Table of Content

    28 January 2022, Volume 56 Issue 1 Previous Issue    Next Issue
    Experimental Study on Condensation of Steam Jet Injection in Submerged Condition
    ZHANG Wei, JIANG Chaofei, YE Ya’nan, WANG Xiaoyan, GONG Zili, HU Chen, XIAO Yao, GU Hanyang
    2022, 56 (1):  1-13.  doi: 10.16183/j.cnki.jsjtu.2020.302
    Abstract ( 855 )   HTML ( 463 )   PDF (10296KB) ( 745 )   Save

    An experimental study is conducted to find the characteristics of steam plume and pressure oscillation on direct contact condensation by a side-hole sparger. Synchronal measuring of transient pressure of the steam plume is gained from the high-speed camera and high-pressure sensor respectively. The influence of steam mass flux and water temperature on direct contact condensation characteristic are presented and its regime map is plotted. Then, the dynamic connections of transient pressure and steam plume in different condensation regimes are analyzed. It is found that high frequency pressure oscillation and the collapse of detached bubbles occur at the same time. Together with the condensing and disappearing process of the collapse of detached bubbles, the intensity of pressure oscillation decays exponentially in a vibration way. The changing trends of steam plume length in condensation oscillation regime and stable condensation regime are also obtained, which shows that the steam plume increases with the steam mass flux and the temperature in the condensation oscillation regime. When entering the stable condensation regime, the steam plume suddenly decreases and then increases with the temperature and the steam mass flux. The research results are useful for the engineering application of sparger in steam emission devices.

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    Test of Critical Heat Flux on Outer Surface of CAP1400 Pressurized Reactor Vessel
    SHI Guobao, ZHENG Mingguang, ZHANG Kun, KUANG Bo, LIU Pengfei
    2022, 56 (1):  14-20.  doi: 10.16183/j.cnki.jsjtu.2020.395
    Abstract ( 725 )   HTML ( 17 )   PDF (3136KB) ( 504 )   Save

    A full height sliced test facility is established based on the modeling process. The heating test section is manufactured by adopting the explosive welding technology, and the surface of carbon steel can simulate the actual surface characteristic of a pressurized reactor. Critical heat flux tests on flow, pressure, subcooling degree, chemical material in water, and surface characteristics are performed on the outer surface of the pressurized reactor vessel. Therefore, the law of heat transfer limit on the outer surface of the CAP1400 pressurized reactor vessel is obtained, and the process of flow and heat transfer for in-vessel retention is validated.

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    A Real-Time Mass Flow Rate Estimation Method of Recirculation Water in Steam Generator of Nuclear Power Plants
    HUI Jiuwu, LING Jun, LUAN Zhenhua, WANG Gaixia, DONG He, YUAN Jingqi
    2022, 56 (1):  21-27.  doi: 10.16183/j.cnki.jsjtu.2020.355
    Abstract ( 849 )   HTML ( 21 )   PDF (1569KB) ( 474 )   Save

    According to its actual structure, the steam generator is divided into the hot leg, the cold leg, the steam-water separator, and the steam chamber, where the hot leg and the cold leg are further divided into a descending channel and an ascending channel. Based on the mass, energy, and momentum conservation laws, the distribution parameter models for the hot leg, the cold leg, the steam-water separator, and the steam chamber are established. Combining the physical parameter database of the working medium and the data collection system (DCS) real-time measurement data, the model is solved in real time and the estimated mass flow rate of recirculation water is obtained. The verification results using the operating data of a CPR1000 nuclear power unit show that the calculated temperature, the pressure, and the mass flow rate of the outlet saturated steam of the steam generator agree well with the measured values, which indirectly verifies the correctness of the estimation approach of recirculation water proposed in this paper.

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    Effect of Nanosecond Pulse Discharge Parameters on Ignition Performance
    LIU Jingyuan, WANG Ning, ZHAO Qingwu, XIONG Yong, CHENG Yong
    2022, 56 (1):  28-34.  doi: 10.16183/j.cnki.jsjtu.2021.033
    Abstract ( 679 )   HTML ( 13 )   PDF (1129KB) ( 653 )   Save

    The discharge characteristics of nanosecond pulse discharge at different pulse voltages and different pulse intervals are investigated based on constant volume bomb. The effects of different discharge parameters on the flame success rate and ignition delay of methane/air mixture are compared. The results show that the coupling between pulses can be reasonably utilized and the utilization rate of discharge energy can be improved by decreasing the pulse interval.The ignition limit of methane/air mixture can be enlarged by increasing the pulse voltage, the pulse number, and decreasing the pulse interval. The ignition delay can be reduced by increasing the pulse voltage and decreasing the pulse interval.

