%0 Journal Article
%T Reduced Chemical Kinetic Model for Titan Entries
%A Romain Savajano
%A Raffaello Sobbia
%A Michele Gaffuri
%A P¨¦n¨¦lope Leyland
%J International Journal of Chemical Engineering
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/970247
%X A reduced chemical kinetic model for Titan's atmosphere has been developed. This new model with 18 species and 28 reactions includes the mainfeatures of a more complete scheme, respecting the radiative fluxes. It has been verified against three key elements: a sensitivity analysis, the equilibrium chemical composition using shock tube simulations in CHEMKIN, and the results of computational fluid dynamics (CFDs) simulations. 1. Introduction The Saturn largest moon Titan, with its thick atmosphere rich in organic compounds and nitrogen, provides similar aspects to Earth. As a consequence, numerous scientists are interested in exploring it and are hoping for hints on how life began on Earth. Thus, it is likely that new missions will follow Cassini-Huygens and try to bring more information on this orange moon. The accurate prediction of the heat fluxes during the entry of the sounding probes is crucial to the integrity of the probe and to the quality of the protection of the scientific instruments. To investigate further the limits of these fluxes, obligatory for efficient thermal protection system design and sizing, CFDs tools are constantly developed and improved. One of the critical parameters for CFDs codes is the chemical kinetic model, as it describes the reactions schemes. However, the complexity of complete modelling is incompatible with design tools, which require fast response time simulation, and it is not necessary for such atmospheres, where the dominant species dictate the physics. The kinetic model depends primarily on the composition of the atmosphere. Despite the recent success of the Cassini-Huygens mission, uncertainties remain regarding the composition of Titan's atmosphere. The main components are N2, CH4, and Ar. One of the first kinetic models commonly used was proposed by Nelson et al. [1] in 1991. However, this first model does not take into account the formation of CN via HCN (as this species is not included). Also, as shown in many papers [2, 3], CN is a strong radiator and the radiative heat flux is predominant during Titan atmospheric entries. Moreover, the reaction rates used were not up to date. Consequently, a new chemical kinetic model was proposed by G£¿k£¿en [4], it is composed of 21 species (N2, CH4, CH3, CH2, CH, C2, H2, CN, NH, HCN, N, C, H, Ar, , CN+, N+, C+, H+, Ar+, and e£¿) and 35 reactions (rates for these reactions are given in Appendix A). Despite this new reduced model, CFDs simulations are still time and memory consuming (several hours depending on the mesh and the physics implemented). As a consequence, each
%U http://www.hindawi.com/journals/ijce/2011/970247/