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  • 2019 Volume 39 Issue 3
    Published: 15 March 2019
      
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  • Experimental Study on NOx Emission Characteristics of a 1 000 MW Opposed Firing Boiler
    MAO Jianbo, ZHANG Ming, XIONG Jianguo, ZHANG Xiaolong
    2019, 39(3): 169-174.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To find the NOx emission characteristics of a 1 000 MW opposed firing boiler with OPCC swirl burners and 2 rows of overfire air(OFA) nozzles, field tests were conducted to study the effects of following factors on the NOx emission behavior, such as the operation mode of burners, oxygen concentration in furnace, damper opening of OFA air, vane angle of outer secondary air, damper opening of inner secondary air, damper opening of central air, outer secondary air flow of OFA nozzle, load distribution of burners, unit load and coal category etc. Results show that the influence coefficients of burner operation mode, oxygen concentration and coal category on the NOx emission are relatively high, which lie in 13%-20.2%; followed by the damper opening of OFA air, damper opening of inner secondary air, load distribution of burners, as well as the unit load, with influence coefficients in 4%-6%. The NOx emission is slightly influenced by the vane angle of outer secondary air, outer secondary air flow of OFA nozzles and the damper opening of central air.
  • Experimental and Numerical Investigation of a 600 MW W-flame Boiler Co-firing Anthracite and Coal Slime
    ZHOU Anli, MA Lun, FANG Qingyan, LI Wei, TAN Peng, ZHANG Cheng, CHEN Gang
    2019, 39(3): 175-183.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking a 600 MW W-flame boiler as an example, thermogravimetric analysis, numerical simulation and field tests were conducted on the combustion characteristics of various anthracite-coal slime mixtures, so as to analyze the ignition, combustion and NOx emission characteristics as well as the operation efficiency of the boiler under co-firing conditions. Results show that the ignition characteristics of anthracite could be improved by blending in coal slime, but the comprehensive combustion characteristics would get worse. Under co-firing conditions, the in-furnace temperature reduces, the solid incomplete combustion loss increases, and the boiler efficiency decreases, but the mass concentration of NOx drops. When the blending ratio of coal slime is less than 10%, the power generation cost could be reduced without significant influence on the stable combustion and operation of the boiler. When the blending ratio gets above 10%, the combustion condition could be improved and the carbon content in fly ash could be reduced by increasing the ratio of air to pulverized coal and by reducing the particle size, however, the mass concentration of NOx would be increased in this case.
  • Effects of Different Start-up Modes on the Stress and Lifetime of a Superheater Outlet Header
    FAN Peipei, ZHAO Yongliang, CHONG Daotong, LIU Ming, YAN Junjie
    2019, 39(3): 184-190.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    A three-dimensional finite element model was established for the high-temperature superheater outlet header of a 600 MW supercritical power unit. Based on the three typical conditions of cold, warm, and hot start-up, the transient temperature field, thermal stress field, mechanical stress field, as well as coupled stress field of the header were obtained, and the effects of different start-up modes on the low cycle fatigue life and damage of the header were compared. Results show that the maximum coupled stress occurs on the intersecting line between the cylinder inner wall and the pipe joint. The thermal stress and mechanical stress would offset each other in different start-up modes. Moreover, the ratio of fatigue damage among the cold, warm, and hot start-up mode is 449:8:1. This study may serve as a reference for the design and operation of high-temperature superheater outlet headers.
  • Model Improvement for Boiler NOx Emission Based on DEQPSO Algorithm
    DONG Ze, MA Ning, MENG Lei
    2019, 39(3): 191-197.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Taking the boiler combustion system of a 1 000 MW ultra supercritical unit as an object of study, a NOx emission prediction model was established based on the combination of differential evolution quantum particle swarm optimization (DEQPSO) and extreme learning machine (ELM), of which the prediction ability was tested with field sample data, while the prediction results were successively compared with those of basic ELM models, and the ELM models optimized by gravitation search algorithm (GSA), particle swarm optimization (PSO) and quantum particle swarm optimization (QPSO), respectively. Results show that the DEQPSO algorithm has a strong capability in parameter optimization, and the DEQPSO-ELM model has strong generalization ability and high prediction accuracy, which may serve as a reference for NOx emission prediction of power plant boilers.
