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    Boiler Technology
  • Boiler Technology
    Treatment of Unsymmetrical Burning in Tower Boiler of a 1 000 MW Unit
    CHEN Shangbing, YANG Zhongming, WANG Hui, SHU Maolong,GAO Hong, YANG Quan
    2015, 35(11): 865-870.
    Abstract ( )   Knowledge map   Save
    To evaluate the deviation degree of unsymmetrical burning in tower boiler of a 1 000 MW unit, a full-size numerical simulation was carried out, and subsequently a comparison of the CO, NO and O2 content in flue gas and the temperature field around the water wall was carried out between simulation results and actual measurements. A core-vector regression (CVR) algorithm was used to analyze the huge data from the distributed control system (DCS), and the relationships between 77 operating parameters and the steam-separator tempeature deviations were modelled and verified, based on which fine distribution schemes of the secondary air were worked out. Results show that the deviation of outlet steam temperature has been effectively reduced after the application of above schemes, resulting in improved steam quality.
  • Boiler Technology
    Monitoring Model for Ash Fouling on Semi-radiation Heating Surface of a 600 MW Supercritical Boiler
    XU Ligang, HUANG Yaji, YUE Junfeng, CHEN Bo
    2015, 35(11): 871-877.
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    To realize monitoring of ash fouling status on heating surface of coal-fired boilers, a monitoring model was established by taking the semi-radiation heating surface of a 600 MW supercritical boiler as the research object, and by using the ash fouling rate as the monitoring indicator, based on which a method for calculation of the flue gas temperature in high-temperature region was proposed, considering the dynamic characteristics of the boiler during variable load operation, while the lumped parameter dynamic correction model was adopted, so as to study the variation tendency of ash fouling on the semi-radiation heating surface during stable and variable load operation. Results show that the model for stable load operation can satisfy the monitoring requirement of ash fouling; whereas the calculation results obtained by the model for variable load operation is still affected by the load variation, even if the influence of load variation has already been considered.
  • Boiler Technology
    Effects of Cone Angle on Gas-Solid Two-phase Flow in the Swirl Burner
    YANG Yu, MA Weichen, DONG Kang, ZHOU Hao
    2015, 35(11): 878-886.
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    Phase Doppler Anemometry (PDA) was used to measure the flow field around the exit of a low NOx swirl burner, during which both the gas/solid velocity and the solid concentration distribution were obtained. Results show that the maximum radial span of the recirculation zone would rise from 40 mm to 70 mm, and the maximum velocity of backflow would rise from 1.97 m/s to 2.45 m/s, when the cone angle of swirl burner is raised from 30° to 45°. The enlargement of recirculation zone helps to delay the mixing of secondary air with primary air, which is beneficial to the reduction of NOx emission. When the cone angle increases to 60°, the secondary air would flow along the wall, and a big low-velocity recirculation zone would occur in the area between primary and secondary air, which is unable to entrain enough high-temperature flue gas to heat the primary air, thus resulting in abnormal combustion of the burner.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Experimental Study on Heat Transfer and Flow Resistance of Long-lead Double-head Spirally Grooved Tubes
    OUYANG Xinping, GAO Ming, LIU Bingxiao
    2015, 35(11): 887-892.
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    To analyze the effects of spiral size on heat transfer performance and flow resistance characteristics of long-lead double-head spirally grooved tubes, experimental tests were conducted to three kinds of such tubes with same base diameter and different spiral sizes, and the results were compared with smooth tubes of same diameter. Results show that the inner surface heat transfer coefficients of long-lead double-head spirally grooved tubes are better than smooth tubes in both the strong turbulence zone and transition flow region, with a greater increment of surface heat transfer coefficient in the transition flow region; whereas the increase of surface heat transfer coefficient is limited at shell side in both the two areas; the spiral size affects more on heat transfer inside the tubes, but affects little on heat transfer outside the tubes. In the experiment, the tube No.1 has the best comprehensive performance.
  • Engineering Thermophysics
    Experimental Analysis on Heat Transfer Correlation of Plate-Shell Heat Exchangers
    LIU Jiarui, ZHAO Wei, HUANG Xiaodong, ZHANG Hua, YU Xiaoming
    2015, 35(11): 893-900.
