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  • 2014 Volume 34 Issue 9
    Published: 15 September 2014
      
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  • Simulation on Combustion Process and Analysis on Slagging Behavior of a 660 MW Swirlopposed Coalfired Boiler
    DENG Niannian,ZHOU Zhen,XIAO Xiang,HUANG Xinya
    2014, 34(9): 673.
    Abstract ( )   Knowledge map   Save
    To analyze the factors influencing the slagging behavior of a 660 MW swirlopposed coalfired boiler, numerical simulations were carried out to its combustion process respectively under 100%, 75% and 50% unit load, with coal particles of different sizes. Results indicate that in the case of 100% load, slagging mostly tends to be formed in the middle area of both the right and left wall at elevation 1924 m, and in the case of 75% load, slagging is most probable to be formed in the middle area of both the right and left wall at elevation 2123 m, and for the 50% load, slagging is least probable in the furnace. For coal particles of size 10 μm, slagging tends to be formed in the middle area of both the right and left wall at elevation 2328 m, and the finer the coal particles, the faster the ignition of pulverized coal, resulting in improved temperature and increased area of slagging in the furnace.
  • Numerical Simulation on Boiler Tube Leakage Detection and Study on the Location Algorithm
    SHEN Guoqing,ZHANG Shiping,AN Liansuo,FENG Qiang,XU Weilong
    2014, 34(9): 678.
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    To accurately locating the boiler tube leakage point, numerical simulation was conducted on the flow field and sound field formed by the leakage jet flow. The Chan algorithm in communication engineering was introduced to the location detection of boiler tube leakage, and test studies were made respectively under open environment, laboratory environment, simulated cool furnace noisefree environment and simulated cool furnace highnoise environment. Results show that the axial velocity of leakage jet flow is the main reason of leakage sound propagation and disturbance, and the noise radiation has directive property in the far field. The sound power level of leakage flow near jet exit is the highest, which decreases with the rise of distance to the jet exit along symmetrical axis. The intensity of sound field increases with rising pore diameter of leakage flow. The sound power level is basically the same under same pore diameter but different steam conditions. The location error of Chan algorithm is within the allowable range, indicating high resolution of the algorithm.
  • Numerical Simulation on Flow Characteristics in Densephase Zone of a HighLow CFB Boiler
    SONG Xingfei,WANG Qinggong,BIE Rushan,JI Xiaoyu,CHEN Pei,LIU Qianqian
    2014, 34(9): 685.
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    Based on kinetic theory of granular flow, numerical simulation was conducted on the gassolid twophase flow in densephase zone of a highlow circulating fluidized bed boiler using EulerEluer twofluid model and standard kε model in Fluent software, so as to analyze the variation law of flow velocity and pressure distribution of particles in the internal circulation process, and to study the effects of bed velocity on the flow characteristics in densephase zone. Results show that at the secondary bed velocity u2=1.5 m/s, the timeaveraged volume fraction of particles reduces in primary bed and increases in secondary bed, while both the standard deviation of pressure drop and reflux velocity of particles increase, with the rise of primary bed velocity; whereas, at the primary bed velocity u1=4.0 m/s, with the rise of secondary bed velocity, the reflux velocity of particles reduces, and the standard deviation of pressure drop increases first and decreases later on, which reaches the maximum in the case of u2=2.0 m/s.
  • Chlorine Corrosion Characteristic of Boiler Heating Surface Due to Cofiring of Biomass and Coal
    WU Yue,WANG Yongzheng,LI Xiujuan,YUE Maozhen,JIANG Lei
    2014, 34(9): 690.
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    To study the characteristic of chlorine corrosion on boiler heating surface due to cofiring of biomass and coal, simulation tests were carried out in a tube furnace using weight gain method under different gaseous and ash deposition conditions, so as to obtain the corrosion behavior for different tube materials, HCl concentrations and at different temperatures. Results show that the characteristic curves of chlorine corrosion on all the metals follow the parabola regularity, and 15CrMoG tube has better corrosion resistance than 12CrMoVG tube; the corrosion rate has a linear relationship with the HCl concentration, and alkali chloride is more corrosive than HCl to above materials; the corrosion rate has an exponential relationship with temperature, which increases rapidly with the rise of temperature from 550 ℃ to 600 ℃.
