Numerical and experimental investigation on the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch

The present paper carried out the numerical simulation and experimental study of the thermofluid fields induced by a pen-like atmospheric nonthermal plasma torch, which is a very simple device to produce atmospheric plasma and has been successfully applied for surface treatment to improve the hydrophilic properties of plastic film and polyethylene. The device consists of a small cylindrical stainless steel pipe with 6.5 mm diameter and 170 mm length inserted into a ceramic tube as the inner electrode. A ring outer electrode made of stainless steel is fixed at near the edge of the ceramic. The 13.56 MHz RF power was applied between the two electrodes to produce a surface discharge. The power into the torch is 60 W. The driving gas is argon and the flow rate varies in the range of 3–12 L min −1. Fundamental research results describing the major features of the flow fields induced by the plasma torch are provided in the present study. The stress is laid on the investigation of the influence of gas flow rate, which is one of important operation conditions, on the flow fields excited by the plasma torch. The principal results show that as the power input is fixed the increase of the gas flow rate will reduce the plasma temperature. The plasma penetration length stretching toward the atmospheric surroundings is also found to be closely related with the gas flow rate. Experimental confirmation by measuring the rotational temperature using optical spectroscopic method has been carried out, and a reasonable agreement between calculation and experiment has been obtained. These results provide fundamental understanding of the thermofluid fields induced by a pen-like atmospheric plasma torch, and also build up a basic predictive capability by numerical simulations to perform the further detailed investigation for practical applications in future.