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    Boiler Technology
  • Boiler Technology
    Numerical Simulation on Blended Coal Combustion with Anthracite in W-shaped Flame Boilers
    ZHU Guang-ming, YAO Bin, DUAN Xue-nong, WU Zeng-jin,JIAO Qing-feng, YANG Yi, CHEN Yi-ping
    2012, 32(5): 345-350.
    Abstract ( )   Knowledge map   Save
    Proximate analysis and thermogravimetric tests were carried out to two typical kinds of anthracite, while numerical simulation performed on blended coal combustion with anthracite in a direct-fired pulverizing system for W-shaped flame boilers at different coal blending modes using dual-mixture fraction/PDF approach, during which the in-furnace temperature field, oxygen concentration distribution and velocity field were obtained. Results show that the proximate analysis data for above two kinds of anthracite are basically the same, but their grindability and combustion characteristics are quite different. At the combustion mode of “blending before furnace”, the in-furnace temperature field, oxygen concentration distribution and velocity field are quite symmetrical, but the burn-off degree of coal powder is lower and the furnace outlet temperature is higher than the mode of “pulverizing coal in different mills”. At the combustion mode of “pulverizing coal in different mills”, the operation pattern of coal mill affects the combustion economy greatly, in which case optimization is possible even under the condition that one kind of anthracite is blended with another, therefore the combustion mode of “pulverizing coal in different mills” is believed to be beneficial for improvement of the combustion economy.
  • Boiler Technology
    Study on Attrition Behavior of CFB Bed Material During Start-up Process
    SUN Bai-zhong, TAN Ping, WANG Qing, LIU Hong-peng, LI Shao-hua
    2012, 32(5): 351-355.
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    Taking the shale ash of the first domestic 65 t/h low rate CFB boiler as an object of study, experimental tests were carried out in a bench-scale fluidized bed so as to analyze how the fluidizing velocity, fluidizing time and bed temperature influence the attrition behavior of the bed material, based on which a second-order attrition model was established. Results show that the shale ash experiences in total rapid decay and stable attrition two stages in fluidized state; its mass reduces exponentially with rising fluidizing time; the degree of ash attrition increases with the rise of bed temperature and fluidizing velocity; the second-order attrition model can well predict the mass changing of shale ash in the fluidized bed.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Study on Operation Mode Optimization for a 600 MW Supercritical Steam Turbine
    FAN Xin, QIN Jian-ming, LI Ming, FU Chen-peng
    2012, 32(5): 356-361.
    Abstract ( )   Knowledge map   Save
    A description is being made to the optimization principle of varying load operation of steam turbine, together with an introduction to the optimization experiment for a 600 MW supercritical steam turbine under varying load operation conditions. According to actual flow characteristics of the HP control valve, an optimized operation mode is obtained by comparing its thermal efficiencies respectively corresponding to 6 typical loads (540 MW, 480 MW, 420 MW, 360 MW, 330 MW and 300 MW), based on which fitting functions for relevant operation curves are proposed on the basis of corrected exhaust pressure. Results show that the optimized operation mode may help to reduce the heat consumption rate of steam turbine under low load condition and accordingly improve its economy in varying load operation.
  • Steam Turbine and Gas Turbine
    Numerical Simulation of Slot Film Cooling Model for Curved Surfaces
    HUANG Yi, XU Qiang, DAI Ren, ZHUO Wen-tao, LI Ying
    2012, 32(5): 362-367.
    Abstract ( )   Knowledge map   Save
    To study the effect of surface curvature on film cooling performance of turbine blade, a numerical simulation was carried out to the two-dimensional slot model for curved (concave, convex and plane) surfaces, during which heat-transfer coefficients on above surfaces were calculated at an injection angle of 35°, a density ratio of 1.5 and at different blowing ratios (0.5, 1.2 and 2.0) using RNG k-ε turbulent model. Results show that at a low blowing ratio of 0.5, the heat-transfer coefficient reduces with rising pressure gradient on curved surfaces; at a medium blowing ratio of 1.2, the heat-transfer coefficient is intensified on all surfaces due to enhanced disturbance by injection flow, in which case, the heat transfer on convex surface is weaker than on concave surface; at a high blowing ratio of 2.0, the surface curvature effects little on heat transfer, resulting in basically the same heat-transfer coefficient on all surfaces.
