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Research Papers

Numerical Characterization of Pressure Drop Across the Manifold of Turbine Casing Cooling System

[+] Author and Article Information
Riccardo Da Soghe

e-mail: riccardo.dasoghe@htc.de.unifi.it

Antonio Andreini

Energy Engineering Department “S. Stecco,”
University of Florence,
50139, via S.Marta 3, Florence, Italy

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received June 28, 2012; final manuscript received August 9, 2012; published online March 25, 2013. Editor: David Wisler.

J. Turbomach 135(3), 031017 (Mar 25, 2013) (9 pages) Paper No: TURBO-12-1090; doi: 10.1115/1.4007506 History: Received June 28, 2012; Revised August 09, 2012

An array of jets is an arrangement typically used to cool several gas turbine parts. Some examples of such applications can be found in the impingement cooling systems of turbine blades and vanes or in the turbine blade tip clearances control of large aero-engines. In order to correctly evaluate the impinging jet mass flow rate, the characterization of holes discharge coefficient is a compulsory activity. In a previous work, the authors have performed an aerodynamic analysis of different arrays of jets for active clearance control; the aim was the definition of a correlation for the discharge coefficient (Cd) of a generic hole of the array. The developed empirical correlation expresses the (Cd) of each hole as a function of the ratio between the hole and the manifold mass velocity and the local value of the pressure ratio. In its original form, the correlation does not take in to account the effect of the hole length to diameter ratio (t/d) so, in the present contribution, the authors report a study with the aim of evaluating the influence of such parameter on the discharge coefficient distribution. The data were taken from a set of CFD RANS simulations, in which the behavior of the cooling system was investigated over a wide range of fluid-dynamics conditions (pressure-ratio = 1.01–1.6, t/d = 0.25–3). To point out the reliability of the CFD analysis, some comparisons with experimental data were drawn. An in depth analysis of the numerical data set has led to an improved correlation with a new term function of the hole length to diameter ratio.

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References

Figures

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Fig. 1

ACC system, Ahmed et al. [18]

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Fig. 2

Scheme of a LPT ACC system, Ahmed et al. [19]

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Fig. 6

CFD mesh sensitivity: geometry A mass flow rate split (%) in case of β = 1.12

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Fig. 5

Standard and refined CFD mesh for geometry A

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Fig. 7

CFD mesh sensitivity: geometry H mass flow rate split (%) in case of β = 1.1

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Fig. 8

CFD turbulence modeling sensitivity: geometry A mass flow rate split (%) in case of β = 1.12

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Fig. 9

Comparison between CFD and experimental results in terms of manifold centerline pressure distribution—geometry A

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Fig. 10

Discharge coefficient distribution: geometry D, E, F, G β = 1.1

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Fig. 11

Discharge coefficient distribution: geometries B, D, F, H, I, β = 1.1

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Fig. 12

Holes separation zones: normalized vector plot

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Fig. 19

Comparisons among correlation predictions and Gritsch et al. experimental data [9]: effects of manifold flow Mach number on discharge coefficient

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Fig. 17

Cd** over MVR parameter distribution: comparison among correlation prediction and whole CFD data set (i.e., all geometries and related operating conditions

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Fig. 18

Comparisons among correlation predictions and Gritsh et al. experimental data [9]: effects of jet-to-manifold flow momentum ratio on Cd distribution

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Fig. 13

Discharge coefficient over MVR parameter distribution: geometry B, F, H, β = 1.1

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Fig. 14

Cd* over MVR parameter distribution: case H, α = 1.19

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Fig. 15

Cd* over MVR parameter distribution: case B, F, H, α function of t/d (β = 1.1)

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Fig. 16

Cd** over MVR parameter distribution: whole CFD data set (i.e. all geometries and related operating conditions)

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Fig. 20

Comparisons among circular and squared supply manifold geometry

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