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    Boiler Technology
  • Boiler Technology
    Hot-state Experiment on Co-combustion of Semi-char and Bituminous Coal Under Different Primary Air Bias Concentration Ratios
    CHEN Dengke, PENG Zhengkang, YAN Yonghong, SUN Liutao, SUN Rui
    2020, 40(8): 605-613. https://doi.org/10.19805/j.cnki.jcspe.2020.08.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    Hot-state experiments were conducted to investigate the influence of the change of bias concentration ratio of pulverized coal at primary air outlet on the ignition properties of primary air-coal mixtures in a 350 kW pilot-scale furnace. The furnace temperature at different axial and radial positions, and the concentrations of gaseous species O2, CO and NOx were measured in the primary combustion zone to study the effects of bias concentration ratio on pulverized coal ignition, NOx emission and burnout properties for co-combustion of Shenhua bituminous coal and Shenmu pyrolyzed semi-char (with blend ratio of semi-char to bituminous coal of 1:1). Results show that, except for the bias concentration ratio of 1.0 the ignition and combustion properties of the fuel-rich jet are better than the fuel-poor jet; the steady combustion position of coke moves upward in the furnace, while the O2 consumption and flue gas generation mainly concentrate on the fuel-rich side. With the increase of bias concentration ratio, the ignition stand-off distance shortens, the combustion stability in high-temperature region enhances, and the NOx concentration decreases sharply. However, the difference in NOx emission is only 20.27 mg/m3 between the cases with bias concentration ratio of 3.8 and 5.0 respectively, showing very small difference of NOx emission. Therefore it is recommended adopting the bias concentration ratio of 3.8-5.0 for the co-combustion of semi-char and bituminous coal.
    • Automatic Control
  • Automatic Control
    Reheat Steam Temperature Prediction and Control Based on Iterative Learning Algorithm for Ultra-supercritical Units Under Deep Peak Shaving
    QU Xiaofan, Lü Jianhong
    2020, 40(8): 614-620. https://doi.org/10.19805/j.cnki.jcspe.2020.08.002
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    To improve the control performance of the coordinated control system in an ultra-supercritical thermal power unit, a control method was proposed based on iterative learning algorithm, which was used to improve the performance of the predictive controller. Based on the state space predictive model, iterative correction was made using historical errors. Meanwhile, the iterative sequence and time series quadratic terms were introduced into the performance indicators to calculate the optimal control law, thereby ensuring unbiased tracking of set values in case of model mismatch. For a 1 000 MW ultra-supercritical unit, an object model of superheated steam temperature was identified by particle swarm optimization algorithm based on field experimental data, while a simulation experiment was performed. Results show that the method proposed can effectively improve the control quality over superheated steam temperature, which has good resistance and robustness to I/O disturbance and model mismatch caused by wide load variations.
  • Automatic Control
    Control Optimization of an Air Supply System in a Thermal Power Unit Under Deep Flexible Peak Load Regulation
    WANG Yinsong, LIU Meng, LIU Shuang
    2020, 40(8): 621-628. https://doi.org/10.19805/j.cnki.jcspe.2020.08.003
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    To study the factors that affect the operation efficiency of axial-flow fans in a thermal power unit, the energy consumption characteristics of the axial-flow fans were analyzed, while a comparison was carried out on the energy consumption between the operation mode of a single axial-flow fan and two axial-flow fans in parallel arrangement. Based on energy consumption analysis of the axial-flow fans, an optimal design scheme was proposed for the axial-flow fan. Results show that when the unit operates at low load, the independent operation mode with a single axial-flow fan could effectively reduce the energy loss and improve the fan efficiency, compared with the parallel operation mode with two axial-flow fans. For the thermal power unit, it is suggested adopting the operation mode with a single axial-flow fan under low load condition, and adopting the parallel operation mode with two axial-flow fans under medium and high load conditions, and between the two modes, automatic undisturbed switching could be realized through the introduction of command coefficients of the axial-flow fans.
    • Monitoring and Measurement
  • Monitoring and Measurement
    On-line Measurement of CO in Flue Gas Based on WM-DAS Combined with In-situ Sampling
    ZHOU Peili, TAN Wen, PENG Zhimin, DING Yanjun
    2020, 40(8): 629-634. https://doi.org/10.19805/j.cnki.jcspe.2020.08.004
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    Combined with in-situ sampling, the WM-DAS method was used to realize fast on-line measurement of CO volume fraction in flue gas of coal-fired units aiming at its strong fluctuation characteristics. Firstly, the WM-DAS method was theoretically deduced and verified. Then, the corresponding device was installed on the horizontal flue duct at the exit of the economizer in a coal-fired power plant, while the measuring chamber was installed in the flue duct. Under the suction effect of Rafael nozzle, the flue gas entered the measuring chamber after being filtered by the filter in the front of the measuring chamber to realize the measurement. Results show that the on-line CO measurement device based on in-situ sampling can achieve fast and high-precision on-line measurement of CO volume fraction. The CO volume fraction is highly correlated with that of the O2.
