The abilities of Scramjets and Ramjets, in their respective operating ranges, are partially bridged by dual-mode Scramjets. The limitations of operation are due to making a static motor that is designed to function in both modes resulting in low and high speed restrictions. This study covers the analysis into the ability of morphing the combustor in a Scramjet to allow for expanded operational capacities through simple mechanisms. Through the restriction and expansion of combustor cavity volume, operational capabilities of the engine can, therefore, be modified to best match scenario requirements. Due to the engine's ability to match a wide variety of scenarios the limitations seen in that of the dual-mode Scramjet are avoided through the usage of a morphing combustor. From initial findings using the quasi-1D Canonical REactor Scramjet Simulation (CReSS) solver, progress was made to confirm results through the usage of Computational Fluid Dynamics (CFD). Prior analysis of the momentum balance between stages two and four of the simulated Scramjet engines, the results showed that the variable geometry matched or outperformed the baseline HiFiRE geometry. The analysis revealed points of Mach and altitude where certain combustor volumes demonstrated greater performance. This greater performance is only gained by the ability to tune the engine in flight to react to external factors as there is no dominant geometry for a given range of Machs and altitudes. This tuning allows for the usage of performance mapping to extract the greatest performance possible over a variety of conditions. Further, it allows for the project to be continuously expanded into mapping appropriate reactions to other initial conditions and stimuli. Using CFD modeling to perform a parametric study on the prior work allows for finer control and analysis of said initial conditions and the resulting flow paths in the variety of tested combustor volumes. From this a discussion is made in regards to the effectiveness of the prior CReSS based analysis of the novel approach. / Master of Science / The abilities of Scramjets and Ramjets (engines which contain no moving parts as the compression of the incoming air is accomplished by the speed at which they operate with the separating factor being that the scramjets internal flow does not go below supersonic speeds), in their respective operating ranges, are partially bridged by dual-mode Scramjets. Dual-mode Scramjets are scramjets which can function with both sub- and super-sonic internal flow speeds. This being below or above Mach 1 (343 m/s, 767.3 mph) respectively. The limitations of operation are due to making a static motor where the geometry does not change that is designed to function in both modes resulting in low and high speed restrictions. This study continues the analysis into the ability of morphing the combustor, the volume in which the air fuel mixture combusts, in a Scramjet to allow for expanded operational capacities through simple mechanisms. Through the restriction and expansion of combustor volume, operational capabilities of the engine can, therefore, be modified to best match scenario requirements. Due to the engine's ability to match a wide variety of scenarios the limitations seen in that of the dual-mode Scramjet are avoided through the usage of a morphing combustor where morphing in this case is a simple volume change equivalent to that of a slide whistle. From initial findings using the quasi-1D Canonical REactor Scramjet Simulation (CReSS) solver, progress was made to confirm results through the usage of Computational Fluid Dynamics (CFD). Prior analysis of the momentum balance between stages two and four of the simulated Scramjet engines, the results showed that the variable geometry matched or outperformed the baseline HiFiRE geometry. The analysis revealed points of Mach and altitude where certain combustor volumes demonstrated greater performance. This greater performance is only gained by the ability to tune the engine in flight to react to external factors as there is no dominant geometry for a given range of Machs and altitudes. This tuning allows for the usage of performance mapping to extract the greatest performance possible over a variety of conditions. Further, it allows for the project to be continuously expanded into mapping appropriate reactions to other initial conditions and stimuli. Using CFD modeling to perform a parametric study on the prior work allows for finer control and analysis of said initial conditions and the resulting flow paths in the variety of tested combustor volumes. From this a discussion is made in regards to the effectiveness of the prior CReSS based analysis of the novel approach.

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