  • Steam Turbine and Gas Turbine
    Numerical Simulation of Film Cooling Effectiveness with Double Outlet Hole Injection at Different Blowing Ratios
    LI Guang-chao, WU Dong, ZHANG Wei, WU Chao-lin
    2012, 32(5): 368-372.
    Abstract ( )   Knowledge map   Save
    To study the influence of blowing ratio on film cooling effectiveness with injection through a novel film cooling hole, a numerical simulation was carried out on the cooling effectiveness with one-inlet double-outlet hole injection by the use of Fluent software to solve Navier-Stokes equation at blowing ratios of respectively 0.5, 1.0, 1.5 and 2.0, during which various flow fields and cooling effectiveness were obtained at above blowing ratios. Results show that blowing ratio has significant influence on the film cooling effectiveness. With the rise of blowing ratio, the cooling effectiveness changes in different laws with the orientation angle of hole; for an orientation angle of 30°, the cooling effectiveness reaches the highest at a blowing ratio of 1.0, whereas for an angle of 45°, it rises with growing blowing ratio, and for an angle of 60°, the cooling effectiveness reduces with the increase of blowing ratio. At higher blowing ratios, the optimum orientation angle is found to be 45°, when better cooling effectiveness can be obtained.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    The Multimodel-based Active Disturbance Rejection Control for Water Level of Steam Generator in Nuclear Power Plants
    GU Jun-jie, JI Nai-liang, SUN Yu-jie, TAN Jun-long, WANG Dong-xu
    2012, 32(5): 373-377.
    Abstract ( )   Knowledge map   Save
    Considering the nonlinear distribution characteristics of water level control for steam generator in nuclear power plants, a novel control strategy is proposed in combination of active disturbance rejection technology with multimodel-based control, in which a multimodel-based control system is designed for the steam generator, and an independent active disturbance rejection controller is prepared for each model under different loading conditions, so as to realize online estimation at extended states, and achieve prompt disturbance elimination by independent disturbance compensation. Simulation results show that the control strategy can help to realize accurate dynamic control for water level of steam generator, which is featured by strong robustness, high disturbance rejection capability, simple computation and facile commissioning.
  • Automatical Controlling and Detecting Diagnosis
    Application of Pseudo-random Sequence Signal in Acoustic Pyrometry of Boiler Furnace
    ZHANG Shi-ping, AN Lian-suo, LI Geng-sheng, SHEN Guo-qing, FENG Qiang, DENG Zhe
    2012, 32(5): 378-382.
    Abstract ( )   Knowledge map   Save
    To obtain the temperature field in boiler furnace, a single-path monitoring system was developed for temperature measurement of flue gas in boiler furnace using pseudo-random sequence signal. Hot-state experiments were carried out for two boilers of respectively 200 MW and 300 MW, of which the measurements were verified by self-developed K ceramic thermocouples. Results show that the pseudo-random sequence signal can be taken as sound source signal in acoustic pyrometry after its too broad bandwidth is narrowed so as to concentrate the energy. The measurement error between acoustic pyrometry and thermocouple method is within 2%, and the curve of temperature measured by acoustic pyrometry using pseudo-random sequence signal agrees well with that of the unit load, proving the measurements to be reliable.
  • Automatical Controlling and Detecting Diagnosis
    Analysis of Non-isokinetic Sampling Deviation for Measurement of Steam Humidity in Microwave Cavities
    HAN Zhong-he, ZHANG Mei-feng, QIAN Jiang-bo
    2012, 32(5): 383-387.
