Andreas K. Flock, Adrian T.E. Krieger, Ali Gülhan

DOI Number XXX-YYY-ZZZ

Conference Number HiSST-2022-150

In all sorts of Ramjet engines the intake serves as the major component to compress the flow to sufficiently large pressures. With its location being far upstream, its performance is crucial for all following
components such as combustor or nozzle. One major physical effect that influences intake performance
is intake starting and unstart. During intake unstart, the shock system within the diffuser quickly moves
upstream and mass flow and thus thrust are reduced. Therefore, a proper understanding of the unstart and then re-start behavior is essential for a correct operation of the engine. This manuscript
presents a numerical, quasi-steady approach to duplicate the starting and unstart characteristics with
a CFD approach. An axisymmetric intake configuration was used as reference configuration. In small
steps the free stream Mach number is decreased and then again increased while intake performance is
monitored. Furthermore, the starting and unstart characteristics were extracted from wind tunnel experiments. When comparing an initially unstarted, but then accelerated intake to an initially started, but
decelerated intake, a hysteresis effect was present: The intake unstart occurred at lower free stream
Mach numbers than the restart. This hysteresis effect was also detected during the wind tunnel experiments. Overall, the re-start and unstart Mach numbers, detected with the numerical approach were
within 7 % of the values detected during experiment.

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In Categories: 1.Events, HiSST 2022, Propulsion Systems and Components
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