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Research Papers: Energy Systems Analysis

Cooling of Turbine Blades With Expanded Exit Holes: Computational Analyses of Leading Edge and Pressure-Side of a Turbine Blade

[+] Author and Article Information
Fariborz Forghan, Uichiro Narusawa, Hameed Metghalchi

Department of Mechanical and
Industrial Engineering,
Northeastern University,
Boston, MA 02115

Omid Askari

Department of Mechanical Engineering,
Mississippi State University,
Starkville, MS 39762

Contributed by the Advanced Energy Systems Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received December 14, 2016; final manuscript received December 26, 2016; published online March 8, 2017. Special Editor: Reza Sheikhi.

J. Energy Resour. Technol 139(4), 042004 (Mar 08, 2017) (7 pages) Paper No: JERT-16-1508; doi: 10.1115/1.4035829 History: Received December 14, 2016; Revised December 26, 2016

Turbine blades are cooled by a jet flow from expanded exit holes (EEH) forming a low-temperature film over the blade surface. Subsequent to our report on the suction-side (low-pressure, high-speed region), computational analyses are performed to examine the cooling effectiveness of the flow from EEH located at the leading edge as well as at the pressure-side (high-pressure, low-speed region). Unlike the case of the suction-side, the flow through EEH on the pressure-side is either subsonic or transonic with a weak shock front. The cooling effectiveness, η (defined as the temperature difference between the hot gas and the blade surface as a fraction of that between the hot gas and the cooling jet), is higher than the suction-side along the surface near the exit of EEH. However, its magnitude declines sharply with an increase in the distance from EEH. Significant effects on the magnitude of η are observed and discussed in detail of (1) the coolant mass flow rate (0.001, 0.002, and 0.004 (kg/s)), (2) EEH configurations at the leading edge (vertical EEH at the stagnation point, 50 deg into the leading-edge suction-side, and 50 deg into the leading-edge pressure-side), (3) EEH configurations in the midregion of the pressure-side (90 deg (perpendicular to the mainstream flow), 30 deg EEH tilt toward upstream, and 30 deg tilt toward downstream), and (4) the inclination angle of EEH.

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Figures

Grahic Jump Location
Fig. 4

Profiles around EEH at the leading-edge suction-side: (a) temperature,  = 4 × 10−3 (kg/s), (b) the Mach number,  = 4 × 10−3 (kg/s), and (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 5

Profiles around EEH at the leading-edge pressure-side: (a) temperature,  = 4 × 10−3 (kg/s), (b) the Mach number,  = 4 × 10−3 (kg/s), and (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 3

Profiles around EEH at the leading-edge stagnation point (EEH axis normal to the blade surface): (a) temperature with  = 4 × 10−3 (kg/s), (b) the Mach number with  = 4 × 10−3 (kg/s), (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 2

η (cooling effectiveness) versus S/Dt (distance from the edge of EEH, normalized with respect to EEH throat (minimum) diameter). Filled triangle experiment from Ref. [22] and solid curve—this study. (Reproduced with permission from Forghan et al. [47]. Copyright 2016 by ASME).

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Fig. 1

Blade cross section at the midplane, hole angle of 90 deg from the blade surface on the pressure-side

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Fig. 6

Profiles around EEH at pressure-side central region, φ = 90 deg: (a) temperature,  = 4 × 10−3 (kg/s), (b) the Mach number,  = 4 × 10−3 (kg/s), and (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 7

Profiles around EEH at pressure-side central region, φ = 120 deg: (a) temperature,  = 4 × 10−3 (kg/s), (b) the Mach number,  = 4 × 10−3 (kg/s), and (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 8

Profiles around EEH at pressure-side central region, φ = 60 deg: (a) temperature,  = 4 × 10−3 (kg/s), (b) the Mach number,  = 4 × 10−3 (kg/s), and (c) η versus S/Dt (right dotted—pressure-side, left solid—suction-side, bottom curves for  = 10−3 (kg/s), middle curves for 2 × 10−3 (kg/s), and top curves for 4 × 10−3 (kg/s))

Grahic Jump Location
Fig. 9

Temperature profile around EEH at the pressure-side, showing the hot mainstream gas penetrating into EEH due to low coolant flow ( = 10−3 (kg/s))

Grahic Jump Location
Fig. 10

Temperature profile of the pressure-side EEH 30 deg to the right: (a) coolant flow rate = 0.002 (kg/s) and (b) coolant flow rate = 0.001 (kg/s)

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