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    Fundamental Research
  • Fundamental Research
    Study on the Abnormal Heat Transfer Characteristics of CO2 Under Supercritical Pressure in Horizontal Tubes
    SU Shiyu, JIANG Wenquan, LI Lin, SHI Jiefeng, LI Yang, YANG Fan
    2022, 42(12): 1167-1173. https://doi.org/10.19805/j.cnki.jcspe.2022.12.001
    Abstract ( ) Download PDF ( )   Knowledge map   Save
    The FLUENT software was used to numerically simulate the heat transfer characteristics of CO2 in a horizontal tube with the diameter of 4 mm and the length of 1 000 mm under supercritical pressure. First, the effect of heat flux on heat transfer was analyzed, indicating that under the condition of mass flow of 140 kg/(m2·s), the top and bottom walls presented a large temperature difference and showed the abnormal characteristics of heat transfer behaviour. Then two kinds of buoyancy criteria were compared and evaluated, and the effect of pressure on buoyancy was analyzed. Finally, the heat transfer characteristics of the horizontal tube walls were revealed via a study on the distributions of profiles' physical properties. Results show that the larger the heat fluxes are, the more obvious the deterioration of heat transfer and the stronger the buoyancy effect will be achieved. The BP criterion can better predict the buoyancy distribution under above conditions. Besides, the wall temperature difference can reflect the strength of buoyancy. Increasing pressure can mitigate the changes of CO2 physical properties and decrease the effect of buoyancy.
  • Fundamental Research
    Numerical Simulation of Flow and Heat Transfer Characteristics of S-CO2 in Plate Diffusion Welded Rectangular Micro-channel Heat Exchanger
    LI Hong, REN Yan, ZHANG Lixin, GAO Ming, LIU Jingnan, YANG Qiguo
    2022, 42(12): 1174-1182. https://doi.org/10.19805/j.cnki.jcspe.2022.12.002
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    Based on a plate diffusion welded rectangular micro-channel heat exchanger with convenient and efficient processing technology, a mathematic-physical model of the heat transfer unit of hot and cold straight channels was established, and the flow and heat transfer characteristics of supercritical carbon dioxide(S-CO2) under different boundary conditions and different channel structures were investigated. Results show that with the increase of Reynolds number(Re), the turbulences in the hot and cold straight channels enhance, the heat transfer performance improves, and the frictional resistance coefficient of the flow decreases. Compared with the flow and heat transfer characteristics in the rectangular channel with no grid, the turbulence effect and heat transfer characteristic are the best when the grid is horizontally arranged on both sides of the channels, and the comprehensive heat transfer enhancement factor (PEC) of the channel is relatively high. However, the PEC still needs to be further improved compared with that of the semi-circular channel.
    • Power Equipment and System
  • Power Equipment and System
    Numerical Simulation of Two-phase Flow Characteristics of Pulverized Coal Distributor
    SHI Quancheng, Lü Weizhi, ZHOU Wentai, HE Xiang, WANG Xin, FAN Weidong
    2022, 42(12): 1183-1190. https://doi.org/10.19805/j.cnki.jcspe.2022.12.003
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    In order to solve the problem of uneven distribution and large concentration deviation of air powder in coal-fired units, an air powder two-phase adjustable coal powder distributor was designed. It was equipped with a special shaped pipe at the elbow, which can improve the distribution characteristics of air powder. Numerical simulation was carried out on the two-phase flow characteristics of pulverized coal distributor, and the distribution of separation efficiency, pressure loss, wear, velocity field and concentration field was studied. Results show that the distribution deviation of air powder can be kept below 10% or even 5% by using the special-shaped coal powder distributor, and the wear mostly occurs in each branch of thick and thin phase and the resistance coefficient is very low. It is beneficial to realize the uniform distribution of primary air powder, ensure the stability and safety of unit operation, and meet the trend of flexibility transformation of coal-fired unit.
