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  • Effects of Channel Height on the Thermal-Hydraulic Performance of Airfoil Fin Printed Circuit Heat Exchanger
    LI Debo, JIN Wanlong, CHEN Zhaoli, CHEN Zhihao, SONG Jinghui, LEI Xianliang, DENG Lei, CHE Defu
    2024, 44(6): 837-843. https://doi.org/10.19805/j.cnki.jcspe.2024.230268
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    The effect of channel height on the thermal-hydraulic performance of airfoil fin printed circuit heat exchangers(PCHEs) was investigated by numerical method based on the impact of channel geometry. Results show that channel height significantly affects the compactness, resistance, and heat transfer performance of PCHE. Under the same Reynolds number (Re=6 000-14 000), the Fanning friction factor f first decreases and then increasesas with the channel height H decreases (i.e., the ratio of channel height to transverse pitch H/ST=0.12-0.60), with the lowest f observed at H/ST=0.24. The Colburn-j factor j shows no significant change for airfoil fin channels with H/ST=0.24-0.60, while an increase in j is observed at H/ST=0.12. The ratio j/f is suitable for evaluating the comprehensive performance of airfoil fin channels with different heights. When using j/f as the comprehensive performance evaluation indicator, the airfoil fin channel with H/ST=0.24 exhibits the best overall performance.
  • Chemical Reaction Kinetics Analysis of NO Generation in Gas Phase of Ammonia-Coal Co-firing
    KANG Zhizhong, ZHANG Zhenzhuo, DING Xian, ZHAO Hujun, SUN Zhe
    2024, 44(6): 844-850. https://doi.org/10.19805/j.cnki.jcspe.2024.230271
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    Ammonia-coal co-firing involves complex chemical reaction processes, and it is highly concerned that whether co-firing exacerbates the generation of nitrogen oxides. Using the method of chemical reaction kinetics calculation, the reaction pathways of NO generation and reduction in the gas-phase reaction of ammonia-coal co-firing were studied, as well as the effects of different factors on NO generation. Results show that compared to pure coal combustion, the NO volume fraction at the outlet of the reactor can be reduced by 96.5% with the ammonia co-firing ratio of 0.3 at temperature (T) of 1 300 ℃ and excess air coefficient (α) of 0.84. Since ammonia decomposition generates a large number of free radicals such as NH2 and NH, which leads to a faster reduction reaction rate and the conversion of N-containing elements into N2 under co-firing working condition. At T=1 300 ℃, an ammonia co-firing ratio of 0.3 is suitable, since the volume fractions of NO and NH3 at the reactor outlet are both low. Small ammonia co-firing ratio will increase the rate of NO generation and NH3 decomposition, leading to an increase in NO volume fractions at the reactor outlet. The higher the temperature is, the more obvious this phenomenon is. Reducing atmosphere (α<1) and a lower temperature (T≤ 1 300 ℃) can effectively reduce NO emissions.
  • Comparative Study on Performance of High Level Water Collection Mechanical Draft Cooling Tower Based on External Cooling and Internal Condensation Modules
    LONG Guoqing, ZHANG Guogang, DENG Weipeng, SUN Fengzhong
    2024, 44(6): 851-858. https://doi.org/10.19805/j.cnki.jcspe.2024.230157
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    To control plumes and save water resources, a hot test system for high level water collection mechanical cooling tower was established for comparative analysis of the plume abatement, water saving and thermal performance of the external cooling module (dry-wet hybrid cooling tower) and the internal condensation module (condensation plume cooling tower). The impact of the ambient temperature, inlet circulating water temperature and circulating water flow rate on the performance of cooling towers was studied. Results show that dry-wet hybrid cooling tower and condensation plume cooling tower have plume abatement and water saving capabilities, which are achieved at the cost of cooling performance reduction of the cooling tower. Compared with the original tower, the circulating water temperature drop of dry-wet hybrid cooling tower and condensation plume cooling tower decreases by about 1.5 K. The plume abatement and water saving performance of the dry-wet hybrid cooling tower and the condensation plume cooling tower is greatly affected by the operating parameters, and the water saving amount and water saving rate of the condensation plume cooling tower are higher than those of the dry-wet hybrid cooling tower.
