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Table of Content

    28 August 2023, Volume 57 Issue 8 Previous Issue   
    Naval Architecture, Ocean and Civil Engineering
    Support Structure Optimization of High-Pile Cap Supported Horizontal Axis Wind Turbine System Based on BESO Algorithm
    ZHAN Lingyu, HE Wenjun, ZHOU Dai, HAN Zhaolong, ZHU Hongbo, ZHANG Kai, TU Jiahuang
    2023, 57 (8):  939-947.  doi: 10.16183/j.cnki.jsjtu.2022.182
    Abstract ( 116 )   HTML ( 17 )   PDF (9027KB) ( 143 )   Save

    The study of reliable support structure is of great significance to the safety of large-scaled horizontal axis wind turbine (HAWT) system. In this paper, for cap-supported HAWT with high pile, the bidirectional evolutional structure optimization (BESO) algorithm based on inversely proportional deletion rate was used to optimize its support structure. Using computational fluid dynamics (CFD) and the principle of pile-soil interaction, the finite element model of HAWT was established, where the wind load and pile-soil interaction were taken into consideration. The reliability of the structural optimization method was verified through the comparison of the dynamic response characteristics between the initial and the optimized model. The results show that the current BESO algorithm can effectively generate a novel support structure form for high-pile HAWT, whose dynamic response is significantly reduced. The results can provide useful references for HAWTs designs.

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    Temperature Rise and Wear Characteristics of Mechanical Seal Face of Deep-Sea Equipment Under Alternating Conditions
    ZHENG Simin, TENG Liming, ZHAO Wenjing, JIANG Jinbo, WANG Mengjiao, PENG Xudong
    2023, 57 (8):  948-962.  doi: 10.16183/j.cnki.jsjtu.2021.528
    Abstract ( 152 )   HTML ( 3 )   PDF (18085KB) ( 56 )   Save

    In order to study the effects of deep-sea complex and severe working conditions on the power device of deep-sea wading equipment, taking the contacting mechanical seal for deep-sea propeller as the research object, a two-dimensional axisymmetric finite element model is established. The influence of alternating conditions on the temperature rise of seal face is explored. The pseudo-real condition test of the mechanical seal is conducted on a self-built test rig, and the temperature rise of seal face is monitored. The surface morphology and wear characteristics are measured and analyzed. The results show that the alternating conditions have a significant influence on the temperature field of the seal ring, and the temperature rise of seal face shows an obvious alternating transient characteristic. After the alternating condition test, the end face roughness of the rotating ring increases significantly. The transient working condition makes the contact state between the seal faces unstable. Abrasive wear occurs on the end face, with obvious pits and densely distributed furrows of different depths. The alternating speed has a greater influence on the temperature rise and wear of the end face than that of the alternating medium pressure. The numerical simulation results are in good agreement with the experimental results, which provides a necessary theoretical guidance and experimental basis for the structural design of the mechanical seal of the deep-sea propeller.

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    A CNN-LSTM Ship Motion Extreme Value Prediction Model
    ZHAN Ke, ZHU Renchuan
    2023, 57 (8):  963-971.  doi: 10.16183/j.cnki.jsjtu.2022.089
    Abstract ( 80 )   HTML ( 4 )   PDF (2516KB) ( 158 )   Save

    Aimed at the short-term extreme value prediction of ship motion, a sliding window method based on motion spectrum information is proposed to extract feature data, based on which, a series prediction model of convolutional neural networks (CNN) and long short-term memory (LSTM) is built. The CNN module aims at the local correlation characteristics of the input data, and the LSTM module aims at the time dimension characteristics of the data. The simulation test results of S175 ship show that the model has a good prediction effect on the motion extremum information in the next 1 and 2 cycles, and the evaluation indexes are significantly better than those of LSTM and gate recurrent unit (GRU) models, which has an important application value.

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    Nonlinear Feedback Control of MIMO Unstable System for Ship Longitudinal Motion
    CAO Tian, ZHANG Xianku
    2023, 57 (8):  972-980.  doi: 10.16183/j.cnki.jsjtu.2022.076
    Abstract ( 53 )   HTML ( 3 )   PDF (2694KB) ( 69 )   Save

    In order to improve the robustness and energy saving of the controller for multiple input multiple output (MIMO) unstable systems, the mathematical model of pitching and the heave motion of the scientific ship “YUKUN” of Dalian Maritime University is taken as the research plant, and the root locus of the transfer function mathematical model with unstable zero-pole and zero-pole processes is pulled to the left half plane by using the root locus shaping technique and weighting matrix. The first-order closed-loop gain shaping algorithm is used to design the robust controller, and the nonlinear feedback driven by the bi-polar S function is introduced to replace the original error linear feedback. The simulation results show that the nonlinear feedback control improves heave and pitching when the model is perturbed, greatly reduces the control energy, and is robust to model disturbance. The solution process of the scheme is simple, and the physical significance of the controller and the controlled object of the whole system is clear. The order of the controller design is low, and the controller design method of the MIMO unstable system is supplemented and perfected.

