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    Boiler Technology
  • Boiler Technology
    Study on Tube Wall Temperature of Power Plant Boilers Based on Coupled Thermal Hydraulic Analysis
    YU Yuexi, LIAO Hongkai, WU Yanling, ZHONG Wei
    2015, 35(1): 1-7.
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    A three-dimensional sliced and segmented calculation model was established for tube wall temperature of superheater by meshing the high-temperature flue gas region of boiler, with which the flue gas temperature in high-temperature region was on-line calculated based on furnace combustion and heat transfer mechanism, while the heat flux of all tubes and working fluid mass flow in parallel pipelines were obtained using iteration method, and finally the wall temperature of all pipelines and tube segments was calculated. Results show that the "Remote Monitoring Subsystem for Furnace Tube Safety Operation of Power Plant Boilers" developed according to the model and algorithm proposed above is able to perform precise online analysis, calculation and overheating warning of tube wall temperature, which is therefore of positive significance to the safety and stable operation of thermal power units.
  • Boiler Technology
    Numerical Simulation and Optimization of an SBS-II Oxy-fuel Combustion Boiler
    WANG Peng, LIU Zhaohui, LIAO Haiyan, LI Yanbing, HUANG Jun, CHEN Yinbiao
    2015, 35(1): 8-12.
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    Taking a pilot-scale SBS-II oxy-fuel combustion boiler as an object of study, the kinetic mechanisms and physical parameters of the combustion process were analyzed and modified, while the in-furnace flow and temperature field were studied under oxy-fuel conditions by numerical simulation. Results show that the combustion of pulverized coal becomes quite intensified after mixing with primary and secondary air under oxy-fuel conditions, and both the flame shape and temperature distribution under 26% oxygen concentration are basically the same as under air combustion conditions, matching with the heat-transfer requirements. With the rise of distance to the burner opening, the internal recirculation zone (IRZ) enlarges first and reduces later on, but the location corresponding to the maximum value remains unchanged. The recirculation flow reaches the maximum under the swirl number of 0.8, in which case, obviously stabilized flame and high burnout rate are obtained.
  • Boiler Technology
    Simulation Study on Reconstruction of 3D Temperature Field in Boiler Furnace by Acoustic CT Algorithm
    AN Liansuo, WANG Ran, SHEN Guoqing, ZHANG Shiping
    2015, 35(1): 13-18.
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    To realize the real-time monitoring of temperature field in boiler furnace, two computer tomography (CT) algorithms were proposed, including the algebraic reconstruction technique (ART) and simultaneous iterative reconstruction technique (SIRT), with which three typical temperature field models were reconstructed for flame distribution in boiler furnace, such as the single-peak model, double-peak model and four-peak model, and subsequently the simulation results were compared between above two algorithms, while their anti-noise capability was analyzed. Simulation results indicate that these two algorithms can be used to reconstruct the 3D temperature field in boiler furnace, and both of them have advantages and disadvantages. For power boilers with complicated combustion conditions, SIRT algorithm has better stability due to its superior anti-noise capability.
  • Boiler Technology
    Mechanism Study on the Effect of Magnesium-based Flux on the Fusibility of Coal Ash with High Fusion Point
    FAN Haojie, HE Kejia, LIU Junjie, ZHANG Zhongxiao
    2015, 35(1): 19-24.
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    The effect of magnesium-based flux on the fusibility behavior of Huainan coal ash with high fusion point was studied by adding different amount of magnesium-based flux to the coal ash. Results show that for Huainan coal ash, the ideal addition is 5%, in which case the coal ash fusion point may be reduced to 1 350 ℃; the high fusion point of Huainan coal ash is found to be caused by the refractory mineral mullite by XRD and SEM analysis, which may be reduced by Mg2+ reacting with mullite to form eutectic minerals, such as cordierite and Ringwoodite, etc. Through quantum chemical calculation, the mullite system is proved to be completely stable, and the Mg2+ could easily enter into mullite crystals from the unsaturated O(7) and O(13), which results in both the rupture of the covalent bond between Al(1)-O(13) and Al(8)-O(13), and the distance enlargement between two Si atoms in silicate, and finally leads to the lattice recombination of mullite.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    High-temperature Creep Strength Analysis for IP Rotor of an Ultra-supercritical Steam Turbine
    WU Qiong, WANG Weizhe, ZHANG Junhui, HU Yifeng, GAO Qinghui
    2015, 35(1): 25-29.
