The plate-fin heat exchanger was designed for the liquid cooling thermal management system of the hybrid electric propulsion system for an electric vertical take-off and landing (eVTOL) vehicle. The offset-strip fin design was applied, and the performance of the heat exchanger was evaluated, particularly with respect to the inclination of the airflow entering the heat exchanger. The estimated performance during the design phase matched well with the experimental results. The inclination of the heat exchanger had a minimal effect on thermal performance, with a slight increase in performance as the inclination increased. However, the pressure difference along the airflow was affected, likely increasing as the inclination increased. The sensitivity of various parameters on coolant temperature was also investigated. The air inlet temperature had a significant effect on coolant temperature, followed by the coolant flow rate. Therefore, when designing the thermal management system, careful consideration should be given to the ambient air temperature and coolant flow rate.

High-speed airbreathing vehicles operating in the hypersonic region are subjected to various flight conditions, making it essential to investigate their performance characteristics under off-design conditions. The wavecatcher intake, known for better performance than conventional two-dimensional intakes, has been widely studied. However, a systematic method for defining its inlet and outlet geometries is still lacking. This numerical study identifies key flow parameters to establish relationships between intake shape and flow characteristics. Based on these correlations, design strategies for inlet and outlet geometries are proposed to enhance off-design starting performance. Using computational fluid dynamics (CFD), three intake configurations were evaluated: rectangular-to-elliptical transition (REST), rectangular-to-rectangular (RtR), and a newly developed semicircular-to-elliptical transition (SEST). For REST and RtR, two aspect ratios were tested to examine their geometric influence. The design point was Mach 7 at 28.7 km altitude, and three-dimensional CFD analyses were conducted for off-design conditions, including angles of attack from [Formula: see text], freestream Mach numbers from 5 to 10, and sideslip angles from 2 to 10 deg. The results show that the SEST configuration provides robust starting performance across all off-design conditions, making it a highly effective option for wavecatcher intake design.