Thermodynamic System Optimization Research Of Supercritical CO₂ Cycle Power Generation Technology

Supercritical CO₂ cycle power generation technology gets attention worldwide because of its advantage such as wide applications,small size,high cycle efficiency and simple system,and its application research has extended from nuclear power to fossil power plants,ship propulsion system,concentrating solar power,fuel cells,industrial waste heat recovery,so it’s a very promising cycle power generation technology.This paper studies the calculation method of CO₂ thermal physical properties,and uses QT（GUI library based on C++）establish SCO₂ thermal simulation module,including physical properties computing module,components and equations libraries,then tests the thermal simulation model by compared with NIST’s CO₂ physical properties data and thermal module established by the American National Laboratory.It’s found that the CO₂ physical properties calculation and heat balance calculation are with high accuracy,which means that can be used for SCO₂ cycle system modeling and simulation.This paper studies the characteristics of simple SCO₂ closed Brayton cycle system,and the influence of the key parameter of compressor,turbine,recuperator to system efficiency.Conclusions are as follow: The effect of compressor inlet parameters on the cycle efficiency is significant.The higher is the turbine inlet temperature,the higher is the efficiency of system,and the inlet temperature has effect on the optimal turbine inlet pressure.The affect of Turbine and compressor efficiency and recuperator temperature difference to system efficiency is substantially linearly.It’s found SCO₂ system can be well applied to different temperatures heat source under various system configurations by modeling and simulation.This paper introduces a case that using a SCO₂ cycle to replace steam cycle for the bottom loop of distributed energy gas turbine combined cycle and carrying on thermodynamic modeling and simulation then optimizing the system parameters to obtain 4.6% efficiency increase,the efficiency of which is 5.5% higher than steam cycle system.Then exergy analysis is used to compare the energy utilization for the two program before and after the optimization,and find that the exergy efficiency of turbine,compressor,recuperator increase and the exergy efficiency of total system increase by 8.66%..