Influence of the braided structure on the film cooling performance over the ceramic matrix composite plate

The influence of the braided structure on the film cooling performance over a ceramic matrix composite plate was numerically and experimentally investigated. The model based on the effective thermal conductivity and the model based on the internal micro braided structures were both built to demonstrate the effects of the braided structure on the cooling performance. Firstly, the experiment of the film cooling efficiency on the braided plate was carried out, to validate the numerical method, which presented good accuracy. Then, the temperature and cooling efficiency distributions were compared between the results based on these two models. Additionally, the braided angle of the internal structure and the relative position between the holes and the braided yarns were changed to investigate their influence on the cooling efficiency and the internal temperature filed. The results show that, the internal braided structure has obvious influence on the cooling effect and the heat conduction inside the composite plate, leading to the non-uniform variation of the cooling efficiency and the temperature. The relative variation between the average cooling efficiencies based on these two models reaches 10.4%. Additionally, the relative position between the film hole and the braided yarns would affect the phase of the cooling efficiency's non-uniform variation. The relative variation among the maximum cooling efficiencies with different relative positions could reach 10.73%, and the cooling performance is best when the hole is located on the horizontal braid yarns. The braided angle would affect the periodic length of the temperature's non-uniform variation inside the plate. The cooling performance is better with smaller braided angle, but the influence is not significant.