  • Stress Testing and Analysis for the Coupling of a Turbo-Generator Unit
    HUANG Shuying, LIU Yaqiong, ZHANG Jinghui, LIU Zhengqiang, FENG Kun, CHEN Changli, WANG Pei, YANG Jiangang
    2019, 39(3): 198-202.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To test the force state of a coupling (including shearing force and bending moment), a strain-based method was proposed. The specific way is to arrange a group of strain gauges on both sides of the coupling to measure the bending strain on the two sections using full bridge mode under low rotating speeds. The measured strain values are then used to solve the shearing force and bending moment with the stress analysis model set up for the coupling. The technology was applied to measure the shearing force and bending moment of the coupling in a rotor-bearing test rig, a 300 MW steam turbine unit and a 600 MW steam turbine unit, based on which, an analysis was conducted on the shaft alignment status. Results show that the method is applicable on operating site, helping to find the vibration cause of the unit.
  • Linear Active Disturbance Rejection Control of SCR Flue Gas Denitrification Systems
    LI Jian, TAN Wen, ZHANG Binwen
    2019, 39(3): 203-207.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    It is difficult to set up an accurate model for the selective catalytic reduction (SCR) flue gas denitrification system with large time delay. To solve this problem, two modified structures were developed based on the linear active disturbance rejection control (LADRC) method. One is to add a time delay to the control variable before it goes to the extended state observer, and the other is to use Smith predictor to offset the delay of output variable before it entering the observer. Taking the SCR system of a 300 MW coal-fired power unit as an object of study, numerical simulations were conducted with LADRC and PID controller. Results show that the original LADRC algorithm helps to achieve satisfactory control performance for SCR systems, while the modified LADRC method improves the control quality.
  • Online Measurement Method for Ultra-low Soot Emission Based on Imaging Light Scattering
    LI Chen, CAI Xiaoshu, ZHOU Wu, WANG Wentao
    2019, 39(3): 208-213.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To realize the online measurement of ultra-low soot emission, a new method based on imaging light scattering was developed to measure the soot concentration and particle size, which was verified by experimental tests. Results show that under low soot concentration conditions, the intensity of scattered light is in direct proportion to the soot concentration. The method proposed can be used to measure not only the ultra-low soot concentration, but also the average particle size on a real time basis.
  • Diagnosis of Ice Accretion on Wind Turbine Blades Based on the Features of Operating Parameters
    GONG Miao, LI Luping, LIU Rui, ZHANG Hao, FENG Jiang
    2019, 39(3): 214-219.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To solve the problem of ice accretion on wind turbine blades in actual engineering applications, a characteristic parameter processing model was established, based on which, six characteristic indexes indicating the icing condition of wind turbine blades were extracted. Taking above six characteristic indexes as the inputs, and the blade ice accretion condition as the output, a BP neural network model was constructed for the diagnosis of ice accretion on wind turbine blades, with the data from actual wind turbine SCADA systems as the training samples and test samples. Results show that the model proposed can help to accurately detect the ice accretion on wind turbine blades.
  • Compound Fault Diagnosis of Wind Turbine Bearings Based on COT-MCKD-STH Under Variable Speed Conditions
    WANG Xiaolong, TANG Guiji, HE Yuling
    2019, 39(3): 220-226.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To diagnose the compound faults of wind turbine bearings under variable speed conditions, a method was proposed by combining the computed order tracking (COT), maximum correlated kurtosis deconvolution (MCKD) and the self-complementary top-hat (STH) transform. Firstly, the time domain signal was even-angle resampled, and then the fruit fly optimization algorithm (FOA) was utilized to search for the optimal filter length of MCKD and the optimal structural element scale of STH transform. After deconvolution processing of the resampled signal, the separated single fault source component was morphologically demodulated by STH transform. Finally, the bearing damages were determined by analyzing the obtained order spectrum. Results show that the proposed method could effectively extract the compound fault features of the bearing under variable speed conditions, which may serve as a reference for engineering applications.
  • Energy Saving Analysis on the Addition of External Steam Cooler and No.0 HP Heater
    YANG Qiuhui, QUAN Xingjun
    2019, 39(3): 227-234.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To study the energy saving effectiveness by the addition of No.0 HP heater and external steam cooler in a 660 MW unit, an analysis was conducted using Ebsilon software under different arrangements of the No.0 HP heater and external steam cooler, different unit loads and different feed water flow rates in the external steam cooler. Results show that when only No.0 HP heater is added, the final feed water temperature would be increased by 23.2 K and 21 K respectively under 75%THA and 50%THA condition, and the heat rate of unit would be reduced by about 31.2 kJ/(kW·h) and 35.8 kJ/(kW·h) accordingly. When only external steam cooler is added, the final temperature of feed water entering the economizer could be increased by 3.2 K, and the heat rate would be reduced by 10.7 kJ/(kW·h), 10.8 kJ/(kW·h) and 13.7 kJ/(kW·h) correspondingly under 100%THA, 75%THA and 50%THA condition. When both the No.0 HP heater and external steam cooler are added simultaneously, the heat rate would be reduced by 40.6 kJ/(kW·h) and 48.2 kJ/(kW·h) respectively under 75%THA and 50%THA condition, indicating that the unit economy could be improved under low load conditions with both No.0 HP heater and external steam cooler installed.
