Simulation studies of micrometer scale dielectric barrier discharges for microthruster applications

Summary form only given. The recently designed Microplasma thruster employs the use of direct-current (DC) microdischarge to cause heating of argon gas during the expansion process through a nozzle. This helps in enhancing the cold gas thrust. However, one of the deficiencies of direct-current microdischarges is the need for exposed electrodes that incur ion bombardment with large thermal fluxes and consequently subject to wear. A different approach is to use an alternating current (AC) with electrodes covered by a suitable dielectric to prevent electrode erosion. The discharge will then be similar to a micrometer scale Dielectric Barrier Discharge (micro-DBD). It is thus important to investigate the power densities that are attained by this system and assess its effectiveness in gas heating. Classical large-scale (mm gap) Dielectric Barrier Discharges (DBD) is used in excimer lamps, ozone generation and in materials processing and are not subject to any significant gas heating. In this study we compare the gas heating effects in a micro-DBD and a classical large-scale DBD over a range of frequencies.A detailed first-principles computational model is used to provide time-accurate solutions of multi-species, multitemperature, self consistent plasma governing equations for the discharge physics. We use a finite rate argon chemistry which has been validated through simulations on micro hollow cathode discharges. The paper will present details of important discharge parameters, power densities and gas temperature in a micro DBD and a millimeter scale classic DBD.