Study on supercritical carbon dioxide Brayton cycle cooling source disturbance control

  Objectives  This paper aims to cope with the possible impact of external condition disturbances on the operating parameters of a supercritical carbon dioxide (S-CO₂) Brayton cycle power generation system and ensure its efficient, safe and stable operation.

  Methods  A dynamic numerical simulation model of a simple S-CO₂ Brayton cycle power generation system is built using the Matlab/Simulink platform, and the transient operation characteristics of the system are analyzed. The change laws of the operating parameters of the thermodynamic cycle system under changing cooler parameters are then simulated, and the influence of the temperature fluctuation of the cooling source on the inlet and outlet parameters of the system components, system cycle efficiency and adjustment methods are analyzed.

  Results  The results show that the maximum error between the established system transient simulation model results and the experimental results is 3.658%; a 2 K increase in the cooling water temperature will lead to a 1.4 K increase in the compressor inlet temperature, and the system will need 300 s to restore stability; after adding a PID control system, the compressor inlet temperature change amplitude is reduced by 50% and the system stabilization time is reduced by 62%.

  Conclusions  The established model can accurately reflect the operation of the system. Based on the opposition of the influence of cooling water temperature increase and flow increase on the system, the proposed PID control system can ensure that the carbon dioxide working fluid in the system is always above the critical point, thereby ensuring the safe and stable operation of the system.