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Type of Document Dissertation Author Karim Kamel Ibrahim, John Author's Email Address kamel.john@gmail.com URN etd-09222007-022308 Title CHEMICAL VAPOR DEPOSITION/CHEMICAL VAPOR INFILTRATION OF PYROCARBON IN POROUS CARBON Degree Doctor of Philosophy Department Aerospace and Mechanical Engineering Advisory Committee
Advisor Name Title Paul McGinn Committee Chair Akshay Waghray Committee Member Alexander Mukasyan Committee Member Joseph Powers Committee Member Keywords
- low Mach number
- surface reaction mechanism
- reaction mechanism
- reactive flow
- porous media
- infiltration
- methane
- Chemical vapor deposition
Date of Defense 2007-08-03 Availability restricted Abstract A chemical vapor deposition/infiltration reactor used to manufacture carbon aircraft brakes has been simulated numerically. This simulation accounts for a homogeneous gas reaction mechanism as well as a heterogeneous surface reaction mechanism. Non-Boussinesq equations are used to predict fluid flow, heat transfer, and species concentrations inside the reactor and porous brakes. A time-splitting algorithm is used to overcome stiffness associated with the reactions. A commercial code is used to solve for the convection/diffusion step while an implicit time-integration algorithm is used to solve for the reaction step. Results showing the flow, temperature and concentration fields, as well as the deposition rate of carbon, are presented.
The direct solution of large scale coupled nonlinear differential algebraic equations (DAE) is extremely difficult if not impossible to obtain. Moreover, such solution is beyond the capability of present computers for unsteady and multidimensional problems that include, multi-species, gas phase as well as surface chemical
reactions, and surface to surface radiation. Therefore, we propose an integration procedure that employs the projection (fractional-step) method for the solution of the momentum equation.
This method is based on operator decomposition where the pressure is obtained by solving a Poisson equation followed by a projection or correction step for the velocity field so that it satisfies the conservation of mass equation. In addition we use a symmetric Strang operator-splitting algorithm to overcome stiffness that arises from chemical reactions.
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