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Table of Content

    28 September 2022, Volume 56 Issue 9 Previous Issue    Next Issue
    New Type Power System and the Integrated Energy
    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
    2022, 56 (9):  1111-1117.  doi: 10.16183/j.cnki.jsjtu.2021.364
    Abstract ( 918 )   HTML ( 782 )   PDF (851KB) ( 659 )   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.

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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
    2022, 56 (9):  1118-1127.  doi: 10.16183/j.cnki.jsjtu.2021.415
    Abstract ( 621 )   HTML ( 132 )   PDF (1463KB) ( 657 )   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.

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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
    2022, 56 (9):  1128-1138.  doi: 10.16183/j.cnki.jsjtu.2022.145
    Abstract ( 695 )   HTML ( 128 )   PDF (3139KB) ( 593 )   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.

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    An LC Inverter Based on Novel Dual-Loop Control
    LI Shuang, SHI Jianqiang
    2022, 56 (9):  1139-1147.  doi: 10.16183/j.cnki.jsjtu.2021.275
    Abstract ( 799 )   HTML ( 127 )   PDF (1553KB) ( 665 )   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.

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    Naval Architecture, Ocean and Civil Engineering
    Numerical Study of Stern Vibration of a Self-Propulsion Ship in Propeller Induced Pressure Fluctuation
    QIN Guangfei, YAO Huilan, ZHANG Huaixin
    2022, 56 (9):  1148-1158.  doi: 10.16183/j.cnki.jsjtu.2021.175
    Abstract ( 694 )   HTML ( 21 )   PDF (15563KB) ( 521 )   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.

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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
    2022, 56 (9):  1159-1167.  doi: 10.16183/j.cnki.jsjtu.2021.185
    Abstract ( 693 )   HTML ( 23 )   PDF (11131KB) ( 489 )   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.

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    Discrete Element Simulation and Analysis of Ice-Inclined Structure Interaction
    WANG Yanlin, GUO Qi, SUN Shanshan, WEI Sihao, XU Ning
    2022, 56 (9):  1168-1175.  doi: 10.16183/j.cnki.jsjtu.2021.182
    Abstract ( 590 )   HTML ( 18 )   PDF (4028KB) ( 467 )   Save

    Inclined structure is an important marine structure in the iced area. The change of the inclined angle will change the main failure mode of sea ice and affect the peak ice force acted on the structure. In order to simulate the random breaking characteristics of level ice, an irregular distributed dilated disk element model with bond-break function is constructed, and the dynamic process of interaction between the level ice and the inclined structure is simulated based on this model, which is verified by comparing the peak ice forces obtained by numerical simulation with the peak ice forces measured in the field. The influence law of the inclined angle on the ice force and the ice failure mode is analyzed. It shows that the variation of ice load with the changes of inclined angles simulated by the numerical method is basically consistent with the variation calculated by the two-dimensional theoretical model. With the increase of the incline angle, the proportion of bending failure decreases and the peak ice force and its occurrence probability increase. The inclined angle is an important factor in the change of sea ice failure modes and the peak ice force. This paper can be used as a reference for discrete element numerical simulation of sea ice and ice-resist design of inclined marine structures.

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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
    2022, 56 (9):  1176-1187.  doi: 10.16183/j.cnki.jsjtu.2021.258
    Abstract ( 629 )   HTML ( 19 )   PDF (10181KB) ( 465 )   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.

