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    Boiler Technology
  • Boiler Technology
    Design and Operation of a 745 t/h CFB Boiler with Bypass Temperature Controlling System for the Reheat Steam
    MAO Jun-hua, TANG Zhi-gang, JING Lei, XIE Yu-rong
    2012, 32(6): 425-429.
    Abstract ( )   Knowledge map   Save
    An introduction is being presented to the design and operation of the first domestic 745 t/h CFB boiler with bypass temperature controlling system for the reheat steam, while influence of the operating condition on NOx and SO2 emission discussed. Performance test results show that the superheater, reheater, cyclone separator and air preheater are all rationally designed; the parameters of reheat steam could be quickly and accurately adjusted by the bypass temperature controlling system; under operating conditions at a load of 220 MW, the average test value of boiler thermal efficiency and the average corrected efficiency are respectively 90.72% and 90.56%; the boiler could be stably and continuously operated at the maximum output of 745 t/h and at the lowest output without auxiliary fuel; the purposes of low NOx and SO2 emission could be achieved if the boiler is rationally operated.
  • Boiler Technology
    Experimental Study on Mixed Combustion of Shenhua Coal with Huolinhe Lignite in a 1 000 MW Power Unit
    GAO Ji-lu, ZOU Tian-shu, LI Zhi-shan, JI Hong-shun, LENG Jie, WU Jing-xing, LI Han-qiong
    2012, 32(6): 430-434.
    Abstract ( )   Knowledge map   Save
    An experimental study was carried out on the mixed combustion of Shenhua coal with Huolinhe lignite in a 1 000 MW power plant, so as to analyze the effect of blending ratio on the maximum mill output, maximum unit output and the unit performance. Combustion optimization tests were performed at an optimal blending ratio, during which problems that may be produced by blending lignite were proposed, while corresponding countermeasures suggested. Results show that the maximum mill output reduces gradually with rising blending ratio of lignite; the effect will be obvious especially when the ratio gets above 40%; the optimal blending ratio of lignite is 30% under the test conditions, in which case the optimal bias of oxygen at outlet of economizer is +0.4, and the optimal bias of baffle opening for over-fire air is -10% at rated load. Based on combustion adjustment, the coking problems occurring on boiler rear wall due to mixed combustion with lignite has basically been solved, with a 0.07% increase of boiler efficiency and a NOx emission of 293.2 mg/m3.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Experimental Study of the Turbulent Flow Downstream of Film Cooling Holes on a Flat Plate
    LIANG Jun-yu, MENG Bao-bao, KANG Shun, ZHAI Li-na
    2012, 32(6): 435-439.
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    Turbulent flow structures downstream of the straight and curved cooling hole were measured by means of 2D PIV (Particle Image Velocimetry) at blowing ratios of 0.5 and 1, with a Reynolds number of 480, during which the mean velocity, vorticity fields and smoke visualizations were obtained on the central symmetry plane and four cross sections, while the influence of hole structure on development of downstream vorticity field analyzed along the flowing direction. Results show that compared with straight holes, the curved hole produces a lower jet trajectory, which helps to raise the adhesion force of cooling film to wall surface, and therefore improve the cooling efficiency; simultaneously, the curved hole provides stronger transverse momentum, which makes the curved jet transversely expand more and finally improves the transverse coverage of cooling film.
  • Steam Turbine and Gas Turbine
    Experimental Study on Steady and Dynamic Performance of a Packed Saturator
    SUN Bo, SHAN Song-wu, LIU Yong-wen, SU Ming
    2012, 32(6): 440-444.
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    An experimental study has been carried out on the steady and dynamic performance of a packed saturator, so as to analyze how the water/air inlet flow and water inlet temperature influence the heating and moisturizing process, with focus on the variation law of the water outlet temperature, air outlet temperature, humidity difference between inlet and outlet air, pressure drop and liquid holdup in the packing section, etc. Results show that at the same flow of water inlet, the heating and moisturizing performance can be improved by raising the water-air ratio and water inlet temperature; with the rise of air velocity, the humidity difference reduces, but the prssure drop and liquid holdup increase; under dynamic conditions with a disturbance of inlet variables, both the liquid holdup and water outlet temperature take a longer time to reach a new stable state than that required by pressure drop.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Direct Neural Network Control for a Fuel-Steam Pressure System Based on Differentiator
    CUI Zhi-qiang, LIU Ji-zhen, LIU Jin-kun
    2012, 32(6): 445-449.
