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    Boiler Technology
  • Boiler Technology
    Sensitivity Analysis of Carbon Emission from Coal-fired Power Plant to Variation of Controllable Operating Parameters
    GAO Jianqiang, SONG Tongtong, ZHANG Qiaobo, CAO Hao
    2020, 40(7): 517-522. https://doi.org/10.19805/j.cnki.jcspe.2020.07.001
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    To find effective measures to reduce the carbon emission from coal-fired power plants from the point of view of controllable operating parameters, a calculation model was established for the sensitivity of carbon emission intensity to the main controllable operating parameters based on CO2 production coefficient of unit standard coal consumption K and combined with energy-loss analysis, so as to analyze the effects of following factors on the carbon emission intensity, such as the temperature and pressure of the superheated and reheated steam, and the exhaust temperature of the boiler, etc. The model was then applied to the analysis of carbon emission reduction for a 330 MW coal-fired unit under stable working conditions respectively at 60% load, 75% load and 90% load. Results show that the carbon sensitivity of controllable operating parameters in the boiler system is higher than that in the steam turbine system. Under high load conditions, the carbon emission intensity is highly sensitive to the exhaust temperature, exhaust gas oxygen content and fly ash carbon content, and the sensitivity of carbon emission intensity to the superheated steam pressure is higher than to other steam parameters. Under low load conditions, the carbon emission intensity is highly sensitive to the auxiliary power consumption, which therefore has great potential in the reduction of carbon emission.
  • Boiler Technology
    Dynamic Model for Soft Sensing of NOx Generation in Coal-fired Units
    ZHAO Zheng, LI Yuening, YUAN Hong
    2020, 40(7): 523-529. https://doi.org/10.19805/j.cnki.jcspe.2020.07.002
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    To solve the problems of low prediction accuracy and time delay produced by static model for soft sensing of NOx generation, dynamic models were suggested. First, the k-nearest neighbor mutual information method was used to determine the auxiliary variable delay, and subsequently the genetic algorithm and mutual information were used to select the order of auxiliary variables. A new input variable set, covering independent variable delay and order information, was then used to construct the dynamic LSSVM soft sensing models respectively based on mutual information and genetic algorithm. The prediction results of above two dynamic models for NOx generation were finally compared with that of the static model. Results show that compared with the static model, the two dynamic models for soft sensing of NOx generation has higher prediction accuracy, with advanced function in prediction to some extent.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Maintenance Interval Optimization Based on Design Life of Steam Turbines
    SHI Jinyuan
    2020, 40(7): 530-539. https://doi.org/10.19805/j.cnki.jcspe.2020.07.003
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    A proposal was suggested for maintenance interval optimization of steam turbines based on the design life, while an introduction was presented to the statistical results of utilization hours for domestic thermal power units, the calculation methods for common equivalent operating hours, the maintenance interval of steam turbines obtained based on the first equivalent operating hours, the calculation methods for start weight coefficients and load change weight coefficients of steam turbines based on the design of fatigue and creep life, the calculation methods for the second equivalent operating hours, the optimization methods for the maintenance interval, the calculation methods for annual average life expenditure of steam turbines and the calculation methods for annual average grade maintenance cost of a unit, together with application examples of a 1 000 MW ultra-supercritical steam turbine and a 600 MW supercritical steam turbine. Results show that compared with the two standards in China Power Industry, the number of years for class A maintenance interval of steam turbines optimized based on the design life is larger, with less average annual life expenditure of the steam turbine and lower average annual grade maintenance cost of the unit. This may serve as a reference for safety and economic operation of power plant steam turbines.
  • Steam Turbine and Gas Turbine
    Design Method for Transition Pieces in Gas Turbine Combustors Based on Multi-modeling Function Combination
    GENG Junjie, QI Haiying
    2020, 40(7): 540-548. https://doi.org/10.19805/j.cnki.jcspe.2020.07.004
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    An aerodynamic modeling design was proposed for the transition pieces (TPs) in gas turbine combustors based on multi-modeling function combination, with focus on design principles, technical routes and design steps including coordinate system settings, import and export contour discretization, etc. Three typical designs of TPs were given, of which their center lines were respectively in the shape of SS, SU and concave. For two special cases of TPs respectively with small fan radius of outlet ring and with large center angle, an improved design method was put forward, together with design examples. Results show that via the method proposed, a veriety of gemetric shapes could be designed for smooth transition from the inlet circular to the outlet ring fan, which adapts to a wide range of aerodynamic design, and could be used as an important means in designing the TPs.
