Investigation of Pyrolysis Gas Chemistry in an Inductively Coupled Plasma Facility

摘要

The pyrolysis mechanics of Phenolic Impregnated Carbon Ablators (PICA) makes it a valued material for use in thermal protection systems for spacecraft atmospheric re-entry. The present study of the interaction of pyrolysis gases and char with plasma gases in the boundary layer over PICA and its substrate, FiberForm, extends previous work on this topic that has been done in the UVM 30 kW Inductively Coupled Plasma (ICP) Torch Facility. Exposure of these material samples separately to argon, nitrogen, oxygen, air plasmas, and combinations of said test gases provides insight into the evolution of the pyrolysis gases as they react with the different plasmas. Measurements done to date include time-resolved absolute emission spectroscopy, location-based temperature response, and more recently, spatially resolved and high-resolution emission spectroscopy, all of which provide measure of the characteristics of the pyrolysis chemistry and material response. Tests with relatively inert argon plasmas established a baseline for the pyrolysis gases that leave the material. CN Violet bands, NH, OH and Hydrogen Alpha (H_α) lines were seen with relative repeatability in temporal, spectral, and intensity values. Tests with incremental addition of reactive plasmas (diluted nitrogen and oxygen) provided a preliminary image of how the gases interacted with atmospheric flows. Evidence of a temporal relationship between NH and H_α relating to nitrogen addition is seen, while oxygen addition sharply reduced the signal of previously seen pyrolysis gases. Temperature analysis highlighted the reaction of the material to oxygen addition and displayed the in depth material response to argon and air/argon plasmas. The development of spatial emission analysis has been started with the hope of better resolving the previously seen.