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    Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Design Optimization of Fir-tree Root and Rim for Control Stage Blades Considering 3D Thermo-elastic Contact Problems
    ZHANG Ming-hui, ZHANG Di, XIE Yong-hui
    2012, 32(7): 501-507.
    Abstract ( )   Knowledge map   Save
    The research on optimization of fir-tree root and rim for turbine control stage blades was conducted in consideration of high-temperature thermal deformation. A parametric model for the fir-tree root and rim was established based on the parametric design language APDL from the finite element software Ansys, with which multivariable optimization was carried out for the structure of the root and rim using pattern search algorithm, by taking 8 critical geometrical parameters as design variables and the maximum equivalent stress of the root and rim as objective function, and hence an optimized structure obtained at the premise that the maximum equivalent stress was evidently reduced. Compared with the original structure, the maximum equivalent stress of the optimized root and rim can be reduced by 19.84% and 6.48% respectively, resulting in increased operation reliability of steam turbines.
  • Steam Turbine and Gas Turbine
    Comparison of Seal Performance Among Stepped Labyrinth, Honeycomb and Hole-pattern Damper Seal
    JIANG Lu-yi, LIU Wang-kou, ZHANG Zhao-he, CUI Qi
    2012, 32(7): 508-512.
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    A 3D numerical simulation was performed on the stepped labyrinth, honeycomb and hole-pattern damper seal using the commercial CFD software Fluent, during which the seal performance of above 3 seals was respectively obtained at different pressure ratios, rotating speeds and relative clearances, while a comparison made between calculated results and experimental data for the stepped labyrinth seal and honeycomb seal. Results show that for the stepped labyrinth seal, the flow coefficient increases with rising pressure ratio and reducing relative clearance, and drops slightly with rising rotating speed; whereas for both the honeycomb and hole-pattern damper seal, the flow coefficient increases with reducing pressure ratio and rising relative clearance, and drops slightly with rising rotating speed, indicating basically a linear variation law. Under same conditions, the steam leakage of a honeycomb seal is 10% less than that of a labyrinth seal, and 6% higher than that of a hole-pattern damper seal.
  • Steam Turbine and Gas Turbine
    Experimental Study of Shafting Load Distribution Based on Strain and Transfer Matrix Method
    ZHANG Shi-dong, YANG Jian-gang, ZHU Xian-bao, LI Yan-yong
    2012, 32(7): 513-516.
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    To calculate the shafting load distribution, a mechanical model for shaft alignment was set up based on strain and transfer matrix method, with which actual bearing load and elevation were calculated by measuring the section strain values, while the influence coefficients of bearing load measured by changing the bearing elevation. Results show that the actual measurements agree well with that of the theoretical calculation, proving the strain and transfer matrix method to be effective, which has many advantages such as easiness in implementation, effectiveness in modularity and strong ability in dealing with complex structures.
    • Boiler Technology
  • Boiler Technology
    Thermodynamic Characteristics and Economic Analysis of a BFG/Pulverized Coal Mixed Combustion Boiler
    WANG Chun-bo,WEI Jian-guo,HUANG Jiang-cheng
    2012, 32(7): 517-522.
    Abstract ( )   Knowledge map   Save
    To solve the problems occurring in a 300 MW tangential blast furnace gas (BFG)/pulverized coal blended combustion boiler, such as overheating of its superheater/reheater and high carbon content in the fly ash, etc., thermodynamic calculations and an economic analysis were carried out. Results show that after the fuel coal is blended with BFG, the in-furnace temperature drops, the exhaust gas volume rises, the absorption of radiation heat reduces, the absorption of convection heat increases, the gas temperatures at and after furnace outlet rise, the exhaust gas temperature increases and the boiler efficiency decreases; after mixing with BFG, the house power consumption rises, but the coal consumption for power generation reduces, which helps to reduce the power generating cost.
  • Boiler Technology
    Influence of OFA Nozzle Position on NOx Emission
    WANG Ding-hui, WANG Xiao-tian, GUO Yong-hong, SUN Bao-min, BAI Tao
    2012, 32(7): 523-527.
