Pore distribution and permeability principles for carbon fiber reinforced silicon carbide matrix composites with three-dimensional needled preform during the transpiration cooling process

Transpiration cooling problem in carbon fiber reinforced silicon carbide matrix composites (C/SiC) was studied based on the context of cooling of jet engine hot-end components. Pore distributions of C/SiC with different fiber preforms were compared, and the C/SiC with three-dimensional needled preform (3DN C/SiC) was selected. The pore structure of 3DN C/SiC was analyzed and studied by X-ray computed tomography scanning (CT), and its porosity was obtained based on the Archimedes’ principle. Finally, based on the Darcy–Forchheimer model, the pressure drop–flow rate curve was obtained and the permeability of 3DN C/SiC was calculated. By considering the influence of inertia and viscous forces, the characteristics and mechanism of the porous media flow inside 3DN C/SiC were analyzed. The results showed that 3DN C/SiC could achieve a permeability of 3.37 × 10^–12 m² under a porosity of 47.61 %, which was close to that of commonly used metal porous media. 3DN C/SiC also demonstrated good flow characteristics as a porous medium. Considering its other advantages, such as high temperature resistance, light weight, and high specific strength, 3DN C/SiC has excellent potential and prospects in jet-engine thermal protection systems.