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    Boiler Technology
  • Boiler Technology
    Safety Analysis of Heating Surfaces and Selection of Emergency Water Supply Pump for a 660 MW Ultra-supercritical CFB Boiler Under Power Failure Condition
    LI Yinlong, YANG Dong, LI Weicheng, DENG Qigang, ZHOU Xu, LU Jiayi, ZHOU Qi
    2022, 42(5): 393-401. https://doi.org/10.19805/j.cnki.jcspe.2022.05.001
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    Taking a 660 MW ultra-supercritical circulating fluidized bed (CFB) boiler as the research object, the calculation model of flow and heat transfer on heating surfaces under power failure condition was established, and a calculating program for the transient characteristics of heating surfaces was developed based on Fortran language. Variation laws of working medium and tube wall temperature at the outlet of heating surfaces were calculated when the heat storage of metal tube wall was considered under power failure condition. Results show that the boiler equipped with an emergency water supply pump with a pressure of 35 MPa and a water delivery capacity of 140 t/h can ensure the wall temperature safety of heating surfaces. The results are of great significance for the selection of emergency water supply pump and the treatment of these conditions in (ultra) supercritical CFB boilers with the external bed.
  • Boiler Technology
    Study on NOx Formation Mechanism During the Combustion of Pulverized Coal Gas Flow Blened with LNG
    KANG Zhizhong, ZHANG Xin, DING Xian, ZHAO Hujun, SUN Zhe
    2022, 42(5): 402-406. https://doi.org/10.19805/j.cnki.jcspe.2022.05.002
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    In order to study the effect of adding liquefied natural gas (LNG) on the reduction of NO generation at the swirl burner outlet, the reaction process of gas-phase combustion of LNG blended pulverized coal flow was studied through chemical kinetic analysis method.Results show that when the ratio of LNG was 50%, the volume fraction of NO in the reactor decreased by 16%. Adding LNG had a better effect on reducing the NO concentration at low excess air coefficient (α<1) and the reaction temperature T>1 350 K; In the case of excess air coefficient α<1, increasing LNG commissioning volume promoted the reduction of NO concentration, but in the case of excess air coefficient α>1, increasing LNG had little effect on reducing NO production concentration.
  • Boiler Technology
    Discuss on the Differences of the Calculated Thermal Expansion Stress Range of Thermal Pipings Using Different Codes
    KUANG Jianghong, YU Bin
    2022, 42(5): 407-412. https://doi.org/10.19805/j.cnki.jcspe.2022.05.003
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    The calculation formula for the thermal expansion stress range of thermal piping within the battery limit of the power plant given in active national standard GB/T 32270—2015 "Pressure piping code-Power piping" is different from that in ASME B31.1—2020 "Power piping, ASME code for pressure piping, B31". Using three simple pipeline sections as examples, the thermal expansion stress ranges were calculated using force method according to above mentioned codes. The differences among the calculated results were analyzed. Results show that for plane pipelines and straight sections of spacial pipelines, because of the addition of axial force, the thermal expansion stress ranges calculated by the formula in ASME B31.1—2020 are larger than that calculated by the formula in GB/T 32270—2015. While the thermal expansion stress ranges for the bends of spacial pipelines calculated by the formula in ASME B31.1—2020 may be less than that calculated by the formula in GB/T 32270—2015 due to the effect of torque.
    • Automatic Control
  • Automatic Control
    Design and Implementation of Operating System for Mapping Area Driver-level Equipment Dispatching Based on Controller in Power Plant
    ZHANG Qiang, GAO Sheng, GUO Rong, WANG Yong
    2022, 42(5): 413-420. https://doi.org/10.19805/j.cnki.jcspe.2022.05.004
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    Based on the language and tools of the IEC61131-3 standard control environment in the controller, the field equipment group of the power plant was abstracted into two typical models of mutual exclusion and non-mutual exclusion, and the field device driver-level operating system in the upper mapping area was constructed by using algorithms such as five-state process, bumpless mode switching and double-loop queue, respectively. Combined with the fly ash island bin pump group of circulating fluidized bed boiler and the water pump group of power plant, the mutually exclusive equipment operating system and non-mutually exclusive equipment operating system were designed and implemented respectively. Results show that the application of the operating system optimizes the equipment scheduling and operation efficiency, reduces the workload of personnel operation, and can tap the standby potential of group equipment, so that the state maintenance is realized, and the reliability and economy of the power plant operation are improved.The operating system has good potential for application and popularization.