  • Identification Method of Torsional Vibration Characteristics of Pumped Storage Units Under Hydraulic Pulsation
    MA Yunxiang, LIU Xiaofeng, HE Xiaofeng, PENG Hui, CAO Yang
    2024, 44(6): 859-864. https://doi.org/10.19805/j.cnki.jcspe.2024.230033
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    A torsional vibration identification method for shafting of pumped storage unit based on hydraulic pulsation was proposed. The dynamic random torque signal was obtained by using strain measurement technology. Setting the trigger threshold, a group of sample signals was obtained by using the intersection point of the signal, the threshold and the points of a certain length. After averaging a sufficient number of sampled signals, the random response and positive/negative velocity impact response were averaged out, and the remaining signal was the amplitude impact response signal. The torsional natural frequency and damping could be obtained by fitting the impact response signal with exponential function. The method was applied to identify the torsional characteristics of a pumped storage unit. The test results show that the hydraulic fluctuation is larger under 25% load condition. The trigger threshold has little influence on the identification results. When the load increases, the torque pulsation decreases. The trigger threshold has little effect on the identified frequency, but it will affect the identified damping. This method does not need to apply torque excitation. It realizes the identification of torsional vibration characteristics under installation conditions, which has a good engineering application value.
  • Numerical Simulation of Thermal and Hydraulic Characteristics of Fuel Assembly Affected by Surface Punching
    LI Chen, WANG Hui, YING Qifan, DIAO Yongfa
    2024, 44(6): 865-871. https://doi.org/10.19805/j.cnki.jcspe.2024.230237
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    Using numerical simulation methods, the thermodynamic and hydraulic parameters in the fuel bundle channel, especially downstream of the positioning grid, were calculated under different Reynolds number conditions. The effects of different punching models on the velocity and turbulence intensity in the downstream of the positioning grid were analyzed from the aspects of pressure drop, Nusselt number and comprehensive local heat transfer factor, and the optimal punching area within different Reynolds number ranges was calculated. Results show that when the Reynolds number is not less than 5 871, compared with the unperforated model, the perforated model can effectively reduce the pressure drop in the downstream section. When the Reynolds number is greater than 6 605, punching holes on the surface of the turbulent blade can reduce the longitudinal vorticity at the blade outlet, which leads to a decrease in the Nusselt number in the far field of the downstream flow field. When the Reynolds number is less than 7 339, the comprehensive heat transfer factor increases the most when the punching area ratio is 15%. However, when the Reynolds number is greater than 7 339, the local comprehensive heat transfer coefficient in the downstream far-field will gradually decrease with the increase of punching area.
  • Principles and Research Progress of Biohydrogen Production
    CHEN Hongwei, FU Yufei, SONG Yangfan, GUO Chenghao, SHI Ruipeng, WANG Meng, XU Youbo
    2024, 44(6): 872-885. https://doi.org/10.19805/j.cnki.jcspe.2024.230241
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    Biohydrogen production technologies such as photolysis of water, photo fermentation, dark fermentation, and coupled dark-photo-fermentation were mainly reviewed. The hydrogen production mechanism, technological advantages and disadvantages, influencing factors and research status of each method were analyzed. At the same time, the types and characteristics of biohydrogen production reactors were compared. The results show that biohydrogen production has great potential in low-grade energy treatment and advanced energy production. Finally, some suggestions on the development of biohydrogen production technology were given.
