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    Boiler Technology
  • Boiler Technology
    Cause Analysis and Treatment of Crack Failures on Upper Part of Front Wall in a 600 MW Supercritical W-flame Boiler
    TANG Daojian, XIE Zhiwen, LIU Ruidong, XIONG Xianwei,LI Yupeng, YANG Taiyong, HUANG Yunxiu
    2015, 35(12): 949-955.
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    To handle the crack failure occurring on upper part of front wall in early operation of a supercritical W-flame boiler, an analysis was performed based on onsite measurements of the steam temperature, while in-furnace simulation calculation and hydrodynamic check calculation were conducted, after which the failure was found to be caused by large deviation of steam temperatures. Results show that the too large deviation of steam temperatures leads to the deformation and cracking of front water wall in the upper furnace. The problem has finally been tackled through operation adjustment, overhaul and technical retrofit, thus obtaining safe and stable operation of the boiler.
  • Boiler Technology
    Numerical Simulation on MILD-Oxyfuel Combustion of Pulverized Coal at Different Excess Oxygen Coefficients
    PAN Cong, ZHANG Liqi, MAO Zhihui, ZHENG Chuguang
    2015, 35(12): 956-963.
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    To study the effects of excess oxygen coefficient on the MILD-Oxyfuel combustion of pulverized coal, the MILD-Oxyfuel combustion process was numerically simulated. Taking a 0.3 MW vertical furnace for pulverized coal combustion as an object of study, numerical calculations were carried out under 8 cases respectively in the mode of MILD combustion and MILD-Oxyfuel combustion at excess oxygen coefficients of 1.20, 1.15, 1.10 and 1.05, etc., with the conventional swirl combustion at excess oxygen coefficient of 1.20 as the reference case. Meanwhile, the distribution of furnace temperature and volumetric concentration of CO and NO were analyzed and compared under 9 cases. Results show that at the same excess oxygen coefficient, the temperature in MILD-Oxyfuel combustion mode is lower and more uniformly distributed than that in the mode of MILD combustion; whereas in the same combustion mode, the combustion status at excess oxygen coefficient of 1.20 is similar with that at excess oxygen coefficient of 1.15, and the temperature distribution is the most uniform at excess oxygen coefficient of 1.10. The volumetric concentration of NO is reduced by 40% in both the modes of MILD and MILD-Oxyfuel combustion, but the excess oxygen coefficient affects little on the NO volumetric concentration.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    An Evaluation Model for the Creep Damage of Gas Turbine Blades and Its Application
    ZHOU Dengji, ZHANG Huisheng, SU Ming
    2015, 35(12): 964-969.
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    To obtain the temperature and stress of turbine blades, a performance simulation model, a blade temperature model and a blade stress model were respectively set up for the gas turbine. Simultaneously, a model for evaluation of turbine blade damages was established based on Larson-Miller parameters obtained by creep experiments, which was used to determine the planning of overhaul period under both time-based and condition-based maintenance system. Results show that the influence of compressor faults on creep life is greater than that of turbine failures, and the compressor blade damage is of the gas path fault maximally impacting the creep life. Therefore the model can be used to guide actual maintenance activities upon calibration.
    • Automatic Control and Detecting Diagnosis
  • Automatic Control and Detecting Diagnosis
    Study on Boiler Superheated Steam Temperature Control System Based on TDFMD PID
    WU Dandan, ZHANG Lixiang, WANG Jungang
    2015, 35(12): 970-974.
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    Dynamic characteristics of boiler superheated steam temperture with large delay, great inertia, non-linearity and time-varying behavior were analyzed under disturbance of attempering water flow, for which a two-degree-of-freedom model driven PID (TDFMD PID) cascade control system was designed, and subsequently a comparison of control performance was made between traditional PID and TDFMD PID cascade temperature control system. Results show that, featured by simple structure, good timeliness, convenient parameter adjustment, strong tracing and anti-disturbance capability, the TDFMD PID cascade steam temperature control system helps to greatly improve the dynamic control quality of relevant control systems.
  • Automatic Control and Detecting Diagnosis
    Application of Empirical Wavelet Transform in Fault Diagnosis of Rotary Mechanisms
    XIANG Ling, LI Yuanyuan
    2015, 35(12): 975-981.
