Table of Content

    28 May 2022, Volume 56 Issue 5 Previous Issue    Next Issue
    New Type Power System and the Integrated Energy
    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
    2022, 56 (5):  543-553.  doi: 10.16183/j.cnki.jsjtu.2021.418
    Abstract ( 849 )   HTML ( 1031 )   PDF (4975KB) ( 768 )   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.

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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
    2022, 56 (5):  554-563.  doi: 10.16183/j.cnki.jsjtu.2022.040
    Abstract ( 888 )   HTML ( 396 )   PDF (1648KB) ( 829 )   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.

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    Mechanical Engineering
    A Multiscale Similarity Ensemble Methodology for Remaining Useful Life Prediction in Multiple Fault Modes
    SHU Junqing, XU Yuhui, XIA Tangbin, PAN Ershun, XI Lifeng
    2022, 56 (5):  564-575.  doi: 10.16183/j.cnki.jsjtu.2021.024
    Abstract ( 672 )   HTML ( 28 )   PDF (4306KB) ( 626 )   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.

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    Conceptual Design of Mechatronics System by Integrating EBD and TRIZ
    XING Lu, HUA Yixiong, ZHANG Zhinan
    2022, 56 (5):  576-583.  doi: 10.16183/j.cnki.jsjtu.2020.361
    Abstract ( 788 )   HTML ( 17 )   PDF (4844KB) ( 532 )   Save

    A novel method for conceptual design of a mechatronics system was proposed, and the design framework of “requirement-environment-conflict-original understanding-solution” was established. The contradiction between design requirements and environmental constraints was identified by using the method of environment-based design (EBD), and the requirements and environment were iteratively analyzed to decouple complex and abstract issues. According to the original understanding of the theory of inventive problem solving (TRIZ), the product solution for specific needs was obtained, which ensured the directionality of innovation, the systematic generation of product design solutions, and the standardization of the design process. The friction and wear test machine of the aeroengine variable stator vane (VSV) shaft bushing system shows that the proposed design method is reasonable and effective.

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    Model of Assembly Deviation of Irregular Large Thin-Walled Structures Based on Higher-Order Composite Shell Element
    LIN Zhangpeng, YU Haidong, YUAN Ke
    2022, 56 (5):  584-593.  doi: 10.16183/j.cnki.jsjtu.2020.333
    Abstract ( 638 )   HTML ( 12 )   PDF (1933KB) ( 417 )   Save

    The non-uniform stiffness distribution of irregular large thin-walled structures leads to warping deformation in the process of machining and assembly. The structure modeling and accurate calculation of the large deformation is the key to predict and control the deviation. A novel irregular higher-order composite shell element based on the absolute nodal coordinate formulation (ANCF) was proposed to accurately calculate the deformation of irregular large thin-walled structures with higher-order slope coordinates and improved shape function, considering the continuity of elements at the contact interface. A discrete method of irregular large thin-walled structures was proposed to solve the problem of node connection and deformation coupling between elements with different thicknesses, and to describe the large deformation of irregular large thin-walled structures effectively by using the combination of irregular higher-order elements and composite elements. An assembly deformation calculation model of irregular large thin-walled structures was proposed based on continuum mechanics. The influence of the thickened area on assembly deviation and stiffness of scalloped segment structures of heavy rocket tank bottom was studied with the new elements and calculation model, so as to provide guidance for structure design.

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    Dynamic Model Predictive Control Method for Steering Control of Driving Robot
    JIANG Junhao, CHEN Gang
    2022, 56 (5):  594-603.  doi: 10.16183/j.cnki.jsjtu.2021.108
    Abstract ( 713 )   HTML ( 26 )   PDF (6497KB) ( 479 )   Save

    A dynamic model predictive control method for driving robots is proposed to realize accurate steering control of the test vehicle. First, the coupling dynamics model of the driving robot and the controlled vehicle is established, and the controllability of the coupling model is judged. Then, the Kalman filter is used to estimate the state of the coupled model, and a model predictive controller is designed according to the estimated state. The least square method is adapted to fit the nonlinear relationship between path curvature and prediction horizon, and a dynamic model predictive controller with variable prediction horizon is designed. Finally, the simulation and the test of the steering control of the driving robot at different conditions are conducted, and the results verify the effectiveness of the proposed method.

