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  • 2022 Volume 42 Issue 1
    Published: 15 January 2022
      
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  • A Review on Supercritical Carbon Dioxide Brayton Cycle
    JI Yuxuan, XING Kaixiang, CEN Kefa, NI Mingjiang, XIAO Gang
    2022, 42(1): 1-9. https://doi.org/10.19805/j.cnki.jcspe.2022.01.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Supercritical carbon dioxide Brayton cycle has the advantages of high efficiency (50%), compact structure, low compression power and great potential for cost reduction. It can be combined with various forms of heat sources such as fossil energy, nuclear energy and solar energy, which has broad development prospects. From the perspective of key components and systems, the domestic and foreign research progress in supercritical carbon dioxide Brayton cycle were reviewed, including heat source heating, power circulation, regenerative equipment, cooling equipment and design optimization, then the experimental test results, system demonstrations and technical bottlenecks of supercritical carbon dioxide of key components were analyzed. Finally, the future research, system demonstration and application trends were forecasted.
  • An Overview of the Integrated Energy Systems' Development Under the Background of Carbon Neutralization
    LU Wanglin, LU Qiliang, ZHANG Zhihong
    2022, 42(1): 10-18. https://doi.org/10.19805/j.cnki.jcspe.2022.01.002
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    In order to analyze the future development trend of the integrated energy systems (IES) under the background of carbon neutralization, domestic and international development status of IES was introduced, the connotation and technical framework of IES were discussed. The key technologies of IES were summarized into five aspects, such as energy production, energy transmission, energy storage, energy consumption and energy intelligent technology. Then the development status and core problems of each technology were analyzed. The suggestions to strengthen the overall planning of IES, to promote the localization of key technologies and equipments, to promote the improvement of IES market, and to develop energy services from the user side were proposed.
  • Release Characteristics of Mercury and Sulfur During Coal Pyrolysis
    SU Yinjiao, TENG Yang, ZHANG Kai, SU Xinxin
    2022, 42(1): 19-26. https://doi.org/10.19805/j.cnki.jcspe.2022.01.003
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    By means of thermal analysis and kinetic analysis method, the raw coal and its washing products from a coal washing plant in Ningwu coalfield were selected as the research object, so as to investigate the release characteristics of mercury and sulfur during coal pyrolysis. Results show that the release of mercury and sulfur is related to the composition of coal, and the release ratio of mercury and sulfur in slime and clean coal is higher than that of gangue and raw coal at the same pyrolysis conditions. The release characteristics of mercury and sulfur are affected by their occurrence forms. Mercury and sulfur in coal mainly exist as inorganic bound state, while mercury in clean coal and slime is more likely to release at low temperature. The release ratio of mercury and sulfur increases with the rise of temperature, the bonding degree of mercury with its occurrence form is weaker than that of sulfur. Thus, the removal efficiency of mercury is more than 50% at the temperture of 500 ℃, while the removal efficiency of sulfur is only about 20% at the temperture of 800 ℃. Reaction time has limited effect on release ratio of mercury and sulfur in coal. The reaction activation energy released by mercury during pyrolysis is lower than that of sulfur, indicating that the experimental results of thermal analysis are consistent with the kinetic inference.
  • Numerical Simulation and Improvement of the Flow Field of a Steam Turbine Compensation Valve
    HE Zhengliang, ZHANG Xue, ZHAO Hongyu, LIU Yunfeng, WANG Jian, MA Tianyin, HUANG Diangui
    2022, 42(1): 27-33. https://doi.org/10.19805/j.cnki.jcspe.2022.01.004
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    Flow field of a steam turbine compensation valve was calculated by numerical simulation method. The internal flow field structure and wall pressure fluctuation under different valve opening were compared and analyzed, and flow characteristics were ameliorated by improving the valve structure. Results show that under medium and large valve opening, the steam pressure of the flow field changes significantly and periodically, and the frequency component of the pressure fluctuation is very complicated. After structural improvement, the vortex area decreases and the amplitude of pressure fluctuation reduces significantly, meanwhile the flow stability is improved, the pressure loss is reduced and the valve flow capacity is increased, which provides a reference for the design and modification of the compensation valve.
