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The present work aims at giving a comprehensive overview of the current development status of an intrusive probe, capable of collecting the condensed combustion products present in the exhaust of a solid rocket motors. The innovative technique was conceived in the EMAP (Experimental Modelling of Alumina Particulate in Solid Booster) framework, a project aiming at characterizing the alumina in terms of size, temperature and spatial distribution to gain detailed information for climatological impact assessment. A supersonic probe was sized to handle a progressive deceleration and cooling of the exhaust gas, as well as the quenching and collection of the suspended particles in a pressure-controlled chamber. The task was achieved by through a quasi 1D gas dynamics code based on the Shapiro method and the normal shock wave theory, which was verified against a hybrid 2D axial-symmetric mesh whose turbulent flow field was solved using the DLR-TAU CFD code. The robustness of the system has been investigated performing a sensitivity and an uncertainty analysis, exploring uncertainties propagation through the numerical code based on Shapiro equations. The sensitivity analysis enabled to define a ranking of importance for the uncertainties on the probe behavior; the uncertainty analysis allowed to estimate failures of the system and/or of the code. Cold flow tests carried out at the vertical facility of DLR-Cologne enabled to gain a proof of concept for both fluid dynamic behavior and collection methodology.

A numerical study of mixing and combustion enhancement has been performed for a Mach 2 model scramjet (supersonic combustion ramjet) combustor. Fuel (hydrogen) is injected at supersonic speed through the rear of a lobed strut located at the channel symmetry axis. The shape of the strut is chosen in a way to produce strong streamwise vorticity and thus to enhance the hydrogen/air mixing. Strength and size of the vortices are defined by the strut geometry and may be modified. It will be shown that in comparison to planar struts the mixing efficiency is strongly improved. On the other hand, the induced vortices cause an increase in entropy and larger losses in total pressure. Different planar and lobed strut injectors are investigated numerically and a comparison with experimental data is given for cold supersonic mixing. Based on this study a numerical investigation of flame stabilization and fuel burnout is performed where two stable modes of combustion are identified. They are associated with attached or detached flames depending on the chosen inflow conditions. In both cases subsonic regions at the channel symmetry axis are responsible for flame holding. If the combustor geometry is chosen in a favorable way these subsonic zones may be kept small. Moreover, the flames are away from solid walls thus minimizing the wall heat load.

The objective of the presented work is to investigate the slipstream effects on the flow properties and thrust performances of a full-length and truncated annular plug nozzle of a small rocket launcher during a suborbital flight. The nozzle flow properties are investigated for three characteristics flow conditions (M∞ = 1.3, 2.59 and 9.7), using CFD simulations. When the rocket launcher flies through the atmosphere, the body geometry produces a slipstream with conditions in the nozzle area that are different from the undisturbed environment. The in-flight behavior of the truncated plug nozzles is complicated and affected also by recirculation regions that take place behind the shroud and plug base. In this paper special emphasis is given to investigate the slipstream effects between the hot exhaust plume from the rocket engine and the external coaxial supersonic/hypersonic air flow and their influence on the slope and position of different shocks generated in the separated flow region (realignment shocks, recompression shocks, plug base lip shock and trailing shocks). Also analyzed is the pressure distribution on the shroud base, spike supersonic ramp and spike base for closed-wake operations to determine the overall engine performance. The results of the numerical simulations confirm the altitude-compensating features of the annular truncated plug nozzles.