao , Ying Zhanfeng , Chen Zhihua , Zu Wei
Published: December 2024

To swiftly and precisely assess the IGBT’s thermal safety during the circuit design phase, this paper proposes a method of establishing an IGBT thermal network model by electrothermal coupling simulation and parameter identification. This model integrates electrothermal coupling simulation techniques and parameter identification methods. Firstly, the IGBT’s finite element model is established by COMSOL, aiming to acquire the temperature distribution patterns of the IGBT and its heat sink under various operating conditions. Then, the objective function of parameter identification is constructed. The IGBT thermal network model’s parameters are extracted by combining the electrothermal coupling simulation results with the primal-dual interior point method. Then the device’s junction-ambient thermal network model is obtained. The proposed method’s efficacy is validated through the comparison of the results and calculation time of the thermal network model and the electrothermal coupling simulation.
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

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

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

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

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

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

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

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

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

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

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

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

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

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.