    Abstract ( )   Knowledge map   Save
    To accurately calculate the sampling deviation of microwave cavity, the non-isokinetic sampling principle was analysed, based on which measurement errors of wetness due to sampling deviation were obtained by computing the trajectory of droplets in two sampling ends of different structures through Lagrangian method under different conditions and droplet sizes. Results show that sampling deviation is less affected by the droplet size at low Mach number, while an obviously close relation with it has been seen as well as working conditions at high Mach number. It is found that optimizing the sampling end of the cavity can effectively reduce the measurement error. Since the Mach number of steam turbine exhaust is relatively low in power plant, therefore higher precision of sampling may be reached for measurement of steam humidity in microwave cavity via appropriate correction of sampling errors.
  • Automatical Controlling and Detecting Diagnosis
    Nonlinear Vibration Characteristics of a Vibro-impact System with Clearance
    LU Xu-xiang, LIU Zheng-qiang, HUANG Shu-hong, LI Lu-ping
    2012, 32(5): 388-393.
    Abstract ( )   Knowledge map   Save
    A dynamic model for vibro-impact system with clearance has been established based on generalized Hertz contact theory, which is numerically solved by 4-5 order Runge-Kutta method. Non-linear vibration characteristics of the model is studied by analyzing the bifurcation diagrams, the phase diagram, the Poincaré maps and the power spectrum chart respectively obtained at different frequency ratios, exci-ting force amplitudes and clearances. Results show that period, period doubling and chaotic motion occur in the vibro-impact system with the variation of frequency ratio, amplitude of exciting force and size of clearance, among which the frequency ratio and amplitude of exciting force play an important role in influencing the non-linear vibration characteristics, when broad chaotic bands appear; the size of clearance effects little on the system response, however, within the small variation range of clearance, the vibration characteristics change greatly.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Study on Thermal Performance of a Wet Cooling Tower with Windshield Board
    LI Yong-hua, ZHEN Hai-jun, TANG Jin-ming
    2012, 32(5): 394-398.
    Abstract ( )   Knowledge map   Save
    To solve the icing problems in wet cooling towers at areas such as the bottom surface of filler, air inlet and base torus in winter in north China, windshield boards are generally installed at the air inlet. Based on a newly-built heat and mass transfer model, CFD simulation and analysis have been performed to study the thermal performance of a wet cooling tower installed with different layers of windshield board at different horizontal wind speeds and environmental temperatures. Results show that when the wind speed is lower than 4m/s, the temperature will be relatively low at areas facing the wind in the tower, where icing troubles easily occur; with the rise of wind speed, the low-temperature zone generally moves to the leeward side; at a wind speed of 8 m/s, as environmental temperatures at -10 ℃, -17 ℃, -23 ℃, the optimal layers of windshield to be installed in the tower are believed to be 1, 3 and 5 respectively, which effectively help to improve the temperature field in the tower and prevent the tower from being frozen.
  • Auxiliary Equipment Technology
    Deposition Behavior of Scales on Brass and CopperSurface in CaCO3 Solution
    SHENG Jian, ZHANG Hua, SHI Xue-fei, ZHAO Ping
    2012, 32(5): 399-403.
    Abstract ( )   Knowledge map   Save
    To study the deposition behavior of CaCO3 scales on brass and copper surface, experimental tests were carried out at static state in 0.5 mmol/L CaCO3 solution at 35 ℃, during which the scales obtained in different dipping durations were measured by weighing method and analyzed using scanning electron microscope. Results show that the scales are found to be more easily formed on copper surface than on brass surface under same conditions; higher pH value promotes not only the growth of scales, but also the formation of square aragonite and calcite, and the square aragonite will finally get recrystallized into the thermodynamically most stable phase (calcite); with the rise of pH value, both the homogenous nucleation in solution and the heterogeneous nucleation on metal surface increase, and the former one increases more than the latter one.
  • Auxiliary Equipment Technology
    Characteristics of CaSO4 Crystallization Fouling on Two Vortex Generators
    XU Zhi-ming, LIU Zuo-dong, WANG Yu-peng, ZHANG Zhong-bin
    2012, 32(5): 404-407.
