Acoustic testing of very high bypass ratio turbofans using turbine powered scale models

Abstract

The design, development, and testing of a twelve (12) inch fan diameter turbine powered simulator and its application to the study of acoustics of future aircraft engines is presented. Specifically, the sound generation mechanism within very high bypass engines are discussed and the scale model hardware necessary to simulate these mechanism are described in detail. A model fan performance map and acoustic results from testing in the NASA Langley 14 x 22Foot Wind Tunnel are presented. The objective of the investigation is to understand the physics of the noise generation and propagation in the very high bypass engine and to use this understanding to design a noise control system.

Inlet shape effects on the far-field sound of a model fan

“…The fan pressure ratio is 1.27 at 100% speed. 5 There are 40 fan exit stator vanes in the normal model configuration. This fan model allows for interchangeable stator vane sets and a set of 20 vanes was tested.…”

Azimuthal patterns of the radiated sound field from a turbofan model

“…Clearly these modes are caused by the interaction of the wakes from the ribs with the rotor bades. (6) The term in front of the square brackets is a constant complex number. The function inside the source brackets is a periodic ruction of 0' with circumferential periodicity 2jt/V.…”

Artificial noise systems for parametric studies of turbo-machinery aero-acoustics

“…Traditional methodologies for studying turbo-machinery aero-acoustics in order of decreasing complexity/technology readiness level (TRL) are as follows: static engine testing, 2 mid-TRL, 3,4 and low-TRL 5 scale model testing. These paradigms use rotor-stator combinations to generate and study Tyler-Sofrin 6 -type interactions and duct propagation.…”