Mechanical Engineering; Energy Engineering and Power Technology; Aerospace Engineering
Abstract :
[en] The influence of unsteady wakes incoming from the upstream stages is of high relevance in modern high-speed, low-pressure turbines (LPT) operating at transonic exit Mach numbers and low Reynolds numbers for their potential to trigger transition and influence the separation of the boundary layer on the blade suction side. The aim of this paper is the experimental characterization of the influence of incoming wakes on the 2D aerodynamics of a high-speed LPT cascade operating at a low Reynolds number and transonic exit Mach number. A detailed analysis of the status of the flow along the blade under investigation and its impact on the profile loss are presented for a range of Mach numbers from 0.70 to 0.95 and Reynolds numbers from 70k to 120k under steady and unsteady inflow conditions. Tests were conducted at on- and off-design engine realistic conditions in the VKI S-1/C wind tunnel on the SPLEEN C1 transonic cascade. The wakes incoming from an upstream blade row have been replicated using a set of rotating bars, which shed wakes at an engine-representative reduced frequency (f+=0.95) and flow coefficient (Φ=0.80). A set of densely instrumented traversable blades were used to sample the surface pressure distributions. The development of the boundary layers along the blade suction side is examined through quasi-wall shear stress obtained with surface-mounted hot-film sensors. Wake traverses were carried out downstream of the cascade with a miniaturized L-shaped five-hole probe to characterize the blade losses. The introduction of periodic incoming wakes promotes variations in the flow topology over the blade. The effect on the suction side separation bubble is shown to depend on the exit flow conditions. At low Mach numbers, the incoming wakes determine a reduction in the size of the bubble; in contrast, this effect is not registered as the exit Mach number increases. Consistently, a high dependence of the unsteady wake effect on the profile loss on the exit Reynolds and Mach numbers is demonstrated.
Disciplines :
Aerospace & aeronautics engineering
Author, co-author :
Simonassi, Loris; Turbomachinery and Propulsion Department, Von Kàrmàn Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Belgium
Do Carmo Lopes, Gustavo Filipe ; Université de Liège - ULiège > Aérospatiale et Mécanique (A&M) ; Turbomachinery and Propulsion Department, Von Kàrmàn Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Belgium
Lavagnoli, Sergio ; Turbomachinery and Propulsion Department, Von Kàrmàn Institute for Fluid Dynamics, Chaussée de Waterloo 72, 1640 Rhode-St-Genèse, Belgium
Language :
English
Title :
Effects of Periodic Incoming Wakes on the Aerodynamics of a High-Speed Low-Pressure Turbine Cascade
Publication date :
13 September 2023
Journal title :
International Journal of Turbomachinery, Propulsion and Power
H2020 - 820883 - SPLEEN - Secondary and Leakage Flow Effects in High-SPeed Low-PrEssurE TurbiNes
Name of the research project :
Clean Sky
Funders :
Union Européenne [BE]
Funding text :
This research was funded by the Clean Sky 2 Joint Undertaking under the European Unions Horizon 2020 research and innovation program under the grant agreement 820883.
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