bluuebunny/crossref_metadata_2025_split huggingface dataset:
On the Water Jet Quality at Part-Load Operation of Pelton turbines
Authors: Semlitsch Bernhard 
Published: June 2024

Abstract
Pelton turbines with multiple nozzles are characterised by their excellent performance over a wide operating range of mass flow rates. Thus, Pelton turbine manifolds must also be designed to deliver good flow quality to the nozzles at part-load operating conditions to accomplish the expectations. A reduced number of nozzles are opened at low mass flow rate operating conditions, where the choice of the open nozzles depends on the water jet quality generated at the individual nozzles. We investigate the flow phenomena occurring in the manifold with the operation of a reduced nozzle number employing numerical simulations to analyse beneficial nozzle opening selections. The turbulent two-phase flow is predicted by the Volume-Of-Fluid (VOF) approach and the k–ω SST turbulence closure model. Different nozzle operating scenarios are simulated, and the implications on the water jet quality, i.e. deviation and shape deformation, are reported. The results show that the free water jet quality criteria can change drastically at individual nozzle operating conditions because of the velocity changes at the branch line junctions.
Comparisons of oxygen increment in a micropump considering the dissolved and released processes
Authors: Ren Z P , Li Z P , Li D Y , Wang H J , Liu J T , Li Y 
Published: June 2024

Abstract
Space micropump are an important component of the on-orbit refuelling system. The gas-liquid behaviour transition induced by dissolved and released processes in the micropump has obtained considerable attention. Our proposed mathematical model achieved the bidirectional dissolved-released processes in an on-orbit space micropump for the first time. The performance characteristics of the micropump and the mathematical computational model used by the plug-discharge flow have been validated. Herein, the correlated mechanism between the flow, mass transfer and solution status were analysed. Under the pressurization of the micropump impeller, the gas was constantly dissolved into the solution, and the higher concentration caused the gas to evolve from the solution. The oxygen increment decreased rapidly when the initial dissolved oxygen centration exceeded 23 mg/L because of the gas evolution occurred. Focused on this sudden decreasing state of oxygen increment from 23 to 24 mg/L, four concentration conditions were discussed in depth including flow field, oxygen increment and mass transfer rate. In the impeller, the equilibrium concentration increases controlled by the pressure was obviously larger than the increase of the real-time concentration; thus, the unidirectional absorbed processes occurred inside the impeller. Two near-rate mass-transfer band were found near the short blades, exhibiting the dynamic equilibrium characteristic. Moreover, affected by the strong disturbance of the impeller outlet, the mass transfer rate was the highest here.
Numerical analysis of the unsteady cavitation performance and structural characteristics of composite propeller
Authors: Dong L , Wu Q , Huang B , Wang G 
Published: June 2024

Abstract
The hydrodynamic performance of a composite propeller under cavitation conditions is analyzed considering the bidirectional transient fluid-structure coupling. The structure field and the flow field are calculated using ANSYS Mechanical/CFX and the information is transferred between them by the interface. It indicates the unsteady cavitating flow features in the presence of the wake condition manifest periodic tendencies. Additionally, the hydrodynamic coefficients of the composite propeller display a phase delay. The composite propeller demonstrates decreased volume of cavitation and enhanced efficiency. The bend-twist coupled deformation in the propeller mitigates the effects of cavitation loads on the performance.
Estimating Wear Rate of Guide Vanes in High-Head Francis Turbines through Flow-Through Testing and DPM Simulation
Authors: Zeng Yongzhong , Liu Xiaobing , Jia Lu , Lai Zhenming , Zhou Bo , Wang Xueren , Yao Yanhua , Yao Bing , Yu Zhishun , Wang Haiqi 
Published: June 2024

