Molecular simulations are performed of high temperature dissociated oxygen reacting with an idealized carbon-carbon composite material, where the microstructure is resolved. The Direct Simulation Monte Carlo (DSMC) method is used to simulate the convection and diffusion of reactants towards the microstructure and the transport of surface reaction products away from the microstructure. Simulations are performed with and without gas-phase chemical reactions in order to determine the relative importance of gas-surface reactions compared to gas-phase reactions next to the material surface. The simulations incorporate reaction probabilities for individual gas-surface collisions based on new reactive scattering data obtained in a molecular beam facility. The molecular beam experiments clearly indicate that a majority of surface reaction products were produced through thermal mechanisms. The experiments provide detailed data on the relative magnitude of O, O2, CO, and CO2 scattering from a representative material sample, made of vitreous carbon. For a gas-surface temperature of 800K, it is found from the simulations that despite CO being the dominant surface reaction product, a gas-phase exchange reaction forms significant CO2 within the microstructure region. The amount of CO2 production within the microstructure region is shown to be dependent on the local Knudsen number, based on the exposed microstructure height. Finally, preliminary simulations are performed for a real Carbon- Carbon (C-C) surface. The surface topology is obtained through X-ray microtomography of an ablated C-C sample, which is triangulated and used directly within a DSMC simulation of the gas-surface interaction.
|Original language||English (US)|
|Title of host publication||53rd AIAA Aerospace Sciences Meeting|
|Publisher||American Institute of Aeronautics and Astronautics Inc, AIAA|
|State||Published - 2015|
|Event||53rd AIAA Aerospace Sciences Meeting, 2015 - Kissimmee, United States|
Duration: Jan 5 2015 → Jan 9 2015
|Name||53rd AIAA Aerospace Sciences Meeting|
|Other||53rd AIAA Aerospace Sciences Meeting, 2015|
|Period||1/5/15 → 1/9/15|
Bibliographical noteFunding Information:
This work was sponsored by the Air Force Offce of Scientific Research (AFOSR) under MURI grant FA9550- 10-1-0563. The views and conclusions contained herein are those of the author and should not be interpreted as necessarily representing the oficial policies or endorsements, either expressed or implied, of the AFOSR or the U.S. Government. The authors would like to thank Prof. Erica Corral at Corral Laboratory in University of Arizona for providing the TPS sample. The reconstruction data and images were produced at the X-ray Computed Tomography Laboratory in the Department of Earth Sciences, University of Minnesota. This facility is funded by a UMN Infrastructure Investment Initiative grant. Vanessa J. Murray was supported by the Department of Defense (DoD) through the National Defense Science and Engineering Graduate Fellowship (NDSEG) Program.
© 2015 by Poovathingal S., Schwartzentruber T.E., Murray V., Minton T.K.