A novel liquid metal MHD enhanced Closed-Brayton-Cycle power generation system for hypersonic vehicles: Thermodynamic analysis and performance evaluation with finite cold source

Closed-Brayton-cycle (CBC) is a potential thermodynamic cycle for high-power dynamic electricity generation on hypersonic vehicles, but finite cold source onboard limits its power level. This study presents a liquid metal MHD (LMMHD) enhanced CBC power generation system and exhibits its theoretical advantages through thermodynamic analysis. The influence of cold source temperature rise, turbine inlet temperature and LMMHD conversion efficiency on system performance is investigated by a zero-dimensional power optimization model, and the electric power and power generation efficiency between LMMHD enhanced CBC and standalone CBC are compared. Results indicate that LMMHD enhanced CBC can theoretically meet the demand for megawatt-class power generation on hypersonic vehicles, the electric power per unit fuel mass flowrate of which can reach 637.84 kW. High-temperature liquid metal and well-designed LMMHD generator are extremely essential to improve the turbine inlet temperature and LMMHD conversion efficiency. Compared with standalone CBC, the electric power increased percentage of LMMHD enhanced CBC is as high as 92.44 %. This paper provides primary performance evaluation for LMMHD enhanced CBC, the key technical issues of which, including the LMMHD generator structure design, mixing and separation process optimization, will be the focus in our next work.