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    A signal processing method was proposed for fault diagnosis of rotary mechanisms based on empirical wavelet transform (EWT). The specific way is to divide the Fourier spectrum of relevant signals, and then to filter the divided spectrum with a set of newly built wavelet filter bank to get a group of single component ingredients, and finally to transform every single component ingredient by Hilbert method so as to obtain the instantaneous frequency and amplitude. To verify the effectiveness of the method, a comparison was made to the performance of EWT and empirical mode decomposition method in diagnosing fault signals coming from both simulation and typical experimental rotors. Results show that the EWT method can accurately analyze the mechanical fault signals and the failure eigenvalues are evident, which may be applied in fault diagnosis of rotary mechanisms.
  • Automatic Control and Detecting Diagnosis
    Quantitative Identification of Unbalance in a Rotor System Based on Surrogate Model
    GU Yujiong, CHEN Dongchao, XU Jing, HE Chengbing
    2015, 35(12): 982-987.
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    A novel method for quantitative identification of unbalance in a rotor system was proposed based on surrogate model. Firstly, training samples were obtained based on Latin hypercube sampling (LHS) and finite element model of the rotor system. Then the support vector regression optimized by particle swarm optimization algorithm (PSO-SVR) was adopted to construct surrogate models so as to set up a relation between the unbalance parameters and corresponding vibration dynamic responses. To realize quantitative identification of the unbalance, objective functions were constructed to solve the unbalance parameters, of which the global searching ability was enhanced with the aid of above surrogate models and the particle swarm optimization algorithm. Results show that the method proposed can effectively identify unbalance parameters in the rotor system, even if small errors exist in the finite element model. However, an accurate finite element model is still an important guarantee for obtaining accurate identifying results.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Experimental Study on Heat Transfer and Flow Resistance of Multi-spiral Groove Enhanced Tubes
    HU Zhiming,YUAN Yichao,LIU Yuzheng
    2015, 35(12): 988-992.
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    To obtain the heat transfer and resistance characteristics of multi spiral groove enhanced stainless steel tubes during operation of the power plant condenser, experimental tests were conducted on the tubes under steam coagulation conditions by simulating the operation condition of the condenser, based on which corresponding formulae to calculate the heat transfer and flow resistance were deduced. Results show that the heat transfer of tubes with multi-spiral grooves is remarkably higher than that of smooth tubes| In the experimental range, the heat transfer coefficient of panel 2 and panel 3 made of multi-sprial grooved tubes is respectively 13.8% and 14.8% higher than that of panel 1 made of smooth tubes, and panel 3 is bettter than panel 2 in heat transfer due to its smaller screw pitch. The flow resistance of panel 2 and panel is 8.7% and 10.7% higher than that of panel 1, resulted from the drag effect of multi spiral grooves.
    • Environmental Science
  • Environmental Science
    Effects of Microwave Drying on Fe-based Catalysts for Low-temperature SCR of NOx with NH3
    CAI Sen, GUI Keting
    2015, 35(12): 993-997.
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    To prepare catalysts for selective catalytic reduction of NOx with NH3, experimental tests were carried out to study the catalytic activity and resistance to SO2 of 8Mn-8Fe/Al2O3 Fe-based supported catalysts respectively dried by microwave radiation and ordinary methods, of which the structure features were analyzed with the method of SEM, XRD and BET. Results show that at the temperature lower than 180 ℃, both the catalytic activity and resistance to SO2 of the Fe-based supported catalyst dried by microwave radiation are obviously superior to that dried by ordinary method, due to the highly dispersed particles, finer catalyst grains, improved pore structures and larger specific surface areas, etc, thus resulting in higher denitrification efficiency. The denitrification efficiency of Fe-based supported catalysts dried by microwave radiation is 30% higher than that by ordinary methods, at the temperature of 90 ℃.
  • Environmental Science
    Experimental Study and Numerical Simulation on Spray Characteristics of Different Nozzles
    LIN Hongliang, LIU Daoyin, LIU Meng, CHEN Xiaoping
    2015, 35(12): 998-1005.
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    The effects of following factors on the spray characteristics of single- and two-phase nozzles were experimentally studied, such as the liquid pressure, air-liquid ratio, axial distance and radial distance, etc., while the influence of incidence angle of air flow and horizontal space between two nozzles on the spray characteristics of two-phase nozzles was numerically simulated using the nozzle spray model newly set up. Results show that the droplet mean diameter of single-phase nozzles reduces with the rise of liquid pressure, which increases with the rise of both axial and radial distance. The droplet mean diameter of two-phase nozzles reduces with the rise of air-liquid ratio, which reduces first and increases later on with the rise of axial distance. The dispersion angle of air flow field is always kept at 23.5°, not affected by the incidence angle of air flow. The space between two nozzles has little influence on gas flow field of both the nozzles, and the droplet mean diameter reduces first and increases later on along the axial direction.