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    Application of an Improved GPU Acceleration Strategy for the Smoothed Particle Hydrodynamics Method
    GUAN Yanmin, YANG Caihong, KANG Zhuang, ZHOU Li
    2023, 57 (8):  981-987.  doi: 10.16183/j.cnki.jsjtu.2022.209
    Abstract ( 42 )   HTML ( 4 )   PDF (1925KB) ( 65 )   Save

    In order to solve the problem of graphics processing unit (GPU) memory access conflicts possibly caused by the disorder of particles and enhance the computation efficiency, an improved GPU acceleration strategy is proposed by establishing particle reorder technology. The acceleration strategy is applied to the smoothed particle hydrodynamics (SPH) method to simulate the dam breaking with obstacles in three dimensions, and the algorithm is verified by comparing with the experimental results, which obtained a high calculation accuracy. Based on this benchmark example of the SPH, the studies on the effect of particle renumbering and the solution efficiency of the algorithm are conducted by comparing the simulations of different hardware facilities. The results indicate that the particle reorder technology can ensure a stable single-step running time, and can effectively solve the problem of graphic card memory access conflicts that commonly exist in the GPU-SPH algorithm. Furthermore, the GPU parallel algorithm can greatly improve the solution efficiency of the SPH method, and with the increase of particle number, the advantage of drastically reducing the computation time becomes more obvious. The method proposed in this paper provides the possibility to expand the application of the SPH method to solve 3D numerical simulations.

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    A Resolved CFD-DEM Approach Based on Immersed Boundary Method
    MAO Jia, XIAO Jingwen, ZHAO Lanhao, DI Yingtang
    2023, 57 (8):  988-995.  doi: 10.16183/j.cnki.jsjtu.2022.095
    Abstract ( 94 )   HTML ( 4 )   PDF (11088KB) ( 94 )   Save

    Based on the immersed boundary method, a resolved CFD-DEM algorithm is proposed to tackle fluid-solid interaction problems which widely exist. In the proposed method, the fluid filed is described by the computational fluid dynamics in the Eulerian framework, while the movement and collision of the solids are simulated by the discrete element method in the Lagrangian framework. In order to deal with the moving interfaces between the fluid and the solids, several immersed boundary points are allocated on the boundaries of the solids. Two classic test cases are calculated to verify the accuracy of the proposed method, including the vortex-induced vibration of a cylinder and the rotational galloping of a rectangular rigid body. Good agreements are achieved between the current results and those in previous references and the reliability of the present method in modelling the fluid-solid interaction problems are proved. Finally, the sedimentation of multiple solids is simulated and the ability of the proposed CFD-DEM method in solving the complex fluid field and the collision among the solids with arbitrary shapes are verified.

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    Mechanical Engineering
    Opportunistic Maintenance Modeling of Finishing Rolls Considering Dismounting Constraints
    BEN Xurui, ZHOU Xiaojun
    2023, 57 (8):  996-1004.  doi: 10.16183/j.cnki.jsjtu.2022.021
    Abstract ( 61 )   HTML ( 4 )   PDF (1449KB) ( 36 )   Save

    A single roll maintenance model is established to realize the dynamic decision of single roll maintenance cycle by considering the influence of roll wear, unit faults, and roll gap quality control on accident loss, piece quality loss, and maintenance cost. Considering special scenarios such as different grinding cycles of each roll, the same unloading cycle and allowing small adjustment of dismounting schedule, a dynamic opportunity maintenance strategy of work roll is proposed and a decision model is constructed to optimize the work roll opportunity maintenance scheme of the finishing rolls. The case study shows that compared with the traditional time window strategy, the dynamic opportunity maintenance strategy has more advantages in reducing the maintenance cost of work roll.

