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  • 2014 Volume 34 Issue 8
    Published: 15 August 2014
      
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  • Calculation on Infurnace Heat Transfer of Large (Ultra) Supercritical Coalfired Boilers
    ZHANG Dalong,ZHANG Hai,L Junfu,ZHANG Man,HU Rende,CAI Shilin,CHEN Chunyuan
    2014, 34(8): 589.
    Abstract ( )   Knowledge map   Save
    Considering the features of heating surface arrangement, the furnace of large (ultra) supercritical coalfired boilers was divided into a free volume region and a platen heating surface region, to which some key parameters previously calculated according to the former Soviet Union "Standard 1973" were corrected, such as the effective radiation thickness, radiative absorption coefficient and the flame center height coefficient, etc. On above basis, a onedimensional zonal thermal calculation method was proposed, which was used for infurnace heat transfer calculation of four 600 MW supercritical coalfired boilers and two 1 000 MW ultrasupercritical coalfired boilers. Results show that the error of outlet flue gas temperature between design value and calculated result obtained by the proposed method is obviously less than that by the former Soviet Union "Standard 1973", indicating that the method can meet the accuracy requirement of actual engineering projects.
  • Calculation on Convection Heat Transfer and Water Wall Temperature in Furnace of Large Capacity Boilers
    TENG Ye,ZHANG Zhongxiao,LIU Xudan,ZHOU Tuo,ZHU Ming
    2014, 34(8): 594.
    Abstract ( )   Knowledge map   Save
    Taking a 1 000 MW ultrasupercritical tower boiler as an object of study, twodimensional area calculation models were established by regional method, through which the infurnace radiation and convection heat transfer were simplified. Using above models, the proportion of convection heat transfer to total infurnace heat transfer and to each area heat transfer along furnace height direction, as well as the distribution of water wall temperature along furnace width direction, were studied at different boiler loads, of which the results were compared with actual measurements. Results show that the maximum deviation of water wall temperature between calculated data and actual measurement is 5.26%, both distributing in the shape of high in the middle and low at two ends. Taking convection heat transfer into account, the calculated wall temperature is increased by a maximum of 16.7 K, and the calculation accuracy is improved by 3.30%. The maximum calculated wall temperature is 523.5 ℃, lower than the allowable temperature of the material, having a safety margin of 4.8%.
  • Combustion Optimizationoriented Spectral Measurement and Field Reconstruction of Furnace Parameters for Power Station Boilers
    WANG Dongfeng,LIU Qian
    2014, 34(8): 599.
    Abstract ( )   Knowledge map   Save
    An analysis was made to the effects of furnace parameters on the efficiency, pollutant emission and service life of a boiler, so as to study the mutual relationship between these parameters and the boiler combustion optimization. A new technology for measurement of furnace parameters based on laser absorption spectrum was described from the aspect of measuring principle and system structure. Taking a 680 MW coalfired boiler as an example, field measurement and reconstruction of furnace parameters were carried out to the boiler based on laser spectrum. Results show that via this method, measurement and field reconstruction can be completed to multiple furnace parameters, which may serve as visible and effective guidance to optimization of boiler combustion. By adjusting the boiler combustion according to measurement results, the flame can be positioned in the furnace center, which therefore fills the furnace adequately and makes the temperature field evenly distributed.
  • Study on Heat Rate Regression Model of Steam Turbines Based on υSVM
    WANG Huijie,CHEN Linxiao,LI Yang,SUN Meiqi,YANG Xinjian
    2014, 34(8): 606.
    Abstract ( )   Knowledge map   Save
    To directly reflect the mapping relation between controllable boundary parameters and heat rate of steam turbine, a regression model based on υSVM was established by taking the controllable boundary parameters with strong relevance with heat rate as the input parameters, which was subsequently verified using gray correlation degree model. The process of establishing υSVM regression model based on Libsvm software was described in detail, and the new model was compared with that of the BP neural network. Results show that under smallsample circumstances, the υSVM model has higher regression precision and better generalization capability; whereas under slight fluctuation of input parameters, the outputs of υSVM model are basically stable, indicating that the model has good robustness and can meet precision requirement of actual applications.
  • Numerical Investigation on Flow Field Characteristics of Linear Cascade with Spontaneous Tip Injection
    HU Jianjun,KONG Xiangdong,LI Zhixian,ZHANG Yonggui,ZHANG Yongjian,XU Jinliang
    2014, 34(8): 612.
