Effect of fan exit guide vane placement on fan broadband interaction noise

This paper explores the effect of fan exit guide vane (FEGV) placement on the aft-radiated interaction broadband noise created by the turbofan stage. The Source Diagnostic Test (SDT) rig-scale fan stage configurations are analyzed. Simulations are carried out using two low-order methods, one based on methods developed by Stewart Glegg and the other one based on methods developed by Ventres, allowing a comparison between their predictions. Additional effects, including the influence of vane sweep, inflow turbulence inhomogeneity and turbulence length scale estimation methods are investigated. The simulations presented here support previous findings that show, unlike the tonal noise, the broadband noise is only slightly affected by the FEGV placement. Both low-order models show that FEGV placement has a tilting effect on the broadband spectrum but they predict different trends in overall sound power level. The spectral tilting is mostly influenced by changes in the turbulence length scale while the overall change in the spectral level is associated with the changes in annulus area. Therefore, as the FEGV placement changes, the final spectrum depends on the magnitude of each influence. Still, the overall broadband noise level only varies within the range of 1 dB for all FEGV cases and placements considered.