Thermochemistry Measurements in Non-Isobaric Flows
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The primary research objective of this study is to advance our understanding of flame suppression in supersonic flows by improving a technique capable of measuring the full thermochemistry in such non-isobaric reacting flows. This is achieved through two different channels: firstly, by further developing an incoherent Raman laser diagnostic technique capable of independently measuring temperature and density, and secondly, by analyzing and modifying an existing miniature supersonic burner (currently utilized as the test bed for the experiments). Vibrational Raman scattering is used to measure density and composition of major species (CO₂, O₂, CO, N₂, CH₄, and H₂O) while rotational Raman scattering is used to measure temperature. The independent measurements of density and temperature allow for the determination of pressure. This line imaging technique is applied to flows with very high strain rates and Reynolds numbers emanating from a miniaturized combustor. A matrix inversion method is incorporated into the laser technique to account for crosstalk in the vibrational spectra. Spectral sensitivity in the charged-coupled device (CCD) array is also introduced into the vibrational processing. Laser energy normalization and laser pulse synchronization are added to the experimental setup. Significant improvements in signal-to-noise ratio (SNR) are observed. A commercial computational fluid dynamics (CFD) code is utilized to model the flow inside the burner. Due to the burners complex geometry, a three dimensional computational domain is used at the expense of a detailed chemical approach. Burner configurations with short and long fuel injectors were studied. Results for the short injector show a flame attached at the tip of the injector while results for the long injector show no combustion taking place. Computational and experimental mole fraction distributions at the nozzle exit are also compared. Results for both injector configurations demonstrate frozen flow in the external supersonic flow, suggesting configuration inside the burner needs to be modified for future use.
Ellis, Dean William (2017). Thermochemistry Measurements in Non-Isobaric Flows. Doctoral dissertation, Texas A & M University. Available electronically from