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    Boiler Technology
  • Boiler Technology
    Study on Competition Mechanism of Alkali Metals and Heavy Metals in Collaborative Combustion of Sludge and Alkali Coal
    LI Yaode, YANG Dong, ZHOU Xihong, DONG Le, WANG Siyang
    2020, 40(5): 349-355. https://doi.org/10.19805/j.cnki.jcspe.2020.05.001
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    The migration characteristics of heavy metal elements Pb, Ni and As in the co-combustion of low-quality fuel (high alkali coal) and biomass fuel (sludge) were studied at the characteristic temperature of a CFB boiler. It is found that the combustion temperature plays an important role in the thermodynamic equilibrium distribution of heavy metals. The higher the temperature is, the higher the molar ratios of Pb, Ni and As would be in the gas components. When the temperature exceeds 1 300℃, Pb would migrate to the gas components in the element state. In the CFB temperature range, Pb deposits on the surface of fly ash particles, with most part in the form of PbCl2 and a small amount in the form of PbCl. When the temperature gets above 1 800℃, Ni exists mainly in the form of Ni(g) in the system. Throughout the combustion temperature range, the mass fraction of As increases with the rise of temperature in the form of a single substance. The alkali metal Na mainly competes for the elements Cl and O in the fuel to achieve morphological conversion to heavy metal compounds. Compared with Na, the competitiveness of K is weaker, and K competes for ion CrO42- in the Ni compound at 700℃, resulting in an decrease in the mole fraction of NiO, while K competes with Ni for element O in the system at 850℃, when the reaction process is different from that at 700℃.
  • Boiler Technology
    Effects of Blend Ratio on Combustion Characteristics and NOx Emission in Co-firing Process of Semi-char and Bituminous Coal
    PENG Zhengkang, YAN Yonghong, SUN Liutao, ZHU Wenkun, SUN Rui
    2020, 40(5): 356-364. https://doi.org/10.19805/j.cnki.jcspe.2020.05.002
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    Effects of blend ratio on the ignition, NOx emission and burnout characteristics in the co-firing process of shenhua bituminous coal and shenmu pyrolyzed semi-char were investigated in a 350 kW pulverized coal-fired pilot-scale furnace, during which, the furnace temperature and concentration profiles of gaseous species (O2, CO and NOx) were measured at different axial positions. Results show that with the increase of semi-char blend ratio, the following ignition characteristics get worse, such as elongated ignition stand-off distance, increased ignition temperature and aggravated NOx emission in the primary combustion zone. When EGA gas analysis is used to estimate the ignition point of fuel blends, the CO gas analysis is found to be more appropriate when the blend ratio is 60% and 100%, while the NOx analysis achieves better results in analyzing the ignition of bituminous coal with high volatile matters. The burnout rate of pure semi-char is the lowest, which could be improved by blending into the bituminous coal with high volatile matters.
    • Steam Turbine and Gas Turbine
  • Steam Turbine and Gas Turbine
    Analysis on the Hydrodynamic Stability of a Vaneless Diffuser Based on Dynamic Mode Decomposition
    WU Wei, ZHAO Bo, ZHU Xiaocheng, DU Zhaohui
    2020, 40(5): 365-370. https://doi.org/10.19805/j.cnki.jcspe.2020.05.003
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    To improve the stability of a vaneless diffuser, the unsteady flow fields in the process of convergence and divergence were analyzed by dynamic mode decomposition (DMD) based on the model of two-dimensional vaneless diffuser at different inlet flow angles, while the flow field variation was analyzed during the unsteady calculation under stable and unstable operating conditions. Results show that the modal characteristics obtained under unstable condition by DMD method are close to that by two-dimensional non-viscous linearization stability model, including the number of circumferential modes and the rotation speed of stall cells.
  • Steam Turbine and Gas Turbine
    Influence of Pre-swirl Angle on the Effectiveness of Back-disk Jet Cooling for Radial Turbines
    LU Kangbo, MA Chao, BAI Shuzhan, FANG Tongyi
    2020, 40(5): 371-378. https://doi.org/10.19805/j.cnki.jcspe.2020.05.004
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    Back-disk jet cooling technology is used to cool the region in a radial turbine where the heat load is large. A conjugated heat transfer (CHT) simulation was carried out to study the effects of pre-swirl angle on the back-disk cooling characteristics in the angle range of 60°-120°. Results show that the back-disk jet flow could greatly improve the cooling efficiency for radial turbines. The cooling effectiveness reaches the optimum at the pre-swirl angle of 60°, and then, with the increase of pre-swirl angle, the cooling effectiveness gets worse. At the same radial position, when the cooling coefficient lies in the range of 0.01-0.02, the average cooling efficiency of the back-disk would drop by 0.003 for every increase in pre-swirl angle by 15°; and when the cooling coefficient lies in the range of >0.02-0.04, the average cooling efficiency would drop by 0.016-0.050 for every increase in pre-swirl angle by 15°. When the cooling fluid flows into the main channel of a radial turbine, the turbine efficiency would be reduced accordingly, and the minimum impact could be reached at the pre-swirl angle of 60°.
