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    Boiler Technology
  • Boiler Technology
    Analysis of Heating-surface Slagging and Outfire Mechanism Caused by Slag-dropping in Coal-fired Boilers
    WANG Shuai, WU Xin, LU Kun, WANG Kai, LI Xuefei
    2020, 40(11): 865-871. https://doi.org/10.19805/j.cnki.jcspe.2020.11.001
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    A study was conducted on the heating-surface slagging and outfire mechanism caused by slag-dropping in four coal-fired units of 1 000 MW, 660 MW, 330 MW and 220 MW, respectively, through analysis of the falling slag macroscopic morphology, furnace pressure fluctuation, slagging of design coal, vitrinite reflectance of accident coal, furnace design parameters and boiler operation mode. Results show that the common feature of outfire failures during slag-dropping before main fuel trip (MFT) is that the furnace pressure jumps first, which is mainly due to the combustible gas explosion in the lower part of the furnace, and secondly due to the entry of a large amount of water vapor into the furnace. For bituminous coal-fired boilers, it is easy to form coloured glaze like blue-black slags when the ratio of mixed anthracite is large, and it is easy to form pale yellow porous slags when the ratio of mixed bituminous coal with low ash melting point is large; a certain number of black coke particles would appear in the slags when the ratio of lean coal to bituminous coal is large.
  • Boiler Technology
    Experimental Study on Combustion Adjustment of a Tangentially-fired Boiler Against High-temperature Corrosion
    ZHOU Wentai, WANG Ke, HE Xiang, MA Dafu
    2020, 40(11): 872-877. https://doi.org/10.19805/j.cnki.jcspe.2020.11.002
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    To reduce the closing-to-wall H2S concentration to achieve the purpose of alleviating the high-temperature corrosion over the water wall, the closing-to-wall gas composition was measured for a 300 MW tangentially-fired boiler, while an analysis was conducted on the causes. Results show that the high-temperature corrosion is mainly concentrated on the water wall in the burner area below the overfire air, asymmetrically distributed along the center line of the water wall, with relatively high H2S concentration on the right of the center line, resulted from unreasonable air distribution, due to insufficient rigidity of the secondary air, which can not wrap up the primary air completely, leading to flame spreading to the water wall. The closing-to-wall H2S concentration has been significantly reduced, while the high-temperature corrosion has been effectively controlled, after taking the following measures, such as adjusting the total air volume and the surrounding air flow rate, and intensifying the combustion in primary air environment, etc.
  • Boiler Technology
    Numerical Simulation on Sulfur Evolution in Pulverized Coal Combustion Under Multi-hole Wall Air Coupling with Air Staged Technology
    MA Honghe, ZHANG Wei, LI Jun, ZHOU Lu, CUI Zhigang, ZHAO Jun
    2020, 40(11): 878-883. https://doi.org/10.19805/j.cnki.jcspe.2020.11.003
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    To investigate the impact of multi-hole wall air on high-temperature corrosion and to test the model reliability for gas phase reaction mechanism of sulfur components, numerical simulations were carried out on the sulfur evolution in pulverized coal combustion under multi-hole wall air coupling with air staged technology using Ansys Fluent software. Results show that all the errors between predicted and measured values for SO2, H2S, CS2 and COS are within 18%, indicating that the kinetic model can be adopted for the predication of sulfur component evolution in actual engineering; proper amount of multi-hole wall air can form a film of oxidizing gas over the wall in the main combustion and reductive zones, keeping the corrosion components away from the wall. By comprehensively considering the NOx emission, combustion efficiency and high-temperature corrosion of the boiler, the optimal value of the multi-hole wall air ratio is recommended to be 0.05, when the burner air ratio is 0.80.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Quantitative Analysis of the Effects of Cylinder Efficiency on the Unit Heat Consumption of a 1 000 MW Ultra Supercritical Double-reheat Steam Turbine
    ZHANG Jiajia
    2020, 40(11): 884-888. https://doi.org/10.19805/j.cnki.jcspe.2020.11.004
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    To obtain the influence law of cylinder efficiency on the unit heat consumption of a 1 000 MW ultra supercritical double-reheat steam turbine, a linear analysis was carried out to perform relevant calculations. Results show that the efficiency of super high- and high-pressure cylinder has little effect on the heat consumption of a unit, while that of medium- and low-pressure cylinder has a great influence. With the decrease of unit load, the influence of efficiency of each cylinder increases, but the amplitude of variation is relatively small. The effect of cylinder efficiency on the heat consumption of a unit is mainly realized through the changes of unit power and system heat absorption, in which, power changes play an important role, especially the efficiency of medium- and low-pressure cylinders.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Condition Monitoring of Wind Turbine Gearbox Bearings Based on Deep Learning and SPRT
    LIU Xubin, GUO Peng, LIN Feng
