On the formation and accumulation of solid carbon particles in high-enthalpy flows mimicking re-entry in the Titan atmosphere

Antonio Esposito, Marcello Lappa, Gennaro Zuppardi, Christophe Allouis, Barbara Apicella, Mario Commodo, Patrizia Minutolo, Carmela Russo

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Abstract

The problem relating to the formation of solid particles enabled by hypersonic re-entry in methane-containing atmospheres (such as that of Titan) has been tackled in the framework of a combined experimental-numerical approach implemented via a three-level analysis hierarchy. First experimental tests have been conducted using a wind tunnel driven by an industrial arc-heated facility operating with nitrogen as working gas (the SPES, i.e., the Small Planetary Entry Simulator). The formation of solid phases as a result of the complex chemical reactions established in such conditions has been detected and quantitatively measured with high accuracy. In a second stage of the study, insights into the related formation process have been obtained by using multispecies models relying on the NASA CEA code and the Direct Simulation Monte Carlo (DSMC) method. Through this approach the range of flow enthalpies in which carbonaceous deposits can be formed has been identified, obtaining good agreement with the experimental findings. Finally, the deposited substance has been analyzed by means of a set of complementary diagnostic techniques, i.e., SEM, spectroscopy (Raman, FTIR, UV-visible absorption and fluorescence), GC-MS and TGA. It has been found that carbon produced by the interaction of the simulated Titan atmosphere with a solid probe at very high temperatures can be separated into two chemically different fractions, which also include "tholins".

Original languageEnglish
Article number93
Number of pages16
JournalFluids
Volume5
Issue number2
DOIs
Publication statusPublished - 12 Jun 2020

Keywords

  • hypersonic flow
  • methane
  • chemical reactions
  • solid particles
  • arc-heated facility
  • direct simulation
  • Monte Carlo method

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