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    Boiler Technology
  • Boiler Technology
    Research on the Sound Ray Bending Characteristics of Temperature-Velocity Coupling Field in Furnace
    JIA Shaoqi, SONG Zhijiang, LI Yanqin, GUAN Xuefeng, LIU Zhigang
    2021, 41(8): 617-623. https://doi.org/10.19805/j.cnkij.cspe.2021.08.001
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    In order to realize the reliable reconstruction of the thermophysical quantity field measured by the acoustic wave method and clarify the coupling mechanism of the medium temperature and flow velocity on the acoustic velocity, the triangle forward expansion method and the Lagrangian method were used to establish the tracking model. For the typical temperature field and flow field of different furnaces, the path bending effect of acoustic wave propagation was studied. Meanwhile a one-dimensional flow field model was established to verify the feasibility and reliability of the above method theoretically. Results show that the coupling temperature and flow field of flue gas has complex effect to the sound ray paths in furnace. The reconstruction results of temperature and flow field by acoustic method will be distorted if the bending of sound line is ignored. The sound ray distribution is consistent with each other in different theoretical methods, which proves that the sound ray tracking model is reliable.
  • Boiler Technology
    Comparative Study on the Arrangement of the Closing-to-wall Air System in Opposed Firing Boiler
    CHEN Qingen, CHEN Guoqing, ZHU Qingguo, XIE Jianbo, ZHANG Xian, SHI Hongfei, FENG Peiliang
    2021, 41(8): 624-631. https://doi.org/10.19805/j.cnkij.cspe.2021.08.002
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    Three main closing-to-wall air arrangement modes (front and rear wall arrangement, side wall arrangement and whole wall combination arrangement) of opposed firing boiler were taken as the research object. With the using of numerical simulation, the changes of air atmosphere at the side wall areas, NOx emission concentration and un-burned carbon mass fraction under three different arrangement modes were analyzed. Results show that although these three arrangement modes can increase the O2 volume fraction in the near wall area, reduce the H2S and CO volume fraction and the content of unburned carbon, there exists great differences in the coverage areas. With the same volumes of closing-to-wall air, the coverage areas with oxygen content greater than 2.0% in the near wall area can account for 83.84% of the side wall of the boiler for the whole wall combination arrangement mode, which is higher than the other two arrangement modes (61.38% and 68.80%). With the application of the whole wall combination closing-to-wall air system, the average O2 concentration increases from 0.25% to more than 2.5%, the average concentration of H2S is reduced by 70%, the average volume fraction of CO is reduced by 65%. No significant change is observed for the boiler thermal efficiency, cooling water amount of superheater and reheater, NOx concentration at SCR inlet and carbon content of fly ash.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Numerical Simulation of Dual Fuel Mixed Combustion in Gas Turbine Combustor
    YANG Qiang, LI Yajun, CONG Wenfeng, LIN Feng
    2021, 41(8): 632-639. https://doi.org/10.19805/j.cnkij.cspe.2021.08.003
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    A numerical simulation of gas turbine dual fuel combustion chamber under two kinds of fuel mixed combustion state was carried out. Results show that the atomization characteristics of liquid fuel under different flow rates, the gas/liquid path structure of dual fuel nozzle and the combustion field difference of gas/liquid fuel determine the mixed combustion performance of dual fuel combustion chamber. When the two fuels are mixed combustion, the deterioration of liquid fuel atomization quality and the radial compression of the combustion field by the outer ring gas fuel nozzle lead to the movement of the high temperature stagnation point to the outlet of the combustion chamber. While the overall temperature distribution factor(OTDF) is high, and the combustion efficiency is decreased. The combustion performance of dual-fuel combustion chamber in low-condition mixed combustion can be effectively improved by further optimizing the aerodynamic fuel atomizing nozzle or increasing the atomized air volume.