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    Large Eddy Simulation of Partially Premixed Flame with Local Extinction Phenomenon
    ZENG Haixiang, WANG Ping, SHROTRIYA Prashant, JIANG Linsong, MURUGESAN Meenatchidevi
    2022, 56 (1):  35-44.  doi: 10.16183/j.cnki.jsjtu.2019.298
    Abstract ( 670 )   HTML ( 19 )   PDF (5439KB) ( 623 )   Save

    The Sydney partially premixed flame FJ200-5GP-Lr75-103 case with the local extinction phenomenon is studied by large eddy simulation (LES) coupled with the dynamic k equation sub-grid scale model and the dynamic thickened flame (DTF) combustion model. To account for the influence of non-uniform equivalence ratio on the laminar flame speed and thickness, two fitting functions are introduced in the DTF model to automatically adjust these two parameters in the wrinkling functions, according to the local value of mixture fraction in the flow field. The results show that the dynamic k equation model can predict the mixture fraction of the non-uniform premixed gas in the flow field well. In the middle and downstream with more flame extinction, the temperature, the species profiles, and the scatter plot of temperature versus mixture fraction calculated by LES agree well with the experiment data. This demonstrates that the improved DTF model can capture the local extinction phenomenon in partially premixed flame, but for the CO mass fraction, discrepancy between the LES results and experiment data is presented.

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    Analysis of POD and EPOD for Unsteady Flow Field of Wind Turbine Airfoil
    SUN Chong, TIAN Tian, ZHU Xiaocheng, DU Zhaohui
    2022, 56 (1):  45-52.  doi: 10.16183/j.cnki.jsjtu.2020.204
    Abstract ( 707 )   HTML ( 17 )   PDF (3093KB) ( 539 )   Save

    The profile flow around the wind turbine airfoil has a significant impact on the overall performance and the noise of a wind turbine. In this paper, a combination method of large eddy simulation (LES) and the solution of Ffowcs Williams and Hawkings (FW-H) equation is used to obtain the unsteady flow field and the far-field aeroacoustic noise of a wind turbine airfoil. The dominant modes of the unsteady vorticity at the angle of attack of 8° are extracted by the proper orthogonal decomposition (POD). The modal structure of the dominant modes indicates that the trailing edge vortices and the laminar separation bubble are the main unsteady feature of the airfoil flow. The modal structures most related to the far-field aeracoustics noise are obtained by the extend proper orthogonal decomposition (EPOD). The modal results show that the vortices in the boundary layer and the large-scale vortices in the wake are most relevant to the generation and propagation of the aeracoustics noise.

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    Formation Law of Surface Defects in Stretch-Bending Formamtion of Aluminum Trim Strip for Automobile Body
    ZHENG Gaoyuan, ZHAO Yixi, CUI Junhui
    2022, 56 (1):  53-61.  doi: 10.16183/j.cnki.jsjtu.2020.323
    Abstract ( 634 )   HTML ( 43 )   PDF (15592KB) ( 417 )   Save

    Surface defects refer to the local undulation of the parts in the forming process. The variable cross-section and variable-curvature aluminum trim parts are prone to local surface defects during the stretch-bending process, which has a great impact on the appearance of the whole vehicle. Research on the formation mechanism of surface defects has important guiding significance for the prevention and control of surface defects. In this paper, the formation mechanism of the deformation defects of the stretch-bending forming surface of aluminum trim is studied, the stretch-bending forming test and the surface defects measurement are conducted, and the simulation model of the stretch-bending forming of aluminum trim is established by using the Abaqus software platform. In addition, the forming process of surface defects is analyzed. The results show that when the ratio of section width to bending radius is larger than 35%, the part will have a warping tendency, and the joint action of section shape, upper die, and padding will cause local surface defects.

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    Numerical Simulation of Stagger Spinning of Cylindrical Part with Cross Inner Ribs
    ZHOU Yu, ZHAO Yong, YU Zhongqi, ZHAO Yixi
    2022, 56 (1):  62-69.  doi: 10.16183/j.cnki.jsjtu.2020.326
    Abstract ( 739 )   HTML ( 45 )   PDF (5571KB) ( 506 )   Save

    Flow spinning is an advantageous technology in forming thin-walled cylindrical parts, but for cylindrical parts with inner ribs,the height of the inner ribs that can be formed is limited. Aimed at the problem that the inner ribs are difficult to fill in such components, a numerical simulation model of staggered spinning of thin-walled cylindrical parts with cross inner ribs is established based on Abaqus, and the influence of the number of rollers on the filling of inner ribs is analyzed. The process test of the cylinder part with orthogonal inner ribs is conducted. The results show that in the staggered spinning process, increasing the number of rollers will reduce the diameter expansion of the aluminum alloy cylindrical part with inner ribs, and inhibit the axial flow of materials, leading to a higher geometric accuracy of the inner ribs. The comparison of the simulation results and the test results shows that the average error of the inner rib filling fullness of simulation result is 11.3%, and the simulation model has a good reliability.

