Research Papers

Scaling of Turbine Metal Temperatures in Cooled Compressible Flows—Experimental Demonstration of a New Theory

[+] Author and Article Information
S. Luque

Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: salvador.luque@imdea.org

T. V. Jones, T. Povey

Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK

1Corresponding author.

2Present address: IMDEA Energy Institute, Unit of High Temperature Processes, Avda. Ramon de la Sagra, 3, Mostoles 28935, Spain.

Manuscript received June 15, 2016; final manuscript received December 21, 2016; published online March 15, 2017. Assoc. Editor: David G. Bogard.

J. Turbomach 139(8), 081001 (Mar 15, 2017) (10 pages) Paper No: TURBO-16-1117; doi: 10.1115/1.4035831 History: Received June 15, 2016; Revised December 21, 2016

Experimental measurements of overall cooling effectiveness conducted on a high-pressure turbine vane in a warm rig flow are scaled to engine conditions in this paper. A new theory for the scaling of turbine metal temperatures in cooled compressible flows has been applied, based on the principle of superposition, and demonstrated analytically and numerically in a previous paper. The analysis employs a definition of overall cooling effectiveness based on a new recovery and redistribution temperature, which makes it independent of the temperature boundary conditions of the hot and cold flow streams. This enables the vane external wall temperatures to be scaled to engine conditions by varying, in a fixed aerodynamic field, the mainstream-to-coolant temperature ratio. Experimental validation of the theory is provided in this article. Measurements were conducted in the Annular Sector Heat Transfer Facility, which employs fully cooled nozzle guide vanes, production parts of a civil aviation engine currently in service. Mainstream Mach and Reynolds numbers, inlet turbulence intensity, and coolant-to-mainstream total pressure ratio (and thus momentum flux ratio) are all matched to engine conditions. Full-coverage overall cooling effectiveness distributions, acquired by infrared thermography, are presented for a range of mainstream-to-coolant temperature ratios between 1.05 and 1.22 and subsequently scaled to engine conditions by an iterative procedure. In reducing to practice the principles of the new scaling theory, it is demonstrated that direct validation of turbine cooling system performance is possible in experiments at lower than engine temperatures.

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Fig. 1

Two-dimensional unwrapped schematic of the Annular Sector Heat Transfer Facility working section

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Fig. 2

Cooling configuration of the HP turbine NGV, schematic sketch (not to scale). Adapted from Ref. [9].

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Fig. 3

IR camera calibration curve of temperature against normalized grayscale intensity

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Fig. 4

Full-coverage surface map of overall cooling effectiveness (incompressible definition), at T01/T02= 1.22

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Fig. 5

Midspan distributions of overall cooling effectiveness: incompressible definition

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Fig. 6

Normalized RMS residuals in ϕ, ℜ, and Erad for the series of 26 tests conducted on the suction surface

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Fig. 7

Midspan distributions of overall cooling effectiveness: compressible definition

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Fig. 8

Average distribution and 95% confidence interval for data presented in Fig. 7

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Fig. 9

Midspan distributions of ℜ and Tr/T01 for both laminar and turbulent boundary layers

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Fig. 10

Midspan distributions of a conventionally scaled effectiveness for a turbulent boundary layer

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Fig. 11

Average distribution and 95% confidence interval for data presented in Fig. 10

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Fig. 12

Invariant overall cooling effectiveness distribution, ϕ, for the HP turbine NGV considered

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Fig. 13

Surface map of the recovery and redistribution parameter, ℜ=Tℜ/T01, for the correct scaling of ϕ

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Fig. 14

Contours of absolute error in ϕ, including the stray radiation term, as a function of T01/T02 and ϕ itself




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