  • Numerical Study on Depressing Secondary Flow Loss of Cascade by Pulse Jet
    ZHAO Shu, CHEN Liu, DAI Ren
    2022, 42(1): 34-42. https://doi.org/10.19805/j.cnki.jcspe.2022.01.005
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    Jet holes were set at the front wall of the cascade, square wave function and sinusoidal function jet were introduced. The effects of the duty ratio of square wave function jet and the mean momentum coefficient, amplitude, frequency of sinusoidal function jet on the secondary flow loss were analyzed by numerical simulation. Results show that when the duty ratio of the square wave function jet is 0.6, the total pressure loss of the square wave jet function can keep effect similar to steady jet, and the mass flow of the required jet is only 60% of the steady jet. When the amplitude of sinusoidal jet is 0.2, the frequency is 0.5 and the time-average momentum coefficient is 0.05%, the best flow control effect of steady jet can be achieved approximately by sinusoidal function jet, and the total mass flow of the jet required is only 70.7% of the steady jet.
  • Research on Intelligent Fault Diagnosis of Rolling Bearings Under Variable Conditions Based on CAE and CNN
    ZHOU Wenxuan, LIU Yang, DENG Minqiang, DING Xue, DEND Aidong
    2022, 42(1): 43-48. https://doi.org/10.19805/j.cnki.jcspe.2022.01.006
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    To evaluate the state of rolling bearings under variable conditions, an intelligent fault diagnosis method based on convolutional neural networks (CNN) and convolutional auto-encoders (CAE) was proposed. Firstly, the labeled data under a single condition and the unlabeled data under variable conditions were inputted into the CAE encoder to obtain the features matrix F. Then F from the data under a single condition was inputted into CNN bearings fault diagnosis model to obtain the state type and calculate the loss, while F from all data was inputted into the CAE decoder to obtain the reconstructed data and calculate the loss. The sum of these two parts of loss was used as the total loss for back propagation training. Finally, the data under variable conditions were inputted into the CAE encoder and CNN bearing fault diagnosis model to get the state type. Results show that the CAE encoder makes F distribution of the data under variable conditions closer and the proposed method can achieve a test accuracy over 97%, which is promising in intelligent fault diagnosis of rolling bearings.
  • Heterogeneous Nucleation Behavior of Fine Particles from Ammonia-based Desulfurization System
    GUO Yang, FAN Fengxian, ZHANG Chao, ZHAO Qingjie
    2022, 42(1): 49-55. https://doi.org/10.19805/j.cnki.jcspe.2022.01.007
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    In order to meet the demand of ultra-low emission of fine particles from coal-fired power plants, combined with the processes of ammonia-based desulfurization and characteristics of fine particles emitted, the theoretical model of vapor heterogeneous nucleation on the surface of a fine particle containing spherical insoluble core and soluble components was developed by considering the nucleation mechanisms of direct deposition and surface diffusion. The heterogeneous nucleation characteristics of fine particles were numerically investigated. Results show that when the soluble components are ammonia sulfate and ammonia bisulfate, the critical free energy of embryo formation and critical embryo radius increase with the increase in mass fraction of ammonia sulfate. The critical embryo radius decreases with the increase of the radius of spherical insoluble core, which largely differs from the nucelation of insoluble particles. With the increase of the mass fraction of ammonia sulfate, the nucleation rate decreases and the critical nulceation saturation ratio increases. In addition, when the radius of insoluble core is below 0.1 μm, the critical nulceation saturation ratio decreases rapidly with the core radius, whereas when the radius of insoluble core is above 0.1 μm, the critical nucleation saturation ratio is not sensitive to the core radius.
  • Experimental Study on the Effects of High Brine Reuse in Desulphurization System on Desulfurization Performance
    MA Shuangchen, LI Yang, GU Tao, GONG Chunqin, HE Chuan, FAN Shuaijun, XU Fang
    2022, 42(1): 56-66. https://doi.org/10.19805/j.cnki.jcspe.2022.01.008
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    According to the reuse problem of high salt wastewater from zero discharge of desulfurization wastewater, a small-scale experimental platform was built to investigate the effects of reuse of high salt wastewater in the desulfurization system on its desulfurization performance, such as desulfurization efficiency, gypsum quality, slurry viscosity and limestone activity. Results show that in desulfurization efficiency experiments, the limestone slurry with salt added can improve the buffering performance of acid gas SO2, and the pH fluctuation range is smaller, which improves the desulfurization efficiency; the sodium salt can promote the SO2 absorption and mass transfer effect at the same concentration, especially for the divalent sodium salt Na2SO4; the gypsum crystals with single salt addition have a better crystal morphology and quality than those without salt addition; from the perspective of the salt viscosity affecting the gas-liquid mass transfer, magnesium salt has a significant impact, so the magnesium salt concentration should be controlled below 1 mol/L; NaCl in slurry can promote the dissolution of limestone, while MgCl2 and CaCl2 have an inhibitory effect. Different salinities have different effects on limestone dissociation.
