To reveal the energy transport mechanisms over the compression ramp of a supersonic inlet under shock-wave/boundary-layer interaction (SBLI), this paper investigates the energy transport characteristics of the second compression ramp of a supersonic inlet at two typical freestream Mach numbers, Ma = 3 and Ma = 4 (design condition), by combining large-eddy simulation (LES) with the momentum potential theory (MPT). The MPT decomposes the fluctuating momentum field into vortical, acoustic, and entropic modes. Combined with the transport equation of fluctuating enthalpy, this approach reveals the energy transport and conversion pathways of fluctuating enthalpy within the core region of shock-wave/boundary-layer interaction (SBLI). Results show that the Ma = 3 case exhibits a spatially inverse pattern characterized by "global attenuation but wall enhancement": over the mid-span plane, all three modes show a decreasing or plateauing trend, with the RMS value of the B′ mode decreasing from 16.16 to 12.06 (about 25% reduction) and that of the A′ mode decreasing by about 30%; whereas on the wall of the second compression ramp, all three modes are significantly enhanced, with the entropic mode exhibiting the largest increase. Flux divergence analysis indicates that the vortical divergence is globally positive, while the acoustic and entropic divergences are globally negative, and the three nearly completely cancel each other locally at every spatial point. This spatially complementary pattern remains robust under different inflow conditions. Source-term analysis further reveals local source–sink pairing between the vortical and acoustic source terms, as well as coexistence and competition between internal driving and dissipation mechanisms within the entropic source term. The energy balance framework for SBLI established in this study provides a mode-level theoretical reference for energy source identification and modal contribution analysis in thermal protection design of inlet compression surfaces.

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.