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  • 2022 Volume 42 Issue 4
    Published: 15 April 2022
      
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  • Molecular Dynamics Research on the Interaction of Calcium, Silicon and Magnesium During the Combustion of Zhundong Coal
    GUO Wangui, Lü Weizhi
    2022, 42(4): 293-301. https://doi.org/10.19805/j.cnki.jcspe.2022.04.001
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    Aiming at the problem that the formation of akermanite could affect the slagging of Xinjiang Zhundong high-calcium coal during the combustion process, based on molecular dynamics method, the two processes before the formation of akermanite at different temperatures and ratios of minerals were discussed, such as the combination process of CaO and SiO2 and the combination process of CaSiO3 and MgO. By calculating the binding energy and diffusion coefficient between different molecules, the binding and diffusion characteristics of these minerals were studied in the reaction process. Results show that the temperature has no obvious influence on the binding characteristics of CaO on the surface of SiO2 and MgO on the surface of CaSiO3, but has an important influence on their diffusion. With the increase of the temperature, the diffusion coefficient of CaO on the surface of SiO2 and the diffusion coefficient of MgO on the surface of CaSiO3 gradually increase, which indicates that it is easier to form akermanite at high temperatures.
  • Simulation on Pressurized Oxy-fuel Combustion of Coal Char Based on ReaxFF MD Method
    HONG Dikun, LEI Ming, ZHAI Xiaoming, GUO Xin
    2022, 42(4): 302-308. https://doi.org/10.19805/j.cnki.jcspe.2022.04.002
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    The molecular structure model of Wucaiwan coal char was constructed based on experimental characterization. The effect of pressure on the oxy-fuel combustion of Wucaiwan coal char was studied using reactive molecular dynamics (ReaxFF MD) simulation. The mechanism of the effect of pressure on char-O2 oxidation reactions and char-CO2 gasification reactions was revealed by analyzing the evolution of char microstructure. Results show that with the increase of pressure, the overall carbon conversion of char increases, and the net contribution of char-O2 oxidation to char conversion increases, while the net contribution of char-CO2 gasification to char conversion decreases. Increasing pressure can reduce the activation energy of char-O2 oxidation reactions, but has a little effect on the activation energy of char-CO2 gasification reactions.
  • Uniform Mixing Technology of Grille Style Cold and Hot Primary Air for Medium Speed Mill
    ZHOU Yaxing, HU Jinyi, YANG Jianguo, WANG Jingyi, CHEN Zhangwei, WENG Gefeng, XIE Xiaoqiang, ZHAO Hong
    2022, 42(4): 309-315. https://doi.org/10.19805/j.cnki.jcspe.2022.04.003
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    Aiming at the problem of inaccurate measurement of primary air velocity and temperature in a medium speed mill equipped with a rectangular primary air duct and narrow side for cold primary air inlet, the performance characteristics of the problems were investigated by experiments, so as to analyze the flow field structure of the mixing air duct. On the premise of keeping the same original pipe size, a method of cold and hot primary air mixing at grille inlet was proposed, and the arrangement of grille inlet holes was progressively optimized. Results show that the proposed method can improve the flow field of the mixing air duct. Under the premise that the increase of the resistance in cold primary air duct does not affect the cold primary air adjustment ability, air velocity and temperature uniformity at the following sections for each optimization model would be greatly improved, such as air velocity measurement point, temperature measurement point and outlet of the mixing air duct. Therefore, the operation performance of the coal mill can be improved effectively.
