Effect of Porosity and Injection Ratio on the Performance of Transpiration Cooling through Gyroids

Abstract

This paper presents experimental measurements of adiabatic effectiveness for three transpiration cooling porosities (ϕ= 0.3, 0.4, and 0.5) constructed from gyroid lattice structures. To the authors’ knowledge, this is the first use of a Triply Periodic Minimal Surface (TPMS) function to produce transpiration test coupons of varying porosity. Polymer gyroid lattice structures were successfully printed using Stereolithography (SLA) down to ϕ= 0.3 for a print resolution of 25 microns and unit cell size of 2 mm. Cooling performance was measured in a small-scale wind tunnel. High-resolution Infrared Thermography was used to determine wall temperatures downstream of the porous section. When tested at both common blowing ratios (M = 0.029, 0.048, and 0.062) and common injection ratios (F = 0.010, 0.017, and 0.022) the cooling performance was found to be dependent on porosity for constant M but not for constant F. Having determined F as the more important parameter for comparison, results are presented alongside transpiration and effusion data from literature.

Keywords

• transpiration cooling
• periodic porous structures
• gyroids
• additive manufacturing
• injection ratio
• effective area