Enhancing spatial thermal uniformity in effusion cooling through gradient-porosity triply periodic minimal surface (TPMS) lattice arrays

Compared to traditional film cooling, effusion cooling provides stronger internal convection and better external film attachment. However, the poor mechanical properties of conventional cylindrical hole arrays limit their widespread application. Triply periodic minimal surface (TPMS) lattices exhibit isotropic mechanical properties without stress concentrations, making them highly suitable for advanced effusion cooling designs. In this study, steady-state infrared thermography was employed to evaluate the thermal performance of uniform and gradient-porosity TPMS topologies (Diamond, Gyroid, and Koch) while numerical simulations revealed the underlying mechanisms. Results indicate that the Diamond lattice maintains a low pressure loss alongside high cooling effectiveness, while the Koch lattice yields the highest overall cooling effectiveness. To address upstream lattice “coolant starvation” and hot gas ingestion caused by mainstream backpressure, a gradient porosity design was introduced. This design significantly improves spatial uniformity: the uniformity index increased by up to 12.7%, the standard deviation decreased by up to 61.4%, and the area-averaged overall cooling effectiveness improved by a maximum of 6.1% compared to the uniform baselines. At a low injection ratio, the uniform configurations channel nearly 50% of the coolant through the trailing row. In contrast, the gradient lattice increases the central coolant mass flow ratio by up to 154.4%. Flow analysis demonstrates that the gradient design shifts the high wall-normal velocity region upstream to resist mainstream ingestion, thereby reducing the scale of downstream counter-rotating vortex pairs to sustain a well-attached protective film. Finally, empirical correlations were developed to provide valuable design guidelines for advanced turbine cooling systems.