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research-article

On the influence of an acoustically optimized turbine exit casing onto the unsteady flow field downstream of a low pressure turbine rotor

[+] Author and Article Information
Loris Simonassi

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria
loris.simonassi@tugraz.at

Manuel Zenz

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria
manuel.zenz@tugraz.at

Stefan Zerobin

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria
stefan.zerobin@tugraz.at

Thorsten Selic

Elin Motoren GmbH, Weiz 8160, Austria
Thorsten.Selic@elinmotoren.at

Franz Heitmeir

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria
franz.heitmeir@tugraz.at

Andreas Marn

Institute for Thermal Turbomachinery and Machine Dynamics, Graz University of Technology, Graz 8010, Austria
andreas.marn@tugraz.at

1Corresponding author.

ASME doi:10.1115/1.4041540 History: Received August 17, 2018; Revised September 21, 2018

Abstract

Modern low pressure turbines (LPT) are designed in order to fulfil a various number of requirements. Regarding the reduction of the emitted noise, different designs of low pressure turbine exit guide vanes of the turbine exit casing (TEC) were tested and their noise reduction capabilities and aerodynamic performance were evaluated. Measurements were carried out in a one and a half stage subsonic turbine test facility at the engine relevant operating point approach. This work focuses on the study of the unsteady flow field downstream of an unshrouded low pressure turbine rotor. The influence on the upstream flow field of a TEC design including acoustically optimized vanes (Inverse cut-off TEC) is investigated and compared with a second TEC configuration without vanes (Vaneless TEC), by means of fast response aerodynamic pressure probe measurements. The second configuration served as a reference concerning the influence of TEGVs onto the upstream located LPT rotor. The interactions between the stator and rotor wakes, secondary flows and the turbine exit guide vanes potential effect are identified via modal decomposition according to the theory of Tyler and Sofrin. The main structures constituting the unsteady flow field are detected and the role of the major interaction effects in the loss generation mechanism and in the acoustic emission is analysed. This study based on the modal analysis of the unsteady flow field offers new insight into the main interaction mechanisms and their importance in the assessment of the aerodynamic and aeroelastic performance of modern low pressure turbine exit casings.

Copyright (c) 2018 by ASME
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