Simultaneous CO and CO2 Laser Absorption Spectroscopy Sensing for Scramjet Combustion Characterization

Tunable diode laser absorption spectroscopy (TDLAS) sensors for simultaneous detection of temperature, carbon monoxide (CO), and carbon dioxide ([Formula: see text]) concentrations have been developed and demonstrated at the exit of a scramjet combustor in the ACT-II facility. Short scramjet combustor flow-through times, combined with elevated temperatures characteristic of the high enthalpy flight environment, create unfavorable conditions for complete reaction progress to combustion products. The implementation of these sensors addressed these challenges by quantitatively characterizing combustion progress. Different fueling schemes and equivalence ratios were tested to understand the effects of injection location and core flow penetration on combustion performance. Along with laser absorption measurements, simultaneous static pressure and high-speed broadband imaging were used for more comprehensive characterization. Results indicated that more robust combustion was achievable through near-cavity fueling as opposed to upstream injection. Greater differences in CO and [Formula: see text]-inferred temperatures existed in cases of nonuniform measurement conditions.