Mechanical and Aerospace Engineering Colloquium

November 29, 2017
November 29, 2017
Speaker: Sean Kearney, Ph.D.
                  Spectral Energies         
Title: Probing Fire Environments and Particle-Laden Flames by Coherent Anti-Stokes Raman Scattering
Location: Easton Hub Auditorium
                  Fiber Optics Building
Time:  3:30 p.m.
Abstract: Laser-based diagnostics have revolutionized laboratory combustion research, providing measurements of virtually any parameter of interest with the highest of fidelity. While powerful, most of these state-of-the art measurement approaches have experienced an application space that is frequently limited to clean-burning laboratory flames. In this talk, we will focus on the insertion of coherent anti-Stokes Raman scattering (CARS) into fire research environments, which are characterized by luminous, particle-laden flames that present multiple optical interferences, and by the large spatial scale of the flame system. We will begin with an introduction to the CARS technique and explain its sensitivity to both temperature and species concentration in gas-phase media. A unique application of CARS and laser-induced incandescence (LII) instruments, which employ nanosecond-duration pulsed lasers, to the study of fully turbulent meter-scale hydrocarbon pool fires is discussed. The design of hardened, fiber coupled instrumentation for application in the challenging large-scale test environment is presented, and joint statistics of the turbulent temperature and soot fluctuations that govern subgrid-scale emission of thermal radiation are provided. We then turn our attention to the application of ultrashort-pulse femtosecond lasers to gas-phase combustion research. The advantages of these high-bandwidth laser sources are explained, and the integration of a unique CARS instrument based a femtosecond Raman pump with a picosecond-duration probe pulse, generated via second-harmonic bandwidth compression (SHBC), is described. We discuss application of the SHBC CARS instrument to aluminum-based propellant flames burning at atmospheric pressure and solid carbon-epoxy-composite-fueled fire environments. The talk concludes with the extension of the CARS technique from point measurements to spatially correlated1-D line imaging of temperature, fuel, and oxygen on a single-laser-shot basis in a plasma-assisted hydrogen diffusion flame.
Bio: Dr. Sean P. Kearney has recently accepted a position as Technical Director of Spectral Energies LLC, the prime onsite research contractor at the Air Force Research Laboratory’s Combustion and Laser Diagnostics Research Complex at Wright-Patterson AFB, OH. He was previously a Distinguished Member of the Technical Staff at Sandia National Laboratories, where he was Principal Investigator for a broad range of laser/optical diagnostic development and application efforts over the duration of his 18-year tenure at Sandia. His work has supported programs over a diverse application space, including combustion; energetic materials; fluid mechanics; heat transfer; microsystems and remote sensing. He has successfully performed laser-diagnostic measurements in challenging, real-world combustion environments, such as meter-scale pool fires and metallized propellant flames. Dr. Kearney’s recent work has focused on development of ultrashort-pulse femtosecond CARS diagnostics for temperature, species and pressure sensing. His work on femtosecond CARS development has resulted in two Best Paper Awards at national AIAA conferences and he is an Associate Fellow of AIAA. Dr. Kearney has authored 35 peer-reviewed Journal articles, 55 conference publications and delivered numerous invited lectures. Dr. Kearney holds a Ph.D. and Master’s degree in Mechanical Engineering from the University of Illinois at Urbana-Champaign, and a Bachelor’s Degree in Mechanical Engineering from Clarkson University.
For additional information, please contact Professor Aaron Mazzeo at or 848-445-0504.