Experimental and Numerical Analysis of the small Scale LAPCAT II Scramjet Flow Path in High Enthalpy Shock Tunnel Conditions

Abstract

Dedicated experimental investigations of the different components of combined cycle propulsion systems are necessary for the understanding of the physical and chemical processes in both on and off-design conditions and the optimization of each individual component. The focus of the present study is put on the supersonic combustion ramjet. For this type of engine the design objective is a combustor with efficient mixing and combustion within the shortest possible length, but still robust enough to operate in various operational conditions. In the framework of the EU co-funded project LAPCAT II, a M=7.4 supersonic combustion ramjet (scramjet) powered small scale flight experiment (SSFE) configuration was designed. Since free jet testing of the complete combustion flow path (intake, combustor and nozzle) is a mandatory step within the design roadmap of future engines, ground based testing of the SSFE engine was conducted in the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR). This type of facility allows duplication of flight conditions in excess of M=8. Here tests were performed simulating Mach 7.4 flight conditions in approximately 28 km altitude. The numerically predicted thrust of the engine could be confirmed in HEG utilizing optical tracking of the free flight wind tunnel model. Combining these experimental results with computed aerodynamic data of the complete SSFE showed that for a selected flight condition a positive aero propulsive balance of the complete configuration could be achieved.