Design Selection and Analysis of a Swept and Leaned Stator Concept

Abstract

AcknowledgmeJItsThe authors wish to thank Mr. Richard E Woodward and Dr. James E. Bridges, both of the Acoustics Branch at NASA Lewis Research Center, for providing the acoustic data shown in this report and the routines used for computing the 1-foot lossless acoustic power from the measured spectra.

Main Fan Noise Mitigation Technologies in Turbofan Engines

“…The three most common types of interaction are rotor blade chopping through the wakes of upstream stators, wakes from rotor blades impinging on downstream stators, and the pressure fields of the rotors reflecting nearby objects. The most important interaction type is generated as a result of periodic impingement of fan wakes on the outlet guide vanes (OGV) (Envia, Nallasamy 1998). The periodic cutting of rotor wakes causes rotor-stator interaction noise by the stator vanes.…”

“…When chosen properly, sweep and/or lean reduce rotor-stator interaction tone noise. To reduce noise, sweep and lean must be chosen in such a way so as to increase wake intersections per vane (Envia, Nallasamy 1998). Since the early 70s, several theoretical and experimental studies have hinted at the potential of sweep and lean for reducing rotor-stator tone noise (Rao 1972;Kazin 1973;Adamczyk 1974;Hayden et al 1977;Schultenm 1982;Envia, Kerschen 1984, 1990.…”

Highlights of Aeroacoustics Research in the U.S.—1998

“…Clearly, when sweep and lean are chosen properly, significant variation in the phase of unsteady pressure occurs compared with the radial stator. For a more detailed discussion see Envia and Nallasamy (1998).…”

Passive Techniques for Fan Noise Reduction in New Turbofan Engines: Review

“…The three most common types of interaction are rotor blades chopping through the wakes of upstream stators, wakes from rotor blades impinging on downstream stators, and the pressure fields of the rotors reflecting nearby objects. The most important one is generated as a result of periodic impingement of fan wakes on the outlet guide vanes (OGV) [5].…”

“…When chosen properly, sweep and/or lean reduce rotor-stator interaction tone noise. To reduce noise, sweep and lean must be chosen in such a way so as to increase wake intersections per vane [5]. Since the early '70s, several theoretical and experimental studies have hinted at the potential of sweep and lean for reducing rotorstator tone noise [8][9][10][11][12][13][14][15].…”