Laser Induced Ignition with Resonant Multiphoton Absorption in Oxygen
Steven F. Adams, PhD
Electrical Systems Branch, Aerospace Systems Directorate
Air Force Research Lab, Wright Patterson AFB, Dayton, OH
A novel resonant laser-induced breakdown scheme has been demonstrated to provide precision spatial guidance of spark formation within an air flow and has been further demonstrated successfully in resonant laser-induced ignition of a moderate-speed flow of an air-propane mixture. This scheme could potentially provide ignition within a combustion system with a laser trigger leading to breakdown of an air-fuel flow within a high-voltage gap using a compact low power laser source. The laser scheme involves resonant enhanced multiphoton ionization (REMPI) in molecular oxygen and subsequent laser field-enhanced electron avalanche to generate a pre-ionized micro-plasma path between high voltage electrodes and thus guide the ignition spark through fuel-rich areas of the air-fuel flow. With this resonant method, sufficient photo-ionization and laser field-enhanced electron avalanche ionization have been generated for inducing air breakdown at a relatively low laser power compared to most laser breakdown concepts. This low power requirement may allow for a laser source to be transmitted to an ignition chamber via fiber optic coupling. Results of this study include high speed photographic analyses of flame ignition in an air-propane flow, showing the spatial and temporal evolution of the laser-induced spark and flame kernel leading to combustion.
Bio: Steven Adams is a research physicist in the Electrical Technology Branch, Aerospace Systems Directorate of the Air Force Research Laboratory at Wright Patterson Air Force Base. His pursuit of science and engineering began in the undergraduate Engineering Physics program at Wright State University while working as a co-op at General Motors’ Inland plant in Dayton. After earning B.S. and M.S. degrees in Engineering Physics at Wright State University, he joined the Air Force Research Laboratory in 1989. He then attended The Ohio State University through the Air Force's Long-Term Full-Time training program where he earned a Ph.D. in Chemical Physics, specializing in Laser Spectroscopy in 1999. Dr. Adams now manages an in-house research program at Wright Patterson on Energy Phenomena in Non-Equilibrium Ionized Gases. In addition to his duties with the Air Force, Dr. Adams has also served as an Adjunct Physics Faculty at WSU for over 20 years.
Light refreshments will be served.