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    Fundamental Research
  • Fundamental Research
    Numerical Simulation of Flow and Heat Transfer Characteristics of Supercritical CO2 in Inclined Tube Under Heating Condition
    DONG Xinyu, ZHANG Yuxuan, LIU Lu, WANG Teng, WANG Tai, YAN Run
    2024, 44(10): 1503-1514. https://doi.org/10.19805/j.cnki.jcspe.2024.230526
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    The supercritical CO2 (SCO2) Brayton cycle has a broad application prospect, and the flow and heat transfer characteristics of SCO2 are very important for the power generation efficiency and safe operation of the system. The flow and heat transfer characteristics of SCO2 in inclined up-tube and down-tube under heating condition were analyzed by FLUENT numerical simulation software. The effects of tilt angle, flow direction and operating conditions on the resistance and heat transfer coefficient of SCO2 were studied. The results show that, the pressure decreases and the convective heat transfer coefficient and resistance coefficient increase with the increase of the up-tube tilt angle. The convective heat transfer coefficient and the pressure increase and the resistance coefficient decreases with the increase of the down-tube tilt angle. The change of tube tilt angle has little effect on the uplift and thermal acceleration effect. The overall heat transfer performance of down-tube is better than that of up-tube, and the comprehensive heat transfer performance of vertical down-tube is the best. The influence of pressure and heat flux on SCO2 convective heat transfer coefficient is small, but the influence of mass flux is larger.
  • Fundamental Research
    Study on Flow Patterns and Local Heat Transfer Characteristics in Steam Heated Vertical Narrow Rectangular Channel
    GU Shengjie, TAO Leren, JIN Cheng, JU Yiwei, ZHAO Xiefei
    2024, 44(10): 1515-1524. https://doi.org/10.19805/j.cnki.jcspe.2024.230446
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    In order to clarify the heat transfer characteristics of flow boiling at each stage in vertical narrow rectangular channel and optimize the performance of the heat exchanger, the experimental study of the flow pattern and local heat transfer characteristics in steam heated vertical narrow rectangular channel with dimensions of 1 400 mm×250 mm×2.75 mm (height×width×depth) was carried out, using deionized water as the working medium. The experimental flow patterns were compared with the existing flow patterns under different heating conditions. The effects of inlet temperature, mass flux and heating power on the local heat transfer characteristics were analyzed combined with the flow pattern variations. Based on the parametric analysis of the experimental data, a new flow boiling heat transfer correlation formula was obtained, which was applicable to the experimental conditions. Results show that the increase of inlet temperature has positive effect on heat transfer at nucleate boiling section, while the effect on the local heat transfer coefficient is small under churn flow phase. The increase of mass flux decreases the local heat transfer coefficient in nucleate boiling stage and enhances the local heat transfer coefficient in the evaporation zone of liquid film flow. The peak of the local heat transfer coefficient shows a tendency to shift to the left as the heating power increases. The new heat transfer correlation formula can well predict the local heat transfer coefficient of flow boiling in the steam heated vertical narrow rectangular channel under experimental conditions.
    • Power Equipment and System
  • Power Equipment and System
    Life Expenditure Calculation Method for Steam Turbine Rotor Based on Damage Mechanics Analysis
    WANG Yuanliang, LIAO Yanqing, PENG Jiahui, XU Hong, NI Yongzhong
    2024, 44(10): 1525-1532. https://doi.org/10.19805/j.cnki.jcspe.2024.230377
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    Thermo-mechanical response of 1 000 MW ultra-supercritical steam turbine rotor under different start-up conditions was numerically simulated by Chaboche viscoplastic constitutive model based on coupled damage in ANSYS finite element software. Based on analysis results of stress and damage in the dangerous area of rotor surface, the functional relationship between steam turbine start-up parameters and rotor maximum damage was established, and a rotor life expenditure calculation method for complex start-up and loading conditions was proposed. Results show that the calculation results of the model are basically consistent with the data in the turbine life expenditure distribution table under standard start-up conditions, verifying the validity of the model. When the proposed method was used, the life expenditure of the rotor and the thermal stress in dangerous area can be quickly calculated by simple processing actual start-up curves.
