Physical contamination results from a competition between the deposition of incoming contaminants and their reemission, depending on the surface temperature. However, interaction with ultraviolet light greatly inhibits reemission. Ultraviolet light can lead to chemical reactions, bonding contaminants to the substrate or nearby molecules. This effect can have important consequences in flight. This is especially true for hot surfaces that show no contamination in the absence of ultraviolet light due to their high temperature and can nevertheless be significantly contaminated through photofixation. Previous studies conducted by ONERA–The French Aerospace Lab with Centre National d’Etudes Spatiales allowed identifying the physical mechanisms involved in photofixation and led to a sufficiently simple model to be implemented in engineering software. In this model, the substrate excitation is followed by the reaction of adsorbed contaminants with excited sites. Contaminant chemical photofixation thus results from the competition between their reemission and their reaction with excited sites. This paper presents the implementation of this photofixation model in the numerical tool COMOVA and its validation. It was carried out by modeling test cases, including ground experiments. It demonstrated the qualitative coherence of the photofixation model. The simplest experimental cases with pure contaminants, which have analytical solutions, also quantitatively validated the physical model and its numerical implementation.


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    Title :

    Ultraviolet Fixation of Molecular Contamination: Physical Model Numerical Implementation and Validation




    Publication date :

    2016




    Type of media :

    Article (Journal)


    Type of material :

    Print


    Language :

    English



    Classification :

    Local classification TIB:    770/7040
    BKL:    55.60 Raumfahrttechnik



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