  • Steam Turbine and Gas Turbine
    Blade Root Groove Structure Optimum Design of Supercritical Carbon Dioxide Turbine
    LI Zhenya, ZHAO Feng, ZHU Youjun, FAN Xuefei
    2021, 41(8): 640-644. https://doi.org/10.19805/j.cnkij.cspe.2021.08.004
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    For the 10 MW supercritical carbon dioxide turbine unit, the T-shaped blade root wheel groove profile was optimized, and the angle of the optimized blade root wheel groove contact surface was obtained by theoretical analysis, then the stress distribution of the T-shaped blade root groove before and after optimization was compared by finite element method.Meanwhile, the influence factors of blade pre-torsion mechanism and rotor deformation were analyzed, and a method to optimize the T-shaped blade root rhombic intermediate structure was proposed. Results show that the peak stress of the optimized wheel slot is slightly higher than before, which of the blade root is significantly reduced,while the stress concentration of the leaf root is improved.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Experimental Research for Correlation Between Radiation Characteristic and Surface Temperature of Fly Ash
    ZHU Runru, WANG Xin, YUAN Ye, ZHANG Yiyang, LI Gengda, HUANG Yun
    2021, 41(8): 645-649. https://doi.org/10.19805/j.cnkij.cspe.2021.08.005
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    In order to reduce the risk of the tube failure in coal/biomass/MSW fired power plants, a high temperature heat exchanger surface ash and temperature state monitoring system based on endoscopic optical temperature measurement method was proposed. A multi-diffusion Hencken burner and fine-particle oscillating powder feeding technology were used to study the relationship between the visible light radiation characteristics and temperature of three kinds of fly ash.Results show that the radiation-temperature correlation curves of the three kinds of fly ash are distinguished due to the different physical and chemical properties.Different selection of optical channels will also significantly affect the accuracy of the results,so laboratory calibration of the system should be carried out before practical application to obtain more accurate results.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Numerical Simulation of Convective Heat Transfer Enhanced by Acoustic Streaming Around Heat Exchanger Tubes
    YANG Yanfeng, JIANG Genshan, YU Miao
    2021, 41(8): 650-658. https://doi.org/10.19805/j.cnkij.cspe.2021.08.006
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    In order to study the effect of steady-state acoustic streaming components on the convective heat transfer characteristics of heat exchange tubes, a numerical calculation model for the enhancement of heat transfer by acoustic streaming outside a single heat exchange tube in a traveling wave field was established. The coupling effect of acoustic streaming and non-uniform temperature field is calculated by using the numerical method of separating time scale, and the variation rules of local Nusselt number and average Nusselt number of heat exchanger tube under different excitation frequencies (10-1 500 Hz) and sound pressure levels (103-127 dB) were analyzed. Results show that the average Nusselt number decreases exponentially with the increase of excitation frequency, and increases exponentially with the increase of sound pressure level. The inner streaming formed by low-frequency sound waves and the outer streaming formed by high-frequency sound waves determine different local Nusselt number distribution laws. Low-frequency and high-intensity sound waves can form a strong acoustic streaming disturbance inside and outside the thermal viscous boundary layer of the heat exchanger tube, which greatly strengthens the heat transfer process of the heat exchanger tube.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Numerical Study on Evaporation and Movement Characteristics of Desulfurization Wastewater in Flue Gas Channel
    LI Hengfan, JIAO Shiquan, HAN Zhonghe
    2021, 41(8): 659-666. https://doi.org/10.19805/j.cnkij.cspe.2021.08.007
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    An evaporation and diffusion models of the atomized particles in the flue gas were established to reveal the evaporation and movement characteristics of the desulfurization wastewater in the boiler tail flue gas channel. The variation rules of average droplet diameter, evaporation distance and other parameters were obtained in the evaporation process, and the effects of the flue gas and droplet properties on the evaporation process were compared through numerical simulation. Results show that the droplet complete evaporation time decreases with the increases of the temperature and velocity of flue gas, the initial velocity, initial temperature and spray angel of droplets, and the decreases of the mass fraction of water vapor, initial droplet diameter and water spray rates. The complete evaporation distance of droplets decreases first and then increases with increasing the flue gas velocity. When the flue gas velocity is equal to 10 m/s, the complete evaporation distance reaches its minimum. The evaporation distance may be mainly affected by other factors through the droplet evaporation time, which is positively related to the droplet evaporation distance.