  • Salt Precipitation Behaviors of Classification and Concentration Process for Desulfurization Wastewater in Coal-fired Power Stations
    ZHAGN Juan, CAO Zhaojun, SHI Haihong, LIU Deyu, SUN Hao, ZHAO Liang, ZHAO Yun, CHANG Jingyu
    2022, 42(1): 67-74. https://doi.org/10.19805/j.cnki.jcspe.2022.01.009
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    To reveal the salt precipitation behaviors of limestone gypsum desulfurization wastewater in the forced evaporation process, the desulfurization wastewater of several power plants in China was divided into three typical systems: sulfate sodium chloride subtype, magnesium sulfate subtype and chloride sodium chloride subtype. Three typical wastewater types were forced to evaporate under simulated atmospheric pressure (101.3 kPa) and negative pressure (50 kPa), obtaining the behaviors of liquid density, boiling point raising, liquid composition and solid salt precipitated during evaporation process. Results show that the order of the main precipitates in sulfate wastewater evaporation is calcium sulfate, magnesium sulfate and sodium chloride, while the order of the main precipitates in chloride wastewater evaporation is calcium sulfate and sodium chloride. When the evaporation loss rate is less than 80%, the main precipitate in the wastewater evaporation process is calcium sulfate. When the evaporation loss rate is more than 80%, a large amount of sodium chloride can be precipitated. Sulfate type magnesium sulfate subtype is more difficult to precipitate sodium chloride than chloride subtype.
  • Modeling of Multi-cogeneration Unit and Analysis of Thermoelectric Dynamic Coupling Characteristics
    TIAN Liang, FENG Rongrong
    2022, 42(1): 75-82. https://doi.org/10.19805/j.cnki.jcspe.2022.01.010
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    In order to solve the problems that multi-cogeneration units were difficult to control due to strong coupling between power generation and heating/steam supply loads, large inertia and large delay of objects, time-varying nonlinearity of the system and other complex characteristics, the energy balance differential equations of each main dynamic link of a 300 MW unit were established through the mechanism analysis method, and the model parameters were determined by using the design and operation data, then the dynamic model suitable for full load condition was established. By putting the actual input signals of unit into the model and comparing the curve error between the model output and the actual output, the accuracy of the model was verified. The simulation experiment of control input disturbance and the linearization method of operation point were used to analyze the structure characteristics of the model, the coupling characteristics of power generation, heating and steam supply, and the nonlinear variation law under different operation conditions. Results show that the object coupling characteristic is mainly reflected in the tee coupling on the exhaust side of the intermediate pressure cylinder, and the nonlinearity is mainly reflected in the characteristic that static gain from the input to the output changes significantly with different operation points.
  • Study on Capacity Configuration and Operation of Hybrid CCHP System
    DU Chuanming, CHEN Mengshi, DU Shangbin, HU Yongfeng, ZHAO Yijun
    2022, 42(1): 83-93. https://doi.org/10.19805/j.cnki.jcspe.2022.01.011
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    Taking a commercial complex as the research object, a Hybrid CCHP system was constructed according to the load demand of cooling, heating and transition season in the park. Comprehensive evaluation indexes were established from the aspects of energy, economy and environment. The capacity configuration of the driving equipment of the system was optimized by genetic algorithm, so as to compare the primary energy saving rate, annual operation cost saving rate and CO2 emission reduction rate of the system under the conditions of following the thermal load (FTL) and following the electric load (FEL), with and without solar complementary, as well as with and without energy storage. Results show that the performance of the Hybrid CCHP system optimized by genetic algorithm is significantly better than that of CCHP system. The stepped energy release mode can further improve the economy of the Hybrid CCHP system.
  • Research Progress on Acceleration Effect and Criteria of Supercritical Fluid Flow
    HUANG Yu, DUAN Lunbo
    2022, 42(1): 94-100. https://doi.org/10.19805/j.cnki.jcspe.2022.01.012
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    In order to explain the heat transfer deterioration essentially, the current research progress of flow acceleration effect and criteria of supercritical fluid flow were reviewed. Firstly, the flow acceleration criteria and its threshold used in straight tubes were summarized, and the problems existing in the flow acceleration criteria were discussed when analyzing heat transfer characteristics, so as to explore the flow acceleration effect in complex tubes. At present, there is no consensus on the selection of flow acceleration criteria and threshold, and the current flow acceleration criteria could not be directly applied to complex tubes. The existence of U-bend elbow would inhibit the influence of flow acceleration effect on heat transfer, while the flow acceleration criteria derived from straight pipe theory cannot reflect the phenomenon.