  • Knowledge Graph Construction Method for Wind Turbine Operation and Maintenance Data
    LI Xiaolu, WANG Ke, ZHAO Bing, LIAO Wenyu
    2024, 44(6): 886-894. https://doi.org/10.19805/j.cnki.jcspe.2024.230235
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    In response to the challenges faced in the digital and intelligent operation and maintenance (O&M) of wind turbines, such as data overload of multiple units, information redundancy, low efficiency in maintenance knowledge retrieval and insufficient reasoning of life-cycle maintenance knowledge, a knowledge graph construction method for wind turbine operation and maintenance data was proposed. Firstly, important information such as faulty components and causes could be extracted using text data such as wind turbine equipment maintenance work orders, so as to provide the knowledge graph construction process for wind turbine operation and maintenance data.Subsequently, during the construction process, modeling analysis was conducted specifically for fault entities, attribute extraction and relationship extraction. Results show that the wind turbine O&M knowledge graph helps O&M personnel to accurately grasp the root causes of failures, efficiently implement maintenance measures, and ensure the repair capabilities of wind turbines under the conditions of informatization and intelligence. Moreover, compared to relational databases, the proposed design method offers better performance in terms of query precision and time.
  • Numerical Study of Aerodynamic Performance of Bionic Flap Airfoil with Mako Shark Tail-fin
    SU Shunlong, YE Xuemin, WU Yingming, LI Chunxi
    2024, 44(6): 895-904. https://doi.org/10.19805/j.cnki.jcspe.2024.230319
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    To further improve the aerodynamic performance of airfoils, a bionic curved flap was proposed based on the trail fin profile of mako sharks. The aerodynamic performance and internal flow of the bionic airfoil were simulated using the SST k-ω turbulence model, and the effects of relative position and installation angle of the bionic flap were analyzed to obtain the optimal bionic flap airfoil with the best aerodynamics, which was compared to the Gurney flaps. Results show that after installing a bionic flap, its lift-drag ratio is significantly higher than the baseline; when the relative flap height remains unchanged, reducing the installation angle and increasing the distance between the flap and the trailing edge lead to an early airfoil stall onset. The aerodynamic performance of the bionic flap airfoil with reverse installation angle of 45° at the trailing edge is the best, and the lift coefficient is 5.9% higher than the Gurney flap airfoil before the stall. After arranging the bionic flap, the flow field tends to be complicated, and the position, quantity and size of vortices change.
  • Experimental Study on Three-dimensional Flat Plate Heat Pipe Enhancing the Thermoelectric Generation Performance
    LI Dashu, DING Yiwen, ZHANG Chengbin
    2024, 44(6): 905-910. https://doi.org/10.19805/j.cnki.jcspe.2024.230288
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    To improve the power generation efficiency of the thermoelectric power generation device, a method for enhancing the performance of three-dimensional flat plate heat pipes was proposed. The effects of the two liquid filling rates on the thermal performance of the three-dimensional flat heat pipe were compared and evaluated by experiments, and the maximum output power and power generation efficiency of the thermoelectric power generation system under different temperature differences were explored. Results show that when the liquid filling rate is 27.4%, the three-dimensional flat heat pipe start-up process is staged start-up and the temperature stratification is significant. When the liquid filling rate is 31.7%, the three-dimensional flat heat pipe can be quickly activated at around 40 ℃, and the temperature distribution uniformity and consistency are good after start-up, which is conducive to the sustained, stable and efficient power generation of the thermoelectric power generation system. The maximum output power and power generation efficiency of the thermoelectric power generation system strengthened by three-dimensional flat plate heat pipes increase with the increase of the temperature difference, and the thermoelectric power generation efficiency can reach up to 3.99%.
  • Energy Storage Prediction of Photovoltaic-Concentrating Solar Power System Based on Model and Data
    TIAN Liang, WANG Guanjie
    2024, 44(6): 911-918. https://doi.org/10.19805/j.cnki.jcspe.2024.230290
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    A model-data joint prediction method was proposed. The object dynamic model was established through mechanism analysis, and the future solar radiation intensity and user load prediction data were introduced for immediate model prediction. The data prediction model was established through the convolution - short and long time memory hybrid neural network improved by attention mechanism, and the historical data was introduced for rolling data prediction. Then, Kalman filter was used to combine the output of the two prediction models to realize the joint prediction of energy storage. Results show that the combined prediction has the advantages of both methods, which can solve the problem of accumulated energy storage prediction errors over time and timely characterize the changes of energy storage when meteorological factors suddenly change and system operation mode changes. The proposed method has good prediction accuracy under various weather conditions.
