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Research Papers

Heat Transfer and Pressure Loss Measurements of Matrix Cooling Geometries for Gas Turbine Airfoils

[+] Author and Article Information
Carlo Carcasci

Assistant Professor
Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: carlo.carcasci@htc.de.unifi.it

Bruno Facchini

Associate Professor
Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: bruno.facchini@htc.de.unifi.it

Marco Pievaroli

Department of Industrial Engineering,
University of Florence,
Florence 50139, Italy
e-mail: marco.pievaroli@htc.de.unifi.it

Lorenzo Tarchi

ERGON Research s.r.l.,
Florence 50127, Italy
e-mail: lorenzo.tarchi@ergonresearch.it

Alberto Ceccherini

GE Oil & Gas,
Florence 50127, Italy
e-mail: Alberto.Ceccherini@ge.com

Luca Innocenti

GE Oil & Gas,
Florence 50127, Italy
e-mail: Luca1.Innocenti@ge.com

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) Division of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 11, 2014; final manuscript received July 24, 2014; published online August 26, 2014. Editor: Ronald Bunker.

J. Turbomach 136(12), 121005 (Aug 26, 2014) (8 pages) Paper No: TURBO-14-1132; doi: 10.1115/1.4028237 History: Received July 11, 2014; Revised July 24, 2014

Matrix cooling systems are relatively unknown among gas turbines manufacturers of the western world. In comparison to conventional turbulated serpentines or pin–fin geometries, a lattice–matrix structure can potentially provide higher heat transfer enhancement levels with similar overall pressure losses. This experimental investigation provides heat transfer distribution and pressure drop of four different lattice–matrix geometries with crossing angle of 45 deg between ribs. The four geometries are characterized by two different values of rib height, which span from a possible application in the midchord region up to the trailing edge region of a gas turbine airfoil. For each rib height, two different configurations have been studied: one having four entry channels and lower rib thickness (open area 84.5%), one having six entry channels and higher rib thickness (open area 53.5%). Experiments were performed varying the Reynolds number Res, based on the inlet subchannel hydraulic diameter, from 2000 to 12,000. Heat transfer coefficients (HTCs) were measured using steady state tests and applying a regional average method; test models have been divided into 20 stainless steel elements in order to have a Biot number similitude with real conditions. Elements are 10 per side, five in the main flow direction, and two in the tangential one. Metal temperature was measured with embedded thermocouples, and 20 thin-foil heaters were used to provide a constant heat flux during each test. A specific data reduction procedure has been developed so as to take into account the fin effectiveness and the increased heat transfer surface area provided by the ribs. Pressure drops were also evaluated measuring pressure along the test models. Uniform streamwise distributions of Nusselt number Nus have been obtained for each Reynolds number. Measurements show that the heat transfer enhancement level Nus/Nu0 decreases with Reynolds but is always higher than 2. Results have been compared with previous literature data on similar geometries and show a good agreement.

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Figures

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Fig. 1

Example of lattice cooled blade [1] and schematic of subchannel flow

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Fig. 5

Geometric parameters of tested matrix geometries

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Fig. 6

Heat fluxes and wall temperature distribution through a single matrix block

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Fig. 7

Pressure taps locations along different subchannel tracks

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Fig. 8

Pressure ratios distribution along track 1

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Fig. 9

Normalized friction factor (f/f0) for different Res

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Fig. 10

Subchannel averaged Nusselt numbers Nueq,s for different Res

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Fig. 11

Subchannel averaged Nusselt numbers Nueq,s as a function of streamwise location at the same mass flow rate

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Fig. 12

Nur,s/Nu0 comparison with Saha et al. [7] for different Res

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Fig. 13

Nur,s/Nu0 comparison with Acharya et al. [8] for different Res

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