Abstract
Laser absorption sensors for temperature and H2O near 1.4 and 2.5μm, CO2 near 2.7μm, and CO near 4.8μm were developed, validated, and deployed in an ethylene-fueled pulse-detonation combustor (PDC). Each sensor was fiber-coupled to enable remote light delivery to the PDC and photo-voltaic detectors were mounted directly to the PDC for improved light collection. Measurements were acquired simultaneously along two orthogonal lines-of-sight (LOS) in both the PDC combustion chamber and the throat of a converging–diverging nozzle located at the PDC exit. Measurements in the nozzle throat were combined with a choked-flow assumption to calculate the time-resolved enthalpy flow rate exiting the PDC. All sensors used first-harmonic-normalized wavelength-modulation spectroscopy with second-harmonic detection (WMS-2f/1f) to account for non-absorbing transmission losses and emission. Furthermore, strong mid-infrared absorption transitions were used to enable improved measurement accuracy and precision. These sensors were validated in non-reactive shock-tube experiments at temperatures and pressures up to 2700K and 50atm. There, these sensors exhibited a nominal accuracy of 3 to 5% with bandwidths from 2 to 20kHz. Measurements in the PDC indicated peak temperatures near 3500K with near-stoichiometric proportions of H2O and incomplete conversion of CO to CO2. The stagnation enthalpy flow rate was highly transient, but repeatable with peak flow rates near 25MW.
Published Version
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