Measurement of far field combustion noise from a turbofan engine using coherence functions

1977 4th Aeroacoustics Conference   unpublished
Coherence measurements between fluctuating pressure in the combustor of a YF-102 turbfan engine and far-field acoustic pressure 0 were made. The results indicated that a coherent relationship between 0 3 cr) Q, the combustor pressure and far-field existed only at frequencies below I W 250 Hz, with the peak cccurring near 125 Hz. The coherence functions and the far-field spectrs were used to compute the combustor-associated I far-field noise in terms of spectra, directivity, and acoustic power,
more » ... nd acoustic power, over a range of engine operating conditicms. The acoustic results s o i measured were compared with results obtained by conventional methods, as well 2s with various semiempirl.xt1 predictions schemes. Examination of the directivity patterns indicated a peak in the combustion noise near 120' (relative to the inlet axis). ii.211ts at progressively lower engine power settings. The data are then ?, .
doi:10.2514/6.1977-1277 fatcat:du4rwjsaune7bigelj2defpkfe