Historical survey on enhanced mixing in scramjet engines

Select methods are reviewed that have been used by the scramjet community t o enhance mixing of fuel with oxidizer to achieve high combustion efficienc y with reduced length combustors. The review also includes research on enha nced supersonic free shear layer mixing from the jet noise reduction commun ity. This latter community has considered concepts involving acoustic excit ation or passive excitation of shear layer instabilities to minimize noise production. Several of these concepts are amendable to active control for s ystem optimization.