Abstract
The development of high-head water resources poses a significant concern due to hydro-abrasive erosion caused by entrained sediment particles. This issue is particularly prevalent in the muddy rivers of the Xinjiang region, China, where Francis turbines are commonly used. With increased soil erosion and rapid sediment transport, the erosion of Francis turbines, especially the guide vanes of high-head turbines, has become increasingly severe. The paper explores key factors that influence the erosion process caused by sediment-laden water. In addition to flow velocity and mud concentration, the properties of the sediment-laden water, such as hardness and size of sand particles, and the concentration ratio of sand particles with different hardness, also play a crucial role in the erosion process. The study is focused on analyzing the erosive effects of sediment-laden water on a high-head Francis turbine’s guide vane. The efficacy of the discrete phase model (DPM) as a simulation method for assessing wear on the guide vane is validated. This model helps analyze critical wear areas on the surface of the vane, enabling the identification of regions most severely affected by erosion due to sediment-laden water. By pinpointing these critical wear areas, the study provides valuable insights into the potential damage caused to the guide vane, thus contributing to better understanding and potential mitigation of erosion in similar turbine systems.
Investigation on the effect of different groove depth and width on the tip clearance leakage flow of hydrofoil
Authors: Dong Liu , Chenhao Li 
Published: June 2024

Abstract
Due to the complexity of axial-flow hydraulic machinery structure and the difficulty of flow field analysis, this paper takes three-dimensional hydrofoil as the research object to analyse the flow characteristics of clearance flow and carry out research on clearance leakage control. The 3-D hydrofoil model with two kinds of gap widths was calculated by using the numerical model method, and compared with the experiment; the influence law of different groove depth and width on the gap leakage flow characteristics and energy characteristics was studied. The results show that with the increase of groove depth, the clearance leakage increases, the lift-drag ratio decreases, and the pressure coefficient increases. Higher axial velocity is shown with increasing groove depth under the small tip clearance, while the opposite is true for large gaps. The optimal groove depth is determined to be D=1mm. When the groove width is 2mm, the pressure coefficient of the hydrofoil is the highest and the vorticity coefficient is the smallest, so the hydrofoil has better performance. In summary, when groove depth D=1mm and groove width W=2mm, the clearance leakage flow rate is smaller and the lift-drag ratio is higher. This study provides a new method for improving the flow field and running stability of turbine-machines with tip clearance in practical engineering.
FSI simulation of a high-head pump-turbine during load rejection process
Authors: Tang M J , Cheng Y G , Liu D M , Chen H Y , Liu K 
Published: June 2024

Abstract
High-head pump-turbine suffers large centrifugal and hydraulic forces due to large rotational speed and severe pressure pulsations during transient processes, and the strong vibration may increase the risk of runner failure. Load rejection transient process is crucial for pumped-storage hydropower stations, and the evolution laws of the runner dynamic stress during this process need profound research. In this study, the evolution of the runner dynamic stress of a prototype pump-turbine during a load rejection transient process was simulated using the one-dimensional and three-dimensional coupling (1D-3D) method and the fluid-structure interaction (FSI) method. The results of this dynamic transient process were compared to the results of the static working points. It is shown that the rotational speed dominates the mean value of stress while the fluctuating amplitude of stress is dominated by pressure fluctuations, which are larger in the S-shaped region of characteristics. Compared with the static working point solutions, the transient process solutions can better reflect the stress fluctuations and should be used for safety assessment.
Study on noise characteristics of centrifugal fan based on blade loading distribution
Authors: Cui Wenhao , Feng Jianjun , Zhu Guojun , Ge Zhenguo , Wang Wei , Li Chenhao 
Published: June 2024

Abstract
In order to explore the influence of different blade loading distribution on the noise characteristics of centrifugal fan, this paper takes the blade loading distribution of the hub and shroud of the centrifugal fan as the design parameters, and establishes four centrifugal fan models with different blade loading distribution. The aerodynamic noise and radiation noise of the centrifugal fan are calculated by the transient results. The research shows that the noise characteristics of the fan change with the change of the blade loading distribution. The maximum aerodynamic noise is generated at the volute tongue, and the total sound pressure level of the gas along the flow direction shows a downward trend. The area with large vibration displacement on the surface of the volute occurs at the back cover plate of the volute, and the noise sound pressure level radiated outward is also higher. The purpose of noise reduction can be achieved by controlling the blade loading distribution.
Numerical prediction of erosion of Francis turbine in sediment laden flow
Authors: He Sanwei , Song Xijie , Wang Li , Zhao Mingliang , Wang Zhengwei 
Published: June 2024