  • Experimental Study on Denitration Process in Enhanced Reduction Zone of a Pulverized Coal-fired Boiler
    WANG Yong, ZHU Jiangtao, CHEN Can, FAN Weidong, ZHOU Qi, LIN Shanhu, LIU Yi
    2019, 39(3): 235-241.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Based on the newly proposed denitration technology (multi-staged enhanced reduction pulverized coal combustion technology), a series of experiments were conducted on a 50 kW self-sustaining down-fired test furnace in Dongfang Boiler Group Co., Ltd. by injecting the reductant (urea solution or ammonia) carried by recycled flue gas into the enhanced reduction zone to intensify the denitration effectiveness. Based on the air staging combustion mode, main factors affecting the denitration efficiency were investigated, such as the input location of the two-level burn out air, injecting location of the reductant, category of the gas carrier, mixing degree of the reductant with recycled flue gas, as well as the RNSR (Nitrogen stoichiometric ratio), etc. Results show that the denitration efficiency can reach about 20% at RNSR=2 when the urea solution is injected into the reduction zone where the first-level burn out air has not been input; while the denitration efficiency can reach about 70% at RNSR=2 when the urea solution is injected into the reduction zone between the two levels of burn out air. The removal efficiency of NOx increases gradually with the rise of RNSR when ammonia is injected into the reduction zone between the two levels of burn out air. The denitration efficiency would remain at about 70% when RNSR lies in 1.2-1.6, which may get up to 80% at RNSR=2.5.
  • Study on Transformation Characteristics of Slurry Droplets and Fine Particles During Limestone Gypsum Desulfurization Process
    ZHAO Wen, CHEN Wu
    2019, 39(3): 242-247.
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The evaporation and entrainment of desulfurization slurry are important factors leading to the change of physical properties of fine particles during limestone gypsum wet flue gas desulfurization process. To analyze the relationship between the crystal characteristics of desulfurization slurry and the emission characteristics of desulfurization droplets and fine particles in cleaned flue gas, a series of experiments were carried out using the phase Doppler particle analysis (PDA) system, electronic low-pressure impactor (ELPI+) and the laser particle size analyzer. Results show that the crystal characteristics of desulfurization slurry are related to the morphology of emitted fine particulates, which are mainly plate-like and prism-like. By optimizing the crystallization process of desulfurization slurry to increase crystal sizes and by adjusting the temperatures of desulfurization slurry and flue gas at the tower inlet, the entrainment of desulfurization slurry could be weakened to some extent, thus the emission concentration of droplets and fine particles could be reduced.
  • Numerical Simulation on Aerodynamic Performance and Noise of Iced Airfoils
    YE Xuemin, ZHANG Ran, HAN Zhangjing, LI Chunxi
    2019, 39(3): 248-256.
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    The aerodynamic and aeroacoustic features of airfoils covered by glaze ice and rime ice were numerically studied using Fluent, while the sound pressure level spectrum and power spectral density of the airfoil were simulated under different iced profiles with incompressible Large Eddy Simulation (LES) method combined with Ffowcs Williams and Hawkings (FW-H) model based on Lighthill acoustic analogy, so as to analyze the effects of attack angle and wind speed on the sound pressure level spectrum and power spectral density. Results show that the aerodynamic performance of iced airfoils is deteriorated by the feature of declined lift, and an earlier separation of air flow from the airfoil is observed to enter the stall region. The effect of glaze ice on the aerodynamic performance is the most significant, followed by rime ice. The noise coming from the airfoil covered by glaze ice and rime ice is significantly higher than that without icing, especially in the former case. The acoustic noise is augmented with the increase of attack angle, and is manifested with the low-frequency discrete and broadband features when the attack angle is smaller or greater than the stall angle. The effect of wind speed on aerodynamic noise is reflected in the total sound pressure level, which increases with rising wind speed at each monitor point.