Nonequilibrium plasma chemistry has been extensively studied recently due to its importance for a variety of engineering applications such as fuel reforming, hazardous emissions reduction,plasma assisted combustion, and plasma flow control. The use of nonequilibrium plasmas for these applications requires both understanding of fundamental kinetic processes involved, and the ability to generate, control, and characterize these plasmas at high pressures, high energy loadings, and in large volumes (over large surface areas). A promising method of generating large-volume, diffuse nonequilibrium plasmas in a wide range of pressures is what is known as the Fast Ionization Wave (FIW) discharge. In this approach, high peak voltage (approximately 10-100 kiloVolt),approximately 10-100 nanosecond duration voltage pulses are used to generate an ionization wave (wave speed of a few cm/nsec) propagating over large distances, up to several tens of centimeters. High electron energy achieved in the wave front dramatically accelerates key plasma processes such as molecular dissociation, thus generating reactive radical species. The project focuses on a comprehensive and fundamental experimental study of the physics and chemistry of FIW plasmas, featuring incorporation of a comprehensive suite of laser-baseed optical diagnostic techniques.
In addition its technical goals, the program will also reflect many of the stated NSF criteria for broader impact. In particular, the program will advance "discovery and understanding" by i), direct involvement of graduate and undergraduate students, and ii), incorporation of the diagnostic methods, modeling tools, and principal findings into the undergraduate and graduate Mechanical Engineering curriculum at OSU. Every effort will also be made to broaden the participation in the research program of individuals from groups traditionally underrepresented in mechanical engineering and chemistry. The continued development FIW technology will also serve to enhance the high pressure plasma infrastructure of the U.S (and the world), potentially enabling a wide variety of applications such as: ignition and flame-holding in next generation high speed jet aircraft; high power gas dynamic lasers; and plasma aerodynamic flow control. The co-PIs are actively engaged in the transfer of plasma and advanced optical diagnostic technology as it is continually developed, to the government and industrial sectors through collaborations with the U.S Air Force, NASA, and a variety of small businesses. Finally, by maintaining an active web site, and by student and PI participation in national and international meetings, the principal findings will be rapidly disseminated to the scientific and educational communities at large.
This program has focused on six primary activities which involved two experimental platforms, an axisymmetric non-equilibrium plasma, and a Fast Ionization Wave (FIW) discharge. More specifically the program focused on (i)., The study of vibrational energy loading and loss in nitrogen and air plasmas in which it was found that energy transfer from excited electronic states is likely to be playing an important role in the plasma kinetics; (ii)., Studies of the kinetics of formation and loss of nitric oxide, NO, a significant atmospheric pollutant, which was found to be formed by reaction of atomic oxygen with electronically excited N2 ; (iii)., The observation of fuel reforming, the process by which large liquid hydrocarbons are converted to smaller, more readily combustible, small gaseous hydrocarbons, by a surface Fast Ionization Wave (FIW) discharge. The has the potential to be used to augment high speed combustion, such as that utilized in modern aircraft, without reliance on a traditional solid state catalyst; (iv)., Fundamental measurements of the temporal evolution of electron density and temperature in non-equilibrium discharges, which provides critical data for predictive modeling of non-equilibrium plasamas; (v)., The development of a new optical diagnostic technique for determination of the time and space-resolved electric field with sub-nanosecond temporal resolution, and (vi)., The development of new two-dimensional non-equilibrium plasma modeling capability. With respect to Broader Impacts this program has partially supported a total of four different PhD graduate students, who participated in a program that combined unique FIW discharge technology with advanced optical diagnostics and modeling. In addition all of the graduate students actively participated in the dissemination of this material to the broader community by the presentation of their work at technical meetings. The program also supported one undergraduate student, Mr. Ben Musci, who assisted the graduate students in the laboratory and who fabricated some of the elements of the experimental instrumentation they utilized to perform this research. This program also significantly impacted the scientific infrastructure in the U.S (and the world). In particular, the repetitively pulsed, FIW discharge constitutes a unique new tool for both fundamental studies of non-equilibrium plasmas, and for potential application to a wide variety of real plasma-based applications.