Abstract
Francis turbine is adopted in many hydropower stations widely. Usually, the operating environment is sandy water flow, and the unit will suffer from sediment wear, affecting the operating life of the unit. This article focuses on the wear problem of hydraulic turbines and uses numerical simulation to conduct research on sediment wear. Lagrange model is adopted to predict the sediment concentration in the flowpassageof the unit, and Tabakoff model is used as the wear model. The results indicate that the guide vane blades, seat rings, end clearance, and runner blades and lower rings of hydraulic turbines are prone to sediment erosion. According to friction mechanics, these areas are mainly subjected to impact wear caused by particle impact at the inlet of the guide vane and the runner. The wear on the surface of the blade passage is mainly caused by frictional wear caused by particle sliding motion. The research results provide a certain help for the optimization of hydraulic turbine wear resistance in engineering.
Pressure Pulsation Analysis of 2D NACA66 Airfoil Based on Pulsation Tracking Network
Authors: Lu Jiahao , Liu Qiang , Pan Jiale , Guang Weilong , Tao Ran , Zhu Di , Xiao Ruofu 
Published: June 2024

Abstract
The NACA66 airfoil is used extensively in the design of turbine runners and as a core component, the airfoil plays a vital role in the operation of the turbine. In order to investigate the details of the effect of the NACA66 airfoil on pressure pulsation, this paper investigates and analyses the NACA66 airfoil with a work angle of 14°. This study combines computational fluid dynamics (CFD) with pulsation tracking network (PTN) technology to numerically simulate the NACA66 airfoil. The simulation results show that the dominant pressure pulsation frequencies in the computational domain are mainly 100hz, 3500hz, and 6900hz, and the pressure pulsation amplitude varies for different dominant frequencies. When the dominant frequency is 100hz and 3500hz, the pressure pulsation amplitude continues to decrease from the inlet to the outlet of the calculation domain, but a small increase in pressure pulsation amplitude occurs at the trailing edge of the airfoil. When the dominant frequency is 6900hz, the pressure pulsation amplitude decreases from the inlet to the outlet of the calculation domain and increases sharply below the airfoil, which is greater than the pulsation amplitude in the surrounding area. This paper reveals the dominant frequency of the NACA66 airfoil disturbance based on PTN technology and the variation of the pressure pulsation amplitude at different dominant frequencies. The content of this study can help to explore more deeply the pressure pulsation problem generated by airfoil winding and provide ideas for solving the pressure pulsation engineering problem.
Multivariate iterative nonlinear chirp mode decomposition: principles and applications
Authors: Huang Jie , Li Chaoshun 
Published: June 2024

Abstract
The rotor-bearing system (RBS) of a hydroelectric unit includes multiple components such as the rotor, rotor shaft, coupling, turbine, and main shaft. There is a strong coupling relationship between the vibration signals of multiple bearing sections. At the same time, the vibration signal of the RBS contains rich frequency components, which can effectively reflect the operating state of the shaft system of the unit. Therefore, synchronous signal analysis across multiple rotor bearing sections is required to completely grasp the operating status of the unit. In this study, the Multivariate Iterative Nonlinear Chirp Mode Decomposition (MINCMD) is proposed to analyze signals on multiple sections simultaneously. MINCMD follows the step-by-step extraction idea of Adaptive Multivariate Chirp Mode Decomposition (AMCMD), but it adopts a new algorithm framework by modifying the objective function. Furthermore, AMCMD does not converge well without a good initial instantaneous frequency (IF). Therefore, a method based on parameterized demodulation (PD) is introduced in MINCMD to solve the multi-channel frequency initialization problem. The effectiveness of the proposed algorithm is verified through a simulation test and real data from hydroelectric units.
Measuring uncertainty of hydraulic generator efficiency by calorimetric method
Authors: Guo Xinjie , Pan Chunqiang , Li Hongtao , Xu Xuhui , Jiang Cuiwei 
Published: June 2024

