Table of Content

    28 February 2019, Volume 53 Issue 2 Previous Issue    Next Issue
    Influence of Main Steam Temperature and Pressure Fluctuations on the Creep-Fatigue Damage of a Steam Turbine Rotor
    ZHAO Nailong,WANG Weizhe,LIU Yingzheng
    2019, 53 (2):  127-133.  doi: 10.16183/j.cnki.jsjtu.2019.02.001
    Abstract ( 1230 )   PDF (1793KB) ( 401 )   Save
    The finite element software Abaqus is adopted to construct an axisymmetric finite element model of a high-pressure rotor of a 1000MW ultra-super critical steam turbine. The boundary conditions are determined based on the in-service steam temperature and pressure data from the power plant. After finite element calculation, the rotor mechanical behavior in the steady operation is analyzed, and the Lemaitre continuum damage model is further applied to study the creep-fatigue damage of the rotor. In addition, the calculating results without consideration of the steam temperature and pressure fluctuations are used for comparison. The results show that the fluctuations of the steam temperature and pressure exert a great influence on the thermo-mechanical behavior of the rotor; the temperature and stress of the rotor keep changing with the steam temperature and pressure; the creep-fatigue damage in the inlet area under the in-service conditions is more than double that under constant steam temperature and pressure conditions.
    References | Related Articles | Metrics
    Experimental Investigation of Convective Heat Transfer Coefficient of Fe3O4/Water Nanofluids in the Presence of the Magnetic Field Under the Turbulent Flow Regime Conditions
    SHA Lili,JU Yonglin,ZHANG Hua
    2019, 53 (2):  134-139.  doi: 10.16183/j.cnki.jsjtu.2019.02.002
    Abstract ( 900 )   PDF (1748KB) ( 374 )   Save
    The effect of magnetic field on the convective heat transfer of Fe3O4/Water nanofluids was experimentally studied. The Fe3O4/Water nanofluids flowed through a horizontal circular tube under the turbulent flow regime conditions. The pressure drop of Fe3O4/Water nanofluids was measured at volume fraction of 3%. The mechanism of the heat transfer of magnetic nanofluids under the magnetic field was discussed. The experimental results showed that the heat transfer coefficient increased with the increase of the Fe3O4/Water nanofluids concentration, and the maximum averaged enhancement was 4.3%. In the presence of the perpendicular uniform magnetic field, almost no obvious enhancement of the convective heat transfer coefficient of Fe3O4/Water nanofluids was observed in fields up to 23.809 and 39.682kA/m but it was observed in fields of intensity up to 63.492kA/m. The maximum averaged enhancement was 3%. Compared with the pressure drop of the distilled water, 50% enhancement was observed using Fe3O4/Water nanofluids at the volume fraction of 3%. Enhancement was also obtained under the applied magnetic field and the maximum averaged enhancement was 11.3%. The power ratio was less than 1, and thus the utilization of Fe3O4/Water nanofluids in heat transfer could not save energy.
    References | Related Articles | Metrics
    Refrigerant Distribution and Application Research of Parallel Flow Evaporator for Bus Air Condition
    YU Dengjia,CHEN Jiangping
    2019, 53 (2):  140-145.  doi: 10.16183/j.cnki.jsjtu.2019.02.003
    Abstract ( 1276 )   PDF (3113KB) ( 398 )   Save
    Microchannel heat exchangers (MCHX) have been widely used in automotive air conditioning system due to their advantages of compactness and higher efficiency. However,there are still issues that need to be overcome due to the slender structure of bus air conditioning, such as the uneven flow distribution of refrigerant and condensed water. A new refrigerant distribution way has been investigated to verify the feasibility and advantages of parallel flow evaporator application in bus air conditioning. Results show that by separate the refrigerant in front of the expansion valve and use four expansion valve control the superheat of each evaporator, the outlet temperature of each evaporator are 11.5, 12.6, 14.2, 11.0℃ respectively. Evaporator outlet temperature uniformity is better than the system with liquid-distributor which are 7.9, 23.3, 13.3, 15.3℃ respectively.
