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Research Papers: Gas Turbines: Turbomachinery

An Energy-Based Method for Predicting the Additive Effect of Multiple Film Cooling Rows

[+] Author and Article Information
Benjamin Kirollos

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: ben.kirollos@eng.ox.ac.uk

Thomas Povey

Osney Thermofluids Laboratory,
Department of Engineering Science,
University of Oxford,
Parks Road,
Oxford OX1 3PJ, UK
e-mail: thomas.povey@eng.ox.ac.uk

1Corresponding author.

Contributed by the Heat Transfer Committee of ASME for publication in the JOURNAL OF ENGINEERING FOR GAS TURBINES AND POWER. Manuscript received March 2, 2015; final manuscript received March 14, 2015; published online July 14, 2015. Editor: David Wisler.

J. Eng. Gas Turbines Power 137(12), 122607 (Jul 14, 2015) (7 pages) Paper No: GTP-15-1075; doi: 10.1115/1.4030907 History: Received March 02, 2015

There have been numerous studies reporting film effectiveness for film rows in isolation, which have led to correlations that are used for preliminary design. Many applications require multiple film cooling rows. Although there is some published data which deal with the combined effect of multiple rows, in most design situations the additive effect is computed using correlations for single rows. The most widely used method is the Sellers superposition method. In many applications, the method gives accurate results. Although the method is to some extent physically based, energy is not conserved within the model, and in certain situations this limitation can be shown to lead to an underprediction of the film effectiveness. In this paper, a new energy-based method for predicting the additive effect of multiple film cooling rows is outlined. The physical basis and limitations of the model are discussed. Predictions conducted using the new method are compared with computational fluid dynamics (CFD) data and contrasted with the Sellers method. In situations where energy conservation is required to avoid underprediction of effectiveness the method is shown to be advantageous.

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References

Figures

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Fig. 1

Layer temperatures using the Sellers [3] model

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Fig. 2

Control volume for a row in isolation [20]. Coolant is injected between xi-δx and xi, so for x<xi-δx, m·ei = 0.

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Fig. 3

Contol volume for the energy-based mixing model

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Fig. 4

CFD solution domain

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Fig. 5

CFD predictions of ηi(x). Injection locations are shown by vertical dotted lines.

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Fig. 6

Local entrainment rate of mainstream gas for film rows in isolation (g/s per domain pitch). Results are shown only in the region dηi/dx≤0, i.e., once the film is established.

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Fig. 7

Mass flow rate contained in each film layer m·i(x) (g/s per domain pitch)

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Fig. 8

CFD prediction of η(x) compared to prediction using the Sellers model and the proposed energy-based mixing model

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Fig. 9

Absolute difference between the film cooling effectiveness predicted by the Sellers model and the proposed model as a function of s/D and x/D

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