    • New Energy
  • New Energy
    Experimental Analysis and Prediction of Biomass Gasification in Three-bed Series Chemical Chain
    CHEN Hongwei, LIU Bochao, JIA Jiandong, LIU Yuqiang, LIANG Jinjun, CHEN Zhe, FENG Xupeng, ZHU Lou
    2021, 41(8): 667-673. https://doi.org/10.19805/j.cnkij.cspe.2021.08.008
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    Based on a three-bed series chemical chain(TBS-CLC) biomass gasification experiment system, the effect of the control parameters on circulating flow rate was analyzed, such as air reactor wind velocity, fuel reactor wind velocity, circulating material mass and gasification chamber bed material level. 129 test data were used to predict the circulating flow rate using the back propagation neural network model, Genetic algorithm optimized back propagation(GA-BP) neural network model and the support vector machine model. Results show that circulating flow rate increases with the increase of fuel reactor wind velocity, but the increase becomes gradually gentler. Circulating flow rate increases with the increase of air reactor wind velocity and circulating material mass and with the decrease of bed material level. The root mean square error predicted by the test sample is 0.841 10 kg/(m2·s), and the average absolute percentage error is 4.42%. The predicted value of the model are in good agreement with the test value, and the particle circulating flow rate can be well predicted by GA-BP model.
  • New Energy
    Mechanical Performance Analysis of Large Wind Turbine Bend-Twist Coupling Blade Based on Aeroelastic Tailoring
    ZHANG Li, MIAO Weipao, LI Chun, ZHANG Wanfu, YAN Yangtian, WANG Bo
    2021, 41(8): 674-683. https://doi.org/10.19805/j.cnkij.cspe.2021.08.009
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    In order to analyze the mechanical properties of bend-twist coupling blades, the NREL 5 MW wind turbine blade shell model was established based on the secondary development of the three-dimensional modeling software NX. The composite material layup design was further carried out on the blades and aeroelastic tailoring of blades was achieved by offsetting the spar cap fiber in the mirror image. The CFD method was used to calculate the pressure distribution on the blade surface. To study the effect of the spar cap fiber offset angle on the mechanical properties of the bend-twist coupling blades, the modal, static and buckling analyses were performed in conjunction with the finite element method. Results show that when the offset angle of the spar cap is small, the maximum stress value on the surface of the bend-twist coupling blade is smaller than that of the traditional blade. The effect is best when the offset angle is -15ånd the maximum stress value decreases by 14.78%. Compared with the conventional blades, the natural frequencies and buckling factors of each order of the bend-twist coupling blades all decrease,and their decrease are close when the angle of forward and reverse offset are the same.The off-axis mirror laying of the spar cap has a great influence on the flapwise vibration of the blade. The offset angle of the spar cap has a certain influence on the anti-buckling ability of the blade and the maximum buckling load of the blade is reduced by about 78%. The natural frequency and buckling factor of the bend-twist coupling blades should be paid more attention to avoid the resonance between the natural frequency of the blade and the excitation frequency. If necessary, the laminate structure should be optimized to improve the anti-buckling ability of the bend-twist coupling blades.
    • System Engineering
  • System Engineering
    Thermo Dynamic Performance and Economic Analysis of a New Type of Solar Jet Co-supply System for Combined Heating or Cooling and Power
    LUO Chi, SUN Peijie, ZHANG Kai, Lü Xiaojing, WENG Yiwu
    2021, 41(8): 684-691. https://doi.org/10.19805/j.cnkij.cspe.2021.08.010
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    A new type of solar jet co-supply system for heating or cooling and power was proposed on basis of organic Rankine cycle and jet refrigeration cycle, via utilization of concentrating solar power, combined heating or cooling and power could be realized through simple valve switching.According to the typical solar radiation intensity in winter and summer in Northwest China, the capacity of power generation, heating or cooling supply were calculated, then the capacity of co-supply of heating or cooling and power for the system was studied while economic analysis was conducted systematically. Results show that under the condition of solar radiation intensity in Northwest China,the system can independently meet the requirements of daily power and heating or cooling of a building. The maximum capacity of power generation and cooling supply is 5.42 kW and 7.26 kW in summer while the maximum heating supply is 2.96 kW in winter. The whole cost of power generation for the system is 0.755 yuan/(kW·h). Compared with other power generation systems, the system has a better performance of low cost, environmental protection, reliability and function of co-supply of heating or cooling and power.
