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An Identification Method for DC-Link Capacitor Capacitance of Grid Connected Inverter ZHU Chenghao, WANG Han, SUN Guoqi, WEI Xiaobin, WANG Fuwen, CAI Xu Journal of Shanghai Jiao Tong University    2022, 56 (6): 693-700.   DOI: 10.16183/j.cnki.jsjtu.2021.515 Abstract （1019）   HTML （1284）    PDF（pc） （5050KB）（1217）       Knowledge map    Save DC-link for the capacitor is one of the most vulnerable components of the grid connected converter, whose capacitance identification will help to improve the system reliability by finding and replacing the aging capacitor in time. An identification method for the DC-link capacitor capacitance of the grid connected inverter based on pre-charging circuit is proposed. By analyzing the relationship between the capacitance and the charging current, charging voltage during pre-charging process, and combining the historical operating data, the set of capacitance state feature vector is built. The support vector regression (SVR) model is trained and the regression prediction relationship between the state value and the capacitance is set. The model is optimized by using the particle swarm optimization (PSO) algorithm, which can be used for capacitance identification of the DC-link capacitor. Simulation and experiments results show that the proposed method can implement the accurate capacitance identification of the DC-link capacitor of the grid connected inverter, with an identification error of less than 0.95%. This method does not need to add hardware circuit and change the control algorithm, and has a certain practical value. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Challenges of Distributed Green Energy Carbon Trading Mechanism and Carbon Data Management LI Xingzhi, HAN Bei, LI Guojie, WANG Keyou, XU Jin Journal of Shanghai Jiao Tong University    2022, 56 (8): 977-993.   DOI: 10.16183/j.cnki.jsjtu.2021.450 Abstract （990）   HTML （893）    PDF（pc） （2604KB）（1157）       Knowledge map    Save To achieve the double carbon goal of “carbon peaking and carbon neutrality”, the construction of the power system which is based on the green energy needs to be accelerated. With the growth of the system scale, the distributed green energy carbon trading mechanism and the carbon data management technology based on the blockchain technology can effectively encourage the development of green energy and become effective means for the implementation of low-carbon electricity. The accurate and real-time carbon emission calculation will further provide data support for the accuracy and security of carbon trading information. First, the current research status of green certificate trading and carbon asset management is introduced. Next, the adaptability analysis of the key technologies of the blockchain technology in the four directions of green electricity traceability, green certificate trading, carbon trading, and joint market of green certificate and carbon assets is performed. Afterwords, the specific mathematical models of carbon emission calculation is studied, and the data availability of carbon source traceability methods applicable to the blockchain architecture are discussed. Finally, some suggestions for the future development of carbon emission flow analysis are proposed. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Multi-Objective Optimization Strategy of Trajectory Planning for Unmanned Aerial Vehicles Considering Constraints of Safe Flight Corridors HUANG Yuhao, HAN Chao, ZHAO Minghui, DU Qiankun, WANG Shigang Journal of Shanghai Jiao Tong University    2022, 56 (8): 1024-1033.   DOI: 10.16183/j.cnki.jsjtu.2021.154 Abstract （770）   HTML （41）    PDF（pc） （5684KB）（1052）       Knowledge map    Save Aimed at the problem of generating a smooth, safe, and dynamically feasible continuous-time trajectory for unmanned aerial vehicles (UAV) in complex environments, a trajectory planning algorithm is proposed to minimize a multi-objective function based on safe flight corridors. The safe flight corridor represented by a collection of convex polyhedra is built based on the initial discrete waypoints generated by the improved rapidly-exploring random tree(RRT), namely the RRT* algorithm. The safety objective function is established according to the constraints of limiting the trajectory inside safe flight corridors. In combination with the flight smoothness, dynamic characteristics, and time performance, a multi-objective function is built. The gradient-based convex optimization algorithm is used to derive the continuous-time trajectory expressed as a piece-wise polynomial by optimizing the position, velocity, acceleration of waypoints, and time allocation. The effectiveness and performance of the proposed algorithm is tested and compared under complex environments such as the coal mine. The test results demonstrate that the proposed algorithm has a better comprehensive performance in comparison with existing algorithms. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Circulation Control of Airfoil Aerodynamic Force Under Ground Effect of Wavy Wall LIU Hao, SUN Jianhong, SUN Zhi, TAO Yang, WANG Dechen, LIU Guangyuan Journal of Shanghai Jiao Tong University    2022, 56 (8): 1101-1110.   DOI: 10.16183/j.cnki.jsjtu.2021.384 Abstract （589）   HTML （34）    PDF（pc） （3280KB）（917）       Knowledge map    Save The interaction of airflow and sea waves seriously affects the flight stability and cruising safety of ground effect vehicles. The influence of different sea states and different angles of attack were analyzed numerically on the aerodynamic characteristics of the airfoil under ground effect of wavy wall. The influence of the constant blowing and periodic blowing methods was further studied on the aerodynamic force of the airfoil under ground effect. The simulation results show that the lift coefficient of the airfoil changes periodically with the wave under the wavy ground wall. The amplitude of the lift coefficient fluctuation is larger with the increasing of wave height and angle of attack, or the decreasing of wavelength. Applying the circulation control method for periodic blowing in the same period as the relative motion of the waves can effectively weaken the fluctuation of the airfoil lift coefficient under wavy sea conditions and improve the flight stability and safety of ground effect vehicles. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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An Admittance Reshaping Strategy of Three-Phase LCL Grid-Connected Inverter Based on Modified Passive Control WANG Han, ZHANG Jianwen, SHI Gang, ZHU Miao, CAI Xu Journal of Shanghai Jiao Tong University    2023, 57 (9): 1105-1113.   DOI: 10.16183/j.cnki.jsjtu.2022.120 Abstract （277）   HTML （32）    PDF（pc） （3313KB）（844）       Knowledge map    Save The passivity-based control (PBC) based on energy function has been studied for grid-connected converters to achieve a better performance. However, traditional PBC method relies on the accurate mathematical model of grid-connected inverter. In previous studies on PBC, the effect of digital control delay is rarely considered and the stability under grid impedance uncertainties is not discussed, especially in the capacitive grid or complex weak grid. To address these issues, this paper proposes an improved PBC method to reshape the output admittance for LCL-filtered grid-connected inverters. The system passive region is expanded up to the Nyquist frequency by adding a capacitor current feedback loop which can achieve active damping control of LCL resonant frequency under the wide range of grid impedance changes. The parameter design method is also presented for the proposed PBC control. To verify the correctness of the theoretical analysis, both simulation and experiments are conducted on a 3 kW grid-connected inverter prototype. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Ultra-Short-Term Load Forecasting of Electric Vehicle Charging Stations Based on Ensemble Learning LI Hengjie, ZHU Jianghao, FU Xiaofei, FANG Chen, LIANG Daming, ZHOU Yun Journal of Shanghai Jiao Tong University    2022, 56 (8): 1004-1013.   