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    Hydrodynamic Characteristics of a Surface Piercing Propeller Entering Water with Different Radiuses
    DING Enbao, CHANG Shengming, SUN Cong, ZHAO Leiming, WU Hao
    2022, 56 (9):  1188-1198.  doi: 10.16183/j.cnki.jsjtu.2021.169
    Abstract ( 664 )   HTML ( 19 )   PDF (5876KB) ( 409 )   Save

    In order to investigate the influence of a dimensionless section position of a surface piercing propeller on the hydrodynamic characteristics of the surface piercing propeller cup section, the cup section of the surface piercing propeller at the dimensionless radius of 0.6, 0.7, and 0.8 is selected for modeling. By solving the RANS equation to simulate the cup section entry process, in combination with the volume of fluid method and the overlapping grid technique, a reliable numerical method is established. The hydrodynamic characteristics of the water entry process of the surface piercing propeller cup section at different section positions are studied. The effects of different section positions on the free surface form, ventilation cavity form, flow field, and the surface pressure distribution in the water entry process of the surface piercing propeller cup section are analyzed. The results show that with the position of the dimensionless radius section getting closer to the tip of the surface piercing propeller, the transition state between the fully ventilated state and the partially ventilated state occurs at a larger speed coefficient, and the transverse force coefficient and the open water efficiency increases.

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    Multiscale Calculation of Elastic Modulus of Cement Paste Based on Grid Nanoindentation Technology
    CHEN Xiaowen, HAN Yudong, DING Xiaoping, HOU Dongwei
    2022, 56 (9):  1199-1207.  doi: 10.16183/j.cnki.jsjtu.2021.089
    Abstract ( 653 )   HTML ( 16 )   PDF (1695KB) ( 442 )   Save

    The calculation of multiscale elastic parameters of cementitious materials based on micromechanical tests and the composite material theory is one of the key theoretical bases for precise design of cementitious materials performance. In this paper, grid nanoindentation tests of microscopic elastic modulus and the mercury intrusion test were conducted on hardened cement paste specimens at different water-cement ratios, to establish a multiscale homogenization calculation method for the elastic modulus of cement paste considering the influence of pores. Besides, the applicability of the dilute method, the self-consistent method, the Mori-Tanaka method, the interaction direct derivation (IDD) method, and the multilevel homogenization method was compared. The results show that the multi-phase and multi-scale calculations considering the effect of pores is in good agreement with experimental values. Except the multi-level homogenization method, the calculation results of several commonly used composite homogenization methods are similar.

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    Mechanical Characteristics and Stress and Strain Analysis of Concrete with Bonding Interface Under Impact Load
    ZHAO Hong, XIE Youjun, LONG Guangcheng, LI Ning, ZHANG Jiawei, CHENG Zhiqing
    2022, 56 (9):  1208-1217.  doi: 10.16183/j.cnki.jsjtu.2021.343
    Abstract ( 583 )   HTML ( 17 )   PDF (12231KB) ( 416 )   Save

    To study the dynamic mechanical characteristic of steam cured concrete and self-compacting concrete bonding interface, a split Hopkinson pressure bar (SHPB) test was used to evaluate the dynamic properties of concrete with a bonding interface. The failure pattern and the characteristics of stress-strain curves and a constitutive model of concrete with a bonding interface were discussed. The results show that the impact destructions are associated with two forms of failures, i.e., the interface separation failure and concrete crushed failure. In interface separation failure, the peak stress, dynamic increase factor (DIF), peak strain, and impact toughness of concrete with a bonding interface increase with the increase of strain rate, and the concrete with a bonding interface shows a stronger strain rate sensitivity. In concrete crushed failure, there exist debonding deformation and crush deformation exist simultaneously. With the increase of strain rate, the accumulation and development of crack at the interface could make the interface zone play an energy relieving role in concrete with a bonding interface. The peak stress and the DIF of concrete with a bonding interface remain unchanged, while the peak strain and impact toughness both increase. The calculated data by the established dynamic constitutive model are similar to the experimental results, especially before the ultimate state of strain stress curves.