  • Power Equipment and System
    Cavitation State Recognition Method of Hydraulic Turbine Based on Transfer Learning and CNN-LSTM
    LIU Zhong, ZHOU Zehua, ZOU Shuyun, LIU Zhen, QIAO Shuaicheng
    2024, 44(10): 1533-1540. https://doi.org/10.19805/j.cnki.jcspe.2024.230470
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    Aimed at such problems as containing noises in hydraulic turbine cavitation acoustic emission signals, noise reduction and feature extraction relying on manual operation, and the accuracy of deep learning model heavily depending on massive training data, a method of hydraulic turbine cavitation state recognition was proposed based on transfer learning and convolutional neural networks-long short term memory network (CNN-LSTM). First, the data was input into CNN to extract the hidden features. Then, the temporal information implied in the feature was extracted from LSTM and the cavitation type was output. The cavitation state recognition model based on CNN-LSTM was established by training network parameters. Finally, cavitation state under similar working conditions was identified by introducing transfer learning. Results show that the proposed model can accurately identify three different types of turbine cavitation with average recognition accuracy of high level. Compared with traditional deep learning model, the proposed model has obvious advantages in recognition accuracy in very few sample learning tasks.
  • Power Equipment and System
    Effect of Thrust Bearing on the Lateral Vibration Characteristics of the Shafting System of Hydro-Generator Unit
    YE Haoyang, ZHANG Wanfu, HUANG Jinhui, LI Chun
    2024, 44(10): 1541-1549. https://doi.org/10.19805/j.cnki.jcspe.2024.230460
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    A finite element model of a 300 MW hydro-generator unit shaft system supported with three guide bearings and one thrust bearing was established. The influence of thrust bearings on the lateral vibration of shaft system was studied by finite element method. The influence of bending stiffness and axial stiffness of thrust bearings on the lateral vibration was calculated and analyzed, and the influence of unbalance force and phase difference of generator rotor on shaft system vibration was studied. Results show that compared with the non-consideration of thrust bearing, when considering the bending stiffness of thrust bearing, the first to third order natural frequencies of the shaft system at the rated speed increase by 5.35%, 1.89% and 1.56% respectively. When the unbalanced force at the rotor of the generator is 100 kg·m and the phase difference is 180° at the rated speed, if the bending stiffness is 8.2×106 N/m, the lateral amplitude of the lower guide bearing, the upper guide bearing, the thrust bearing and the collector is reduced by about 17.44%, 6.72%, 17.04% and 28.76%, respectively. When the unbalance force is 100 kg·m and the phase difference is 0°, the lateral amplitude of each component is reduced by 3.31%, 2.78%, 9.46% and 15.01%, respectively, taking into account the bending stiffness.
  • Power Equipment and System
    Experimental and Simulation Study on Sliding Wear Behavior Between Heat Transfer Tube and Support Plate in Steam Generator
    ZHENG Yu, BAO Shiyi, XU Lei, LOU Chengming, CHEN Wei, YUAN Wei
    2024, 44(10): 1550-1557. https://doi.org/10.19805/j.cnki.jcspe.2024.230511
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    Experimental study on sliding wear behavior between 405 alloy support plate and Inconel 690 alloy heat transfer tube was carried out, and the influence of different loads and cycle times on the wear between the tube and plate was discussed. The sliding wear mechanism between the tube and plate was studied based on the micro-surface morphology of the wear surface. A sliding wear calculation model between 405 alloy support plate and Inconel 690 alloy heat transfer tube was established based on the ARCHARD wear model and ABAQUS adaptive mesh technology. Results show that the surface wear mechanism of the heat transfer tube mainly includes adhesive wear and abrasive wear when the heat transfer tube experiences sliding wear. The model can accurately predict the contour shape of the wear surface and the change of wear volume with the loads and cycle times.
    • New Energy Resources and Energy Storage
  • New Energy Resources and Energy Storage
    Optimization Design of Wind Turbine Tiplets Based on Bidirectional Fluid-Structure Coupling
    ZHANG Ling, YUE Xu, XIU Dongbo
    2024, 44(10): 1558-1564. https://doi.org/10.19805/j.cnki.jcspe.2024.230365
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    Taking a WindPACT 1.5 MW wind turbine as research object, blade tip winglets were designed by orthogonal test with parameters of thickness, taper and tilt angle, and bidirectional fluid-structure coupling was calculated. Results show that the vibration frequency of the blade decreases after adding winglet. The maximum tensile stress of the blade tip winglet is 58.707 MPa, and its maximum compressive stress is 29.87 MPa, which means the blade material can meet strength requirements, and will not break. As the thickness, taper and inclination angle of the tip winglet increase, the tensile stress and compressive stress increase accordingly. For the deformation of the tip winglet, the inclination angle has the greatest effect, followed by taper, and the thickness has the least effect. Bidirectional fluid-structure coupling can obtain more accurate results than one-way fluid-structure coupling method.