Abstract
Calorimetric method is generally performed on determination of hydraulic generator efficiency. Generator losses could be evaluated by measuring the heat taken by cooling medium or dissipated from a reference surface. To satisfy the requirements of measuring uncertainty in IEC 60034, special attention must be paid. An estimation method is proposed and performed on a hydraulic generator for calorimetric test. Estimation result shows that discharge of cooling water must be reduced to a rather low value to ensure the measuring uncertainty of calorimetry within 3%. Also, a lower cooling discharge can bring higher temperature rise then reduce the measuring uncertainty caused by temperature measurement. Furthermore, to reduce the measuring uncertainty of cooling discharge, flowmeters must be installed correctly.
Assessment of Fiber Bragg Grating sensors for monitoring induced strains on the draft tube cone of hydraulic turbines
Authors: Sánchez-Botello X , Roig R , de la Torre O , Madrigal J , Sales S , Mulu B , Högström C-M , Escaler X 
Published: June 2024

Abstract
In hydraulic turbines, several flow instabilities can take place inside the draft tube cone during off-design and transient operating conditions such as the rotating vortex rope which can severely damage the structure if sustained in time. In the frame of the AFC4Hydro H2020 research project, an extensive measurement campaign has been carried out to monitor and predict this rotating vortex rope phenomenon in a reduced scale Kaplan turbine model at the Vattenfall Research and Development facility in Älvkarleby, Sweden. The hydraulic turbine model has been operated in propeller mode with a fixed blade angle corresponding to its best efficiency point. Several sensors have been placed along the test stand to monitor vibrations, strains and pressures. Concretely, the present paper assesses the performance of using Fiber Bragg Grating sensors to measure the strains induced on the draft tube cone walls with high-spatial resolution in three different zones of influence: the upper and lower flanges and the vertical cone wall between the runner outlet and the elbow. To do so, a total of 3 arrays embedding a total of 48 Fiber Bragg Grating sensors were glued inside three grooves previously machined on these particular areas of the draft tube cone. Analysing the frequency response of the different Fiber Bragg Grating sensors, the strain patterns induced by the rotating and plunging components of the rotating vortex rope have been precisely determined. Moreover, their impacts at the different part load conditions tested have also been quantified.
Research of Model Characteristics based on Probability Statistics Method for Condition Evaluation of Hydropower Unit
Authors: Zhou Ye , Cao Dengfeng 
Published: June 2024

Abstract
The paper introduces the condition evaluation method of hydropower unit based on the health sample with the long time and massive condition monitoring data. By analysing the probability statistics characteristics of units’ status data, it designs the unit operating condition model, and makes the statistics analysis for two-dimension model, which consists of the unit feature value and single influence factor such as water head or active power, furthermore, it built and analyses the three-dimension condition model to get the different influence result by comparing the multi-dimension models. The statistical characteristics of unit operating condition model obtained can be the foundation and basis for implement of hydropower unit health condition evaluation.
Multi-channel deterioration trend prediction of pumping storage unit based on temporal graph convolution network
Authors: Xiao Xiangqu , Li Chaoshun 
Published: June 2024

Abstract
The safe and stable operation of pumped storage units is related to the integrity of the power grid, and it is necessary to study the prediction of unit deterioration trends. Traditional degradation trend prediction methods are mostly for single channel, without considering the interaction between different channels of the shaft system. Therefore, a multi-channel degradation trend prediction model for pumped storage units shaft system is proposed. Firstly, the healthy model is obtained by constructing the mapping relationship between the working parameters and the swing of the shaft system through the fully connected network. Secondly, the deterioration trend sequence of each channel is calculated based on the historical monitoring data of each channel of the unit shaft system and the corresponding healthy model. Finally, the correlation coefficient analysis method is used to calculate the correlation between each channel, and the temporality of the degradation sequence of each channel and the correlation between channels are learned through the spatio-temporal graph convolutional network to realize the prediction of multi-channel degradation trends. The proposed model is verified by using the data of a pumped storage power station. The results show that the proposed model can accurately predict the multi-channel deterioration trend.
Fault diagnosis method of rolling bearing based on MSSA-VMD algorithm
Authors: Yu Tian , Li Chaoshun 
Published: June 2024

