EFFECT OF SELF-SUSTAINED PULSATION OF COOLANT FLOW ON ADIABATIC EFFECTIVENESS AND NET HEAT FLUX REDUCTION ON A FLAT PLATE

Nicola Rosafio, Simone Salvadori, Daniela, Anna Misul, Mirko Baratta, Mauro Carnevale, Christian Saumweber

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

Advanced film-cooling systems are necessary to guarantee
safe working conditions of high-pressure turbine stages. A fair
prediction of the inherent unsteady interaction between the mainflow and the jet of cooling air allows for correctly describing the
complex flow structures arising close to the cooled region. This
proves to be crucial for the design of high-performance cooling
systems. Results obtained by means of an experimental campaign
performed at the University of Karlsruhe are shown along with
unsteady numerical data obtained for the corresponding working conditions. The experimental rig consists of an instrumented
plate where the hot flow reaches Mach = 0.6 close to the coolant
jet exit section. The numerical campaign models the unsteady
film cooling characteristics using a third-order accurate method.
The ANSYS® FLUENT® software is used along with a mesh refinement procedure that allows for accurately modelling the flow
field. Turbulence is modelled using the k-ω SST model. Timeaveraged and time-resolved distributions of adiabatic effectiveness and Net Heat Flux Reduction are analysed to determine to
what extent deterministic unsteadiness plays a role in cooling
systems. It is found that coolant pulsates due to fluctuations generated by flow separation at the inlet section of the cooling channel. Visualizations of the fluctuating flow field demonstrate that
coolant penetration depends on the phase of the pulsation, thus
leading to periodically reduced shielding. Eventually, unsteadiness occurring at integral length scales does not provide enough
mixing to match the experiments, thus hinting that the dominant
phenomena occur at inertial length scales.
Original languageEnglish
Title of host publicationProceedings of ASME Turbo Expo 2021
PublisherAmerican Society of Mechanical Engineers (ASME)
Publication statusAcceptance date - 16 Mar 2021

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