Supersonic Combustion Enhancement By Oxygen

This paper examines the gas dynamics effects of enhancing combustion in a supersonic axisymmetric flowpath by injecting supplemental oxygen gas into the flow. Transverse injection of oxygen supplements the incoming air and increases the oxygen mass fraction in the flowpath with a penalty of decreasing total pressure. The effect of changing gas composition and quenching the heat generated by high enthalpy combustion is examined in a zero-dimensional analysis and verified experimentally. Experimental results in the ACT-II high enthalpy blowdown wind tunnel are presented for Mach 3 flows in an axisymmetric flowpath with a rapid expansion between the isolator and combustor. Wall pressure measurements and high-speed plasma-luminescence imaging shows that oxygen injection is able to locally and safely choke the flow for a ram mode combustion operation of the flowpath. Such physics can be envisioned in a vehicle operating in high atmospheres where oxygen concentration decreases and thus the available oxidizer becomes a limiting factor in combustion.