Characterization of the VKI Plasmatron subsonic ICP jet combining optical emission spectroscopy, intrusive measurements, and CFD simulations

TL;DR

This study combines optical emission spectroscopy, intrusive measurements, and CFD simulations to comprehensively characterize the subsonic ICP jet in a wind tunnel, improving understanding and modeling of the flow and heat transfer.

Contribution

It introduces an integrated methodology for ICP jet characterization using advanced spectroscopy, measurements, and simulations, enhancing accuracy over traditional approaches.

Findings

Emission spectra agree with thermochemical equilibrium predictions.

The proposed forward procedure accurately predicts stagnation line flow.

A consistent framework between simulations and experiments is established.

Abstract

This paper addresses the characterization of the subsonic flow in the 1.2~MW Inductively Coupled Plasma (ICP) wind tunnel at the von Karman Institute for Fluid Dynamics (VKI), targeting chamber pressures of 50 and 100~mbar, and input electric powers between 150 and 300~kW. Ultraviolet to near-infrared optical emission spectroscopy measurements of the free-jet flow are carried out with an updated experimental set-up, calibration procedure, and data processing, providing high-quality absolute spatially-resolved emission spectra. Emission measurements agree with thermochemical equilibrium predictions within a range of conditions, allowing to extract experimental maps of cold-wall heat flux and dynamic pressure against the inferred free-jet enthalpy. A detailed comparison with the characterization methodology traditionally employed is presented, highlighting the need for an improved modeling strategy. Using the measured free-jet temperature and dynamic pressure only, a forward procedure for the computation of the stagnation line flow is proposed. The latter agrees with intrusive heat flux measurements through a range of test conditions, and for values of the recombination coefficient of the reference copper probe commonly found in the literature. Results demonstrate that a consistent framework between numerical simulations and experimental data can be achieved, defining an improved framework for the characterization of the subsonic ICP jet.