Core noise source diagnostics on a turbofan engine using correlation and coherence techniquesFluctuating pressure measurements at several locations within the core of a turbofan engine were made simultaneously with far-field acoustic measurements. Correlation and coherence techniques were used to determine the relative amplitude and phase relationships between core pressures at these various locations and between the core pressures and far-field acoustic pressure. The results indicate that the combustor is a low-frequency source region for acoustic propagation through the core nozzle and out to the far-field. Specifically, it was found that the relation between source pressure and the resulting sound pressure involves a 180 deg phase shift and an amplitude transfer function which varies approximately as frequency squared. This is shown to be consistent with a simplified model using fluctuating entropy as a source term.
Document ID
19770061605
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Karchmer, A. (NASA Lewis Research Center Cleveland, OH, United States)
Reshotko, M. (NASA Lewis Research Center Cleveland, Ohio, United States)
Date Acquired
August 9, 2013
Publication Date
November 1, 1976
Subject Category
Aircraft Propulsion And Power
Meeting Information
Meeting: Meeting of the Acoustical Society of America