CARE – Cavity Acoustics and Rossiter modEs

The main overall objective is systematically experimentally quantify the coupled resonance occurring due to interaction between vortex oscillations from the boundary layer / shear layer flow passing over a cavity and the acoustic cavity. This targeted to provide validation data for in-house acoustic codes at industry in order to strengthen design prediction capabilities.

Funded by:

Vinnova (through the NFFP7 program)

Time period:

20191010 – 20230630

20230701 – 20240831 (continuation as CARE-2)

20240901 – 20250531 (continuation as CARE-3)

Project partners:

GKN Aerospace Sweden

Background

Acoustic resonance in cavities in aero engines is a current and major concern due to the detrimental effect the unsteady loads have on the nearby components in the engine. An example is the bleed system resonance in the intermediate compressor duct that may cause failure to the low-pressure compressor. The basic acoustic phenomena of quarter pipe length or Helmholtz resonances may occur for any given cavity geometry and calculations of those are not straightforward for complex cavity geometries with several exits. So-called Rossiter’s resonance may occur due to an interaction between the radiating cavity acoustic resonance frequency and any dominant boundary layer vortex frequency from passing over the cavity that can lead to severe structural forces generating high vibration amplitudes, which in turn may lead to pre-lifetime failure of components.

Aim and objectives

Detailed objectives are:

Quantify resonance frequencies for three cavity configurations with increased geometrical complexity level.
Establish a validation database from experiments with key parameters and variables such as non-dimensional geometry parameters, free-stream velocity, turbulent boundary layer thickness, acoustic resonance frequency, pressure amplitude, vortex-shedding frequency etc.
Update the design of the trailing edge of the cavity opening. Experimentally analyse the impact of the previously measured acoustic vibration on the new design with focus of matching the eigenfrequency of the trailing edge design.