  • Steam Turbine and Gas Turbine
    Experimental Study on Heat and Mass Transfer in a Humidifier of HAT Cycle
    HE Ming, ZHANG Qing, WANG Yuzhang
    2020, 40(5): 379-384. https://doi.org/10.19805/j.cnki.jcspe.2020.05.005
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    To study the heat and mass transfer characteristics of gas-liquid two-phase flow in a humidifier of humid air turbine (HAT) cycle, an experimental system was established for the high pressure packing humidifier, while a measuring setup was developed for the temperature and relative humidity of pressurized humid air and water, based on which, the distribution of temperature and relative humidity along the height of the humidifier was obtained under 15 working conditions, and the influence of water-gas ratio and inlet water temperature on the humidification process was studied. Results show that the temperature of both the humid air and the water decreases first and then increases along the flow direction, and the humid air has already reached the saturation state at the bottom of the humidifier. The water-gas ratio has a great influence on the humidifier performance and its inner two phase parameters. With the increase of water-gas ratio and inlet water temperature, the temperature of water and air increases at the same location, resulting in increased overall humidification amount. The higher the inlet water temperature is, the earlier the humid air would reach the saturation state at the bottom of the humidifier.
  • Steam Turbine and Gas Turbine
    Storage Strategy Optimization for Gas Turbine Spare Parts Based on Linear Programming Algorithm
    WEN Chenyang, LIU Pei, JIN Jiangbo, LIN Shitao, LI Zheng
    2020, 40(5): 385-391. https://doi.org/10.19805/j.cnki.jcspe.2020.05.006
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    The replacement strategy of hot aisle components for gas turbines was discussed in depth, and the economics of combined storage strategies for multiple gas turbine spare parts were analyzed and compared in detail through a linear programming algorithm, following which, a calculation method was proposed for spare parts storage strategies with minimum component costs. Results show that the combined storage strategy for multiple gas turbines could save the parts cost during maintenance, since the spare parts could be replaced in turn. The algorithm proposed may be used to optimize the storage strategy of spare parts in actual applications.
    • Turbo-Generator
  • Turbo-Generator
    Effects of Damping Structure on the Suppression of Torsional Vibration in a 600 MW Turbo-Generator Shaft System
    XU Dingjie, LI Luping, ZHOU Zijian, LU Xuxiang, NIU Xiaorui, CHEN Yishuang
    2020, 40(5): 392-397. https://doi.org/10.19805/j.cnki.jcspe.2020.05.007
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    Taking the torsional vibration characteristics of the shaft system in a domestic 600 MW sub-critical turbo-generator set as the object of study, a 3D solid model was established using Solidworks software to comparatively analyze the vibration amplitude for the system with and without damping structures. Results show that the amplitude of torsional vibration decreases obviously in the shaft system with damping structures, and the maximum amplitude appears 0.2 s after the excitation of a three-phase short-circuit fault; the damping structure could not only reduce the maximum value of torsional vibration, but also accelerate the attenuation of vibration amplitude, proving the damping structure to be effective in the suppression of torsional vibration in the shaft system.
    • Automatic Control
  • Automatic Control
    Simulation Research on Pitch Control Strategy for Offshore Wind Turbines
    ZHANG Li, YU Wan, LI Chun, DENG Yunhe
    2020, 40(5): 398-403. https://doi.org/10.19805/j.cnki.jcspe.2020.05.008
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    Based on open source software FAST and Matlab/Simulink co-simulation platform, the disturbance accommodating control (DAC) was adopted for the pitch control of offshore wind turbines, which was subsequently compared with the FAST baseline control, so as to study the effects of different control strategies on the floating stability, to propose an improved DAC strategy, and to analyze the influence of the improved DAC on the performance and rotor speed of related offshore wind turbines. Results show that under the control of DAC, the rotor speed of an offshore wind turbine would keep stable, but the floating stability would be poorer, comapred with the FAST baseline control; the influence of DAC on the floating stability of an offshore wind turbine mainly concentrates on the platform surge and pitch; the improved DAC is believed to be more suitable for the pitch control of offshore wind turbines.