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    Engine Emission Prediction Based on Extrapolated Gaussian Process Regression Method
    WANG Ziyao, GUO Fengxiang, CHEN Li
    2022, 56 (5):  604-610.  doi: 10.16183/j.cnki.jsjtu.2021.231
    Abstract ( 901 )   HTML ( 127 )   PDF (1750KB) ( 478 )   Save

    Aimed at improving the prediction accuracy of engine emissions under driving conditions which are not covered by the training set, an extrapolated Gaussian process regression (GPR) method is proposed. First, the training set data is fed to the GPR model for pre-training, and then a wide-area input set is constructed by uniform sampling between plus/minus three standard deviations, and the hyperparameters are optimized for the goal of minimizing the prediction variance of the input set. The test results on a direct injection gasoline engine show that the mean absolute error of emission prediction using the extrapolated GPR is 0.53411, which is 24.27% lower than that of using the traditional GPR and 36.32% lower than that of using the back propagation (BP) neural network, which signifies the effectiveness of the proposed method in terms of reducing test costs and improving the accuracy of emission prediction during real driving.

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    Numerical Simulation and Experimental Study of Oil-Free Double-Warp Air Scroll Compressor
    SUN Jian, PENG Bin, ZHU Bingguo
    2022, 56 (5):  611-621.  doi: 10.16183/j.cnki.jsjtu.2021.115
    Abstract ( 895 )   HTML ( 20 )   PDF (19911KB) ( 528 )   Save

    In order to analyze the flow characteristics of the internal flow field in the working chamber of the oil-free double-warp scroll compressor, a three-dimensional unsteady numerical simulation of the internal flow field in the working chamber of the compressor is conducted based on the computational fluid dynamics (CFD) method. In order to verify the deviation between the numerical simulation and the actual working process, a test platform for scroll compressors using air as the working medium is built, and the actual output performance parameters of the oil-free double-warp scroll compressor are obtained. The results show that the mass exchange between adjacent working chambers has a greater impact on the working chamber and the distribution of temperature and velocity along the tooth height direction, but has a little impact on pressure. The inlet and outlet mass flow and velocity rate change periodically, and as the compressor speed increases, the theoretical volume flow increases.

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    Transient Characteristics of a High-Speed Aero-Fuel Centrifugal Pump in Variable Gas-Liquid Ratio Conditions
    LI Jia, LI Huacong, WANG Yue
    2022, 56 (5):  622-634.  doi: 10.16183/j.cnki.jsjtu.2021.092
    Abstract ( 830 )   HTML ( 8 )   PDF (19747KB) ( 457 )   Save

    To clarify the transient flow characteristics of a high-speed aero-fuel centrifugal pump in variable gas-liquid ratio conditions, numerical simulations for the internal flow field in design flow rate and small flow rate conditions are conducted, focusing on the transient flow characteristics and time-frequency performance of pressure pulsation in the impeller channel. The conversion relationship between gas-liquid ratio and inlet pressure is given to determine the inlet simulation boundary, and then the grid model and length of time step are checked for relevant test. The prediction results between simulations and test are given to verify the effectiveness of the adopted simulation method. Then, the transient characteristics are analyzed through the results of pressure contour and turbulent kinetic energy, and the time-frequency performances of pressure pulsations at impeller inlet and outlet are conducted by fast Fourier transform(FFT). The results show that the flow in the impeller channel is relatively stable under the fuel saturation condition, and the main frequency of pressure amplitude is rotation frequency. With the increase of gas-liquid ratio, the impeller inlet produces a low-pressure zone whose area is significantly enlarged. Besides, a certain wake flow zone is generated at impeller outlet, where the turbulent energy dissipation rate is also demonstrated to be the strongest at these zones. Moreover, the inlet pressure is generally decreased with the increase of gas-liquid ratio, and the main frequency at the design flow rate is rotation frequency, but other frequency multiplication appears at the small flow rate. Meanwhile, the wake flow at the impeller outlet does not seriously affect the main frequencies at the monitoring points, where the main frequency is still rotation frequency.

