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    Boiler Technology
  • Boiler Technology
    Hydrodynamic Calculation and Wall Temperature Safety Analysis of a 700℃ Ultra Supercritical Opposed Firing Boiler with Spiral Tubes
    WAN Li, ZHU Chao, WU Pengju, NIU Tiantian, LI Yinlong, YANG Dong
    2020, 40(12): 949-957. https://doi.org/10.19805/j.cnki.jcspe.2020.12.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To achieve reliable operation of a 700℃ ultra supercritical boiler with high-temperature heating surfaces, a hydrodynamic calculation program suitable for ultra supercritical boilers was developed based on the network model for nonlinear flows, and subsequently the calculation results were compared with actual operation data of similar boilers to verify the reliability of the program. According to the structure features of the 700℃ ultra supercritical opposed firing boiler with spiral tubes, the water wall tubes and various headers were respectively simplified as equivalent flow loops and pressure nodes, based on which, the water wall pressure drop, the flow distribution, the fluid temperature distribution at furnace outlet and the wall temperature distribution along furnace height were calculated at 100%BMCR, 50%BMCR and 30%BMCR load, respectively. Results illustrate that the metal temperature of water wall is within the allowable range of the material at different loads, and the hydrodynamic performance of the 700℃ ultra supercritical opposed firing boiler with spiral tubes is proved to be safe and reliable.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Research and Selection on Parameters and Thermodynamic Schemes of Small Steam Turbines with High Parameters
    LI Ximing, TANG Zhenhe
    2020, 40(12): 958-964. https://doi.org/10.19805/j.cnki.jcspe.2020.12.002
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    Based on the principle of thermodynamics, the relations of actual cycle efficiency with ideal cycle efficiency and internal efficiency of a steam turbine were derived, while the relationship between the ideal cycle efficiency and main steam parameters was deduced. The concept of non-dimensional relative volume flow number was proposed, and the the small volume flow was defined and measured, while the internal efficiency at small flow rate was improved by adopting the small enthalpy degradation and high speed scheme. Results show that considering the actual cycle efficiency, safety and cost performance, the main steam temperature of the small steam turbine should be 535℃. Considering the nagative effect of the increase of main steam pressure on the internal efficiency, the main steam pressure of 50 MW and below steam turbines should not exceed 8.83 MPa. The steam pressure could be increased to 13.24 MPa by using the single-reheat two-cylinder double-speed scheme, when the actual cycle efficiency of the unit could be improved by 15% at most.
  • Steam Turbine and Gas Turbine
    Modeling and Dynamic Simulation of a Blast Furnace Gas-Steam Combined Cycle System
    REN Yuning, SHEN Jiong, ZHANG Junli
    2020, 40(12): 965-974. https://doi.org/10.19805/j.cnki.jcspe.2020.12.003
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    To further study the dynamic characteristics of a blast furnace gas combined cycle system, according to the working mechanism and specific structural parameters of the gas-steam combined cycle system, a dynamic mathematical model was established for the system on Matlab/Simulink platform, based on which, dynamic simulations were performed under the step disturbance of fuel composition, fuel bypass valve opening and IGV opening. Results show that the fluctuation of fuel calorific values has certain effects on the thermal parameters of the combined cycle; the degree of IGV opening has a great effect on the exhaust temperature, and its influence on the steam turbine output can not be neglected.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Wind Turbine Blade Surface Damage Identification Based on Blade Surface Dirt Pretreatment and CNN
    LIN Feng, GUO Peng, LIU Xubin
    2020, 40(12): 975-981. https://doi.org/10.19805/j.cnki.jcspe.2020.12.004
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    To detect the damages hidden under the dirt on blade surface more effectively, a fault diagnosis method was proposed based on the pretreatment of dirt on blade surface and the convolutional neural network (CNN). The robust principal component analysis (RPCA) was used to preprocess the image of the blade with surface dirt, and then the damage feature extraction process was transformed into a convex optimization problem to be solved, thus to obtain the damage feature of the blade, while the CNN was trained with actual blade images taken by unmanned aerial vehicle (UAV). Finally, the trained CNN was used to identify the blade images preprocessed by RPCA and to determine the specific type of damages. Results show that the method proposed can help to indentify the damage of blades with surface dirt, which is proved to be effective by practical applications.
