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  • Fundamental Research
    Study on Heat Transfer Performance of PCHE Adapted to Physical Property Variation of SCO2
    ZHAO Quanbin, HOU Min, SUN Jianfeng, ZHANG Dalin, QI Shaopu, CHONG Daotong
    2023, 43(12): 1531-1538. https://doi.org/10.19805/j.cnki.jcspe.2023.12.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    In view of the problems, such as the near-critical state of CO2 working fluid in the cold end of the supercritical CO2 Brayton cycle, the physical properties change drastically with temperature, and the difficulties in design and operation control of the cold end heat exchanger, the straight channel printed circuit heat exchanger (PCHE) and the variable section channel PCHE applied to supercritical CO2 power cycle cold end heat transfer were designed, and the flow and heat transfer characteristics of SCO2 in PCHE of variable-section flow channel were analyzed, based on the method of segmented design of heat exchanger. SIMULINK was used to establish a simulation model of the heat exchanger, the influences of the inlet parameters on the SCO2 outlet parameters of heat exchangers with different flow channel forms were studied when the inlet parameters deviated from the design working conditions. Results show that the designed flow channel section of gradual expansion in SCO2 side can increase the heat transfer performance of PCHE, but the pressure loss will be increased. PCHE with flow channel cross-section of progressive expansion can better stabilize the outlet temperature of SCO2 while the inlet parameters of the cold side and hot side deviate from the design working conditions, and the operating range of the cold end parameters can be broadened.
  • Fundamental Research
    Influences of Turbulent Prandtl Number Models on Predicting sCO2 Heat Transfer in Horizontal Circular Tubes
    XIE Xiongzhou, YE Daoming, HUANG Junhui, WANG Jianyong
    2023, 43(12): 1539-1548. https://doi.org/10.19805/j.cnki.jcspe.2023.12.002
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    The effects of different Prt models on the numerical simulations of turbulent heat transfer of supercritical carbon dioxide in horizontal tubes were systematically investigated using the SST k-ω turbulence model and the predictive capability of different Prt models was analyzed by comparing against experimental data. Results show that under the condition of low-level buoyancy, the constant turbulent Prandtl number of 0.85 exhibits a good predictive ability, and the maximum deviation for wall temperatures is less than 5 K. Under the condition of strong buoyancy, larger deviations appear for the predictions using Prt=0.85 and the existing models of variable turbulent Prandtl numbers that are corrected for supercritical heat transfer have been demonstrated to be invalid as well. Through in-depth analysis, the turbulent Prandtl number models have profound impacts on fluid flow & heat transfer of supercritical carbon dioxide in the boundary layer, and then determine the turbulent heat transfer performance.
  • Fundamental Research
    Study on Structure and Properties of AlCrN Coating on SP-700 Titanium Alloy for Last Stage Blades in a Steam Turbine
    LI Cong, NIE Bingyue, REN Yanjie, LI Wei, CHEN Wei, ZHOU Libo, CHEN Jian
    2023, 43(12): 1549-1556. https://doi.org/10.19805/j.cnki.jcspe.2023.12.003
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    In order to investigate the effect of substrate negative bias voltage on the structure and properties of the ion plating coatings, AlCrN films were deposited on SP-700 titanium alloy by three different ion plating processes. The morphology, phase composition, micro-hardness, wear resistance and electrochemical corrosion resistance of the coatings were measured by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Vickers microhardness tester, reciprocating friction and wear tester, white light interference 3D surface profiler and electrochemical workstation. The corrosion behavior of the coating in HF solution with mass fraction of 5% was measured by immersion corrosion method. Results show that the surface of the ion plating coating is compact, mainly composed of cubic (Cr,Al) N phase and cubic Al phase, and its microhardness is high, the friction coefficients of the coatings are lower during friction and wear process, the wear mass loss of the specimen in the process 2 is the smallest, and the relative wear resistance reaches 902.26. The corrosion resistance of AlCrN coating in NaCl solution with mass fraction of 3.5% is similar to that of titanium alloy substrate. The corrosion resistance of AlCrN coating in HF solution is better.
