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    Boiler Technology
  • Boiler Technology
    Experimental Study on Swirl Number of a 2 150 t/h Tangentially Fired Boiler
    JIN Yunli
    2013, 33(10): 745-752.
    Abstract ( )   Knowledge map   Save
    To reduce the steam temperature deviation of a 2 150 t/h tangentially fired boiler, experimental studies were performed on the correlation between the swirl number and the flame center track, while an analysis carried out to the influence of combustion adjustment on the swirl number. Based on experimental analysis and combined with steam temperature deviation, the running track of flame center varying with the swirl number was obtained. By calculation from perspective of wind box differential pressure control, laws governing the variation of air distribution unevenness on the swirl number were studied. Results show that raising the unevenness of air distribution will lead to increased swirl number; there does not exist a definite correspondence between the swirl number and the load; the swirl number reduces with decreasing oxygen volume fraction, and the fluctuation range of swirl number was enlarged during unloading process, which may lead to large steam temperature deviation and overheating failures; the downswing of burner helps to raise the swirl number; the increase of reverse swirl number caused by too large air flow of reversed tangential separated overfire air (SOFA) can also enlarge the steam temperature deviation.
  • Boiler Technology
    Combustion Adjustment Tests for Preventing Overheating Problems in a 600 MW Supercritical W-flame Boiler
    ZHOU Wentai, CHENG Zhihai, JIN Xin, HE Xiang
    2013, 33(10): 753-758.
    Abstract ( )   Knowledge map   Save
    To solve the water wall overheating problems occurring in the No.2 600 MW supercritical W-flame boiler in Yunnan Huadian Zhenxiong Power Generation Co., Ltd., an analysis was carried out, based on which combustion adjustment tests were performed on the aspects of secondary air distribution, coal particle size and primary air pressure, etc. Results show that the problems are found to be caused by both the unreasonable air distribution mode and the instable in-furnace combustion, which are finally solved by combustion adjustment, resulting in uniform in-furnace air distribution, reduced fluctuation of furnace negative pressure, stabilized signals of flame detection, cleared flame TV images and improved furnace combustion.
  • Boiler Technology
    Numerical Simulation on Mixing Characteristics of Particles in Circulating Fluidized Bed
    LI Bin, SONG Xiaolong
    2013, 33(10): 759-764.
    Abstract ( )   Knowledge map   Save
    To study the mixing behavior and mixing mechanism of particles in circulating fluidized bed, numerical simulations were carried out on axial and radial mixing of the particles using the discrete element method based on computational fluid dynamics. From the moving speed perspective of the gas and particles, an analysis was made to the overall mixing process of the particles by combining the axial mixing with radial mixing, while the mixing degree quantitatively evaluated based on the standard deviation of characteristic concentration, thus obtaining the gas velocity field, particle velocity field and particle volume fraction distribution in the bed. Results show that the velocity distribution of particles is basically consistent with that of the gas; dense phase appears in the lower part while the dilute phase appears in the upper part; the effect of axial mixing is better than the radial mixing; improving the air velocity of fluidization helps to accelerate the mixing of particles in the bed, and radial mixing is more sensitive to the air velocity of fluidization than axial mixing.
  • Boiler Technology
    Effect of Recirculation Mode on Acid Dew Point of Flue Gas in an Oxy-fuel Combustion Boiler
    WANG Chunbo, QIN Hongfei
    2013, 33(10): 765-769.
    Abstract ( )   Knowledge map   Save
    Taking a 600 MW oxy-fuel combustion boiler as an example, variation laws of H2O and SO2 vo-lume fractions in the flue gas were studied under three different recirculation modes, during which a prediction was made to the acid dew point of flue gas, while an analysis performed to the effect of recirculation mode on the low-temperature corrosion of its rear heating surfaces. Results show that the acid dew point of flue gas in oxy-fuel atmosphere is 15 K higher than that in air atmosphere; the H2O and SO2 volume fractions are sensitive to the desulfurization and dehydration process during recirculation period; great difference of acid dew point exists among three recirculation modes, and the maximum difference is high up to 11 K. At the same time, the acid dew point of flue gas decreases with the increase of primary flue gas recirculation ratio.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Calculation and Analysis on Vibration Behaviors of Medium Pressure Rotor in a 500 MW Steam Turbine Unit
    ZHANG Lei, ZHANG Junjie, XU Yatao, ZHAO Zongbin, QIN Zhiwen
    2013, 33(10): 770-774.
