Inverse design of inlet distortion using method of characteristics for direct-connect scramjet studies

Scramjet combustors are among the most crucial components in scramjet engines. Combustor experiments are generally conducted in two forms, namely, free jet (inlet-isolator-combustor components) or direct-connect (nozzle-isolator-combustor components) facilities. The direct-connect facility is commonly used in the combustor study because of the short research cycle, minimal investment, and high revenue. In this study, this facility is configured in a novel manner, designed, and numerically simulated. The proposed facility is first mounted with a facility nozzle, followed by an expansion component and an isolator. And the expansion component is inverse designed through method of characteristics (MOC). The proposed method can generate the expected profiles of real-isolator conditions of scramjet engines without encountering any starting problems. To verify the design philosophy, computational fluid dynamics (CFD) simulations are conducted on the isolators downstream of a scramjet inlet and the new direct-connect facility nozzle. The flow condition in free jet experiments agrees with that in the direct-connect facility. The different flow deflection distributions of the expansion component outlet (design parameters) are examined as well. Furthermore, the starting characteristics of the direct-connect facility are simulated. The simulation results ascertain that the design philosophy can solve the starting problem as expected. This facility, which is designed using an economical and convenient method, will be utilized in the future for experimental investigations. Moreover, it facilitates the comprehensive understanding of combustor phenomena.