    • Turbo-Generator
  • Turbo-Generator
    Analysis on Sealing Bush Caused Unstable Vibration in a Turbo-Generator Set
    ZHANG Wentao, XIA Yalei, LI Yong, YANG Jiangang, FANG Lintie
    2020, 40(7): 549-555. https://doi.org/10.19805/j.cnki.jcspe.2020.07.005
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    To analyze the mechanism of periodic vibration fault in a large capacity generator, a force analysis model was established using Reynolds equation for the single-flow sealing bush, so as to study the influence of hydrogen pressure on the working status of the sealing bush. Considering the thermal effect of oil flow in the bearing, a model of oil film was established to solve the temperature distribution. Results show that the temperature rise of oil film increases in the case of large eccentricity, high viscosity and small bearing clearance. Under the forward synchronous whirl of journal, thermal bending of generator shaft would occur due to the temperature difference existing on the cross section of the journal. Through variable oil temperature tests, the reason of the generator vibration fault has been found, and the problem has been finally solved by reducing the synchronous whirl caused by the journal shake and imbalance, and by properly increasing the sealing clearance.
    • Monitoring and Measurement
  • Monitoring and Measurement
    Research on Nonlinear Dynamics of a Rotor Based on Full Spectrum Analysis
    XIANG Ling, YANG Yang, ZHANG Yue, AN Chaohui, YE Feng
    2020, 40(7): 556-563. https://doi.org/10.19805/j.cnki.jcspe.2020.07.006
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    To study the precession of a faulty rotor system with rigid support, a nonlinear dynamic model was established for the rotor system to simulate the precession signals of the rotor system respectively with crack fault, rub-impact fault and crack rub-impact compound fault, so as to investigate the changing laws and characteristics based on full spectrum analysis. The full spectrum of the rotor system was experimentally verified under crack rub-impact compound faults on a Bently rotor test-bed. Results show that the full spectrum not only reflects the change of the rotor vibration amplitude, but also contains the information of the rotor precession direction. High-frequency components of -nX(n=1,2,3…) appear in the response of the rotor under rub-impact fault and crack rub-impact compound fault. When the speed ratio is 0.55, the amplitude of the -2X component is higher than that of the 2X component, showing second-order anti-precession characteristics. The nonlinear characteristics of the rotor system with rub-impact fault and crack rub-impact compound fault are more complex at high speeds, when ±1/2X components appear in the full spectrum, and the rotor system keeps in the motion of period 2.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Numerical Simulation of Gas-Solid Two-phase Flow Based on MFIX
    YANG Jianmeng, LI Bin, WANG Hongyuan, HOU Dangyuan
    2020, 40(7): 564-570. https://doi.org/10.19805/j.cnki.jcspe.2020.07.007
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    Based on the open source program MFIX, a three-dimensional model was established for the gas-solid two-phase flow in a spouted bed, and subsequently numerical simulations were conducted for the source program with different drag models using MFIX-DEM method to obtain the flow characteristics of particles in the three-dimensional spouted bed. At the same time, the flow characteristics of particles in the spouted bed were analyzed within 0.2-2.0 s through experiments. Results show that the numerical simulations agree well with the experiments. The bed height of Gidaspow model is close to the experimental results, but the fluctuation range of the bed height of Gidaspow model is larger, while that of Syamlal-O'Brien model is relatively close to the experimental results. The dead area of model B is smaller than model A under two drag models, and the flow ability in model B is stronger. As time goes on, there will be an extreme point of bed height, before and after this point, the bed height fluctuates greatly; the extreme point of bed height in model B is higher than in model A, and the time point when the extreme value appears in Syamlal-O'Brien model is later than in Gidaspow model.
  • Engineering Thermophysics
    Flickering Characteristics and Nonlinear Analysis of Non-premixed Coaxial Jet Flames
    PAN Wenxuan, YANG Mo
    2020, 40(7): 571-579. https://doi.org/10.19805/j.cnki.jcspe.2020.07.008
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    Taking the coaxial jet burner as an object of study, numerical simulations were conducted on the coaxial methane-air diffusion flame under the nozzle diameters of 6 mm, 11.4 mm and 17.4 mm, respectively, so as to analyze the flickering characteristics of the diffusion flames with the oxygen concentration in 23%-48%. Results show that the optimum co-flow ratio Ur, under which the flame could be stabilized, increases with rising diameter of the burner, and the corresponding Ur values for the three burner diameters to suppress flame oscillation are 0.647, 2.2 and 11.4 respectively. The vortex surrounding the flame moves downward gradually with the increase of the Ur, when the peak flickering frequency rises, and the amplitude of flame oscillation reduces, while the flow and heat transfer change from periodic oscillation to chaos state. The amplitude of diffusion flame decreases as the oxygen concentration increases, and when the oxygen mass fraction is 48%, the peak frequency is 10 Hz, which does not change with the mass fraction of oxygen.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Theoretical Analysis and Application of a Denitration Technology over the Whole Load Range
    XU Jiaye, ZHU Xiaolei, LI Jianning, CHONG Peian, DING Shifa
    2020, 40(7): 580-585. https://doi.org/10.19805/j.cnki.jcspe.2020.07.009
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    To achieve the purpose of ultra-low emission from a 600 MW coal-fired power unit, a hot water recirculation system was added to the boiler economizer, while the steam from adjacent boiler was used to heat the local feed water via an extraction line for the No.2 high-pressure heater. Results show that under the condition of 30% BMCR, when the recirculation rate of working medium is 900 t/h, the outlet gas temperature of the economizer may reach 309.10 ℃, with an increase of 30.80 K, satisfying the temperature requirement by denitration operation. During the start-up process, when the steam from adjacent boiler is used, the local feed water could be heated from 154.22 ℃ to 194.53 ℃, when the outlet gas temperature of the economizer may reach 301.77 ℃, also satisfying the temperature requirement by denitration operation.