  • New Energy Resources and Energy Storage
    Short-term Wind Power Prediction with Deep Convolutional-Temporal Networks Considering Enhanced Feature Selection
    FU Bingzhe, WANG Wei, REN Guorui, YANG Jian, LI Yihuan
    2024, 44(10): 1565-1573. https://doi.org/10.19805/j.cnki.jcspe.2024.230510
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    Accurate wind power prediction plays a vital role in ensuring grid security and rational utilization of wind resources. To improve the wind power prediction accuracy, a wind power prediction strategy including anomaly detection, feature selection and enhancement, and hyperparameter tuning was proposed. Firstly, the isolation forest algorithm was employed to identify and eliminate the outliers and redundancies within the wind power data. Subsequently, the maximum information coefficient (MIC) was introduced as an evaluation indicator for feature selection to enable the acquisition of highly correlated input features. Additionally, an optimized model combining convolutional neural network (CNN) and gated recurrent unit (GRU) neural network was established, where the CNN layer further enhanced the comprehension of feature importance through MIC, while the multi-layer GRU layers modeled the temporal relationship of wind power. Results show that the proposed optimized neural network model outperforms other predictive models in the literatures, yielding smaller prediction errors with a mean increase of coefficient of determination by 4.44%, and an average decrease of mean absolute error and root mean square error by 62.02% and 61.51%, respectively. High predictive precision is achieved.
  • New Energy Resources and Energy Storage
    Experimental Operation Performance Analysis on a Solar PVT Heat Pump System with Combined Modules
    LU Wanglin, LI Zheng, JIANG Shan
    2024, 44(10): 1574-1581. https://doi.org/10.19805/j.cnki.jcspe.2024.230471
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    Based on existing photovoltaic modules, the combined PVT modules were formed by installing heat collectors, and an experimental setup of combined PVT heat pump system was established. The system operation performance experiments were conducted under two working conditions of sunny and cloudy typical days, and the water in the water tank was heated from the ambient temperature to 60 °C. Results show that the average coefficient of performance of the system are 4.11 and 4.20 under the typical sunny and cloudy working conditions, respectively, which are higher than air-source heat pumps under the same working conditions. Correspondingly, the maximum power generation efficiencies are 13.2% and 19.9%, respectively. The surface temperature of PVT modules is lower than 40 °C, which reveals apparent surface cooling and efficiency improvement effects. The average heat acquisition factors are 48% and 71% for the sunny and cloudy typical days, respectively. The dimensionless pressure loss coefficient is maintained in the range of 0.030-0.047, which indicates that the flow is well uniform.
  • New Energy Resources and Energy Storage
    Stress Analysis of Composite Material Flywheel Rotor for Energy Storage Under Muti-rim Cooperation
    ZHANG Yu, TENG Wei, WANG Yajun, QIN Run, PENG Dikang, LIU Yibing
    2024, 44(10): 1582-1591. https://doi.org/10.19805/j.cnki.jcspe.2024.230487
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    Stress state of composite flywheel rotor under multi-rim fit structure was analyzed. Taking consideration of the initial static stress after multi-rim fit of flywheel rotor, the static strain after fit, the stress of multi-rim interference fit under working conditions, as well as the effect of composite wheel flange fiber winding on stress, a theoretical model for axisymmetric flywheel rotor of orthotropic material was established, and the radial and circumferential stress distributions of rotor rims under centrifugal force and interring fitting pressure were calculated. The relationship between the interference amount and the stress of each rim of the rotor was analyzed, and the selection criterion of the interference amount was established. Results show that with the increase of interference amount, the stress between the metal shaft and the metal hub will first decrease and then increase, and the stress between the composite wheel flange will increase accordingly.
  • New Energy Resources and Energy Storage
    Research on Multi-physics Domain Modeling and Dynamic Simulation of Pumped Thermal Electricity Storage System
    AN Xugang, HE Qing, ZHANG Qianxu
    2024, 44(10): 1592-1599. https://doi.org/10.19805/j.cnki.jcspe.2024.230508
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    Pumped thermal electricity storage (PTES) is a new type of physical energy storage technology. To study the dynamic characteristics of PTES system, a dynamic simulation physical model of Brayton cycle PTES system was established, and dynamic response of the main characteristic parameters during start-up process of energy storage/release stage was analyzed, including pressure, temperature, mass flow, power, etc. Results show that in order to make the system operate under the rated condition, the system volume should be selected as 5 m3, and the initial pressure in energy storage/release stage should be selected as 2.1 and 3.8 MPa, respectively. At a given speed increase rate, the main characteristic parameters of the system gradually change from the initial values according to a certain trend, and reach the rated values in about 1 400 s. The simulation model and research results can provide references for the dynamic characterization of start-up process of PTES system.