    • Engineering Thermophysics
  • Engineering Thermophysics
    Influence of Fluid-Solid Coupling on Flow and Heat Transfer in a Channel with a Flexible Body Inserted
    MA Chengliu, YANG Mo, LI Zheng, CHEN Kai
    2020, 40(8): 635-640. https://doi.org/10.19805/j.cnki.jcspe.2020.08.005
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    Based on the flow and heat transfer in the channel of a new type of pierced rectangular vortex generator (PRVG), the fluid-solid coupled convective heat transfer process with flexible body inserted in the channel was simulated to study the influence of the oscillation of PRVG on the vorticity field and heat transfer performance in the channel, and to explore the mechanism of heat transfer enhancement by the fluid-solid coupling. Results show that the flexible body would produce trailing vortex in the flow field during the deformation process, and when the body reaches its maximum bending degree in a beating cycle, the trailing vortex would fall off into the wake flow at the trailing edge, making the cold and hot fluid mix violently, thus enhancing the heat transfer. With the increase of Re, the heat transfer intensity tends to increase. When Re=3 000, installing a single flexible body in the channel could increase the intensity of the convective heat transfer by 39.4%.
  • Engineering Thermophysics
    Experimental Study on Solitary Wave Characteristics of Liquid Film over a Triangular Wall
    WU Zhengren, ZHANG Yameng, LIU Mei, LI Li, YANG Hongyue
    2020, 40(8): 641-645. https://doi.org/10.19805/j.cnki.jcspe.2020.08.006
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    Solitary wave characteristics of liquid film are important factors affecting the surface morphology and heat transfer itself. An experimental platform for falling liquid film flow was built to measure the film flow on an inclined triangular plate, and to further analyze the variation law of velocity and frequency of solitary waves at different inclination angles, Reynolds numbers and distance along the path. Results show that the velocity of solitary waves is positively correlated with Reynolds number, and that on a triangular wall is higher than on a flat plate, which increases gradually along the flow direction. The frequency characteristics of solitary waves have no obvious correlation with Reynolds number, inclination angle and distance along the path, but are closely related to their own generation processes.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Numerical Simulation on a Condenser Considering Velocity Distribution of the Cooling Water
    LING Jiaxi, YI Siqiang, LIAO Xianwei, WANG Changshuo, YANG Jianming
    2020, 40(8): 646-653. https://doi.org/10.19805/j.cnki.jcspe.2020.08.007
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    Based on the numerical models respectively established for the steam and water side of a condenser, an innovative method was proposed to import the velocity distribution of cooling water obtained from the calculation of porous media model on water side into the porous media model on steam side to realize the coupling calculation of flow and heat transfer on both sides. A self-defined program was developed on the Fluent platform for reading the velocity distribution on water side and importing it into the steam side. A coupling simulation was conducted for the steam and water side of a surface condenser in a 600 MW unit. Results show that the coupling calculation method proposed is feasible, and the numerical simulation of condenser performance is more reasonable based on uneven velocity distribution of cooling water on the water side.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Separation Performance Analysis of a Novel Compound Demister
    CHEN Hongwei, FENG Xupeng, XU Jifa, AI Tianchao
    2020, 40(8): 654-659. https://doi.org/10.19805/j.cnki.jcspe.2020.08.008
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    Based on the basic structure of a baffle demister, a new composite demister was manufactured by adding a row of round tubes in the bend pipe area. The method of computational fluid dynamics was used to numerically simulate and analyze the original baffle demister, the baffle demister with hook plate and the new composite demister. Results show that when the droplet size is less than 20 μm, the defogging efficiency of the new composite demister is significantly higher than that of the original baffle demister and the baffle demister with hook plate; when the inlet flow rate is 4 m/s, and the droplet size is 10 μm, the new compound demister would have a defogging efficiency 9.33% higher than the original baffle demister, and 5.33% higher than the baffle demister with hook plate; the restriction of tube bank against incoming flow and the turbulence of the airflow can improve the defogging effectiveness of the new composite demister; the new composite demister captures the maximum number of droplets in tube bank area, indicating that the tube bank plays an important role in the new composite demister.