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    High-temperature creep strength of the intermediate-pressure (IP) rotor in an ultra-supercritical steam turbine was numerically investigated using Abaqus, so as to obtain the temperature, stress and strain field, under steady-state operation conditions of rotor, during which the influence of multiaxial effect on the creep strength was taken into consideration, and the continuous damage evolution pattern on characteristic point was analyzed. Results show that the mutiaxial effect has a significant influence on the creep strength; stress redistribution happens during initial stage of steady-state operation of rotor, which impacts the continuous damage evolution pattern.
    • Automatic Control and Detecting Diagnosis
  • Automatic Control and Detecting Diagnosis
    Feedforward-Feedback Control of the Once-through Boiler-Turbine Coordinated System Based on Stable Inversion
    LI Lu, LIU Jizhen, XIANG Dan
    2015, 35(1): 30-36.
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    To improve the control performance of once-through boiler-turbine coordinated system, a feedforward-feedback control method was proposed based on the nonlinear model of once-through boiler-turbine unit, which is realized by: first establishing a nonlinear model with certain precision and suitable for controller design through reasonable reduction, next introducing the theory of stable inversion to seek inverse solution of the model, then making the unit output reach around the set points quickly by feedforward control via inversion system, and finally designing the feedback controller with multiple output variables to eliminate tracing error caused by external interference. Simulation tests were carried out at state disturbance and set point perturbation under different static operation conditions, and the results were compared with the nonlinear internal model control method, which prove the feedforward-feedback control system based on stable inversion to have excellent set point tracing capability.
  • Automatic Control and Detecting Diagnosis
    Real-time Estimation of Torsional Stress in Turbo-Generator Shafts Caused by Frequent Subsynchronous Oscillation with Low Amplitudes
    GU Yujiong, CHEN Dongchao, XU Jing, REN Zhizheng, HE Chengbing
    2015, 35(1): 37-44.
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    A novel method was proposed to realtimely estimate torsional stress in turbo-generator shafts caused by frequent subsynchronous oscillation (SSO) with low amplitudes in high-voltage direct-current (HVDC) power transmission systems, with which the torque in each weak cross section of shafts can be calculated by combining the torsional angle signal and 3-phase generator voltage and current signals collected in real time with torsional vibration modes and torsional rigidity in each weak position, and subsequently real-time torsional stress can be obtained based on the weak section structure characteristics and stress concentration factor. The method was used to estimate the torsional stress history of shafts in a 1 000 MW turbo-generator set, which had suffered an actual SSO with low amplitudes caused by HVDC. Results show that the proposed real-time calculation method for torsional stress is simple, accurate and reliable without complicated mathematical calculation, which is easy to implement via computer.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Characteristic Study on Syngas Flames with Combined CO2 Dilution and Micro-mixing Injection Combustion
    ZHANG Yongsheng, ZHANG Hailong, TIAN Long, FU Zhongguang, ZHANG Kai
    2015, 35(1): 45-49.
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    A characteristic study was conducted to syngas flames with combined CO2 dilution and micro-mixing injection combustion. Results show that the combined CO2 dilution and micro-mixing injection combustion is an effective way to reduce the NOx emission from syngas diffusion flames. Under experimental conditions, the emission of NOx is lower than 2 mg/m3, and the emission of CO is lower than 10 mg/m3, while the latter decreases with the rise of flame power; the temperature respectively at combustor exit, furnace wall and nozzle exit increases with the rise of flame power.
  • Engineering Thermophysics
    Experimental Study on Surface Wave Characteristics of Laminar Falling Films Along Vertical Plate
    LIU Mei, WANG Songling, LI Xiaoen, WU Zhengren
    2015, 35(1): 50-54.
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    Spatial and temporal characteristics of the surface wave on laminar falling films along vertical plate were analyzed in a self-developed experimental setup. The shape pattern, velocity and frequency of the surface wave were studied using CCD shadowgraph method in the range 600-1 300 for Re, and simultaneously statistical characteristics of the velocity and frequency were analyzed based on experimental measurements combined with Matlab image processing. Results show that both the velocity and the velocity range of solitary wave are directly proportional to the Re, but the frequency of solitary wave has weak dependence on the Re and the location of measurement. The frequency of solitary wave is found to be in the range of 7-13 Hz through Matlab processing.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Modeling and Simulation of MPS Medium Speed Coal Mills
    ZENG Deliang, GAO Shan, HU Yong
    2015, 35(1): 55-61.
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    To improve the safety and economy of coal mill operation, a dynamic mathematical model was established for MPS medium speed coal mill based on mass and energy balance. Considering the impact of coal moisture on the energy balance and taking the pulverized coal moisture as a state output, the model parameters were identified with historical data using genetic algorithm, and the internal states of coal mill was estimated by an extended Kalman filter (EKF) method, while the model states and outputs were validated with two sets of on-site data. Results show that the states estimated by EKF method are consistent with the model states, and the model outputs are in good agreement with those of online measurements, which prove the coal mill model established to be effective in predicting the dynamic performance of coal mills.
