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Laser-induced ignition in nonpremixed methane-oxygen flows

Event Type: 
Date and Time: 
Friday, May 13, 2022 - 16:15
Location: 
Building 300, Room 300
Event Sponsor: 
Parviz Moin, Director of Center for Turbulence Research
Speaker(s): 
Dr. Jonathan Wang

Laser-induced breakdown is a versatile means of depositing energy in a gas and seeding ignition of a combustible mixture, and it offers multiple advantages over conventional approaches.  To analyze the laser-generated flow and ensuing ignition dynamics, direct numerical simulations are conducted in several configurations: a quiescent gas, a temporally evolving shear layer, and a model gas-gas rocket combustor.  Consistent with experimental observation, it is shown that ignition is possible even when energy is deposited in a non-flammable region of the flow, due to a laser-generated vortex of hot, radical-rich gas.  In contrast to directly depositing energy in a premixed region, this mode of ignition crucially depends on the reacting vortex and its thermochemistry as it interacts with local mixture and flow gradients.  It is also shown that ignition is critically mediated by turbulent fluctuations: changing the instantaneous pre-ignition flow alone, while preserving all statistics exactly, can be sufficient to produce different ignition outcomes.

Bio: 
Dr. Jonathan Wang is a postdoctoral fellow at CTR at Stanford University. He earned his PhD in Theoretical and Applied Mechanics at the University of Illinois Urbana-Champaign, and his thesis focused on the flow and ignition dynamics of laser-induced breakdowns. He joined CTR in 2020, where he works as part of the Predictive Science Academic Alliance Program studying laser-induced ignition for rocket combustion. His interests are in compressible, chemically reacting flows and nonequilibrium flows.