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Dynamic Modeling and Characteristic Analysis of Helium Brayton Cycle System


 The Brayton cycle using helium gas as a working medium has the advantages of high conversion efficiency, simple design, compact structure and high inherent safety. It can be combined with fossil energy, nuclear energy, solar energy and other forms of heat sources, and has broad prospects for development. The Helium Brayton cycle (HBC) is a highly integrated system. The dynamic characteristics of the Brayton cycle system are complex and difficult to obtain. It is necessary to establish the mechanism model of the HBC for research and analysis, and provide the basis for subsequent control system design. Based on the equations of conservation of mass, energy, momentum and energy balance, the thermo-hydraulic models of heat accumulator, precooler, intercooler and pipeline are established in this paper. The model was established according to the characteristic curves of helium turbine, low-pressure compressor and high-pressure compressor, and the shaft speed model was established according to the energy balance equation. Coupled with the above models, a lumped parameter nonlinear model of the HBC is established. Based on the MATLAB/Simulink platform, typical transient conditions such as external heat source power disturbance and external load disturbance are calculated. The results show that with the decrease of heat source input power, the temperature of each equipment and the net efficiency of the circulation decrease. When the external load fluctuates, the imbalance of compressor and turbine torque will lead to the rapid change of shaft speed.