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    Fundamental Research
  • Fundamental Research
    Numerical Study on Mixing Characteristics of Fuel and Air in Hydrogen Micro-mix Burner
    PENG Zhu, ZHANG Zhedian, LEI Fulin
    2023, 43(11): 1391-1398. https://doi.org/10.19805/j.cnki.jcspe.2023.11.001
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    Realizing the uniform mixing of hydrogen and air outside the tube of the hydrogen gas turbine can avoid flashback and achieve low NOx emission. In order to achieve as uniform mixing as possible from the nozzle outlet to combustion, the flow characteristics of the micro-mix nozzle outlet and the influence of the interaction between the fuel-air inflow on the mixing of hydrogen and air were calculated and analyzed by numerical simulation, and the effects of the fuel-air momentum ratio, fuel hole gap ratio, jet height and mixing length on the cold mixing of the micro-mix nozzle were investigated respectively. Results show that the mixing effect is directly impacted by the standard jet depth, the neighboring jet disturbance and the vortex structure of the diffusion section. The suitable standard jet depth is achieved with a momentum ratio Rm in the range of 1.19-1.77, which can lead to more uniform mixing. When the fuel hole gap ratio is 0.54, the interaction of adjacent jets causes a larger gradient in the decrease of the hydrogen concentration in the center of the jet. Increasing the jet height and mixing length can reduce the mixing inhomogeneity, and the development of near-wall vortex pair integrity is beneficial to the mixing improvement.
  • Fundamental Research
    Modelling and Heat Transfer Analysis of Fully Ceramic Microencapsulated Fuel Pellet Based on COMSOL Software
    WANG Mouhao, BU Shanshan, LU Xuxiang, LIU Rui
    2023, 43(11): 1399-1405. https://doi.org/10.19805/j.cnki.jcspe.2023.11.002
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    A full three-dimensional model for fully ceramic microencapsulated (FCM) fuel pellet was constructed using COMSOL software.An efficient modelling method for the random distribution of TRISO particles in FCM fuel pellet was proposed, which could achieve a particle dispersion with high packing fraction. The temperature distribution characteristics of FCM fuel pellets under different packing fractions (35%, 40% and 45%) and various random particle distributions were analyzed. Results show that the temperature in the central region of FCM fuel pellet is high, and the temperature decreases gradually along the radial direction. The temperature of TRISO fuel particles, especially in the fuel core, is significantly higher than that of the particles in the surrounding matrix and the temperature difference can reach 130 K or even higher. The maximum temperature gradient appears in the Buffer layer. Under the same linear power, with the increase of particle packing fraction, the highest temperature of fuel pellet decreases and the average temperature increases slightly. Influenced by the randomness of particle distribution, the scatter degrees of both the average temperature and the maximum temperature distributions increase with the decrease of particle packing fraction. In general, the random distribution of particles has an inconsiderable effect on the average temperature of fuel pellets.
    • Power Equipment and System
  • Power Equipment and System
    Experimental Study on Combustion Optimization of Coal-fired Unit After Flexible Modification
    LÜ Weizhi, ZHAO Xu, HE Xiang, MA Dafu
    2023, 43(11): 1406-1412. https://doi.org/10.19805/j.cnki.jcspe.2023.11.003
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    After the flexible modification of thermal power units, the stable combustion ability of low load is improved. However, the flue gas temperature in the main burner area of the furnace under high load is also bound to be increased, which is easy to cause the problem of slagging and higher NOx production. Taking a 600 MW front and rear wall hedge unit as the research object, the analysis of the reasons for the easy coking of the boiler after flexibility modification and combustion optimization test were conducted. Results show that coking is mainly caused by the increase of flue gas temperature in the main burner area and the reducing atmosphere. By weakening the swirl of the burner, increasing the proportion of direct current air in the burner, reducing the temperature at the outlet of the mill, rationally distributing air, increasing the primary air pressure, controlling the oxygen content in the main burner area and other technical means, the coking in the main burner area can be restrained while ensuring the stable combustion ability under low load.
