Archive

  • 2018 Volume 38 Issue 4
    Published: 15 April 2018
      
  • Select all
    |
  • Thermal Stress Analysis of Water Wall in a 600 MW Supercritical CFB Boiler
    FAN Xuchen, CHEN Ye, ZHENG Xiong, WANG Quanhai, LI Jianbo, LU Xiaofeng
    2018, 38(4): 253-257.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To investigate the deformation of water wall in a supercritical circulating fluidized bed (CFB) boiler, based on the experimental data of water wall temperature distribution in a 600 MW supercritical CFB boiler, numerical simulation was carried out on the thermal stress of water wall with an area of 4.6 m×2 m at the height of 30 m above the air distributor. Results show that at 80% load, the temperature of water wall in the calculated area changes greatly along the height direction, and the distribution of thermal stress is extremely uneven. The water wall tube in the calculated area expands to the bottom of the boiler. Due to the deviation of expansion, the maximum protuberant deformation of the water wall to the center of the boiler is about 1.14 mm. For the whole water wall, the deformation may be superimposed, which can aggravate the abrasion of water wall and even cause the break of water wall tubes.
  • Application of an Improved LSSVM in Combustion Modeling and Optimization of Utility Boilers
    LI Yingbao, WANG Dongfeng
    2018, 38(4): 258-264.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The traditional least squares support vector machine (LSSVM) model was improved by robust cross-validation (RCV) method, while the combustion system of a 350 MW domestic boiler was modeled to predict the change of outlet flue gas parameters of the boiler. Results show that the robust cross-validation least squares support vector machine (RCV-LSSVM) modeling method improves the predicting precision and enhances the robustness of the model, which can effectively avoid the influence of single element error upon the model. By optimizing the combination of input parameters in the boiler combustion system, the overall economic efficiency of boiler can be improved, while the generation of nitrogen oxides (NOx) can be reduced.
  • Experimental Study on Compound Fault Characteristics of Rotor Crack and Rub-Impact Based on Full Spectrum Analysis
    HU Aijun, LIN Jianfeng, MA Pu
    2018, 38(4): 265-271.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The rub-impact fault, crack fault and crack rub-impact compound fault were respectively simulated on a rotor test setup, and subsequently the full spectrum method was used to analyze the fault characteristics. Results show that compared with traditional Fourier spectrum analysis, the full spectrum method can accurately identify above three kinds of faults and can characterize the coupling characteristics of the compound fault using the -2X, -3X and -4X double frequency components. The experimental results may serve as a reference for the diagnosis of rotor compound faults.
  • Online Measurement of Size Distribution of Pulverized Coal with Light Fluctuation Method
    QIN Shouxuan, CAI Xiaoshu
    2018, 38(4): 272-277.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on random theory and statistical properties of transmission light, a light fluctuation method was proposed to measure the size distribution of pulverized coal in power plant, which was verified with a self-developed experimental setup. Results show that via the method, the parameters of size distribution could be effectively obtained. By combining with wavelet reconstruction technology, the method can be used to process actual data of a power plant, during which the influence caused by concentration fluctuation and oversample could be avoided, thus obtaining accurate information of size distribution and concentration of the pulverized coal.
  • Prediction Model for Boiler NOx Emission Based on Adaptive Quantum Grey Wolf Optimization
    NIU Peifeng, SHI Chunjian, LIU Nan, MA Yunpeng, WU Zhiliang, LI Jinbai
    2018, 38(4): 278-285.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To accurately set up a prediction model for NOx emission from circulating fluidized bed boilers, an adaptive quantum grey wolf optimization (AQGWO) algorithm was proposed based on Bloch sphere coordinates to optimize the fast learning network (FLN), of which the optimization accuracy and convergence rate were verified by comparing the AQGWO with differential evolution algorithm and particle swarm optimization. Using the experimental data of a 300 MW circulating fluidized bed boiler obtained under different working conditions, the prediction results of AQGWO-FLN model were contrasted with those of basic FLN model and the FLN models optimized by other algorithms. Results show that the AQGWO-FLN model has good generalization ability and high prediction accuracy, which may be used to predict the NOx emission from coal-fired boilers effectively and accurately.