    • Digitalization and Intelligentization
  • Digitalization and Intelligentization
    Multi-domain Coupled Dynamic Modelling and Full Operating Condition Hierarchical Cooperative Control of CDR Wind Turbine
    HU Yang, SHAO Maofeng, WANG Weiran, ZHANG Chong
    2024, 44(10): 1600-1610. https://doi.org/10.19805/j.cnki.jcspe.2024.230450
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    For a cascade dual rotor (CDR) wind turbine, a method of modelling the approach wind velocity of the rear rotor under the cascade layout of the front and rear rotors was proposed based on free vortex wake theory. A multi-domain coupled dynamic model of "aerodynamic-transmission-electrical-support" was established for the first time, which including the key sub-systems of the front and rear rotors, drive shaft system, and tower tube. Considering the structure and operation characteristics of CDR wind turbine, a new hierarchical cooperative control architecture of the dual rotor unit was designed for the safe operation and maximum power generation output of CDR wind turbine. A refined simulation software for CDR wind turbines with different capacity levels was developed based on Fortran language, and a simulation experiment platform was set up in combination with a high-performance server. In order to verify the effectiveness of the programme, the design parameters of a typical 2.7 MW CDR wind turbine were configured, and the load analysis and performance verification were carried out under full operating conditions in accordance with International Electrotechnical Commission (IEC) standard. Results show that the model can accurately reflect the coupling dynamic characteristics of each subsystem in wind turbine, and the proposed hierarchical cooperative control method has a good tracking performance of optimal power curve within the safe load range.
  • Digitalization and Intelligentization
    A Two-level Optimization Scheduling of a Virtual Power Plant Based on Stackelberg and Cooperative Game Theory Under the Dual Carbon Goals
    ZHOU Jianguo, WU Zhaobo
    2024, 44(10): 1611-1619. https://doi.org/10.19805/j.cnki.jcspe.2024.230514
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    Under the dual carbon goals in China, the large-scale integration of new energy power generation into the virtual power plant (VPP) will lead to high penalty costs in electricity market transactions. A two-level game model for VPP participating in day-ahead market bidding was designed, with the objective of maximizing two-level benefits through scheduling optimization of VPP. Firstly, considering the uncertainty of wind power plants (WPP) and electric vehicle aggregator (EVA) using scenario generation and reduction techniques, a lower-level electricity bidding model composed of WPP, EVA, and gas turbine (GT) cooperation was designed, along with an upper-level electricity price bidding model for the VPP operator. Secondly, based on the hierarchical relationship between the two sub-models, the two-level model was transformed into a mixed complementarity problem (MCP) using the Karush-Kuhn-Tucker (KKT) conditions, and an optimal solution was obtained. Profit allocation for the cooperative parties was conducted using the Shapley value method. Numerical examples show that the designed model can effectively reduce carbon emissions and wind power penalty costs, while increasing participant benefits.
  • Digitalization and Intelligentization
    Wind Turbine Gearbox Condition Monitoring Based on Improved Instance Learning Algorithm
    ZHANG Shuyao, LIU Changliang, WANG Ziqi, LIU Shuai, LIU Weiliang
    2024, 44(10): 1620-1631. https://doi.org/10.19805/j.cnki.jcspe.2024.230509
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    The operation of a wind turbine (WT) gearbox is a complex nonlinear process. Utilizing instance-based learning (IBL) algorithm to establish models can effectively monitor conditions of the gearbox. In view of the fact that IBL algorithm is sensitive to the quality of training data, a two-step active learning (AL) sample selection method considering multiple properties was proposed. Firstly, a grid partitioning initial sample selection method based on Latin hypercube sampling was proposed, and outliers were removed using z-score. Then, the first step was to select candidate samples based on the comprehensive scores of informativeness and representativeness to avoid the influence of outliers. The second step was to sparsize candidate samples based on diversity to avoid the impact of redundant points. Finally, the residual of instance-based learning regression (IBLR) model was analyzed based on exponential weighted moving average control chart, and the status of WT gearbox was monitored based on the failure rate. The model was verified using actual fault data of a certain WT. Results show that the proposed method can select high-quality samples, improve the model accuracy compared to the unmodified model on the validation set, and increase the computational efficiency by about 50%, which can effectively achieve early warning of the gearbox faults.
