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    Boiler Technology
  • Boiler Technology
    Test Study on Combustion Adjustment for 1 000 MW Ultra Supercritical Boilers
    GAO Ji-lu, ZOU Tian-shu, LENG Jie, WU Jing-xing, LIU Xue-zeng
    2012, 32(10): 741-746.
    Abstract ( )   Knowledge map   Save
    Experiments on combustion optimization and adjustment of a 1 000 MW power boiler were carried out, so as to analyze the influence of following factors on the boiler efficiency, such as the primary air distribution, fineness of pulverized coal, air distribution of burner, oxygen volumetric fraction and over-fire air rate, etc. Results show that for the same layer of burners, the deviation of oxygen volumetric fraction distribution along breadth of furnace caused by wind inlet through both ends of big bellows can be improved by increasing the opening of distribution plates at both ends and middle positions for external secondary air. With the rise of oxygen volumetric fraction, the boiler heat efficiency increases first and reduces later on, which reaches the highest at an oxygen volumetric fraction of 3.0%. With the reduction of over-fire air rate, both the boiler heat efficiency and mass concentration of NOx emission rise gradually. Comprehensively considering the boiler efficiency, NOx emission and metal temperature of platen superheater tubes, it is recommended that the over-fire air rate be kept at about 25% at rated load, when the boiler heat efficiency may reach 93.9%, with a mass concentration of NOx emission at 306.1 mg/m3.
  • Boiler Technology
    Stress Soft-sensing Model for Steam-Water Separator of Ultra Supercritical Boilers Based on Elman Neural Network
    LI Na, YAN Wei-ping, MA Liang-yu
    2012, 32(10): 747-752.
    Abstract ( )   Knowledge map   Save
    Based on structural features of steam-water separator for ultra supercritical boilers, a 3D finite element model was established for thermal analysis purpose, with which the total stress field was simulated during start-up of a 1 000 MW unit. Combining the finite element method with neural network algorithm, a dynamic stress soft-sensing model was set up based on Elman neural network, by taking both the medium pressure and wall temperature series as auxiliary variables, and the finite element calculation results as training samples, of which the structure was subsequently determined after model training. The soft-sensing model was finally verified with actual operating and monitoring data of the power unit. Results show that the model calculation results can well approach that of finite element analysis. Featured by high precision and good real-time performance, the model may serve as a reference for on-line life monitoring of power plant boilers.
  • Boiler Technology
    Study on Superheater Temperature Unbalance and Relevant Piping Arrangement for a Tangential Firing Boiler
    LUO Qing, CAO Han-ding, JIANG Xiao-feng, LIN Bi-yu, XIONG Xian-wei, WU An
    2012, 32(10): 753-759.
    Abstract ( )   Knowledge map   Save
    To solve the unbalance problems of gas velocity and temperature distribution and the steam temperature deviation of superheater, frequently existing in large tangential firing boilers, an analysis has been performed on actual operation data of a 1 000 MW boiler in Beijiang Power Plant, while a simulation carried out on the in-furnace flow field. Results show that the gas flow fields are different at both sides of screen tubes due to the residual rotation existing in upper part of the furnace, and the steam temperatures near the baffle angle are differently distributed at both sides. By changing the arrangement of pipes between the rear screen superheater and final superheater of boiler (from cross into parallel), the heat absorption deviation between two stages of heating surfaces are offset, which helps to improve the regulation performance of relevant attemperators.
  • Boiler Technology
    Effect of Air Distribution Mode on Solids Circulation Rate in a Circulating Fluidized Bed
    CHEN Hong-wei, YANG Xin, YIN Meng, CHENG Ling
    2012, 32(10): 760-764.
    Abstract ( )   Knowledge map   Save
    Effects of various factors on solids circulation rate in the riser of a CFB were studied on a cold-state test rig respectively with cone and panel type air distributors. Results show that when a cone distributor is used, the minimum complete fluidizing velocity is significantly higher than the minimum fluidizing velocity. The solids circulation rate grows with rising speed of air in both the gasification chamber and the riser, and the growth rate reduces gradually. The air speed and bed material height under cone distributor mode play a more important role in influencing the solids circulation rate than that under panel distributor mode; however, the particle size of bed material acts just in an opposite way.
