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Research Papers

Film Cooling Extraction Effects on the Aero-Thermal Characteristics of Rib Roughened Cooling Channel Flow

[+] Author and Article Information
Beni Cukurel

e-mail: cukurel@vki.ac.be

Claudio Selcan

e-mail: selcan@vki.ac.be

Tony Arts

e-mail: arts@vki.ac.be
von Karman Institute for Fluid Dynamics,
Chaussée de Waterloo, 72, B-1640,
Rhode-St-Genèse, Belgium

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 5, 2012; published online November 2, 2012. Editor: David Wisler.

J. Turbomach 135(2), 021016 (Nov 02, 2012) (12 pages) Paper No: TURBO-12-1084; doi: 10.1115/1.4007501 History: Received June 28, 2012; Revised August 05, 2012

The present study is geared towards quantifying the effects of film cooling holes on turbine internal cooling passages. In this regard, tests are conducted in a generic stationary model, with evenly distributed rib-type perturbators at 90 deg, constituting a passage blockage ratio of H/Dh = 0.3 and pitch-to-height ratio of P/H = 10. The 1/3H diameter surface-perpendicular film cooling holes are employed at a distance of 5/3H downstream of the preceding rib. Through liquid crystal thermometry measurements, the aero-thermal effects of a change in suction ratio are contrasted for various configurations (Re = 40,000 SR = 0–6), and compared with the analogous aerodynamic literature, enabling heat transfer distributions to be associated with distinct flow structures. At increased suction ratio, the size of the separation bubble downstream of the rib is observed to diminish, triggering globally an earlier reattachment; in addition to low-momentum hot fluid extraction via film cooling suction. Hence, in the presence of active flow extraction, higher overall heat transfer characteristics are observed throughout the channel. Moreover, the findings are generalized via friction factor and Nusselt number correlations, along with an analytical 20-pitch passage model. SR ∼ 3.5 is observed to provide favorable characteristics of pitch-to-pitch uniform suction ratio, lack of hot fluid ingestion and to sustain the highest passage averaged heat transfer.

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References

Figures

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Fig. 1

Schematic of the experimental setup

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Fig. 2

Typical hue temperature calibration curve

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Fig. 3

Convective ribbed wall perspective mapping

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Fig. 4

Normalized heat flux distribution around a hole

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Fig. 5

Normalized heat flux distribution around a rib

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Fig. 6

Visualization of the ribbed channel flow field [11]

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Fig. 7

Rib downstream flow (a) without film cooling hole (b) with film cooling hole [13]

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Fig. 10

Generalized cooling hole setup—control volumes

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Fig. 11

Wall friction factor at various suction ratios

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Fig. 9

Laterally averaged EF at various suction ratios

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Fig. 8

Effects of suction ratio on EF distributions

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Fig. 12

20 Blade model—local SR at each pitch

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Fig. 13

Blade model—Nusselt number average up until each pitch

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