Session: 22-02 Fan Aerodynamic Excitation and Inlet Distortion 2

Paper Number: 129159

129159 - Parametric Study on the Duct Intake Reflection Coefficients for Fan Flutter Analyses 

The coupling between the acoustic reflections of the intake and the fan vibration characterizes the fan flutter of modern aero engines. Close to the intake cut-on/cut-off condition, the reflection of the intake is most significant and key to the appearance of the so-called flutter “bite.”

Conceptual, still quantitative, models to analyze this problem have been developed using the reflection coefficients of a zero-thickness duct. A methodology to obtain such coefficients based on the Wiener-Hopf technique was given by Rienstra (1984) as close expressions that involved the complex integration of different kernels. As a result, its usage is hindered since Rienstra provided just a few results as examples.

Moreover, the existing results are intended for noise analyses and, firstly, focus more on its application for exit than intake noise, and secondly, there is a lack of information about the phase of the reflected waves that is critical for aeroelastic acoustic applications but for most acoustic applications is irrelevant.

This work presents a thorough set of the modulus and phase of reflection coefficient data for a zero-thickness intake, including variations of the inlet Mach number, inner-to-outer radius ratio, and circumferential wavenumber as a function of the dimensionless frequency. The paper is closed with a physical explanation of the derived trends and the consequences of fan flutter.

Presenting Author: Jose Miguel Perez Universidad Politécnica de Madrid

Presenting Author Biography: Associated professor of Fluid Mechanics and Computational Fluid Mechanics at the School of Technical Aeronautical Engineering (Polytechnic University of Madrid). Expert in Computational Fluid Mechanics and linear stability analysis and control applied to fluid mechanics problems in aerodynamics.

Authors:

Jose Miguel Perez Universidad Politécnica de Madrid
Roque Corral Universidad Politecnica de Madrid