  • Monitoring and Measurement
    Early Fault Diagnosis of Fan Rolling Bearings Based on RSBLMD Algorithm
    MA Tianting, SUN Zhenbo, DENG Minqiang, DENG Aidong
    2020, 40(12): 982-987. https://doi.org/10.19805/j.cnki.jcspe.2020.12.005
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    To diagnose the early fault of rolling bearings, an algorithm was proposed on the basis of rational spline based local mean decomposition (RSBLMD), which was applied to the analysis of early weak faults of rolling bearings. Firstly, an improved rational spline interpolation algorithm was introduced to construct the envelope curve. Then, the RSBLMD algorithm was developed and used to decompose the measured vibration signals into a series of product functions (PF). After that, the effective component that contains the most fault information among the decomposition results was selected based on the kurtosis. Finally, through analysis on the envelope spectrum of the effective component, early fault diagnosis of rolling bearing was achieved. Results show that the method proposed has higher decomposition accuracy, which can help to identify the early fault of rolling bearings precisely.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Numerical Analysis of Spray Motion and Evaporation Characteristics in a Supersonic Two-stage Suspension Flame Spray Process
    LIAN Jiageng, YE Xin, SHAN Yanguang
    2020, 40(12): 988-994. https://doi.org/10.19805/j.cnki.jcspe.2020.12.006
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    Taking the supersonic two-stage suspension flame spray process as an object of study, a two-phase flow and heat transfer model was established using numerical method to simulate and analyze the atomization, motion and evaporation behavior of the suspension, as well as the precipitation and motion heating process of solid particles. Results show that as the mass flow of nitrogen increases, the temperature of the jet decreases along the center axis, but the flow rate does not change. When the volume flow of the suspension injected in radial direction is about 100 mL/min, the suspension can penetrate into the center of the jet, in which case, the effects of both the atomization and evaporation are the best. At the injection angle of -15°, the particle size could be significantly reduced, and the number of particles reaching the substrate in liquid form would be cut down, thereby improving the quality of the coating.
  • Engineering Thermophysics
    Numerical Simulation on the Motion of Particles Under Synergistic Action of Streaming-induced Drag Force and Acoustic Radiation Force
    YANG Yanfeng, JIANG Genshan, LIU Yuechao, JIANG Yu, YU Miao
    2020, 40(12): 995-1001. https://doi.org/10.19805/j.cnki.jcspe.2020.12.007
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    Considering the streaming-induced drag force and acoustic radiation force acting on the particles, a dynamic model was established for the micro particles in the plane standing wave sound field of a two-dimensional channel. The second-order acoustic streaming field was solved by the numerical method of separating time scale, and the reliability of the numerical model was verified by comparing the classical Rayleigh streaming field with the simulated second-order acoustic streaming field. On this basis, the time-average sound field force was coupled to the particle motion equation to study the motion behavior of particles under the synergistic action of streaming-induced drag force and acoustic radiation force. Results show that there exists a critical diameter of dcrit=160 μm under the action of standing wave sound field of 150 dB and 1 000 Hz. When the size of particle is less than dcrit, the motion of particles would be mainly controlled by streaming-induced drag force, which would be of the eddy type. When the size of particles is not less than dcrit, the motion of particles would be mainly controlled by acoustic radiation force, and the particles would gradually converge at the position of sound pressure nodes. With the increase of particle size, the main force controlling the motion of particles gradually changes from streaming-induced drag force to acoustic radiation force, while the velocity of particles increases gradually.
  • Engineering Thermophysics
    Simulation of Sessile Droplet Evaporation Based on Dynamic Contact Angle
    DONG Baiyang, SHAN Yanguang, WENG Zhihao
    2020, 40(12): 1002-1007. https://doi.org/10.19805/j.cnki.jcspe.2020.12.008
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    To improve the present evaporation model that mainly carries out staged simulation for each evaporation mode, a new model was proposed by introducing the dynamic contact angle to achieve continuous simulation on the conversion of sessile droplets from constant contact radius (CCR) mode to constant contact angle (CCA) mode. The model was then used to simulate the evaporation process of sessile droplets at different dynamic contact angles, following which, the simulation results were compared with actual measurements. Results show that when the initial contact angle is relatively small, the droplet evaporation rate decreases linearly; whereas when the initial contact angle is relatively large, the droplet evaporation rate decreases nonlinearly. In the stable stage of evaporation, the Marangoni convection dominates the internal flow of the droplet, and when the evaporation tends to be completed, the influence of natural convection on the internal flow of the droplet gradually enhances and eventually takes the leading role.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Effects of Magnesium Ion in Slurry on the Reaction Characteristics of Flue Gas Desulfurization
    LIU Gaojun, CAI Xiangdong, LI Xiaohui, GUO Yue, LI Qing
    2020, 40(12): 1008-1013. https://doi.org/10.19805/j.cnki.jcspe.2020.12.009
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    A laboratory bench was set up to simulate the desulfurization reaction under different mass concentration of magnesium ion, and to comparatively study the effects of the ion flow rate on the desulfurization reaction. Results show that the magnesium ion can inhibit the crystallization process of gypsum. Specifically, the low concentration of magnesium ions (< 2.40 mg/L) could mainly inhibit the formation of gypsum crystal nucleus in the early stage, while the high concentration (> 3 000 mg/L) would delay the growth of gypsum crystal in the later stage. When the concentration of magnesium ion is less than 0.48 mg/L, the content of median particles in slurry increases, while the distribution range of particle size reduces, which is conducive to the dehydration of gypsum slurry; whereas when the concentration of magnesium ion lies in 3 000-12 000 mg/L, the law of change is opposite. When trace amounts of magnesium ions are added, a smaller number of acicular crystals would form in gypsum, which have little effects on the dehydration of slurry gypsum; whereas when mass amounts of magnesium ions are added, the number of acicular crystals in gypsum would increase obviously, which could improve the water holding capacity of the slurry, thus favoring the dehydration of the slurry.
