Aiming at the problem of test media vitiation by combustion heating associated with ground test facility, the effects of combustion vitiated air on hydrogen-fueled scramjet performance were investigated with numerical approach. At the simulating condition of flight Mach 6.5, fuel equivalence ratio 0.6, the flow-field and performance of the scramjet were numerically calculated within clean free airstream and vitiated airstream respectively. As for the vitiated airstream, several schemes of matched parameter relative to clean air and different combustion heating methods were considered. The modified H2/O2reaction mechanism with seven species/eight steps and the standard k-ε turbulence model were employed, which would be firstly validated by the direct-connected combustor test data. The summarized conclusions are:(1) both the thrust and specific impulse of scramjet in the vitiated airflow decrease, compared with those in clean airstream; (2) the overall least discrepancy of scramjet performance within alcohol heating vitiated airstream is found when the static temperature, static pressure and Mach number are matched, while the most discrepancy when the total temperature, total pressure and Mach number are matched; (3) the overall least discrepancy of scramjet performance within hydrogen heating vitiated airstream is found when the total enthalpy, static pressure and Mach number are matched, while the most discrepancy when the methane heater is used.