DOI: 10.16183/j.cnki.jsjtu.2021.486 Abstract （1043）   HTML （396）    PDF（pc） （3182KB）（788）       Knowledge map    Save Accurate electric vehicle load forecasting is the basis for maintaining the safe and economical operation of charging stations, and for supporting the planning and decision-making of new and expanded charging infrastructure. In order to improve the accuracy of the ultra-short-term load forecasting of charging stations, an ultra-short-term load forecasting method based on ensemble learning is proposed. First, aimed at the prediction accuracy and the response speed, the light gradient boosting machine (LightGBM) framework is utilized to build several basic regressors. Next, the basic regressors are integrated by using the adaptive boosting (Adaboost) method. Finally, by using hyperparameter adjustment and optimization, a dual-system for ultra-short-term load forecasting of charging stations named energy ensemble boosting-light gradient boosting machine (EEB-LGBM) is generated. The analysis of the numerical examples shows that the proposed model has a higher accuracy than the back propagation neural network (BPNN), convolutional neural networks-long short term memory (CNN-LSTM), autoregressive integrated moving average (ARIMA), and other load forecasting methods, which can greatly reduce the training time and the computing power requirements of the training platform. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Intelligent Global Sensitivity Analysis Based on Deep Learning WU Shuchen, QI Zongfeng, LI Jianxun Journal of Shanghai Jiao Tong University    2022, 56 (7): 840-849.   DOI: 10.16183/j.cnki.jsjtu.2021.191 Abstract （960）   HTML （48）    PDF（pc） （1418KB）（786）       Knowledge map    Save This paper proposes an end-to-end method that combines deep learning and sensitivity analysis, which can perform gradient back propagation calculation sensitivity on the saved weight information while training the model. The structure and activation function of the depth model are specially designed to adapt to the subsequent sensitivity calculation. The experimental results conducted on a Boston house prices dataset, a track information fusion dataset, and the G function show that the proposed method is more accurate than classical methods such as Sobol’ method when the parameter distribution is uneven, and has a stronger robustness. Compared with the traditional neural network method, the accuracy of the proposed method is higher. The experiment proves that the sample parameter sensitivity obtained by the deep learning model can be used to optimize the model output. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Wind-Solar-Electric Vehicles Coordination Scheduling Method for High Proportion New Energy Grid-Connected Scenarios LI Linyan, HAN Shuang, QIAO Yanhui, LI Li, LIU Yongqian, YAN Jie, LIU Haidong Journal of Shanghai Jiao Tong University    2022, 56 (5): 554-563.   DOI: 10.16183/j.cnki.jsjtu.2022.040 Abstract （845）   HTML （396）    PDF（pc） （1648KB）（784）       Knowledge map    Save Wind-solar-electric vehicles coordinated optimization scheduling can effectively reduce the adverse effects of multiple uncertainties of wind-solar output and disorderly charging of electric vehicles on the power system. Most of the existing optimization scheduling models take the minimum equivalent load fluctuation as the optimization objective, which, only considering the overall fluctuation of equivalent load, cannot measure the matching degree of output-load, and do not consider the difference of output in different output scenarios. Therefore, a wind-solar-electric vehicles coordination scheduling method for high proportion new energy grid-connected scenarios is proposed. First, the disordered charging model of electric vehicles by Monte Carlo simulation is constructed. Then, a wind-solar output typical day classification model using Gap statistical and K-means++ is constructed based on the forecasting data of wind and solar power. Finally, taking the minimum equivalent load variance and load tracking coefficient as the double optimization objectives, a wind-solar-electric vehicles coordination optimization scheduling model is established, and the NSGA-II algorithm is used to solve it. The results demonstrate that the proposed model can effectively improve the matching degree of wind-solar output and load, and reduce the fluctuation of equivalent load, so as to reduce the adverse effects of multiple uncertainties of wind-solar output and disorderly charging of electric vehicles on the power system. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Optimal Planning of Power Systems with Flexible Resources for High Penetrated Renewable Energy Accommodation GUO Yongtao, XIANG Yue, LIU Junyong Journal of Shanghai Jiao Tong University    2023, 57 (9): 1146-1155.   DOI: 10.16183/j.cnki.jsjtu.2022.269 Abstract （171）   HTML （11）    PDF（pc） （2433KB）（773）       Knowledge map    Save High penetrated renewable energy has brought great challenges to the flexibility of the power system due to its volatility and intermittency. To improve the capacity of renewable energy accommodation, the flexibility reformation of thermal power units, the construction of gas-fired units, and the electrical energy storage installation are considered as effective solutions. Thus, an optimization model for power system planning scheme considering multi-type flexible resources with their different output characteristics is established. The simulation results on a modified IEEE 24-bus power system and 12-node natural gas system demonstrate the effectiveness of the proposed model. In addition, the applicability of different flexible resource planning schemes is comprehensively evaluated from the perspectives of economy, accommodation capacity, and carbon reduction, so as to meet the different planning goals. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Dual-System Reinforcement Learning Method for Flexible Job Shop Dynamic Scheduling LIU Yahui, SHEN Xingwang, GU Xinghai, PENG Tao, BAO Jinsong, ZHANG Dan Journal of Shanghai Jiao Tong University    2022, 56 (9): 1262-1275.   DOI: 10.16183/j.cnki.jsjtu.2021.215 Abstract （819）   HTML （70）    PDF（pc） （4009KB）（763）       Knowledge map    Save In the production process of aerospace structural parts, there coexist batch production tasks and research and development (R&D) tasks. Personalized small-batch R&D and production tasks lead to frequent emergency insertion orders. In order to ensure that the task is completed on schedule and to solve the flexible job shop dynamic scheduling problem, this paper takes minimization of equipment average load and total completion time as optimization goals, and proposes a dual-loop deep Q network (DL-DQN) method driven by a perception-cognition dual system. Based on the knowledge graph, the perception system realizes the representation of workshop knowledge and the generation of multi-dimensional information matrix. The cognitive system abstracts the scheduling process into two stages: resource allocation agent and process sequencing agent, corresponding to two optimization goals respectively. The workshop status matrix is designed to describe the problems and constraints. In scheduling decision, action instructions are introduced step by step. Finally, the reward function is designed to realize the evaluation of resource allocation decision and process sequence decision. Application of the proposed method in the aerospace shell processing of an aerospace institute and comparative analysis of different algorithms verify the superiority of the proposed method. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Differentiated Allocation Model of Renewable Energy Green Certificates for New-Type Power System ZHANG Shuo, LI Wei, LI Yingzi, LIU Qiang, ZENG Ming Journal of Shanghai Jiao Tong University    2022, 56 (12): 1561-1571.   