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    Remaining Useful Life Prediction of IGBT Modules Across Working Conditions Based on ProbSparse Self-Attention
    ZHONG Zhiwei, WANG Yuxiang, HUANG Yixiang, XIAO Dengyu, XIA Pengcheng, LIU Chengliang
    2023, 57 (8):  1005-1015.  doi: 10.16183/j.cnki.jsjtu.2021.538
    Abstract ( 146 )   HTML ( 3 )   PDF (5921KB) ( 82 )   Save

    In order to improve the accuracy of remaining useful life (RUL) prediction of insulated gate bipolar transistor(IGBT) modules across working conditions to enhance their reliability, an RUL prediction method based on the ProbSparse self-attention mechanism and transfer learning was proposed based on the transient thermal resistance features of IGBT modules under different working conditions. An accelerated aging test bench of the IGBT module was designed ang built to perform power cycling experiments in different temperature ranges, and state data of full life-time under different working conditions were collected. Transient thermal resistance change data during the IGBT module degradation were calculated, and the transient thermal features that can accurately reflect the aging state of the IGBT module were extracted and selected. These features were used to predict the RUL of IGBT modules across different working conditions based on the proposed method. The experimental result shows that the accuracy of the proposed RUL prediction method of IGBT modules across working conditions outperforms other compared methods. Particularly, the RUL prediction accuracy during the early degradation stage has been significantly improved.

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    Theoretical Modeling, Simulation Analysis, and Experimental Investigation of a Pneumatic Toothed Soft Actuator
    SU Yiyi, XU Qiping, LIU Jinyang
    2023, 57 (8):  1016-1027.  doi: 10.16183/j.cnki.jsjtu.2022.039
    Abstract ( 71 )   HTML ( 4 )   PDF (17776KB) ( 110 )   Save

    Based on the nonlinear geometric relationship of the bulging angle and the bending angle, and the principle of virtual work and nonlinear constitutive relationship of Neo-Hookean incompressible hyperelastic material, a quasi-static mechanical model for pneumatic toothed soft actuator was established, considering the strain energy of the bottom, side walls, and front and rear walls. Considering the geometric nonlinearity and material nonlinearity, the proposed model could solve the configuration of the soft actuator at different driving pressures and terminal loads precisely and efficiently. The finite element simulation of the cantilevered-free soft actuator was conducted by Abaqus, and the corresponding experimental device was established. The simulation analysis and experimental investigation were performed at different driving pressures. A comparison of the results show that there is a positive linear correlation between the driving pressure and the bending angle of the soft actuator, and the prediction of the theoretical model agrees well with the simulation and experimental results. In addition, the distribution of the strain energy was analyzed. Based on the equal-curvature model, the configuration results of the soft actuator at terminal loads are basically consistent with those obtained by Abaqus. The proposed quasi-static mechanical modeling method provides a theoretical basis for the structural optimization design, performance improvement, and motion control of similar soft actuators.

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    Prediction of Oil Retention in Compressor Suction Lines with Refrigerant/Oil Mixture
    ZHANG Zhiting, GU Bo, ZENG Weijie, HU Jinting, WU Pengzhan
    2023, 57 (8):  1028-1036.  doi: 10.16183/j.cnki.jsjtu.2022.071
    Abstract ( 48 )   HTML ( 4 )   PDF (6491KB) ( 26 )   Save

    At present, there is no method for predicting oil retention applicable to various working fluids. Oil retention characteristics in compressor suction lines are studied and a general method for predicting oil retention is established. The database of oil retention in suction lines is established according to experimental values in the public literature. After analyzing the influencing factors, a correlation of the volume ratio of oil retention in the database is fitted. According to the correlation and the state of working fluid at the inlet of suction line, the amount of oil retention can be predicted. In addition, oil retention of R32/PVE VG68 in suction lines is tested. A comparison of the experimental values and the prediction values indicate that for the flow of R32/PVE VG68 in suction lines, the calculation method can accurately show the variation trend of oil retention with various factors, and can accurately predict the amount of oil retention under different conditions.

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    Nonlinear Degradation Modeling and Residual Life Prediction for Rollers Based on Kernel-based Wiener Process
    WANG Hanyu, CHEN Zhen, ZHOU Di, CHEN Zhaoxiang, PAN Ershun
    2023, 57 (8):  1037-1045.  doi: 10.16183/j.cnki.jsjtu.2022.004
    Abstract ( 89 )   HTML ( 3 )   PDF (1553KB) ( 53 )   Save

    In the process of steel rolling, due to wear and other reasons, the working performance of the roll under long and complex working conditions has a gradual decline. Considering the characteristics of complex working conditions and strong random interference of the roll working environment, this paper proposed a kernel-based Wiener process (KWP) degradation model to characterize the strong randomness of the roll degradation trend by using the Wiener process, and to capture the nonlinear degradation path of the roll by using the kerna function. This paper derives the analytical expression of parameter estimation in the Bayesian framework, and constructs the health index of the roll working rotation, then predicts the remaining useful life (RUL) of the roll. In combination with the field data of 1580 hot rolling production line of an iron and steel company, the goodness of fit of the model built is 0.989, and the residual life prediction error is less than 4.7%. Compared with the common machine learning algorithm, it has achieved better results, which is helpful to improve the operating efficiency and safety of equipment and achieve maintenance as needed.