    Abstract ( )   Knowledge map   Save
    To reduce the NOx emission of a coal-fired boiler with swirl burners, a retrofit scheme was proposed by adopting the air-staged combustion mode, based on which a numerical simulation was carried out on the in-furnace combustion and pollutant formation respectively at 3 positions of OFA nozzle using CFD software platform at rated load, so as to determine the optimum position of OFA nozzle. Results show that the uplifting of OFA nozzle will reduce the O2 volumetric fraction in the main combustion zone and therefore reduce the highest temperature in the furnace by 23-29 K; the position of OFA nozzle plays a role in influencing the NOx reduction, outlet gas temperature and coal/coke conversion rate; with the lifting of OFA nozzle position, the NOx mass concentration reduces, the outlet gas temperture rises and the coal/coke conversion rate drops. Considering above effects comprehensively, the optimal position of OFA nozzle is finally determined as 7.7 m away from the burner of upper layer.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Heat Value Measurement of Coal Fuel for a Once-through Boiler
    ZENG De-liang, YAN Shu, SUN Wei-yi, LIU Ji-zhen, XIE Xie
    2012, 32(7): 528-531.
    Abstract ( )   Knowledge map   Save
    Based on the features of one-through boiler unit, a model is proposed for heat value measurement of the coal fuel, in which the dynamic performance of both the pulverizing system and the boiler proper has been considered. An identification of model parameters has been performed by using operating data of a domestic 1 000 MW ultra super-critical power unit, while the model precision verified. Results show that the model is quite accurate, insensitive to disturbance from boiler side, and therefore may be used for real-time monitoring of coal heat value.
  • Automatical Controlling and Detecting Diagnosis
    Control Study for Ash Recycling Systems Based on Compensatory Fuzzy Neural Network
    GAO Ming-ming, LIU Ji-zhen, GAO Ming-shuai, YANG Shi-ming,WU Yu-ping, ZHANG Ming-sheng
    2012, 32(7): 532-537.
    Abstract ( )   Knowledge map   Save
    To study the influence of the amount of return materials on bed temperature of related CFB boiler, a control model has been established for the return materials in ash recycling system based on compensatory fuzzy neural network (CFNN), with which a simulation study has been carried out by taking the temperature change and temperature variation rate as the input variables, and the return air flow as output variable. Comparison results between CFNN controller and coventional controller show that the adaptability of the former one to parameter change is obviously stronger than the latter one, which therefore may serve as a reference for control optimization of ash recyling systems.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Numerical Simulation of Swirl Nozzle Flow Characteristics at Pulsating Pressures
    LIU Hong-zhao, WU Wei-liang
    2012, 32(7): 538-541.
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    Numerical simulation on flow characteristics in a swirl nozzle has been carried out at pulsating pressures, while how following factors vary with the pressure pulsating frequency analyzed, such as the instantaneous flow, average flow, atomization angle and the phase difference between the pulsating pressure and the instantaneous flow, etc. Results show that the instantaneous flow and atomization angle change periodically at the same frequency as the pulsating pressure, and the phase difference between them is π; the average flow at nozzle outlet changes in an oscillatory way with the rise of pressure pulsating frequency, of which the variation law is relatively complicated.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Analysis on Optimum Vacuum of Direct Air-cooled Unit Under Variable Working Conditions
    GUO Min-chen, XIE Jing-lan, LI Peng
    2012, 32(7): 542-546.
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    To improve the thermal economy of direct air-cooled power unit, a determination method for optimum vacuum has been developed by calculating the increment of both the unit power generation and the auxiliary power consumption based on the variable condition model for cold-end system, at rising supply rate of air for condenser. According to the similarity law, the effect of face velocity on fan power consumption is determined firstly, then the influence of back pressure on unit power generation is obtained by analyzing and simplifying the mathematical model of cold end system, and finally the optimum vacuum corresponding to various face velocities is deduced at different ambient temperatures and different exhaust steam heat loads. Calculation results on a 330 MW unit show that both the optimum vacuum and corresponding air velocity increase with rising exhaust steam or ambient temperature; the optimum vacuum is greatly affected by the ambient temperature, when the temperature gets above 20 ℃.
  • Auxiliary Equipment Technology
    The Constant Parameter Output of Heat Exchangers During Dynamic Processes
    TANG Sheng, LI Ke-qun
    2012, 32(7): 547-551.
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    To keep the target output parameters of various heat exchangers constant during dynamic processes, a mathematical model has been set up from an integral standpoint, with which analytical solutions of the outlet temperature responses were calculated by using Laplace and inverse Laplace transform, while an adjustment method deduced for target output parameters of two- and multi-stream heat exchangers with step changes of one or more inlet parameters. Results show that the output parameters of heat exchanger can be accurately controlled by adjusting the inlet parameters, so as to secure the operation stability and safety of heat exchangers.
    • Environmental Science
  • Environmental Science
    Experimental Study on NOX Reduction in a Coal-fired Boiler by Reburning Biomass Syngas with Tar
    YIN Ren-hao, LUO Yong-hao, LIU Chun-yuan, ZHANG Rui-zhi, CAO Yang
    2012, 32(7): 552-557.