  • Automatic Control
    Composite Cascade Control Based on Reinforcement Learning for a SCR Denitration System
    CHEN Haowei, JIA Xinchun, SUN Xiaoming, HOU Pengfei
    2022, 42(5): 421-428. https://doi.org/10.19805/j.cnki.jcspe.2022.05.005
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    Aiming at the characteristics of strong disturbance, large delay, large inertia in a selective catalytic reduction (SCR) denitration system, an ITD3-PI composite cascade control algorithm was proposed based on an improved dual-delay depth deterministic strategy gradient (ITD3) algorithm, a PI controller and a disturbance observer (DOB). Firstly, an ITD3 algorithm was proposed according to the PID control scheme, it generated new environmental states by performing differential and integral operations on the errors between the set values and the measured values of the outlet NOx mass concentration, then stored the new states, the measured values and the errors in the experience pool. Secondly, the DOB was used to estimate the disturbance of a denitration process and performed a feedforward compensation. Finally, the proposed ITD3-PI composite cascade control was compared with a TD3-PI composite cascade control, a composite cascade PID control and a cascade PID control. Results show that the proposed method has good performances of fast control speed, small overshoot and strong anti-interference ability,which provides a new thought for the applications of reinforcement learning in a SCR denitration system.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Bearing Fault Diagnosis Based on CEEMDAN Sample Entropy and Convolutional Neural Network
    XIAO Junqing, JIN Jiangtao, LI Chun, XU Zifei, SUN Kang
    2022, 42(5): 429-436. https://doi.org/10.19805/j.cnki.jcspe.2022.05.006
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    Aiming at the problem that it is difficult to extract and identify the fault features of rolling bearing vibration signals under strong noise background, a fault diagnosis method (CEEMDAN sample entropy-CNN) combining complete cnsemble empirical mode decomposition with adaptive noise (CEEMDAN) sample entropy and convolutional neural network (CNN) was proposed. Based on the fractal theory, CEEMDAN algorithm was used to decompose the vibration signal and extract its nonlinear features. The optimal IMF component was selected by fractal box dimension, and the feature vector composed of its sample entropy was input into CNN to realize the classification and diagnosis of bearing faults. Finally, the t-SNE clustering visual analysis was performed on the bearing faults. Results show that compared with empirical mode decomposition (EMD) sample entropy and ensemble empirical mode decomposition (EEMD) sample entropy, the proposed CEEMDAN sample entropy-CNN method has better recognition ability and generalization performance under different working conditions, and its visualization analysis results are more intuitive.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Analysis of Heat Transfer Characteristics of Three-dimensional Tubular Ribbed Chase Change Heat Storage Unit
    REN Zhibin, HUANG He, GAO Jiaxu, ZHAO Ming
    2022, 42(5): 437-443. https://doi.org/10.19805/j.cnki.jcspe.2022.05.007
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    The heat storage and release process of different phase change heat storage models and the influence of inlet fluid temperature on heat storage process were studied by numerical simulation method. Results show that the heat storage and release time of different sections vary greatly along the axial direction, and the natural convection in the axial direction has little effect on heat storage and release. Adding fractal fins can effectively improve the heat storage and release rate. In the process of heat storage, the heat storage time of both model 4 and model 5 can be shortened by 45.4% compared with model 1. In the process of heat release, compared with model 1, the heat release time of model 2- model 5 can be shortened by 12.3%, 13.7%, 27.4% and 34.2%, respectively. Increasing the inlet fluid temperature can significantly reduce the heat storage time, while the increase of heat storage rate decreases gradually. When the inlet fluid temperature is higher than 358.15 K, the effect of inlet fluid temperature on melting time decreases significantly.
  • Engineering Thermophysics
    Study on NOx Emission Mechanism in Dimethyl Ether Counter Flow Diffusion Flame Based on Chemical Explosive Mode Analysis Method
    XIONG Deyang, KANG Yinhu, GAO Xin, WANG Quanhai, LU Xiaofeng
    2022, 42(5): 444-449. https://doi.org/10.19805/j.cnki.jcspe.2022.05.008
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    The application and feasibility of chemical explosion mode analysis (CEMA) method in NOx emission mechanism were studied, so as to reveal the mechanism of chemical reaction on NOx emission path, and find out the key reaction kinetic factors that dominate NOx emission. Results show that the CEMA method can accurately characterize the NOx chemical reaction kinetics. On the stoichiometric equivalent surface, the elementary reactions R309(N+NO=N2+O) and R371(CH+N2=HCN+N) have the most significant effects on NOx emission at low and high stretch rates, respectively. Reducing reaction rate of the elementary reactions can greatly control NOx emissions.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Simulation Study on Aerodynamic Performance of Axial Flow Fan with Serrated Flaps Trailing Edge
    ZHENG Nan, YE Xuemin, YANG Tiankang, LI Chunxi
    2022, 42(5): 450-457. https://doi.org/10.19805/j.cnki.jcspe.2022.05.009
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    Taking a two-stage variable pitch axial flow fan as an example, the fan performance, vortex structure and aerodynamic noise were investigated for serrated flaps with different tooth lengths by large eddy simulation (LES), so as to analyze its internal flow characteristics, noise source distribution and noise reduction mechanism. Results show that the serrated flaps can effectively improve the fan performance, and the increase of total pressure is inversely proportional to the tooth length. The maximum efficiency point of the fan with serrated flaps would move to large flow rate side, and the high operation efficiency area becomes wider. With the increase of tooth length, the average static pressure of serrated flaps decreases first and then increases,and the average static pressure of case 4 decreases by 402 Pa compared with the original fan, therefore, the reduction of its high-frequency noise is the most significant. The utilization of serrated flaps can reduce the turbulence fluctuation intensity, the size and distribution area of wake vortices decrease, meanwhile, the number of leading-edge separation vortices decrease. Two pairs of antisymmetric vortices with opposite rotation directions appear at the trailing edge of the serrated flaps, leading to strong interaction between the two and fast energy dissipation, which is the main reason for the noise reduction.
