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    Boiler Technology
  • Boiler Technology
    Numerical Simulation on Combustion Characteristics of a 300 MW Bituminous Coal/BFG Co-firing Boiler Mixed with Lignite and the Economic Analysis
    WANG Chunbo, LI Wei
    2013, 33(6): 413-418.
    Abstract ( )   Knowledge map   Save
    Numerical simulation was carried out on a 300 MW bituminous coal/BFG co-firing boiler mixed with lignite, while economic analysis performed to the boiler unit, during which the influence of blending ratio on the in-furnace temperature and CO concentration distribution was analyzed under cases that the bituminous coal was completely/partially replaced with lignite and different ratios of blast furnace gas (BFG) was blended. Results show that when the bituminous coal was completely replaced with lignite, the in-furnace temperature reduces obviously while the outlet temperature rises significantly, which may affect safety operation of the boiler; whereas when the bituminous coal was partially replaced with lignite, with the rise of blending ratio, the in-furnace temperature reduces gradually while the outlet temperature rises, but the CO concentration basically keeps the same; for a fixed blending ratio of lignite, with the rise of blending ratio of BFG, the in-furnace temperature reduces obviously, the outlet temperature rises, and the highest CO concentration reduces gradually. The power generation cost with pure bituminous coal is 117 090 RMB/h, which drops to 80 107 RMB/h when 40% lignite and 20% BFG are blended, indicating a reduction of power generation cost by 31.59%.
  • Boiler Technology
    Numerical Simulation on Oxygen-enriched Combustion of T-shaped Pulverized Coal-fired Boiler
    TIAN Jiao, WANG Yong, QIAO Xiaolei, CAI Xinchun, JIN Yan
    2013, 33(6): 419-423.
    Abstract ( )   Knowledge map   Save
    To study the oxygen-enriched combustion characteristics of pulverized coal-fired boiler, numerical simulation was carried to the combustion process of a T-shaped boiler using Fluent software, during which the in-furnace temperature field, velocity field and mass concentration distribution of various gas components were obtained under conditions of different oxygen concentrations in primary air. Results show that the overall in-furnace temperature under oxygen-enriched condition is higher than that under air combustion condition; when the oxygen volume fraction is increased from 21% to 33%, the mean furnace temperature rises from 1 413.2 K to 1 447.1 K; when the oxygen volume fraction is increased to 27%, the mean furnace temperature changes obviously, reaching 1 435.6 K; when the oxygen volume fraction is increased to a degree more than 29%, the mean furnace temperature basically remains unchanged; the optimal oxygen volume fraction is 27%-29% under oxygen-enriched combustion mode with variable primary air volumes.
  • Boiler Technology
    Numerical Simulation on Flow and Temperature Field of Multi-phase Flow in Convective Waste Heat Boiler of Pressurized Coal Gasifiers
    ZHANG Chuanmei, JIN Jing, ZHANG Hao, JIANG Jie, GAO Wenjing, DONG Zhen
    2013, 33(6): 424-429.
    Abstract ( )   Knowledge map   Save
    Simulation and analysis were carried out on flow and temperature distribution of syngas in three sections and circles of a convective waste heat boiler for pressurized dry pulverized coal gasifier, in which the gas flow field was calculated by combining species transport equation with Realizable k-ε turbulence model, while the particle flow field by DPM model. The two-way coupling model was applied to analyze the interaction between gas and particles. Simultaneously, the temperature field was calculated by weighted-sum-of-gray-gases model and DO model, and the basic parameters of high-pressure gases were decided by comparison state method, pressure and species amendment method, and Hottel’s method. Result show that the velocity of syngas reduces gradually from top to bottom heating surface and from outer to inner annular space, and the velocity peak deviates along the height direction due to the action of baffle plates. High concentration of particles appears at the syngas inlet, the bottom of each section and in the area blocked by upper plate, where soot blowers are required. The heat-transfer coefficients of upper, middle and lower heating surface as well as the outer water wall are respectively 274 W/(m2·K), 243 W/(m2·K), 198 W/(m2·K) and 223 W/(m2·K).
  • Boiler Technology
    Cause Analysis on Burnout of OPCC Swirl Burners and the Remedy
    LI Debo, SHEN Yueliang, DENG Jianhua, DI Wanfeng, XU Qisheng
    2013, 33(6): 430-436.
    Abstract ( )   Knowledge map   Save
    Aiming at actual situations that great economic loss was brought to a 660 MW supercritical boiler due to large-area burnout of its OPCC swirl burners, detailed analysis was carried out on the burnout causes, including the selection of swirl burner materials, defects in structural design, problems in field operation, and so on. Through thermal numerical simulation to the whole furnace, corresponding burnout reasons were found, based on which improvement measures were proposed for the swirl burners. Results show that the main burnout reason is the too high swirl intensity of the inner secondary air; the primary air duct made of carbon steel is inadequate for heat-resistant requirement, which should be replaced with high-temperature abrasion-resistant alloy steel by integral casting; previous ceramic paste process is easy to cause the falling off of ceramics, which should be modified; serious carbonization is found on the central air duct made of heat-resistant steel, of which the manufacturing technology should be improved.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Influence of Three-lobe Journal Bearing’s Oil Film Pressure Property on the Rotor Stability
    ZHANG Aiping, LIN Shengqiang, XIE Meina
    2013, 33(6): 437-442.
