Duct Mode Measurements on the TFE731-60 Full Scale Engine

Abstract A continuously rotating rake with radial microphones was developed to measure the inlet and exhaust duct modes on a TFE731-60 turbofan engine. This was the first time the rotating rake technology was used on a production engine. The modal signature for the first three fan harmonics was obtained in the inlet and exhaust. Rotor-stator and rotor-strut interaction modes were measured. Total harmonic power was calculated over a range of fan speeds. Above sonic tip speed, the rotor locked mode was not strong enough to be identified, but the “buzz-saw” noise at fan sub-harmonics was identified. Introduction The Advanced Subsonic Technology (AST) program sponsored the Engine Validation of Noise Reduction Concepts (EVNRC). A full-scale turbofan engine, the TFE731-60 was used as a test bed for part of this program. A continuously rotating rake with radially distributed microphones was developed for use on the Honeywell TFE731-60 as an acoustic diagnostic tool. Rotating rake technology had been developed and used successfully on model scale