  • Power Equipment and System
    Simulation Research on Influence of Deflector on the Aerodynamic Noise Characteristics of a Flue in Thermal Power Plant
    HUANG Ruling, LI Guanpeng, WANG Zhaoyang, AN Chunguo, GUO Chang, GAO Ming
    2022, 42(12): 1191-1197. https://doi.org/10.19805/j.cnki.jcspe.2022.12.004
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    In view of the aerodynamic noise problem of a flue duct after the induced draft fan of a power plant, a numerical simulation was conducted based on Fluent, and the method combining large-eddy simulation and FW-H equation was adopted to analyze the aerodynamic noise at the monitoring points outside the pipe, and then the different optimization schemes were achieved. Results show that when increasing the cross-sectional area of the pipe, a high turbulent kinetic energy area will appear near the wall after the flue gas enters the flue. And the installation of deflectors can improve the uniformity of flow distribution and reduce the turbulent kinetic energy at the bend. When the two assemblies installed in the first and second bends both contain two deflectors, the noise reduction is relatively effective. Compared with the original flue containing eight and six deflectors, the average total sound pressure level of aerodynamic noise is reduced by 4.8%.
  • Power Equipment and System
    Comparative and Predictive Analysis on Calculation Methods of Steam Turbine Rotor Equivalent Stress
    LI Wangfan, XU Jiamin, LI Siqi
    2022, 42(12): 1198-1205. https://doi.org/10.19805/j.cnki.jcspe.2022.12.005
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    To improve the calculation accuracy of online monitoring of steam turbine rotor stress, the simplified calculation methods of the stress field and the temperature field were systematically proposed. Taking the high-pressure rotor of the 300 MW turbo-generator as an example, the temperature field and stress field under cold starting conditions were analyzed by simplified calculation methods and a finite element software. The equivalent stress of the dangerous part was predicted by introducing a correction coefficient. Results show that comparing the results obtained by simplified calculation methods with the results obtained by the finite element software, the maximum deviations of the rotor outer surface and inner temperature appear in the initial stage of cold starting, and the outer surface equivalent stress has a large deviation in the initial stage and later stage of cold starting.The predicted results were in good agreement with the simulation results of finite element software by using the support vector regression(SVR)based on cross-validation, which could meet the accuracy standards of engineering practice.
  • Power Equipment and System
    Experimental and Numerical Study on Influence of Balance Hole on Aerodynamic Performance of Axial Flow Turbine
    ZHONG Zhuhai, SUN Qi
    2022, 42(12): 1206-1212. https://doi.org/10.19805/j.cnki.jcspe.2022.12.006
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    An experimental study on the influence of the variation of balance hole area on the aerodynamic performance of turbine was carried out with a three-stage air turbine test bench. Numerical calculation and analysis of the test turbine stage were carried out, and the rule of the turbine stage performance change with the balance hole area was studied, and the numerical results were compared with the test results.Results show that the stage efficiency is the lowest when there is no balance hole, and for the balance hole with diameter less than 25 mm, the stage efficiency increases with the increase of balance hole diameter, and then decreases gradually. The calculated efficiency change rule is in good agreement with the experimental results. The efficiency is optimal when the leakage area ratio between the balance hole and the diaphragm seal is 2-3.
  • Power Equipment and System
    Mechanical Integrity Analysis of Heavy-duty Gas Turbines
    SHU Guogang, CHEN Jian, ZHANG Xiaoyi, FAN Wei, SONG Zhiqiang, WEI Zeming, WU Hong
    2022, 42(12): 1213-1222. https://doi.org/10.19805/j.cnki.jcspe.2022.12.007
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    From the perspective of ensuring structural reliability and safety, mechanical integrity analysis and validation methods of heavy-duty gas turbines were summarized. Based on material failure modes and damage mechanisms under severe service environments, the analyses of mechanical integrity, rotor and whole machine dynamics, and machine clearance design were conducted. The procedures and tasks of mechanical integrity analysis of gas turbine main components, the important role of testing and evaluation methods of mechanical integrity analysis, and the root cause analysis of the field issues on commercial units were systematically discussed, which can provide a complete set of verification and validation methods for reliability and safety of gas turbine structures.
