Nonequilibrium effects in supersonic induction plasma

Abstract

Supersonic plasma jets find applications in plasma chemistry and plasma processing, metallurgy, experimental physics, and space technology. Usually the plasma in these jets deviates from chemical and thermal equilibrium. To optimize the industrial process detailed study of nonequilibrium effects in supersonic flow is required. In the article we apply numerical simulation to study the supersonically accelerated argon plasma flow downstream of the induction plasma torch. We compare the jets exhausting from two different convergent-divergent nozzles by means of a two-temperature model. The results show that the axial electron number density is rather convective flux controlled than recombination-ionization reaction controlled in both cases. However, the recombination resulting in electron gas heating is more essential in the jet flowing from the nozzle with a higher outlet Mach number. The composition of the jet exhausting from the nozzle with a lower outlet Mach number remains almost unchanged (“frozen”) until the end of the first expansion zone. These results confirm that the chamber pressure and the nozzle design changing leads to the induction plasma jets with different chemical conditions. For low-pressure supersonic plasma, these conditions vary from frozen to recombining. The conclusion is that depending on the industrial process, one can choose the proper torch nozzle geometry to have nonequilibrium plasma with the required properties.

Two-temperature transport coefficients in argon–helium thermal plasmas

“…The modelling of plasma processes requires two-temperature transport coefficients in order to solve with accuracy the conservation equations with their boundary conditions (see, e.g. recently [1][2][3]). Very recently, Rat et al [4,5] proposed a modified approach of the Chapman-Enskog method applied to a two-temperature thermal plasma in order to calculate the non-equilibrium transport coefficients.…”

Bulk Processing of Hydroxyapatite Nanopowder Using Radio Frequency Induction Plasma

“…The design of the supersonic plasma nozzle is the main factor contributing to the phase stability of the HA nanopowder. The plasma temperature at the supersonic nozzle outlet is close to 4000°C 24 . Therefore, the supersonic nozzle prevents the exposure of HA sol to the hottest region of the plasma where the temperature increases beyond 10 000°C.…”

“…While descending in the plasma, the liquid from the sol evaporates, and HA nucleates and grows. Therefore, HA particles travel further down the plasma stream before the decomposition process starts, where the temperature is only 1500°C 24 . Kumar et al 15,16 synthesized HA nanopowder from a suspension of 7–14 wt% HA in water using RF plasma where the phase decomposition ranged from 42% to 56%, depending on the plate power.…”

“…The plasma temperature at the supersonic nozzle outlet is close to 40001C. 24 Therefore, the supersonic nozzle prevents the exposure of HA sol to the hottest region of the plasma where the temperature increases beyond 10 0001C. While descending in the plasma, the liquid from the sol evaporates, and HA nucleates and grows.…”

“…Therefore, HA particles travel further down the plasma stream before the decomposition process starts, where the temperature is only 15001C. 24 Kumar et al 15,16 synthesized HA nanopowder from a suspension of 7-14 wt% HA in water using RF plasma where the phase decomposition ranged from 42% to 56%, depending on the plate power. The plasma heat energy flash dried, melted, and vaporized the HA powder, which led to nonbioactive phases, such as TTCP and CaO.…”