Quantitative Imaging of Ignition of Gaseous Mixtures

Stephanie A. Coronel

Hopeman 224

Optical diagnostics have been used for more than three centuries to observe dynamic and quasi-steady fluid events in ways that are not possible with the human eye alone. In recent decades, there have been significant advances in flow visualization techniques, including the development of sophisticated optical diagnostics that yield quantitative information. In spite of the existence of newer diagnostics, older and less expensive techniques can still be used today to quantitatively measure parameters of interest in flows. This talk focuses on interferometry, an imaging technique that dates back more than a century but which has only recently been applied to visualization and measurement of ignition of reactive flows. In addition to interferometry, I discuss the image processing algorithms required to extract temperature from images of optical phase difference (directly measured through interferometry). The technique and algorithms are applied to ignition of reactive mixtures by moving hot particles, an explosion hazard that is present in the nuclear, aircraft, and industrial sectors. Spatio-temporal temperature measurements of the flow (Re < 200) indicate that ignition preferentially occurs in the region of flow separation of the particle. Furthermore, a simplified model of reactive flow adjacent to a hot surface indicates that ignition occurs some distance away from the surface. At this location, heat release in the gas from the chemical reactions exceeds heat losses back to the surface.

Bio: Stephanie Coronel is a postdoctoral scholar at the Graduate Aerospace Laboratories at the California Institute of Technology (GALCIT). She received her PhD in Aeronautics from Caltech in 2016, where she worked for Professor Joseph E. Shepherd on combustion in the Explosion Dynamics Laboratory. She received her BS in Aerospace Engineering from the University of Texas at Arlington in 2009 and an MS in Aeronautics from Caltech in 2010. Her cur- rent research focuses on ignition in thermal boundary layers, specifically using optical diagnostics to make quantitative measurements of the reactive gas temperature adjacent to hot surfaces. Additionally, she works on understanding the process by which accidental explosions can occur in nuclear power plants. Her research interests include the development of novel diagnostics for visualization of reacting and non-reacting flows, specifically turbulence, as well as developing nanosecond imaging for investigating ultra high-speed events such as cavitation and deflagration to detonation transition (DDT).