Isolator-Combustor Interactions in a Direct-Connect Ramjet-Scramjet Experiment

Isolator-combustor interactions are measured in a direct-connect dual-mode ramjet-scramjet experiment. An operating point approach is used to create a mapping of the coupling effects between the isolator geometry, inlet flow conditions, and fuel injector behavior. The resulting isolator/injector coupling map provides a description of the response of the isolator to particular injector performance and the effective blockage it induces on the isolator flow. Existing models and correlations predicting the pressure rise across a pseudoshock and its resultant length were evaluated through comparison with measurements made in a heated-flow isolator duct that is coupled to a hydrogen-air combustor. The observation of a normal-to-oblique shock-train transition mechanism has led to the development of a revised shock-train operating regime description that takes into account the impact of Mach number and maximum pressure recovery on the shock configurations present in the isolator.