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    Research & Analysis
  • Research & Analysis
    Analysis and Optimization on the Thermal Performance of a 500kW Supercritical Carbon Dioxide Recompression Cycle
    Zuo Chengyi, Li Xu, Gan Lu
    2023, 37(1): 1-6. https://doi.org/10.19806/j.cnki.fdsb.2023.01.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To research and analyze the performance and rule of the supercritical carbon dioxide recompression cycle generation system, a calculation model was established for the 500 kW supercritical carbon dioxide recompression cycle, while the effects of cycle parameters on the thermal efficiency and the split ratio were studied. After which, the cycle parameters were optimized so as to obtain the optimum thermal efficiency. Calculation results show that following cycle parameters all have the optimum values for the optimum thermal efficiency, including the minimum temperature, the minimum pressure, the maximum pressure, and the split ratio. The thermal efficiency increases with the increase of the maximum temperature. Based on the optimized cycle parameters, the mass flow of working fluid is reduced by 0.92 kg/s, and the thermal efficiency is increased from 39.51% to 43.85%.
  • Research & Analysis
    Study on Flow Field of the Induced Fan with Inlet and Outlet Flue Gas Duct in a 600MW Unit
    Li Yanwei, Hu Shanmiao, Ma Dafu
    2023, 37(1): 7-12. https://doi.org/10.19806/j.cnki.fdsb.2023.01.002
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on numerical simulations, comparisons and analyses were carried out for the induced fan proper and the whole flue gas duct system in a 600 MW unit. Results show that the inlet and outlet flue gas duct has a certain effect on the induced fan performance under small flow condition, and there is an interaction effect between the inner flow field of the induced fan and the flow field of the inlet and outlet flue gas duct. With the whole flue gas duct system under boiler maximum continuous rating (BMCR) condition, the uniformity of the flow field of the inlet flue gas duct can be improved by the characteristics of the inner flow field of the induced fan under design condition, which may result in the aggravated energy loss and the more disordered flow field. The effects of the inner flow field of the induced fan should be fully considered while optimizing and retrofitting the inlet and outlet flue gas duct.
  • Research & Analysis
    Numerical and Experimental Study on the Influence of Filter on Aerodynamic Performance of High-pressure Control Valve in Steam Turbine
    Zhong Zhuhai, Sun Qi, Tian Chaoyang, Yang Changzhu
    2023, 37(1): 13-17. https://doi.org/10.19806/j.cnki.fdsb.2023.01.003
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the steam turbine in a subcritical unit, a study was conducted on the experital test and numerical simulation for the aerodynamic performance of the high-pressure control valve with the annular filter. Results show that by adopting the filter, the the symmetry of the flow field distribution in the valve is significantly improved, and the force on the valve disc in the flow direction and the direction perpendicular to the flow is reduced. Which results in the weakened backflow intensity of the oblique flow field in the valve seat downstream and the significant improved uniformity of the outlet flow field of the valve seat. The filter can not only rectify the flow, but also effectively control the flow around the valve chamber. The filter with a reasonable design has little effect on the flow coefficient and the total pressure loss coefficient of the valve, and can significantly improve the stability of the flow field. Through the comparison between numerical calculation results and experimental test results, it is proved that the simulation precision based on the porous media model can satisfy the engineering application requirements.
  • Research & Analysis
    Analysis of the Inner Wall Crack on Drain Tank for High-temperature and High-pressure Steam Pipeline
    Xie Ameng, Hu Zhifang, Cheng Lei, Xu Zhiguo
    2023, 37(1): 18-23. https://doi.org/10.19806/j.cnki.fdsb.2023.01.004
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking a drain tank for the high-temperature and high-pressure steam pipeline in a power plant as the research object, analyses were conducted on the reasons of the inner wall crack on the drain tank through the simulation with the basic flow and heat transfer model, and the observation of the metallographic structure. Results show that the thermal stress is mainly affected by the temperature field. The different temperature gradients inside the drain tank lead to the generation of tiny cracks, which gradually expand with the increase of the operation time, and finally cause the drain tank to be unable to operation normally. The weakening of secondary hardening effect and the continuous decline of material hardness are casued by the aggregation and coarsening of M23C6 type carbide and Laves phase, and the migration and diffusion of solid solution elements in the matrix structure, which are the main reasons for the performance deterioration of P92 steel drain tank after long-term operation.