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    Geometrical Model and Optimization of Scroll Compressor Based on Involute of Circle with Variable Radii
    PENG Bin, LIU Huixin, TAO Yaohui
    2023, 57 (8):  1046-1054.  doi: 10.16183/j.cnki.jsjtu.2022.129
    Abstract ( 51 )   HTML ( 3 )   PDF (3426KB) ( 23 )   Save

    Considering the problems that quantitative analysis and optimization of the geometrical model of scroll compressor created from involute of circle with variable radii are incomplete, the changing trend of the working chamber volume from the beginning of the suction process to the end of the discharge process is given. The volume calculation differences of Green’s theorem method, the graphical method, and the normal isometric method are compared, the reasons for calculation errors are analyzed, and the correctness of the geometrical model is verified. The calculation formula of teeth area utilization rate is deduced, and the sensitivity models of suction volume and teeth area utilization rate are constructed. It is concluded that the influence of the base circle radius variation coefficient and the occurrence angle of the inner profile are particularly significant. A multi-objective optimization analysis model considering nonlinear constraints and taking the suction volume and teeth area utilization rate as the optimization goals is established. The results show that the multi-objective genetic algorithm NSGA-II has a better comprehensive performance than the multi-objective particle swarm algorithm MOPSO and the suction volume of the scroll compressor created from the involute of circle with variable radii for an automobile air conditioner has been increased by 6.5% and the teeth area utilization rate has been reduced by 4.27%. This paper can provide further theoretical reference for the optimal design and quantitative research of the scroll compressor constructed from involute of circle with variable radii.

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    Effect of Injection Strategy on Low Load Premixed Combustion of a Diesel Engine in Engine Speed Extension
    FAN Chao, LU Yingying, LIU Yize
    2023, 57 (8):  1055-1066.  doi: 10.16183/j.cnki.jsjtu.2021.433
    Abstract ( 42 )   HTML ( 2 )   PDF (8737KB) ( 63 )   Save

    In this paper, the influence of the multiple injection strategy on premixed charge compression ignition (PCCI) combustion of a heavy-duty diesel engine in low load speed extension is studied experimentally and numerically, and the general optimization direction of low-load spray combustion of a heavy-duty diesel engine is obtained. The injection timing should match the shape of the combustion chamber, so that the oil, gas, and chamber are combined to make full use of the advantage of the shape of the combustion chamber. As the speed increases, the multi-injection strategy can overcome the defects such as the decrease of injection rate and the decrease of oil-gas mixing degree caused by the extension of injection duration. For single injection at a low speed, through optimizing the injection strategy, the NOx emission is reduced by 38%, the soot emission is decreased by one order of magnitude, and the indicated thermal efficiency is increased by 8.66%. For single injection at a medium speed, the indicated thermal efficiency remains unchanged, the NOx emission is reduced by 59.3%, and the soot emission is reduced by 70%. For single injection at a high speed, the thermal efficiency and the NOx emission are increased slightly while the soot emission is decreased significantly. In addition, it is found that with the increase of speed, the influence of the multiple injection strategy on indicated thermal efficiency and emissions is gradually increased, and the optimization effect of the multiple injection strategy is more obvious than that of low speed.

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    Energy Conversion Efficiency of Wavy Conical Wind Energy Capture Structure
    ZOU Lin, YAN Yulong, TAO Fan, LIU Diwei, ZHENG Yunlong
    2023, 57 (8):  1067-1077.  doi: 10.16183/j.cnki.jsjtu.2022.137
    Abstract ( 69 )   HTML ( 2 )   PDF (14616KB) ( 42 )   Save

    In order to improve the energy harvesting efficiency of the wind energy capture structure, this paper proposes a novel wavy conical bladeless wind energy capture structure, and establishes a mathematical model for energy conversion of the wavy conical wind energy capture structure. The Reynolds-averaged N-S equations in combination with the SST k-ω turbulence model is used to numerically simulate the vortex-induced vibration response of the energy capture structure, and analyze the effects of mass ratio and damping ratio on the vortex-induced vibration response and wind energy conversion efficiency of the wavy conical wind energy capture structure. The results show that the wavy conical energy capture structure with a mass ratio of m*=2 and a damping ratio of ζ=0.05 can obtain a wider lock-in interval and higher energy conversion efficiency. It is also found that the mass damping ratio m*ζ directly affects the energy conversion efficiency, a suitable combination of m*ζ can improve the energy conversion efficiency, with an average energy conversion efficiency of nearly 31% higher at m*ζ=0.10 than at m*ζ=0.05. The research results can provide theoretical support for the improvement of the energy conversion efficiency of bladeless wind turbines.

