Plasma-flow interactions in field-emission discharges with applications in microcombustion

Abstract

Field emission based microplasma actuators generate highly non-neutral surface discharges that can be used to heat, pump, and mix the flow through microchannels and offer an innovative solution to the problems associated with microcombustion. They provide a constant source of heat to counter the large heat loss through the combustor surface, they aid in flow transport at low Reynolds numbers without the use of moving parts, and they provide a constant supply of radicals to promote chain branching reactions. In this work, we present two actuator concepts for the generation of field emission microplasma, one with offset electrodes and the other with planar electrodes. They operate at input voltages in the 275–325 V range at a frequency of 1 GHz which is found to be the most suitable value for flow enhancement. The momentum and energy imparted by the charged particles to the neutrals as modeled by 2D particle-in-cell with Monte Carlo collisions are applied to actuate flow in microchannels using 2D computational fluid dynamics modeling. The planar electrode configuration is found to be more suitable for the purpose of heating, igniting and mixing the flow, as well as improving its residence time through a 10 mm long microcombustor. The combustion of hydrogen and air with the help of 4 such actuators, each with a power consumption of 47.5 mW cm−1, generates power with an efficiency of 90.5%. Such microcombustors can be applied to all battery based systems requiring micropower generation with the the ultimate goal of ‘generating power on a chip’.