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    To solve the heat transfer correlation of a plate-shell heat exchanger (PSHE), experimental study was made on the basis of relevant research results of plate heater exchanger (PHE) using equal velocity method. Keeping the flow rate of both cold and hot fluid to be constant, experimental tests were conducted to a 1/1 process PSHE, of which the results were compared and analyzed. Results show that the heat transfer correlation obtained by fitting the empirical value of PHE varies at different qualitative temperatures; the unknown parameters in heat transfer correlation of PSHE are all definite values, i.e. coefficient 0.182 5, Reynolds number index 0.75 and Prandtl number index 0.34; the heat transfer correlation of PSHE is unrelated to the flow processes at plate side, unrelated to the flow processes 1 and 2 at shell side, but is coefficient-related to the flow processes 3 and 4 at shell side, and the coefficients of processes 3 and 4 are 0.82 and 0.68 times of the process 1.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Modeling for Soft Sensing of Coal Mill Output Based on Neural Network
    HAN Liangyun, LU Jingui
    2015, 35(11): 901-905.
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    To accurately measure the ball mill output, factors influencing the mill output were studied via grey entropy correlation analysis, after which a soft sensing model was built up based on BP neural network by taking above influencing factors as auxiliary variables and using the data chosen by optimal Latin hypercube design as training samples. The model reliability was verified with several groups of samples. Results show that the model established for soft sensing of ball mill output has a small prediction error, strong generalization ability, indicating good forecasting performance of the model.
  • Auxiliary Equipment Technology
    Real-Time Stall Detection of Centrifugal Fans Based on SDP Analysis and Image Matching
    XU Xiaogang, WANG Songling, LIU Haixiao
    2015, 35(11): 906-911.
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    To timely, accurately and real-timely detect the stall of centrifugal fans, a method based on symmetrized dot pattern (SDP) and image matching was put forward. Gradual process experiments of rotating stall were conducted on a G4-73No.8D centrifugal fan to collect the gas dynamic pressure signals coming from inner wall of the fan casing, which were subsequently converted into SDP images by SDP analysis, thus the SDP image templates under normal and stall operation state were established. Pressure signals from 80 sampling points were converted into SDP images, and then matched with the image templates to detect the stall; the steps were repeated for every 16 sampling points until the fan operating from normal state to rotating stall. To verify the accuracy of this method, the tested signals were analyzed off-line by wavelet transform to detect the starting point of rotating stall. Results show that via this method, the starting point of weak rotating stall could be detected within 0.35 s, while that of strong rotating stall could be detected within 0.05 s.
    • Environmental Science
  • Environmental Science
    Experimental Study and Thermodynamic Modeling of a Novel Direct Steam Stripping System for CO2 Capture
    XIANG Qunyang, FANG Mengxiang, WANG Tao, JIANG Wenmin,Yann LE MOULLEC, LU Jiahui, LUO Zhongyang
    2015, 35(11): 912-917.
    Abstract ( )   Knowledge map   Save
    A thermodynamic model of Aspen Plus was developed for studying a novel direct steam stripping system based on detailed experimental tests, of which the simulation results were compared with relevant experimental data. Results show that the simulation results are in good agreement with relevant experimental data. The CO2 regeneration energy obtained by simulation is 2.44 MJ/kg, lower than the experimental data 3.05 MJ/kg, which could be reduced to get near to the simulation results by modifying the stripper structure and promoting the mass transfer, and could be further reduced to 2.24 MJ/kg by reducing the temperature pinch of the economizer to 5 K.
  • Environmental Science
    Influence of Flue Gas Circulation Mode on the Formation of SO3
    XIAO Haiping, HAN Gaoyan, DONG Lin
    2015, 35(11): 918-922.
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    The influence of flue gas circulation mode on the formation mechanism of SO3 was analyzed by chemical reaction kinetics. Results show that more SO3 would be produced in oxy-fuel combustion mode compared with traditional conditions, among which maximum concentration of SO3 appears in the mode of wet flue gas circulation. The formation of SO3 could be promoted by high concentrations of free radicals, such as O, OH and HOSO2 generated in combustion process due to existence of high initial O2, SO2 and H2O volume fractions. The generation rate of SO3 increases with reducing initial SO2 concentration, and with rising initial O2 and H2O concentration. The mode of oxy-fuel combustion may result in high flue gas acid dew point, and in wet flue gas circulation mode, the acid dew point is the highest. The acid dew point could be effectively reduced by flue gas desulfurization and dehydration.
  • Environmental Science
    Mechanism Study on Hg Adsorption by MnO2-modified Activated Carbons
    GAO Zhengyang, L Shaokun
    2015, 35(11): 923-928.