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    Large Eddy Simulation on Blow-Off Limit of Methane and Hydrogen-Mixed Gas
    ZHOU Xirui, WANG Ping, ZENG Haixiang, ZHANG Yang, PRASHANT Shrotriya, ANTONIO Ferrante, QI Haotian
    2022, 56 (5):  635-647.  doi: 10.16183/j.cnki.jsjtu.2020.329
    Abstract ( 715 )   HTML ( 21 )   PDF (10173KB) ( 401 )   Save

    The blow-off limits of methane and hydrogen-mixed gas on the Sydney inhomogeneous inflow jet burner were calculated and studied by large eddy simulation. The GRI 3.0 detailed reaction mechanism, 28-step and 19-step methane simplified reaction mechanisms were used to calculate the laminar premixed flames under the condition of different hydrogen-mixed fuel gases, which demonstrates the good performance of the 19-step simplified mechanism. A dynamic thickening flame combustion model was combined with the 19-step reaction mechanism to compute the Sydney partially premixed jet flame burner with a hydrogen-mixed gas (the volume ratio of V(H2):V(CH4):V(CO):V(CO2) = 0.2:0.2:0.27:0.33). The blow-off limits in FA and FJ layouts of hydrogen-mixed gas are 90 m/s and 109 m/s, while for pure methane flames are 74 m/s and 128 m/s, respectively. The difference of blow-off limits between the two fuels is related to the inhomogeneity of fuel and air mixing in different layouts. This study shows that the combustion stability can be improved by optimizing the inlet layout and mixing process of fuel gas and air.

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    Design of a Grooved Cross-Section Silicon Needle for Assisting Deep Implantation of Flexible Neural Probe
    HE Yuxin, ZHANG Wenguang, XU Liyue, ZHOU Xuhui
    2022, 56 (5):  648-655.  doi: 10.16183/j.cnki.jsjtu.2020.341
    Abstract ( 778 )   HTML ( 10 )   PDF (2560KB) ( 429 )   Save

    Aimed at the buckling problem of deep implantation of flexible neural probe, a grooved cross-section silicon needle is designed as an auxiliary implant tool to provide temporary stiffness for probe implantation. In order to quantitatively evaluate the comprehensive performance of auxiliary tools, combining critical buckling force and cross-section area, and considering mechanical and biological properties, the performance evaluation index of auxiliary tools is proposed. Based on this evaluation index, the optimal groove depth ratio and groove width ratio of the grooved cross-section silicon needle are studied. The best groove depth ratio is the maximum value within the process requirements while the best groove width ratio increases with the thickness of the silicon needle. Moreover, the performance evaluation index is used to quantitatively prove that the grooved cross-section silicon needle has obvious performance advantages over the traditional circular and rectangular cross-section silicon needles. The simulation design of the grooved cross-section silicon needle is conducive to screening the best parameter combination of the cross-section, reducing the number of processing and the cost of experiments.

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    Naval Architecture, Ocean and Civil Engineering
    A Numerical Method for Transient Tracking of Sediment Particles in Dredge Pump
    GUO Tao, LIU Mingming, CAO Lei, HU Jingzhao, HONG Guojun, YOU Yunxiang
    2022, 56 (5):  656-663.  doi: 10.16183/j.cnki.jsjtu.2020.437
    Abstract ( 726 )   HTML ( 19 )   PDF (14885KB) ( 635 )   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.