    • Power Equipment and System
  • Power Equipment and System
    Model Verification and Calculation Analysis of Dynamic Characteristics of Water Wall of Ultra-supercritical Boiler Based on Frequency Domain Method
    BI Lingfeng, DU Xiaocheng, ZHANG Xirong, LI Weiteng, CHEN Jingrong, CHEN Tingyu, YANG Dong
    2023, 43(12): 1557-1566. https://doi.org/10.19805/j.cnki.jcspe.2023.12.004
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    In order to study the dynamic characteristics of the water wall outlet parameters of ultra-supercritical boiler, the calculation model of the dynamic characteristics of the water wall system under supercritical pressure was established by using the frequency domain method. The experimental results show that the calculated values are in good agreement with the measured data. The lower furnace water wall of an ultra-supercritical boiler was calculated, and the dynamic characteristics under 75%THA load were obtained. The dynamic characteristics at heat flux, inlet enthalpy, inlet mass flow rate and outlet pressure step were studied. The effects of heat flux, inlet enthalpy, inlet mass flow, and outlet pressure step on the outlet fluid parameters were analyzed separately. Results show that the response time due to disturbance decreases when the inlet enthalpy, inlet mass flow rate, and heat flux increases; the response time due to disturbance increases when the inlet pressure and pipe section length increase.
  • Power Equipment and System
    Analysis of Initial Value Dependence and Nonlinearity of Air Jet in Furnace
    LING Liang, ZHAO Jingshuai, LIU Wenhua, ZHAO Yanfeng, WANG Wenshuai, YANG Mo
    2023, 43(12): 1567-1576. https://doi.org/10.19805/j.cnki.jcspe.2023.12.005
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    In order to study the initial value dependence and nonlinearity of air jet in furnace, a simplified two-dimensional CFD numerical model and a three-dimensional cold tangential jet experimental model were established respectively for a tower coal-fired boiler. The nonlinear characteristics of flow in the furnace were discussed by combining numerical simulation with experiment, and a new nozzle startup mode-"sequential startup" was proposed. Results show that even if the geometric structure and boundary conditions are completely symmetric, the flow field may also be asymmetric. With the increase of Reynolds number, the internal flow undergoes stable steady state solution, periodic oscillation solution and chaotic solution in turn. When arranging a pair of nozzles, the flow shows obvious multi solution characteristics. Within a certain Reynolds number range, the only result can be controlled by "sequential startup" to achieve accurate flow control. Only when the velocity phase diagram of the monitoring point is a steady attractor or a limit cycle attractor, will the flow show an initial value dependence on the opening sequence of the nozzle. After experimental verification, starting the nozzles at four corners in a certain sequence can control the only result of the flow field, that is, precise control is realized.
  • Power Equipment and System
    Determination of Adiabatic Film Cooling Effectiveness in Transonic Channel Flow
    LIU Yisu, ZENG Wei, DAI Siming, LI Jianing, MA Haiteng
    2023, 43(12): 1577-1584. https://doi.org/10.19805/j.cnki.jcspe.2023.12.006
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    In transonic flow, the derivation of recovery temperature in adiabatic film cooling effectiveness is still controversial. There are two different kinds of methods, namely, liner regression method (LRM) and dual liner regression technique (DLRT). LRM believes that the recovery temperature equals to adiabatic wall temperature for the uncooled model. But DLRT determines the recovery temperature from two cooled experiments which only differ in coolant temperature. To explore the difference between LRM and DLRT, experimental rig of transonic channel flow with a mainstream Mach number of 0.85 was built. Transient thermal measurements by infrared thermography were conducted for the uncooled and cooled cases. The mainstream total temperatures of experiments were 330 K and 345 K respectively. For cooled experiments, the blowing ratios was 1.0 and the coolant temperatures were 282 K, 287 K and 291 K respectively. Results show that the convective heat transfer coefficients processed by two methods are basically the same. However, the adiabatic film cooling effectiveness obtained by the two methods is qualitatively different, due to the difference of recovery temperatures.