DOI: 10.16183/j.cnki.jsjtu.2022.150 Abstract （1299）   HTML （816）    PDF（pc） （1436KB）（743）       Knowledge map    Save In order to achieve China’s “30·60” decarbonization goal, the green and low-carbon transformation of the energy system is the fundamental support; the construction of new-type power system is the key step, and the green certificate is the important voucher to reflect the green value of renewable energy. Currently, the distribution mechanism of green certificates in China is oversimplified, which neither effectively measures the variability of green values generated by different types of renewable energy, nor balances the coordinated development of renewable energy. Therefore, to differentiate the exchange mechanism of green certificates by different types of renewable energy power in this paper, an evaluation index system is established, which describes the difference between green certificates, considering the comprehensive value of renewable energy, and an evaluation model is built with the criteria importance by using the intercriteria correlation (CRITIC) method, the entropy weight method, and the technique for order preference by similarity to an ideal solution (TOPSIS) method. Under the development scenario of peaking carbon emissions before 2030, the impact of the differentiated distribution model on the green incomes of centralized photovoltaic distributed photovoltaic power, onshore wind power, and offshore wind power is analyzed. Moreover, the development plan of renewable energy is modified in consideration of the effect of the differentiated distribution model, and policy suggestions on green certificates are proposed accordingly. The results show that the differentiated distribution model of green certificates is practical to provide corresponding decision-making support to the construction and improvement of green certificates trading mechanism in China. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Voltage and Frequency Suppression of Intentional Islanding Restoration Process for Distribution System with Multi-Generations CHEN Chun, GAO Jing, CAO Yijia, WANG Weiyu, ZHAO Long Journal of Shanghai Jiao Tong University    2022, 56 (5): 543-553.   DOI: 10.16183/j.cnki.jsjtu.2021.418 Abstract （818）   HTML （1031）    PDF（pc） （4975KB）（734）       Knowledge map    Save Intentional islanding restoration of distribution systems with multi-generations is of great importance to ensure the power supply of critical loads under extreme conditions, which is beneficial to improve the reliability of distribution systems. There are transient voltage and frequency fluctuations in the process of intentional islanding restoration, when the loads and distributed generations are gradually connected to the grid. The safety and stability of the intentional islanding are affected by the fluctuations, and networking process may fail in serious cases. Hence, the rapid power response of the energy storage system is utilized to suppress voltage and frequency fluctuations. A fluctuation suppression model based on energy storage system control is established, where a voltage and current double-loop feed-forward disturbance compensation control system is designed. A vector control method for energy storage system with improved dual-loop control is proposed, which solves the problems of traditional V/f control voltage offset and excessive voltage fluctuation. MATLAB/Simulink is used to build simulation models in different control modes in accordance with the black-start principle. The simulation results show that the improved double-loop control based on the vector method has a stronger anti-interference ability and significantly improved the islanding black-start self-organizing networking process. Voltage and frequency fluctuations are reduced, and the dynamic response performance of the system is improved. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Real-Time Calculation of Carbon Emissions in County-Level Administrative Regions Based on ‘Energy Brain’ CHEN Yun, SHEN Hao, WANG Jiayu, ZHAO Wenkai, PAN Zhijun, WANG Xiaohui, XIAO Yinjing Journal of Shanghai Jiao Tong University    2022, 56 (9): 1111-1117.   DOI: 10.16183/j.cnki.jsjtu.2021.364 Abstract （979）   HTML （782）    PDF（pc） （851KB）（724）       Knowledge map    Save Existing calculation methods of carbon emission cannot well meet the needs of gradual refinement and real-time of carbon emission regions. In order to ensure the real-time and accuracy of carbon emissions responsibility allocation, a real-time calculation method of carbon emissions in urban regions is proposed. The improved K-means clustering algorithm is used to cluster and combine the operating periods and operating scenarios of the urban area energy load,so as to obtain the typical carbon emission characteristics. The regional unit electricity carbon emission is proposed as a carbon emission indicator, the operating period and scenario are classified, and the unit electricity carbon emission and the total carbon emission of urban regions for each cluster are calculated. The proposed algorithm is verified based on part of the historical data of energy consumption in the energy brain of a certain region in eastern China. The results show that the clustering method and carbon emission indicators can effectively calculate the total carbon emission of urban regions in real-time. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Radar Signal Recognition Based on Dual Channel Convolutional Neural Network QUAN Daying, CHEN Yun, TANG Zeyu, LI Shitong, WANG Xiaofeng, JIN Xiaoping Journal of Shanghai Jiao Tong University    2022, 56 (7): 877-885.   DOI: 10.16183/j.cnki.jsjtu.2021.209 Abstract （849）   HTML （28）    PDF（pc） （4098KB）（723）       Knowledge map    Save In order to solve the problems of difficult feature extraction and low recognition rate of radar signal at low signal-to-noise ratios, a dual channel convolutional neural network model based on Choi-Williams distribution (CWD) and multisynchrosqueezing transform (MSST) is proposed, which obtains two-dimensional time-frequency images by CWD and MSST time-frequency analyses on radar signals. Respectively, the time-frequency images are preprocessed and sequencely fed to a dual channel convolutional neural network for deep feature extraction. Finally, the features acquired by the two channels are fused, and the radar signal is classified and recognized through the convolutional neural network classifier. The simulation results show that when the signal-to-noise ratio is -10 dB, the overall recognition accuracy can reach above 96%, which is excellent at low signal-to-noise ratios. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Mechanism of Forced Subsynchronous Oscillation of Large-Scale Photovoltaic Power Generation Grid-Connected System with Series Compensation Tranmmission Lines LIN Yong, KANG Jiale, YU Hao, CHEN Honglin, YANG Yanji, CHEN Wuhui Journal of Shanghai Jiao Tong University    2022, 56 (9): 1118-1127.   DOI: 10.16183/j.cnki.jsjtu.2021.415 Abstract （666）   HTML （132）    PDF（pc） （1463KB）（714）       Knowledge map    Save There exists the subsynchronous oscillation (SSO) instability risk in large-scale photovoltaic(PV) grid-connected systems with series compensation, which is generally explained by the negative damped oscillation theory. In this paper, the inter-photovoltaic harmonics due to maximum power point tracking (MPPT) control are used as the disturbance source and the large-scale PV grid-connected system with series compensation as the forced system. The forced oscillation theory is used to reveal the SSO mechanism of PV power generation based on the interaction between the perturbed MPPT and the series compensation grid-connected system, and verified in the PSCAD/EMTDC simulation platform. The results show that the perturbed MPPT-based PV inverter outputs interharmonic currents to the system due to the modulation coupling on the AC-DC side, which may lead to serious forced SSO problems when the interharmonic frequency is close to the frequency of inherent weakly damped mode of the system, causing a shock to the system stability. The simulation results verify the correctness of the proposed theory. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Inertial Control Strategy for Wind Farm with Distributed Energy Storage System Based on Model Predictive Control SHEN Yangwu, SONG Xingrong, LUO Ziren, SHEN Feifan, HUANG Sheng Journal of Shanghai Jiao Tong University    2022, 56 (10): 1285-1293.   