    References | Related Articles | Metrics
    Evaluation of Travel Time Reliability for Bus Passenger Based on Mixed Logit Model
    NI Anning,LIU Yanchen,CUI Yuwei,LU Junli
    2019, 53 (2):  146-152.  doi: 10.16183/j.cnki.jsjtu.2019.02.004
    Abstract ( 1045 )   PDF (1222KB) ( 326 )   Save
    Appropriate evaluation of traveler’s travel time reliability is important for understanding how the reliability influences traveler’s choice decision. Combined with SP survey design, two kinds of reliability criteria are applied and a questionnaire program which includes different decision scenes is proposed to study the characteristics of bus travelers’ evaluation of travel time reliability in the context of morning peak in Tianjin city. Questionnaire program is able to generate daily travel situations which are familiar to each respondent automatically. Mixed logit model is applied. The results provide the distribution of willingness to pay for the travel time reliability of travelers and the relation between reliability preference and different social economical characteristics. Furthermore, the results are also helpful for calculating the benefits of reliability improvement in transportation construction program, and provide meaningful references for TDM policies making.
    References | Related Articles | Metrics
    Fatigue Life Prediction of a Hatch Corner Based on the Spectral Analysis and Fatigue Crack Growth Approaches
    YU Honggan,HUANG Xiaoping,ZHANG Yongkuang
    2019, 53 (2):  153-160.  doi: 10.16183/j.cnki.jsjtu.2019.02.005
    Abstract ( 1071 )   PDF (3659KB) ( 376 )   Save
    Hatch corner is a typical stress concentration area in a large opening ship, and is a crucial structure detail for fatigue assessment. In this paper, an elliptic hatch corner ahead of the cabin in an ultra large container ship was taken as an example to research the assessment of the fatigue life of hatch corner based on the spectral analysis and fatigue crack growth method. Firstly, the hydrodynamic and structural response analysis were performed to get the whole ship’s structural responses and the stress distribution in the hatch corner under different loading conditions, and then determine the possible crack initiation positions on the hatch corner. Secondly, the analysis results were taken as boundary conditions of FE hatch corner model with crack which is built via ANSYS, SIF (Stress Intensity Factor) was obtained. Taking the maximum circumferential stress criterion (MCSC), propagation paths of crack in the hatch corner under different load cases were gotten, then regression was used to establish a corresponding empirical formula of SIF based on a large series of analysis. Finally, the spectral analysis approach recommended by ABS was adopted to construct the fatigue load spectrum, and the Single Curve Model and the proposed empirical formula were used to predict the fatigue life of the hatch corner. The results could provide a reference for fatigue assessment of hatch corner.
    References | Related Articles | Metrics
    Coupled Sound Field Calculating Method for Ship Underwater Noise Excited by Multiple Categories of Vibration and Sound Sources
    LI Qing,YU Han,YANG Deqing
    2019, 53 (2):  161-169.  doi: 10.16183/j.cnki.jsjtu.2019.02.006
    Abstract ( 1254 )   PDF (4028KB) ( 636 )   Save
    Aiming at a frigate model based on the DTMB 5415 hull form, a coupled sound field calculating method for ship underwater radiation noise in low-middle frequencies was discussed by considering three typical categories of vibration and sound sources, mechanical, propeller and hydraulic noise. A vibroacoustic coupling FEM-IBEM (the finite element method-indirect boundary element method) model for the frigate was established, and the front 40000 order modes were calculated as the modal basis for the acoustic response. This study then calculated the acoustic radiated power level in 0-500Hz and analyzed directional properties and spectral characteristics for every noise component, and it compared the differences between the direct superposition and the coupled sound field calculating methods. The research shows that the physical model of the coupled method is more exact and efficient, and it is a preferred method for ship underwater radiation noise numerical prediction in low-middle frequencies excited by multiple categories of vibration and sound sources.
