Effects of film cooling injection inclination angle on cooling performance in rotating detonation combustors

Film cooling is a promising thermal management solution for rotating detonation combustors (RDCs) maturing toward long-duration engineering implementation. Aimed at elucidating the interaction between air coolant and rotating detonation waves (RDWs) and assessing the cooling performance, three-dimensional numerical simulations are conducted on an RDC utilizing four different film cooling injection inclination angles and compared to a case without coolant injection. Increasing injection angles from 30 degrees to 90 degrees results in a broader detachment region and deeper penetration, negatively influencing the cooling performance. A time-averaged method is adopted to evaluate the overall cooling performance, including axial temperature profiles, film protection coverage, RDC film effectiveness, and pattern factor. The results show that the cylindrical cooling hole with a 30 degrees injection angle outperforms others due to enhanced wall attachment of the coolant and reduced interaction with the mainstream hot gas. Consequently, a low injection angle within the manufacturing limits is recommended for practical applications. Furthermore, this study uncovers several phenomena unique to RDCs when introducing film cooling, absent in conventional gas turbines, such as temperature discrepancy between the inner and outer walls, elevated upstream temperature caused by coolant injection, and non-uniform cooling effectiveness between the two sides of the cooling holes. Finally, the interplay between film cooling and RDW is illustrated through temperature and pressure gradient contours.