Performance evaluation of SCO2 Brayton cycles for thermal protection and power generation in hypersonic vehicles

To address thermal protection and electricity demand in hypersonic vehicles, this study establishes a thermodynamic simulation platform to evaluate the performance of SCO2 regenerative (Reg.BC), recompression (Rec. BC), and turbine split flow (TS.BC). The effects of the working fluid mass flow rate (m) and split ratio (x) are analyzed for a fixed heat absorption (Qth) of 554.4 kW and Qth values ranging from 400 kW to 1900 kW. The results show that for a constant Qth, there is always a corresponding m. When the mass flow rate is below m, the Rec.BC outperforms the TS.BC, while the TS.BC performs better when m is exceeded. At Qth = 554.4 kW, m equals 3.264 kg/s. For a given Qth, optimal performance can be achieved by adjusting both m and x. In terms of cycle thermal efficiency (eta th) and cycle net output work (Wnet), the Rec.BC outperforms the TS.BC, which in turn outperforms the Reg.BC. For Wnet per unit mass, the Reg.BC is the most efficient, followed by the Rec.BC and TS. BC. Moreover, the TS.BC does not offer improvements in mitigating the issue of pinch points.