Poster (Scientific congresses and symposiums)
Purge and Leakage Effects on the Aerodynamics of a High Speed Low Pressure Turbine Cascade
Do Carmo Lopes, Gustavo Filipe; Lavagnoli, Sergio; Gendebien, Samuel et al.
2020ASME Turbo Expo 2020
 

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Abstract :
[en] The ultra-high bypass ratio geared turbofan (GTF) has been identified as a key engine concept to reduce emissions and noise footprint of the next generation of civil aircrafts. The increase in rotational speed of the low-pressure turbine (LPT) enabled by the geared architecture offers potential benefits in efficiency and considerable savings in engine weight, overall dimension and cost. However, the higher-pressure ratio implies that the LPT operates at transonic Mach number at the exit (Mis ~ 1), in combination with low Reynolds numbers. For this reason, increasing the efficiency levels of novel high-speed turbines with respect to conventional direct drive LPTs represents a challenge for the turbomachinery designers: Due to the operating conditions, secondary flows have different impact and structure compared to a conventional turbine. The secondary flows are further affected by purge flows. It is evident that there is a high demand for developing new engineering knowledge and reliable tools to design highly efficient and compact high-speed LPTs. However, detailed aerodynamic and performance measurements under engine representative conditions are in short supply. This shortage of relevant experimental data also concerns the impact of leakage and purge flows on the secondary flow structures development, and consequently on the high-speed LPTs loss mechanisms. The current research targets the investigation and understanding of the unsteady aerodynamics of the next-generation of high-speed LPTs and is part of a large EU-funded program named SPLEEN (SECONDARY AND LEAKAGE FLOW EFFECTS IN HIGH-SPEED LOW-PRESSURE TURBINES) led by the von Karman Institute in collaboration with Safran Aircraft Engines. The study focuses on the experimental characterization of the secondary flow structures and the interaction of cavity purge flows with the mainstream in high-speed LPT geometries tested at engine-scaled conditions. The cavity flow effects will be investigated in the VKI S-1/C large-scale high-speed linear cascade, operating at engine representative exit isentropic Mach and Reynolds numbers, and inflow conditions (free-stream turbulence and periodic wakes). Three cavity-airfoil arrangements will be investigated, representative of the leakage flow emerging from the stator-rotor hub cavity and of those leakage flows established between the casing and the tip of a shrouded rotor. The secondary air flow rates will also be varied to understand the impact of purge streams on the airfoil performance and 3D flow structure. A dense test matrix is envisaged to measure the aerodynamics of the LPT cascade in a time-averaged and time-resolved manner. Time-resolved total pressure and turbulence measurements will be performed to characterize the cascade inlet flow conditions, obtain boundary layer integral parameters and determine freestream turbulence intensity as well as length scales. The inlet and outlet three-dimensional and unsteady flows will be characterized by velocity, pressure and angle measurements thanks to pneumatic and fast-response aerodynamic probes. Quasi-shear stress measurements will characterize the boundary layer status on the blade and cascade endwall by means of surface mounted hot-films. Additionally, the cascade central blade and passage endwall will also be instrumented with pressure taps to investigate the time-averaged and time-resolved blade loading and endwall aerodynamics under simulated unsteady wakes and cavity flows. The output of this research work will consist in a high-fidelity database that will aid the development, tuning and validation of analytical and numerical prediction models used in the early design stages of future high efficiency and compact high-speed LPTs.
Disciplines :
Aerospace & aeronautics engineering
Author, co-author :
Do Carmo Lopes, Gustavo Filipe  ;  Université de Liège - ULiège > A&M
Lavagnoli, Sergio;  von Karman Institute for Fluid Dynamics > Turbomachinery > Professor
Gendebien, Samuel ;  von Karman Institute for Fluid Dynamics > Turbomachinery > Research Engineer
Hillewaert, Koen  ;  Université de Liège - ULiège > Département d'aérospatiale et mécanique > Design of Turbomachines
Language :
English
Title :
Purge and Leakage Effects on the Aerodynamics of a High Speed Low Pressure Turbine Cascade
Publication date :
September 2020
Number of pages :
A2
Event name :
ASME Turbo Expo 2020
Event organizer :
ASME
Event place :
online (original London UK), United Kingdom
Event date :
September 21-25, 2020
Audience :
International
European Projects :
H2020 - 820883 - SPLEEN - Secondary and Leakage Flow Effects in High-SPeed Low-PrEssurE TurbiNes
Funders :
CleanSky II
CE - Commission Européenne [BE]
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since 11 August 2021

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