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    Micropore Characteristics and CT Seepage Test of Jinan Red Clay with a Strong Vertical Permeability
    LU Linhai, WU Chaojun, SUN Jiecheng, CAI Hao, YE Guanlin
    2022, 56 (9):  1218-1226.  doi: 10.16183/j.cnki.jsjtu.2021.234
    Abstract ( 452 )   HTML ( 10 )   PDF (34551KB) ( 324 )   Save

    Because of the particularity and complexity of Jinan spring area, the quaternary sedimentary layer is mainly composed of clay and silty clay, which has the characteristics of a strong permeability. In the construction of excavation, a series of problems such as the precipitation abnormal difficulties and the serious structural water seepage would occur. In order to reveal the causes of the strong permeability of Jinan red clay, a study from the perspective of micropore structure of Jinan red clay was conducted. First, the basic physical properties of the undisturbed red clay were tested, and the micro particle arrangement of the red clay was obtained by the scanning electron microscope (SEM). Then, a soil seepage device based on computed tomography (CT) was developed. The three-dimensional pore structure and the water flow visualization of the red clay in different seepage stages were obtained through CT scanning. Finally, a pore network model (PNM) was established to quantitatively analyze the number and the volume proportion of the pores and throats in the soil during the seepage process. The results show that the overlapping of particles in the horizontal section of Jinan red clay is more loose, and the pore structure is mainly developed vertically, with the existence of large connected channels. Water flows preferentially along the existing connected pore channel of the red clay, which leads to the expansion of the seepage channel. The connected channel with a large pore diameter is the main factor affecting the permeability of the soil.

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    Anti-Uplift Portal Frame in Control of Underlying Tunnel Deformation Induced by Foundation Pit Excavation
    WU Huaina, FENG Donglin, LIU Yuan, LAN Ganzhou, CHEN Renpeng
    2022, 56 (9):  1227-1237.  doi: 10.16183/j.cnki.jsjtu.2022.006
    Abstract ( 627 )   HTML ( 13 )   PDF (11913KB) ( 355 )   Save

    The excavation of foundation pit above the existing metro tunnel inevitably leads to the uplift of the tunnel. As an anti-uplift measure, the anti-uplift portal frame is still lack of research. Based on a foundation pit excavation project colinear with tunnel for long-distance, the excavation influence on the underlying shield tunnel during the construction process of anti-uplift portal frame and the foundation pit excavation was studied via numerical simulation. The interaction mechanism between the anti-uplift portal frame and ground as well as the anti-uplift effect were analyzed. Finally, a structural optimization design was proposed based on the simulation. The results show that the tunnel may be uplifted due to the shaft excavation during the construction of the anti-uplift portal frame and the uplift can be effectively restricted by backfilling and sectional excavation. Compared to the excavation without the anti-uplift portal frame, the uplift value of the tunnel decreases from 19.5 mm to 15 mm because of the restriction of the anti-uplift portal frame. The connection between the slabs and piles are weak positions of the structure due to the stress concentration and it is necessary to do a local reinforcement treatment in the connection.

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    Effect of Dynamic Properties of Temperature and Frequency-Dependent Properties of Damping Layer on Vibration Characteristics of Ballastless Track
    NIU Zhenyu, LIU Linya, QIN Jialiang, ZUO Zhiyuan
    2022, 56 (9):  1238-1246.  doi: 10.16183/j.cnki.jsjtu.2021.030
    Abstract ( 504 )   HTML ( 15 )   PDF (1995KB) ( 351 )   Save

    Taking the damping layer as the research object, first, by using the dynamic mechanical test, based on the high-order fractional derivative FVMP model, and in combination with the temperature-frequency equivalent principle, the temperature and frequency dependent properties of the damping layer was characterized. Then, the model was applied to the vehicle-CRTSIII slab ballastless track coupled system. Finally, the effect of the temperature and frequency dependent properties of the damping layer on track structure vibration response was analyzed. The results show that the temperature and the loading frequency have a significant impact on the dynamic mechanical properties on the damping layer and the high-order fractional derivative FVMP model can accurately characterize this property. In the time domain response, the peak values of the slab track displacement and the acceleration on the FVMP model are significantly larger than those on the K-V model. At each reference temperature point, the displacement response of the slab track on the FVMP model decreases with the decrease of temperature, while the acceleration of the slab track shows an opposite trend. In the middle and high frequency band, the frequency domain response of the slab track on the FVMP model are greater than those on the K-V model. At each reference temperature point, the response of the slab track on the FVMP model decreases with the decrease of the temperature. Therefore, in order to improve the accuracy of the track structure prediction, it is necessary to consider the temperature and frequency dependent properties of the damping layer.

