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    Fundamental Research
  • Fundamental Research
    Identification of Two-phase Flow Pattern Based on Ensemble Learning and Electrical Resistance Tomography
    ZHANG Lifeng, XIAO Kai
    2023, 43(9): 1103-1110. https://doi.org/10.19805/j.cnki.jcspe.2023.09.001
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    In order to identify the flow pattern of two-phase flow more accurately and efficiently, a flow pattern identification method using ensemble learning was proposed. The data of four flow pattern of gas-liquid two-phase flow in the vertical pipeline were collected by electrical resistance tomography (ERT) system. Firstly, the data were averaged by selecting a certain number of frames, and the extreme gradient boosting (XGBoost) algorithm was constructed by using multiple classification and regression trees (CART) as the weak classifier, which was pre-trained using feature gain as an indicator for feature selection to achieve data dimensionality reduction. Then, five deep neural network (DNN) models and adaptive boosting (AdaBoost) algorithm were combined to construct the DNN-AdaBoost algorithm for flow pattern identification of gas-liquid two-phase flow. Finally, the DNN-AdaBoost algorithm was compared with other flow pattern identification algorithms. Results show that the identification accuracy of the DNN-AdaBoost algorithm is higher than other algorithms, and its average identification accuracy can reach 98.25%.
  • Fundamental Research
    Influence of Step-cooling Test on Microstructure and Mechanical Properties of 30Cr2Ni4MoV Steel for LP Rotor of Nuclear Power Plant
    CUI Zhengqiang, WANG Miaomiao, SHI Kexian, WENG Weijie
    2023, 43(9): 1111-1115. https://doi.org/10.19805/j.cnki.jcspe.2023.09.002
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    In order to solve the problem of long-term aging embrittlement of 30Cr2Ni4MoV steel of low pressure (LP) rotor, effect of step-cooling test on microstructure and mechanical properties of 30Cr2Ni4MoV steel for LP rotor of nuclear power plant was investigated by using chemical composition analysis and microstructure observation, tensile test, impact and hardness test at room temperature, as well as fracture appearance transition temperature (FATT) tests. Results show that tensile strength, hardness and the room-temperature impact values decrease, and the FATT rises up with the increase of grain size and coarsening of the carbide particles during step-cooling test. However, the decline of mechanical properties after step-cooling test is not obvious. It is concluded that the LP rotor with 30Cr2Ni4MoV steel used in this study is insensitive to aging embrittlement.
    • Power Equipment and System
  • Power Equipment and System
    Study on Load Response Characteristics of a 300 MW Circulating Fluidized Bed Unit with Deep Peak Regulation
    ZHANG Hongfu, GAO Mingming, YU Haoyang, YUE Guangxi
    2023, 43(9): 1116-1122. https://doi.org/10.19805/j.cnki.jcspe.2023.09.003
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    At present, circulating fluidized bed (CFB) units need to participate in deep peak loading and rapid load changing operation, and the load response rate at the initial load changing stage is mainly determined by the heat storage characteristics of the steam-water side. Therefore, a quantitative calculation method for the heat storage of subcritical CFB units in the steam-water side was proposed. The steam-water process of a 300 MW CFB unit with deep peak regulation was segmented according to the characteristics of the steam fluid. The heat storage coefficients of steam fluid and metal at each section in different load operating conditions (30%-100% load) were calculated respectively by combining with design data and actual operating parameters of the boiler. Considering the influence of steam turbine thermal efficiency, the sustainable time of heat storage and load response characteristics of CFB boiler were analyzed. Results show that the heat storage coefficients of the unit in the steam-water side increase with the decrease of the load, and the change rate is larger under 50% load. Considering the difference of the unit operating stability margin, the sustainable time of heat storage utilization in the steam-water side decreases, and the load response capacity of the unit decreases significantly with the decrease of load.
