Numerical investigation of flow distribution and transpiration cooling performance in heterogeneous porous media with reacting coolant

The micro structure of porous media has significant impact on transpiration cooling performance. In this study, the flow distribution and transpiration cooling performance are investigated in heterogeneous porous media. A local thermal non-equilibrium model coupling with cracking reaction model of the coolant is developed. Compared with the non-reacting flow, the cooling efficiency increases significantly for the reacting flow while the flow distribution becomes more non-uniform. With the porosity increasing from 0.2 to 0.5, the average cooling efficiency decreases by 7.5% while the standard deviation of cooling efficiency increases by 119.3%. It is found that porosity has the most significant impact on transpiration cooling performance for low to medium blowing ratios. For blowing ratio at 0.3%, the average cooling efficiency increases by 10.3% while the standard deviation increases by 249.8% with porosity increasing from 0.2 to 0.5. In order to further improve the transpiration cooling performance, 6 sets of heterogeneous porous structures with spatially varying porosity functions are analyzed. Different from the homogeneous porous media, the heterogeneous porous media render better flow distribution and cooling performance. Compared with the homogeneous porous media, the average cooling efficiency remains above 60% for all the heterogeneous porous media while the standard deviation of the cooling efficiency is reduced from 13.1% to 1.7% for the optimized porous structure. The results indicate the spatially periodic porous structure is promising in rendering better overall transpiration cooling performance. This work provides novel insight into flow distribution and transpiration cooling mechanism in heterogeneous porous media using reacting coolant.