Benefits of Swept-and-Leaned Stators for Fan Noise Reduction

An advanced high bypass ratio fan model was tested in the NASA John H. Glenn Research Center 9 £ 15 Foot Low-Speed Wind Tunnel. The primary focus of this test was to quantify the acoustic benee ts and aerodynamic performance of sweep and lean in stator vanedesign. Three statorsets wereused forthis testseries. Aconventional radial stator set was tested at two rotor ‐stator axial spacings. Additional stator sets incorporating sweep only and sweep and lean were also tested. The hub axial location for the swept-and-leaned and swept-only stators was at the sameaxiallocationastheradialstatoratthesmallerrotor ‐statorspacing (upstreamstatorlocation ),whilethetipof thesemodie edstatorswasatthesameaxiallocation astheradialstatorsetatthedownstream rotor ‐statorspacing. The acoustic data show that swept and leaned stators give signie cant reductions in both rotor ‐stator interaction noise and broadband noise beyond what could be achieved through increased axial spacing of the conventional, radial stator. Application of these test results to a representative two-engine aircraft and e ight path suggest that about a 3 effective perceived noise (EPN)dB fan noise reduction could be achieved through incorporation of these modie ed stators. This reduction would represent a signie cant portion of the6-EPNdB aircraftnoisereduction goal relative to that of 1992 technology levels of the current NASA Advanced Subsonic Technology initiative.