  • Power Equipment and System
    Numerical Study on the Influence of Blade Tip Slot and Winglet on the Performance and Noise of Axial Fans
    YANG Tiankang, YE Xuemin, LIU Yang, LI Chunxi
    2023, 43(9): 1123-1131. https://doi.org/10.19805/j.cnki.jcspe.2023.09.004
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    For a two-stage variable-pitch axial fan, a new type of blade tip structure with suction surface winglets and carve slots was proposed. The aerodynamic performance of the fan before and after modification was simulated by Fluent software, and the noise and vortex changes were obtained by large eddy simulation. The influence of blade tip structure on the performance, internal flow, noise and vortex structure at the blade tip was analyzed. Results show that the total pressure and efficiency of the fan are improved after the installation of the winglet on the suction surface, the best performance is achieved after setting a downstream-slot on the winglet. The leakage vortex and blade tip clearance are the main noise source, and the winglet on the suction surface can effectively reduce the acoustic noise, while the slotted winglet results in the increase of total sound pressure level. Considering both the performance and noise changes, the scheme 2 is the best modification scheme. Under this scheme, the reduced leakage vorticity at the blade tip, the low fan noise and the scattered distribution of vortex structure are observed. The large-scale vortex breaks into small pieces, and the vortex core is far away from the main channel, resulting in smaller blade tip losses.
  • Power Equipment and System
    Calculation Method for Total Calendar Life of Steam Turbine Rotors for Nuclear Power Plant
    SHI Jinyuan, XIE Yuesheng, JIANG Luyi, LI Wangfan, FAN Xuefei
    2023, 43(9): 1132-1142. https://doi.org/10.19805/j.cnki.jcspe.2023.09.005
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    Aimed at steam turbine rotors for nuclear power plant (NPP), a calculation method for the rotor total calendar life under the interaction of high-cycle fatigue and low-cycle fatigue damage mechanisms was proposed. The high-cycle fatigue damage mechanism and calculation method for the high-cycle fatigue crack initiation life, and the low-cycle fatigue damage mechanism and low-cycle fatigue crack initiation life of steam turbine rotors for NPP were introduced. Then, the methods for calculating its high-cycle fatigue crack propagation test constant and high-cycle fatigue crack propagation life, and for calculating its low-cycle fatigue crack propagation test constant and low-cycle fatigue crack propagation life were given. The calculation methods of crack initiation calendar life and crack propagation calendar life under the interaction of high-cycle fatigue and low-cycle fatigue damage mechanisms, and the calculation method for calendar total life of steam turbine rotors for NPP were established. An application example of the calculation and improvement of the total calendar life of a steam turbine low pressure welding rotor for NPP was given. Results show that the total calendar life of a steam turbine low pressure welding rotor for NPP is increased to 74.46 years by the improved design from 55.92 years of the original design, which provides a theoretical basis for the long life design of steam turbine for NPP.
    • New Energy Resources and Energy Storage
  • New Energy Resources and Energy Storage
    Performance Analysis of Supercritical Carbon Dioxide Combined Dry Gas Seal
    WANG Zhi, WU Yuxiao, HAN Xu, CAI Wenkui, MENG Jinxiang
    2023, 43(9): 1143-1150. https://doi.org/10.19805/j.cnki.jcspe.2023.09.006
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    In order to enhance the comprehensive performance of dry gas seal of supercritical carbon dioxide near the critical point, a combined spiral groove consisting of a wide spiral groove and a narrow spiral groove was designed based on the superposition combination principle. Considering the actual gas effect, inertia effect and turbulence effect, the geometric parameters of the combined spiral groove were changed to establish the corresponding mathematical model, so as to calculate the pressure distribution of gas film at the end face. Results show that under the influence of centrifugal effect, inertia effect and viscous pumping, the sealing performance of the combined spiral groove improves with the increase of the groove length and number of grooves, and reduces with the increase of groove depth, spiral angle and gas film thickness. At the groove length of 69 mm, the slot depth of 5 μm, the number of grooves of 12, the helix angle of 15° and the gas film thickness of 2.05 μm, stiffness to leakage ratio of the dry gas seal reaches the maximum, and the comprehensive sealing performance is the best.
  • New Energy Resources and Energy Storage
    Capacity Allocation Optimization on Grid Connected System Consisting of Wind Power, Photovoltaic Power, Pumped Storage and Battery
    LIU Zhong, ZHANG Le, KOU Pangao, ZOU Shuyun
    2023, 43(9): 1151-1159. https://doi.org/10.19805/j.cnki.jcspe.2023.09.007
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    A joint operation system consisting of wind power, photovoltaic power, pumped storage, and battery was constructed, and a capacity allocation optimization method with the lowest cost and the lowest lifecycle carbon emission as optimization objectives was proposed. Based on the real data of the reference region, the optimal capacity allocation scheme of the proposed system was obtained with the fast non-dominated sorting genetic algorithm with elite strategy (NSGA-Ⅱ) and technique for order preference by similarity to ideal solution (TOPSIS). Results show that the studied joint operation system can not only ensure the power supply reliability, but also achieve the effective accommodation of wind and solar power with low costs and carbon emissions. The system has good economic and environmental protection performance, and the effectiveness of the proposed model and method is validated.
