Wall Pressure Effects and Shock-Boundary Layer Interactions in a Transpiration Cooled Scramjet Model Combustor

Abstract

This publication presents results of the ongoing investigation of transpiration cooling of scramjets conducted at the German Aerospace Center (DLR). It summarizes the results on the influence of the shock-boundary layer interaction on the static wall pressure distribution downstream of the transpiration cooling system obtained in more than 1000 hot run tests. Special focus is placed on the local static pressure distribution in the coolant wake region on the combustion chamber’s upper wall. Furthermore, different flow interaction phenomena were discovered and are thoroughly analyzed by the application of state of the art optical and intrusive measurement techniques like Background Oriented Schlieren (BOS) combined with pressure data analysis and correlation. The unique SBLI behavior of two coolants (hydrogen and nitrogen) and their influence on the static wall pressure distribution gets addressed in this publication. Three different porous wall materials are compared and analyzed in terms of performance, sensitivity to shock- boundary layer interaction issues and their influence on the wall pressure in the coolant wake region. An outlook is presented on the results of additional experiments using different types of porous media (e.g. ceramics) and improved measurement techniques with the same coolants. Further research requirements and subsequent changes in the test setup are discussed.