  • Numerical Simulation on Film Cooling Effectiveness with Injection from Sister Holes
    ZHANG Ling,GUO Ruihong,GUO Dafei,LI Hao
    2014, 34(9): 696.
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    Using Fluent software to solve the NavierStokes equations, the effects of sister hole injection on both the film cooling effectiveness and the surrounding temperature field were studied with Realizable kε  turbulence models under three angle conditions, namely 30°, 45°  and 60°. Results show that the film cooling effectiveness with injection from sister holes is improved by interaction of vortices from two secondary holes and a main hole, which pulls the jet center that has been raised to the crosswise direction, damages the counterrotating vortex pair, changes the lift force to transverse tensile force, so as to maintain the flow adhesion and improve the transverse distribution of coolant. The highest film cooling effectiveness is to be achieved at an angle of 30°  between two sister holes.
  • Uncertainty Analysis of Wetness Measurement System by Microwave Resonant Cavity
    QIAN Jiangbo,YAN Xiaozhe,HAN Zhonghe,LI Hengfan
    2014, 34(9): 701.
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    Based on relations for wetness measurement by microwave resonant cavity, the sensitivity coefficients of relevant relations were deduced, and the uncertainty of direct measurement parameters was analyzed, such as pressure and frequency, etc. Taking the steam of different pressure and wetness as an example, the uncertainty of various calculation parameters in the wetness measurement relations was studied, while standard uncertainty of the wetness measurement system was combined, and the influence of both steam pressure and wetness on the system uncertainty was analyzed. The comprehensive system uncertainty was identified, considering parameters measurement, cavity heat expansion, sampling error, sedimentary water film on inner surface of cavity and so on. Results show that the uncertainty of the wetness measurement system is less than or equal to 0.764%, and its combined standard uncertainty increases with the rise of steam pressure and wetness. The system uncertainty is slightly affected by pressure measurement, but greatly influenced by frequency measurement. Therefore to guarantee the precision of a wetness measurement system, it is important to measure the resonant frequency accurately.
  • Steadystate Detection of Power Plant History Data Based on Adaptive Gauss Filter
    GAO Meng,LIU Jizhen,WANG Ruiqi,ZHANG Heng,ZHANG Xuan
    2014, 34(9): 708.
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    Combining the denoising algorithm based on adaptive Gauss filter with the Rstatistic method, a steadystate detection was carried out to power plant history data. Taking the total air volume data of a 1 000 MW unit as an object of study, simulation comparison was made between the previously proposed method and the median filter method under same working conditions. Results show that the method based on adaptive Gauss filter has better denoising effectiveness and larger retention capacity on point mutation information, which is of high sensitivity in short time steadystate detection, and of high accuracy in switching boundary identification between steadystate and unsteadystate detection.
  • An Online Transient Temperature Monitoring System for Boiler Drums
    LI Bin,CHEN Feng,SHI Liangxiao
    2014, 34(9): 714.
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    To monitor the transient temperature field of boiler drum, a calculation model was set up based on inverse method, with which the transient temperature was obtained by solving the ordinary differential equations transferred from partial heat conduction equations using inverse method with volume control ideas according to the temperature measured by thermocouples mounted on outer surface of the drum. The calculation results were verified by onedimension heat conduction analytical solutions and twodimension heat conduction Ansys numerical solutions for infinitely long cylinder as well as by experimental data. Results show that there is a good agreement among above three calculation methods, proving the inverse method to be highly accurate, which therefore can be used in online transient temperature monitoring of boiler drums.
  • Calculation Model for Transient Characteristics of Deaerator in Ultra Supercritical Unit During RB Process
    ZHU Bao,QIAN Haiping,WU Meng,CHEN Liqiang,WANG Chongru,SHENG Deren
    2014, 34(9): 720.
