Integrated Analysis of Scramjet Flowpath with Innovative Inlets

During the second year of this challenge effort, combustion simulations were employed to provide significant insight into the relative impact of flow distortion arising in the different inlet designs: rectangular, scoop and "jaws". Efforts on the rectangular cross-section design extended previous analyses to explore multi-cavity injection with streamwise and spanwise interlacing. To this end, new injection strategies were developed in a standard single-cavity configuration and tested for optimum combustion efficiency, measured through flame holding and stabilization characteristics. Among the key observations is the improved efficiency associated with opposing injector pairs within the cavity in a manner that reinforces the natural circulation. Furthermore, under appropriate circumstances, configurations that trigger or enhance spanwise instabilities to yield longitudinal vortices tend to augment mixing and may be more effective than normal injection. For the newer inward turning inlet designs, a common combustor configuration was developed and tested numerically. Preliminarily, eight circumferentially distributed injectors mounted on the cavity back face were considered. Although the injection rates were modest, several distinctions were immediately apparent in performance due to differences in jaws and scoop inlet distortion. The profile obtained with jaws provides highly non-uniform combustion regions relative to scoop, yielding different burning patterns as measured from the products of combustion. An initial assessment of the flow in the recessed cavity region (in the low burning section of the combustor) indicates that the streamwise direction recirculation was not as strong for scoop as for jaws. Further analyses are in progress to optimize both configurations in an attempt to guide evolution of each design.