UVM Theses and Dissertations
Format:
Print
Author:
Lutz, Andrew J.
Dept./Program:
Mechanical Engineering
Year:
2011
Degree:
MS
Abstract:
The computational fluid dynamics codes used to calculate ablative heat shield thickness are limited by a lack of fundamental data for critical gas-surface interactions and chemical reaction rates. One such interaction is carbon nitridation, Cs +N - CN⁻, where atomic nitrogen extracts solid carbon from a heat shield surface. Few measurements have been performed for this reaction at conditions relevant to re-entry, and large differences exist in reported values. Experiments aimed at measuring this particular gas-surface reaction rate have been conducted recently in the 30 kW Inductively Coupled Plasma Torch Facility at the University of Vermont, which simulates re-entry conditions on scaled material samples.
Two-photon laser-induced fluorescence is used to measure nitrogen atom density and translational temperature in the reacting boundary layer above the graphite surface, which factor into the calculation for the nitrogen atom flux reaching the surface. The carbon mass flux from the surface is estimated from a mass loss measurement and the nitridation rate is then estimated from a simple kinetic model. Initial tests were done with modest surface temperatures in the range of 1620 to 1800 K. Experimental results are compared with a non-equilibrium boundary layer flow code for validation.
Two-photon laser-induced fluorescence is used to measure nitrogen atom density and translational temperature in the reacting boundary layer above the graphite surface, which factor into the calculation for the nitrogen atom flux reaching the surface. The carbon mass flux from the surface is estimated from a mass loss measurement and the nitridation rate is then estimated from a simple kinetic model. Initial tests were done with modest surface temperatures in the range of 1620 to 1800 K. Experimental results are compared with a non-equilibrium boundary layer flow code for validation.