Abstract
Thermal-gradient chemical vapor infiltration (TG-CVI) is an alternative process to the classical CVI by involving a temperature gradient to obtain uniform densification. It allows fabricating C/SiC and C/C composites starting from a fibrous preform and gasses precursor. The main interest of these processes is increasing the density homogeneity and the densification rate. In the proposed TG-CVI reactor, a heater with a constant temperature (1323 K) is placed in the core of the reactor and the cool gas flows from the outside to the center. Therefore, a continuous radially moving densification from inside to the outside of porous preform can be achieved. A numerical model was developed in order to investigate temperature distribution and velocity profile in the TG-CVI reactor. The commercial CFD software CFD-ACE+ was used. The obtained three-dimensional results were compared with experimental data. Three reference points were defined to measure the temperature in the preform. The computed results of TG-CVI showed a good agreement with the measured data. The simulation results of this study are important for the optimization of the densification process in the preform in The TG-CVI reactor.
Highlights
Chemical vapour infiltration (CVI) is considered as one of the main processes used to densify porous preform for carbon/carbon and carbon/silicon carbide composites [1, 2]
The densification rate is low, the consumed time to achieve the process is extremely high, and this process is energy-consuming. These drawbacks can be avoided by thermal-gradient CVI (TG-CVI) process [5]
This CVI reactor is used in the industrial fabrication of silicon carbide by introducing a mixture of methyltichlorosilane (MTS) and hydrogen to the reactor
Summary
Chemical vapour infiltration (CVI) is considered as one of the main processes used to densify porous preform for carbon/carbon and carbon/silicon carbide composites [1, 2]. The first implementation of CVI was carried out under isothermal conditions (I-CVI)[3] This type is the simplest type of CVI in which the preform is placed in a uniform temperature furnace. The densification rate is low, the consumed time to achieve the process is extremely high, and this process is energy-consuming. These drawbacks can be avoided by thermal-gradient CVI (TG-CVI) process [5]. A computational fluid dynamic (CFD) study has been carried out to simulate temperature distribution and velocity pattern in a 3 dimensional TGCVI reactor
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