  • Boiler Technology
    Effects of the Structure of Preheating Chamber on Combustion and NOx Emission of a Multi-stage Self-preheating Burner
    CHEN Dong-lin, CHENG Shan, YUN Ying, DENG Tao
    2012, 32(10): 765-769.
    Abstract ( )   Knowledge map   Save
    An introduction is being presented to the structure of a multi-stage self-preheating burner and its four typical preheating chambers. Through CFD simulation, the flow field, flue gas recirculation rate, temperature field, fuel gas burn-out rate and volumetric fraction of NOx in the combustion chamber have been calculated and analyzed in comparison with that of traditional burners. Results show that compared with traditional burners, the proposed burner has a different flow field and a higher adaptability to fuels of low heating values; the structure of its preheating chamber influences both the flue gas recirculation rate and the preheating effectiveness, and therefore accordingly influences the burn-out rate and NOx emission. Furthermore, the load of the burner affects less on the burn-out rate, but more on NOx emission.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Cause Analysis of Steam-excited Vibration in Steam Turbine Unit
    SONG Guang-xiong, CHEN Song-ping, SONG Jun-hui, LIANG Hui-zhao
    2012, 32(10): 770-778.
    Abstract ( )   Knowledge map   Save
    By analyzing the steam-excited vibration faults occurring in domestic steam turbine unitin recent years, the failures are found to be caused by too large excitation force and poor bearing stability. Main features of the steam-excited vibration are analyzed from the aspects of vibration location, characteristic frequency of low-frequency vibration, amplitude variation of low-frequency vibration, the relationship between vibration and operation parameters, and other related factors, etc. Based on above analysis, relevant fault diagnosis criteria are proposed, while corresponding countermeasures suggested, such as reducing the steam exciting force and improving the bearing stability, etc., which may serve as a reference for safe operation of steam turbine unit.
  • Steam Turbine and Gas Turbine
    Influence of Water Marbles on Efficiency, Blade Fracture and Water Erosion of Steam Turbines
    GAO De-wei
    2012, 32(10): 779-785.
    Abstract ( )   Knowledge map   Save
    By analyzing the status of blade fracture and water erosion occurring in an extraction condensing turbine unit, the failure is found to be caused mainly by the braking force from water marbles, which inhibits the rotation of the rotor, and therefore directly affects the efficiency of the steam turbine. The formation mechanism of secondary water droplets from water marbles is compared with that from water films at blade trailing edge torn and broken by high-speed steam flows. It is pointed out that the number of water marbles can be effectively decreased by changing the structure of corresponding baffle plates, so as to reduce the mentioned braking force, economize the energy consumption, and therefore elongate the blade life and raise the unit efficiency.
  • Steam Turbine and Gas Turbine
    Comprehensive Test-rig for Rotor-Bearing System of Heavy-duty Gas Turbines
    XU Zi-li, ZHAO Shi-quan, WANG Jian-lu, WANG Wei-min, WANG Tie-jun, YU Lie
    2012, 32(10): 786-791.
    Abstract ( )   Knowledge map   Save
    An introduction is being presented to a domestic comprehensive test-rig for rotor-bearing system of heavy-duty gas turbines, with which a field shafting vibration test has been carried out to a gas-steam combined cycle power generation unit. Results show that throughout the start-up, shut-down and operation period at rated speed of the gas turbine, the rotor-bearing system can operate stably, which is proved to be reasonably designed with good performance of dynamic balancing of rotor. The test-rig may serve as a reference for design and development of rotor-bearing system for domestic heavy-duty gas turbines.
    • Automatical Controlling and Detecting Diagnosis
  • Automatical Controlling and Detecting Diagnosis
    Study on Terminal Sliding Mode Control for Boiler-Turbine Unit Based on RBF-NN Inverse System
    WU Zhong-qiang, XIAO Xue-fei
    2012, 32(10): 792-797.
    Abstract ( )   Knowledge map   Save
    Aiming at the features of boiler-turbine unit, such as multiple inputs, multiple outputs, nonlinearity and strong coupling etc., an inverse system method is used to achieve feedback linearization and decoupling of the unit, during which the inverse system is identified using radial basis function (RBF) neural network, while the modeling errors reduced through online learning. A terminal sliding mode controller is designed for the unit to reach finite time convergence, and its global stability is analyzed and guaranteed using Lyapunov approach. Simulation results show that the control system works well within a wide range of operation conditions, which is superior to the system designed based on classical inverse system method.
