Review on heat-to-power conversion technologies for hypersonic vehicles

Hypersonic vehicles have enormous military and economic value, while their power and thermal protection demands will increase substantially with the rise in Mach number and duration. Converting the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection, but also supply power for the vehicle. This paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles, including the indirect conversion of Brayton and Rankine cycles, direct conversion of thermoelectric materials, and combined conversion. For the open Brayton cycle with hydrocarbon fuel as the working fluid, the Power-to-Weight Ratio (PWR) can achieve the highest, at around 1.8, due to the high PWR of the hydrocarbon fuel turbine and the few components of the system. However, its work capacity is limited by the flow rate of the supplied fuel. The closed Brayton cycle can maintain a relatively high PWR, ranging from 0.2 to 0.8, while achieving relatively high output power and conversion efficiency. The Rankine cycle has a higher PWR, its range is close to that of the closed Brayton cycle, peaking at about 0.88. The thermoelectric materials technology has a small power generation level, making it more suitable for scenarios with low power demand. This review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.