    References | Related Articles | Metrics
    The Analysis of Nominal Wake Flow Characteristics in Short Wave
    GUO Chunyu,LIU Tian,ZHAO Qingxin,HAO Haohao
    2019, 53 (2):  170-178.  doi: 10.16183/j.cnki.jsjtu.2019.02.007
    Abstract ( 1032 )   PDF (5488KB) ( 336 )   Save
    KCS standard ship model was studied as the object of this paper. The numerical calculation by using Reynolds Averaged Navier-Stokes method is mainly for the variation of the constraint model’s nominal wake field in a short regular wave encounter period, and its features are analyzed. The calculation results show that time history of axial nominal wake fraction is the same as the periodic variation of the incident wave. The variation of the wave wake fraction in a single wave period is relatively small, however, the impact of wave cannot be ignored. The main cause of wave wake fraction in negative value is the wave drift in the direction of the wave direction, which approximately equals to the total average flow. When the wave crest and wave trough is located at the propeller disk, axial nominal wake field change is always the most obvious, and the degree of change significantly affected by the wave steepness, and the decreases of wave length has a certain influence on the below of the propeller disk.
    References | Related Articles | Metrics
    Water Entry of an Elastic Wedge Based on a Semi-Analytical Slamming Model
    YU Pengyao,ZHAO Yong,WANG Tianlin,ZHEN Chunbo,SU Shaojuan
    2019, 53 (2):  179-187.  doi: 10.16183/j.cnki.jsjtu.2019.02.008
    Abstract ( 1174 )   PDF (1220KB) ( 304 )   Save
    A fluid-structure coupled method for the dynamic response of the elastic wedge during the water entry is established based on a semi-analytical slamming model. By comparing the calculation results with different mesh densities, time steps and mode numbers, it is shown that the proposed method has better convergence. The correctness of the method is verified by comparing it with the results of commercial software and literature. Compared with the hydroelastic analysis method based on the Wagner model, this method can reasonably predict the structural response before and after flow separation. The structural responses by the coupling method and decoupling method under different impact velocities are compared and analyzed, and the importance of fluid-structure interaction is further revealed.
    References | Related Articles | Metrics
    Optimization Model for Integrated Quay Cranes and Yard Trucks Scheduling Based on Double Cycling
    ZHANG Xiaoju,ZENG Qingcheng,CHEN Zigen,LI Taoying
    2019, 53 (2):  188-196.  doi: 10.16183/j.cnki.jsjtu.2019.02.009
    Abstract ( 1195 )   PDF (931KB) ( 395 )   Save
    To solve the integration problems when quay cranes are applied with double cycling and increase the speed of turn-around of containers in the container terminal, this paper researched in the integrated scheduling of quay cranes and trucks. An integrated scheduling model with the objective to minimize the makespan of the ship was developed. The task assignment and scheduling of quay cranes and trucks are optimized by the proposed model. Compared with traditional operations, double cycling increases the working stage of trucks and increases the difficulty of solving this problem. An algorithm based on heuristic rules was designed to solve large scale problems and results are compared with those obtained by low bounds. Results show that the proposed algorithm can increase the speed of solving the model. The integrated scheduling of quay cranes and trucks contributes to increasing the speed of double cycling of quay cranes and thereby provide theories for the container terminal.
    References | Related Articles | Metrics
    Pallet Detection Based on Contour Matching for Warehouse Robots
    WU Wenhan,YANG Ming,WANG Bing,WANG Chunxiang
    2019, 53 (2):  197-202.  doi: 10.16183/j.cnki.jsjtu.2019.02.010
    Abstract ( 1633 )   PDF (3924KB) ( 761 )   Save
    Pallet detection is the key step of cargo handling for warehouse robots. A pallet detection method based on point clouds plane contour matching is proposed to solve the current detection method problems that are not robust to illumination and relative position between the pallet and sensor. Point clouds generated by time-of-flight (ToF) camera are filtered and segmented to different planes using region-growing method constrained by surface normal. Then point clouds are projected to the grid image along the plane’s principle normal direction. Fusion contour feature of Hu moment invariants and scale feature extracted from grid image contour is applied for similarity matching between the target and template pallet contour. The experimental results show that the method has high recognition rate and strong robustness under the circumstance of complex illumination, uncertain distance and relative pose between the pallet and sensor.
