Experimental and Numerical Study on Effusion Cooling Configuration for the Swirl CMC Combustor Platform

Abstract

Abstract With advantageous thermal, strength, and weight properties at high temperatures, Ceramic Matrix Composite (CMC) is regarded as the potential structural material for modern aeroengines with the extreme increase of operating temperature. However, the anisotropic thermal conductivities caused by the weaving type call for a novel cooling structure design since it brings a completely different thermal conduction performance inside the hot components compared to the superalloy. The infrared thermographic experiment was carried out based on the SiC/SiC composite platform prepared by a 2-D plain weave braid structure with the CVI process with three staggered effusion hole configurations in this paper to explore the cooling characteristic of the CMC. The surface overall cooling effectiveness (ϕ) of the platform was measured under a temperature ratio of 1.5 (Tg/Tc = 1.5) and seven mass flow ratios. And a separate numerical simulation with different swirl effects was conducted as a supplement for the combustor operation condition. The results indicate that the thermal conductivity along the thickness direction is of great importance for the platform cooling. The overall cooling effectiveness of the CMC platform was smaller in comparison with the superalloy platform because of its smaller through-thickness thermal conductivity. Moreover, the concentrated coolant outflow is beneficial for the CMC cooling performance given that the area-averaged overall cooling effectiveness disparity of the two materials was narrowed with the smaller hole spacing. The swirling flow strongly inhibits the outflow of coolant near the swirling core but expands the lateral coverage of the film simultaneously. Such behavior alters the film cooling potential as well as the cooling pattern. The difference between CMC and superalloy was increased with the low swirl situation and decreased with the high swirl situation.