  • Automatical Controlling and Detecting Diagnosis
    Fuzzy Identification of MIMO Thermal Process Based on Adaptive Competitive Clustering
    HAO Wan-jun, QIAO Yan-hui, GUAN Shang-jun, LI Ze
    2012, 32(10): 798-803.
    Abstract ( )   Knowledge map   Save
    Considering the nonlinear, strong coupling, parameters time-varying characteristics and variable work conditions of multi input multi output(MIMO) thermal process, a new model identification method is proposed based on input-output data of the system and fuzzy adaptive competitive clustering, with which the input-output data are firstly clustered according to typical work conditions, while the T-S model structure identified so as to determine the antecedent parameters of the system; then, the consequent parameters of the fuzzy rules are identified using recursive least squares, while the antecedent parameters modified exactly. Application results on the nonlinear model of a boiler-turbine unit prove the model identification method to be effective.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Calculation and Analysis of the Chemical Exergy Based on High Heating Values of Fuel
    WANG Ji-xuan, WU Zhi-quan, HAN Zhong-he, LIU Xiao-zhen, QIAN Jiang-bo
    2012, 32(10): 804-808.
    Abstract ( )   Knowledge map   Save
    Taking the actual reaction process of fossil fuel as an object of study, a calculation formula of chemical exergy was derived for fuels containing a number of elements, such as C, H, O, N, S, etc., based on actual combustion process models and high heating values. With the formula, chemical exergy of some domestic coals was calculated and compared with that of overseas calculation results based on models for pure substance. Results show that the calculated values of chemical exergy obtained by the newly derived formula based on high heating values agree well with that of other researchers.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Antifreezing Performance Monitoring of Direct Air-cooled Condenser Based on Fuzzy Analytic Hierarchy Process
    ZHANG Xue-lei, ZHOU Lan-xin, CHEN Hai-ping, ZHU Hai-xia
    2012, 32(10): 809-814.
    Abstract ( )   Knowledge map   Save
    Taking a certain 300 MW direct air-cooled unit as an example, factors influencing the antifreezing performance of the air-cooled condenser were analyzed, during which a monitoring model for the antifreezing performance was built up based on fuzzy analytic hierarchy process. Results show that the temperature deviation between condensation water and pumping air has greater impact on antifreezing performance than other factors, and the antifreezing performance of cooling tubes at rows two and five is relatively poor. The model established based on fuzzy analytic hierarchy process may not only help to quantitatively evaluate the antifreezing performance, but also narrow the scope to find the point of failure, which may therefore serve as a reference for freezing failure prevention, trouble shooting and operation optimization of similar power units.
  • Auxiliary Equipment Technology
    Prediction Model of Condenser Vacuum Degree Based on Particle Swarm Optimization Algorithm
    WANG Jian-guo, MENG Na, YIN Xin
    2012, 32(10): 815-819.
    Abstract ( )   Knowledge map   Save
    Combining the principal component analysis with BP neural network algorithm based on particle swarm optimization, a condenser vacuum prediction model has been proposed on the basis of heat-transfer analysis of the condenser, operation data collected by DCS of a 660 MW unit, and the partial correlation coefficient obtained by multiple regression analysis of main factors influencing the condensor vacuum. By comparing the measured and predicted value of condenser vacuum, the real-time rationality of condenser vacuum can be estimated, and thus soft-sensing can be realized for condenser operation conditions. The prediction model may serve as a theoretical basis for fault diagnosis of condenser, and therefore help to raise the opeation efficiency, reliability and safety of power units.
    • Energy System Engineering
  • Energy System Engineering
    Reliability Grade Evaluation of Power Plant Based on Projection Pursuit Principle
    FU Zhong-guang, JING Yuan, QI Min-fang, WANG Jian-xing
    2012, 32(10): 820-824.
    Abstract ( )   Knowledge map   Save
    Taking the competition data of domestic large thermal power plants in 2010 as a sample set, a model for reliability evaluation of 600 MW supercritical power units was built up based on projection pursuit principle and genetic algorithm, with which a comparison was made between the evaluation results and relevant competition data. Results show that the evaluation results based on the newly built model agree well with the competition data. Overcoming the deficiency of artificial factors, the model has features of strong objectivity, high precision, great effectiveness and facile operation.