DOI: 10.16183/j.cnki.jsjtu.2022.134 Abstract （873）   HTML （1098）    PDF（pc） （1641KB）（710）       Knowledge map    Save Distributed energy storage (DES) wind turbine is an effective means to solve the problem of system frequency stability caused by large-scale wind power connection. In this paper, an inertial control method for DES wind farms based on model predictive control (MPC) is proposed.First, the linearized prediction model of the DES wind farm is established. Then, on this basis, in combination with the control framework of MPC, an optimization model and strategy of MPC inertial control are proposed considering the cost of energy storage loss and the balanced change of wind turbine rotor speed,in order to achieve the balanced change of wind turbine rotor speed during inertia control. The simulation results show that the proposed control strategy can effectively coordinate the active power output of the wind power generation unit and the energy storage system unit in the DES wind turbine, reduce the cost of charging and discharging loss of the energy storage system, and ensure that the rotational speed of all wind turbines in the wind farm tends to be average during the inertial control period, avoiding the problem of wind turbines exiting frequency regulation due to excessive reduction of the rotational speed of wind turbines. The inertial control strategy of the DES wind farm is beneficial to improve the frequency stability of the power grid, which is of great significance to ensure the safe operation of the power grid. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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An LC Inverter Based on Novel Dual-Loop Control LI Shuang, SHI Jianqiang Journal of Shanghai Jiao Tong University    2022, 56 (9): 1139-1147.   DOI: 10.16183/j.cnki.jsjtu.2021.275 Abstract （868）   HTML （129）    PDF（pc） （1553KB）（707）       Knowledge map    Save To improve the voltage tracking and anti-disturbance performance of the LC inverter, a novel voltage-current dual-loop control strategy is proposed. First, the voltage loop is tuned to first-order inertia link by zero-pole cancellation based on virtual resistance, which restrains the overshoot during voltage tracking. Next, the hypo-time-optimal current-loop is adopted to enhance the response speed of the current loop, which suppresses the sudden change of transient voltage. Finally, the cause of overshoot during the voltage recovery period is analyzed and the overshoot is eliminated by the adaptive integrator initial value, which modifies the voltage waveform distortion under loading disturbance. Based on the traditional double-loop control, the voltage loop and the current loop are improved respectively by the proposed novel control strategy, which overcomes the shortcomings of step response and anti-load disturbance performance. The feasibility and effectiveness of this method are validated through simulations on MATLAB/Simulink. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Real-Time Detection of Insulator Drop String Based on UAV Aerial Photography LI Dengpan, REN Xiaoming, YAN Nannan Journal of Shanghai Jiao Tong University    2022, 56 (8): 994-1003.   DOI: 10.16183/j.cnki.jsjtu.2021.416 Abstract （723）   HTML （396）    PDF（pc） （28565KB）（704）       Knowledge map    Save It is of great significance for unmanned aerial vehicle(UAV) to replace manual inspection of power insulators. Aimed at the problem of limited computing power and storage resources of the UAV, an improved real-time target detection algorithm suitable for insulator drop string failure detection is proposed. Based on the YOLOv5s detection network, first, the PANet networks in neck are replaced with bi-directional feature pyramid network(BiFPN) to improve the feature fusion ability. Next, DIoU is used to optimize the loss function to optimize the model. The channel pruning and fine tuning of the γ coefficient generally improve the accuracy, speed, and deployment ability of the detection network. Finally, the image is enhanced at the network output to improve the availability of the algorithm. The proposed algorithm is tested under a specially expanded insulator fault data set. The results show that compared with the original YOLOv5s algorithm, the average accuracy of the proposed algorithm is improved by 3.91%, the detection speed is improved by 25.6%, and the model volume is reduced by 59.1%. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Application of Plane Elements and Shell Elements in Imitating Ribs of Members in Compound Strip Method HOU Yanguo, LI Zhanjie, GONG Jinghai Journal of Shanghai Jiao Tong University    2022, 56 (6): 710-721.   DOI: 10.16183/j.cnki.jsjtu.2021.071 Abstract （820）   HTML （448）    PDF（pc） （10465KB）（694）       Knowledge map    Save Finite strip method (FSM) is a classical method to analyze the buckling of thin-walled members. The traditional FSM adopting trigonometric functions longitudinally can hardly analyze the members with spaced ribs along the longitudinal direction, while the compound strip method (CSM) can compensate for this shortcoming. Based on the CSM, the influence of utilizing plane elements and shell elements to respectively imitate stiffeners on buckling is investigated. Compared with the shell-element ribs, the plane-element ribs are prone to assembling the stiffener matrices with fewer degrees of freedom. But the shell-element ribs are more comprehensive as the out-plane displacement of ribs are taken into consideration. It is found that plane element ribs and shell element ribs have little difference on the buckling capacity of members. The buckling capacity has a small difference of mean absolute error (MAE) underneath 0.75% between the two types of CSMs, and the buckling capacity and modes are in good agreement with the finite element results. The buckling loads of the two types of CSMs are close to the FEM with a MEA less than 5%. The accuracy of the plane elements satisfies the predicted requirements, which helps to reduce the program computation and simplify the analysis complexity. The efficiency of analysis can be dramatically improved for fine meshing elements. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Novel Prediction Model for Fatigue Strength DUAN Hongyan, TANG Guoxin, SHENG Jie, CAO Mengjie, PEI Lei, TIAN Hongwei Journal of Shanghai Jiao Tong University    2022, 56 (6): 801-808.   DOI: 10.16183/j.cnki.jsjtu.2021.051 Abstract （1045）   HTML （123）    PDF（pc） （1208KB）（688）       Knowledge map    Save Fatigue failure is one of the most important reasons for the failure of engineering application components. However, due to the high cost of fatigue experiments, it is necessary to use mechanical properties to predict fatigue strength. Based on the true stress-strain curves, a novel model for fatigue strength prediction is established and is used to calculate the fatigue strength. The strength predicted is compared with that calculated by the staircase method and the Basquin equation. The results show that the model could obtain the fatigue strength of the materials only by using tensile strength and work-hardening strength, and it is suitable for other steels, which greatly saves costs and increases accuracy. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Experiment on Wedge-Shaped Latticework Channel Cooling Applied in Aero Engine Gas Turbine Blade Trailing Edge XIAO Kehua, LUO Jiahao, RAO Yu Journal of Shanghai Jiao Tong University    2022, 56 (8): 1034-1042.   DOI: 10.16183/j.cnki.jsjtu.2021.162 Abstract （626）   HTML （33）    PDF（pc） （20093KB）（686）       Knowledge map    Save In order to study the flow and heat transfer performance of wedge-shaped latticework channels in the turbine blade trailing edge, this paper conducted an experimental study by employing the transient liquid crystal (TLC) technique to investigate the local heat transfer characteristics of the upper and lower main surfaces and applying the pressure scanning valve to mesure the pressure loss of the channels at different Reynolds numbers. The experiment shows that there is a significant difference between the upper and lower main surfaces under the turning flow configuration condition at the trailing edge section. The average Nusselt number of the lower main surface is over 30% higher than that of the upper main surface. In heat transfer coefficient, the wedge-shaped latticework channel is over 46% higher than that of the needle rib channel. There is a strong mass exchange at the interface between the upper and lower channels of the latticework channel. The intermittent high heat transfer areas on the upper and lower main surfaces are corresponding to the interface. As the inlet Reynolds number increases, the channel pressure drop increases rapidly. The pressure drop of the wedge-shaped latticework channel is 5 to 7 times that of the needle ribs, but the heat transfer area of latticework channel is 107.4% higher than the needle ribs channel, and the overall thermal performance of the wedge-shaped latticework channel is still approximately 66% higher than that of the needle ribs channel. