An Experimental Parametric Study of Geometric, Reynolds Number, and Ratio of Specific Heats Effects in Three-Dimensional Sidewall Compression Scramjet Inlets at Mach 6
Since mission profiles for airbreathing hypersonic vehicles such as the National Aero-Space Plane include single-stage-to-orbit requirements, real gas effects may become important with respect to engine performance. The effects of the decrease in the ratio of specific heats have been investigated in generic three-dimensional sidewall compression scramjet inlets with leading-edge sweep angles of 30 and 70 degrees. The effects of a decrease in ratio of specific heats were seen by comparing data from two facilities in two test gases: in the Langley Mach 6 CF4 Tunnel in tetrafluoromethane (where gamma=1.22) and in the Langley 15-Inch Mach 6 Air Tunnel in perfect gas air (where gamma=1.4). In addition to the simulated real gas effects, the parametric effects of cowl position, contraction ratio, leading-edge sweep, and Reynolds number were investigated in the 15-Inch Mach 6 Air Tunnel. The models were instrumented with a total of 45 static pressure orifices distributed on the sidewalls and baseplate. Surface streamline patterns were examined via oil flow, and schlieren videos were made of the external flow field. The results of these tests have significant implications to ground based testing of inlets in facilities which do not operate at flight enthalpies.
Auslegung und Charakterisierung eines dreidimensionalen Scramjet-Einlaufs mit hohem Verdichtungsverhältnis und variabler Innenkontraktion
Schwerpunkt der Arbeit lag in der Uberfuhrung vormals zweidimensionaler Einlaufgeometrien in eine dreidimensionale Konfiguration. Dazu wurden Voruntersuchungen mit einem modifizierten 2D-Einlauf durchgefuhrt, auf deren Basis der neue 3D-Einlauf mittels einer CFD-Parameterstudie entwickelt wurde. Um das Starten des Einlaufs sicherzustellen wurde eine verfahrbare Haube zur Variation der Innenkontraktion integriert. Das Betriebsverhalten des 3D-Einlaufs wurde im Wind-kanal H2K analysiert. Dies umfasste das Startverhalten und die Variation des Brennkammer-gegendrucks, der Reynoldszahl und von Anstell- und Schiebewinkel. Zur Analyse der Stromung kamen zahlreiche Messverfahren zum Einsatz. Neben Schlierenaufnahmen und Wanddruckverlaufen wurden die Profile des Pitot- und statischen Drucks im Isolator mittels eines Druckmessrechens aufgezeichnet und daraus Machzahlprofile sowie Verdichtungs- und Totaldruckverhaltnisse abgeleitet. Die Massenstrome an den jeweiligen Betriebspunkten wurden mit einer Drossel gemessen. Zudem wurde auf den externen Rampen die Warmestromdichte aus Infrarotthermografiemessungen bestimmt. 
 
The work focused on converting former two-dimensional inlet geometries into three-dimensional configurations. In order to do so preliminary investigations using a modified 2D-inlet were conducted. Based on this, a new 3D-inlet was designed by a parametric CFD study. To ensure inlet starting a movable cowl for the variation of internal contraction was integrated. The operational behavior of the 3D-inlet was analyzed in the windtunnel H2K. This covered the starting behavior and the variation of combustion chamber backpressure, Reynolds number and angle of attack and angle of yaw. For the investigation of the flow, numerous measurement techniques were applied. Besides Schlieren images and wall pressure curves, the profiles of Pitot and static pressure in the isolator were recorded by a pressure measurement rake, from which Mach number profiles as well as compression and total pressure ratios were derived. The mass flow at each point was measured by a throttle. Furthermore, wall heat fluxes on the external ramps were determined from infrared thermography.
Three-dimensional inviscid analysis of the scramjet inlet flow field
A computer code has been developed to analyze the inviscid flow field in a supersonic combustion ramjet (scramjet) inlet. The code uses the three-dimensional Euler equations in full conservation form to describe the inlet flow. An algebraic numerical coordinate transformation is used to generate a set of boundary-fitted curvilinear coordinates. The governing equations are solved by a time-asymptotic, unsplit, two-step, finite-difference method. This method is highly efficient on the vector processing computers for which the current code is written. Detailed results are presented for two scramjet inlet configurations over a range of Mach numbers. The calculated results are compared with the available experimental and theoretical results.