    • New Energy
  • New Energy
    Multiphysics Platform Construction and Seismic Dynamics of Offshore Wind Turbine
    YAN Yangtian, LI Chun, MIAO Weipao, YUE Minnan, NIU Kailun
    2022, 42(5): 458-467. https://doi.org/10.19805/j.cnki.jcspe.2022.05.010
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    In order to study the dynamic response of large offshore wind turbine under earthquake, turbulent wind, wave and current,The finite element model of supporting structure considering the environmental loads and soil-structure interaction was established. the accuracy of finite element model and the necessity of considering soil-structure interaction were verified based on the modal method. And the structural response of large wind turbine was studied. Results show that the dynamic characteristics of the structure are significantly affected by the soil-structure interaction. Under the earthquake loads, the structural response of multiple freedom degrees increases. Due to the effect of wind, wave and current loads, the damping effect of the external load on the support structure is significant. Therefore, the wind, wave and current loads can not be ignored in the study of seismic dynamic response.
    • System Engineering
  • System Engineering
    Study on Load Control Strategy of a S-CO2 Cycle Power Generation System Based on Volumetric Method
    HE Peng, ZHANG Jingxuan, HUANG Weiguang
    2022, 42(5): 468-474. https://doi.org/10.19805/j.cnki.jcspe.2022.05.011
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    Taking a recompression supercritical carbon dioxide (S-CO2) cycle system as the research object, the control strategy of the system in the load reduction process was studied by volumetric method. The dynamic response of the system to the charging and discharging working fluid was emphatically analyzed and the control strategy was optimized accordingly. Results show that the system will have operational instability problems due to the real gas effect of S-CO2 when conventional volumetric method is used to reduce the load (discharge working fluid directly). By increasing the inlet temperature of the main compressor and then discharging the working fluid, the problems can be avoided, and the cycle efficiency loss caused by load reduction can be effectively reduced. The maximum cycle efficiency of the optimized control strategy using supercritical volumetric method can reach 90% of the rated condition at 50% load.
    • Material Research
  • Material Research
    Experimental Study on High-temperature Low Cycle Fatigue Performance of Inconel 617 and C-HRA-2 Alloys for Advanced Ultra-supercritical Units
    ZHOU Gangbao, BIAN Shuang, CHEN Zhenyu, CHEN Zhengzong, BAO Hansheng, ZHANG Naiqiang
    2022, 42(5): 475-483. https://doi.org/10.19805/j.cnki.jcspe.2022.05.012
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    The axial strain controlled low cycle fatigue (LCF) tests of imported and domestic candidate Inconel 617 and C-HRA-2 nickel-based alloys used in advanced ultra-supercritical (A-USC) units at high temperature of 700 ℃ were carried out, in which the strain amplitudes were ranging from 0.25% to 0.75%. LCF properties of two alloys were studied by cyclic stress response, cyclic stress-strain characteristic, fatigue life prediction and fracture morphology analysis. Results show that the cyclic stress response and fatigue life are related to the strain amplitude, and the cyclic hardening degree of C-HRA-2 alloy is significantly higher than that of Inconel 617 alloy, but the peak stress of two alloys after cyclic hardening is similar. The hysteresis loops of two alloys exhibit non-Masing behavior. Using Manson-Coffin model and energy-based method can effectively predict the fatigue life, and the fatigue initiations of two alloys originate from the specimen surface under different strain amplitudes. The fatigue crack propagation of Inconel 617 alloy is transgranular, while that of C-HRA-2 alloy is transgranular and intergranular.
  • Material Research
    Comparative Study of Steam Oxidation Resistance of New Ferritic Heat-resistant Steels
    MA Yunhai, WANG Yanfeng, ZHANG Zuogui
    2022, 42(5): 484-491. https://doi.org/10.19805/j.cnki.jcspe.2022.05.013
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    Oxidation behavior of G115 and T92 steels was investigated at 650 ℃/27 MPa in supercritical steam. After oxidation for 2 000 h,scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), electron backscatter diffraction (EBSD) were employed to determine the morphology, chemical composition and microstructure of the oxide scale, respectively.Results show that compared with T92 steel, G115 steel shows the better steam oxidation resistance. For these two ferritic steels, the oxide scale consists of three parts, the outer layer of thick columnar magnetite, the inner layer which main constituent is fine (Fe,Cr) spinel and a small amount of magnetite and the inner oxidation zone which main constituent is the mixture of FeO+Cr2O3. With the oxidation proceeding to 2 000 h, the holes in the outer layer of the oxide film of the two ferritic steels increase, and defects such as penetrating cracks appear in the oxide film. Simultaneously , the tendency of oxide exfoliation increases.