  • Secondary Frequency Control Strategy Assisted by Flywheel Energy Storage Considering Operation Stability of Thermal Power Plant
    ZHANG Wenzheng, WANG Wei, GAO Song, LI Yihuan, CHEN Biao, FANG Fang
    2024, 44(6): 919-929. https://doi.org/10.19805/j.cnki.jcspe.2024.230279
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    To solve the issue of un-stable operation of thermal power units caused by severe fluctuations in the power grid, a secondary frequency regulation control strategy assisted by flywheel energy storage considering the operation stability of thermal power plant was proposed. Firstly, a secondary frequency regulation control model for ultra-supercritical thermal power units integrated with the flywheel energy storage was developed. Then, a non-linear decomposition method for AGC instructions based on constraints of multi-layer variable gain rates was proposed. Finally, a fitness function was designed based on the unit stability and the AGC performance of the system, and the whale optimization algorithm (WOA) was used to obtain the optimal parameters of limiting algorithm. Based on the above method, a collaborative control strategy of secondary frequency regulation was designed for the integrated system of thermal power unit and energy storage. A simulation verification was conducted on the integrated system with a 1 000 MW thermal power unit and flywheel energy storage as an example. The results show that the proposed control strategy can effectively respond to high-frequency commands of the integrated system without affecting the frequency regulation performance, reduce the action amplitude of thermal power unit, and improve the stability of power unit operation.
  • Research on Covert Attack Method in Nuclear Power Plant Based on SOS-LSTM
    WANG Dongfeng, ZHANG Xiong, HUANG Yu, DENG Jianyong, GUO Feng
    2024, 44(6): 930-938. https://doi.org/10.19805/j.cnki.jcspe.2024.230073
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    A covert attack method based on a symbiotic organism search(SOS) algorithm to optimize long short-term memory (LSTM) neural network was proposed to solve the problem of obtaining a high-precision estimation model of the attacked target for covert attacks. The output and input signals of the feedback controller of the attack target were taken as the data set of the LSTM. The estimation model of the attacked area was obtained through training, and was used to design the covert attacker to impose attack signals on the attacked object.In addition, the SOS algorithm was applied to optimize the parameters of the LSTM to improve the performance of the covert attacker.The simulation results of covert attack on the primary circuit control system of nuclear power plant show that the attack method has high concealment performance while realizing preset attack behavior on the output signal of the target control system.
  • Fault Warning of Coal Mill Based on IWOA-Transformer
    LUO Yi, DUAN Mingda
    2024, 44(6): 939-946. https://doi.org/10.19805/j.cnki.jcspe.2024.230356
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    A fault warning method based on the improved whale algorithm to optimize the hyperparameters of Transformer network (IWOA-Transformer) was proposed. The method improved the whale optimization algorithm (WOA) by utilizing nonlinear convergence coefficients and Gaussian variation to improve its convergence speed and avoided falling into local optimum. Then, the hyperparameters of Transformer were optimized with the improved whale optimization algorithm (IWOA) to establish a fault warning model of coal mill, and the adaptive threshold was determined by the similarity function of predicted and actual values. Combined with the expert system, the fault type was judged and solutions were proposed,and coal mill fault early warning was achieved. Finally, A fault warning test was conducted using a 350 MW cogeneration unit medium-speed coal mill as an example. Results show that the IWOA-Transformer model can significantly improve the speed and accuracy of early warning, and has practical engineering value.
