Experimentelle Untersuchung der Innenverdichtung eines Hyperschalltriebwerkeinlaufs mit Überschalldurchströmung (English shop)

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The subject of this research project is the experimental investigation of the internal compression of ramjet engines with supersonic combustion (scramjet). The focus lies on the isolator, which is located between the inlet and the combustion chamber. The task of the isolator is to decelerate the flow entering the engine to moderate supersonic Mach numbers with a concomitant increase in pressure. Furthermore, the isolator must prevent the propagation of the pressure fluctuations emanating from the combustion process (isolation). The particular feature of the present tests is that the isolator is subjected to an asymmetric incoming flow, as prescribed by a real engine inlet. In order to obtain a database for the design of isolators, various models were tested at simulated flight Mach numbers of M=3.3 and M=4. In addition to conventional pressure and temperature measurement techniques, a colour schlieren optical system was available for the investigations, by means of which the pressure gradients inside the engine model could be visualised. Special attention is paid to the operational safety of the engine flow, which is dominated by “shock trains” and shock waves. With the aid of the optical method employed, the resulting shock configurations and shock–boundary layer interactions can be visualised very well. A comparison of the experimental data with numerical calculations carried out in parallel permits further conclusions about the observed flow phenomena.

Abstract:
The main topic of the research project is the experimental investigation of the inner compression of ramjet inlets with supersonic combustion (scramjet). The work focuses on the isolator section, located between the Inlet and the combustion chamber. The main Task of the isolator is he deceleration of the incoming air to moderate supersonic mach numbers and thus an increase of pressure. Furthermore the isolator has to protect the inlet against the pressure fluctuations released by the combustion process. In the particular measurements the Isolator was charged with an asymmetric flow, as it will be given by an Scramjet-inlet. To achieve a database for the design of Isolator sections different geometries are tested at simulated flight mach numbers of M=3,3 and M=4. The investigations were done by use of conventional pressure and temperature measurements as well as a colour-schlieren-optic, allowing the visualisation of pressure gradients within the tested model. Special attentions were given to the stable operation of the shock and shock-train dominated flow. Using the optical system the shock systems and the shock boundary interaction could be visualised very well. A comparison between the experimental data and numerical calculations done in parallel leads to additional Information about the observed flow phenomena.

Keywords: supersonic; engine, isolator, internal compression; fluid dynamics; aerospace.