  • System Engineering
    Performance Analysis of a Heat-power Decoupling System Integrated with Steam Ejectors in the Full Condition Rang
    ZHANG Juntai, LIU Ming, CHONG Daotong, YAN Junjie
    2021, 41(8): 692-699. https://doi.org/10.19805/j.cnkij.cspe.2021.08.011
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    In order to realize the heat-power decoupling of cogeneration units, a heat-power decoupling system integrated with steam ejectors was proposed, and the calculation model of the system within the full condition rang was established. Taking a 350 MW cogeneration unit as an example, the heat-power decoupling system integrated with steam ejectors as the ejector heating unit, so as to compare the operation flexibility and coal saving rate of the two units. Results show that when the heating load is 700 GJ/h, the minimum electric load rate of cogeneration unit and ejector heating unit is 50% and 34%, respectively. Furthermore, electric load regulation range of the ejector heating unit is larger. Compared with cogeneration unit, the ejector heating unit is more economical under certain conditions. Moreover, the ejector heating unit is more energy-saving under the condition of high ejection rate, low electric load rate and low heat load rate. To ensure that economy of the ejector heating unit is better than that of the cogeneration unit, it requires that the electric load rate is less than 85% at the heating load of 200 GJ/h, or the heat load rate is lower than 0.91 at the electric load rate of 80%.
    • Material Research
  • Material Research
    Microstructure Evolution Analysis of FB2 Steel Used for High-efficiency Ultra Supercritical Unit During 620℃ High Temperature Creep-Rupture Tests
    TIAN Xiao, XU Hui, QIN Chengpeng, LI Taijiang, LI Yimin
    2021, 41(8): 700-706. https://doi.org/10.19805/j.cnkij.cspe.2021.08.012
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    In order to study the microstructure change of FB2 steel during long-term service, high temperature creep-rupture tests were carried out at 620℃, and microstructure of the creep-rupture sample was observed, so as to analyze evolution law of its microstructure and precipitates. Results show that the microstructure of FB2 steel is still tempered martensite during high temperature creep-rupture tests. With the rise of creep-rupture time, the martensite structure recovers with its lath becomes wider, and dislocation density decreases slightly. The size of M23C6 carbide is not obviously coarsened, its average size is still about 250 nm after creep-rupture time reaches 9 577 h, which shows good pinning effect on martensite lath boundary. During high temperature creep-rupture tests, new Laves phase precipitates in FB2 steel by single nucleation and attaching M23C6 to nucleation, which grows rapidly and would engulfs M23C6 carbide particles. After 9 577 h, the maximum size of Laves phase reaches 1 μm, while the thermodynamic equilibrium state is not yet reached.
  • Material Research
    Creep Behavior Analysis and Life Prediction of T91/TP347H Dissimilar Steel Welded Joint
    CAO Yu, LIU Chuanhuai, PAN Weiguo, JI Dongmei
    2021, 41(8): 707-712. https://doi.org/10.19805/j.cnkij.cspe.2021.08.013
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    High temperature creep tests of T91/TP347H dissimilar steel welded joints were carried out under constant temperature and different stresses. The modified θ projection model was used to describe the creep behavior of T91/TP347H dissimilar steel welded joints. Combined with the empirical formula of creep fracture, the analytical expression of minimum creep rate was derived, furthermore, a new creep life prediction model was proposed. Results show that the fitting curve obtained by modified θ projection model is in good agreement with experimental results, which could accurately express the three-stage characteristics of creep curve. Prediction error of the proposed creep life prediction model is within 5%, which shows good prediction accuracy.