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The 11 February 2019 at 14h00

PhD Defense: Thomas GROSNICKEL – ” Large eddy simulations to predict internal turbine blade cooling flows”

Nicole BOUTET |  CERFACS, CONFERENCE ROOM J.-C. André |  

Abstract

Aeronautical engine designers are constantly subject to increasing power demands from aircraft manufacturers. To satisfy this requirement, combustor outlet temperature can be increased to improve efficiency and output energy of the engine. This rise in temperature however can surpass the material melting point and to avoid engine failure, turbine blades rely on internal cooling systems. Turbine blade cooling often uses internal channels, taking cold air from the compressor flow. Design of these systems therefore resumes to maximizing heat transfer enhancement while minimizing airflow rate to avoid engine power penalties. However, such flows are still largely uncontrolled and miss-understood. In an attempt to better understand such spatially developing rotating flows, the present study deals with a computational investigation on a straight, rotating rib roughened cooling channel. The configuration consists in a squared channel equipped with 8 ribs turbulators placed with an angle of 90 degrees with respect to the flow direction. For the studied cases, time resolved two-dimensional Particle Image Velocimetry (PIV) measurements have been performed at the Van Karman Institute (VKI). Adiabatic as well as isothermal conditions have been investigated to evaluate the impact of the wall temperature on the flow, especially in the rotating configurations.  Static as well as both positive and negative rotating channels are compared with, in each case, either an adiabatic or an isothermal flow prediction. In this work, Large Eddy Simulation (LES) results show that the high fidelity CFD model is able to reproduce the differences induced by buoyancy on the flow topology in the near rib region and resulting from an adiabatic or an isothermal flow in rotation.  The model manages also to predict the turbulence increase (decrease) around the rib in destabilizing (stabilizing) rotation of the ribbed channels. Finally and thanks to the full spatial and temporal description produced by LES, the spatial development and the unsteadiness of secondary flows are analyzed to better understand their origin and potential differences in all a cases. This study shows that the wall heat flux topology is driven by the secondary flows structure and the wall heat flux intensity is driven by the level of flow fluctuations in the ribbed region.

Keywords – LES – Turbomachinery – Ribbed channel – Cooling

Jury

Prof. Tom VERSTRAETE                       University of Gand, Belgium                                  Referee
Mr. Matthieu FENOT                              Pprime  ISAE-ENSMA Futuroscope, France         Referee
Prof. Antonius ARTS                              University of Louvain, Belgium                              Member
Prof. Françoise  BATAILLE                     PROMES-CNRS, Perpignan,France                    Member
Mr. Laurent GICQUEL                            CERFACS, Toulouse, France                               Advisor

Mr. Florent DUCHAINE                           CERFACS, Toulouse, France                              Co advisor
Mr. Charlie KOUPPER                            Safran Helicopter Engines, Bordes, France        Invited member

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