Project is sponsored by the Austrian Research Agency FFG  

Bionic Surface Technologies GmbH

Project Coordinator: Institute for Thermal Turbomachinery and Machine Dynamics

Project Applicants / Contact: Dip.-Ing. Dr.techn. Andreas Marn (Project Manager)

Abstract:

The pressure to reduce noise emissions of aircrafts also forces engine manufacturers to acoustically optimise their engines. The noise level of the fan was reduced successfully within the last decades. Therefore, noise from the low pressure turbine becomes dominant and has to be reduced as well. In some project the large potential of different modifications of the turbine exit casing (TEC) to reduce noise was shown. The outcomes of this project will essentially increase knowledge by applying innovative modifications. Sound absorbing surfaces will be tested in order to reduce noise level at the dominant frequency in the sound field (blade passing frequency). As reference the most promising configurations have been chosen (leaned TEC and inverse cut-off TEC) and a state-of-the-art TEC. Firstly, the endwalls of the TEC will be modified with e.g. sound absorbing material and the effectiveness is evaluated. Secondly, the only vane surfaces are modified and thirdly, a combination will be tested. All in all different combinations of noise reduction measures will be tested. However, some of these modifications are altering surface roughness thus changing boundary layer development. In order to evaluate a possible change in rotor excitation vibration measurements with an existing telemetry system will be performed as well as an aerodynamically evaluation of the flow field. The outcomes allow to give recommendations and suggestions how to reduce noise level of aero engines considering aeroelasticity in order to perform a holistic optimisation. Further, these results increase knowledge gained in prior projects.

Objective:

1. Improved understanding of the physics of sound propagation downstream of LPTs
2. Reduction of sound emissions by means of different TEC modifications
3. Database for aeroacoustic code calibration
4. Establishment of design rules and a validation database

Instrumentation:

First results:

Theses: