Heat transfer characteristics and performance evaluation of a cooled radial-inflow turbine rotor blade for closed Brayton cycle based on He-Xe mixture

Closed Brayton cycles using He-Xe mixtures are promising for compact, high-power-density energy conversion because their favorable thermophysical properties reduce turbomachinery stage requirements compared with pure helium. However, increasing turbine inlet temperature to improve cycle efficiency imposes severe thermal loads on radial-inflow turbine components, making traditional uncooled designs unsuitable for long-term operation. This study preliminarily investigates the internal cooling-channel layout and localized cooling features of a radial-inflow turbine rotor blade for a He-Xe closed Brayton cycle. A three-dimensional conjugate heat transfer method is used to assess four cooling configurations in terms of thermal protection and aerodynamic performance. To mitigate the intense leading-edge thermal load, a composite configuration combining impingement and film cooling is proposed, in which coolant first passes through an impingement cavity and is then discharged through leading-edge film holes, significantly reducing local solid temperature. In addition, 45° angled ribs and a crescent-shaped guide are introduced to enhance coolant-side heat transfer and redistribute coolant within compact internal passages. Under a fixed coolant mass-flow constraint, the final configuration improves thermal protection in critical regions, including the leading edge, tip, root, and trailing edge, while producing a stage efficiency penalty of 3.96%. The effects of individual cooling elements on downstream flow evolution and local heat transfer are also analyzed. These results provide guidance for radial-inflow turbine cooling design in high-temperature He-Xe closed Brayton cycle systems.