    Abstract ( )   Knowledge map   Save
    To analyze the safety of medium pressure rotors in a 500 MW steam turbine unit when they pass through the critical speed, calculation and analysis were conducted to vibration behaviors of the medium pressure rotor with the maximum vibration amplitude in actual operation, of which the first order and second order critical speed were calculated with self-developed rotor dynamics software, and its maximum static deflections were obtained respectively at the first order critical speed and 3 000 r/min, and subsequently corresponding equivalent acceleration of gravity was calculated at different rotation speeds with a static deflection analysis program. Unbalanced centrifugal forces of the rotor were finally simulated at different rotating speeds by applying equivalent acceleration of gravity in Ansys, in which case corresponiding distribution of equivalent bending stress was analyzed. Results show that the equivalent acceleration of gravity at the first order critical speed and 3 000 r/min is respectively 10 m/s2 and 1 m/s2, and the maxium equivalent bending stress calculated under various working conditions is far less than the yield limit of the material.
  • Steam Turbine and Gas Turbine
    Numerical Investigation on Factors Influencing Leakage Flow Characteristics of Honeycomb Seals
    ZHANG Yi, CAO Lihua, SUO Fujun, LI Yong, JIANG Sibo
    2013, 33(10): 775-781.
    Abstract ( )   Knowledge map   Save
    Three-dimensional flow fields in a honeycomb seal were numerically simulated using RNG k-ε two-equation turbulence model and Simple algorithm with Fluent software, so as to analyze the leakage flow characteristics from the aspects of pressure ratio, cell size, depth and wall thickness of the honeycomb. Results show that the honeycomb seal with special hexagonal structure divides the leakage flow into many small vortices, where three-dimensional anticlockwise turbulent spirals can be seen; with the rise of pressure ratio, the leakage flow increases, but in a reducing gradient; the smaller the cell size is, the more the number of small vortices will be divided into, and the clearance friction will rise, resulting in reduced leakage flow; with the rise of honeycomb depth, the leakage flow drops, and when the depth gets above 4 mm, the dropping gradient reduces; the leakage flow decreases slightly with rising wall thickness of the honeycomb.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Identification of Hammerstein Model for a CFB Boiler Based on Quantum Genetic Algorithm
    WANG Dongfeng, REN Yanyan, LIU Changliang, HAN Pu
    2013, 33(10): 782-788.
    Abstract ( )   Knowledge map   Save
    Hammerstein models were used to identify two typical systems of a circulating fluidized bed (CFB) boiler, of which the nonlinear and linear parts were respectively expressed by polynomials and difference equations, and the identification problems of models were converted into the optimization searching in parameter space using quantum genetic algorithm (QGA). Optimal solutions of unknown parameters were solved so as to obtain specific models of the two systems in the CFB boiler. Moreover, a series of simulation experiments were performed with field data. Results show that Hammerstein models can well express the characteristics of typical systems in CFB boilers, and mathematical models of high precision can be obtained by using quantum genetic algorithm to optimize the parameters.
  • Automatical Controlling and Detecting Diagnosis
    Steam Generator Water Level Control Based on SDRNN-ADRC Optimization
    ZHOU Hongyu, WANG Zhenghai, HUANG Jianping, ZHAO Qian
    2013, 33(10): 789-794.
    Abstract ( )   Knowledge map   Save
    To solve the problems existing in steam generator (SG) water level control system, an active disturbance rejection control (ADRC) scheme was proposed, in which an extended state observer was used to estimate and dynamically compensate the internal and external disturbance in feed forward way, and simultaneously, the contradiction between rapidity and overshoot of the control system was alleviated through nonlinear feedback regulation based on state error vector. Meanwhile, an identification method based on second-order diagonal recurrent neural network (SDRNN) was proposed to dynamically identify SG Jacobian information for real time optimization of the ADRC parameters. Besides, simulation tests of SG water level were carried out with the controller under different disturbances, such as water level disturbance, steam disturbance and feed water disturbance, of which the results were compared with that of feedforward-cascade PI controller. Results show that the SG water level control system based on SDRNN-ADRC optimization has excellent dynamic and static control performance, with small overshoot and small steady-state error.
    • Energy System Engineering
  • Energy System Engineering
    Off-design Performance Analysis of a 600 MW Solar-Coal Hybrid Power Generation System
    LIN Lin, ZHANG Yanping, HUANG Shuhong
    2013, 33(10): 795-802.
