Simulation Of SCO₂ Brayton Cycle System And Related Turbomachinery

Compared with the traditional system,the Supercritical Carbon Dioxide（sCO₂）Brayton circulation system has become a research hotspot in recent years because of its advantages such as small system size,high circulation efficiency and easy access to working medium.Aiming at the problems still existing in the research reports of scholars,this paper carried out related studies on the sCO₂ Brayton circulation system from two aspects of cycle simulation and related turbomachinery design.In order to further study the influence of different physical property calculation methods on the simulation accuracy of sCO₂ Brayton cycle performance,three cycle models were firstly established by using Aspen HYSYS and Aspen Plus software:simple cycle,re-compression cycle and split-flow re-compression cycle.Four physical property methods were used to simulate each cycle.Compared with the laboratory data,the results show that the REFPROP physical property calculation method based on Aspen Plus software has a high accuracy.Then the physical property method was used to calculate and compare the cycle efficiency of the above three cycles under the same working condition.The results show that the cycle with heat recuperator can obtain higher efficiency.Finally,based on the re-compression cycle model,the influences of the five main parameters on the cycle efficiency were studied under different recuperative conditions.The conclusion of this paper can provide a theoretical reference for the design of the re-compression cycle model of sCO₂.In order to investigate the performance of turbomachinery in the sCO₂ Brayton cycle system under off-design conditions and its influence on the cycle system,this paper selects the experimental conditions of the split-flow re-compression cycle as the design conditions to design and analyze the four turbomachinery equipment in the cycle:the main compressor,the re-compressor and two turbines.Firstly,the 1D design and 3D modeling of the four equipment were carried out by using the Concept NREC software.Then Numeca software was used to simulate the internal flow of the four equipment.The calculation results show that the four devices designed in this paper can meet the design requirements and have good aerodynamic performance.On this basis,the Concept NREC software was used to analyze the performance of the four equipment under 1D variable conditions,and the characteristic curves of the four equipment were obtained.Finally,this paper combines the characteristic curves of the four turbomachinery designs with the cycle model to simulate and analyze the actual operation of the cycle.The simulation results can provide relevant references for the application of the sCO₂ Brayton cycle in actual operation.