Unsteady flow phenomena in a highly bend engine intake with passive and active flow control

Abstract

Highly bent intake systems cause unsteady flow phenomena which have a negative impact on the performance of the compressor system. In the present study, a serpentine intake is investigated experimentally with and without flow-stabilizing measures. The timeaveraged measurement results show that the flow-stabilizing measures strongly reduce the separation bubble and the flow distortion in the intake. Unsteady pressure measurements indicate accordingly that dominant Strouhal numbers, associated with the Dean vortices, are weaker or not present at all in case of flow control. These unsteady phenomena are further analyzed in terms of their respective Strouhal numbers versus the power spectral density and compared to the configuration without any flow-stabilizing measures. The results demonstrate that without flow stabilizing measures, two dominant peaks occur at Strouhal numbers 0.32 ≤ Sr ≤ 0.39 and 0.18 ≤ Sr ≤ 0.24. Thereby, with increasing Reynolds numbers, the dominant Strouhal numbers decrease slightly. KEYWORDShighly bend engine intake, unsteady flow phenomena, active and passive flow control NOMENCLATURE γ relative radius of curvature r k radius of curvature r in radius at the inlet cross section Sr Strouhal number DIP duct inlet plane DOP duct outlet plane IJP Institute of Jet Propulsion ET F engine test facility M EIRD military engine intake research duct p rel relative static pressure p ∞ ambient pressure x, y, z Cartesian coordinates d Duct outlet diameter L total MEIRD lenght x rel , y rel relative cartesian coordinates P SD power spectral density v velocity f frequency s Position at the centerline, percentage wise n spool speed