Control of Nitrogen Atomic Density and Enthalpy Flow Into Reaction Chamber in $\hbox {Ar/N}_{2}$ Pulse-Modulated Induction Thermal Plasmas

Simultaneous control of the nitrogen atomic density and the enthalpy flow onto the specimen installed downstream of the plasma torch was accomplished using Ar/N₂ pulse-modulated induction thermal plasmas (PMITPs). Such simultaneous control was difficult to realize because the increasing input power into conventional nonmodulation thermal plasmas increases the number density of the nitrogen atoms, but it also increases the enthalpy flow onto the specimen. The behavior of the excited nitrogen atoms was measured through spectroscopic observation. The specimen´s surface temperature was measured using a radiation thermometer. Then, the net enthalpy flow onto the specimen was estimated. Results showed that the modulation of coil current increases the time-averaged nitrogen atomic density and decreases the time-averaged enthalpy flow during the modulation cycle onto the specimen irradiated by the Ar/N₂ PMITP. This result was confirmed by results from the developed 2-D two-temperature chemical nonequilibrium model of the Ar/N₂ PMITP