  • Deposition Mechanism of Dust Particles on the Solar PV Module Surfaces and Simulation on Dust Accumulation Characteristics
    ZHAO Weiping, Lü Yukun, YAN Weiping
    2022, 42(4): 316-325. https://doi.org/10.19805/j.cnki.jcspe.2022.04.004
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    Particle deposition mechanism was investigated and deposition condition was proposed based on the analysis of the forces of dust particles and the surface energy effect on particle deposition. The dust accumulation numerical model of PV (photovoltaic) modules was established. The rationality of the deposition model was verified by comparing the simulation and experimental results under the same conditions. On that basis, the effects of particle size, wind speed and tilt angle on the dust deposition amount of the PV module surfaces were analyzed. Results show that the deposition amount of 10 μm particles is the largest under the same conditions, and the dust accumulation is negatively correlated with particle size when the tilt angle is greater than 30°. Furthermore, the deposition of 30 μm particles on the module surfaces decreases approximately linearly with increasing tilt angle. Besides, when the tilt angle increases from 15° to 60°, the dust deposition amount can be reduced by about 2.3 g/m2 when the wind speed is 7 m/s, and the reduction rate is approximately 52.4%. The dust accumulation exhibits an approximate V-shaped changing pattern with increasing wind speed. An area with dust particle size less than 30 μm and annual average wind speed of about 3 m/s may be suitable for constructing the PV power plants. Additionally, appropriately increasing tilt angle is beneficial to reduce the accumulated dust.
  • Study on Two-way Strong Fluid-Structure Coupling of Wind Turbine Blade with Pitch Fault
    WANG Yuanbo, LI Gen, LI Chun, LIU Qingsong
    2022, 42(4): 326-333. https://doi.org/10.19805/j.cnki.jcspe.2022.04.005
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    In order to explore the aerodynamic characteristic and structural response of large horizontal axis wind turbine blade with pitch fault under the highly coupled effects of multi-physical field on the condition of shut down after reaching the cut-out wind speed, based on two-way strong fluid-structure coupling combined with computational fluid dynamics and finite element method, the aerodynamic and structural status of the NREL 5 MW wind turbine blades with pitch fault/success were compared and analyzed. Results show that the wave range of blade flapwise torque under two-way strong fluid-structure coupling is wider than that of no fluid-structure coupling, and the maximum aerodynamic torque and tip displacement of the blade with pitch fault under the cut-out wind speed are 13.8 times and 14.1 times of those with successful pitch, respectively. Meanwhile, transient buckling occurs in blade with pitch fault.
  • Simulation Study of Trans-critical CO2 Heat Pump System with Ejector
    NIU Qingyu, GUAN Xin, SONG Ziye, QIN Tao
    2022, 42(4): 334-340. https://doi.org/10.19805/j.cnki.jcspe.2022.04.006
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    A self-built trans-critical CO2 heat pump system was used to carry out thermal performance experimental study, and the influence of CO2 outlet temperature and evaporation temperature on the heating coefficient (Coph) of a trans-critical CO2 heat pump system (SBC) was analyzed and compared. On this basis, the corresponding thermodynamic model of the trans-critical CO2 heat pump system with an ejector(SEC) was established. The system cycle program was written by Matlab, and the system performance was numerically simulated. The variation of injection coefficient, working medium dryness and Coph at ejector outlet was investigated with the change of working fluid pressure, working fluid temperature, evaporation temperature and other parameters. Results show that the simulation value is in good agreement with the experimental data, and the established system thermodynamic model has high accuracy. When the working fluid temperature increases from 31℃ to 38℃, the maximum Coph of SEC is 24.8% higher than that of SBC. While the evaporation temperature increases from 5℃ to 13℃, the maximum Coph of SEC is 28% higher than that of SBC. The ejector greatly reduces the throttling loss caused by CO2 working medium in the expansion process and plays a significant role in improving the system performance.