  • Power Equipment and System
    Effect of Non-uniform Layout of Packing Coupled with Partition Water Distribution on Thermal Performance of Wet Cooling Tower
    BU Zhaobin, SUN Gengsheng, JIANG Guangxu, LÜ Sai, YANG Jichong, HE Suoying, GAO Ming
    2023, 43(11): 1413-1420. https://doi.org/10.19805/j.cnki.jcspe.2023.11.004
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    Taking the large wet cooling tower of a 300 MW unit as the research object, its three-dimensional numerical model of non-uniform layout of packing coupled with partition water distribution was established. When its inner and outer packing zones were arranged with 30 mm and 26 mm S-wave packing, respectively, the effect of non-uniform layout of packing coupled with partition water distribution on the thermal performance of cooling tower was studied under different operating conditions via changing the partition water distribution radius R1 and rearranging the water distribution percentage between the inner and outer zones. Results show that non-uniform layout of packing coupled with partition water distribution can significantly reduce the high-temperature zone in the tower center and increase the air-water ratio. Under the design condition, with the increase of packing partition radius R2 and water distribution percentage in the inner zone P, the Merkel number and volume heat transfer coefficient increase firstly and decrease subsequently. The overall thermal performance can be improved by reducing P at R1=15~35 m or increasing P at R1=40 m. The relatively optimal coupling layout can be achieved at R1=25 m, R2=25 m, and P=35%. Compared with the original tower, the Merkel number and volume heat transfer coefficient increase by 0.09 and 17.0 W/(m3·K), respectively.
  • Power Equipment and System
    Analysis on Fracture Behavior of 20Cr1Mo1VNbTiB Bolt for Supercritical Steam Turbine
    ZHANG Tao, WANG Jianguang, XIE Liming, CHEN Hao, QIAO Xin
    2023, 43(11): 1421-1427. https://doi.org/10.19805/j.cnki.jcspe.2023.11.005
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    During operation of a 660 MW supercritical steam turbine in a power plant, a large number early fracture failures of 20Cr1Mo1VNbTiB bolt of HP governing valves and IP governing valves occurred. The fracture behavior of bolts was analyzed by means of fracture analysis, composition analysis, mechanical property test and microstructure analysis. Results show that under the combined action of pre-tightening force and impact load formed by frequent action of governing valve on bolts, the TiN particles at the bottom of thread tooth with notch effect and stress concentration initiate microcracks in modes of self fragmentation, sharp corner cracking, and attachment matrix high stress distortion zone cracking, and form crack sources in series with each other. Then bolts fracture is caused by rapid crack expansion under load action. Meanwhile, large number of TiN inclusions in the structure destroys the continuity of the matrix, reduces the toughness and crack resistance of the alloy, which causes brittle fracture of the bolts. Therefore, in the process of alloy smelting, the mass of Ti in molten steel should be strictly controlled to be less than 0.1%. The size and amount of TiN precipitated phase should be controlled by optimizing the cooling rate and increasing the amount of fine oxides in steel, so as to reduce its harmful effect and achieve the real purpose of Ti alloying.
  • Power Equipment and System
    Online Calculation Method of Exhaust Enthalpy for Low Pressure Steam Turbine Based on Polytropic Exponent
    WANG Kairun, MA Suxia, HUO Mao
    2023, 43(11): 1428-1433. https://doi.org/10.19805/j.cnki.jcspe.2023.11.006
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    Based on the principle of steam turbine under off-design operating condition, a new method was proposed to calculate steam turbine exhaust enthalpy online-polytropic exponent method. By considering the effects of inlet flow, inlet temperature, inlet pressure and exhaust pressure on low pressure (LP) steam turbine work ability, the polytropic exponent model of LP turbine work was established. An accurate thermodynamic model for a single unit and an improved general model for different units were obtained by using the polytropic exponent method. Results show that the average relative error between the calculated value of the accurate model and the design value is 0.165% and the maximum relative error is 0.738%, and the average relative error between the calculated value of the improved general model and the design value is 0.93%, and the maximum relative error is 3.52%, indicating that the proposed method can meet the accuracy requirement of actual engineering projects.
  • Power Equipment and System
    Life Calculation and Reliability Analysis of Turbine Wheel Based on Monte Carlo Method
    LI Xiaopin, YANG Yu, TIAN Genqi, LI Siqi, WANG Jiayun
    2023, 43(11): 1434-1439. https://doi.org/10.19805/j.cnki.jcspe.2023.11.007
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    To comprehensively study the probabilistic fatigue life and reliability analysis of turbine wheel, low-cycle fatigue test of turbine wheel material 13Cr10MoW1VNbN was carried out. The corresponding result analysis and error optimization were performed. Based on Manson-Coffin formula and material test data, a strain-life prediction model was established. Monte Carlo method and envelope method were used to obtain the fatigue life data of wheel, respectively. The statistical analysis and reliability research were conducted. Results show that the reliability curve by Monte Carlo method has a gentler downward trend than that by envelope method. More uncertainties considered give rise to greater safety margin.