  • Power Equipment and System
    Effect of Jet Nozzle Angle and Equivalence Ratio on Premixed Reacting Jet in Axial Staged Combustion Chamber
    ZHANG Liang, JIN Zhaoyang, YAO Fei, GE Bing
    2023, 43(12): 1585-1591. https://doi.org/10.19805/j.cnki.jcspe.2023.12.007
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    The thermal numerical simulation of the fuel axial staged model combustion chamber was carried out, so as to analyze the effects of jet nozzle angle and equivalence ratio on the velocity field, temperature field, residence time, turbulent kinetic energy distribution and pollutant emission of the model combustion chamber. Results show that with the increase of jet equivalence ratio, except for 45°, obvious backflow appears at the downstream of jet nozzle when the angle comes to 90° and 135°, and the flue gas residence time in the combustion chamber increases. With the decrease of jet nozzle angle, the residence time of the primary combustion zone increases, and the residence time of the secondary combustion zone decreases, but the total residence time increases. With the increase of jet nozzle angle and jet equivalent ratio, the high turbulent kinetic energy region in the combustion chamber increases. Compared with jet nozzle angle of 90° and 135°, the NOx mass fraction at jet angle of 45° is higher when the jet equivalent ratio is low, indicating that under certain operating conditions, the emission characteristics are lower when the jet angle is 45°.
  • Power Equipment and System
    Study on the Start-up Characteristics of Secondary Passive Residual Heat Removal System
    SUN Ao, CHENG Jie, ZHU Dongbao, TIAN Chunping, WANG Jianjun, YAN Changqi
    2023, 43(12): 1592-1598. https://doi.org/10.19805/j.cnki.jcspe.2023.12.008
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    Taking the offshore nuclear power platform as the application object, based on the design scheme of the secondary passive residual heat removal system (PRHRS), an experimental facility was designed and built. The start-up characteristics of the system were studied, and the evolution of important parameters of the system during the start-up process was analyzed. Results show that the PRHRS can establish stable natural circulation and effectively remove the heat generated from the U-type tubes in the steam generator under the studied working conditions. During the start-up process, the initial operation pressure only affects the process of the system reaching the asymptotic steady-state, but not the final steady-state of the system. The thermal stratification in the cooling water tank plays an important role in the evolution characteristics of the temperature at the outlet of the passive residual heat removal heat exchanger.
    • New Energy Resources and Energy Storage
  • New Energy Resources and Energy Storage
    Development of sCO2 Rankine Cycle System Based on Gas Turbine Waste Heat Recovery and LNG Cold Energy
    MOU Wenbiao, WANG Zheng, FU Hongjun, WANG Jin, XIAO Gang
    2023, 43(12): 1599-1606. https://doi.org/10.19805/j.cnki.jcspe.2023.12.009
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    A waste-heat power generation system was proposed based on supercritical carbon dioxide (sCO2) Rankine cycle coupled with the natural gas expansion, using gas turbine flue gas as the heat source and LNG as the cold source. For 3 million tons per year LNG receiving station, the sensitivity analysis and optimization calculations of cycle parameters on thermodynamic performance were carried out. Results show that the net power of system can reach 528.57 MW, which is able to match 342 MW gas turbine. LNG contributes 0.095 7 MJ/kg of electrical energy, and the thermal efficiency of the system reaches 63.54%. Compared with the traditional gas-steam combined cycle, the net power of system is increased by 3.5%, and the efficiency of system is improved by 2.15 percentage points.
  • New Energy Resources and Energy Storage
    Performance Simulation and Analysis of Solar-assisted Direct-expansion PVT Heat Pump Hot Water System in Different Cities
    LU Wanglin, SHI Yu, BAO Jiaqi, LIU Wenjie, DAI Yanjun
    2023, 43(12): 1607-1614. https://doi.org/10.19805/j.cnki.jcspe.2023.12.010
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    The simulation model of the direct-expansion PVT heat pump hot water system was developed based on its working principle by iteration algorithm to investigate the system performance under various environmental conditions. Results show that in Shanghai, Beijing, Lhasa, Lanzhou, Kunming and Guangzhou, the average COP of direct-expansion PVT heat pump hot water system on typical days in summer is 7.34, 7.30, 6.98, 8.18, 6.24 and 6.79, and the heating time for given amount of water is 275 min, 273 min, 279 min, 243 min, 314 min and 295 min, respectively. The average COP of direct-expansion PVT heat pump hot water system on typical days in winter is 5.59, 5.21, 6.05, 5.03, 6.48 and 5.43, and the heating time for given amount of water is 344 min, 364 min, 316 min, 376 min, 298 min and 359 min, respectively. In the above-mentioned cities, compared to pure photovoltaic modules, the annually-averaged electricity generation benefits of PVT modules are 9.28%, 8.56%, 10.42%, 10.01%, 7.70%, 7.64%, respectively.