    • New Energy
  • New Energy
    Influence of Parameters of Catenary Mooring Systems on Dynamic Response of Different Floating Wind Turbine Platforms Under the Coupling Effect of Wind and Wave
    HAN Zhiwei, DING Qinwei, LI Chun, YUE Minnan, DENG Yunhe
    2020, 40(8): 660-670. https://doi.org/10.19805/j.cnki.jcspe.2020.08.009
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    A dynamic model was established for the aerodynamic-hydrodynamic-mooring coupling of floating wind turbines by secondary development of AQWA through Fortran programming, while an algorithm was selected to solve the model. Considering the coupling effect of wind and wave, a study was carried out on the influence of the parameters of different catenary mooring systems on the dynamic response of 3 floating wind turbine platforms and on the corresponding parameters of each system in the wind turbine. Results show that the system parameters have a great effect on the maximum surge and heave, but have a small influence on the maximum pitch angle and cabin acceleration. Moreover, the maximum tension at different mooring positions is different, so the selection of appropriate mooring position can effectively enhance the stability of the platform. The mooring system with catenary of larger diameter would result in higher stability of Barge platform. The distance between connection point and free surface, and the length and diameter of catenary have a great effect on the maximum surge and mooring tension of the Semi platform, which have a small influence on the maximum heave, pitch angle and cabin acceleration.
    • Material Research
  • Material Research
    Insulation Property Evolution of Thermal Barrier Coatings During High Temperature Services
    HAO Hongliang, LONG Yun, YANG Xigang, WANG Yuzhang, WANG Xing
    2020, 40(8): 671-677. https://doi.org/10.19805/j.cnki.jcspe.2020.08.010
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    To study the variation law of thermal conductivity of thermal barrier coatings (TBCs) in severe service environments, like high-temperture salt spray atmosphere, etc., the Lattice Boltzmann Method (LBM) and the analysis model of heat transfer process were used to analyze the effects of the following factors on the insulation performance of the TBCs, such as the thickness of ceramic layer and bond layer, the convective heat transfer coefficient on flue gas side and cooling air side, and so on. Results show that the thermal insulation property of TBCs reduces rapidly after corrosion, which weakens with increasing effective thermal conductivity of TBCs after sintering. The thickness of ceramic layer plays a decisive role to the thermal insulation properties of TBCs, i.e. the thermal insulation properties of TBCs increase almost linearly with the thickness of ceramic layer, while the bond layer has little effect. The increase of convective heat transfer coefficient would lead to reduced temperature of blade substrate on cooling air side, but to increased temperature of blade substrate on flue gas side.
  • Material Research
    Study on Mechanical Properties of 1CrMo Layer Deposited by Laser Cladding on 9%Cr Steel Surface
    CHEN Zhijun, QIAO Shangfei, DONG Gang, LIU Xia, YAO Jianhua
    2020, 40(8): 678-685. https://doi.org/10.19805/j.cnki.jcspe.2020.08.011
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    To solve the problem of low Cr reduction efficiency on the journal surface of a 9%Cr steel rotor caused by high dilution rate and high heat input when surfacing 1CrMo alloy on the rotor journal, where local repair is not available after wear damage, a deposit welding test was carried out with 1CrMo alloy on the surface of 9%Cr steel by laser cladding instead of surfacing, following which, the microstructure and properties of the 1CrMo cladding layer were tested and analyzed. Results show that the laser cladding technology helps to form good cladding of 1CrMo alloy on the surface of 9%Cr steel, with high mechanical properties of the cladding layer. Compared with surfacing technology, the laser cladding can effectively reduce the dilution of substrate to the cladding layer, thus improving the Cr reduction efficiency of the surface. Compared with the base metal, the tensile strength of 1CrMo cladding is slightly lower, but its ductility and toughness are better, proving the mechanical properties of 1CrMo cladding to meet the design requirements of 9%Cr rotor journal in steam turbines.
    • Hydroturbine Technology
  • Hydroturbine Technology
    Experimental Study on Sediment Abrasion over Guide Vanes in Mixed-flow Hydroturbines of High Head Hydropower Stations
    TIAN Wenwen, LIU Xiaobing, LI Jia'nan, YUAN Shuai, LU Siyang, LI Yebing
    2020, 40(8): 686-692. https://doi.org/10.19805/j.cnki.jcspe.2020.08.012
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    Experimental study and numerical calculation were conducted on the sediment abrasion over turbine guide vanes in a high head hydropower station to find the wear law of S135 and ZG06Cr13Ni5Mo materials commonly used for moving guide vanes, and 1Cr18N9Ti and Q345 for fixed guide vanes of hydraulic turbines, after which, the calculation formula of sediment wear rate was fitted. Results show that the influence of sediment velocity is higher than that of sediment concentration by two orders of magnitude. The wear on suction surface of guide vanes is more serious than on pressure surface, and obvious lines, spots and gaps could be observed in the head and tail of guide vanes. Both the S135 for moving guide vane and the 1Cr18Ni9Ti for fixed guide vane have high resistance to sediment erosion.