  • Power Equipment and System
    Robustness Analysis of Shaped Holes in Near-wall Vortical Flow
    BAO Amei, CHEN Liu, DAI Ren
    2022, 42(12): 1223-1229. https://doi.org/10.19805/j.cnki.jcspe.2022.12.008
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    In a flat-plate ejection model, vortex generator (VG) was used to simulate the complex near-wall vortex flow in the cascade flow field, and adiabatic film cooling effectiveness and the change rate of film coverage area of fan-shapedand NEKOMIMI holes were studied. The robustness of fan-shaped and NEKOMIMI holes was analyzed in near-wall vortex current environment. Results show that the streamwise vortex is mixed with the anti-kidney vortex downstream of the film hole, thus lifting the anti-kidney vortex and reducing the film cooling efficiency. NEKOMIMI film hole produces more stable anti-kidney vortex which prevent it to be rolled up by the near-wall vortex. Within the blowing ratio range from 1.0 to 2.0, the area-averaged cooling efficiencies of fan-shaped hole and NEKOMIMI hole are respectively decreased by 9.3%-12.9% and 1.0%-2.7%. The effective coverage is reduced by 14.2%-29.0% for the fan shaped hole while 1.9%-4.6% for the NEKOMIMI hole. Therefore, NEKOMIMI hole has performed better robustness in a complex flow with streamwise vortex.
  • Power Equipment and System
    Structure Optimization Analysis and Experimental Verification of a Swirl Nozzle
    PU Chenghao, DING Zhiwei, SHEN Yuanxian, SHI Dong
    2022, 42(12): 1230-1236. https://doi.org/10.19805/j.cnki.jcspe.2022.12.009
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    Volume of fraction (VOF) method was used to analyze the internal flow field of a swirl nozzle, and a simulation and experimental schemes were designed. The structure optimization design of a nuclear power plant regulator nozzle with rated pressure drop of 40.8 kPa, rated flow rate of 11.38 kg/s and spray angle of 80° was carried out. Results show that the flow field in the swirl nozzle has the characteristics of vortex motion, and the structure of the swirl core plays a decisive role in the pressure and velocity field in the nozzle. Groove depth is the most critical factor in the formation of hollow conical spray.The spray angle and particle size can be optimized by increasing the number of grooves, the depth of grooves and the spiral angle. If necessary, the spray uniformity can be significantly improved by adding additional fluid channel. The flow and pressure drop characteristics of the nozzle meet Bernoulli equation, and the experimental results are in good agreement with the numerical simulation results. The numerical method for design of spray characteristics can save the test iteration in the trial-manufacture stage of the swirl nozzle, and provide ideas for the design of similar nozzles in various industrial applications.
    • New Energy Resources and Energy Storage
  • New Energy Resources and Energy Storage
    Performance Analysis and Multi-scenario Decision of Cogeneration System Combined with Gasifier Under Different Mixing Ratios
    YAN Zhiquan, GU Xinzhuang, JIA Teng
    2022, 42(12): 1237-1245. https://doi.org/10.19805/j.cnki.jcspe.2022.12.010
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    The gasification cogeneration system using biomass feedstocks as input energy has the potential to generate clean heating in rural areas of northern China and meets the "carbon neutralization" target. The performance of three kinds of typical biomass feedstocks (corn cob, wheat straw and bark) under different mixing ratios was compared and analyzed, and the suggestions of corresponding mixing ratios under different scenarios using performance evaluation index as a reference were proposed. Results show that the optimal air equivalence ratio (0.325) can be acquired at the mixing ratio (B) of 5∶5∶5, and the corresponding cold gas efficiency is 79.65%. The highest calorific value of syngas is 4.691 MJ/m3 at the mixing ratio of 1∶5∶1, while the lowest biomass feedstock consumption is 20.1 kg/h at the mixing ratio of 1∶5∶10. The highest waste heat of jacket water and exhaust gas are 15.94 kW and 17.6 kW at the mixing ratio of 1∶5∶10, meanwhile the highest cooling capacity is 6 kW. For the application scenario with high energy efficiency requirements but insensitive to price, the recommended mixing ratio is 1∶5∶10, and corresponding energy and exergy efficiency are 22.24% and 15.44% respectively.