  • Environmental Protection Technology and Equipment
    Characteristic Research on Simultaneous Removal of SO2 and NOx by Combining Ozone Preoxidation with Ammonia Absorption Based on Spray-and-Scattered-Bubble Technology
    LIU Ruiqi, SI Tong, WANG Chunbo, XU Ziyang, REN Yujie, HU Jian
    2020, 40(7): 586-592. https://doi.org/10.19805/j.cnki.jcspe.2020.07.010
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    Experimental tests were conducted on the simultaneous removal of SO2 and NOx by combining ozone preoxidation with ammonia absorption based on spray-and-scattered-bubble technology, so as to analyze the effects of following factors on the desulfurization and denitration efficiency, such as the O3/NO molar ratio, SO2 concentration, NO concentration, liquid-gas ratio and immersion depth, etc., and to build a calculation model for the mass transfer area. Results show that the denitrification efficiency can be obviously improved by increasing the molar ratio of O3/NO. The increase in SO2 concentration will promote the absorption of NO2. With the increase of liquid-gas ratio and immersion depth, both the desulfurization efficiency and denitrification efficiency would be improved due to the extended total mass transfer area. When the molar ratio of O3/NO is 1, the liquid-gas ratio is 6 L/m3, the immersion depth is 50 mm, and the ammonia water mass fraction is 0.06%, the desulfurization efficiency and denitrification efficiency using spray scattering technology would respectively reach 99% and 82%, higher than that using single spray technology and single bubble technology under the same parameters.
    • Nuclear Technology
  • Nuclear Technology
    Characteristic Study of a Nuclear Reactor Coolant Pump During Power-off Idling Process
    YE Daoxing, LAI Xide, WEN Haigang, SHENG Xiaoyu, ZUO Lingyu
    2020, 40(7): 593-599. https://doi.org/10.19805/j.cnki.jcspe.2020.07.011
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    To analyze the performance variation of a nuclear reactor coolant pump during idling period, a mathematical model was established based on the relationship of flowrate and speed with idling time, following which, numerical calculation and dimensionless analysis were conducted to study the performance of the pump impeller. Results show that the flow rate reduces rapidly along with the time, which drops to 6.5% at 220 s. For the chord length of 0.1, the difference of pressure ratio between pressure surface and suction surface of blade reduces with idling time, while the pressure ratio increases with idling time at the inlet of blade, which drops suddenly at the outlet near pressure surface. For the chord length of 0.5, at the outlet of blade, both the pressure ratio and speed ratio oscillates twice. For the chord length of 0.9, the pressure ratio and speed ratio both oscillate once, when the difference of pressure ratio and speed ratio between pressure surface and suction reduces with idling time. The pressure ratio and speed ratio change periodically in circumferential direction. As the idling time rises, the pressure ratio increases while the speed ratio decreases with both reducing amplitude.
  • Nuclear Technology
    Economic Analysis of the Thermal Power System in the Secondary Circuit of a Nuclear Power Plant Based on Energy Level Decoupling
    YAN Shuibao, QIAN Yibo, QI Jipeng, FENG Can
    2020, 40(7): 600-604. https://doi.org/10.19805/j.cnki.jcspe.2020.07.012
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    According to the energy level theory of thermal systems, the thermal system in the secondary circuit of a nuclear power plant was considered to have a coupling relationship between the thermal system of the primary reheating unit and its internal energy level. Through decoupling analysis, the variation law of the efficiency of the secondary circuit thermal system with the structure of the system itself was taken into account. Without increasing the complexity of the energy saving theory, a quantitative relationship between the efficiency of the secondary circuit thermal system and the structure of the system itself was obtained, and the correctness of the algorithm was finally verified with a numerical example. Results show that in the secondary circuit thermal system of a nuclear power plant, the separator can not only improve the safety, but also significantly improve the thermal economy of the thermal system.