Investigation of CN in the Reacting Boundary Layer of Ablating Graphite using PLIF

Abstract

Planar Laser Induced Fluorescence (PLIF) of CN is used to study graphite ablation during exposure to an atmosphericpressure, high-temperature air flow. The 5000 K to 6000 K air flow is produced by the 50 kW Inductively Coupled Plasma (ICP) Torch at The University of Texas at Austin. Temporally- and spatially- resolved PLIF imaging is used to offer insight into reaction layer behavior. Two-line LIF thermometry in the reaction layer is also used, where the temperature is inferred from the ratio of signal intensities resulting from pumping two rotational lines, while collecting the broadband fluorescence. PLIF results are compared to s imultaneously-collected optical emission spectra. This work represents a first s tep towards building a better understanding of the thermo-chemical environment and the chemical kinetics of high-temperature material ablation, and provides insights into the production of CN during the ablation of carbon-based ablators in hypersonic applications.