    • Digitalization and Intelligentization
  • Digitalization and Intelligentization
    Sensor Fault Signal Classification Based on Visual Information Enhancement for In-service Gas Turbine Control Systems
    YANG Xilian, WANG Yuzhang, YANG Zhipeng, CHENG Kanru, ZHAO Qunfei
    2023, 43(9): 1160-1165. https://doi.org/10.19805/j.cnki.jcspe.2023.09.008
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    One-dimensional time series data was converted into a two-dimensional image through the Graham angle field (GAF), and image feature extraction was completed by using the histogram of the directional gradient, then fault signal classification was completed by using multi-classification support vector machine. Based on the actual operating data of a 9F gas turbine in power plant, five typical fault signals with noise were superimposed on the normal data to verify the effectiveness of the proposed method, and the confusion matrix was used to further visualize the fault classification results. Results show that the proposed method can effectively identify weak and gradient fault signals. The accuracy rate of fault classification is 96.6%, and both the GAF and the Markov transition field (MTF) have high fault classification accuracy.
  • Digitalization and Intelligentization
    Control Strategy of 35 MWth Oxy-combustion Boiler Island Based on Dynamic Simulation
    LIU Weilong, YU Zujue, SUN Heming, RAN Shenming, LI Yu, HU Fan, WANG Peng, LIU Zhaohui
    2023, 43(9): 1166-1173. https://doi.org/10.19805/j.cnki.jcspe.2023.09.009
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    In order to study the operating characteristics of the oxy-combustion unit under different load change rates, a 35 MWth oxy-combustion boiler island dynamic simulation model was established, and a closed-loop control unit for the flue gas side and water side was built. Firstly, the system response characteristics were verified after a 4% step change in fuel quantity. On this basis, the variation of the process parameters under the regulation of the control system were simulated at the load change rate of 2%/min and 5%/min. Results show that the simulation results are in good agreement with the actual operation data, and the control process of this control system is stable and converges quickly. The system is more stable at 2%/min load change rate. To obtain more reasonable output parameters, the load change rate during system operation should be minimized as much as possible
  • Digitalization and Intelligentization
    Research on Replay Attack Detection Method of Steam Generator Liquid Level Control System in Nuclear Power Plant Based on Dynamic Watermark
    WANG Dongfeng, GU He, HUANG Yu, WANG Jiajun
    2023, 43(9): 1174-1180. https://doi.org/10.19805/j.cnki.jcspe.2023.09.010
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    In response to the problem that the conventional DCS of the SG liquid level control system in nuclear power plants has weak ability to prevent replay attacks and does not have effective detection capabilities, an active detection method using dynamic watermarks was used to detect replay attacks, which involved injecting watermark signals into the actuator and detecting watermark information in the state estimator, so as to verify the authenticity of sensor signals. Based on the structural characteristics of the control system, an active detection scheme based on dynamic watermark technology was designed to achieve real-time detection of replay attacks. Results show that the detection scheme can detect the occurrence of replay attacks both theoretically and in numerical simulations.
  • Digitalization and Intelligentization
    Gas Turbine Sensor Fault Diagnosis Method Based on SSA and BiLSTM with Attention Mechanism
    CHENG Kanru, WANG Yuzhang, YANG Zhipeng, YANG Xilian
    2023, 43(9): 1181-1189. https://doi.org/10.19805/j.cnki.jcspe.2023.09.011
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    A sensor fault diagnosis method combining singular spectrum analysis (SSA) and Bi-direction long short-term memory (BiLSTM) deep network based on attention mechanism was proposed. Firstly, the sensor signal was preprocessed using SSA to obtain the trend term and period term of the signal. Secondly, the preprocessed time series were input into the BiLSTM deep network with attention mechanism for training to obtain the classifier model. Finally, the method was trained, verified and tested by using the operation data of a 9F gas turbine. Results show that the diagnostic accuracy of the test set can reach 96.5%, and the proposed method can effectively solve the sensor problem of low fault diagnosis accuracy caused by sparseness and weak amplitude of fault signals.
