Large-eddy simulations of the operation of an axisymmetric isolator–combustor configuration experimentally tested in an arc-heated combustion facility and equipped to study the influences of secondary oxidizer injection are presented in this work. Oxygen enrichment may have benefits in enabling stable scramjet operation at higher altitudes and higher Mach numbers. Inflow conditions are generated from computations of flow within the arc heater—results that compare predictions with laser spectroscopy and wall pressure measurements are reported. Predictions show good agreement with experimental wall pressure measurements for cases with pure Formula: see text injection and with air injection. Both the use of air and Formula: see text as the oxidizing agent can enable stable dual-mode operation, but the thrust potential is less for air injection. Injection of 19% of the fuel into the combustor rather than into the isolator leads to a reduced shock train length and an increase in stream thrust. The flame transitions from a non-premixed flamelet-like structure nearer to the injectors to a combination of non-premixed and rich-premixed structures in the wakes of the injectors. Most of the heat release occurs under locally non-premixed conditions.
Richardson et al. (2026) studied this question.