  • Experimental Study on Wear Resistance of SCR Denitration Catalyst to Flue Gas Fly Ash
    CHEN Hongwei, ZHAO Baoning, ZHANG Qian, XU Wenliang, DENG Huaiming, WANG Guangtao
    2018, 38(4): 286-290.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Experimental studies were conducted on wear resistance of SCR denitration catalyst to flue gas fly ash in a self-developed cold-state test facility. Results show that the catalyst wear mainly happens on the end faces, which is primarily affected by the flue gas velocity, and the wear rate varies in the velocity index of 4, while the velocity index reduces with rising size of fly ash particles. The catalyst wear is secondarily influenced by both the size and concentration of fly ash particles, and the index of particle size is about 1, which reduces with rising flue gas velocity; the wear rate of catalyst is directly proportional to the concentration of fly ash. In actual operation, the flow field should be secured as far as possible to avoid local high speed, so as to reduce the attrition of catalyst, thus achieving economic and safety operation of the denitration system.
  • Spray Evaporation Characteristics of Desulfurization Waste Water with Zero Discharge in Coal-fired Power Plant
    WANG Zulin, ZHANG Yi, SU Guoping, WEI Shuzhou
    2018, 38(4): 291-297.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To achieve zero discharge of desulfurization waste water, spray evaporation experiments of desulfurization waste water were conducted after evaporation crystallization by mechanical vapor recompression (MVR) with the injection points located in the flue duct before SCR, so as to study the evaporation characteristics of desulfurization waste water in the flue duct, and to analyze the effects of concentrated waste water injection on the outlet fly ash concentration, flue gas components, size distribution of ash particles, SO3 concentration, and specific resistance and chemical composition of fly ash, etc., while the influence of concentrated desulfurization waste water added with alkali liquor on the main components of flue gas and the specific resistance of fly ash was researched. Results show that when the concentrated desulfurization waste water is sprayed into the flue duct before SCR, there would be no significant change of dust concentration, but the HCl and HF concentration in the flue gas would increase. The content of corrosive gas in the flue gas decreases when the desulfurization waste water with alkali liquor is sprayed into the flue duct. SO3 concentration at the outlet of SCR reduces when the concentrated desulfurization waste water is injected. The specific resistance of fly ash at the same temperature drops when the desulfurization waste water with alkali liquor is sprayed, compared with the condition without alkali liquor. This is beneficial to the improvement of dust collection efficiency.
  • Effect of Evaporation Bypass on Water and Chlorine Balance in Desulfurization System of a Coal-fired Power Plant
    MA Shuangchen, WU Kai, WAN Zhongcheng, CHAI Jin, ZHANG Jingrui, LIU Qibin, WEN Jiaqi
    2018, 38(4): 298-307.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To compare the difference in water balance and chloride balance of a desulfurization system with and without evaporation bypass, material balance models were respectively put forward. Results show that under the condition with evaporation bypass, in the case of 2% volatile mass fraction of chloride and complete evaporation of desulfurization wastewater, the volumetric flowrate of desulfurization wastewater decreases by 4.30%, the make-up water decreases by 14.60%, and the carry-over moisture at absorption tower outlet reduces by 12.83 t/h. When the volatile mass fraction of chloride rises or when the chloride concentration in desulfurization wastewater reduces, the flowrate of desulfurization wastewater, make-up water and carry-over moisture would increase, while the temperature of flue gas at absorption tower outlet would rise.
  • Analytical Method for Particle Collection in a High-temperature Wire-cylinder Electrostatic Precipitator
    WANG Xihui, CHEN Houtao, YANG Guang, XIAO Gang
    2018, 38(4): 308-315.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    By analyzing the force condition of charged particles in gas flow field coupled with electric field, the particle trajectory in effective collection space was calculated, so as to derive the formula for collection efficiency of particles. Results show that the calculation results agree well with experimental data at the temperature of 350-700℃ with port voltage greater than 15 900 V, when the maximum relative error is less than 9%. The boundary effect of cathode line should be considered in the case of mean gas velocity being larger than 0.2 m/s. For particles with same diameter, the migration velocities differ a lot when their initial positions are different in the electric field. The required height of precipitator reduces with the rise of port voltage; taking the particle of size 10 μm as an example, to reach the collection efficiency of 100% at the temperature of 620℃, the required height is about 0.86 m for a port voltage of 15 925 V, which is about 0.42 m when the port voltage gets up to 19 200 V. A particle is more likely to be captured when entering the electric field, if its initial position is in the vicinity of cathode line or anodic tube.