  • New Energy Resources and Energy Storage
    Influence of Surface Riblets on the Aerodynamic Performance of Wind Turbine Airfoils
    NIU Zhigang, LUO Dahai, WANG Ziyao
    2022, 42(12): 1246-1254. https://doi.org/10.19805/j.cnki.jcspe.2022.12.011
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    The aerodynamic performance of several wind turbine airfoils with longitudinally arranged surface riblets was studied by numerical simulation method. Based on the transition SST model and using commercial computational fluid dynamics (CFD) software, the drag reduction effects of two different types of L-shaped and V-shaped riblets were studied. The effect of riblets on the lift and drag characteristics of wind turbine airfoils was also studied, considering the variation of Reynolds number and airfoil geometry. By comparing the lift and drag coefficients, together with the surface friction coefficient, the drag reduction mechanism of surface riblets for wind turbine airfoils was discussed. Results show that under the condition of optimal riblet geometric parameters, L-shaped riblets have better drag reduction effect than V-shaped riblets, and the maximum drag reduction rate for the DU airfoil reaches up to 5.6%. Using the optimal geometric parameters, surface riblets have drag reduction effects in a wide range of Reynolds number and angle of attack.
  • New Energy Resources and Energy Storage
    Research on Dynamic Characteristics of Offshore Wind Turbine Tower Considering the Coupling of Blade Rotation and Soil-Structure Interaction
    FAN Ang, LI Luping, OUYANG Minnan, CHEN Shangnian
    2022, 42(12): 1255-1264. https://doi.org/10.19805/j.cnki.jcspe.2022.12.012
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    Based on Ansys finite element software, a three-dimensional solid modeling of the tower system of the NREL 5 MW monopile offshore wind turbine was conducted, and the influence of the blade rotation state and soil-structure interaction on the vibration characteristics of the tower was analyzed. Results show that considering the centrifugal force and centrifugal stiffness generated by the blade rotation, the soil-structure interaction can significantly reduce the first two modal frequencies of the tower, and the relative variation of the first two modal frequencies are -31.68% and -31.74%, respectively. At the same time, the transient displacement response value of the tower increases,and the maximum displacement of the tower top in fore-and-aft and lateral directions can be increased by 86.94% and 46.59% respectively compared with the fixed constraint at the bottom. Under the combined action of blade rotation and soil-structure interaction, the equivalent stress of the tower increases significantly, and the maximum equivalent stress can be increased by 57.38%; the first and second order modal frequencies will resonate with the blade 1P rotation frequency when the speed reaches around 9.5 r/min, and will not resonate with the blade 3P rotation frequency within the rated speed.
    • Integrated Energy System
  • Integrated Energy System
    Correlation Analysis of Inlet Dryness and Aerodynamic Performance of Supercritical Carbon Dioxide Compressor
    ZHOU Miaoqin, ZHANG Jingxuan, HUANG Weiguang
    2022, 42(12): 1265-1271. https://doi.org/10.19805/j.cnki.jcspe.2022.12.013
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    A numerical study was simulated on the impact of inlet dryness on the aerodynamic performance of supercritical carbon dioxide compressor, and the morphological feature of tip clearance flow under different inlet dryness was emphatically compared and analyzed. Results show that with the decrease of the inlet dryness, the mass flow rate at the maximum efficiency scenario, the peak efficiency, the pressure ratio and the surge margin increase. At design flow rate and low flow rate conditions, the efficiency decreases with the decrease of inlet dryness. At the condition of high flow rate, the efficiency increases with the decrease of inlet dryness. When tip clearance is 5% of inlet blade height at the same conditions, the smaller the inlet dryness is, the stronger the tip leakage flow will be, and the "secondary leakage" is easier to be formed.
  • Integrated Energy System
    A Comprehensive Thermodynamic Analysis of CHP Unit Incorporating Thermal Energy Storage for District Heating Network
    HE Ye, LI Chao, GAO Jiasheng, ZHOU Yan
    2022, 42(12): 1272-1280. https://doi.org/10.19805/j.cnki.jcspe.2022.12.014
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    In order to improve the problem of surplus heat in the oversaturation period and insufficient heat supply in the unsaturated period, an auxiliary thermal energy storage system was integrated on a 600 MW coal-fired CHP unit. The thermal economy of the comprehensive heating system was evaluated by using two indexes of thermal saturation and heating deviation, and the global energy flow analysis and the exergy analysis of the local district heating system were conducted. Results show that without reducing the power output of the whole system, it could increase the heat saturation of the heating to 100% meanwhile reduce the heating deviation by 0.98%.The lower the outdoor temperature is, the more obvious the advantages of the integrated heating system will be.