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    Effect of Porosity on Local Scour Around Circular Array of Cylinders in Steady Currents
    LIU Shihang, LOU Xiaofan, TANG Guoqiang, WANG Bin
    2022, 56 (5):  664-674.  doi: 10.16183/j.cnki.jsjtu.2020.346
    Abstract ( 716 )   HTML ( 15 )   PDF (8169KB) ( 483 )   Save

    The local scour around a circular array of cylindrical piles through physical model was studied under the live-bed condition, concerning the effect of porosity of the structure on the local scour development. The porosity of the model was achieved by varying the number of single piles, while the outer diameter of pile groups was kept as a constant. The effect of porosity on the equilibrium scour depth, the scour extent, and the time scale of scour was examined. It is found that the scour around the pile group is significantly affected by the porosity of the structure. As p>0.7, the resultant scour is mainly determined by the scour around each individual pile. As p<0.5, the scour is characterized by the pattern of one single pile with the same outer diameter as the pile group. As 0.5<p<0.7, the scour shows a pattern of transition from local scour to global scour. It is also found that the normalized equilibrium scour depth is a power function of p, with a power of approximately 0.67.

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    Water Migration and Deformation Characteristics of Coastal Complex Strata in Artificial Freezing Process
    ZHOU Jie, REN Junjie
    2022, 56 (5):  675-683.  doi: 10.16183/j.cnki.jsjtu.2021.057
    Abstract ( 626 )   HTML ( 15 )   PDF (5190KB) ( 461 )   Save

    The difference in the water migration and the deformation characteristics of silty sand and clay in the freezing process cannot be ignored when the artificial ground freezing method is used in coastal complex strata consisting of clay and silty sand, and is also the root cause of current engineering accidents caused by freezing. In order to find out the difference of the water migration and the deformation characteristics between the silty sand and clay, a self-made single side freezing instrument was used to conduct a series of freezing tests of original silty sand of ②3 layer and the remodeled clay of ④ layer in Shanghai at a freezing temperature of -20 ℃, -15 ℃, and -10 ℃. The results show that the deformation curves can be divided into steep curve I(silty sand) and gradual curve II(clay). The deformation curves of different layers of clay soil sample fluctuated greatly with time. The results indicate that water migration is fully developed inside the clay during the freezing process, while most of the water inside the silty sand freeze quickly and thus water migration is not developed as obvious as that inside the clay. In addition, the deformation curves of the two types of soils is consistent with the distribution changes of water inside the silty sand and clay after freezing. Based on the research results, specific suggestions can be made for the relevant measures to deal with engineering problems such as frost heave in the practice of the freezing method for coastal complex strata consisted of silty sand and clay.

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    Seismic Response Analysis of Cut-Off Wall of Dam Foundation Under Spatial Variability of Parameters
    ZHANG Fuyou, ZHOU Qiangqiang, DU Pengcheng
    2022, 56 (5):  684-692.  doi: 10.16183/j.cnki.jsjtu.2021.242
    Abstract ( 642 )   HTML ( 18 )   PDF (4705KB) ( 501 )   Save

    The overburden of rockfill dams has complex soil types, loose structures, and sometimes lenses, which make the material parameters of the overburden have spatial variability, and the impact of earthquakes on the stress and deformation of the dam foundation cut-off wall cannot be ignored. Under the framework of Monte Carlo, by using the Gaussian spatial random field discrete method of Cholesky decomposition, the secondary development of Abaqus with Python is used to realize the “non-invasive” stochastic finite element analysis of the spatial variability of the overburden material. The research results show that considering the spatial variability of the cover material, the stress and deformation of the different parts of the cut-off wall have different degrees of excess, and the coefficient of variation of dynamic stress is greater than that of the dynamic displacement, indicating the variability of the material parameters of the cover is more sensitive to the stress changes of the impervious wall under the action of earthquake. Therefore, this uncertainty should be considered in the design stage to ensure the safe operation of the dam foundation impervious wall.

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