    2020, 40(11): 889-896. https://doi.org/10.19805/j.cnki.jcspe.2020.11.005
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    To improve the efficiency and accuracy of condition monitoring for high-speed shaft bearings with high failure rates, a condition monitoring method was proposed based on deep learning model. First, the ReliefF method was used to select the model variables, of which, the dimension was reduced through a denoising autoencoder. Then, a model was established for the nonlinear relationship between the temperature of high-speed shaft bearing and its influencing factors simplified by dimension reduction using long short-term memory network. Subsequently, the method of sequential probability ratio test was introduced to capture the abnormal changes of the bearing temperature residual predicted by the model, and to send out abnormal alarms of wind turbine operation in time. The model was finally verified by two 1.5 MW experimental wind turbines in east China. Results show that the method proposed can help to timely and accurately find the overtemperature problem of high-speed shaft bearing caused by gearbox abnormality, which may serve as a reference for condition monitoring and fault warning of wind turbine gearbox bearings.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Simulation on Combustion Characteristics of Non-premixed Syngas Jets Based on Different Coupled Models
    HUANG Zhangjun, LUO Yanzhen, LI Luping, TIAN Hong
    2020, 40(11): 897-905. https://doi.org/10.19805/j.cnki.jcspe.2020.11.006
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    Based on different kinds of chemical reaction mechanisms, turbulence models and combustion models, eight groups of coupled models were adopted to simulate the non-premixed jet flame of CO/H2/N2 fuel, so as to analyze the accuracy of each coupled model by comparing the results of simulation and experiment. Results show that the coupled model 4 (PdM model+RNG k-ε model+SLF model) and the model 8 (GRI-Mech 3.0 model+Standard k-ε model+EDC model) bring out more accurate prediction on temperature and component of the non-premixed syngas jet flame. The model based on SLF has higher prediction accuracy on radial distribution of temperature and main components than that based on EDC. Optimum simulation results could be obtained for the non-premixed syngas jet flame using the coupled model 4 (PdM+RNG k-ε+SLF).
  • Engineering Thermophysics
    Effects of Pressure on Flame Flickering Under Different Co-flow Velocities
    DENG Ruiying, LI Yongchao, YANG Mo, LI Yubing
    2020, 40(11): 906-914. https://doi.org/10.19805/j.cnki.jcspe.2020.11.007
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    The combustion process of methane/air in a coaxial jet combustor was simulated by direct numerical simulation (DNS) using Ansys Fluent, so as to investigate the influence of pressure on the flame flickering under different co-flow velocities, and to study the combustion system by nonlinear analysis. Results show that the flame flickers at the co-flow velocity of 0.009 8 m/s, and the pressure of 0.7×105-1.6×105 Pa; the interaction between flame and vortex increases with the rise of pressure, during which, the flame flickering gets intensified. When the co-flow velocity increases to a critical value, the flame that originally flickers in the pressure flow field becomes stable, indicating that the combustion flow field changes from the buoyancy dominated type to the co-flow momentum dominated kind. Increasing the co-flow velocity and pressure can promote the formation of soot. Through nonlinear analysis on the dynamic characteristics of the combustion system, the combustion system is found to be strongly dependent on the initial values of the co-flow velocity and pressure. At the critical values of the co-flow velocity or pressure, the solution of the system bifurcates dynamically.
    • New Energy
  • New Energy
    Seismic Dynamic Response of Jacket Offshore Wind Turbines Under Different Wind Loads
    YAN Yangtian, YUE Minnan, LI Chun, YANG Yang, XU Zifei
    2020, 40(11): 915-923. https://doi.org/10.19805/j.cnki.jcspe.2020.11.008
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    To study the influence of wind load on the dynamic response of jacket offshore wind turbines during the occurrence of an earthquake, the NREL 5 MW offshore wind turbine was taken as the research object, and the finite element model of truss wind turbine was established. The p-y curve was used to describe the interaction between flexible seabed soil and pile foundation, while the SMOOTH turbulent wind spectrum model was applied to solve the wind load, and the transient dynamic response of the wind turbine supporting structure was calculated under normal operation, shutdown and emergency shutdown conditions. Results show that the wind load has a significant influence on the supporting structure of a wind turbine, and the response characteristics of the supporting structure vary greatly under different operating conditions. The occurrence of an earthquake will lead to a surge in the frequency and amplitude of local shear stress and strain energy. The emergency shutdown can effectively weaken the influence of wind-earthquake interaction on the wind turbine blades and the supporting structure. 60 s after the earthquake, the peak value of local shear stress in the supporting structure would drop by 7.7%, with an average reduction by 87.5%. The peak value of strain energy at the junction of wind turbine tower and jacket structure would drop by 14.6%.
