The Roles of Atomic Oxygen and Nitric Oxide in Low Temperature Plasmas Sherrie Bowman, David Burnette, Ivan Schkurenkov, Walter Lempert 68 th International Symposium on Molecular Spectroscopy June 18, 2013 Michael A. Chaszeyka Nonequilibrium Thermodynamics LaboratoryDept. of Mechanical and Aerospace Engineering

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Outline of Presentation Dept. of Mechanical and Aerospace Engineering 1.Literature Review and Background Information -Plasma Assisted Combustion -Laser Diagnostics and Kinetic Modeling 2.Characterization of Plasma -Images -Current and Voltage Measurements 3.Results and Kinetic Modeling -Atomic Oxygen -Nitric Oxide -Atomic Nitrogen 4. Conclusions and Future Work

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory What Are Plasmas? What is PAC? Dept. of Mechanical and Aerospace Engineering Non-Thermal, Cold Plasma : Weakly ionized gas (~1% ions) that has electrons at a significantly higher temperature than ions (non-equilibrium). Uses: Surface etching Catalysis Welding, cutting, spraying Medicine Plasma Thrusters Plasma Assisted Combustion (PAC) Plasma Assisted Combustion: Ignition delay time Ignition/Flame temperature Flame stabilization S. Samukawa, M. Hori, S. Rauf, K. Tachibana, P. Bruggeman, G. Kroesen, J. Whitehead, A. Murphy, A. Gutsol, S. Starikovskaia, U. Kortshagen, J. Boeuf, T. Sommerer, M. Kushner, U. Czarnetzki, and N. Mason. “The 2012 Plasma Roadmap” J. Phys. D: Appl. Phys. 45 (2012)

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Background: CH 4 /Air Flame Stabilization Dept. of Mechanical and Aerospace Engineering Plasma generates relatively stable intermediate species, H 2 and CO, which play a key role in flame stabilization Kim, W., M.G. Mungal, and M.A. Cappelli. "The Role of In Situ Reforming in Plasma Enhanced Ultra Lean Premixed Methane/Air Flames" Combustion and Flame Radicals are produced in Stream A. 2. Radicals rapidly form intermediate species that move outward from the inner flame. 3. The intermediate species eventually ignite Stream B. *When no ignition, H 2 CO formation is significant. (OSU)

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Previous Work: Atomic Oxygen TALIF in Air/Fuel Mixtures Dept. of Mechanical and Aerospace Engineering O atom decay in C 2 H 4 /air is more rapid than in air by a factor of ~ 100 O + O 2 +M → O 3 +M O + O 3 → O 2 + O 2 O + C 2 H 4 → CH 3 + HCO O + C 2 H 4 → H + CH 2 CHO Modeled Pulser energy = 0.76mJ/pulse Uddi, M., N. Jiang, E. Mintusov, I.V. Adamovich, and W.R. Lempert, "Atomic Oxygen Measurements in Air and Air/Fuel Nanosecond Pulse Discharges by Two Photon Laser Induced Fluorescence" Proceedings of the Combustion Institute

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory PAC Studies at Ohio State Dept. of Mechanical and Aerospace Engineering The study of kinetics of air/fuel plasmas at low temperature ( K). Recent Studies: OH, T, T v, H atoms (soon) This Study: O, N, and NO Creation of O atoms is considered the single most important effect from application of a discharge. Zeldovich’s Mechanism: N 2 + O → NO + N O 2 + N → NO + O *We want to obtain experimental data sets for all three species involved and, where possible, compare to kinetic models.*

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory LIF: Nitric Oxide Dept. of Mechanical and Aerospace Engineering Calibration: Comparison with 4.0 ppm NO in N 2 gas (60 Torr total pressure). Experimental Concerns: NO is a strong absorber of laser beam. (Minimize region of interest) Interference from other species. (Nearly negligible at low T)

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory TALIF: Atomic O and N Dept. of Mechanical and Aerospace Engineering Two Photon LIF:Lower signal levels Calibration via comparison with a known noble gas (~55 Torr of Xenon or Krypton)

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Schematic Diagram of Experimental Apparatus Dept. of Mechanical and Aerospace Engineering

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Pin-to-Pin Discharge Dept. of Mechanical and Aerospace Engineering Bare Metal Electrodes: ∙Spherical ∙7.5 mm diameter ∙10 mm gap

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Characteristics of Plasma Dept. of Mechanical and Aerospace Engineering cm -1 /molecule eV/molecule

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory TALIF Results – Air Dept. of Mechanical and Aerospace Engineering Air  fuel P = 40 Torr Plasma Rep Rate = 60 Hz Laser Rep Rate = 10 Hz Black Dots: Experiment Red Curve: Modeling Peak in experimental [O] reproducible but not reproduced by the model.

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Results – NO and N in Air Dept. of Mechanical and Aerospace Engineering Air No fuel P = 40 Torr Plasma Rep Rate = 60 Hz Laser Rep Rate = 10 Hz Dots: Experimental Results Lines: Modeling Predictions N 2 + O → NO + N k = 5.0 x cm 3 /s O 2 + N → NO + O k = 9.1 x cm 3 /s

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Results – NO and N in Air with H 2 Fuel Dept. of Mechanical and Aerospace Engineering Air H 2 fuel,  =0.5 P = 40 Torr Plasma Rep Rate = 60 Hz Laser Rep Rate = 10 Hz Dots: Experimental Results Lines: Modeling Predictions NO + H 2 → H + HNO k = 1.6 x cm 3 /s NO + H 2 → NH 2 + O k = 2.14 x cm 3 /s

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Conclusions and Ongoing Work Dept. of Mechanical and Aerospace Engineering It was found that: ∙Significantly high energy (8mJ/pulse, cm -1 /molecule) was coupled to the plasma. ∙O atom loss can be modeled reasonably accurately in this configuration for air. (Differences potentially due to Zeldovich mechanism) NO + N → N 2 + O NO + O → O 2 + N ∙ NO and N mechanism qualitatively matches modeling predictions based on the Zeldovich mechanism (in air). ∙NO and N mechanism follows expected trends and matches modeling predictions quite well (with H 2 fuel). Current work: ∙Additional experiments at various pressures and different fuels: H 2, CH 4, C 2 H 4, C 3 H 8, etc. ∙Additional modeling calculations with and without fuels.

Michael A. Chaszeyka Nonequilibrium Thermodynamics Laboratory Acknowledgements Dept. of Mechanical and Aerospace Engineering - Air Force Office of Scientific Research Chiping Li – Technical Monitor -Dr. Keisuke Takashima