    Abstract ( )   Knowledge map   Save
    To achieve adaptive control without modeling information for boiler steam pressure in the fuel-steam pressure system, a direct neural network controller is designed on the basis of a priviously developed sliding-mode controller based on high-gain differentiator, which does not require measurement of speed and acceleration signals. The closed system is proved to be stable by Lyapunov analysis. Simulation results indicate that good tracking performance of boiler steam pressure can be guaranteed by using neural network controller based on differentiator.
  • Automatical Controlling and Detecting Diagnosis
    A Wavelet Method for Denoising of Acoustic Emission Signals Based on LabVIEW
    GUO Min-chen, MEI Yong, MA Ying, CHEN Wen-fei, WANG Bo-ping
    2012, 32(6): 450-453.
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    To solve the problems of rubbing faults existing in sliding bearings of steam turbine, an effective diagnosis method is being proposed. The specific way is to denoise the acoustic emission(AE) signals previously acquired by AE detector from the bearings, then to analyze the processed AE signals using spectrum method, and finally to estimate the actual rubbing details. An experimental study has been carried out on the test rig of a 300 MW steam turbine rotor. Results show that via above method, rubbing faults of turbine rotor can be accurately predicted, based on which on-line monitoring of steam turbine is achieved while the security of the unit guaranteed.
  • Automatical Controlling and Detecting Diagnosis
    Fault Diagnosis of Steam Turbine Based on MPSO-SVM Algorithm
    SHI Zhi-biao, SONG Quan-gang, MA Ming-zhao, LI Qi
    2012, 32(6): 454-457.
    Abstract ( )   Knowledge map   Save
    To overcome the blindness of artificial selection for nuclear function parameters and penalty factors by Support Vector Machine (SVM) as well as the deficiency of easily falling into local minimum at later stage of traditional Particle Swarm Optimization (PSO), a vibration fault diagnosis model has been established for steam turbine based on a newly proposed modified particle swarm optimization (MPSO) algorithm, with which pattern recognition is performed using fault data. Results show that the model can help to realize automatic optimization on relevant SVM parameters and achieve global optimal solution. Compared with PSO-SVM and GA-SVM method, the MPSO-SVM algorithm has a faster convergence speed and higher classification accuracy.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Sygas Flame Structures of a Dual-swirled Burner at Different Equivalent Ratios
    XIE Yue-sheng, HU Guo-ju, GUO Pei-qing, GE Bing, ZANG Shu-sheng
    2012, 32(6): 458-462.
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    An experimental study has been performed to investigate the syngas flame structures of a dual-swirled burner at different equivalent ratios, using a planar laser induced fluorescence (PLIF) system, high-temperature thermocouples and an infrared gas analyzer. Results show that the syngas flame exhibits a crescent shape at a relatively low equivalent ratio of 0.2; with the rise of equivalent ratio, the flame shows an M-shaped root, and its spray angle reduces at both inside and outside, while the lift-off height and penetration depth increase. Simultaneously, large areas of chemical reaction appear downstream of the combustor, with a compressed flame root, raised exhaust temperatures and a reduced CO emission.
    • Environmental Science
  • Environmental Science
    Effect of Coal Type and Pyrolysis Condition on Removal Efficiency of Flue Gas Mercury by Coal Char
    LI Qian-kun, ZHOU Jin-song, LUO Zhong-yang, ZHANG Yi, CEN Ke-fa
    2012, 32(6): 463-468.
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    Effect of coal type, pyrolysis temperature and time on mercury adsorption by coal char was studied in a bench-scale fixed bed by using X-ray photoelectron spectroscopy and Autosorb-1-C analyzer. Results show that the rank of coal seems to have a large effect on the adsorption of mercury vapors; under the same production conditions, the removal efficiency by lignite char is above 90%, obviously higher than that by bituminous char below 40%. For the same pyrolysis time, the removal efficiency increases and the breakthrough time reduces with rising pyrolysis temperature. At the same pyrolysis temperature, the mercury removal efficiency increases first and reduces later on with rising pyrolysis time, which reaches the highest at a pyrolysis time of 30 min.
  • Environmental Science
    Effect of Coal Ash on NOx Emission of CFB Boilers
    ZHANG Jun-chun, CHENG Le-ming, HUANG Chen,XIE Gui-lin, FANG Meng-xiang
    2012, 32(6): 469-475.
