Digital Imaging Holography and Pyrometry of Aluminum Drop Combustion in Solid Propellant Plumes
Abstract not provided.
Publications
Hybrid fs/ps CARS for sooting and particle-laden flames
54th AIAA Aerospace Sciences Meeting
We report the application of ultrafast rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning aluminized ammonium perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laserbased diagnostics, with intense background luminosity, scattering and beam obstruction from hot metal particles that can be as large as several hundred microns in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminumparticle- seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulateenhanced laser-induced breakdown. Introduction of fs/ps laser pulses enables CARS detection at reduced pulse energies, decreasing the likelihood of breakdown, while simultaneously providing time-gated elimination of any nonresonant background interference. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements from the fs/ps rotational CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Preliminary results in canonical flames are presented using a hybrid fs/ps vibrational CARS system to demonstrate our progress towards acquiring vibrational CARS measurements for more accurate temperatures in the very high temperature propellant burns.
Optical phase-conjugate digital inline holography for correcting aberrations in particle-laden flames
54th AIAA Aerospace Sciences Meeting
While historically there have been many demonstrations of phase-conjugate holography to correct for noise created by phase distortions, the technique has not been applied to modern digital inline holographic measurements. Here, we present the theory and initial experiments exploring the impact of using phase-conjugate digital inline holography (PCDIH) to reduce noise produced by phase distortions through index-of-refraction gradients, such as would be experienced in a combustion environment. We demonstrate the ability to measure 3D object locations using PCDIH and correct for some types of disturbances. To quantify the technique, a plasma generator is used to produce strong indexof- refraction changes in room air. Object position errors in these measurements from both traditional DIH and PCDIH are compared. Preliminary results suggest that the use of PCDIH could potentially reduce positional error by approximately half when measuring through phase disturbances.
Hybrid fs/ps CARS for Sooting and Particle-laden Flames
We report the application of ultrafast rotational coherent anti-Stokes Raman scattering (CARS) for temperature and relative oxygen concentration measurements in the plume emanating from a burning aluminized ammonium perchlorate propellant strand. Combustion of these metal-based propellants is a particularly hostile environment for laserbased diagnostics, with intense background luminosity, scattering and beam obstruction from hot metal particles that can be as large as several hundred microns in diameter. CARS spectra that were previously obtained using nanosecond pulsed lasers in an aluminumparticle- seeded flame are examined and are determined to be severely impacted by nonresonant background, presumably as a result of the plasma formed by particulateenhanced laser-induced breakdown. Introduction of fs/ps laser pulses enables CARS detection at reduced pulse energies, decreasing the likelihood of breakdown, while simultaneously providing time-gated elimination of any nonresonant background interference. Temperature probability densities and temperature/oxygen correlations were constructed from ensembles of several thousand single-laser-shot measurements from the fs/ps rotational CARS measurement volume positioned within 3 mm or less of the burning propellant surface. Preliminary results in canonical flames are presented using a hybrid fs/ps vibrational CARS system to demonstrate our progress towards acquiring vibrational CARS measurements for more accurate temperatures in the very high temperature propellant burns.
Optical phase-conjugate digital inline holography for correcting aberrations in particle-laden flames
Abstract not provided.
Phase Conjugate Digital Inline Holography (PC-DIH)
Abstract not provided.
Hybrid fs/ps CARS for Sooting and Metalized Flames
Abstract not provided.
Characterization of aerodynamic fragmentation in the bag and sheet thinning regimes by crossed‐beam two‐view digital in‐line holography
Abstract not provided.
High-Speed 1D Raman/Rayleigh Scattering Imaging in Turbulent H2/N2 Flames
Abstract not provided.
Characterization of drop aerodynamic fragmentation in the bag and shear thinning regimes by crossed-beam two-view digital in-line holography
Abstract not provided.
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