  • Power Equipment and System
    A New Correlation for Predicting Film Cooling Effectiveness of Fan-shaped Holes and Its Application
    LIN Chixiang, CUI Xiaofeng, DAI Ren
    2023, 43(11): 1440-1447. https://doi.org/10.19805/j.cnki.jcspe.2023.11.008
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    Based on the experimental data of fan-shaped holes, a new correlation for predicting film cooling effectiveness was proposed. Considering the influences of hole shape parameters and flow conditions inside and outside the hole on film cooling effectiveness, a surrogate model of correlation characteristic coefficient was built. Results show that the film cooling effectiveness and optimal hole shape parameters of the optimized holes obtained through experimental design (DOE) are basically consistent with those obtained by the surrogated correlation model. The application of the new correlation to accelerate the multi confidence optimization of film cooling hole shape, or to optimize the specific layout of multi film cooling hole arrays has significant engineering application value.
  • Power Equipment and System
    Main Shaft Strength Analysis of Rotary Air Preheater Considering the Influence of Overturning Moment
    GAO Jianqiang, ZHANG Ziyue, LIU Songyang, LI Hongyu
    2023, 43(11): 1448-1453. https://doi.org/10.19805/j.cnki.jcspe.2023.11.009
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    Taking the rotary air preheater of a 660 MW unit as the research object, the stress calculation and strength check of the dangerous section of the main shaft for the rotary air preheater were carried out using the method of bending and torsion synthesis equivalent bending moment. Results show that when the rotary air preheater operates under BMCR conditions, the overturning moment of the main shaft reaches the maximum and the bending stress accounts for 52% of the total synthesis stress, which is an important factor affecting the bending deformation of the main shaft. Compared with the situation without considering the influence of overturning moment, the safety margin of the main shaft is reduced by 40% after considering the over turning moment.
  • Power Equipment and System
    State Recognition Method of Hydraulic Turbine Cavitation Based on Chaos Theory and CNN-OSVM
    LIU Zhong, LI Xianwei, ZOU Shuyun, WANG Wenhao, ZHOU Zehua
    2023, 43(11): 1454-1460. https://doi.org/10.19805/j.cnki.jcspe.2023.11.010
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    Aiming at the problem of low recognition accuracy of hydraulic turbine cavitation condition, which caused by strong nonlinearity of acoustic emission (AE) signal, a cavitation state recognition method of hydraulic turbine based on chaos theory and convolutional neural network combined with optimized support vector machine (CNN-OSVM) was established. The phase space reconstruction of the AE signal under different hydraulic turbine cavitation conditions was carried out to obtain the phase diagram as a data set. The phase map features of different cavitation states were extracted by convolutional neural network, and the optimization support vector machine classifier was optimized by grid search algorithm and K-fold cross-validation algorithm to identify the cavitation state. Results show that the CNN-OSVM model with the input chaotic phase diagram could identify four cavitation conditions accurately, with an average accuracy of 98.8%.Meanwhile, it was proved that CNN-OSVM model had higher recognition accuracy and generalization than CNN model and OSVM model for nonlinear signal classification.
    • New Energy Resources and Energy Storage
  • New Energy Resources and Energy Storage
    Dynamic Response of Offshore Floating Dual-rotor Wind Turbine
    ZHANG Wenguang, SUN Jiahao, LUO Weijian, CHEN Wenhua
    2023, 43(11): 1461-1468. https://doi.org/10.19805/j.cnki.jcspe.2023.11.011
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    To investigate the dynamic response characteristics of an offshore floating dual-rotor wind turbine, its simulation system was constructed based on the OC3-Hywind Spar floating platform. Its aerodynamic-hydrodynamic coupling analysis model was established using free vortex wake (FVW) method and OpenFAST hydrodynamic computation module. The wind-wave coupling analysis and control simulation were conducted. Results show that its power fluctuation amplitude generated by the primary and auxiliary rotors decreases as the wind and wave angle increases. Its flow field between the primary and auxiliary rotors is more complex compared to onshore dual-rotor wind turbine. Multi-objective variable-pitch control can reduce the power fluctuation and alleviate the fatigue damage to auxiliary rotor. The platform motion response fluctuates more significantly within the wind and wave angle range of 0° to 90°.