    • Auxiliary Equipment Technology
  • Auxiliary Equipment Technology
    Effects of Gurney Flap on the Performance of a Variable Pitch Axial Flow Fan
    LI Chunxi, ZHANG Chao, ZHANG Ruixing, YE Xuemin
    2020, 40(5): 404-411. https://doi.org/10.19805/j.cnki.jcspe.2020.05.009
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    The performance and internal dynamics of an OB-84 type variable-pitch axial flow fan with Gurney flap (GF) installed at the trailing edge of rotating blades were numerically simulated, while the acoustic noise was predicted. Results show that GF could increase the total pressure rise of the fan, and the larger the height is, the greater the lifting range would be, and the working point of highest efficiency moves to the side with large flow rate. The GF with a height of 0.5% chord length could increase the fan efficiency on the side with large flow rate at blade pitch angles of 29° and 35°. After addition of GF, the secondary leakage vortex occurring on blade tip would aggravate the tip leakage; a pair of shedding vortices appearing in the downstream of trailing edge would increase the pressure difference between the suction surface and the pressure surface. The addition of GF would lead to the increase in aerodynamic noise of the fan. When the GF with a height of 0.5% chord length is adopted, the total pressure rise and the fan efficiency would be increased by 12.01% and 3.13%, respectively.
    • Environmental Protection Technology and Equipment
  • Environmental Protection Technology and Equipment
    Techno-Economic Study on Semi-dry Flue Gas Desulfurization by Calcium-based and Sodium-based Solutions
    GUO Shiyi, PAN Weiguo, KANG Di
    2020, 40(5): 412-418. https://doi.org/10.19805/j.cnki.jcspe.2020.05.010
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    To study the characteristics of medium-temperature flue gas desulfurization by semi-dry spray process, an experimental platform was built up, based on which, experimental tests were conducted to analyze the effects of inlet gas temperature, inlet SO2 concentration, stoichiometric ratio (SR) and AAST on the desulfurization efficiency, respectively with Ca(OH)2 solution, Na2CO3 solution and NaHCO3 solution as the absorbents. Meanwhile, a techno-economic analysis was carried out by taking a refuse power plant as an example. Results show that when the outlet gas temperature keeps constant, the desulfurization efficiency of above three absorbents improves with the increase of inlet temperature, but reduces with the rise of inlet SO2 concentration. Under same conditions, the desulfurization efficiency of NaHCO3 solution is the highest, followed by Na2CO3 solution and Ca(OH)2 solution. When Ca(OH)2 is taken as the desulfurization absorbent, the comprehensive desulfurization efficiency can reach 84%. Considering the economy and desulfurization efficiency, it is recommended adopting Ca(OH)2 solution as the absorbent in engineering applications.
  • Environmental Protection Technology and Equipment
    Experimental Study and Numerical Simulation on CO2 Separation from Power Plant Flue Gas by Membrane Method
    LI Boyang, YU Juan, FENG Fan, ZHANG Zhongxiao
    2020, 40(5): 419-425. https://doi.org/10.19805/j.cnki.jcspe.2020.05.011
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    To study the effects of hollow fiber membrane on the separation of low concentration CO2 from power plant flue gas, a single-stage membrane separation system was built, based on which, the factors affecting the separation performance of the system were studied experimentally, such as the pressure and total flow rate of inlet gas, the volume fraction of various components in inlet gas and the temperature of membrane module, etc. In addition, a simplified mathematical model was established for the separation membrane module, while the relative errors between the calculated results and experimental data were analyzed. Results show that the volume fraction of CO2 in permeable gas increases with the rise of both the total flow rate of inlet gas and the volume fraction of CO2 in inlet gas, and decreases with the increase of the inlet gas pressure. The increase in temperature of the membrane module has little effect on the volume fraction of CO2 in permeable gas. The recovery rate of CO2 in the system increases with the rise of the inlet gas pressure, the volume fraction of CO2 in inlet gas and the temperature of the membrane module, and decreases with the increase of the total flow rate of inlet gas. The calculation results agree well with the experimental data within the allowable error range, and the model is easy to be applied. This may serve as a calculation basis for the process design of CO2 separation by membrane method.
    • New Energy
  • New Energy
    Influence Analysis on Different Concentrating Strategies of Heliostats in a Tower Solar Thermal Power Station
    DU Yuhang, LIU Xiangmin, WANG Xingping, JIANG Zhihao
    2020, 40(5): 426-432. https://doi.org/10.19805/j.cnki.jcspe.2020.05.012
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    Taking the 50 MW tower solar thermal power station as an object of simulation, a heliostat mirror field model and a cylindrical exposed receiver model were established according to the main simulation parameters of the station, based on which, the distribution of flux density on the surface of the receiver was calculated for the following three concentrating strategies of the heliostat, such as the simple, alternating offset and normal distribution concentrating strategy, using the data of typical meteorological years, by the method of ray tracing, under design point conditions, over the whole day of summer solstice, and in different layouts of heliostat field. Meanwhile, the influence of above three concentrating strategies on the safety of the receiver was analyzed. Results show that among the three concentrating strategies, the alternating offset concentrating way could effectively improve the distribution of flux density on the surface of the receiver, resulting in higher safety of the station.