3D infrared temperature maps measurements of ablative materials during plasma wind tunnel experiments

Abstract

Accurate surface temperature and recession measurements are crucial experimental data for plasma wind tunnel testing of ablative thermal protection materials. In this work we propose a novel methodology to reconstruct infrared temperature maps on 3D geometries undergoing surface recession. An optical calibration technique is used to extract 3D metric information from the 2D thermal images, thanks to a specific calibration target with control points. The evolution of the sample shape during the experiment is tracked from a side view, using a visual-range camera with dedicated image processing, and reconstructed in 3D under the assumption of axisymmetry. The surface temperature is projected on the time-varying 3D geometry from the calibrated thermograms. The technique is demonstrated on a graphite ablation experiment in air plasma. The reconstructed maps provide detailed multidimensional information about the transient temperature evolution, overcoming traditional approaches that are limited around the stagnation point. The technique allows to study ablation mechanisms with further detail, improving experimental data for material qualification and validation of simulation codes.