  • New Energy Resources and Energy Storage
    Exergoenvironmental Analysis of Coal-fired Power Generating System Integrated with Carbon Capture and Solar Energy System
    SONG Ruizhe, KONG Mengdi, YE Xuemin, LI Chunxi
    2023, 43(12): 1615-1625. https://doi.org/10.19805/j.cnki.jcspe.2023.12.011
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    The Eco-Indicator 99 method was used as an exergoenvironmental index evaluation method to conduct the environmental analysis of the conventional coal-fired unit (scheme 1), coal-fired carbon capture power system (scheme 2) and solar-assisted coal-fired carbon capture power system (scheme 3).The life cycle assessment of coal and each equipment was conducted, and the exergoenvironmental indices of the three schemes were compared. Results show that system exergy efficiency is characterized by scheme 3>scheme 1>scheme 2. Considering the power penalty induced by carbon capture and storage (CCS) and the solar power compensation to the unit power, the specific environmental impact of electricity is indicated with scheme 2>scheme 1>scheme 3. The power consumption of CCS system results in a decrease in the net power output of the system, the environmental impact of producing 1 kW·h of electricity is reflected with scheme 2>scheme 3>scheme 1. The exergoenvironmental indices show that only the boiler generates pollutants and play a dominant role in the environmental impact. The environmental impact can be reduced by reducing pollutant generation. For boilers, small turbines and other equipment, the environmental impact can also be cut down by improving the exergy efficiency.
    • Digitalization and Intelligentization
  • Digitalization and Intelligentization
    Power Control Strategy of the SOEC System for Smoothing Wind Power Fluctuations
    WU Xin, FENG Ge, XIONG Xingyu
    2023, 43(12): 1626-1633. https://doi.org/10.19805/j.cnki.jcspe.2023.12.012
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    In order to smooth the fluctuation of wind farm output power, considering the high-efficiency characteristics of solid oxide electrolytic cells (SOEC) for hydrogen production through water electrolysis, a kilowatt-scale SOEC stack model was constructed based on the actual data and its accuracy was verified. To address the non-linearity and time-lag characteristics of the SOEC system, a power control strategy based on model prediction was proposed to mitigate the power fluctuations in wind farms. Based on the operational data of a 15 MW wind farm, a wind farm output power decomposition method was proposed using the ensemble empirical mode decomposition method, so as to obtain charging power instructions of the SOEC system and conduct simulation verification on it. Results show that the power control effect of the SOEC system based on model prediction is very effective, which can realize the following change of charging power command, and the mean absolute percentage error is 1.674%, indicating that it has a high accuracy in suppressing wind power fluctuations.
    • Green Energy and Low-carbon Technology
  • Green Energy and Low-carbon Technology
    Effect of Different Flue Gas and Acidification Conditions on Denitrification Performance of Active Coke
    CHENG Weiliang, XING Wangda
    2023, 43(12): 1634-1640. https://doi.org/10.19805/j.cnki.jcspe.2023.12.013
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    Based on the single variable control method, the dependence of denitrification effect of active coke on reaction temperature, ammonia nitrogen ratio and oxygen content was studied. The active coke was acidified by sulfuric acid, hydrochloric acid and nitric acid respectively, and the influence of acidified active coke on denitrification efficiency was analyzed. On this basis, different acid treatment experiments of V2O5 modified active coke were carried out to compare and analyze the change of denitrification efficiency. Results show that the denitrification efficiency increases with the increase of temperature. The denitrification efficiency is highest in the range of 1.0-1.1 ammonia nitrogen ratio. When oxygen content is 10%, the denitrification efficiency of active coke reaches the peak value of 51.3%. At 200℃, the denitrification efficiency of the three acidified active coke increases. The denitrification efficiency of V2O5 modified active coke without acidification increases by 30.7%. And the denitrification efficiency of V2O5 modified active coke is improved by 15.8% after nitric acid acidification, while that of sulfuric acid and hydrochloric acid is not obvious.