  • New Energy
    Optimization of Cleaning Strategies for Heliostat Fields in Tower Solar Thermal Power Plants
    JIANG Zhihao, DU Yuhang, LIU Xiangmin
    2020, 40(11): 924-928. https://doi.org/10.19805/j.cnki.jcspe.2020.11.009
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    Based on a 50 MW tower solar thermal power plant, a simulation model was constructed to analyze the influence of heliostat reflectivity on the annual average power generation and the levelized cost of energy. Taking the sum of the annual loss of power generation and the cost of heliostat cleaning caused by the reduction of heliostat reflectivity as the total annual loss of power station, an optimization model was established for the heliostat cleaning strategy to obtain the variation law of the total annual loss of power station with the cleaning period, and finally to determine the optimum cleaning strategy. Results show that with the increase of reflectivity, the annual average power generation increases, while the levelized cost of energy decreases. The elongation of cleaning period will result in a decrease first and then an increase in the total annual loss of the power plant.
    • Material Research
  • Material Research
    Strength Checking and Evaluation of P92 Hot-extruded Tee Based on 3D Optical Scanning Technology
    SHI Zhigang, LI Nanlin, MA Hong, JIA Jianmin, ZHANG Hongjun, XIONG Wei
    2020, 40(11): 929-935. https://doi.org/10.19805/j.cnki.jcspe.2020.11.010
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    Taking the P92 hot-extruded tee with cracks after service for 85 000 hours as an object of study, the size of the tee was mapped by 3D optical scanning technology, and subsequently the strength checking and stress finite element analysis were carried out, following which, the stress intensity assessment was performed. Results show that the size of the P92 hot-extruded tee obtained by three-dimensional optical mapping is in good agreement with the actual data. The maximum stress is located at the corner center on inner wall of the shoulder, which coincides with the initiation position after service for 85 000 hours. The weak structural strength at the shoulder is the main factor causing the cracking of the P92 hot-extruded tee.
  • Material Research
    Creep Rupture Life Estimation of P91 Steel Pipes Through Artificial Neural Network Based Hardness Prediction
    WANG Zheng, WANG Yanfeng
    2020, 40(11): 936-939. https://doi.org/10.19805/j.cnki.jcspe.2020.11.011
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    The creep rupture life of P91 steel pipes with different hardness was evaluated using artificial neural network (ANN) technology, while an assessment model was established for the creep rupture life, which was verified with the test data obtained under different hardness conditions. Results show that the predictive data of the creep rupture life assessment model based on artificial neural network are in good agreement with the experimental data, and most of the output errors can be controlled within ±5%. Based on this model, the creep rupture life of P91 steel pipes could be evaluated quickly and nondestructively under any hardness conditions. The model helps to not only save the test cost, but also improve the reliability of the creep rupture life prediction through self-learning of artificial neural network.
    • Nuclear Technology
  • Nuclear Technology
    Research on Transient Wave Entry Characteristics of the Primary Loop Pressurizer in an AP1000 Nuclear Power Unit
    LIU Jianquan, YANG Yihao, ZHANG Jiguo, YAO Wenzhuo, ZHOU Tao, DAI Wentai
    2020, 40(11): 940-948. https://doi.org/10.19805/j.cnki.jcspe.2020.11.012
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    To study the evolution process and hydraulic characteristics of the wave entry flow in an AP1000 pressurizer, a three-dimensional CFD method was used to analyze the unsteady heat transfer to capture the intensity of temperature and velocity fluctuation for the mixture of cold and hot fluids in the wave entry process, while the effect of buoyancy was estimated by taking the fluid density as a polynomial function of temperature. Results show that the simulated values agree well with the experimental data, and the RSM turbulence model combined with VOF multiphase heat transfer model can effectively predict the development trend of wave entry process. The Richardson number Ri has an important influence on the mixing of hot and cold fluids, and its magnitude determines the influence of buoyancy on fluids. The mixing of hot and cold fluids mainly occurs in the -0.5 m < z < 0.5 m area of the lower head; the most intense fluctuations of temperature and velocity are concentrated in the area of -0.3 m < z < 0.3 m, and the peak value of fluctuation increases gradually with the advance of wave entry process, so the electric heater should avoid to be placed in such rugged environment.