Simulation of the ignition transient in RF inductively-coupled plasma torches

The paper deals with the time-dependent numerical simulation of inductively-coupled plasma torches during the ignition transient, which is induced by a graphite rod and leads to the final, self-sustaining plasma condition. The study has been performed by using a 2D time-dependent fluid-magnetic code based on the SIMPLER algorithm within the assumptions of laminar flow, local thermodynamic equilibrium conditions and optically thin plasma. The graphite rod has been treated as a real obstacle for the gas and the electron emission due to the thermoionic effect has been suitably taken into account. The advantage of using a time-dependent code in order to select different plasma operating conditions that can lead to stable discharges is pointed out. Results for both argon and air discharges are presented for different torch geometries, RF frequencies and inlet gas configurations (also including the presence of a carrier gas injected along the axis of the torch). Moreover, the final self-sustaining plasma configurations obtained are compared, when available, with results coming from static models, which have been published by other authors.