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Cryogenic Minimal Quantity Lubrication Assisted Cutting Process for Polyimide Materials CAO Zheng, LEI Xuelin, ZHANG Hang, CAI Xiaojiang Journal of Shanghai Jiao Tong University    2022, 56 (6): 784-793.   DOI: 10.16183/j.cnki.jsjtu.2021.173 Abstract （816）   HTML （21）    PDF（pc） （21845KB）（650）       Knowledge map    Save The cutting performance of the porous polyimide material assisted by cold air trace lubrication was investigated, and the influence law of cutting process parameters on the cutting effect (cutting force, surface finish quality, and oil content) of the porous material was explored. The results show that compared with dry cutting and low-temperature cold air cutting, the cutting temperature and the machined surface roughness of cold air micro-lubrication cutting are the lowest, and the damage to the porous runner is the smallest. The depth of cut and the feed volume are the factors that have the greatest influence on milling force and surface roughness, respectively. Defects such as chip burrs and tears are the main factors that lead to the increase in surface roughness. The existence of drawing, micro-crack, stacking, and tiny debris on the workpiece surface are the main causes for the decrease in the oil content and oil delivery rate of the material. The optimal machining parameters of the porous polyimide material in the orthogonal experiment with the aid of cold air trace lubrication are vc=(100±2) mm/min, fz=(0.3±0.01) mm/r, ap=(0.8±0.1) mm (vc is the cutting speed, fz is the feeding rate, and ap is the cutting depth). With the assist of the cryogenic minimal quantity lubrication technology, the low damage processing, high oil content, and high oil delivery rate of cage products can be obtained. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Linear Parameter-Varying Integrated Control Law Design for a Hypersonic Vehicle YANG Shu, QIAN Yunxiao, YANG Ting Journal of Shanghai Jiao Tong University    2022, 56 (11): 1427-1437.   DOI: 10.16183/j.cnki.jsjtu.2022.190 Abstract （900）   HTML （352）    PDF（pc） （2903KB）（643）       Knowledge map    Save A linear parameter-varying (LPV) integrated control law is designed for a hypersonic vehicle to achieve trajectory control based on an altitude-horizontal trajectory control concept. The LPV output-feedback control theory and pole placement techniques are employed to design parameters of the control law within a Mach number envelope. Such a control law performs integrated control for longitudinal and lateral-directional dynamics of the vehicle, free from the scheme of inner and outer control loops of classical flight controls and ensuring robust and optimal control performance in the sense of L2-induced norm. A mathematical model of the hypersonic vehicle is developed in the Earth-centered-Earth-fixed reference frame. Earth rotation, Earth oblateness, and the second order harmonic perturbations of Earth are considered in the model. Numerical simulations are conducted to examine the performance of the LPV controller. The simulation results indicate that the closed-loop system of the hypersonic vehicle achieves D-stability. The LPV control law achieves a good performance in vehicle trajectory control and has sufficient robustness with respect to perturbations and sensor noise. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Frequency Control Strategy for Interconnected Power Systems with Time Delay Considering Optimal Energy Storage Regulation FU Yang, DING Zhiyin, MI Yang Journal of Shanghai Jiao Tong University    2022, 56 (9): 1128-1138.   DOI: 10.16183/j.cnki.jsjtu.2022.145 Abstract （733）   HTML （128）    PDF（pc） （3139KB）（643）       Knowledge map    Save Aimed at the problem of large frequency deviation caused by the source load uncertainty and the communication delay in the interconnected power system, a frequency control strategy for interconnected power systems with time-delay considering energy storage regulation is proposed. An interconnected power grid model with time delay which includes a steam turbine generator, a wind turbine generator, and energy storage equipment is established. According to the area control error (ACE), the energy storage device coordinates the steam turbine generator to participate in the frequency control, and the modified particle swarm optimization (MPSO) algorithm is used to optimize the proportional integral derivative (PID) load frequency controller to realize the secondary frequency adjustment, which improves the frequency stability of the load frequency control (LFC) system in a certain time-delay interval. A fractional order PID (FOPID) controller is designed for the energy storage device to adjust the output power and smooth the source load fluctuation. The frequency control performance of the energy storage system is improved to further control the frequency deviation of the interconnected power system. Different working conditions are compared and analyzed on the MATLAB/Simulink platform to verify the effectiveness of the proposed frequency control strategy. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Design and Realization of Continuum Manipulator Based on Coupling of Double Parallel Mechanism WU Guanlun, SHI Guanglin Journal of Shanghai Jiao Tong University    2022, 56 (6): 809-817.   DOI: 10.16183/j.cnki.jsjtu.2021.060 Abstract （769）   HTML （38）    PDF（pc） （14846KB）（640）       Knowledge map    Save A 5-degree-of-freedom continuum manipulator is designed and implemented to improve the flexible positioning ability of the continuum mechanism in applications such as interactivity operations, light object grabbing, and human-machine collaboration. In the design process, by introducing a two-segment constant curvature model, the distribution of degrees of freedom on the mechanism is explained geometrically by the method of twist. Coupling two stretchable parallel modules in series, a two-segment structure is formed for curving and each segment has two degrees of freedom in bending and one degree of freedom in stretching, thereby giving 5 degrees of freedom to the end-effector. Concentrating on the dynamic performance of the manipulator, an electromechanical system platform is built as a prototype. The experiments show that the structure realizes the control of the end-effector during large deformation of the manipulator, and is able to achieve extreme pose in 2 s with an approximation positioning error of 2% of the nominal arm length. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Off-Axis Tensile Test and Numerical Simulation of Unidirectional Thermoplastic Composite Laminates ZHANG Jian, CHEN Xiuhua, CHEN Yong, FANG Yin Journal of Shanghai Jiao Tong University    2023, 57 (2): 201-212.   DOI: 10.16183/j.cnki.jsjtu.2021.352 Abstract （457）   HTML （98）    PDF（pc） （13908KB）（623）       Knowledge map    Save As a high-performance thermoplastic composite material, AS4/PEEK has been widely used in aerospace, military, automotive, and other fields. After conducting the off-axial tensile test of unidirectional AS4/PEEK laminates with different angles, the relevant stress-strain curves and tensile strengths, as well as fracture plane angles are obtained. In simulation, a 3D elastic-plastic model where the parameters are determined by trust-region reflective algorithm is used to describe the nonlinear mechanical behavior of AS4/PEEK laminates. In combination with the LaRC05 criterion and the crack zone theory, a user material subroutine VUMAT based on Abaqus is developed and applied to the numerical simulation of off-axis tensile test. The numerical results show that the 3D elastic-plastic damage constitutive model can accurately simulate the plastic effect of AS4/PEEK laminates and the tensile strength predicted by the numerical method agrees well with those from the test. The proposed 3D elastic-plastic damage model provides an accurate and effective method for the comprehensive analysis of plastic deformation and damage of thermoplastic composites. