AEM Seminar: TODAY, January 20th - Asst Prof Marien Simeni, Department of Mechanical Engineering, University of Minnesota - Twin Cities
Molly Schmitz
Spring 2023 Seminar Series
AEM Seminar: Nanosecond Pulsed Discharges as Testbeds for Nonequilibrium Kinetics
Abstract:
Plasmas sources are prominent candidates to resolve many of the listed grand challenges for engineering. Among these sources, nanosecond pulsed discharges have proven to be particularly versatile when it comes to a variety of applications (plasma flow actuation, plasma-assisted combustion and removal of volatile organic compounds). Besides their practical use in industry, these discharges have also shown to be formidable testbeds for nonequilibrium kinetics. For instance, nonequilibrium-based kinetics leading to gas heating rates as high as 5x10 10 K*s -1 has been recently observed in air and explained in such discharges. This fast heat release found an application in the reduction of ignition delays in combustion engines, showing the interplay between nonequilibrium kinetics and applications. Nevertheless, the explanatory mechanism of the latter process involves energy transfer from nitrogen electronically excited levels: N 2 (A, B, C) populated on the nanosecond time-scale by electron-impact excitation of nitrogen molecules. This was only evidenced by rigorous time-resolved measurements of gas temperature, electron density and densities of N 2 (A, B, C). In this talk, I will highlight through a few examples how highly spatio-temporally resolved optical and laser-based diagnostics are critical in furthering our understanding of nonequilibrium kinetics in plasmas. I will also demonstrate new (high-sensitivity) spectroscopic strategies to probe fundamental quantities in plasmas such as the electric field strength. Finally, I will show how these recent advances could help realizing breakthroughs in the field of extreme ultraviolet lithography.
Bio:
Marien Simeni is currently (since April 2022) Assistant Professor at the department of Mechanical Engineering of the University of Minnesota. Before joining UMN, he was an Associate Research Physicist at the Princeton Plasma Physics Laboratory (2020-2022). He previously earned a PhD in Aerospace Engineering from Ecole Centrale Paris (France, 2015) and a BS in fundamental physics from Ecole Normale Superieure Cachan (France, 2010). His research focuses on the development of advanced optical diagnostics for low to high pressure plasmas as well as the generation of extreme ultraviolet and soft x-ray light sources for photolithography. He is the first recipient of the Robert Ellis Jr postdoctoral Fellowship in plasma physics.
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Molly Schmitz
Spring 2023 Seminar Series
AEM Seminar: Multi-Physics Modeling for Future Propulsion and Power Systems: high-pressure phase separation and plasma assisted ignition
Abstract:
In the development of advanced propulsion and power systems, the growing concerns about emissions and efficiency and the pursuit of high speeds have pushed the systems to operate at extreme conditions. These conditions and the corresponding technical solutions often introduce more physics, which brings new challenges to modeling and simulation. In this presentation, I will talk about two examples of such multi-physics modeling from our recent works: (1) Advanced gas turbines and detonation engines operate at high pressures for high power density and efficiency. At such conditions, the injected multicomponent liquid propellants and fuel-air mixtures often go through thermodynamically transcritical phase change. We developed a CFD framework based on the first-principle vapor-liquid equilibrium (VLE) theory to accurately predict high-pressure phase change, and demonstrated that phase separation can be triggered by either mixing or expansion waves. (2) Plasma assisted combustion (PAC) is a promising technology to enable ignition and stable combustion either at extreme conditions (e.g., high-speed flows in scramjets) or using low-reactivity fuels (e.g., carbon-free ammonia). We developed a series of 0D-3D CFD solvers to model PAC with different levels of fidelity. Using our solvers, we figured out why plasma can surprisingly reduce the NOx emission of ammonia combustion and investigated how turbulence and pulsing frequency affect plasma assisted ignition performance.
Bio:
Dr. Suo Yang is a Richard and Barbara Nelson Assistant Professor of Mechanical Engineering at the University of Minnesota - Twin Cities. During 2017-2018, Dr. Yang was a Postdoctoral Research Associate in Mechanical and Aerospace Engineering at Princeton University. He received Ph.D. (2017) and M.S. (2014) degrees in Aerospace Engineering, and another M.S. degree in Computational Science and Engineering (2015), all from Georgia Institute of Technology. He received a B.S. degree in Mathematics and Applied Mathematics from Zhejiang University in 2011. Dr. Yang's research focuses on the modeling and simulation of turbulent reacting and multiphase flows, including combustion, plasma, particulate and multiphase flows, and hypersonics, with applications to propulsion and energy systems. He has been authored for more than 60 peer-reviewed journal articles and referred conference papers with Google Citations of 1,000+ and a Google H-Index of 18, in which he received Editor's Pick and Featured Article awards from Physics of Fluids and Combustion and Flame. Dr. Yang is a recipient of the DARPA Young Faculty Award (YFA) and ONR Young Investigator Program (YIP) Award. His research is supported by NSF, ARL, ARO, DARPA, ONR, AFRL, ARPA-E, and ExxonMobil. Dr. Yang is a Senior Member of AIAA and a committee member of three AIAA Technical Committees. He also serves as an active reviewer for many high top-tier journals for which he received three Outstanding Reviewer Awards.