    Abstract ( )   Knowledge map   Save
    Using CFD software, and considering the SST turbulence calculation model and N-S equation for rotation property of viscous fluid, the oil film pressure distribution of three-lobe journal bearing was studied so as to analyze its influence on the stability of steam turbine rotors, and to carry out a comparative analysis of the oil film pressure distribution among the three-lobe journal bearing, the cylindrical bearing and the elliptical bearing. Results show that, under the same conditions of oil film thickness and inlet pressure, the three-lobe journal bearing has the highest stability among the three kinds of bearing, which is hard to cause oil film oscillation and instability; under the same conditions of oil film thickness and eccentricity, the bearing capacity of elliptical bearing is better than that of the three-lobe journal bearing, however, the latter one is more helpful to stable operation of turbine rotors and power units.
    • utomatical Controlling and Detecting Diagnosis
  • utomatical Controlling and Detecting Diagnosis
    BP Neural Network Prediction on Heat-transfer Performance of Direct Air-cooled Condensers
    GAO Jianqiang, WANG Yan
    2013, 33(6): 443-447.
    Abstract ( )   Knowledge map   Save
    A novel prediction model for heat-transfer performance of direct air-cooled condenser (DACC) was established based on BP neural network by analyzing the calculation process of DACC heat-transfer coefficient, taking the unit load, exhaust pressure, condensate temperature, exhaust temperature, and inlet/outlet temperature of DACC as input parameters, and the heat-transfer coefficient and face velocity as output parameters, in combination of the theoretical model with actual operation data. Results show that the BP neural network model has a high precision in parameter prediction, which therefore can be used for on-line monitoring of DACC heat-transfer performance.
  • utomatical Controlling and Detecting Diagnosis
    In Situ Measurements of CO in Combustion Gases Based on TDLAS and Analysis on Relevant Influencing Factors
    ZHANG Haidan, WANG Fei, XING Dawei, XU Ting,JIANG Zhishen, YAN Jianhua, CEN Kefa
    2013, 33(6): 448-454.
    Abstract ( )   Knowledge map   Save
    Spectral parameters of CO absorption line were measured under different combustion conditions using a 2.3 μm diode laser by scanned-wavelength direct absorption (DA) strategy based on tunable diode laser absorption spectroscopy (TDLAS), so as to study the influence of pressure and temperature on the width and intensity of absorption line. Results show that the line width increases gradually with the rise of pressure, which requires the laser to have a wide scanning range; spectral line R(30) is highly independent at high pressures, without superimposition with other interference lines, therefore is suitable for measurement of CO absorption line; the influence of particles on measurement precision can be reduced by background elimination method; the intensity of lines in selected band is strong enough at high temperatures (>1 000 K), so that direct absorption signals can be obtained, and the complexity of modulation technique can be avoided, which therefore may serve as a reference for study of relevant influencing factors.
  • utomatical Controlling and Detecting Diagnosis
    Diagnosis of Valve Leakage Fault Patterns Based on Acoustic Emission Detection
    YANG Jing, LI Luping, RAO Hongde, ZHU Yijun, LIU Gongchun
    2013, 33(6): 455-460.
    Abstract ( )   Knowledge map   Save
    To realize visual and accurate diagnosis of valve leakage faults, the flow field around leakage holes and the energy calculation on fluid in the flow field were analyzed under typical leakage patterns, by integrating theory with practice and classifying common leakage patterns in engineering practice. Simulation experiments were carried out to study the valve leakage of different patterns, during which corresponding acoustic emission signals were analyzed using wavelet packet technology, and subsequently the variation laws of leakage acoustic emission energy with leakage pattern were obtained. Results show that the energy ratio in each sub-band of acoustic emission signals differs regularly for valve faults of different patterns. The diagnosis criteria may serve as a reference for visualized detection of valve faults.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Effect of Gas Film Thickness Distribution on Condensation Heat-transfer Characteristics of Vapor-Gas Mixtures
    LI Huijun, PENG Wenping
    2013, 33(6): 461-465.
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    A thickness model of gas film formed during condensation heat-transfer process of vapor-gas flow on a horizontal tube was set up based on the double boundary layer theory and in consideration of the induced velocity inside gas film, shear force at gas-liquid interface and the pressure gradient, with which the gas film separation conditions were discussed. Results show that along the downward direction of tube wall, the gas film thickness increases gradually; when the gas film separates, its thickness will increase sharply near the separation point, and reduce with rising velocity; whereas when the gas film doesn’t separate, its thickness will reduce rapidly near the bottom of tube wall, and increase with rising velocity; the gas film thickness will increase with rising wall temperature and mass concentration of non-condensable gas; the gas film thickness and separation have certain effects on the heat-transfer characteristics of vapor-gas mixture.
