Dynamic characteristics analysis of supercritical CO2 closed Brayton power generation system for hypersonic vehicles

Abstract

Supercritical CO₂ closed Brayton cycle (SCO₂CBC) has great application potential in the field of airborne power generation (APG) for hypersonic vehicles due to its high power-to-weight ratio and high thermal efficiency. Owing to the complex thermophysical properties of SCO₂ in CBC and considering the unique limited cold source environment on hypersonic vehicles, the dynamic cycle law of the SCO₂CBC APG system remains unknown. In this context, this paper constructs the dynamic model of the SCO₂CBC APG system for hypersonic vehicles and validates the key components and systems. On this basis, the main dynamic process and control effect in the cycle process are simulated and analyzed. Finally, the dynamic operating characteristics and the coupling influence law among the main components are determined through sensitivity analysis. The results demonstrate that the dynamic response of the system to the decrease in the power of the wall cooling channel is noticeably slower than that to the increase in the power. Furthermore, the system is more sensitive to the flow of cooling fuel than to temperature of cooling fuel. The designed SCO₂ dynamic regulation module can effectively adjust the fluctuation range of compressor inlet pressure in the load reduction process, and ensure the efficient and stable operation of the cycle, but the control range of the pressure threshold should not be too low. Among all the system components, the recuperator is the most sensitive to the change in the power of the wall cooling channel, while the compressor is the most sensitive to the dynamic response of cooling fuel flow and temperature disturbance. The above conclusions can provide necessary theoretical support for the performance evaluation, dynamic regulation, and variable condition design of the APG system of hypersonic vehicles.