    Abstract ( )   Knowledge map   Save
    Experimental tests were carried out by burning typical bituminous and lignite coal in a bench-scale fluidized bed, during which the emitted concentration of both N2O and NO was measured with and without addition of coal ash or inorganic minerals generally contained in coal ash (including CaO, MgO, Fe2O3, Al2O3, CaSO4, and MgSO4). Results show that coal ash may help to reduce the N2O emission and raise the NO emission; the total conversion rate of fuel nitrogen to NOx increases with rising mass fraction of coal ash; the main active components in coal ash affecting the NOx emission are respectively CaO, Fe2O3, and MgO.
    • New Energy
  • New Energy
    An Analysis on Thermal Performance of CPC Solar Collectors
    GAO Hong-yu, WANG Hui-tao, WANG Hua, HUANG Jun-wei, GE Zhong
    2012, 32(6): 476-480.
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    By analyzing the heat-transfer model of compound parabolic concentrator(CPC) evacuated tube collector, and based on expressions respectively for the overall heat loss coefficient, thermal efficiency factor, heat removal factor and instantaneous efficiency, a performance prediction model has been developed for the finned CPC collector with glass cover, while a calculation and a comparison made to the instantaneous efficiency of collectors with and without glass cover. Results show that the collector with glass cover has a thermal efficiency even lower than that without glass cover, under the same radiation intensity, when the temperature difference is small between the working medium and the environment; however, when the temperature difference gets up to a certain degree, the former one will be better than the latter one, i.e. the collector with glass cover will have a higher thermal efficiency.
  • New Energy
    Comprehensive Optimization on Aerodynamic and Aeroacoustic Performance of Airfoils
    ZHUO Wen-tao, JI Zeng-chuan, CHEN Er-yun, DAI Ren, HUANG Yi
    2012, 32(6): 481-486.
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    Taking both the aerodynamic and aeroacoustic performance as the objectives of optimization, a multi-objective optimization method was proposed for low-speed airfoils by using Bezier curves to describe the airfoil geometry, applying the analysis method of iterative potential flow and boundary layer (IBL) flow to calculate the flow field, using the Brooks-Pope-Marcolini airfoil self-noise semi-empirical model to predict the aerodynamic noise and adopting Powell method to obtain the optimized airfoil. The multi-objective optimization method has been verified with a NACA0012 prototype airfoil in different weight assignment schemes. Results show that compared with the prototype airfoil, the optimized one has a higher lift-drag ratio, lower acoustic level and better aerodynamic and aeroacoustic performance under design conditions.
    • Energy System Engineering
  • Energy System Engineering
    Design and Optimization of the Low-temperature Waste-heat Dual-cycle Power Generation System
    TANG Yuan-qiang, YU Yue-feng
    2012, 32(6): 487-493.
    Abstract ( )   Knowledge map   Save
    The screw expander dual-cycle system was adopted for power generation by recovering low-temperature waste heat, for which thermal design calculation was performed by fitting the thermal physical parameters of organic working medium R245fa. Two approaches for determining evaporating temperatures were proposed and compared using first and second law of thermodynamics by taking the system net power and efficiency as the optimization objects for the heat source per unit mass. Results show that with the rise of evaporating temperature, there exists an optimal evaporating temperature, in which case the system net power achieves the highest, and the system efficiency grows gradually; more waste heat and most exergy are recovered by the system when the net power of system reaches the highest, and the corresponding evaporating temperature is therefore determined as the optimal one; at a constant evaporating pressure, all the waste heat recovery, the system net power and the net efficiency reduce with rising superheat degree, so the saturated steam power cycle is recommended.
  • Energy System Engineering
    Decision of the Most Economical Coal for Power Plants Based on Data Mining Technology
    RAN Peng, LI Geng-sheng, ZHANG Shu-fang, WANG Song-ling
    2012, 32(6): 494-500.
    Abstract ( )   Knowledge map   Save
    By analyzing the effects of coal quality on operating cost of coal-fired power plants, an evaluation model was established for calculating the comprehensive use cost of fuel coal. Based on fuzzy association rule data mining technology, an algorithm was proposed to determine the correlations between the coal quality and the power plant operating cost, including the coal transportation cost, the anti-pollution cost, the coal purchasing cost, and the equipment maintenance cost, while a method put forward for decision of the most economical coal. On the basis of 3 years operating data of a power plant, an analysis has been carried out on comprehensive cost of the 4 coals in the pre-procurement plan, after which the most economical coal is determined. Results show that not only the production processes of power plant, but also the coal price and coal quality should be considered in determination of the coal procurement policy. It is not always more economical to burn low-price low-quality coal than high-price high-quality coal. In above case, coal No.2 is finally determined as the most economical one.
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