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  • 2017 Volume 37 Issue 9
    Published: 15 September 2017
      
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  • Effect of Na/Ca/Fe on Slagging Behavior of Zhundong Coal During Combustion Process
    WEI Bo, TAN Houzhang, WANG Xuebin, RUAN Renhui, HU Zhongfa, WANG Yibin
    2017, 37(9): 685-690.
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    Combustion experiments were conducted for Zhundong coal in a drop tube furnace, where ash particles were collected at different flue gas temperatures by a sampling probe in un-cooled mode, so as to analyze the status of different inorganic components in the flue gas before slagging, as well as to obtain the combination mode of ash particles. Results show that at the temperature of 1000 ℃, the ash particles containing sodium silicates, sodium aluminosilicates, and calcium sulphates keep in molten state, which impact and adhere on the tube wall; with the rise of slag layer thickness, the surface temperature increases, leading to the formation of molten film on the slag layer to further capture other ash particles; Fe species are fluxing agents, which may react with Si, Al, Mg, Na and Ca system to form the low temperature eutectic; when particles rich in Fe2O3 impact the molten deposit surface, a new layer of slag would be created due to the reduced melting point of deposit surface caused by the fluxing action of Fe2O3.
  • Effects of Swirl Number on Combustion Instability and NOx Formation of a Gas Turbine
    SHI Li, FU Zhongguang, WANG Ruixin, SHEN Yazhou
    2017, 37(9): 691-698.
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    Effects of swirl number on premixed combustion instability and NOx formation characteristics in combustion chamber of a gas turbine were numerically studied using large eddy simulation technology. Results show that increasing the swirl number would expand the divergence angle of flow field, enlarge the center recirculation zone, enhance the recirculation process of hot products, raise the temperature in premixing area and broaden the high-temperature zone, which are favourable for the ignition and stable combustion of fuel flow as well as for the shortening of flame length; there is a single processing vortex core (PVC) in the flow field under the swirl number of 0.7, and another PVC would occur under higher swirl numbers; increasing the swirl number would improve the periodic shedding frequency of vortex and make the crush position of PVC move towards upstream, when both the oscillation frequency and amplitude of pressure would be improved due to the shortened flame length and concentrated heat release region; increasing the swirl number would also expand the flame width and reduce the peak value of temperature, which are favourable for the control of NOx emission.
  • Effect of Rotor Unbalance on Vibration Characteristics of a Two-span Three-support Shafting
    BIN Guangfu, LI Xuejun, CHEN Lifang, CUI Yahui
    2017, 37(9): 699-703.
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    To solve the problem of frequent unbalance vibration existing in two-span three-support shafting of steam turbine units and aircraft engines, the effects of rotor unbalance on the shafting vibration were studied. The specific way is to set up a finite element model for the two-span three-support shafting, then to apply in-phase and out-phase unbalance excitations to each rotor, and finally to perform a steady-state response analysis for the shafting. Meanwhile, a simulation test rig was also established. Results show that the vibration characteristics of the shafting caused by weighing in outside span is mainly of the single rotor type, and the vibration influences each other among rotors significantly, with vibration characteristics of the overhung rotor kind.
  • Effect of H2O on Catalytic Combustion of CO by 0.5%PdZrO2/γ-Al2O3
    LIU Xing, LÜ Xiaojing, WENG Yiwu
    2017, 37(9): 704-709.
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    Taking 0.5%PdZrO2/γ-Al2O3 as the catalyst, catalytic combustion experiments of CO were conducted in a self-developed PID control muti-function test rig, so as to study the basic features of CO catalytic combustion, and to analyze the effect of H2O addition on the CO conversion rate, and the effect of H2O concentration on the CO conversion rate and CO reaction time. Reasults show that the ignition and burnout temperature of CO over 0.5%PdZrO2/γ-Al2O3 would be increased by addition of H2O due to the improved activation energy of catalytic combustion. Both the ignition and burnout temperature of CO increase with the rise of H2O concentration. The higher the concentration of H2O is, the lower the CO coversion rate will be. The time to reach steady catalytic combustion of CO increases with rising H2O concentration. The presence of H2O reduces the activity of the catalyst, inhibiting the catalytic combustion.
  • Numerical Investigation on Heat Transfer Characteristics of R113 Falling Film Evaporation in Vertical Tube of an Annular Membrane Evaporator
    WANG Weishu, TIAN Miao, CUI Qiang, PENG Yan, SHI Xiaobao
    2017, 37(9): 710-715.
