Research Papers

Calculation of Steady and Periodic Unsteady Blade Surface Heat Transfer in Separated Transitional Flow

[+] Author and Article Information
Roberto Pacciani

 “Sergio Stecco” Department of Energy Engineering, University of Florence, via di Santa Marta, 3, 50139, Firenze, ItalyRoberto.Pacciani@unifi.it

Filippo Rubechini, Andrea Arnone

 “Sergio Stecco” Department of Energy Engineering, University of Florence, via di Santa Marta, 3, 50139, Firenze, Italy

Ewald Lutum

 MTU Aero Engines GmbH, Dachauer Str. 665, 80995 Munchen, Germanyewald.lutum@mtu.de

J. Turbomach 134(6), 061037 (Sep 12, 2012) (8 pages) doi:10.1115/1.4006312 History: Received July 27, 2011; Revised July 28, 2011; Published September 12, 2012; Online September 12, 2012

In this work, aerothermal investigations of a highly loaded HP turbine blade are presented. The purpose of such investigations is to improve the physical understanding of the heat transfer in separated flow regions, with the final goal of optimizing cooling configurations for aerodynamically highly loaded turbine designs. The analysis is focused on the T120 cascade, that was recently tested experimentally in the framework of the European project AITEB-2 (Aero-thermal Investigation of Turbine Endwalls and Blades). Such a cascade has a relatively low solidity that is responsible for the formation of a laminar separation bubble on the suction side of the blade. Separated-flow transition and transonic conditions downstream of the throat result in a flow configuration that is very challenging for traditional RANS solvers. Moreover, the separated flow transition pattern was found to have a strong impact on both the aerodynamic and thermal aspects. The study was carried out using a novel three-equation, transition-sensitive, turbulence model. It is based on the coupling of an additional transport equation for the laminar kinetic energy to the Wilcox k - ω model. Such an approach allows one to take into account the increase of the nonturbulent fluctuations in the pretransitional and transitional region. Comprehensive aerodynamic and heat transfer measurements were available for comparison purposes. In particular, heat transfer measurements cover different Mach and Reynolds numbers, in both steady and periodic unsteady inflow conditions. A detailed comparison between measurements and computations is presented, and the impact of transition-related aspects on the surface heat transfer is discussed.

Copyright © 2012 by American Society of Mechanical Engineers
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Figure 1

Blade-To-blade section of the single-block 649 × 129 × 80 nonperiodic C-type grid for the T120S cascade

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Figure 6

T120S cascade: steady heat transfer distributions (Re2,is  = 3.9 · 105 )

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Figure 10

T120S cascade: comparison between steady and time-averaged heat transfer coefficient distributions (Re2,is  = 3.9 · 105 , M2,is  = 0.95)

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Figure 9

T120S cascade: heat transfer augmentation due to unsteady flow (Re2,is  = 1.2105 , M2,is  = 0.87)

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Figure 8

T120S cascade: space-time diagrams of (a) skin-friction coefficient, (b) turbulent kinetic energy, and (c) isentropic Mach number (Re2,is  = 3.9 · 105 , M2,is  = 0.87)

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Figure 7

T120S cascade: steady and time-averaged isentropic Mach-number distributions (Re2,is  = 3.9 · 105 , M2,is  = 0.87)

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Figure 5

T120S cascade. Distribution of wall-shear stress, laminar, and turbulent kinetic energy along the suction side (Re2,is  = 3.9 · 105 , M2,is  = 0.87).

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Figure 4

T120S cascade: density gradient and eddy viscosity contours superposed to streamlines in the separated flow region (1: separation point, 2: transition onset, 3: shock location, 4: reattachment location, Re2,is  = 3.9 · 105 )

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Figure 3

T120S cascade: steady isentropic Mach-number distributions (Re2,is  = 3.9 · 105 )

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Figure 2

T120C cascade: isentropic Mach-number distributions (Re2,is  = 3.9 · 105 , M2,is  = 0.87)




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