Transient simulation of the oscillatory injection of water–ethanol mixtures into an inductively-coupled radio frequency thermal plasma

Abstract This study investigates the effects of oscillatory water–ethanol injection on the temperature, velocity, and species distributions within an inductively-coupled radio frequency (RF) thermal plasma, using a transient 2D-axisymmetric computational fluid dynamics model. The simulation models a TEKNA PL-35 RF plasma torch, operated with an argon–oxygen gas mixture, accounting for various species such as electrons, atoms, molecules, and ions. The water–ethanol solution is injected through a probe into the plasma core with sinusoidal velocity, replicating the effects of a peristaltic pump. Validation of the model is performed through comparison with previously published numerical data, demonstrating good conformity. The study explores the influence of frequency and molar concentration of the injected water–ethanol mixture, and operating pressure on key plasma characteristics, including electron density and temperature distribution. Results indicate that applying an oscillatory velocity pattern for central fluid injection into the plasma reduces the overall plasma temperature, particularly near the probe outlet. Additionally, it leads to a more uniform temperature distribution by decreasing sharp temperature gradients at the torch outlet. Furthermore, higher operating pressures increase electron density, which enhances energy transfer through mechanisms such as electron impact reactions. This improved energy transfer promotes a more uniform temperature distribution, leading to greater plasma uniformity. These results suggest that the oscillatory injection can promote more uniform heating of precursor materials, which is vital for applications such as coating deposition and powder synthesis.