Numerical Study on Modulation Induced Entrainment Gas Flow and its Promotion of Nanopowder Synthesis in Pulse-Modulated Induction Thermal Plasmas *

A numerical study was conducted for our unique and original method for PMITP+TCFF method for high-production rate nanopowder synthesis. The PMITP is pulse-modulated induction thermal plasma, while TCFF is time-controlled feedstock feeding (TCFF). The PMITP provide a periodically alternating thermal plasma fields between an extremely high-temperature plasma in on-time and a relatively low-temperature plasma in off-time. Feedstock particles are intermittently injected synchronized with on-time of the PMITP for efficient evaporation of feedstock during on-time and for efficient nucleation of nanoparticles during off-time. The developed numerical model combines the calculations of the PMITP field, dynamics of feedstock particles with two-way interactions between PMITP and feedstock particles, and the moment transport for aerosol considering homogeneous nucleation, heterogeneous condensation. Using the developed method, we newly found that modulation of the thermal plasma field can induce strong entrainment gas flow downstream of the plasma torch, which can remarkably promote nucleation of nanoparticles. This entrainment gas flow can be controlled by modulation conditions.