    Abstract ( )   Knowledge map   Save
    The flow field of a linear cascade with singlehole spontaneous tip injection (STI) was obtained by numerically solving relevant threedimensional Reynoldsaveraged NS equations (RANS), after which the flow interaction between tip injection flow and tip leakage flow (TLF) was analyzed, while the characteristics of both tip leakage and blade load distribution were compared under conditions with and without tip injection, and the influence of relative endwall movement on tip leakage flow with STI was discussed. Results show that the fanshaped low velocity zone downstream the jet orifice occupies part of the leakage flow passage, which produces a suppression effect on the tip leakage flow and influences the blade load distribution in the meanwhile. Compared with the case without STI, when the Reynolds number is 5.764×105, the relative leakage ratio will reduce by 5.42% and the load of single blade will increase by 1.41%, under the condition with STI.
  • Linear Active Disturbance Rejection Control on Coordinated System of a 1 000 MW Ultrasupercritical Power Unit
    MA Yongguang,LI Chao,MA Liangyu,ZHANG Ruiqing
    2014, 34(8): 618.
    Abstract ( )   Knowledge map   Save
    Taking a 1 000 MW ultrasupercritical power unit as an object of study, a new coordinated control scheme was developed for the unit based on linear active disturbance rejection controller (LADRC) in the mode of “coordination control of boiler following (CCBF)”, with two LADRCs respectively for the boiler and the steam turbine. The proposed control strategy was programmed with Matlab, and the twoway data communication between the control program and the fullscope simulator of the given 1 000 MW power unit was achieved with UDP/IP protocol. Simulation tests under load disturbance were carried out for the unit. Results show that the proposed LADRCbased control scheme is significantly superior to the original PID controller in the control effect of both the loadfollowing capability and the main steam pressure stabilization.
  • Harmony Control of Nuclear Reactor Power Based on MCP Standard Transfer Function
    YANG Ping,LIANG Huonan,CHEN Yan,LIU Xiujie
    2014, 34(8): 624.
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    To overcome the deficiency existing in the control of nuclear reactor power, a cascade compensation and statevariable feedback harmony (CSH) controller based on multiple capacity process (MCP) standard transfer function was proposed. The MCPCSH controller was then verified by Simulink simulations, and compared with classical PD control system. Results show that the proposed method has robust tracking capability for zeropoint highorder nonselfregulating process. Compared with PD controller, the new system has features of smaller overshoot and shorter settling time in slope loading tests.
  • DOAS Monitoring by Fourier Transform Filtering Based on Frequency Spectrum Correction
    ZHENG Haiming,WU Hao,LI Guangjie
    2014, 34(8): 628.
    Abstract ( )   Knowledge map   Save
    Frequency spectrum correction was introduced to the data processing based on differential optical absorption spectroscopy (DOAS) by fast Fourier transform (FFT) filtering, while experimental studies were conducted to singlecomponent gases SO2 and NO2 by simulation of spectral line drift. Results show that for singlecomponent gases SO2 and NO2, both the traditional least square method and the corrected FFT filtering can achieve good effects, with an error less than 5%; however, the corrected FFT method has better effect than the uncorrected one; for a drift of two wavelengths, the maximum error of corrected FFT method is 3.65%, and the mean error of traditional least square method is 32.80%, indicating that the former has significantly better effect than the latter.
  • Research on Lowtemperature Corrosion Characteristics of Coal Mill Under Oxyfuel Combustion Conditions
    WANG Chunbo,QIN Hongfei
    2014, 34(8): 633.
    Abstract ( )   Knowledge map   Save
    To solve the lowtemperature corrosion problems existing 〖JP2〗in oxyfuel combustion boilers, a study〖JP〗 was carried out to the effects of recirculation mode, coal category and boiler load on the lowtemperature corrosion of the mill by taking a 600 MW oxyfuel combustion boiler as an example. Results show that the acid dew point of flue gas at mill outlet is sensitive to the desulfurization and dehydration process under recirculation mode; when high sulphur coal is burned, serious lowtemperature corrosion will occur in the mill; the acid dew point of flue gas decreases with the reduction of boiler load, which is determined by both the SO2 and H2O concentration, however, the effect of SO2 is slightly greater than that of H2O.
  • DEM Experimental Study on Kinetic Energy and Coal Storage of Ball Mills
    HE Fang,BAI Yan,ZHANG Ran
    2014, 34(8): 639.
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    Partition computation was performed to the motion status of balls in a coal mill, after which the kinetic energy of balls was used to measure and control the coal storage. Moreover, mill operation process was simulated by PFC3D software platform based on discrete element method, so as to analyze the relationship among the coal quality, coal storage and ball motion under certain quantitatively optimized configuration of operating parameters, and to obtain the variation law of realtime kinetic energy of balls with energy consumption by sliding friction and with total work of cylinder wall, which represent the mill working efficiency. Results show that the impact energy obtained by balls in projectile motion is more than that in cascading motion, and the ball kinetic energy can more accurately reflect the realtime variation of coal storage. The method to control coal storage with ball kinetic energy is therefore proved to be feasible.