  • Green Energy and Low-carbon Technology
    Optimization Study of SCR Static Mixer Based on Comprehensive Performance Evaluation
    LI Xinglei, LU Zhimin, LI Debo, LI Bohang, GUO Songjie, YAO Shunchun
    2023, 43(12): 1641-1648. https://doi.org/10.19805/j.cnki.jcspe.2023.12.014
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    In order to comprehensively evaluate the mixing effect and drag loss of static mixers in selective catalytic reduction (SCR) system, a comprehensive performance evaluation index combined the uniformity of flow field and drag characteristics-dimensionless mixing efficiency η was proposed. According to the field requirements, the comprehensive performance of the system was evaluated by numerical simulation method with circular, petal and SMV mixers as examples. Results show that the η of circular mixer, SMV mixer and petal-shaped mixer are 16.18%, 22.50% and 26.88%, respectively. The petal-shaped mixer has the best comprehensive performance. Under the condition of sequence arrangement, same direction layout and coverage rate of 37%, the overall performance of the petal-shaped mixer is the best, and its dimensionless mixing efficiency η is 28.60%, which is 6.40% higher than before optimization.
  • Green Energy and Low-carbon Technology
    Research on Modelling Method of the Incineration Process in Waste-to-Energy Power Plant Based on ISSA-ELM
    ZHAO Zheng, WANG Jin, ZHOU Ziyu, LI Zhuoge, WEI Qiang
    2023, 43(12): 1649-1656. https://doi.org/10.19805/j.cnki.jcspe.2023.12.015
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    In order to establish an accurate and effective multi-input multi-output model of the incineration process in waste-to-plant, a modeling method combining improved sparrow search algorithm (ISSA) and extreme learning machine (ELM) was proposed. Firstly, variable selection was carried out, and stable data was screened based on sliding window. Secondly, the improved sparrow search algorithm was used to optimize the weights of input layer and biases of hidden layer of ELM, so as to eliminate the influence of random selection of weights of input layer and biases of hidden layer on the stability of the model. Finally, the ISSA-ELM model was compared with the traditional BP neural network, ELM model and SSA-ELM model. Results show that the incineration process model of the waste-to-energy plant based on ISSA-ELM is more accurate and effective than BP, ELM and SSA-ELM models, which provides reference for the adjustment of incineration condition and the best operating variable value for operators.
    • Integrated Energy System
  • Integrated Energy System
    Exergy Conversion Characteristics on the Frequency Regulation Ability Enhancement with Steam Distribution System for a CHP Plant
    TANG Haiyu, ZHENG Lijun, MA Guofeng, WANG Chaoyang, LIU Ming, YAN Junjie
    2023, 43(12): 1657-1664. https://doi.org/10.19805/j.cnki.jcspe.2023.12.016
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    Taking the combined heat and power (CHP) supplying industrial steam as the research object, the dynamic model of the steam pipe network was developed. Then, the frequency regulation capability of CHP unit assisted with steam distribution system was studied. The exergy storage equivalent conversion rate of steam distribution system under different operating conditions was analyzed. Results show that, when the extraction valve is kept closing for 30 s, the user side steam pressure reaches the lower limit value, and the additional cumulative power generation is 307 kW·h. When the extraction valve is totally closed, the exergy storage equivalent conversion rate is 84.6%, 82.8% and 81.5% as the power load of CHP unit is 700 MW, 900 MW and 1 000 MW,respectively. The faster the action of the extraction valve is, the faster the CHP plant power rises. When the valve closing time is 5 s, the maximum CHP plant power climbing rate is 9.77 MW/s. The variable load rate increases when the CHP unit assisted steam distribution system in frequency regulation, and the operation flexibility of CHP unit can be enhanced.
  • Integrated Energy System
    Study on Operational Optimization of Virtual Power Plant Considering “Source and Load” Uncertainties
    BAO Zhe, LI Wei, ZHANG Xiaofang, XU Ye, YU Songyuan
    2023, 43(12): 1665-1674. https://doi.org/10.19805/j.cnki.jcspe.2023.12.017
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    In order to effectively avoid potential imbalance between supply and demand caused by the "source and load" uncertainties, and promote the large-scale development of the virtual power plant, an operational optimization model considering "source and load" uncertainties was proposed based on Copula function, birandom chance-constrained programming algorithm and thermoelectric decoupling. Results show that this model can not only accurately characterize the "source and load" uncertainties and formulate the operational strategies with optimal economic benefits and full utilization of energy, but also provide the effective linkage between the operating costs and default risks, and offer a theoretical basis for decision makers to weigh the risks and economic benefits of energy supply.