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    Adaptive Transferring Method of Digital Twin Model for Machining Domain
    SHEN Hui, LIU Shimin, XU Minjun, HUANG Delin, BAO Jingsong, ZHENG Xiaohu
    2022, 56 (1):  70-80.  doi: 10.16183/j.cnki.jsjtu.2021.167
    Abstract ( 939 )   HTML ( 44 )   PDF (6512KB) ( 668 )   Save

    In the multi-variety and small batch manufacturing workshop, digital twin model is mostly established for specific scenarios. Due to its lack of adaptive ability under working conditions, the prediction accuracy of machining quality is insufficient. To solve this problem, an adaptive transferring method of the digital twin model is proposed. By building the transferable digital twin model, the online prediction of machining quality based on the fusion of mechanism and algorithm model is realized. The transferring process and strategy of the digital twin model are proposed. Based on the analysis and calculation of characteristic data, the source model to be transferred is selected. At the same time, in combination with the transfer learning theory, the transfer of digital twin models is realized under simple and complex changing conditions. Taking drilling as an example, the drilling experiment platform is built and the feasibility of digital twin model transfer is verified. The results show that the model can keep the mean absolute error of prediction less than 1.5% under changing working conditions. This method provides a new idea to improve the adaptive ability of digital twin models.

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    An Inverse Optimization Approach of Vehicle Routing Problem
    CHEN Yuyi, CHEN Lu
    2022, 56 (1):  81-88.  doi: 10.16183/j.cnki.jsjtu.2020.210
    Abstract ( 935 )   HTML ( 29 )   PDF (1978KB) ( 529 )   Save

    Generally, experienced drivers or experts do not always follow the shortest path in the last mile delivery of e-commerce. Hence, an inverse optimization approach was proposed to obtain a proper cost matrix by learning from the experts’ past experience. Thus, the routing model with respect to the learned cost matrix could provide solutions as good as those given by experts. An algorithm-based multiplicative weights updates algorithm was applied to achieve the experience learning process. The experimental analyses based on the random and real-life instances demonstrate the effectiveness of this approach.

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    Multimodal Fusion Classification Network Based on Distance Confidence Score
    ZHENG Dezhong, YANG Yuanyuan, HUANG Haozhe, XIE Zhe, LI Wentao
    2022, 56 (1):  89-100.  doi: 10.16183/j.cnki.jsjtu.2020.186
    Abstract ( 868 )   HTML ( 99 )   PDF (3505KB) ( 625 )   Save

    Multimodal data modeling can effectively overcome the problem of insufficient information in a single mode and can greatly improve the performance of model. However, not much progress has been made in quantifying the confidence of neural network models, especially for multimodal fusion models. This paper proposes a method based on embedding, which calculates the local density estimation in the embedding space by calculating the distance between samples, and then calculates the confidence score of the model. The proposed method is scalable and can be used not only for a single modal model, but also for the confidence measurement of multimodal fusion model. In addition, it can also evaluate and quantify the influences of different modal data on the multimodal fusion model.

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    Influence of Distributed Leading-Edge Roughness on Stall Characteristics of NACA0012 Airfoil
    LI Yi, BAI Junqiang, ZHANG Yanjun, ZHAO Ke
    2022, 56 (1):  101-113.  doi: 10.16183/j.cnki.jsjtu.2020.324
    Abstract ( 813 )   HTML ( 72 )   PDF (4986KB) ( 582 )   Save

    The influence of the distributed leading-edge roughness on the stall characteristics of NACA0012 airfoil is analyzed in full turbulence flow or transition flow. The Menter shear-stress transport model and the $\gamma - \overline{Re_{\theta t}}$($\overline{Re_{\theta t}}$ is transition momentum-thickness Reynolds number, γ is intermittency)transition model are used to simulate the flow around the airfoil by coupling the roughness model and the roughness amplification factor transport equation respectively. The airfoil stall characteristics and the pre-stall boundary layer development are analyzed. The results show that the trailing-edge stall occurs for the NACA0012 airfoil in full turbulence flow, and the stall characteristic is not changed by the leading-edge roughness. The maximum lift coefficients are significantly decreased with the leading-edge roughness at a lower angle of attack. In transition flow, the leading-edge roughness inhibits the formation of leading edge laminar separation bubbles, and the stall characteristic of airfoil is changed from leading-edge stall to trailing-edge stall. The maximum lift coefficient is significantly increased with the leading-edge roughness at a higher angle of attack.

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    Explicit Buckling Analysis of Rotationally Restrained Plates on Rigid Base Under Various Loading Conditions
    WU Tao, MO Shixu, XIANG Yongbin, ZOU Zequn, ZHENG Yan
    2022, 56 (1):  114-126.  doi: 10.16183/j.cnki.jsjtu.2020.353
    Abstract ( 688 )   HTML ( 19 )   PDF (4340KB) ( 543 )   Save

    In order to investigate the unilateral buckling behavior of rectangular plates with different elastic rotational restraint stiffnesses on the rigid foundation, the buckling of rectangular plates with elastic rotation constraints on the rigid foundation under linear pressure and uniform shear force is studied. According to the buckling deformation under different loading conditions, the appropriate deflection surface function is proposed, and the theoretical solution to critical buckling load is deduced from the energy variation of plate buckling by using the Rayleigh-Ritz method. The buckling formula of the thin plate at the combined bending-shear stress is obtained by using the correlation stability checking formula. A finite element model is established to analyze the influence of different base stiffnesses and bending-shear ratios on the bending shear composite buckling stress. The results are compared with the web buckling test result of a semi filled steel box concrete composite beam in the negative moment region. The results show that the rigid foundation of semi filled concrete can be simplified as an elastic foundation with a stiffness coefficient slightly lower than 5.

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