    • Green Energy and Low-carbon Technology
  • Green Energy and Low-carbon Technology
    Study on Crystallization Behaviour of Captured Products from Ammonia Carbon Capture Slurry in Coal-fired Power Plant
    MA Shuangchen, GAO Heli, CHEN Liutong, JIA Jun, FAN Shuaijun, CHEN Wentong, WANG Xiaohua
    2024, 44(10): 1632-1639. https://doi.org/10.19805/j.cnki.jcspe.2024.230523
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    Under the background of carbon emission from coal-fired power plants, the crystallization process of carbon dioxide absorbed by ammonia water was used as the research object. Based on the classical nucleation theory, the changes in the crystallization rate of ammonium bicarbonate with temperature, stirring speed, salt additives adding were studied, by using temperature, pH and conductivity methods. The effect of additives on crystallization was analyzed by scanning electron microscope (SEM) and X-ray diffraction (XRD). Results show that the crystallization reaction of ammonium bicarbonate is affected by the kinds of additives at water bath temperature of 25 ℃ and stirring speed of 550 r/min. The addition of sulfate ions will slow down the reaction, while the addition of magnesium chloride can accelerate crystallization rate and generate crystals with stable structure.
  • Green Energy and Low-carbon Technology
    Mechanistic Study on Mercury Adsorption by CuCl2-modified Biomass Char Based on Density Functional Theory
    MA Ziran, WANG Hongyan, ZHAO Chunlin, ZHOU Jiali, PENG Shengpan, MA Jing, WU Jianfei
    2024, 44(10): 1640-1646. https://doi.org/10.19805/j.cnki.jcspe.2024.230369
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    Based on density functional theory, models of rice husk char and CuCl2-modified rice husk char were established using Materials Studio software to calculate and analyze these models before and after mercury adsorption. The mechanism of mercury removal by rice husk char was analyzed from a microscopic perspective. Results show that during the adsorption process, electrons on Hg atoms are transferred to the surface of rice husk char. Van der Waals forces are formed between them, and Hg atoms are binded to the surface of rice husk char in the form of physical adsorption. While CuCl2-modified rice husk char can break one of Cu-Cl bonds in CuCl2 on the surface of char in the mercury adsorption process. Cu atom and Cl atom will combine with Hg atom to form mercury chemisorption, which results in higher mercury removal efficiency by CuCl2-modified rice husk char than that of original rice husk char. It can provide theoretical guidance for the industrial application of biomass char adsorbents to mercury removal by clarifying its corresponding mechanism.
  • Green Energy and Low-carbon Technology
    Numerical Research on Evaporation Characteristics of Desulfurization Wastewater Droplets Based on Reaction Engineering Approach
    ZHAO Liang, LI Linggang, ZHANG Juan, LI Ang, CHEN Jiawei, PAN Danping, YANG Linjun
    2024, 44(10): 1647-1655. https://doi.org/10.19805/j.cnki.jcspe.2024.230465
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    Influence of inlet flue gas temperature, inlet flue gas flow rate and tower diameter on evapration characteristics of desulfurization wastewater droplets in a rotary spray evaporation equipment of a coal-fired power plant was studied by numerical simulation. In order to improve the heat and mass transfer model of droplets evaporation, their heat and mass transfer process was described by apparent activation energy function of droplets in reaction engineering approach (REA) and compiled into the calculation process of discrete phase. Results show that increasing the temperature and flow rate of inlet flue gas can shorten the evaporation residence time and vertical evaporation distance of droplets. Increasing the diameter of drying tower can prolong the residence time of high-temperature flue gas in the tower and improve the swirl intensity, which can accelerate the evaporative heat transfer process of droplets.
  • Green Energy and Low-carbon Technology
    Study on Rotary Spray Evaporation and Product Characteristics of Concentrated Desulfurization Wastewater
    CHEN Haijie, MA Xiaoyue, WEI Xin, ZHAN Lingxiao, CHEN Heng, YANG Linjun
    2024, 44(10): 1656-1662. https://doi.org/10.19805/j.cnki.jcspe.2024.230484
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    Experimental research has been conducted on the spray evaporation of concentrated desulfurization wastewater on a rotary spray evaporation test platform. Evaporation characteristics of wastewater droplets under different operating conditions and concentration ratios were analyzed. The microscopic morphology, composition, and hygroscopicity of the evaporation products were also tested. Results show that with the increase of concentration ratio, the average temperature inside the tower slightly increases, while water vapor volume fraction at the tower outlet decreases, under the same inlet flue gas conditions (360 ℃, 500 m3/h). When the gas-liquid ratio is greater than 9 500 m3/m3, the rotary spray evaporation tower will exhibit good adaptability to desulfurization wastewater with different concentration ratios, maintaining the water content of the products below 2%. The hygroscopicity of the evaporation products of desulfurization wastewater with low concentration ratios is relative weak due to the small proportion of salts, while the evaporation products of wastewater with high concentration ratio show strong hygroscopicity due to the significant increase in content of crystalline salts.