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    To study the reaction mechanism of Hg adsorption by MnO2-modified activated carbons (C14H6), the quantum chemistry method MP2 ab initio calculation was used to optimize the 6-311+g(d,p)/SDD basis set to obtain the geometric configuration of the reactants, intermediates, transition states and products, so as to calculate the reaction kinetics. The reaction rate constants at 298-1 500 K and 0.000 1-3 MPa were calculated via transition state theory, and their variation tendency with temperature and pressure was analyzed simultaneously. Results show that in the environment simultaneously containing Hg, C14H6 and MnO2, the reaction between MnO2 and C14H6 is faster than between Hg and C14H6, and MnO2(C14H6) is easier to react with Hg than C14H6. The reaction rate constant increases with the rise of both temperature and pressure. The adsorption effect of MnO2-modified activated carbons for Hg is better than unmodified activated carbons.
    • New Energy
  • New Energy
    Effects of Reforming Conditions on Performance of the SOFC Stack
    ZHAO Qing, L Xiaojing, WANG Weiguo, WENG Yiwu
    2015, 35(11): 929-933.
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    Taking natural gas as the fuel, an external reforming experimental platform of solid oxide fuel cell (SOFC) system was established, so as to test the performance of the SOFC stack under different reforming conditions, and to analyze the effects of following factors on the stack performance, such as the water-carbon ratio, reforming temperature, reforming mode and natural gas flow, etc. Results show that under different current densities, the power output of SOFC stack using steam reforming is higher than that using auto-thermal reforming. When the stack working temperature is constantly set at 1 023 K, the power output of SOFC stack gradually increases with the rise of steam-carbon ratio, which significantly improves with the rise of natural gas flow.
  • New Energy
    Dynamic Modelling and Simulation of a Novel Grid-connected Wind Turbine
    WU Xin, SU Rui, RUI Xiaoming, LU Congfei
    2015, 35(11): 934-937.
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    To study the dynamic characteristics of wind turbine based on differential speed regulation, a tri-axial dynamic model was built up by spring-damper-mass system, with which numerical simulation was carried out using Simulink software. Taking the step wind load as an input variable, the speed, torque and power of planet carrier shaft, ring gear shaft and sun gear shaft in the differential gear train were thus obtained, and subsequently the frequency distribution of torque signals was acquired. Results show that the wind power of novel unit can be effectively adjusted via the speed regulating motor and differential gear train without any resonance due to its natural frequency keeping off the torque component.
  • New Energy
    Numerical Study of Wind Turbine Airfoil with Large-thickness Blunt Trailing Edges
    LI Xinkai, DAI Liping, KANG Shun, LIANG Sichao
    2015, 35(11): 938-943.
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    Taking airfoils DU97-W-300 and DU00-W2-401 with experimental data for wind turbines as the object of study, the effects of turbulence model and grid distribution on aerodynamic performance of the airfoils predicted by RANS algorithm were analyzed, while a comparison of calculation results was made between DES and RANS at multiple angles of attack. Results show that in the linear section of airfoil lift curve, the calculation values of transition SST (T-SST) model agree well with the experimental data, but in the stall segment of airfoil lift curve, the calculation results of full turbulence models are superior to T-SST turbulence model, and among the full turbulence models, SA model is better than SST model. Compared with RANS algorithm, the airfoil lift drag coefficient calculated by DES method is closer to the experimental data, which is able to better simulate the detail structure of separation vortex, and therefore is suitable for simulation of the large-thickness airfoils easy to get separated.
    • Material Science
  • Material Science
    Experimental Study on Fly Ash Erosive Wear of Carbon Steel 20# in Corrosive Gas Environment
    ZHAO Xianping, ZHU Chongwu, YE Guilin, SUN Jianrong, PAN Weiguo
    2015, 35(11): 944-948.
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    To study the effects of corrosive SO2 and CO2 in flue gas on erosion resistance of metallic materials used in power plants, hot-state erosive wear experiments of carbon steel 20# were carried out at a temperature of 250-500 ℃ by adding SO2 and CO2 to the test flow, and the results were compared under different airflow environments. Results show that with the rise of temperature, the relative wear of carbon steel 20# reduces first and increases later on in the range of test temperature, and the relative wear in corrosive gas environment containing SO2 and CO2 is obviously higher than that in compressed air environment, indicating that the content of SO2 and CO2 in boiler flue gas may accelerate the erosive wear of carbon steel 20#.