Experimental Determination of the Effectiveness of a Sound Absorbing Turbine Exit Casing

Authors

Manuel Zenz - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
Florian Schönleitner - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
Loris Simonassi - DIMSET-University of Genova
Sabine Bauinger - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
Dominik Broszat - MTU Aero Engines
Franz Heitmeir - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology
Andreas Marn - Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology

Abstract

This work presents results from experimental investigations conducted in the subsonic test turbine facility for aerodynamic, acoustic, and aeroelastic investigations at Graz University of Technology. The experiments have been performed for the acoustically relevant operating point approach under engine relevant conditions. The sound absorbing exit guide vanes of the turbine exit casing have been designed as Helmholtz resonators with a resonance frequency according to the blade passing frequency of an aero design point. In order to prove the effectiveness of that exit guide vanes acoustic measurements and modal decomposition have been performed and the sound power per azimuthal mode was calculated and compared with results of a conventional hard wall exit guide vane of aerodynamic design. It is shown that the sound power level can be reduced significantly by about 23 dB. However, the losses are increased dramatically.