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    Bending Properties of Unbonded Flexible Risers with Composite Materials
    LIU Qingsheng, XUE Hongxiang, YUAN Yuchao, TANG Wenyong
    2022, 56 (9):  1247-1255.  doi: 10.16183/j.cnki.jsjtu.2021.144
    Abstract ( 609 )   HTML ( 15 )   PDF (3186KB) ( 422 )   Save

    Unbonded flexible risers are widely applied to transport oil and gas resources from seabed to platform, and composite cylindrical layers are sometimes contained due to design requirements. Based on an 8-layer unbonded flexible riser model, the bending properties of the unbonded flexible risers with composite cylindrical layers are studied. A theoretical method of combining axisymmetric and bending loads acting on unbonded flexible risers is proposed, and a numerical method with detailed geometric characteristics taken into account is established for verification. The influence of two typical composite materials as well as the fibre volume fraction on the bending properties of the unbonded flexible risers is analyzed. The theoretical and the numerical results are in good agreement, which shows that the bending properties of the unbonded flexible risers are greatly affected by the axial Young’s modulus of the composite cylindrical layers, and composite material with larger axial Young’s modulus would greatly enhance the bending stiffness of the unbonded flexible risers, expecially in the full-slipping stage. In addition, the axial tensile stiffness and bending stiffness of full-slipping stage are proportional to the fibre volume fraction of the composite cylindrical layers.

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    Mechanical Engineering
    Energy Consumption Prediction of Office Buildings Based on CNN-RNN Combined Model
    ZENG Guozhi, WEI Ziqing, YUE Bao, DING Yunxiao, ZHENG Chunyuan, ZHAI Xiaoqiang
    2022, 56 (9):  1256-1261.  doi: 10.16183/j.cnki.jsjtu.2021.192
    Abstract ( 821 )   HTML ( 84 )   PDF (2358KB) ( 416 )   Save

    In order to accurately reflect the operation characteristics of office buildings, a convolutional neural network(CNN)-recurrent neural network(RNN)combined model for energy consumption prediction of office buildings is proposed by using the good feature extraction ability of CNN and the good time series learning ability of RNN. Besides, a two-dimensional matrix data input structure suitable for the deep learning model is designed. The case study results show that compared with the simple recurrent neural network and long short term memory network, both the prediction accuracy and computational efficiency of CNN-RNN combined model are significantly improved, and the generalization of the model is also good.

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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
    2022, 56 (9):  1262-1275.  doi: 10.16183/j.cnki.jsjtu.2021.215
    Abstract ( 752 )   HTML ( 67 )   PDF (4009KB) ( 701 )   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.

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    Multi-Stage Opportunistic Maintenance Decision-Making for Electric Multiple Unit Systems with Bi-Objective Optimization
    WANG Hong, QI Yankun, HE Yong, YANG Guojun
    2022, 56 (9):  1276-1284.  doi: 10.16183/j.cnki.jsjtu.2021.104
    Abstract ( 551 )   HTML ( 62 )   PDF (1218KB) ( 366 )   Save

    In order to improve operation efficiency of the electric multiple unit when running reliably, a multi-stage opportunistic maintenance decision strategy with bi-objective optimization is proposed based on the traditional opportunistic maintenance strategy. The window of opportunistic maintenance is equidistantly divided into multiple stages, and components located at different stages are maintained by different efforts. Aimed to solve problem of assigning multiple maintenance tasks of components, an assignment algorithm with two repairpersons is proposed. To further improve the multi-attribute optimization performance of this model, the proposed algorithm is introduced into the multi-attribute decision-making. The numerical example analysis verifies the effectiveness of the multi-stage opportunistic maintenance strategy in optimizing availability and average cost rate. Furthermore, the influence of weight factors on optimization tendency is discussed as well.

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