An experimental and computational study of the interaction between the jet of an ICP torch and a cylidrical substrate

Summary form only given. Several industrial and research and development processes can possibly make use of Inductively Coupled Plasma (ICP) torches in the interaction with either a static or a rotating cylindrical substrate; like for high purity silica overcladding of preforms for optical fiber production, as well as in some calibration procedure for high precision measurement of physical properties of materials and, generally, in the frame of thermal treatment techniques, with or without chemical synthesis and deposition of materials. The investigation of thermo-fluid-dynamic phenomena in the downstream plasma region of interaction with the substrate is important in order to optimize these processes, also taking advantage of the many operating and geometric parameters intrinsic in the use of ICP plasmas. The interaction between cylindrical rods of different diameters (4, 8, 16 mm) and materials (stainless steel and quartz), placed at different distances (30 and 40 mm) from the exit region of an ICP torch operated in Ar at 13.56 MHz and 500 W at atmospheric pressure has been investigated using Schlieren Imaging (SI) with a Z-type setup; substrate temperature measurements have been obtained using infrared temperature sensors. Two different points of view of the same experimental set-up have been used for SI: one with the camera axis coaxial with the rod axis, while another one with the camera axis perpendicular to both rod and torch axis, as shown in Fig. 1. Hot-spot temperature on the surface of the substrate has been measured with infrared sensors (Optris LTCF1); results are compared with T distribution obtained with 3D simulation of the region where the substrate interacts with the impinging jet; axisymmetric 2D simulation of the volumetric region where plasma is generated has been used. Experimentally derived temperatures are also used to validate the simulation model and to “tune” it with the aim of choosing the best physical description of the- turbulent phenomena occurring downstream the torch. Future studies will concern the analysis of substrate under rotation and/or translation.