Particle modeling of non-equilibrium field emission driven RF microplasmas
Non-equilibrium microplasmas at atmospheric pressures have been investigated for active flow control, micropropulsion and electronic display applications to name a few. The operational voltages for these microplasmas are on the order of kilovolts. When the electric field at the electrodes reaches GV/m or tens of GV/m either due to reduced interelectrode spacing and surface irregularities or due to carefully designed nanostructures on the electrodes, quantum processes such as field emission and field ionization come into effect. These can potentially reduce the operational voltages of microplasma devices by an order of magnitude. Due to the rarefied and non-equilibrium nature of these microplasmas, they are modeled here using particle-in-cell method with Monte Carlo collisions (PIC/MCC) and the developed collision model is validated. The voltage-current characteristics of the field emission driven microdischarges indicate the absence of the glow regime because field emission replaces secondary emission as the discharge sustaining mechanism. At low pressures, microplasma driven by field ionization and field emission, enabled by nanostructures on electrodes is found to be operational at voltages less than 100 V. At high pressures, a feasibility study on the concept of flow actuation by dielectric barrier discharge using field emission (FE-DBD) is performed. Theoretical analysis and simulations for microplasma actuated planar Poiseuille flow show that the gain in flow rate is inversely proportional to the Reynolds number. The increase in gas temperature due to Joule heating, indicates FE-DBD's potential for microcombustion, micropropulsion and chemical sensing in addition to microscale pumping and mixing applications, with operational voltages an order of magnitude lower than the conventional DBDs.
Alexeenko, Purdue University.
Aerospace engineering|Mechanical engineering|Plasma physics
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