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Experimental Investigations on Highly Loaded Compressor Airfoils with Different Active Flow Control Parameters Under Unsteady Flow Conditions
Citation key 2018_brueck_gpps
Author Brück, C. and Mihalyovics, J. and Peitsch, D.
Pages GPPS-2018-0054
Year 2018
DOI 10.5281/zenodo.1343489
Location Montreal, Canada
Journal GPPS - Proceedings of Global Power and Propulsion Society Conference
Month 05
Note Technische Universität Berlin:
C. Brück, J. Mihalyovics, D. Peitsch
Editor GPPS
How Published Creative Commons Attribution 4.0 International License CC-BY 4.0
Abstract At the Institute of Aeronautics and Astronautics of the Technische Universiẗat Berlin, an annular cascade has been developed to investigate the behavior of three-dimensional flows in a compressor stator cascade under the influence of a certain pressure gain combustion process. The experimental investigations presented herein, discuss the impact of an unsteady outflow condition on the compressor stator flow being periodically throttling by means of a two bladed throttling device in the stator wake. This simulates the expected conditions for a Pulsed Detonation Engine (PDE). The unsteady flow conditions cause changes in the incidence angle at the leading edge of the compressor stator blades. As a major consequence, separation on the suction side and in the hub region occur, caused by a periodic event depending on the position of the throttling device. Active Flow Control (AFC) is implemented by means of pneumatic side wall actuation at the stator hub to affect the afore mentioned flow conditions. Various positions and blowing angles of the actuation slot with respect to different massflow rates are investigated to analyze the impact of the AFCon the suction sided corner vortex system. In addition to the steady blowing of compressed air, pulsed blowing at different frequencies and constant duty cycles is also evaluated with regard to the corrected total pressure loss coefficient. Further more, Strouhal number variations are realized by changing the frequency of the throttling device causing different flow characteristics on the stator blades and thus influencing the effectiveness of the AFC. Different actuator geometries and their varying impact on the AFC of the corner vortex system are analyzed using multicolored oil flow visualization. Unsteady conditions are investigated via phase-averaged pressure measurements in the wake and on the suction side (SS) of the stator blades to visualize the unsteady flow characteristics for one passage. Using a traversable stator blade, 24 positions for static pressure measurements from the leading to the trailing edge are used to visualize the complete pressure field on the SS from hub to tip with over 1800 pressure values. AFC has a varying impact on the throttling frequency and can improve the turning of the stator blades for different Strouhal numbers, as can be concluded from a rising static pressure. A change of the actuator position and blowing angle causes a change to the radial and axial dimension of the corner separation and secondary flow structures on the SS. Moreover, these characteristics differ with the mass flow used for the actuation. The investigations under pulsed blowing conditions show a clear tendency towards smaller frequencies to achieve a lower corrected total pressure loss coefficient.
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