Influence of porosity and pore size on the heat transfer characteristics of ceramic matrix composites plate

Ceramic matrix composites (CMCs) are key candidate materials for aero-engine hot-section components due to the excellent thermo-mechanical properties. However, multi-scale porosity defects inevitably introduced during the preparation and processing impose significant uncertainties on the components' heat transfer characteristics. In this work, micro-scale and meso-scale representative volume elements (RVEs) were established. Numerical simulations were conducted to investigate the steady-state thermal conduction behavior under different porosity levels and pore sizes. The influence of porosity discrepancies induced by CVI and MI processes on the cooling efficiency of CMC turbine leading edges was further analyzed based on numerical results. The numerical results show that increasing porosity significantly reduces the equivalent thermal conductivity. At the micro-scale, the transverse thermal conductivity of micro-RVEs without fibers and with fibers decreases by approximately 7.07% and 7.77% at 5% porosity, respectively, compared with the pore-free condition. At the meso-scale, the equivalent thermal conductivity is reduced by 14.21% as porosity increases from 10% to 18%. Pore size has a limited effect on the equivalent thermal conductivity, but large pores increase the non-uniformity of temperature distribution, and large temperature gradients arise near pores close to fibers or yarns. This study clarifies the critical role of manufacturing-induced pores in CMC heat transfer, providing a basis for establishing manufacturing requirements to enhance the thermal reliability of aero-engine hot-section components.