Experimental Boundary Layer Investigation of a Stacked Transpiration Cooling Setup with Uniform Blowing Ratio

Abstract

Transpiration cooling is considered as an innovative cooling method meeting the demand for efficient cooling of future rocket engine combustion chambers. In this context an experimental baseline study with a stacked transpiration cooled setup of four aligned ceramic fiber reinforced carbon (C/C) samples is investigated in hot gas conditions of THG = 374.15 K and ReDh = 200.000 with a transpiring coolant blowing ratio of F = 0 - 4% of air. Hereby, the focus is on the investigation of the boundary layer situation based on the measurement of velocity and temperature profiles with a measurement rake comprising a pitot tube and a thermocouple. A determination of the friction coefficient cf as well as the Stanton number St is discussed and implemented for the no blowing and blowing cases. On the basis of two test cases with different transpiration lengths and starting points of uniform transpiration cooling a unifying illustration is aimed for the derived momentum and mass transfer parameters. Representations considering the momentum thickness Reynolds number Redelta2 and the enthalpy thickness Reynolds number Redeltah yielded good agreement.