15th European Conference on Turbomachinery Fluid dynamics & Thermodynamics

Paper ID:

ETC2023-129

Main Topic:

Diffusers

https://doi.org/10.29008/ETC2023-129

Authors

Andreas Grois  - University of the Bundeswehr Munich, Germany
Marcel Stößel - University of the Bundeswehr Munich, Germany
Dragan Kozulovic - University of the Bundeswehr Munich, Germany
Reinhard Niehuis - University of the Bundeswehr Munich, Germany
Michael Krummenauer - Bundeswehr Technical Centre for Aircraft and Aeronautical Equipment in Manching, Germany

Abstract

The Institute of Jet Propulsion (IJP), in cooperation with the Bundeswehr Technical Centre for Aircraft and Aeronautical Equipment in Manching, developed the highly bent, compact intake system MEIRD (Military Engine Intake Research Duct) for academic and research purposes on integration aspects with innovative propulsion systems. Modern aircraft, such as military UAVs or high-performance fighter aircraft, require very low observability. Therefore, part of the propulsion system's contribution is to prevent radar reflections from the easily detectable fan. This is often achieved by using double s-shaped intake designs, which, however, cause strong flow distortions and thus are particularly in focus of detailed investigations on its effects on engine operating stability and performance. Previous studies at the IJP were limited to ground-level cases of the engine intake and its interaction phenomena with the downstream low-pressure compressor. Setting up an ambient-condition-independent test environment enables the investigation of the intake system under more realistic flight conditions. In combination with detailed numerical flow simulations, such a test setup allows for validated investigations on the influence of the inflow conditions on the distortion schemes and intensities inside the MEIRD. Therefore, the proposed paper deals with the detailed analysis of the data derived from numerical studies, which were validated against experimental data acquired using the new test setup. Analytical calculations were conducted to identify relevant parameters of the flight conditions to be used as boundary conditions for both the experimental and the numerical setup. Then, a process chain was designed to transfer the aircraft's flight conditions to the intake operating points to determine proper Mach and Reynolds number combinations. A scaled-down intake model (MediMEIRD - Medium scaled Military Engine Intake Research Duct) was developed to match the performance map of the available wind tunnel setup and the derived envelope conditions in the best possible way. Presently, the Mach- and Reynolds number range of the investigations could be varied to represent the aircraft envelope between 0 km and 14 km and flight velocities up to Ma=0.525. The flow solver TRACE developed by DLR was used for the steady state RANS simulations. Since the experimental MediMEIRD setup is equipped with a large number of static pressure taps, the CFD results are particularly validated and analyzed in detail at those cross sections equipped with pressure taps. The placement of the sections was carried out to identify and locate the most relevant aerodynamic phenomena. Furthermore, determining the resulting forces by integrating these surface pressures enables the classification of local flow distortions in the intake. The study reveals that Mach and Reynolds number variations based on different flight conditions significantly affect the flow in the intake, whereas influences of Mach number dominate. High Mach numbers increase the flow distortions. It turned out that the Reynolds number has a minor influence. In addition, the distribution of the flow distortion based on the resulting forces allows the entire intake to be considered. Finally, the CFD simulations and test bench provide a flexible environment for investigating complex flow distortion phenomena due to different intake operating conditions.



ETC2023-129




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