  • Study on Off-design Thermal Performance of Solar-assisted Coal-fired Generating Units with Carbon Capture
    JIANG Jintao, LI Chunxi, DONG Zhijian, YE Xuemin
    2022, 42(4): 341-349. https://doi.org/10.19805/j.cnki.jcspe.2022.04.007
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    After comparing three coal-fired power generation schemes of carbon capture, a novel solar-assisted coal-fired power generation system with carbon capture was established, and the thermal performance and exergy performance of the integrated system were evaluated by thermodynamics and exergy models. Based on the exergy contribution of external fuel, the influence of variable conditions on the contribution to system and reboiler products was analyzed. Results show that increasing unit load and initial parameters of the working medium is beneficial to improving thermal economy and exergy efficiency of the integrated system. With the decrease of main steam pressure, the contribution of boiler coal exergy and secondary reheat coal exergy to system products gradually increases, while the contribution of primary reheat coal exergy to system products gradually decreases. With the increase of main steam temperature, the contribution of boiler coal exergy to system products gradually increases, while the contribution of primary and secondary reheat coal exergy to system products gradually decreases. Increasing unit load is conducive to raising the contribution of primary and secondary reheat coal exergy to system products and the contribution of compression waste heat exergy for carbon capture and storage (CCS) to reboiler products.
  • Comparative Study on Two Utilization Methods of Flue Gas Waste Heat in Coal-fired Power Plants
    DONG Wei, XU Jidong, LIU Shuangbai, SI Paiyou
    2022, 42(4): 350-358. https://doi.org/10.19805/j.cnki.jcspe.2022.04.008
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    Two methods of flue gas waste heat utilization systems in coal-fired power plants were introduced, including conventional low-temperature economizer system and raw coal pre-drying system. Taking a 600 MW supercritical unit as an example, the thermodynamic performance of the unit under two waste heat utilization modes was calculated and analyzed. On this basis, the energy saving mechanism of the two systems was further explored from the perspective of energy distribution and energy grade, and the economic efficiency of the units after applying the flue gas waste heat utilizations was compared and analyzed. Results show that,when the boiler exhaust temperature reduces from 130℃ to 95℃, the power supply coal consumption rate of the unit can be reduced by 1.4 g/(kW·h) with the using of conventional low-temperature economizer system. For the raw coal pre-drying system can replace higher-grade fuel chemical energy, the coal consumption rate of power supply can be reduced by 3.7 g/(kW·h), which has a better energy-saving effect and economic benefit.
  • Study on Replacing Gas-fired Boiler by Gas-fired Cogeneration Coupled with Ground Source Heat Pump for Heating Under Carbon Neutral Background
    XUE Xiaojun, HOU Zhihua, ZHANG Hongchang, XU Gang, CHEN Heng, CHEN Honggang
    2022, 42(4): 359-364. https://doi.org/10.19805/j.cnki.jcspe.2022.04.009
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    In view of the current carbon neutrality target and the shortage of natural gas, taking Beijing as an example, a scheme that using gas-fired cogeneration coupled with ground source heat pump replaced gas-fired boiler for heating was proposed, in which the electric energy generated by gas-fired cogeneration was directly used for heating from heat pump. Based on the actual heating data of Beijing, the thermodynamic performance and the carbon emission performance of the coupled heating scheme and the original gas-fired boiler heating scheme were compared and analyzed in detail. The coupled heating scheme can not only improve the utilization efficiency of fossil fuel, but also reduce carbon dioxide emissions. Results show that under the same heating amount, the fossil fuel utilization efficiency of the coupled heating scheme is 2.22 times that of the original heating scheme, and the former can reduce carbon dioxide by 55.02%. The initial investment of the coupled heating scheme is higher, but the annual comprehensive cost after subsidies is lower than that of the original heating scheme.
  • Optimization of Interval Load Scheduling Strategy for a CCHP System Using Natural Gas
    HE Qing, CHANG Dawei, ZHANG Junli, ZHENG Wenguang, CHEN Qi, WANG Shibin, LEI Zhiheng, NONG Jugui
    2022, 42(4): 365-371. https://doi.org/10.19805/j.cnki.jcspe.2022.04.010
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    Aiming at the problem that the actual operation of a combined cooling, heating and power (CCHP) system using natural gas was greatly affected by the load demand interval limitation, and the comprehensive performance optimization was difficult, a scheduling optimization method of multi-objective interval operation based on ε-constraint was proposed. First, the models of gas-steam combined cycle, centrifugal electric compression refrigerator, steam lithium bromide refrigerator and hot water lithium bromide refrigerator, etc. were established, considering the ramping rate constraint of gas turbine and the constraint of electricity purchase and sale. Then taking the optimal economy, environmental protection and energy efficiency as the objective function, the ε-constraint method was used to deal with the multi-objective problem combined with the actual operation demand, and the interval multi-objective optimization scheduling model of CCHP system using natural gas was constructed. Results show that compared with the original strategy of determining electricity by heat in the cooling season, the optimization method has a better effect on the optimal scheduling of interval load, the total operation cost can be saved by RMB 1.3×104 per day and the carbon dioxide emission can be reduced by 15.7 t per day. The economic and environmental benefits are significantly improved by this method.