    • Topic of Wind Power Technology
  • Topic of Wind Power Technology
    Dynamic Response Analysis of Super Large Offshore Wind Turbine Under Current Scour
    SHI Haodong, YAN Yangtian, MA Lu, LI Chun, NIU Kailun
    2023, 43(9): 1190-1197. https://doi.org/10.19805/j.cnki.jcspe.2023.09.012
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    To explore the change of structural dynamic characteristics of wind turbine pile before and after scouring, a 10 MW single-pile offshore wind turbine model was established under soil-structure interaction. The modal analysis of the whole machine and the dynamic response analysis of the wind turbine influenced by the wind and wave were carried out. Results show that with the increase of scour depth, compared with the first order frequency, the second order natural frequency decreases significantly, and the erosion effect has a significant impact on the second order natural frequency. Compared with no scouring, the displacement of the tower top increases by 7.8% and the displacement of the pile foundation increases by 110.5% at the scour depth of 1.28D. Compared with the tower, the scouring effect has a greater impact on the pile foundation. Compared with no scouring, when the scour depth is 1.28D, the peak stress of the pile foundation increases by 14.3% and the peak strain energy increases by 6.7%. The scouring effect makes the accumulation of stress and strain energy more obvious. The impact of the scouring effect on the wind turbine should be fully estimated in the design.
  • Topic of Wind Power Technology
    Research on Aerodynamic Modeling and Control Simulation of Dual-rotor Wind Turbine
    ZHANG Wenguang, LUO Weijian, SUN Jiahao
    2023, 43(9): 1198-1206. https://doi.org/10.19805/j.cnki.jcspe.2023.09.013
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    To study the aerodynamic characteristics and wind energy utilization rate of the dual-rotor wind turbine, the dual-rotor wind turbine model was built based on the NREL 5 MW and WindPACT 1.5 MW wind turbine rotors, and the power optimization control simulation was carried out. Firstly, the aerodynamic, tower shadow effect, drive chain and generator models of the dual-rotor wind turbine were established, and the model was built using Matlab/Simulink. Secondly, based on the free vortex wake (FVW) method, the flow field of the dual-rotor wind turbine was simulated under different wind conditions. Finally, a power control strategy for dual-rotor wind turbine was designed based on fuzzy control and compared with the PID control strategy. The simulation results show that compared with CFD, the absolute error of the relative wind speed of the flow field calculated by FVW is less than 10%, which can rapidly and dynamically calculate the flow field distribution of the dual-rotor wind turbine; compared with different wind conditions, the wind energy utilization rate of the dual-rotor wind turbine can be increased by about 24%; the fuzzy control strategy improves the power dynamic response and suppresses power fluctuations of the dual-rotor wind turbine significantly.
  • Topic of Wind Power Technology
    Temperature Monitoring of Heavy Wind Power Unit Inverters Based on FD-AT-LSTM
    HU Yang, HU Yaozong, CHENG Yi, CHEN Xiugao, DONG Dezhi, SUN Xiaoyan
    2023, 43(9): 1207-1215. https://doi.org/10.19805/j.cnki.jcspe.2023.09.014
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    In order to monitor the condition of wind turbine inverters, a condition monitoring method for large wind turbine inverters based on finite differential regression vector and long short-term memory neural network with attention mechanism was proposed. The minimum mean square error variable step adaptive filtering method was used to perform adaptive filtering on the input and output to eliminate the random noise of the data. The Akachi information criterion was used to determine the dynamic delay order of input and output, and the finite differential regression vector was constructed and the inverter condition monitoring model was established with the finite differential regression vector as the input. And then the monitoring index was calculated according to the model residual and the monitoring index threshold was determined by kernel density estimation. Results show that compared with other machine learning methods, the proposed finite difference neural network model has great improvements in the model evaluation index.This method can be applied to the frequency converter monitoring and early warning in large wind turbines, and has certain industrial application prospects.
  • Topic of Wind Power Technology
    Icing Characteristics of Blades and Deicing Test of Hydrophobic Elastic Coating
    YING Yuxiang, YANG Liujing, JIN Chonghui, LI Ke, LI Yabin, ZHOU Yonggang
    2023, 43(9): 1216-1222. https://doi.org/10.19805/j.cnki.jcspe.2023.09.015
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    In order to investigate the blade icing characteristics, the deicing effect and deicing characteristics of the hydrophobic elastic coating, an experimental wind turbine was built in a wind power plant.The icing characteristics of the wind turbine blades were analyzed using the image method, and the deicing effect of the hydrophobic elastic coating using manual coating and spray gun was compared, as well as the deicing effect of the coating on glaze ice and rime ice. Results show that both rime ice and glaze ice are mainly distributed on the leading edge of the blade. Compared with the rime ice, the glaze ice is distributed in a larger range on the leading edge of the blade. As the rotation radius increases, the amount of ice on the blades increases in a linear relationship. After using the hydrophobic elastic coating, the contact angle of the blade increases by approximately 64%. Thanks to the smooth hydrophobic surface characteristics and microscale deformation ability of the coating, the ice adhesion strength of the blade is reduced by about 93%. When the blade freezes, under the action of periodic tangential force, the ice on the coated blade can be thrown off in time, and the deicing effect of the manual coating is better than that of the sprayed coating. The deicing effect of the coating on glaze ice is better than that of rime ice.