    Abstract ( )   Knowledge map   Save
    Based on the 600 MW supercritical steam turbine model set up on Aspen Plus platform, a model of solar-coal hybrid power generation system was established, which uses the steam from solar collector instead of extraction from high-pressure heater. Operation status of the solar-coal hybrid system was simulated under four different loading conditions, while the variation law of both the energy consumption and turbine steam flow was analyzed for three schemes of solar-coal hybrid systems under off-design working conditions. Results show that the proposed solar-coal power generation system can significantly reduce the coal-consumption rate of 600 MW coal-fired power unit without obvious changes of the turbine steam flow. All the three schemes are applicable for retrofit of coal-fired power units in operation, which can serve as an effective way not only for energy saving and emission reduction of coal-fired power units, but also for stable operation of solar power generation systems.
  • Energy System Engineering
    Quantitative Analysis of Waste Heat Resources Based on the Second Law of Thermodynamics
    ZHOU Shaoxiang, ZOU Wenbo, HU Sangao, LIANG Shuangyin
    2013, 33(10): 803-807.
    Abstract ( )   Knowledge map   Save
    An analysis was performed to the quantitative calculation method for waste heat recovery and its exergy according to thermodynamic fundamentals. Based on the fuel specific consumption analysis of energy utilization, formulae were derived for quantitative calculation of coal saved by waste heat recovery using the second law of thermodynamics, while a comparative analysis of energy-saving potential through waste heat recovery and power generation made among gas turbine, cement plant and coal-fired power plant. Results show that the amount of energy economized by waste heat recovery depends on not only the absolute quantity of waste heat, but also the temperature level, i.e. the lower the temperature level, the less the coal saved.
  • Energy System Engineering
    Study on Mechanism of CO2 Capture Process and its Integration with Power Generation Systems
    HAN Zhonghe, WANG Jixuan
    2013, 33(10): 808-814.
    Abstract ( )   Knowledge map   Save
    Calculation formulae for regeneration energy consumption of a CO2 capture system were derived, while the influence of absorbent property on the regeneration energy consumption analyzed, after which corresponding regeneration energy consumptions were calculated under different mass fractions of absorbent. Taking the N600-24.2/566/566 power unit as an example, a number of CO2 capture schemes were proposed based on integrated modes of solar-coal hybrid power generation system, in which case relevant thermo-economic indexes were calculated and compared using heat balance method, such as the heat consumption rate, the power generation standard coal consumption and the thermal efficiency, etc. Results show that the scheme 5 with application of solar energy is found to be the most economical one for its lowest heat consumption rate and lowest power generation standard coal consumption, under conditions of design radiation intensity and constant main steam mass flow.
    • Material Science
  • Material Science
    Mechanical Properties and Microstructures of Dissimilar Steel Welded Joints Between Domestic Steel S30432 and Steel T92
    LIANG Jun, ZHAO Lei, ZHAO Yanfen
    2013, 33(10): 815-821.
    Abstract ( )   Knowledge map   Save
    Mechanical properties, microstructures and hardness distribution of the dissimilar steel welded joint between martensitic steel T92 and domestic austenite steel S30432 were investigated and compared with those of the dissimilar welded joint between steel T92 and imported steel S30432, while the influence of steel T92 composition on microstructure of the welded joint analyzed. Results show that both the two joints have equivalent mechanical properties, similar hardness distribution, but the peak hardness value in the T92 side fusion zone of the former joint is slightly lower than that of the latter joint. Furthermore, block ferrite bands can be observed in the steel T92 side fusion zone, and the Creq variation of the steel T92 affects the content and size of the formed ferrite blocks.
  • Material Science
    Experimental Study on Microstructure and Mechanical Properties of HR3C Tubes After Internal Pressure Creep Test
    L Yinan, LIU Shutao, ZHANG Hongjun
    2013, 33(10): 822-828.
    Abstract ( )   Knowledge map   Save
    Experimental studies were carried out on microstructure and mechanical properties of HR3C tubes after creep test at different internal pressures and time duration. Results show that dispersed NbCrN phases precipitate both within grains and on grain boundaries after internal pressure creep test; M23C6 carbides precipitate as a continuous chain on grain boundaries, which get coarsening with the increase of time duration; simultaneously, M23C6 carbides precipitate as square particles within grains and in the form of lath-like phases on twin boundaries. The strength and hardness of HR3C tubes increase obviously after internal pressure creep test due to grain-boundary strengthening and dispersion strengthening from disperse phase precipitation of NbCrN and M23C6, and by continuously distributed M23C6 on grain boundaries, however, with the rise of time duration, M23C6 carbides on grain boundaries get coarsening, which result in a decrease of grain boundary strengthening, thus leading to a slight decrease of the tensile strength. Obvious decrease of both the room-temperature impact absorbing energy and the elongation of HR3C steel is resulted from the M23C6 carbides continuously precipitated on grain boundaries after internal pressure creep test.