  • Research on Characteristics of AA-CAES System Under Different Working Mediums and Heating Storage Mediums
    LI Peng, HU Qingya, HAN Zhonghe
    2022, 42(4): 372-379. https://doi.org/10.19805/j.cnki.jcspe.2022.04.011
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    In order to study the operating characteristics of the tri-generative system based on advanced adiabatic compressed air energy storage (AA-CAES) under different working mediums and heating storage mediums, four operation schemes were proposed with air and carbon dioxide (CO2) as working mediums and water and THERMINOL66 as heating storage mediums. The energy analysis and exergy analysis methods were used to compare the system performance differences under the four operation schemes, and to study the influence of the temperature of the low-temperature heat storage medium and the convective heat transfer coefficient on the system performance. Finally, non-dominated sorting genetic algorithm-II (NSGA-II) was adopted for multi-objective optimization of the tri-generative system with exergy efficiency and energy storage density as objective functions. Results show that the exergy efficiency and energy storage density of the system are the highest when air is the working medium and water is the heating storage medium. The maximum exergy destruction is generated by the second-stage heat exchanger in the four operating schemes. The lower the temperature of the low-temperature heating storage medium, the higher the exergy efficiency, and the lower the energy storage density. When the convective heat transfer coefficient increases, the exergy efficiency decreases, while the energy storage density firstly decreases and then increases. The optimal performance of the system is obtained when a lower temperature heating storage medium and a moderate convective heat transfer coefficient are applied.
  • Optimal Load Distribution of Cogeneration Units Based on Slime Mould Algorithm
    WEI Zhiting, ZHANG Min, ZHOU Xingye, LI Pei, SHENG Deren, LI Wei
    2022, 42(4): 380-386. https://doi.org/10.19805/j.cnki.jcspe.2022.04.012
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    To solve the problem of unreasonable thermoelectric distribution and high energy consumption of the main-pipe thermal power unit, a slime mould optimization algorithm was proposed to optimize the load distribution in the order of the steam turbine side and the boiler side,which was verified through the actual operating data of a "three boilers and two turbines" main-pipe unit. Results show that the average steam consumption rate is reduced by 0.063 t/(MW·h) and the average coal consumption rate was reduced by 0.126 kg/t after optimization.On the basis of meeting the heating conditions, the steam consumption rate on the steam turbine side and the coal consumption rate on the boiler side can be reduced through reasonable thermal and electric load distribution, so as to maximize the energy utilization efficiency.
  • Research and Development of Flexible Heating Control Strategy for 2×300 MW Cogeneration Units
    LIU Zhu, SONG Jiancheng, MA Suxia, LIU Jiale, ZHAO Ming, REN Biao
    2022, 42(4): 387-392. https://doi.org/10.19805/j.cnki.jcspe.2022.04.013
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    Based on the actual heating conditions of thermal power plant, six flexible heating modes were designed to meet the heat load demand in the whole heating cycle, and a flexible heating control strategy was proposed based on real-time heat load and boiler load. Finally, the engineering test for a subcritical 2×300 MW cogeneration unit in Shanxi province was carried out. Results show that the flexible heating control strategy can automatically switch to the optimal heating mode according to the real-time changes of boiler load and heat load demand. On the premise of ensuring heating demand, the power generation of the whole plant has been increased by 5.5 MW via optimizing heating parameters, indicating that the economic benefits are significantly improved.