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    Materials Science and Engineering
    Growth Rates of HFCVD Diamond Films on Silicon Carbide Substrates for Heat Dissipation Applications
    LI Weihan, QIAO Yu, SHU Da, WANG Xinchang
    2023, 57 (8):  1078-1085.  doi: 10.16183/j.cnki.jsjtu.2022.043
    Abstract ( 53 )   HTML ( 2 )   PDF (18057KB) ( 89 )   Save

    Diamond has an extremely high thermal conductivity, making it to have a great potential as a heat dissipation material. Based on the hot filament chemical vapor deposition (HFCVD) technique, diamond thick films were deposited on silicon carbide substrates by using the multi-step method in this paper. The scanning electron microscopy (SEM) and Raman spectroscopy were adopted for characterizing the samples. The influences of filament power, carbon concentration, and reactive pressure on the growth rate and quality of the diamond films were systematically studied. It is found that the diamond film with the best quality is synthesized by adopting a filament power of 1 600 W, a methane/hydrogen flux ratio of 18/300 (nucleation stage) and 14/300 (growth stage), and a reactive pressure of 4 kPa. The corresponding growth rate is 1.4 μm/h.

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    A Visco-Elastoplastic Constitutive Model of Uncured Rubber and Its Finite Element Implementation
    WANG Yinlong, LI Zhao, LI Ziran, WANG Yang
    2023, 57 (8):  1086-1095.  doi: 10.16183/j.cnki.jsjtu.2022.022
    Abstract ( 38 )   HTML ( 3 )   PDF (3592KB) ( 58 )   Save

    In order to investigate the mechanical properties of uncured rubber, uniaxial and cyclic tensile experiments are conducted on uncured rubber at different strain rates. From the experimental results, the rate-dependent nonlinear mechanical behaviors of uncured rubber can be clearly observed. With strain rate increasing, the stress level, hysteresis and Mullins effect get enhanced, and the residual strain decreases. To characterize the nonlinear visco-elastoplastic mechanical behaviors of uncured rubber, a three-network (TN) constitutive model that contains a hyperelastic network and two nonlinear viscoplastic networks is proposed. The eight-chain model is used to characterize the hyperelastic behavior while the Bergstr?m-Boyce flow model is applied in the viscoplastic networks to capture the nonlinear viscous flow. The proposed constitutive model is implanted into the finite element software Abaqus with which, the multistep tensile relaxation test is simulated. The simulation result is satisfactorily consistent with experimental results, which verifies the effectiveness of the TN model. Finally, the simplified molding process of a tire tread is simulated, which further verifies the stability of the TN model.

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    Springback Control of DP1180 Steel Stamping by Variable Closing Pressure
    DING Yuejie, WANG Yiwen, WANG Wurong, WEI Xicheng, ZHAO Yangyang
    2023, 57 (8):  1096-1104.  doi: 10.16183/j.cnki.jsjtu.2021.439
    Abstract ( 62 )   HTML ( 3 )   PDF (28869KB) ( 69 )   Save

    In order to further control the springback of advanced high-strength steel in stamping,a method to reduce the bending springback by increasing the variable closing pressure (VCP) through servo hydraulic equipment without increasing the material forming margin was proposed. For U-shaped benchmark parts of 1 180 MPa dual-phase (DP1180) steel formed by stamping, the feasibility of increasing VCP to control springback was analyzed by using the finite element method, and the mechanism of increasing VCP to reduce springback was studied from the perspective of residual stress and dislocation. The results show that the proposed method can reduce the residual stress and the dislocation density of the formed material, thus increasing the inelastic recovery and achieving the effect of reducing the springback angle of the target part by 22.3%. Because this method is only applied at the end of part forming, which does not affect the plastic flow in the material forming process, there is no need to increase the additional material forming ability and shaping process, which can be applied to actual industry without changing the production rhythm, and has a broad application prospect.

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