Numerische Untersuchung des Forced Response Verhaltens eines Verdichters in Abhängigkeit der Einlaufgestaltung

Abstract

Modern military aircraft are subject to demanding operational requirements. A key aspect of stealth technology is the shielding of engine components from radar detection, achieved through bend intake ducts. These intake geometries distort the incoming airflow, potentially degrading engine performance and introducing an external aerodynamic excitation. The disturbed inflow can lead to an increase in mechanical stress on the compressor blades, making aeroelastic analysis essential for ensuring engine longevity. This thesis presents a numerical forced response analysis of a military compressor subjected to distorted inflow conditions. Three differently shaped intake geometries are investigated with respect to their forced responses. A modal approach is applied, enabling the evaluation of both resonant and off-resonant conditions. It is shown that the frequency ratio, representing the proximity between excitation frequency and natural frequency, is the dominant factor influencing the forced response. As a result, intake geometry and its aerodynamics must be optimized taking into consideration the modal characteristics of the compressor blades. Also shock motion as the primary excitation mechanism is identified. A Fourier decomposition of the inlet distortion demonstrates that its variations in total pressure amplitude directly translate into corresponding unsteady pressure fields in their respective engine order. Finally, several opportunities for future work are identified.