    Abstract ( )   Knowledge map   Save
    A test rig, consisting of a 10 kW updraft biomass gasifier and a 20 kW pulverized-coal drop tube furnace, was established to investigate the technology of NOx reduction in a coal-fired boiler by reburning biomass syngas with tar under different reburning conditions. Results show that the tar produced in gasification process will crack into hydrocarbon radicals with high heat value, which have a positive effect on NOx reduction. Higher efficiency of NOx reduction may be obtained at lower excess air coefficients and higher reburning temperatures, and in the experiment, the data may get above 80%. The application of biomass syngas reburning technology may help to handle the tough problem of tar disposal, raise conversion rate of biomass energy, and simultaneously reduce NOx emission from coal-fired boilers.
  • Environmental Science
    Process Simulation of the Multiple Cyclic CCRs System for CO2 Capture Based on Aspen Plus
    CHEN Hai-ping, WANG Zhong-ping, WU Wen-hao, TONG Jia-lin
    2012, 32(7): 558-561.
    Abstract ( )   Knowledge map   Save
    The multiple cyclic calcination/carbonation reactions (CCRs) process for CO2 capture has been simulated using commercial software Aspen Plus, with focus on the energy recovery of the CCRs system, while an analysis performed on the sensitivity of simulated results, so as to analyze the effect of the mass flow of make-up CaCO3 on the solids circulation rate, the coal consumption for carbonation process and the CO2 capture rate. Results show that after the introduction of CCRs system to a 600 MW supercritical power plant, the unit efficiency drops to 39.59%, but the plant power output rises from 600 MW to 1 041.90 MW, due to additional power generation by steam turbine with the energy recovered by CCRs system.
  • Environmental Science
    Technical Calculation and Analysis of MSW Incineration with Co-current and Counter-current Shaft Furnace
    ZHAO Wei, WANG Qi, LIU Hai-xiao, ZOU Zong-shu
    2012, 32(7): 562-568.
    Abstract ( )   Knowledge map   Save
    Mass and heat balance calculation were performed for MSW (municipal solid waste) incineration process with co-current shaft furnace, of which the result was compared with that of the counter-current shaft furnace. Results show that ash content has little influence on the critical heat value required by MSW for gasification and melting, but the air-preheat temperature effects more, i.e. the critical heat value drops greatly with rising air-preheat temperature. Under same working conditions, co-current shaft furnace allows a higher moisture limit in MSW, far more than that allowed by counter-current process; meanwhile, co-current shaft furnace requires a lower critical heat value of MSW, far below the counter-current one, and the average difference value between them is about 45 000 kJ/kg, indicating that the co-current shaft furnace is more suitable for melting MSW of low heat values.
    • Nuclear Technology
  • Nuclear Technology
    Anti-seismic Calculation of the Double-casing Centrifugal Charging Pump for 1 000 MW Nuclear Power Plants
    FU Qiang, YUAN Shou-qi, ZHU Rong-sheng, WANG Xiu-li, OU Ming-xiong
    2012, 32(7): 569-576.
    Abstract ( )   Knowledge map   Save
    An inherent modal analysis has been performed on the structure of a centrifugal charging pump with Ansys software based on a newly developed 3D model. Using static method, its anti-seismic performance at SSE seismic load has been analyzed according to SRSS algorithm by simultaneously considering the actions of the gravity, temperature and pressure load. Results show that the fundamental frequency of the charging pump body is 655.13 Hz, far more than 33 Hz, indicating that the structure is rigid; the biggest Mises equivalent stress is 103.40 MPa, appearing in the middle area of outer casing, less than the material allowable stress 140.23 MPa specified by ASME-Ⅱ; the maximum displacement response is 0.143 mm, occurring in the middle area of outer casing, far below the gap of 1mm left between various components. Calculation results prove the charging pump to be satisfactory according to relevant standards.
  • Nuclear Technology
    Thermal Design and Calculation of Pressurizer Relief Tanks
    GONG Ai-cheng, ZHANG Bo, GAO Ya-fu
    2012, 32(7): 577-580.
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    Assuming that the steam in pressurizer relief tank (PRT) is in the saturated state under thermodynamic equilibrium condition, and based on the state equation of ideal gas and the laws of conservation of mass and energy, a method for design and calculation of PRT capacity is proposed for nuclear power plants, while influence of temperature and pressure limit on the PRT capacity analyzed, including how to determine the control range of water level. The method has been verified with thermal parameters of PRT and sparger nozzle in Taishan Nuclear Power Plant Phase I. Results show that the thermal parameters obtained by the method are in good conformance with actual engineering requirements, which may therefore serve as a reference for thermal design of pressurizer relief tank for nuclear power plants.