Validation of an integrated acoustic absorber in a turbine exit guide vane

Abstract

Within the scope of previous papers, the general setup of an acoustic turbine test facility at the Graz University of Technology has been presented. In addition, its significance for the validation of acoustic prediction tools and the verification of noise reduction features related to the LPT (Low Pressure Turbine) has been highlighted. In contrast to the passive noise reduction feature presented last year, the purpose of the present paper is the verification of an innovative integrated acoustic absorber. It considerably extends the available area for acoustic lining in the tailpipe downstream of the LPT by integrating it into the Turbine Exit Case (TEC). The innovative absorber has been acoustically designed for a maximum area utilization and tested at the above mentioned cold flow LPT rig. In parallel, numerical predictions based on the MTU in-house Linearized Euler (LEE) tool have been performed and compared to the results of the experimental investigations. The results show a very promising noise reduction potential of the integrated TEC absorber with a relatively broadband attenuation characteristic that allowed for a noticeable effect at all three acoustic operating conditions as well as the first and second Blade Passage Frequency (BPF). In addition, they, again, demonstrate the adequate correlation of the LEE predictions with the experimental data and its qualification as a design tool.