  • Research & Analysis
    Analysis on Linear Deviation of the Outlet Pipeline of High Temperature Reheater in an Ultra-supercritical Unit
    Zhang Zhenglei, Wu Haiyang, Huang Xiaobo, Zhang Xusheng, Sun Zhongyuan
    2023, 37(1): 24-30. https://doi.org/10.19806/j.cnki.fdsb.2023.01.005
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The linear deviation occurred in the outlet pipeline of the high temperature reheater in a 660 MW ultra-supercritical unit, and many constant spring supports were at the lowest position. Analyses were conducted on the liner deviation, and combined with the displacement-load test, the stress distribution of the pipeline during operation was researched through simulation. Results show that the load deviation and constant degree of most of constant spring supports has significantly risen above the standard value, and the displacement in cold operation is in accordance with the tested deviation value on site. Both of the primary stress and the secondary stress during operation obtained from simulation have an increase on average, while the secondary stress of some nodes even exceeds the allowable value. The main reason of the pipeline linear deviation is the substandard performance of the constant spring support, which is caused by a mismatch between the gravity load of the pipeline and the applied load of the constant spring support. It is suggested that the unqualified support must be replaced, and the daily maintenance of support should be strengthened in the management and supervision.
    • Material Technology
  • Material Technology
    Oxidation Analysis of T22 Heat Exchange Tube at 550℃
    Wang Miaomiao, Yang Changshun, Zhu Xinghua, Wu Zhijun, Jiang Yichen, Tang Yunfei
    2023, 37(1): 31-35. https://doi.org/10.19806/j.cnki.fdsb.2023.01.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The oxidation analysis was carried out for the samples of the T22 heat exchange tube for nuclear power units with different oxidation time periods at 550 ℃, and analyses were conducted on the thickness, morphology and composition of oxide films. Experimental results show that, the growth of oxide films of the T22 heat exchange tube is similar to the parabolic law under the longest test time of 41 255 h, while the oxidation rate of the inner and outer walls of the sample decreases gradually with the increase of the test time. In the later stage of the oxidation test, the oxidation rate curves of the inner and outer walls are close to each other and tend to be stable. The oxide film consists of two layers: the outer layer is mainly composed of Fe3O4, and the inner layer is mainly composed of the mixed oxide of Fe2O3 and (Fe, Cr)3O4.
  • Material Technology
    Fracture Analysis on Fastening Bolt of Electro-Hydraulic Servo Valve for High Pressure Regulating in a Steam Turbine of Feed Water Pump
    Liu Ming, Wang Zhengjun, Wu Gang, Xie Xin
    2023, 37(1): 36-40. https://doi.org/10.19806/j.cnki.fdsb.2023.01.007
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of the fracture failure of the fastening bolt of the electro-hydraulic servo valve for high pressure regulating in a steam turbine of feed water pump in a thermal power plant, analyses were carried out through following methods, such as chemical component analysis, hardness testing, microstructure analysis, fracture scanning analysis, force simulation calculation, etc. Results show that, the multi-source fatigue fracture of the first bolt is caused by the excessive pretightening force, while the instantaneous ductile fracture of the other bolts occurs directly due to the excessive static load, which is resulted from the manufactured defects existing on the thread surface, especially at the bottom of the screw teeth. This may serve as a reference for the installation and inspection of fastening bolts in electro-hydraulic servo valves.
    • Design & Manufacture
  • Design & Manufacture
    Design and Optimization of the Heat Dissipation Structure of Module Based on Thermal Simulation
    Xie Pan, He Xiang, Li Wenjie, Wang Xuan, Wang Yiding
    2023, 37(1): 41-46. https://doi.org/10.19806/j.cnki.fdsb.2023.01.008
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking a power amplifier module as the research object, one conventional structure and three optimized structures for heat dissipation were designed. Under the condition of the same fan, the same initial, and the same boundary condition, numerical simulations were respectively conducted on the heat dissipation of the four structures based on thermal simulation technology. Simulation results show that, the heat resistance inside the module and the heat flux density at the bottom of the module both can be decreased by the optimization of the module structure, while the convective heat transfer coefficient of the radiator can be improved by the optimization of the radiator structure. Both of the above two optimization measures can reduce the heat source temperature, and the optimal effect of the heat dissipation can be obtained with the combined two measures.
