Hypersonic turbulent transpiration cooling including downstream effects.

Abstract

Turbulent lieat-transfer measurements were made on a transpiring flat plate model in a Mach 8 tunnel using nitrogen, helium, and argon as injection gases. The model consisted of an impermeable leading edge, a transpiration section, and a downstream section instrumented with asymptotic calorimeters. Tests were made at a. of 0°, —5° , and —10° and thus local freestream Mach numbers of 8.02, 6.88, and 5.77, respectively, with the leading edge and porous section at various surface temperatures. The reduction in the heat flux for the transpiring section was obtained at higher blowing rates and Mach numbers than previously reported, whereas the downstream heat flux results may be the first quantitative measurements of their kind. The reduction in the turbulent heat flux to the transpiring and downstream surfaces is found to be insensitive to Mach number, Reynolds number, and transpiration gas. Comparison of the reduction in heat flux with existing information is made and satisfactory agreement is obtained. The heat flux downstream of the transpiring surface is found to increase sharply immediately behind the porous region and then to remain essentially independent of distance for the remainder of the downstream section. A simple relation is derived for correlating the downstream results for laminar and turbulent flow with the upstream injection of air.