DOI: 10.1615/ICHMT.2015.IntSympAdvComputHeatTransf
ISBN Print: 978-1-56700-429-8
ISSN: 2578-5486
Multi-scale Approach to Turbine Heat Transfer and Aerodynamics
Краткое описание
Aerothermal design analysis of high pressure turbine blades in gas turbines/aero-engines
presents considerable challenges. Heat transfer and cooling analyses typically ask for higher
flow modelling fidelity and resolution than those for the blade path aerodynamic counterpart.
In particular, there are large scale disparities in terms of
- Time-scale: slow solid conduction vs fast fluid convection.
- Length-scale: macro passage flow vs micro film cooling flow etc.
In this presentation, some recent effort and progress using a multi-scale approach are
discussed. Firstly a general background problem statement is made in the context of
aerodynamics-heat transfer interaction, to highlight the relevance of including feedback of
heat transfer to aerodynamics. The lack of a framework in treating the wall boundary
condition for unsteady energy equation is highlighted, which should be fundamental to high
speed flows with heat transfer as those experienced in HP turbines. A new semi-analytical
harmonic transfer function is introduced as a baseline interface condition for unsteady
conjugate heat transfer with large temporal scale disparity. The semi-analytical method is
then extended to form a general multi-harmonic interfacing condition for both the timeaveraged
and fluctuating wall temperatures, as required for the unsteady energy equation in
LES applications. Computational examples are given to show the effectiveness of the present
unsteady conjugate heat transfer method.
The spatial length scale issue associated with film-cooling is addressed by adopting a blockspectral
method. A small subset discrete mesh blocks are solved with high local mesh
resolution, as required to resolve the small scale mixing and interactions between the film and
main stream. The pointwise block-to-block (hole-to-hole) variation is represented by a spatial
spectrum. An instantaneous whole domain solution can then be obtained efficiently by a
spectral mapping. The validity and effectiveness of the models are illustrated with
corresponding computational examples. The potential of using the present method for
resolving (rather than modelling) more general micro-scale problems, e.g. surface roughness,
is also indicated. Further details can be found in:
He, L. and Oldfield M.L.G. "Unsteady Conjugate Heat Transfer Modelling",
ASME Journal of Turbomachinery, Vol.133. No.3, July 2011.
He, L, "Block-Spectral Approach to Film-Cooling Modelling",
ASME Journal of Turbomachinery, Vol.134. No.2, March 2012.
He, L, "Block-Spectral Mapping for Multi-Scale Solution",
Journal of Computational Physics, Vol.250, pp13-26, Oct 2013.