    References | Related Articles | Metrics
    Global Localization for Intelligent Vehicles Using Ground SURF
    HU Bing,YANG Ming,GUO Lindong,WANG Chunxiang,WANG Bing
    2019, 53 (2):  203-208.  doi: 10.16183/j.cnki.jsjtu.2019.02.011
    Abstract ( 1146 )   PDF (2367KB) ( 449 )   Save
    Global localization is essential for intelligent vehicles as navigating on the urban road. Generally, visual localization methods are based on semantic landmarks such as lanes and stop-lines which are easily interfered by other semantic landmarks, such as arrows and zebra crossing. To solve the problem, a new global localization method using ground speeded up robust features (SURF) is proposed in this paper. Firstly, SURF extracted from bird-eye view images are fused with high-precision GPS data to create a priori map. Then, SURF extracted online are matched with the map to estimate the global localization using the iterative closest point (ICP) algorithm. Finally, the global localization is fused with other sensors data by the extented Kalman filter (EKF) for better accuracy. Experiment results show that localization can reach decimeter-level accuracy, which can meet the demand for intelligent vehicles.
    References | Related Articles | Metrics
    Adaptive Robust Control Strategy of Valve Controlled Asymmetric Cylinder Position Control System
    HE Changyu,SHI Guanglin,GUO Qinyang,WANG Dongmei
    2019, 53 (2):  209-216.  doi: 10.16183/j.cnki.jsjtu.2019.02.012
    Abstract ( 1222 )   PDF (1224KB) ( 394 )   Save
    A robust adaptive control strategy was proposed to improve the robustness and enhance the position tracking accuracy of valve controlled asymmetric cylinder position system with unknown nonlinearities and uncertain parameters. Dynamic surface control technique was introduced to avoid the inherent “explosion of complexity” problem of the traditional back stepping method, and the design process of the nonlinear controller could be simplified. By combining a discontinuous projection operator, the unknown parameters could be estimated effectively. The stability of the closed loop system was analyzed by using Lyapunov stability theory, and the simulation results have verified the effectiveness of the proposed control method.
    References | Related Articles | Metrics
    Diesel Engine Fault Online Diagnosis Method Based on Incremental Sparse Kernel Extreme Learning Machine
    LIU Min,ZHANG Yingtang,LI Zhining,FAN Hongbo
    2019, 53 (2):  217-224.  doi: 10.16183/j.cnki.jsjtu.2019.02.013
    Abstract ( 976 )   PDF (3695KB) ( 294 )   Save
    In order to realize online fault diagnosis of diesel engine, a fast online diagnosis method based on incremental sparse kernel extreme learning machine (ISKELM) was proposed. Aiming at the problem of sample sparseness and model expansion in kernel online learning process, a sparse kernel function matrix construction strategy based on instantaneous information measurement was proposed. In the strategy, sample forward sparseness and backward deletion are implemented according to the principle of minimizing dictionary redundancy and maximizing the self information of dictionary elements. Then the dictionary is expanded and pruned online under the best order. So a diagnosis model with limited order and sparse structure is established. In order to solve the updating problem of the model kernel weight matrix, a method consisting of sample addition learning algorithm and improved sample reduction learning algorithm was put forward. It reduces the computational complexity and improves the online updating speed of the diagnosis model. UCI standard data and diesel engine fault data classification experiment results indicate that compared with several existing online diagnosis methods, ISKELM not only has high classification accuracy, but also greatly improves the online modeling speed, and it realizes diesel engine fault online diagnosis more quickly and accurately.
