Heat Transfer Measurements of a Transpiration-Cooled Stagnation Point in Transient Hypersonic Flow

Abstract

This paper presents a novel experimental technique where infrared thermography is employed to directly measure the surface heat transfer of a transpiration-cooled porous material in transient hypersonic flow. Experiments were conducted in the Oxford High Density Tunnel on a flat-faced hemispherical probe at a single Mach 7 freestream condition () with nitrogen, air, argon, krypton, and helium injection gases and mass flow rates ranging from 0.01 to . Surface heat transfer measurements were extracted by imaging directly on the porous material using a FLIR A6751 high-speed long-wave infrared camera. Porous alumina was chosen due to its favorable thermal properties for infrared analysis and its very small pore sizes () enabling a uniform outflow. It was found that the surface Stanton number reduction matched to within 10% of both computational fluid dynamics results and correlations.