Planar Concentration Measurements in a Co-Axial Jet with Structured Illumination Assisted Polarization Separation Filtered Rayleigh Scattering (PS-FRS) Technique
U.E. Malkocoglu(1), S.C. Woolsey(2), G. Byun(1), K.T. Lowe(1)
1: Kevin T. Crofton Department of Aerospace and Ocean Engineering, Virginia Tech, Blacksburg, Virginia 24061, United States of America
2: George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332, United States of America
DOI:
The current work introduces an enhanced background mitigation strategy for Filtering Rayleigh Scattering (FRS) measurements, with the integration of polarization separation and structured illumination methodologies. Polarization separation efficiently isolated the target polarized FRS signal from the other irrelevant scattering sources with a limited additional effort and setup complexity, and minimized the effect of the polarization-insensitive background in FRS images. In addition to that, single-phase structured illumination spatially modulated the FRS signal further distinguishing it from the rest with the help of lock-in analysis, which specifically targets the spatial modulation frequency to extract the scattering signal. The inclusion of the structured illumination enhanced the FRS signal in a round co-axial He/N2 mixing jet stream by up to ∼15%, despite the low overall FRS signal levels associated with a small Rayleigh scattering cross section of the He flow.