  • New Energy Resources and Energy Storage
    Performance Evaluation on Supercritical Carbon Dioxide Pumped Thermal Electricity Storage System Integrated with External Thermal Source
    SUN Ruiqiang, LI Yanbin, LIU Ming, ZHAO Yongliang, YAN Junjie
    2023, 43(11): 1469-1476. https://doi.org/10.19805/j.cnki.jcspe.2023.11.012
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    The pumped thermal electricity storage (PTES) system based on the supercritical carbon dioxide was studied. The thermodynamic and economic analysis models were developed, and the system parameters were optimized, so as to analyze the effects of compressor efficiency, turbine efficiency, pressure loss and the minimum heat exchange temperature difference on the system performance. In addition, an integrated system configuration using gas turbine exhaust as external heat source was proposed. The performance of the independent PTES system and the integrated external heat source system was analyzed. Results show that the highest roundtrip efficiency of the independent PTES system can reach 62.91%. After integrating the external thermal, the investment cost per unit energy decreases, and the energy efficiency of the system decreases with the increase of discharge time and discharge power.
  • New Energy Resources and Energy Storage
    Planning and Scheduling of Integrated System of Light Hydrogen Storage and Methanol for High Proportion of Renewable Energy Consumption
    LIU Kangxiang, ZHOU Jiahui, XU Gang, CHEN Yanqi, ZHANG Runzhi, LIU Wenyi
    2023, 43(11): 1477-1486. https://doi.org/10.19805/j.cnki.jcspe.2023.11.013
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    In order to solve the problems of large-scale distribution, transportation and storage of renewable energy in Northwest China, an integrated system of light-storage-hydrogen-methanol was designed for high proportion of renewable energy consumption. Firstly, the mathematical model of the system was constructed and linearized by McCormick method with the aim of maximizing the total annual revenue of the system. Secondly, based on the annual data, the optimal equipment capacities and run schedules were determined. Finally, the influences of methanol price, oxygen price, carbon price and equipment cost on total income were analyzed. Results show that through the joint design and dispatching optimization, the new light-storage-hydrogen-methanol integrated system can utilize renewable energy by a wide margin and maintain the stable production of methanol without increasing the power grid pressure. Meanwhile, the system has initial economic benefits. With the increase of methanol price and the decrease of equipment cost, the economic benefits of the system can be further improved.
  • New Energy Resources and Energy Storage
    Simulation and Performance Analysis of Solar-assisted PVT Heat Pump System in Different Areas
    LU Wanglin, CHEN Pei, LU Qiliang, BAO Jiaqi, LIU Wenjie, DAI Yanjun
    2023, 43(11): 1487-1493. https://doi.org/10.19805/j.cnki.jcspe.2023.11.014
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    In order to reveal the effect of the temporal-spatial variation of the environmental conditions on the performance of the solar-assisted direct expansion photovoltaic-thermal(PVT) heat pump, the mathematical modelling and simulation were conducted. The performance of the PVT heat pump within the heating season in different areas was analyzed. Results show that the average evaporation temperature of the PVT heat pump system is enhanced to the level near to, even over the ambient temperature due to the solar irradiation, which improves the thermodynamic performance considerably. When the condensing temperature is 50 ℃, the average COP during the heating season in Beijing, Lhasa, and Lanzhou is 3.67, 5.01 and 3.41 respectively, the average heat gain power of a single module is 541 W, 810 W and 504 W respectively, and the heat gain factor is 71.7%, 62.0% and 79.3% respectively, the power generation benefit is 4.76%, 8.67% and 6.10% respectively.
    • Digitalization and Intelligentization
  • Digitalization and Intelligentization
    Research on a Self-coupling PID Control Strategy for Reactor Core Power
    LU Yuanxu, ZENG Zhezhao, TANG Lijun, BAI Jiazan
    2023, 43(11): 1494-1499. https://doi.org/10.19805/j.cnki.jcspe.2023.11.015
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    To solve the control problems of nonlinear control of reactor core power, a self-coupling proportional-integral-differential (SCPID) control method was proposed. In this method, all the known or unknown complex factors and external disturbances in the system were defined as a total disturbance, and the controlled error system was established with the total disturbance as the excitation. Then, the core power control system based on SCPID control theory was designed, and the stability of the closed-loop control system in the complex frequency domain was rigorously analyzed and proved. Results show that compared with other methods, the control method of SCPID is simple and efficient, and has practical application value in the field of reactor core power system control.