  • General Matrix Model of Carbon Emissions and Carbon Sensitivity of Thermal Power Units
    RAN Peng, WANG Jing, LI Zheng, LIU Xu, ZENG Qinghua, LI Weiqi
    2024, 44(6): 947-955. https://doi.org/10.19805/j.cnki.jcspe.2024.230205
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    In order to realize the simple and accurate measurement of carbon emissions of thermal power units and grasp the influence of operating factors on carbon emission intensity, basing on the emission factor method technology, referring to the traditional q-γ-τ matrix structure form, according to the needs of solving carbon emissions of thermal power units, and grasping the influence of operating parameters on carbon emission intensity of power generation, a general matrix model of carbon emissions and carbon sensitivity of thermal power units was established, and the matrix filling rules were determined. The accuracy of the model was verified by the heat balance method combined with the material balance algorithm, and the calculation results were compared with the emission factor method. The carbon emission of a thermal power unit for 24 h was calculated, and the disturbance ΔMCO2 of carbon emission intensity of power generation was analyzed when the smoke oxygen, main steam temperature and pressure fluctuated. Results show that, compared with the emission factor method, the proposed model can shorten the time span of carbon emission accounting and improve the accuracy of carbon emission accounting. The carbon emission of the unit for 24 h is 5 780.644 t; When the smoke oxygen is reduced by 0.1%, ΔMCO2 is 1.772 6 g/(kW·h); When the main steam temperature increases by 0.5 K, ΔMCO2 is 3.020 6 g/(kW·h); When the main steam pressure increases by 0.2 MPa, ΔMCO2 is 0.378 8 g/(kW·h).
  • Energy Consumption Assessment and Reaction Kinetics Analysis of Catalytic Amine-based Carbon Capture Technology
    JIANG Cong, GAO Ge, JIANG Wufeng, LI Xiaoshan, LUO Cong, ZHANG Liqi, WU Fan
    2024, 44(6): 956-963. https://doi.org/10.19805/j.cnki.jcspe.2024.230222
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    In order to alleviate the extensive energy consumption of amine-based carbon capture, nanoscale aluminum oxyhydroxide was applied as the catalyst to reduce the heat duty of amine regeneration. The desorption process was divided into a heating-up stage and an isothermal stage based on the basic heat transfer theory. An energy consumption assessment model for calculating the heat input during different stages was established, and the real-time heat duty variation curves were obtained. This model was more precise than conventional methods, and was beneficial for determining the optimal operation conditions to reach the lowest energy consumption. Based on this method, the best desorption temperatures to achieve the lowest heat duty with and without catalyst were investigated. Results show that moderate temperatures can bring the lowest energy consumption. Besides, through the analysis of the overall reaction kinetics during the regeneration process, it is found that the reaction order model is most suitable for describing the reaction rate of ethanolamine solution. The parameters of the reaction order model prove that the catalyst saves the energy consumption of regeneration by reducing the activation energy of the desorption reaction.
  • Study on Heat and Mass Transfer of Vertical Tube Falling Film Reboiler in CO2 Chemical Absorption System
    XU Lihua, DENG Feng, Lü Xun, LI Lanxi, WANG Tao, FANG Mengxiang
    2024, 44(6): 964-972. https://doi.org/10.19805/j.cnki.jcspe.2024.230023
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    To solve the problems of the high regenerationenergy consumption and the thermal degradation caused by prolonged high-temperature heating of absorber in CO2 chemical absorption system, a new type of tubular falling film reboiler was proposed. By analyzing the flow characteristics of falling film, a research was conducted on structural optimization design of liquid distributors. To verify the heat and mass transfer performance of the falling film reboiler and find the optimal operating parameters, a systematic thermal experiment was conducted on a 200 m3/h flue gas CO2 chemical absorption pilot platform. The experiment results of falling film flow reveal that the unevenness of the liquid distributor can be significantly reduced to 0.026 after optimizing the direct opening of the connecting tube and the aperture of the distribution slot. Results show that, with the increase of liquid phase flow velocity within the tubes and the transition between laminar and turbulent flow states, the overall heat transfer coefficient of the falling film reboiler initially decreases and then increases. Concurrently, as the mass flow rate of steam increasing from 60 kg/h to 70 kg/h and 80 kg/h, the regeneration rate can be increased from approximately 10% to approximately 20%, and with a peak of up to 24.7%, thereby promoting the secondary desorption of the amine solution. By increasing the steam flow rate and the inlet temperature of the amine solution, the heat flux of the falling film reboiler gradually increases, resulting in a gradual enhancement of the overall heat transfer performance and a subsequent increase in the overall heat transfer coefficient. The CO2 chemical absorption tube-type falling film reboiler developed in this study has achieved a reduction in the residence time of the absorbent within the reboiler, while simultaneously can improve the heat transfer efficiency of the reboiler and the CO2 regeneration rate of the amine solution. This is expected to significantly reduce the heat consumption for carbon capture.
