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Dependence of External Heat Transfer Coefficient and Aerodynamics on Wall Temperature for 3-D Turbine Blade Passage

[+] Author Affiliations
R. Maffulli, L. He

Oxford University, Oxford, UK

Paper No. GT2014-26763, pp. V02CT38A046; 13 pages
doi:10.1115/GT2014-26763
From:
  • ASME Turbo Expo 2014: Turbine Technical Conference and Exposition
  • Volume 2C: Turbomachinery
  • Düsseldorf, Germany, June 16–20, 2014
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-4562-2
  • Copyright © 2014 by ASME

abstract

The dependency of convective heat transfer coefficient (HTC) on wall temperature has been recognized in some previous works but existing corrections are confined to either empirically based correlations or based on a boundary layer approach. A recent study by the present authors on a 2D configuration highlights upstream flow history has a strong impact on HTC for a non-adiabatic blade surface, and such an effect cannot be adequately corrected by the use of existing empirical correlations. A boundary layer based approach may be used in a 2D case for the correction as attempted previously. However, it is strongly argued that a boundary layer based method would become very difficult, if not impossible, to apply for complex 3D flows as those in endwall and secondary flow regions of a turbine blade passage.

The present work is aimed to examine how the HTC and main 3D passage aerodynamic features of interest may be affected by the wall temperature condition. A systematic computational study has been firstly carried out for a 3D NGV passage. The impacts of wall temperature on the secondary flows, trailing edge shock waves and the passage flow capacity are discussed, underlining the connection and interactions between the wall temperature and the external aerodynamics of the 3D passage. The local errors in HTC in these 3D flow regions can be as high as 30–40% if the wall temperature dependence is not corrected.

The effort is then directed to a new 3-point non-linear correction method. The benefit of the 3-point method in reducing errors in HTC is clearly demonstrated. A further study illustrates that the new method also offers much enhanced robustness in the HTC procedure, particularly relevant when the wall thermal condition is shown to influence the laminar-turbulent transition as exhibited by two well-established transition models adopted in the present work.

Copyright © 2014 by ASME

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