  • Design & Manufacture
    Technology of the Assembly and Welding Between Canned-motor Pump Shell and Steam Generator Outlet Nozzle
    Long Huisong
    2023, 37(1): 47-50. https://doi.org/10.19806/j.cnki.fdsb.2023.01.009
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the assembly and welding between the canned motor reactor coolant pump (canned-motor pump) shell and the steam generator in AP1000 nuclear power units, following aspects of the domestic assembly and welding technology were introduced in detail, such as the surfacing of isolation layer, the assembly and welding of pump shell, the nondestructive testing, the deformation control, etc. Results show that, through adopting the introduced technology, corresponding parameters of the equipment with domestic assembly and welding technology can satisfy the design requirements. Meanwhile, this may serve as a reference for the manufacture of similar equipments in nuclear power units.
    • Automatic Control
  • Automatic Control
    Main Steam Temperature Control System Based on Prediction and Compensation with LSTM in a Thermal Power Unit
    Zhang Guobin, Guo Ruijun, Du Ronghua, Xin Xiaogang, Zhang Qian, Niu Yuguang
    2023, 37(1): 51-58. https://doi.org/10.19806/j.cnki.fdsb.2023.01.010
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The main steam temperature control system was proposed based on the prediction and compensation with long short-term memory (LSTM) in a thermal power unit, and the nonlinear relationship was established between the main steam temperature and following factors from the operation history database of the unit, such as the feed coal flow rate, the main steam pressure, the feed water flow rate, etc. The prediction model with LSTM was built for the main steam temperature control system, after which the main steam temperature control system based on prediction and compensation was constructed through the prediction value. Results show that, compared with the back propagation (BP) algorithm, the LSTM algorithm has a higher prediction accuracy, while in the actual application, the control quality of the steam temperature can be improved, which is caused by the advanced action of the control system based on the predictive compensator with the prediction value.
  • Automatic Control
    High-quality Sample Selection Method for Mass Operating Data of Thermal Process and Corresponding Application
    He Kang, Wang Yong, Chen Rongze, Ren Shaojun, Si Fengqi
    2023, 37(1): 59-64. https://doi.org/10.19806/j.cnki.fdsb.2023.01.011
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A method of high-quality sample selection was proposed for mass operating data of thermal processes. The latent variables of the system were selected through principal component analysis (PCA), and the samples were supplied by the steady weights synthetic minority over sampling technique (SWSMOTE) for the operating condition with fewer samples. After which, taking a gas turbine as an engineering example, the availability of the proposed method was verified. Results show that, the original data can be compressed to about 10% by the proposed method for high-quality sample selection, and the average root mean square error of the model can be reduced from 0.042 to 0.031. The training time of the model can be reduced by 90%.
    • Operation & Retrofit
  • Operation & Retrofit
    Reason Analysis and Treatment Suggestions on Water Wall Cracking at the Corner of Manhole Door of Supercritical Boiler
    Huang Weigang, Chen Peng, Xing Jun, Sun Lijun, Wang Miao, Li Hengda, Ma Hao, Sha Yuanchao
    2023, 37(1): 65-70. https://doi.org/10.19806/j.cnki.fdsb.2023.01.012
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    After a 660 MW supercritical unit was operated for 21 000 h,cracks and leakage occurred on the water wall at the corner of the boiler manhole door, which affected the safe operation of the unit. The failure reason of the water wall at the corner of the boiler manhole door is analysed, the thermal stress of the manhole door and its nearby water wall is simulated, and the shell structure of the manhole door is optimized to reduce the stress of the nearby water wall, so as to ensure the safe operation of the unit.
  • Operation & Retrofit
    Analysis and Treatment on the Excessive Expansion Difference of Medium Pressure Cylinder During the Cold Start-up in a 350MW Supercritical Steam Turbine
    Wu Xingwu, Yao Zhihong, Qiu Chen, Tan Rui, He Xinrong
    2023, 37(1): 71-74. https://doi.org/10.19806/j.cnki.fdsb.2023.01.013
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    For the 350 MW super critical units in a power plant, the expansion differences of the medium pressure cylinders were excessive during the cold start-up of the steam turbines in the No.5 and No.6 units, which leads to the long start-up time of the units and the operation delay of the denitration system. Analyses were conducted on the excessive expansion differences of the medium pressure cylinders, and following corresponding measures were carried out, such as adjusting the K value of the shaft clearance, adding the heating system between the inner-shell and outer-shell of the medium pressure cylinder, optimizing the cold start-up process, etc. Results show that, through adopting corresponding measures, the cold start-up processes of the steam turbines in the two units are smoothly, and the units can reach full load with the start-up requirements.