SOLID-FUEL SUPERSONIC COMBUSTION

A solid fuel scramjet which utilized a combustor made of Plexiglas has been successfully demonstrated. Hot air entered the Plexiglas combustor with a Mach number of 1.5. A small amount of hydrogen gas was injected into a mixed supersonic-subsonic flame stabilization zone at the head-end of the combustor to help sustain combustion. The combustor consisted of a short, constant area section followed by a diverging section. Combustor exit Mach numbers were typically 1.1-1.4 and combustion efficiencies as high as 87% have been attained with equivalence ratios between 0.49-0.65. Nozzle exit temperature rake measurements indicated that the rough surface generated in the near thermally choked constant diameter region generated enough mixing to provide high centerline temperatures. However, to date the heat addition and wall friction induced losses have resulted in 50-70% losses in stagnation pressure across the combustor.