Abstract
Early fault signals of rolling bearings are affected by environmental noise, which makes it challenging to extract fault characteristics. In this paper, a bearing fault diagnosis method based on Sparrow Search Algorithm (SSA) and Variable Modal Decomposition (VMD) is proposed to achieve adaptive signal decomposition and feature extraction. First, the fusion shock index is constructed based on the envelope spectrum pulse factor and correlation coefficient to measure the shock fault components. Then, the VMD parameters are adaptively optimized by the improved sparrow search algorithm MSSA, and the fusion shock index is established as the optimal modal component selection method of the fitness function. Finally, the envelope spectrum of the signal after noise reduction is analyzed to extract the fault characteristic frequency. By analyzing the bearing outer ring fault signal and inner ring fault signal under strong noise, the results show that this method can adaptively determine the mode number and penalty factor of VMD, effectively extract the fault signal characteristics, and realize rolling bearing fault diagnosis.
Research on low-carbon optimization methods for regional energy interconnection systems considering multi-energy coupling characteristics
Authors: Guo Feng , Dou Zhenlan , Sun Chen , Zhang Chunyan , Jiang Kuan , Guo Bingtao , Yang Zijie , Zhang Baihan 
Published: June 2024

Abstract
With the increasing application of multi-energy cogeneration, distributed renewable power generation, and multi-energy storage in various multi-energy systems, their efficient collaborative optimization has become the key to further improving emissions. This article utilizes energy hubs to integrate energy equipment with multi-energy coupling and multi-source supply characteristics and constructs a regional interconnected energy system that considers multi-energy coupling characteristics. A multi-objective optimization model for the above-mentioned energy system is established, including economic, low-carbon, and safe aspects such as operating costs, process emissions, and operational safety, and the raccoon optimization algorithm is applied to solve the model. The experimental results show that compared with classical scheduling algorithms, the proposed method can effectively reduce carbon emissions at a certain operating cost.
Research on photovoltaic energy storage capacity allocation considering distribution network reliability and economy
Authors: Liu Zhongjian , Li Qingxi , Jiang Shigong , Qian Ruixin , Ma Liang , Liu Xiaoming , Sun Donglei 
Published: June 2024

Abstract
The rapid development of renewable energy sources, such as solar cells, is creating major challenges for the reliable and economical operation of distribution networks. This paper proposes an optimal PV storage system configuration method that considers the life cycle cost of energy storage devices, establishes a multi-objective optimization model for PV storage system configuration to minimize overall system cost and selection factor, and achieves optimal system power configuration by solving the model using improved NSGA-III optimization algorithm. To compare and analyse optimization results, a regional PV storage system was developed as an example, and results show that when using an improved NSGA-III optimization algorithm to solve the PV storage system model and optimize system power configuration, compared with PV storage system using PSO algorithm, the total economic cost of the system is reduced by 10.4% and can be realized.
Geological engineering double sweet spot evaluation of thin coal seam reservoirs based on facies control: A case study of tight sandstone gas in the Shenfu block of the Ordos Basin
Authors: Xu Wei , Zhang Bing , Zhou Zhan , Wei Chao , Zhang Zhaopeng , Gong Ding 
Published: June 2024

Abstract
The development of thin coal layers within the Shenfu tight sandstone reservoirs significantly impacts the control of hydraulic fractures over the actual sweet spots, leading to considerable inter-well production variability. This paper establishes a connection between individual well sweet spots and block sweet spots through a refined lithofacies model and conducts a comprehensive double sweet spot secondary optimization in conjunction with the characteristics of thin coal layer development. The research findings indicate the following: Class I sweet spots ≥0.46, 0.37≥ Class II sweet spots <0.46, 0.3≥ Class III sweet spots <0.37; fractures will be captured by the coal layer if the thin coal layer is more than 5 m away from the perforation point or if the coal layer thickness exceeds 3 m; the secondary sweet spot optimization can eliminate the influence of thin coal layers and establish a three-dimensional comprehensive double sweet spot model suitable for the study area.