Thermodynamic cycle analysis and optimization to improve efficiency in a 700 °C ultra-supercritical double reheat system

  • Mei YangEmail author
  • Yun-long Zhou
  • Di Wang
  • Jiayu Han
  • Yujia Yan


When increasing steam parameters, the incomplete thermodynamic cycle and large irreversible system losses are bottlenecks in improving thermal efficiency in ultra-supercritical power plants. In this study, a comprehensive analysis of both parameter optimization and system cycle analysis is carried out for a 1000-MW double reheat ultra-supercritical thermal power plant. First, the genetic algorithm is used to optimize the primary and double thermal pressure, as well as the steam extraction parameters of the steam turbine. Then, a thermodynamic optimization model is proposed to analyze performance. Moreover, the exergy analysis method is applied to reveal the irreversibility mechanism in the thermodynamic cycle. In order to further solve the energy-grade mismatch problem, the performance of a regenerative steam turbine thermal system is improved based on the optimized system. The results indicate that the power generation efficiency of the optimized system is 0.31% higher than that of the prototype system, and the heat consumption rate is decreased by 43.67 kJ (kW h)−1. The power generation efficiency in the regenerative steam turbine system is up to 52.42%, which is 1.44% higher than that of the optimized system. Therefore, an effective method to improve the thermal efficiency is obtained through the thermodynamic cycle analysis and optimization for 700 °C ultra-supercritical double reheats systems.


700 °C ultra-supercritical power plant Thermodynamic cycle optimization Exergy analysis The power generation efficiency Thermodynamic performance 

List of symbols


The amount of the work by a steam turbine, kJ kg−1


The efficiency of the steam turbine system


The specific exergy of the supply system, kJ kg−1


The exergy of feed water, kJ kg−1


The mass flow rate of main-steam, kg s−1


The mass flow rate of steam single reheat steam, kg s−1


The mass flow rate of double reheat steam, kg s−1


The main-steam pressure


The first reheat pressure


The second reheat pressure


No. i the extraction pressure


The exergy of intermedium-pressure turbines inlet steam, kJ kg−1


The exergy of low-pressure turbines inlet steam, kJ kg−1


The exergy of intermedium-pressure turbines exhaust steam, kJ kg−1


The exergy of low-pressure turbines exhaust steam, kJ kg−1


The heat consumption rate


The exergy efficiency


The exergy losses, kJ kg−1


The specific exergy of inlet, kJ kg−1


The specific exergy of outlet, kJ kg−1


The specific exergy of heat flux, kJ kg−1


The specific enthalpy of the working medium at the given state, kJ kg−1


The specific enthalpy of the working medium at the environmental state, kJ kg−1


The average temperature of heat absorption process of working medium, K


The environment temperature, K


The specific enthalpy of the working medium at the given state, kJ (kg K)−1


The specific entropy of the working medium at the environmental state, kJ (kg K)−1


The entropy production of irreversible processes, kJ (kg K)−1


Heat consumption of power plants, kJ h−1


The output power of generator, kW


The fuel consumption per unit time of boiler, kg h−1


The low heat value (LHV) of coal, kJ kg−1


The unit of heat consumption rate, kJ (kW h)−1


The specific work of the power equipment, kJ kg−1


Heat absorbed by the working medium kJ kg−1




High-pressure cylinder


Intermediate-pressure cylinder


Low-pressure cylinder






Condensate pump


No. i regenerative heater



This work has been supported by the National key research and development program (Project No. 2018YFB0604404), and Science and Technology Development Project of Jilin Province of China (Project No. 20190103008JH).


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Copyright information

© Akadémiai Kiadó, Budapest, Hungary 2019

Authors and Affiliations

  1. 1.School of Energy and Power EngineeringNortheast Electric Power UniversityJilinChina

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