Experimental Investigation of Supersonic Combustion in the HIEST and HEG Free Piston Driven Shock Tunnels

Ground based testing of a supersonic combustion ramjet (scramjet) configuration used in the framework of the HyShot IV flight were carried out in the High Enthalpy Shock Tunnel (HIEST) of the Japan Aerospace Exploration Agency (JAXA) Kakuda Space Center and the High Enthalpy Shock Tunnel Göttingen (HEG) of the German Aerospace Center (DLR). The objective of these investigations was to study the same hydrogen fuelled scramjet configuration in both large scale free piston driven shock tunnels and to compare the combustor performance. The full scale wind tunnel models consisted of an intake, a combustor and exhaust surfaces. The utilised test conditions aimed at duplicating Mach 7.5 flight conditions in the altitude range of 28 – 30 km. Gaseous hydrogen was injected into the combustion chamber by a wall mounted hypermixer injector developed by JAXA. The characteristics of the combustion process, in particular the change from steady supersonic combustion to a transient combustor flow, was investigated in both facilities by varying the fuel equivalence ratio. Time resolved surface pressure measurements in the combustor and on the exhaust surfaces as well as high speed flow visualisation was performed