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Shared Energy Storage Optimal Operation Method Considering the Risk of Probabilistic Voltage Unbalance Factor Limit Violation FANG Xiaotao, YAN Zheng, WANG Han, XU Xiaoyuan, CHEN Yue Journal of Shanghai Jiao Tong University    2022, 56 (7): 827-839.   DOI: 10.16183/j.cnki.jsjtu.2021.455 Abstract （892）   HTML （605）    PDF（pc） （1838KB）（618）       Knowledge map    Save The distributed access with single-phase and uncertain generation of the renewable energy increase the risk of voltage unbalance limit violation in the distribution network. With the increasing penetration rate of the renewable energy generation, it is important to study the mitigation of the impacts of intermittent renewable energy generation on the risk of voltage unbalance limit violation in the distribution network. A shared energy storage allocation strategy and optimal operation method based on global sensitivity analysis (GSA) is proposed. First, a back propagation neural network (BPNN) based probabilistic voltage unbalance factor calculation model for the distribution network is constructed, and the risk index of the distribution network probabilistic voltage unbalance factor limit violation is defined, which can quickly and accurately quantify the impact of uncertain renewable energy generation on the risk of voltage unbalance limit violation in the distribution network. Then, a GSA method based on Wasserstein distance is proposed to identify the critical renewable energy sources affecting the distribution network voltage unbalance. Finally, the GSA-based shared energy storage allocation strategy and the rolling prediction optimization-based operation method of the shared energy storage are proposed. The effectiveness of the proposed method is verified through the simulation analysis of IEEE 123-bus distribution network. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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An Image Self-Calibration Method Based on Parallel Laser Ranging CHENG Bin, HUANG Bin, LI Derui Journal of Shanghai Jiao Tong University    2022, 56 (7): 850-857.   DOI: 10.16183/j.cnki.jsjtu.2021.447 Abstract （724）   HTML （22）    PDF（pc） （3660KB）（616）       Knowledge map    Save Regarding the disadvantages of existing camera calibration methods, such as external information relative, special camera poses,the need for calibration targets, and complex operations, this paper proposes a real-time self-calibration method based on parallel laser ranging by employing high-precision laser rangefinders to synchronously measure the position of the measured object plane when taking pictures, so that the object plane equation can be solved. The 2D coordinates of at least four sets of corresponding points on object plane and image planes are selected to obtain the homography matrix, which represents the mapping relationship between object and image planes, so as to complete the calibration simply and quickly. A calibration device is developed to validate the accuracy of the proposed self-calibration method in different testing scenarios. The results show that the measurement error of line segments length in the image are between -0.49% and 0.15%, and the average errors are merely -0.14%, which indicates that the parallel laser ranging self-calibration method proposed in this paper is accurate and robust. The causes of measurement error are further investigated by analyzing the influences of laser ranging, laser inclination, and device offset. The error eliminating suggestions are provided to give references for the application of the proposed self-calibration method in the field of image measurement. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Numerical Method for Transient Tracking of Sediment Particles in Dredge Pump GUO Tao, LIU Mingming, CAO Lei, HU Jingzhao, HONG Guojun, YOU Yunxiang Journal of Shanghai Jiao Tong University    2022, 56 (5): 656-663.   DOI: 10.16183/j.cnki.jsjtu.2020.437 Abstract （698）   HTML （19）    PDF（pc） （14885KB）（615）       Knowledge map    Save In order to transiently solve the transient movement of sediment particles in dredge pumps, a modified algorithm is realized based on the discrete phase model in ANSYS Fluent. The granular phase volume fraction solved by using the Eulerian (granular)-Eulerian (liquid) two phases flow method and the Huilin-Gidaspow drag force laws are introduced for tracking particles with the Lagrangian method in dense flow. The solution process that solves particle motion after updating the impeller grid is changed to a process that solves particle relative motion after rotating synchronously the impeller grid with the particles. Under the situations of moving wall, the modified algorithm avoids the calculation error on collision identification and rebounded velocity of the particles. A comparison of numerical results shows that the modified algorithm can significantly improve the accuracy of particle motions in the dredge pump with similar time cost. The erosive wear predicted by the modified algorithm mainly appears on the front edges of the blades and the peak of erosion rate is about 7×10-5 kg/(m2∙s), which is similar to the actual situations, supporting the effectiveness of the modified algorithm. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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“Window Effect” and Protective Measures of Exogenous Pulsed Electromagnetic Field on Implantable Cardiac Pacemaker LU Wu, DING Ranran, ZHAO Wenbin, HUANG Dong, WANG Zheming Journal of Shanghai Jiao Tong University    2022, 56 (11): 1518-1531.   DOI: 10.16183/j.cnki.jsjtu.2021.326 Abstract （839）   HTML （11）    PDF（pc） （24935KB）（598）       Knowledge map    Save The electromagnetic interference (EMI) from pulsed electromagnetic field (PEMF) on pacemakers is unignorable in modern power grids and healthcare environments, but there is limited study on the interaction mechanisms and protective measures. In this paper, an in-vitro human chest model for pacemaker implantation is made by using pork tissues immersed in 0.9% sodium chloride solution. The effect of PEMFs generated by the switching actions of common electrical equipment and low-frequency medical equipment on pacemakers is simulated by using fast-front current sources. The pulse forming line theory is employed for analyzing the waveform compression of PEMFs in human thoracic cavity. Further, the parameterized bio-electromagnetic transient model of pacemaker in combination with biological tissues is established in finite element software. The results show that pacemaker malfunctions including pacing inhibition and P pulmonale occur under PEMF. The “Window effect” in subcutaneous pouch under PEMF is found by changing the winding of pacemaker leads in the pouch. Based on the research finding, a protective strategy by using composite materials to shield the window area is proposed. The theoretical feasibility of this protective measure is confirmed by simulation, where the intensity of pacemaker EMI could be reduced by 80 dB when the composite materials shielding is used. Finally, a safe distance is developed for pacemaker wearers in electrical and medical environments. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Aerodynamic Drag Characteristics of Ultra-Low Orbit Satellites WANG Xiaoliang, YAO Xiaosong, GAO Shuang, LIU Guohua Journal of Shanghai Jiao Tong University    2022, 56 (8): 1089-1100.   