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    To solve the problem of feed pump cavitation that may occur during load rejection process of an ultra supercritical unit due to the drop in available net positive suction head (Na) of feed pump, a mathematical model to calculate the transient characteristics of deaerator and the maximum Na decrease (ΔNa,max) of feed pump was proposed, based on theoretical analysis and experimental research on the run back (RB) transient process of deaerator. Resnlts show that comparison results between calculated and experimental data prove the proposed model to be highly accurate. To effectively reduce the ΔNa,max, countermeasures may be taken by either controlling the fluctuation of water volume in deaerator, or reducing the downcomer length under the premise keeping the mounting height of deaerator unchanged.
  • Application of MPSHPII Mediumspeed Coal Mill in Highmoisture Coalfired Units
    SUN Ke,JIN Shiqi,QIN Dachuan
    2014, 34(9): 725.
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    To overcome the difficulty in calculating the maximum output and optimizing the operation of a MPSHPII mediumspeed coal mill, a calculation method was proposed for the new type of mill, and subsequently the calculation results were compared with actual experimental data. Operating conditions suitable for the coal mill were put forward through studies on its operating characteristics, during which the effects of primary air volume, separator baffle angle, mill output and loading force on both the pulverized coal fineness and the unit consumption were obtained. Results show that via the proposed method, the mill output can be accurately calculated, which, however, is still limited by drying output in the case high moisture coal is pulverized.
  • Experimental Study on Shaft Torque Fluctuation for Variable Frequency Driven Motors
    LI Nianzai,GUO Yujie,ZHANG Xiaobin,YANG Jiangang
    2014, 34(9): 731.
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    To study the torsional vibration mechanism of variable frequency driven (VFD) motors, an analysis model on harmonic frequency of the shaft torque under SPWM operation mode was set up using signal analysis method, with which shaft torque pulse characteristics during run up process were tested on a VFD motor test rig. Results show that the spectrum of shaft torque pulse includes not only multiple integer harmonic components of speed frequency, but also multiple interharmonic components around the speed frequency; the amplitude of harmonic component reduces with the rise of component order; lateral vibration has slight influence on the dynamic torque, of which the amplitude increases with rising speed; in case of disturbance, many frequency components occur with higher amplitude than the case without disturbance.
  • Analysis of Separation Vortex and Broadband Noise Radiation on Fan Blade Surfaces
    WAN Jianfeng,YANG Ailing,DAI Ren
    2014, 34(9): 736.
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    Using large eddy simulation method and FWH acoustic model, the flow field, surface pressure fluctuation and broadband noise radiation of a ClarkY airfoil were analyzed under low Mach number flow conditions. Simultaneously, the spectrum of blade surface pressure was compared with that of the far field sound pressure. Results show that the near wall separation vortex has a correlation with the blade surface pressure fluctuation; each pressure fluctuation is related with a pulsating vortex. The radiation capacity at far field of separation vortex is very small, and the broadband noise mainly comes from the pressure fluctuation caused by both the leading edge impingement and the trailing edge separation; the radiation capacity at leading edge is larger than at trailing edge.
  • A New Performance Reliabilitybased Method for Power Curve Assessment of Wind Turbines
    RUI Xiaoming,ZHANG Muyong,HUO Juan
    2014, 34(9): 742.
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  • Mechanical Properties and Structure of Steel 30Cr2Ni4MoV for AP1000 Steam Turbine LP Rotors
    CUI Zhengqiang,WANG Yanfeng,SHI Kexian
    2014, 34(9): 748.
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    Mechanical properties and structure of steel 30Cr2Ni4MoV at different locations of an LP steam turbine rotor were researched by chemical composition and microstructure analysis, room and hightemperature tensile tests, roomtemperature impact and hardness tests, as well as fracture appearance transition temperature (FATT) tests, so as to study the variation mechanism of its mechanical properties and structure. Results show that at different locations of rotor, the segregation of chemical composition is relatively small, the change of grain size is not obvious, the tensile strength and hardness are very uniform, but the roomtemperature impact values, the energy of fracture transition plastic and the FATT are quite different. Both the roomtemperature impact value and the energy of fracture transition plastic on rotor surface are higher than at rotor core, however, the FATT on rotor surface is lower than at rotor core.