    • Environmental Science
  • Environmental Science
    Study on Characteristic of Flow Field in a New Gas-outside Liquid-inside Atomizer
    LIU Dingping, CHEN Boqiang
    2013, 33(6): 466-471.
    Abstract ( )   Knowledge map   Save
    Numerical simulation and analysis were carried out on two-phase flow field in a new type gas-outside liquid-inside atomizer by computational fluid dynamics (CFD) technique, during which the influence of inlet gas/liquid pressure on the two-phase flow was studied, while the simulation results verified with experimental data. Results show that the outlet turbulence intensity of nozzle increases with the rise of inlet gas/liquid pressure in the range of 0.1—0.5MPa. Raising the inlet gas and inlet liquid pressure is respectively favorable to the reduction and uniformity of particle sizes.
    • New Energy
  • New Energy
    Start-up Characteristics of Naphthalene Thermosyphon in Parabolic Trough Solar Collectors
    LIU Yun, ZHANG Hong, ZHAN Dongdong, LI Sihai
    2013, 33(6): 472-478.
    Abstract ( )   Knowledge map   Save
    Based on theoretical analysis of start-up characteristics of the naphthalene thermosyphon in a parabolic trough solar collector, experimental studies were carried out on the start-up characteristics under different heating conditions, inclination angles, and fluid filling rates, while a comparison made to the start-up characteristics between experimental measurements and calculated results at 4 ℃ inclination angle under semi-circle heating conditions. Results show that the naphthalene thermosyphon can be started normally and run stably at a relatively small inclination angle in a semi-circle heating way; the heating way has little impact on the start-up characteristics of naphthalene thermosyphon; the filling rate has certain effects on the start-up time of condenser section, which reduces with lowering filling rate; the tested transition temperature of condenser section is slightly lower than the theatrically calculated one and the start-up process basically agrees with that of the theoretical analysis.
  • New Energy
    Experimental Study on Combustion Characteristics ofDistilled Spirit Lees in Fluidized Bed
    BIE Rushan, HUANG Bing, SONG Xingfei, JI Xiaoyu, ZHU Shaofei
    2013, 33(6): 479-483.
    Abstract ( )   Knowledge map   Save
    The ash composition, ash fusion point, and ignition temperature of distilled spirit lees were measured using X ray fluorescence spectrophotometer, ash fusion point determination meter, and thermo-gravimetric analyzer, while a combustion test carried out on a small-size fluidized bed test setup so as to study the ignition, sintering and NOx emission characteristics of distilled spirit lees with different moisture contents. Results show that, the content of K2O and Na2O in the ash is very low, which in total is only 4.936%; the softening temperature of the ash is relatively high, being more than 1 290 ℃; dried lees has relatively high content of volatiles and can ignite at 250 ℃; when the mean particle size of quartz sand is 300 μm and the fluidizing velocity within the bed is greater than 0.36 m/s, the fluidizing condition is good; at 900 ℃, distilled spirit lees burns in quartz sand fluidized bed without sintering phenomenon; at different combustion temperatures, the mass concentration of NOx emission is high, which increases with the rise of combustion temperature; distilled spirit lees can burn in quartz sand fluidized bed with good burnout effect.
  • New Energy
    Research on Prediction Model for Fusion Temperature of Biomass Ash
    RUAN Ruibin, LONG Bing, LIU Zhiqiang, XU Aixiang
    2013, 33(6): 484-489.
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    The influence of ash composition on its fusibility was analyzed using actual measurements from data samples, based on which a prediction model was established for the fusion temperature of ash by regression analysis method, and subsequently the significance and accuracy of relevant regression equations were verified. Results show that SiO2, CaO, K2O, SO3 and P2O5 have both positive and negative effects on the biomass ash fusibility, whereas MgO and Na2O assist the melting of biomass ash. The model is proved to be applicable to the prediction of biomass ash fusion temperature, and therefore may serve as a reference for actual engineering projects.
  • New Energy
    Influence of Geometric Parameters on Transition Characteristics of Wind Turbine Airfoils
    GAO Wei, LI Chun, GAO Yuewen, YE Zhou
    2013, 33(6): 490-486.
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    The transition point and aerodynamic performance of three wind turbine airfoils with different relative thicknesses and relative cambers were studied by coupling the potential flow equation and boundary layer equation, so as to analyze the influence of attack angle on the transition point, and the influence of boundary layer transition and reattachment on the lift and drag coefficient. Results show that the transition point moves forward with rising attack angle; with the increase of relative thickness and camber, the transition point continuously moves forward at different locations and speeds. The reattachment promotes the increase of lift coefficient.