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    By establishing physical and mathematic model for R113 falling film evaporation in vertical tube of an annular membrane evaporator, two-dimensional unsteady numerical simulation was conducted on heat transfer characteristics of the gas-liquid countercurrent falling film evaporation, so as to analyze the distribution of liquid film flow, wall temperature and film surface temperature, and to compare the thickness of liquid film before and after heating. Results show that in the process of falling film evaporation, the splash of droplets starts from the lower end of liquid film, which propagates gradually toward the upper end; for R113, both the wall and film temperature rise along the flow direction during falling film evaporation, while the gas temperature falls; the temperature reduces gradually from wall to center along the radial direction, and the temperature distribution tends to be opposite at the position 1 mm away from the wall; the thickness of liquid film reduces greatly after heating, when the thickness of downstream film becomes relatively uniform.
  • Research on Flow Uniformity and Pressure Characteristics of a Wide-angle Electrostatic Precipitator
    ZHOU Hao, ZHAO Kai, ZHAO Menghao, MA Weichen, SONG Jin
    2017, 37(9): 716-725.
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    Flow uniformity and pressure characteristics of an electrostatic precipitator were studied based on the model test rig with area ratio of 9.43, up and down extending angle of 45°and 57°respectively, and with inside velocity of the air medium within 1.06-1.27 m/s. Results show that the relative deviation of flow rate can be reduced to 0.27 through experiments; uniform air flow and low pressure drop could be achieved by optimizing the design of perforated plates with an optimal perforated rate in the range of 0.5-0.7; when the perforated plate moves upstream, or when the number of perforated plates rises, the pressure drop would increase.
  • Study on Modification of Iron Ore Catalysts for Low-temperature SCR Denitrification
    LU Huixia, GUI Keting
    2017, 37(9): 726-731.
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    Siderite particles were modified by mixing with rare earth element Ce to prepare SCR catalysts, and subsequently low-temperature SCR flue gas denitrification was conducted to study the activity of the catalysts. Meanwhile, the siderite catalysts were characterized by XRF, BET, XRD and NH3-TPD analysis before and after modification. Results show that the catalytic activity of modified siderite catalysts is significantly improved, and their sulfur resistance and durability are promoted accordingly. After doping with Ce, elements Fe and Mn in original iron ore would react with Ce, which makes the specific surface be enlarged, the crystal structure be improved and the surface acidity be increased, resulting in enhanced activity of the modified catalysts.
  • Research on Properties of CuO-ZnO/γ-Al2O3 Catalysts for N2O Decomposition
    MA Shuai, LU Qiang, LIN Zhuowei, LIU Yu, LI Wenyan, DONG Changqing
    2017, 37(9): 732-737.
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    CuO-ZnO/γ-Al2O3 catalysts for direct decomposition of N2O were prepared by incipient wetness impregnation method with CuO as the active component, ZnO as the promoter, and γ-Al2O3 as the carrier. Experiments were performed to investigate the activity of above catalysts for N2O decomposition affected by the active component and promoter contents as well as by the flue gas conditions. Moreover, the catalysts were subjected to stability test and characterization. Results indicate that the catalyst with 15% CuO has the highest N2O decomposition activity, and the addition of ZnO promotes the catalytic activity remarkably. The presence of O2 and H2O in the flue gas inhibits the activity of the catalyst. The N2O decomposition efficiency of 15Cu-30Zn/γ-Al2O3 catalyst was kept over 90% in the 100 hours stability test in presence of O2 and H2O at the temperature of 650℃ and space velocity of 21000 h-1, indicating favorable deactivation resistance to O2 and H2O as well as good stability of the catalyst at high temperatures.
  • Mechanism Study of H2O and NH3 Adsorption by V2O5 with Different Valences
    GAO Zhengyang, LIANG Ranran, FAN Junhui
    2017, 37(9): 738-743.
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    To study the reaction mechanism of H2O and NH3 adsorption by V2O5 with different valences (V6O15 and V6O15+), the quantum chemistry method was used to get the structures of reactants, intermediates, transition states and relevant products, so as to analyze the potential energy, reaction energy barrier, bond length and adsorption energy of the optimized structure in the reaction process. Results show that both V6O15 and V6O15+ can absorb H2O to generate V-OH, but for the later the whole reaction is exothermic with lower reaction energy barrier, indicating that V6O15+ is more likely to react with H2O to generate Brønsted acid site. The adsorption energy of NH3 on V6O15+ is larger, and it is easier to form -NH4+, which can react with NO. Furthermore, the cationic cluster V6O15+ is more active than the neutral cluster V6O15 in SCR denitrification reactions.