    References | Related Articles | Metrics
    Analysis of Dynamic Workspace for Under-Constrained Coordinate Suspending System with Multi-Robots
    SU Cheng,YE Jianan,LI Wei,DING Wangcai,ZHAO Zhigang
    2019, 53 (2):  225-231.  doi: 10.16183/j.cnki.jsjtu.2019.02.014
    Abstract ( 916 )   PDF (819KB) ( 410 )   Save
    For the under-constrained system that multi-robots cooperatively tow a payload by cables, the dynamic workspace can’t be found out by the principle of vector closure. The dynamic equations of the system were established by using the Newton-Euler equation. Then the geometric meaning of Farkas and Stiemke lemma and relationship with the dynamic equations of the system were introduced, and the solving of dynamic workspace was converted to the problem that whether there exists a hyper plane. For the under-constrained system, the dynamic equations also need to be split to get the dynamic workspace. Finally, simulations were conducted to validate the feasibility of the proposed method by Monte Carlo method, it validates that the payload acceleration has little effect on the dynamic workspace by comparing the two groups of simulation.
    References | Related Articles | Metrics
    Firefly Algorithm with High Precision Mixed Strategy Optimized Particle Filter
    BI Xiaojun,HU Songyi
    2019, 53 (2):  232-238.  doi: 10.16183/j.cnki.jsjtu.2019.02.015
    Abstract ( 1104 )   PDF (973KB) ( 422 )   Save
    Aiming at the problem of the low precision and slow convergence rate of particle filters based on intelligent optimization algorithms, this paper came up with a firefly algorithm with mixed strategy optimized particle filter. The algorithm is applied to the chaotic perturbation search strategy in the firefly optimization mechanism for balancing the particle optimization ability effectively, and proposed dynamic visual search strategy to improve the utilization ratio of particles moving toward high likelihood regions. At the same time, according to the particle filter mechanism, a new fluorescence luminance formula is designed to expand the observation information for improving the particles quality. Experiment results show that the proposed algorithm effectively improves the accuracy and speed of the intelligent optimization particle filter for nonlinear system state estimation.
    References | Related Articles | Metrics
    Estimation of Panicle Seed Number Based on Panicle Geometric Pattern Recognition
    MA Zhihong,GONG Liang,LIN Ke,MAO Yuhan,WU Wei,LIU Chengliang
    2019, 53 (2):  239-246.  doi: 10.16183/j.cnki.jsjtu.2019.02.016
    Abstract ( 980 )   PDF (5806KB) ( 360 )   Save
    School of Mechanical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
    References | Related Articles | Metrics
    Surface Modification of Austenitic Stainless Steel Bipolar Plates by Low Temperature Colossal Supersaturation Gaseous Carburization
    JIANG Yong,LI Yang,ZHOU Yang,GONG Jianming
    2019, 53 (2):  247-252.  doi: 10.16183/j.cnki.jsjtu.2019.02.017
    Abstract ( 1093 )   PDF (1442KB) ( 300 )   Save
    By the means of low temperature colossal supersaturation gaseous carburization (LTCSGC) technique, a carburizing layer of 30 μm was formed on the surface of 316L austenitic stainless steel bipolar plate. The carbon concentration, compressive residual stress, nano-hardness and the phase structure along cross-sectional depth direction of the specimens were investigated, respectively. Besides, the contact resistance of carburized 316L stainless steel bipolar plates was measured and the corrosion resistance of the samples in simulated proton exchange membrane fuel cell (PEMFC) environment was analyzed. Results demonstrate that the LTCSGC layer was a functionally gradient material which was composed of expanded austenite. Moreover, its carbon concentration, residual stress and hardness decline continuously along cross-sectional depth direction from surface to substrate. Compared with 316L stainless steel bipolar plates, the contact resistance of carburized samples after LTCSGC treatment was reduced by 34%. The self-corrosion potential in PEMFC anode environment was improved to -79mV, which was higher than the PEMFC work potential (-0.1V). Therefore, it was protected by cathode. In PEMFC simulated cathode environment, the self-corrosion potential was increased by 260mV and the corrosion resistance was remarkably improved. Meanwhile, the potentiostatic polarization etching current density was reduced by 75%.
    References | Related Articles | Metrics