    Abstract ( )   Knowledge map   Save
    To find the fouling characteristics on vortex generators, experimental tests were carried out to study the fouling formation in heat-transfer processes by taking supersaturated CaSO4 solution of 2 100 mg/L as the medium, during which the growth of fouling deposit was obtained by off-line weighing me-thod. Results show that both the size and pitch of vortex generator play a role in influencing the fouling deposition. For a fixed diameter of vortex generator (4 mm), the amount of fouling deposit per unit area of metal surface increases with rising pitch, whereas for a fixed pitch of vortex generator (10 mm), the amount of fouling deposit reduces with rising size.
    • New Energy
  • New Energy
    Simulation of DME Synthesis from Biomass Gasification in Interconnected Fluidized Beds
    JIANG Hong-ling, XIAO Jun, SHEN Lai-hong
    2012, 32(5): 408-413.
    Abstract ( )   Knowledge map   Save
    Taking the rice straw as an object of study, a simulation model for synthesis of dimethyl ether (DME) from biomass gasification in interconnected fluidized beds was established using Aspen Plus software, so as to analyze how following factors influence the synthesis process, such as the gasification temperature, steam/biomass (mS/mB) mass ratio, synthesis temperature and pressure, absorption tower operating pressure and the absorbent/DME (nA/nD) flow ratio, ect. Results show that for the purpose of direct DME synthesis from biomass gasification in interconnected fluidized beds using steam gasification technology, it is suggested that relevant parameters be set as follows: gasification temperature at 750 ℃, mS/mB=0.3, and DME systhesis temperature and pressure respectively at 260 ℃ and 4 MPa; if water is taken as the absorbent, the absorption tower operating pressure is proposed to be within 3-4 MPa with an nA/nD ratio of 0.5. Under above optimal conditions, the DME yield may reach 6.1 mol per kg biomass.
    • Material Science
  • Material Science
    Mechanical Properties of 30Cr1Mo1V HP-IP Rotor Steel After Long-term Service
    ZHAO Shuang-qun, LIN Fu-sheng
    2012, 32(5): 414-419.
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    Mechanical properties of 30Cr1Mo1V steel samples taken from different areas of an HP-IP turbine rotor after long-term service were studied by tensile, impact and FATT50 tests respectively at room and high temperatures, after which causes leading to the material changes in strength and toughness were analyzed. Results show that in areas of rotor enduring high service temperatures, the morphology, distribution and sizes of carbides may change a lot; the carbides precipitated from bainite and ferrite will aggregate and grow; carbides may gradually precipitate and get coarsening at the boundary of original austenite grain and that between bainite and ferrite. The degradation of tensile properties differs slightly at different locations, and the greatest degradation occurs in the area enduring highest service temperatures, where the corresponding toughness will reduce accordingly. The decrease of total impact energy is mainly from the decrease of the crack forming energy, and the crack propagation energy doesn’t show large difference for all locations. Compared with areas enduring low service temperatures, the fracture appearance transition temperature (FATT50) in areas enduring high service temperatures is obviously higher.
  • Material Science
    Experimental Study on Sulfuric Acid Dewpoint Corrosionin Simulated Atmospheric Conditions
    ZHAO Qin-xin, ZHANG Zhi-xiang, DU Wen-zhi, ZHANG Zhi-chao
    2012, 32(5): 420-424.
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    To solve the problem of low-temperature corrosion occurring in waste heat recovery of power boilers, low-temperature corrosion tests were performed at wall temperatures of 43 ℃, 55 ℃, 65 ℃, 75 ℃ and 85 ℃ for 72 hours by taking 4 dewpoint corrosion resistant steels as the object of study, such as Corten, ND, 316L and GR2, and 20 and 20G as the comparison materials, during which the test specimens were analyzed by scanning electron microscope and energy dispersive spectrometer. Results show that the corrosion resistance of above 6 materials follows the descending order as below: GR2>ND>316L>Corten>20G>20. ND steel is considered as the most ideal material for deep cooling facility of flue gas. At the wall temperature of 65 ℃, ND steel undergoes the least low-temperature corrosion.