UCLA

Non-intrusive optical sensors are critical for measurements of molecular species and thermodynamic properties in high-speed, high-temperature flows. Tunable laser absorption spectroscopy enables in situ, high-bandwidth, line-of-sight measurements of pressure, temperature, and species, enabling quantitative measurement on the kHz to MHz time scales of shock and detonation driven non-equilibrium processes. This work focuses on the advancement of multiple laser absorption spectroscopy methods that target combustion intermediate and product species including: (1) formaldehyde (CH2O, 3.6 μm), (2) hydroxyl (OH, 18.8 μm), and (3) an integrated laser diagnostic for carbon monoxide (CO, 5 μm), water (H2O, 5 μm), and carbon dioxide (CO2, 4.2 μm). Studies of CH2O and OH were performed on the UCLA high-enthalpy shock tube and focused on determining the spectroscopic parameters of these species at high temperatures, enabling quantitative interference-free measurements. The laser spectroscopy system targeting CO, H2O, and CO2 was developed to simultaneously measure all three species, temperature, and pressure in a rotating detonation engine. The collective advancements of these species-specific sensors involved new wavelength selection, novel methods for correcting spectral interference, and elevated pressure operation. Prospective future work includes further advancement towards supercritical combustion conditions, and applications for fundamental chemical kinetics and detonation physics studies.