DOI: 10.16183/j.cnki.jsjtu.2021.014 Abstract （649）   HTML （26）    PDF（pc） （7210KB）（598）       Knowledge map    Save Taking the 180~300 km ultra-low orbit satellite as the research object, the aerodynamic drag characteristics of the typical shapes were studied by using the direct simulation Monte Carlo (DSMC) method in the free molecular flow simulation method, which can accurately simulate the three-dimensional complex shapes. By comparing the theoretical drag coefficients of spheres and plates at different velocity rates and the aerodynamic experimental data of 70° bluff body shapes at different velocity rates with the DSMC calculation results, the adaptability of the three-dimensional DSMC method to shape and mesh is verified. The drag characteristics of several typical satellite shapes were calculated and compared, and the pressure difference drag, shear drag, total drag and dimensionless drag coefficients with altitude and shape were obtained. The optimized design of the shape of the ultra-low orbit satellite can reduce the drag by about 10%, which can effectively improve its on-orbit operation characteristics and reduce the design requirements of the own related systems of the satellite. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Multiscale Similarity Ensemble Methodology for Remaining Useful Life Prediction in Multiple Fault Modes SHU Junqing, XU Yuhui, XIA Tangbin, PAN Ershun, XI Lifeng Journal of Shanghai Jiao Tong University    2022, 56 (5): 564-575.   DOI: 10.16183/j.cnki.jsjtu.2021.024 Abstract （646）   HTML （28）    PDF（pc） （4306KB）（591）       Knowledge map    Save Traditional similarity-based methods generally ignore the diversity of equipment fault modes, the difference in degradation rates, and the inconsistency among monitoring data lengths. Thus, a similarity-based multi-scale ensemble method in multiple fault modes (MFM-MSEN) is proposed to improve remaining useful life (RUL) prediction accuracy and characterize prediction uncertainty. By training the fault mode classification model, designing the time-series weighted prediction strategy, and recognizing the fault mode of equipment, the test equipment is matched with the training equipment with the same fault mode to reduce matching complexity, based on which, a multi-scale ensemble strategy is proposed to overcome the data utilization limitation caused by single-scale matching methods and enhance the generalization ability of the proposed MFM-MSEN method. This strategy matches the similarities between test equipment and training equipment at multiple time scales, and then multiscale prediction results are integrated to fit accurate RUL probability distribution by employing kernel density estimation. Experimental results demonstrate the superiority of the proposed MFM-MSEN method in dealing with the differences in equipment degradation. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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A Numerical Model for Analysing Response of Membrane Surface Under Ponding Load WANG Shasha, ZHANG Xiangyu, QIU Guozhi, GONG Jinghai Journal of Shanghai Jiao Tong University    2022, 56 (6): 730-738.   DOI: 10.16183/j.cnki.jsjtu.2021.152 Abstract （611）   HTML （23）    PDF（pc） （20233KB）（581）       Knowledge map    Save A numerical model to analyze the response of the membrane surface under ponding load is propesed which combines the smoothed particle hydrodynamics (SPH) method and the non-linear constitutive model of the membrane material. According to the stress-strain response surface of the membrane material based on the biaxial tensile test with different stress ratios, a nonlinear constitutive model is established. SPH particles are used to simulate water, and a numerical model of the fluid-solid coupling between the membrane surface and ponding load is established. The mesh size adopted in this paper is determined by verifying the mesh convergence, and the influence of the loading time on the calculation results is analyzed. At the same time, the distribution law of stress and strain of the membrane surface are analyzed. The results show that the loading process becomes increasingly stable with the increase of the loading time, and 100 s can meet the analysis requirements.The numerical simulation results are compared with those of the flat membrane ponding test. It is found that the maximum vertical deformation of the membrane surface is in good agreement, which verifies the reliability of the method proposed in this paper. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Review of Single Blade Installation and Docking Technology of Large Offshore Wind Turbine XIE Sihong, ZHAO Yongsheng, XU Yiqing, HE Yanping, HAN Zhaolong, XU Yuwang Journal of Shanghai Jiao Tong University    2023, 57 (6): 631-641.   DOI: 10.16183/j.cnki.jsjtu.2022.237 Abstract （399）   HTML （356）    PDF（pc） （14702KB）（574）       Knowledge map    Save In recent years, offshore wind turbines show the trend of large-scale development, the installation area of which has been expanding to the deep and far-reaching ocean. However, due to the harsh environmental conditions in the far-reaching ocean region, the traditional rotor-lifting method is facing many limitations. In contrast, the single blade installation technology has significant advantages in installation efficiency and safety, and has gradually become a new research hotspot. Based on the characteristics and difficulties of the offshore single blade installation technology, this paper investigates and summarizes the lifting equipment and key technologies involved in single blade installation section, including blade yokes, the single blade installation dynamic simulation model, and the active control technology. Among them, the research and development of novel single blade installation equipment and methods with active control technology are essential for large-scale offshore wind turbine installation in the far-reaching ocean region. Additionally, based on the development trend and prospect of offshore blade installation and the docking technology, it introduces some technical ideas, including single blade yoke with dynamic positioning function, and double hoop blade vertical installation auxiliary device, which are expected to solve the installation problem of large-scale offshore wind turbines. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Numerical Study of Stern Vibration of a Self-Propulsion Ship in Propeller Induced Pressure Fluctuation QIN Guangfei, YAO Huilan, ZHANG Huaixin Journal of Shanghai Jiao Tong University    2022, 56 (9): 1148-1158.   DOI: 10.16183/j.cnki.jsjtu.2021.175 Abstract （749）   HTML （21）    PDF（pc） （15563KB）（566）       Knowledge map    Save To study the stern vibration characteristics of the ship sailing in still water under the action of propeller induced pressure fluctuation, the propeller self-propulsion numerical simulation was conducted based on the Reynolds-averaged Navier-Stokes (RANS) method, in combination with the shear-stress transport (SST) k-ω model. Taking the obtained fluctuating pressure on the hull surface as the external excitation, the acoustic-structure coupling calculation was performed through the structural finite element model coupled with the flow field boundary element model, and a numerical prediction method for the stern vibration of the self-propulsion ship excited by the propeller surface force was established. By analyzing the fluctuating pressure characteristics in the time domain and frequency domain, it is found that the amplitude of the blade frequency component is much larger than that of other frequency components. For the right-handed propeller, the starboard side pressure amplitude above the propeller is higher than that on the port side. The analysis of the corresponding relationship between the propeller fluctuating pressure, the structural inherent characteristics, and the vibration response shows that the coupled mode natural frequency should be far away from the propeller excitation force frequency to reduce the vibration response. The exploration of the effect of modifying stern structure on the vibration response at the same excitation indicates that increasing the plate thickness or installing stiffeners can change the inherent characteristics of the structure, thus avoiding resonance and achieving the vibration reduction effect. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Resistance Element Welding of Carbon Fiber Reinforced Thermoplastic Composites to High-Strength Steel WANG Yecheng, LI Yang, ZHANG Di, YANG Yue, LUO Zhen Journal of Shanghai Jiao Tong University    2022, 56 (10): 1349-1358.   