  • Analysis on Characteristics of a Supercritical ORC Lowgrade Heat Power Generation System
    TANG Lei,WANG Yuping,YANG Ping,GENG Xiaoru,WENG Yiwu
    2014, 34(8): 646.
    Abstract ( )   Knowledge map   Save
    An analysis was carried out to following three key issues of a supercritical organic Rankine cycle (ORC) power generation system using lowgrade heat source with temperature lower than 150 ℃, such as the working medium selection, the heating process and the system performance, etc. Results show that among all the working mediums suitable for supercritical ORC power generation systems, the one with relatively high critical temperature has higher system thermal efficiency but lower expander inlet pressure and lower condensing pressure; whereas the one with relatively low critical temperature has lower system thermal efficiency but higher energy utilization ratio, higher expander inlet pressure and higher condensing pressure. For the supercritical heater, good heat matching can be achieved between heat source and working medium under the condition of higher heattransfer pressure and lower expander inlet temperature. Under the restriction of heat source inlet temperature and minimum heattransfer temperature difference, there exists an optimum expander inlet temperature and expander inlet pressure, which make the system thermal efficiency reach the highest.
  • Distribution Optimization on Feedwater Enthalpy Rise in Steam Turbine Unit Based on Modified PSO Algorithm
    FU Wenfeng,WANG Lanjing,LI Fei,YANG Yongping
    2014, 34(8): 653.
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    To conveniently and accurately achieve optimal distribution of feedwater enthalpy rise in regenerative heaters, a versatile calculation model was proposed based on modified particle swarm optimization (PSO) algorithm by improving the description of aggregation degree of an adaptive PSO at evolutionary state, which was subsequently applied to optimization calculation of feedwater system in a 1 000 MW steam turbine unit. Results show that the proposed algorithm has better convergence ability and solving accuracy; the unit thermal efficiency has been improved by 0.23% compared with the original design value after optimization. The method is simple to operate and has wide universality.
  • Experimental Study on Magnetic Transformation of S30432 Boiler Tubes After Hightemperature Service
    SHI Zhigang1,DONG Hongnian,LI Yimin,WANG Hongzhe,CAO Haitao,WANG Qihong，HE Xiaodong
    2014, 34(8): 660.
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    Experimental studies were conducted to S30432 hightemperature superheater tubes with relatively high magnetism respectively using magnetic induction intensity measuring instrument, austenite oxide detector, optical microscope, scanning electron microscope, transmission electron microscope and Xray diffractometer, etc. Results show that new tubes have no magnetic equivalent and magnetic induction intensity; higher magnetic equivalent and magnetic induction intensity exist in tubes after service for 1.9×105 h, both of which change greatly in the annular direction, the longer the service time, the higher the magnetic equivalent; causes leading to high magnetism of the tubes are the existence of lath martensite, distributed closely at both sides of the grain boundary; the amount of martensite structure in tubes with longer service time is significantly larger than that with shorter service time; compared with new tubes, the εCu phase dispersed intragranularly in S30432 service tubes is obviously greater in size, which turns to round particle from its original irregular shape.
  • Research on Mechanical Properties of a Steam Turbine Rotor Remanufactured by Laser Cladding
    GUO Shirui,DONG Gang,YE Zhong,YAO Jianhua
    2014, 34(8): 668.
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    To study the tensile, impact and bending properties of a composite material including laser cladding and base metal, experimental tests were conducted to a turbine rotor shaft journal remanufactured by laser cladding with Febased alloy powder, under the premise of controlling the total indicated runout (TIR) within 6.35 μm after laser cladding. Results show that in comparison with the average value of base metal 28CrMoNiV, the tensile and bending strength of the composite material are improved respectively by 11.29% and 24.11%, with an impact absorbing energy of 39 J. According to the mixing rule of parallel model, mechanical properties of the laser cladding are better than those of the base metal 28CrMoNiV; the number of principal and secondary crystal axis in laser cladding is far greater than that in the base metal, resulting in increased tensile strength of the cladding due to existence of high density dislocation that inhibits the sliding of the grain boundary. In comparison with the base metal, grains in the cladding layer are smaller and denser, in which the crack propagation path is of the tortuous kind, resulting in increased toughness of the cladding due to the enhancement of crack initiation energy.