  • Dynamic Response of the Array of Floating Wind Turbine Platforms
    DING Qinwei, LI Chun, YE Kehua, HAO Wenxing, YE Zhou
    2017, 37(9): 744-750.
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    To investigate the dynamic response of wind turbine platform matrix, models were established based on OC3-Hywind Spar Buoy platform for NREL 5 MW wind turbine, with which, a comparison was carried out on dynamic response characteristics of floating platforms respectively in single, 1×5 linear and 3×3 square arrangement applying radiation and diffraction theory. Results show that the surge, heave and pitch response of Spar platform all appear in the range of low frequency waves; the 1×5 linearly arranged platforms have lower surge response than single platform, because the sharing mooring reduces the surge response, which does not have obvious effect on the heave and pitch response; in terms of 3×3 squarely arranged platforms, the platforms located on sides have higher swaying but smaller heave response than single platform, while the platforms in middle area have higher surging and negligible swaying response; in terms of 3×3 squarely arranged platforms, the heave and pitch response of platforms in middle area and at vertices are lower than single platform, and the response of rest platforms are not significantly suppressed.
  • Thermal Performance Study of a High-level Water Collecting Cooling Tower for 1 000 MW Units
    JIA Mingxiao, HU Sanji, HAN Li, MU Lin
    2017, 37(9): 751-756.
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    To obtain the thermal performance of high-level water collecting cooling towers, experimental tests were conducted on such a cooling tower with drenching area of 12075 m2 used in a 1000 MW power unit, during which, calculation equations were derived for the thermal performance of the high-level water collecting cooling tower, while internal air temperature distribution was measured for the tower. In addition, a comparison was carried out on the difference of outlet water temperature between the mentioned high-level water collecting cooling tower and a conventional cooling tower with same process parameters. Results show that for the high-level water collecting cooling tower, the internal air temperature distribution in the case of three parallel pumps is more even than that of two parallel pumps. The sectional wind speed at packing area of the high-level water collecting cooling tower is larger than that of conventional cooling tower, and the outlet water temperature of the former is 0.8 K lower in summer.
  • Performance Analysis of a Power Generation System Using Solar Energy to Pre-dry the Low-rank Coal
    XU Cheng, BAI Pu, YANG Zuoxun, WANG Chunlan, XU Gang, YANG Yongping
    2017, 37(9): 757-763.
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    As northwest China is rich in solar energy and low-rank coal resources, a low-rank coal fired power generation system was proposed using solar energy integrated low-rank coal pre-drying technology. Taking a typical 600 MW supercritical unit as an object of study, heat balance models were established for the solar collection unit and the low-rank coal pre-drying unit, so as to analyze the changes of the coal mass flow and heat value with and without coal pre-drying, evaluate the comprehensive thermal performance of the proposed system from aspects of coal consumption and solar-to-electric efficiency, and finally to study the effects of total equipment investment and on-grid power tariff on the economic performance of the system with static investment payback period as the evaluation criteria. Results show that the coal consumption rate of the coal-fired power plant could be reduced remarkably by using low-grade solar energy to pre-dry the low-rank coal. As the moisture of low-rank coal reduces from 25.0% to 10.0%, the coal consumption rate would be lowered by 8.9 g/(kW·h), when the solar-to-electric efficiency could reach 25.3% with only 4.3 years of static investment payback period, indicating remakable economic benefit of the system.
  • Unequal Pressure Ratio Scaling Analysis of Station Blackout Accident in Passive Safety Nuclear Power Plant
    SHI Yan, YE Zishen, YANG Fuming, LI Yuquan, HAO Botao
    2017, 37(9): 764-772.
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    H2TS method was applied in the scaling analysis of station blackout (SBO) accident in passive safety nuclear power plant. The important phenomena were identified and chosen to establish the similarity criterions. Based on the parameter relationships given by similarity criterions, simulation theory and experimental method were proposed for the SBO in passive safety PWR at different pressure ratios, and subsequently both the distortion evaluation and numerical simulation were conducted. Results show that temperature is a kernel parameter in SBO accident analysis; the method with lower pressure and same temperature can well simulate the important phenomenon of SBO without distortion. Due to the difference of coolant physical properties, the method with lower pressure and lower temperature presents a little distortion, which gradually decreases in accident scenario. The transition between lower pressure simulation and same pressure simulation spontaneously happens and all key parameters become the same to that of prototype nuclear power plant after the ADS pressure relief valves are opened.