  • Auxiliary Equipment Technology
    Characterization on Sound Pressure Signal of an Axial Flow Fan with Abnormal Blade Angle Based on Complexity Algorithms
    LI Chunxi, LIN Qing, YE Xuemin
    2015, 35(1): 62-69.
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    Taking a variable pitch axial flow fan of OB-84 type as an example, the distribution of sound pressure in each region was simulated by large eddy simulation with FW-H noise model, and the results under abnormal installation angles were compared with that under normal conditions. Based on the analysis results of power spectral density, wavelet decomposition and reconstruction were conducted to the original sound pressure signal, while characteristic entropy of the reconstructed signal was abstracted, so as to study the characterization capabilities of three complexity algorithms. Results show that the sound pressure in various regions of the axial flow fan is obviously different in time domain, and the pulsation morphology, interval and amplitude vary with the abnormal installation angle. The noise signal is featured by discrete peaks in low-frequency region, with energy level gradually reduced, while broadband noise becomes notable with the rise of deviation degree. The characteristic entropy in blade region is the least due to uniform regularity, and the aerodynamic characteristics and noise signal remain relatively stable in afflux section and diffusion section, thus the abnormal degree of blade installation angle could be evaluated by approximate entropy, sample entropy and Lempel-Ziv complexity.
  • Auxiliary Equipment Technology
    Determination and Application of Condenser Optimum Vacuum Under Variable Conditions of Steam Turbine
    XU Xing, HUANG Qilong, DAI Weibao, QIN Huimin, CAI Pei
    2015, 35(1): 70-75.
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    Based on operation characteristics of mutual coupling between steam turbine and the condenser, numerical models were set up for characteristic calculation of the condenser under variable conditions of the steam turbine, while a calculation method was proposed for optimum vacuum of the condenser. Models reflecting the influence of condition deviation on optimum vacuum of the condenser were established, which were subsequently applied for operation optimization of the circulating water system in a 330 MW unit under variable working conditions. Results show that the condenser optimum vacuum varies with the operation condition of the steam turbine, the model newly established is proved to be practicable in operation optimization of the circulating water system, due to its strong capability in determination of the optimum vacuum.
    • Environmental Science
  • Environmental Science
    Optimization on Lean Solvent CO2 Loading in Coal-fired Power Plants with Large-scale CO2 Capture
    LIU Wenyi, TANG Baoqiang, XU Gang, HU Yue, YANG Yongping, SONG Xiaona
    2015, 35(1): 76-82.
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    To solve the high energy consumption problem in CO2 capture of coal-fired power plants, an optimization on lean solvent CO2 loading was conducted, based on a comprehensive consideration of the mutual effects among the steam-water system, decarbonization unit and the multistage CO2 compression unit. Results show that the regeneration energy consumption of decarbonization unit increases first and decreases later on with the rise of lean solvent CO2 loading, which reaches the minimum at the lean solvent CO2 loading of 0.26 mol/mol; the power consumption of auxiliary pump increases with the rise of lean solvent CO2 loading at different regeneration pressures; in the case that the CO2 capture ratio remains unchanged, the CO2 compression power consumption hardly changes with the lean solvent CO2 loading. For power plants with large-scale CO2 capture, the power supply efficiency increases first and decreases later on with the rise of lean solvent CO2 loading, and the optimum power supply efficiency can be obtained at the lean solvent CO2 loading of 0.26 mol/mol and the pressure of 250 Pa.
    • Nuclear Technology
  • Nuclear Technology
    Running Parameters Optimization Design and Flow CoastdownTransient Analysis for Main Circulating Pump of Nuclear Power Plants
    LI Guijing, YAN Changqi, WANG Jianjun
    2015, 35(1): 83-88.
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    Researches were made on optimization design of a main circulating pump by establishing a calculation model based on self-developed improved complex shape algorithm to minimize its volume under the premise of meeting the given restraint conditions. In view of the fact that it is one of the essentials to accurately calculate the lowering speed of reactor coolant flow in reactor safety analysis, an assessment was conducted on the flow coastdown transient process of optimal results, under coastdown conditions before startup of the passive residual heat removal system, with the transient calculation model of main circulating pump. Results show that significant effects can be obtained for the main circulating pump through above optimization, and the coolant pumping time of optimization model is close to the prototype, with safety not worse than the prototype.