Forced Response Analyses of a 3.5 Stage Axial Flow Compressor

Background

Jet engine blade design contains three main aeromechanic challenges: forced response, flutter, and non-synchronous vibration. Forced response occurs when an excitation frequency coincides with one of the natural frequencies of the blades. Currently, preliminary design methods rely on empirical engine data to determine the acceptable frequency margin to safely operate the engine. During the last decades, computational fluid dynamics (CFD) has become an accurate tool to predict these aeromechanics phenomena. However, the use of unsteady CFD analyses for blade design requires validation with high-quality experimental data. 

Three-blade passage with surface mesh

About this Project

In this work, a frequency domain, harmonic balance CFD code is used to analyze a 3.5 stage axial compressor. Forced response analyses are carried out on the embedded rotors at different crossings on the Campbell diagram. The goal is to analyze the effect of neighboring rows on the response amplitude of the embedded rotors. Also, an extensive mistuning analysis is conducted to determine the sensitivity of the mistuned system to frequency perturbations, aerodynamic asymmetries, and excitation force perturbation.

 

To validate our results, the accuracy of the predictions is assessed against experimental data from a high-speed, rotating compressor rig located at Purdue University.

 

Example of flow around the stator blades

 

Group Members Involved