Performance of a scramjet combustor with combined normal and tangential fuel injection

The performance of a scramjet combustor with combined normal and tangential injection was experimentally investigated. Experiments were performed on a 500 mm cylindrical scramjet combustor at a freestream Mach number of 4.5, a nozzle supply pressure of 35.8MPa and a nozzle supply enthalpy of 5.8MJ/kg. Hydrogen fuel was injected normally to promote combustion and tangentially to reduce viscous drag. A series of fuel injectors were used to vary the proportion of tangential to normal fuel, with between 45 and 100 % of the fuel injected tangentially. Reductions in the viscous drag of up to 25% were observed with the greatest reductions occurring at the lowest total equivalence ratio tested for each injector. However, the average pressure produced by combustion with combined normal and tangential injection was approximately 50 % less than that produced by normal injection alone. An analysis of the change in specific impulse indicated that the best overall performance was produced by 100% normal injection.