  • Topic of Wind Power Technology
    Research on Characteristics of Three-dimensional Superimposed Wake Model Based on Wind Field Experiments
    ZHANG Shaohai, GAO Xiaoxia, XU Shinai, ZHU Xiaoxun, WANG Yu, WANG Xi
    2023, 43(9): 1223-1229. https://doi.org/10.19805/j.cnki.jcspe.2023.09.016
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    Aiming at the problem that the existing wake model can not completely describe the spatial distribution characteristics of superimposed wake, a three-dimensional superimposed wake model based on double-Gaussian function (3DJGF-M model) was proposed to achieve a more accurate and comprehensive prediction of superimposed wake. Firstly, the wake expansion coefficient of the three-dimensional double-Gaussian full wake model (3DJGF model) was corrected. The coefficient does not need to be determined by many tests and calculations, which can reduce computational cost. Secondly, by introducing the influence of wind shear, the superposition principle of velocity loss was modified. In addition, based on the 3DJGF model, the 3DJGF-M model was derived using the superposition principle considering wind shear. Finally, wind field experiments were carried out with lidars to verify the accuracy of 3DJGF-M model. Results show that the relative error of 3DJGF-M model in predicting the horizontal profiles and vertical profiles of the whole wake region is basically within 5%, and the prediction effect is good. It has great application potential for the layout optimization of wind farms.
  • Topic of Wind Power Technology
    Dynamic Response Analysis of the Semi-submersible Floating Wind-Current Integrated System Under the Combined Action of Wind, Wave and Current Loads
    SHI Zhaobin, YANG Yang, FU Jianbin, FANG Fang
    2023, 43(9): 1230-1237. https://doi.org/10.19805/j.cnki.jcspe.2023.09.017
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    A semi-submersible wind-current integrated system composed of the DTU 10 MW wind turbine, OO-Star semi-submersible platform, and a 550 kW tidal turbines was studied.The unsteady aerodynamic and hydrodynamic load prediction model of the wind and tidal turbines was developed based on the blade element momentum theory and the generalized dynamic wake model. The fully coupled aero-hydro-servo-elastic simulation model for the floating wind-current integrated system was built through the secondary development of AQWA using a dynamic link library (user_force64.dll). The effects of the number of tidal turbines on the platform motion, mooring tension, and total system power under the combined effects of wind, wave and current loads were studied. Results show that the more power flow generators are installed, the larger the average surge value, and the smaller the average pitch value. The highest decrease in the average pitch value is 68.17%. The maximum tension for the upwind mooring of the integrated wind-current system with three tidal turbines increases by about 34.54%. The proposed model can effectively improve the output power of the system. The power of the system increases by about 15.94% when three tidal turbines are installed.
  • Topic of Wind Power Technology
    Optimization of Power Distribution for Primary Frequency Regulation of Wind Farm Based on Rotor Kinetic Energy of Wind Turbines
    LI Xiang, LIU Ketian, LI Jun, HU Xinyu
    2023, 43(9): 1238-1246. https://doi.org/10.19805/j.cnki.jcspe.2023.09.018
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    In order to realize the transition of frequency control strategy of wind turbines from the operating characteristics of wind turbines themselves to wind farm, an optimization model was constructed for the power distribution of the primary frequency regulation of wind farm which based on the rotor kinetic energy of wind turbines. Firstly, the wind farm single machine equivalent model was constructed based on the rotor kinetic energy of wind turbines; secondly, based on the single machine equivalent model, the optimal control parameters of wind farm during the frequency regulation were solved; then the wind farm power distribution optimization model was constructed taking into account the different operating conditions of wind turbines, and the power distribution coefficients of each wind turbine during the frequency regulation were solved; finally, the effectiveness of the optimization model was verified by simulation examples. Results show that this method can accurately control the change of rotor kinetic energy during the frequency regulation of wind farm, and the errors are within the permissible range of engineering applications, which has good practicality.