  • Environmental Protection Technology and Equipment
    Effect of Microwave Discharge on Simultaneous Desulfurization and Denitrification of Activated Coke at Different Space Velocities
    SHAO Jing, LIU Haiyu, QIAO Xiaolei, JIN Yan, FAN Baoguo
    2020, 40(12): 1014-1018. https://doi.org/10.19805/j.cnki.jcspe.2020.12.010
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    Simultaneous desulfurization and denitrification experiments were performed at different space velocities by microwave-induced low-temperature plasma through activated coke discharge. Results show that as the space velocity decreases, the discharge intensity weakens and the denitrification rate reduces, while the desulfurization rate increases. At low space velocities and under weak discharge conditions, the desulfurization efficiency is higher than the denitrification efficiency; whereas at high space velocities and under strong discharge conditions, the desulfurization efficiency is lower than the denitrification efficiency. Microwave discharge increases the content of C=C functional groups on the surface of activated coke, which are favorable to the desulfurization and denitrification, when sulfur-and nitrogen-containing functional groups are generated.
    • New Energy
  • New Energy
    Concept Design and Dynamic Response of Floating Wind Turbine Platforms Under Normal and Severe Sea Conditions
    LI Shujun, LI Chun, WANG Bo, DING Qinwei
    2020, 40(12): 1019-1027. https://doi.org/10.19805/j.cnki.jcspe.2020.12.011
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    To study the dynamic response of offshore floating wind turbine platforms under the combined disturbance of wind, wave and ocean currents, a model of 2×2 array floating wind farm was established based on the Barge platform, following which, the time-frequency response of the floating wind farm with a single platform or multi platforms was comparatively studied using radiation/diffraction theory and finite element method, under normal and severe sea conditions. Results show that the dynamic response of a multi-platform structure is mainly of the low frequency kind under normal sea condition. The multi-platform structure has a higher stability than the single-platform structure in surge, heave and pitch direction. Under severe sea conditions, the dynamic response of a multi-platform structure is mainly concentrated in the wave frequency region. For the multi-platform structure, the greater the distance away from the windward side, the smaller the surge and pitch angle will be.
    • Material Research
  • Material Research
    Corrosion Behavior of Heat-resistant Steels 12Cr1MoV, T92 and Inconel 625 in Supercritical Carbon Dioxide Environment
    NI Yifan, YANG Changshun, ZHAO Shuangqun
    2020, 40(12): 1028-1034. https://doi.org/10.19805/j.cnki.jcspe.2020.12.012
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    To study the corrosion behavior of the materials for high-temperature components in a new supercritical carbon dioxide (S-CO2) Brayton cycle power generation system, corrosion tests were conducted on the heat-resistant steels 12Cr1MoV, T92 and Inconel 625 that had been exposed in supercritical CO2 environment at 600℃ and 25 MPa for 3 000 hours. Scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffractometer were employed to characterize the corrosion products. Results show that the corrosion kinetics of above three alloys obey a parabolic law, and the corrosion resistance of Inconel 625 is successively superior to T92 and 12Cr1MoV. The corrosion products of 12Cr1MoV and T92 consist of outer layer Fe3O4 and inner layer (Fe,Cr)3O4, in which, between the matrix and inner layer (Fe,Cr)3O4 of T92 corrosion product, there exists a transition layer consisting of the mixture of (Fe,Cr)3O4 and matrix. The corrosion product on the surface of Inconel 625 is mainly the protective oxidation film Cr2O3.