DOI: 10.16183/j.cnki.jsjtu.2021.271 Abstract （680）   HTML （138）    PDF（pc） （47715KB）（565）       Knowledge map    Save The high strength joining of carbon fiber reinforced nylon 6 composites (CF/PA6) to TWIP980 steel was achieved by resistance element welding (REW). A 304 stainless steel rivet was used as an assistant element. The effect of welding current and welding time on the joint mechanical property was studied. Four joint failure modes with different strengths were identified, and the microstructures of joints, and the interfaces between CF/PA6 and the steel were analyzed. As the melting point and thermal conductivity of CF/PA6 are lower than those of the high-strength steel, it is prone to overheat and decompose during welding. While ensuring the formation of a certain size of weld nugget, avoiding or reducing the decomposition of CF/PA6 is the key to the successful implementation of CF/PA6 high-strength steel REW. By using a hard welding process such as high welding current and short welding time, high strength joints can be obtained while reducing the decomposition of CF/PA6. Based on the failure load of the joint, the weld lobe under the conditions of this study was determined. The process is sensitive to the change of welding time, and the allowable welding time range is narrow. The decomposition of CF/PA6 cannot be avoided completely even when the welding parameters in the weld lobe are employed. Therefore, it is necessary to conduct further research on the temperature field and the nugget formation mechanism of the REW process. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Numerical Simulation and Flow Pattern Evolution of Gas-Liquid Two-Phase Flow Passing Through a 90° Pipe Bend Based on CFD WANG Zhiwei, HE Yanping, LI Mingzhi, QIU Ming, HUANG Chao, LIU Yadong Journal of Shanghai Jiao Tong University    2022, 56 (9): 1159-1167.   DOI: 10.16183/j.cnki.jsjtu.2021.185 Abstract （767）   HTML （30）    PDF（pc） （11131KB）（564）       Knowledge map    Save In order to investigate the evolution characteristics of gas-liquid two-phase flow passing through a 90° pipe bend, the volume of fluid (VOF) multiphase flow model and the Realizable k-ε turbulence model are used to conduct numerical simulations. The evolution of velocity, pressure distribution, gas void fraction, and flow pattern passing through a 90° pipe bend is studied in detail. The results show that different gas-liquid two-phase flow patterns will produce different degrees of secondary flow phenomenon after passing through the 90° pipe bend, and the tangential velocity presents a bimodal distribution, which eventually dissipates into a unimodal distribution in the horizontal pipe. The pressure on the outer wall of the pipe bend increases as the inlet velocity increases. The change of gas void fraction is related to the transformation of the flow pattern, the bubbly flow evolves into a slender slug flow in the horizontal pipe after passing through the 90° pipe bend, and the gas void fraction will decrease. The slug flow, the churn flow, and the annular flow evolve into the stratified-wave flow in the horizontal pipe after passing through the pipe bend, and the variation of the gas void fraction is relatively low. The research results can provide certain theoretical support for the design and development of gas-liquid two-phase flow conveying elbows and the prediction of induced stress. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Numerical Analysis of Influence of Blade Icing on Dynamic Response of Integrated Wind Turbine Structure CHUANG Zhenju, LI Chunzheng, LIU Shewen Journal of Shanghai Jiao Tong University    2022, 56 (9): 1176-1187.   DOI: 10.16183/j.cnki.jsjtu.2021.258 Abstract （697）   HTML （20）    PDF（pc） （10181KB）（559）       Knowledge map    Save Based on the integrated jacket-support offshore wind turbine model of the National Renewable Energy Laboratory (NREL), the computational fluid dynamics (CFD) method is coupled with the wind turbine integrated analysis method to study the blade icing process and its influence on the overall dynamic performance of the wind turbine. First, the blade motion attitude calculated by the integrated analysis method is input into CFD. The discrete multiphase model and melting solidification model are used to simulate the icing growth of three-dimensional wind turbine blades. The k-ε turbulence model is used to calculate the aerodynamic performance before and after icing. Finally, the aerodynamic results after blade icing are returned to the integrated analysis method to analyze the influence of blade icing on the overall response of the wind turbine. The results show that the blade icing increases linearly along the blade span. The icing is mainly concentrated on the leading edge of the blade with the thickest ice accumulation at the tip. The lift coefficient decreases and the drag coefficient increases after icing. Blade icing will reduce the power of the whole machine, the torque, and the rotor speed. At the same time, it will lead to additional vibration response at the blade tip and tower top, and increase the wind speed required by the wind turbine to reach the rated power. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Fast 3D Pose Estimation Method for High Speed GMAW of Large Box Girders LI Gaoyang, JIA Aiting, HONG Bo, LI Xiangwen, GAO Jiapeng Journal of Shanghai Jiao Tong University    2022, 56 (6): 794-800.   DOI: 10.16183/j.cnki.jsjtu.2020.362 Abstract （550）   HTML （25）    PDF（pc） （10448KB）（558）       Knowledge map    Save In the process of high speed gas metal arc welding (GMAW), large box girder has many complex working conditions, such as positioning weld, low assembly accuracy, difficulty in strictly ensuring the pose of workpiece through tooling, real-time change of 3D pose of weld, etc. The vision based weld recognition method has a large amount of calculation and is not aimed at the workpiece with positioning weld, making it difficult to obtain the 3D pose of large box girders quickly. Aimed at this problem, a fast 3D pose estimation method for large box girder based on laser displacement sensing and point cloud clustering was proposed. Using this method, the vertical plane and flat plane of the welding seam of large box girders were obtained by fast segmentation of point cloud. Then, the pose information of welding seam was calculated. A pose information estimation test was conducted for welds with different poses. The results show that when the welding speed is up to 1200 mm/min, the pose error of the weld is less than 0.25 mm and 1.8°respectively. The robustness of the automatic welding of large box girders to complex conditions of positioning weld and low assembly accuracy is enhanced, which greatly improves the welding quality. Table and Figures | Reference | Related Articles | Metrics | Comments（0）

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Centrifugal Test and Numerical Analysis of Impact of Surface Surcharge on Existing Tunnels LIU Jinhao, YAN Yuanzhong, ZHANG Qi, BIAN Rong, HE Lei, YE Guanlin Journal of Shanghai Jiao Tong University    2022, 56 (7): 886-896.   DOI: 10.16183/j.cnki.jsjtu.2020.412 Abstract （592）   HTML （16）    PDF（pc） （14733KB）（555）       Knowledge map    Save Surface surcharge has a significant impact on the safety and stability of existing underground tunnels, and relevant regulations in soft clay areas have very strict restrictions on the tunnel displacement caused by surface surcharge. In order to accurately assess the impact of surface surcharge on the tunnel displacement in soft clay areas, the influence of surface surcharge on tunnel displacement and soil deformation is studied by using the centrifugal model test, and a corresponding finite element model is established based on the centrifugal model test. The parameter values of the soil constitutive model are determined by indoor soil tests. From the aspects of soil strain and shear stiffness, the applicability of the HS model and the HSS model in the analysis of the soft clay surface surcharge problem is compared and analyzed. Based on the result, the influence of surface surcharge on the deformation of soft clay formation and tunnel displacement is further discussed while comprehensively considering the size of the surface surcharge and the location of the tunnel. The results can provide some reference for engineering design. Table and Figures | Reference | Related Articles | Metrics | Comments（0）