  • Numerical Study on Configuration and Aerodynamic Characteristics of Triangular Flaps for Wind Turbine Blades
    CHEN Zhigang, LI Kunlin, YANG Bo, LI Maodong, LU Xuxiang
    2018, 38(4): 316-320.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the effect of triangular flaps on the aerodynamic characteristics of wind turbine blade airfoils, the triangular flaps were added to the trailing edge of the NACA4412 airfoil, for which, a two-dimensional flap calculation model was established. Based on CFD numerical simulation, the aerodynamic parameters of the triangular flaps with different widths and lengths were analyzed with the angles of attack in the range of 0°-18°, so as to obtain the lift coefficient, drag coefficient, lift to drag ratio and airfoil wall pressure distribution curve at different angles of attack. Results show that the lift to drag ratio of aerofoil decreases and the stall angle advances with growing length of flap, while the lift to drag ratio of aerofoil increases and the stall angle delays when the width of flap increases, therefore, the aerodynamic characteristics of aerofoil can be improved by reducing the length or increasing the width of flap. Compared with conventional flaps, the manufacturing materials and space are reduced by taking 5% region of aerofoil tail as the space for flap installation.
  • Modeling of a Smart Blade Wind Turbine and Its Multi-target Control with Trailing Edge Flaps
    ZHANG Wenguang, BAI Xuejian
    2018, 38(4): 321-328.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To research the effects of trailing edge flap (TEF) on active load suppression and power control of a wind turbine, the National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine was taken as the research object, with two separate TEFs added to each blade. A smart blade wind turbine model with TEFs was developed on Matlab/Simulink by building the aerodynamic model, drive chain model and generator model, which was then verified by comparison with FAST aeroelastic simulation platform under different wind conditions, and subsequently a multi-target control was designed with trailing edge flaps. Simulation results show that, compared with FAST aeroelastic simulation platform, the smart blade wind turbine model has a higher accuracy, with parameters deviation less than 10%; under the multi-target control with trailing edge flaps, the power spectral density (PSD) of the blade flapwise root moment can be reduced by 89.73% at 1P frequency, while the standard deviation of generator power can be reduced by 75.07%.
  • Performance Analysis of an ORC-RO Desalination System with Different Energy Recovery Methods
    LIU Xiulong, CAO Shuang, XU Jinliang, XIE Xuewang, ZHAO Xiaoli
    2018, 38(4): 329-336.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A model of reverse osmosis (RO) desalination system driven by organic Rankine cycle (ORC) was designed. Taking R600a/R601a as the organic working fluid, with the seawater passing through a condenser to improve the fresh water production, a comparison was carried out on the performance of an ORC-RO desalination system with different energy recovery methods. Results show that the best mixing ratio of R600a/R601a for the BASIC system, PWT energy recovery system and PES energy recovery system are respectively 0.7/0.3, 0.8/0.2 and 0.9/0.1. At the average temperature 12℃ of Bohai sea, the fresh water production of BASIC system is 5.04 kg/s, which can be increased by 38.69% and 130.36% when PWT system and PES system are used respectively. For the same power consumption, the fresh water production of above three systems is respectively 80.96%, 39.44% and 19.57% higher than the RO desalination system driven by electricity. With the increase of inlet water temperature of the condenser, the advantages of PES system in water production reduce, and zeotropic mixture is proved to be superior to pure fluid. Clearly, it is necessary to consider the influence of seawater temperature in the design of similar composite systems.
  • Performance Analysis of a Steam-driven Injector for Emergency Feedwater System of Nuclear Power Plant
    WU Xinzhuang
    2018, 38(4): 337-340.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A simplified analysis method was proposed for the demand of emergency feedwater by nuclear power plant using steam-driven injector. According to the parameters of AP1000 nulcear power plant, the cooling water demand in primary loop was analyzed during shutdown period, so as to obtain the requirement on performance of the steam-driven injector in the process of hot and cold standby. Results indicate that, the steam-driven injector is required to operate at various cases during shutdown period, so different configurations can be adopted in the design of steam-driven injectors, thus meeting the performance requirement of steam-driven injector through adjustment on relevant steam and water parameters.