  • Digitalization and Intelligentization
    Rolling Bearing Fault Diagnosis Based on VMD and Improved DenseNet
    DONG Lunan, DENG Aidong, FAN Yongsheng, LIU Yang
    2023, 43(11): 1500-1505. https://doi.org/10.19805/j.cnki.jcspe.2023.11.016
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    In view of traditional fault diagnosis methods have poor anti-noise performance and insufficient fault information mining in vibration signals, a rolling bearing fault diagnosis model was proposed based on variational mode decomposition (VMD) and dense connection network (DenseNet). Firstly, VMD was used to decompose the vibration signal containing noise into multiple intrinsic modal components. Some components with greater relevant to the original signal were selected and reconstructed. The signal was obtained after noise reduction. Then, the reconstructed signal was sent to DenseNet network to extract features. by increasing the channel attention mechanism, different weights were given to different extracted features to further strengthen the discrimination of features. Finally, fault classification was finished according to Softmax layer. Results show that this model can extract fault features effectively from vibration signals with different intensity noise. It has good diagnostic performance.
  • Digitalization and Intelligentization
    Rotor Crack Parameter Identification Based on Kriging Combined Model and NSGA-III Algorithm
    HU Kai, MA Jun, WANG Xiaodong, CHEN Hongchao
    2023, 43(11): 1506-1514. https://doi.org/10.19805/j.cnki.jcspe.2023.11.017
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    In order to solve the problem of insufficient quantitative identification accuracy of rotor crack parameters, a rotor crack parameter identification method based on Kriging combined model and non-dominated solution sequencing genetic algorithm type III (NSGA-III) was proposed. Firstly, Kriging conbined models with different correlation functions were established as the candidate model library based on the dynamic model response. Secondly, the model with poor performance was eliminated by the stepwise regression model screening strategy, and the optimal Kriging combined model was obtained according to the heuristic weight weighting. Thirdly, the relationship between the crack parameters and the response of the cracked rotor system was established by using the proposed Kriging combined model. Finally, a multi-objective function was constituted according to the difference between the predicted response amplitude of Kriging combined model and the actual response, and the recognition results were obtained by NSGA-III. Results show that the maximum error of crack parameter identification by this method is 2.5%. Compared with the recognition method based on single Kriging model and exponential function-Gaussian function combined model, the proposed method has higher applicability and accuracy.
    • Integrated Energy System
  • Integrated Energy System
    Research on Load Optimal Distribution Strategy of Combined Heat and Power System Based on Improved Gray Wolf Algorithm
    DING Heng, HU Hui, CAO Yue, SUN Jian, SI Fengqi
    2023, 43(11): 1515-1522. https://doi.org/10.19805/j.cnki.jcspe.2023.11.018
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    In order to study the optimal distribution strategies of thermoelectric load in combined heat and power (CHP) system and solve the time-delay problems caused by the tedious updating mechanism in the traditional gray wolf optimization algorithm, an improved multi-objective gray wolf algorithm (MOGGWO) was proposed. The evolution process was completed directly by using the position of the top three wolves and Gaussian sampling. The improved algorithm was applied to the multi-objective optimal distribution of thermoelectric load in the CHP system consisting of two 600 MW units. Results show that the improved multi-objective gray wolf algorithm can greatly shorten the solving time of load distribution, and while improving the system economy, its renewable energy absorption capacity will be weakened. Therefore, the optimal distribution strategy of thermoelectric load should be selected according to the actual situation on site.
  • Integrated Energy System
    Comparative Study on Load Cycling and Transient Performance of Different Wide-load Denitration Systems
    GAO Guobin, GAO Wei, ZHANG Junliang, LIU Ming, YAN Junjie
    2023, 43(11): 1523-1530. https://doi.org/10.19805/j.cnki.jcspe.2023.11.019
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    The load cycling and transient performance were obtained when different wide-load denitration schemes were adopted, i.e., No.0 high pressure heater, feed water bypass of economizer and flue gas bypass of economizer. Results show that: at 30%THA -100%THA load, the enhancement of SCR system inlet temperature is the largest using economizer flue-gas bypass on the low-temperature superheater side, reaching 31.2 K on average when the bypass flow is 50%. The standard coal consumption rates increase when economizer bypass schemes are adopted. By adopting economizer flue-gas bypass on the low-temperature superheater and low-temperature reheater sides, the improvement of SCR system inlet temperature can reach 42.16 K and 27.56 K, respectively, when the average standard coal consumption rate is increased by 1 g/(kW·h). The lag time of SCR system inlet temperature is very short and the change rate is high, reaching 34.65 K/min when economizer flue-gas bypass on low-temperature superheater side is adopted. Moreover, the temperature change at the inlet of the SCR system has a lag about 1 min when the No.0 high pressure heater is put into operation, and the average power change rate reaches 10.22 MW/min.