Fourier Descriptors for Improved Analysis of Distortion Transfer and Generation

Abstract

For fan/compressor design, quantifying distortion transfer and generation bladerow by bladerow through a fan/compressor is important to understand the flow physics and predict performance. What is needed are descriptors capable of describing distortion profiles with both high and low distortion content and account for the reshaping of distortion profiles. Four key parameters were identified as desirable to quantitatively capture distortion transfer, generation and effects on performance: distortion magnitude, shape, severity and phase. A set of distortion descriptors based on Fourier analysis are shown to quantitatively capture distortion magnitude, shape and phase change across bladerows. These Fourier descriptors are modal amplitude, total amplitude, and phase shift. When used together, these Fourier descriptors can be used to qualitatively describe any conceivable profile shape for any parameter.