  • Study on Thermal and Techno-Economic Performances of a New Solar-Coal Complementary Power Generation System
    WANG Chao, WANG Yankai, SUN Haojia, GAO Rongze, QUAN Xiang, WANG Limin, CHE Defu
    2024, 44(6): 973-983. https://doi.org/10.19805/j.cnki.jcspe.2024.230263
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    In order to reduce the influence of solar energy fluctuation on the performances of the solar-coal complementary power generation system, a new type of solar-coal complementary power generation system was proposed. Models of key devices and subsystems were developed and verified, and the thermal and techno-economic performances of the new solar-coal complementary power generation system were studied. Results show that the thermal performance of the system decreases with the operation load, and increases firstly and then decreases with the increase of direct normal irradiance. The average annual output power of the system is 699 MW, the average annual coal saving rate is 7.506 g/(kW·h), and the average annual solar-to-power efficiency is 10.82%. When the heat storage capacity duration is 10 h, the system has the best techno-economic performances, with the life-cycle net present value of 4.18×108 yuan, the internal return rate of 11.81% and the dynamic payback period of 12.6 years. The levelized cost of electricity is 0.402 yuan/(kW·h), and the profitability is good.
  • Optimization of Supercritical Carbon Dioxide Recompression Cycle in Nuclear Reactor
    HOU Shengya, XUE Songsong, YANG Qiguo
    2024, 44(6): 984-990. https://doi.org/10.19805/j.cnki.jcspe.2024.230254
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    Optimization research was conducted on supercritical carbon dioxide recompression cycle system applied to the fourth generation gas-cooled reactor. By establishing a comprehensive thermodynamic and exergoeconomic model, and introducing spatial compactness indicators based on the demand for nuclear power modularization, a study was conducted on supercritical carbon dioxide recompression cycle system from multiple dimensions such as thermodynamic performance, spatial compactness, and exergoeconomic performance. Impact of key parameters on the performance of supercritical carbon dioxide recompression cycle system was analyzed, and further multi-objective optimization was carried out to improve the applicability of the system. Results show that through multi-objective optimization, the comprehensive performance of the cycle is improved, and the optimal exergy efficiency, unit power cost rate, and required heat exchange area per unit output power are 71.5%, 3.11 cent/(kW·h), and 0.191 m2/kW, respectively.
  • Thermodynamic Analysis and Process Optimization of a Semi-closed Supercritical CO2 Cycle Using Process Splitting Method
    YU Liang, XIN Tuantuan, ZHANG Yifei, XU Cheng
    2024, 44(6): 991-1000. https://doi.org/10.19805/j.cnki.jcspe.2024.230256
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    In the face of the increasingly urgent need for the reduction of carbon emission and energy consumption, the development of efficient advanced thermal cycles with low carbon emission is becoming more and more important. A natural gas fueled semi-closed supercritical CO2 cycle was proposed with zero carbon emission, and the semi-closed cycle was split into an open cycle and a closed cycle through working fluid splitting to further clarify the thermal to power conversion process. Furthermore, the cycle splitting method was applied to the complex modified cycle, which was split into several simple cycles to formulate the thermodynamic evaluation models of the different process modification measures and intuitively reveal the energy-saving mechanism of different cycle configurations. Through parameter sensitivity analysis, the optimum parameters of process modification measures were obtained. Results show that the cycle efficiency can be effectively improved by various cycle layout modification measures such as reheating, recompression, intermediate cooling and partial cooling, which can contribute to the efficiency improvement of 1.79~5.59 percentage points. After the integration and optimization of various process modification measures, the net power generation efficiency of the system is increased by 10.18 percentage points compared with the basic cycle.