    • New Energy
  • New Energy
    Effects of Heterogeneous Underlying Surface on Wake Flow of Wind Turbines
    WU Zhengren, ZHAI Yunlei, LIU Weiwei, WANG Songling
    2015, 35(12): 1006-1011.
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    The effects of underlying surface on velocity and turbulent kinetic energy in the downstream of a wind turbine were simulated using Fluent software based on newly established models of wind turbine and wind farm, by setting the underlying surfaces according to different roughness of four terrains, and by taking the corresponding wind velocity profiles as the inlet boundary conditions. Results show that with the rise of terrain roughness, the downstream velocity of wind turbine reduces gradually, and the ratio of inlet to outlet velocity at hub height declines also. The speed recovery rate is 98%, 98%, 94% and 92% respectively from terrain A to terrain D. The turbulent kinetic energy becomes more disorderly with the increase of terrain roughness. Different underlying surfaces would lead to different downstream flows, and would especially result in different wind speed and turbulent kinetic energy in the near surface.
  • New Energy
    A Control Strategy for Vertical Axis Wind Turbines with Flaps
    LI Runjie, LI Chun, YANG Yang, NIE Jiabin
    2015, 35(12): 1012-1017.
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    A two-dimensional numerical simulation was conducted to vertical axis wind turbines (VAWT) based on SST k-ω turbulence model, following which an inverse function control strategy was put forward to improve the rotating flow field of wind turbine through swinging of the flaps. Simultaneously, the flow field and vorticity of relevant wind turbines were analyzed, and a comparison of torque coefficient was made under the condition with and without inverse function control strategy. Results show that the control strategy helps to make the wind turbine blade completely lie within the critical angle of attack, weaken the large scale vortex in trailing edge of the airfoil, uniformly distribute the vorticity of airfoil over the whole flow field, improve the aerodynamic performance of the wind turbine, and therefore reduce the amplitude of the torque coefficient.
  • New Energy
    A Modularized Solar Seawater Desalination System with Multi-effect Evaporation and Heat Recovery
    XIAO Hongsheng, LIU Zhenhua, CHEN Zhenyu, XIA Ning
    2015, 35(12): 1018-1023.
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    The structure and components of a newly-designed small-sized modularized seawater desalination system powered by solar energy with multi-effect heat recovery units were introduced in detail. Through tests under different weather conditions and in different pressure regulating ways, the freshwater yield of the solar seawater desalination system was analyzed, thus obtaining the ways to improve the performance ratio and total efficiency of the system. Results show that via the free pressure setting method to regulate the steam pressure, and by controlling the maximum collecting temperature at 130 °C, the freshwater yield of unit collecting area in the modularized system with about 2.31 m2 daylight gathering area can reach 1.982 kg/(h·m2), and the all-day freshwater yield is up to 7.869 kg/m2, with a highest performance ratio up to 2.5, the total efficiency up to 1.35, and the system collecting efficiency up to 0.4, indicating outstanding performance of the solar seawater desalination system.
    • Nuclear Technology
  • Nuclear Technology
    Effects of Annular Flow on Rotor Vibration of Nuclear Power RCP Motors
    QU Dazhuang, JIN Le, ZHOU Quan, LI Mengqi, JIA Xin
    2015, 35(12): 1023-1028.
    Abstract ( )   Knowledge map   Save
    In terms of existing knowledge on dynamic phenomena of an annular flow, a simplified single disk was taken as an analytical model to theoretically study the rotor vibrations. Stability boundary conditions and whirling frequency changes of rotor vibrations were developed by using the Hurwitz criterion and a complex eigenvalue method. Principles of vibration amplitude changes and corresponding critical speeds were presented by analytically solving responses of unbalanced rotor vibrations in steady state. By means of the finite element method with complex modes, rotor vibrations of an existing canned motor pump were simulated numerically. Results from numerical calculation are corresponding with conclusions from theoretical studies, which may serve as a reference for further understanding the effect mechanism of annular flow on rotor vibration of nuclear power reactor coolant pump(RCP) motors.