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Research Papers

Second Law Analysis of Aerodynamic Losses: Results for a Cambered Vane With and Without Film Cooling

[+] Author and Article Information
Phil Ligrani

Oliver L. Parks Endowed Chair,
Professor of Aerospace and Mechanical Engineering,
Director of Graduate Programs
e-mail: pligrani@slu.edu

Jae Sik Jin

Post-Doctoral Research Fellow
Department of Aerospace and Mechanical Engineering,
Parks College of Engineering, Aviation, and Technology,
Saint Louis University,
3450 Lindell Boulevard,
McDonnell Douglas Hall, Room 1033A,
St. Louis, MO 63103

1Corresponding author.

Contributed by the International Gas Turbine Institute (IGTI) Division of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received July 9, 2012; final manuscript received July 17, 2012; published online June 5, 2013. Assoc. Editor: David Wisler.

J. Turbomach 135(4), 041013 (Jun 05, 2013) (14 pages) Paper No: TURBO-12-1135; doi: 10.1115/1.4007588 History: Received July 09, 2012; Revised July 17, 2012

Results of second law analysis of experimentally-measured aerodynamic losses are presented for a cambered vane with and without film cooling, including comparisons with similar results from a symmetric airfoil. Included are distributions of local entropy creation, as well as mass-averaged magnitudes of global exergy destruction. The axial chord length of the cambered vane is 4.85 cm, the true chord length is 7.27 cm, and the effective pitch is 6.35 cm. Data are presented for three airfoil Mex distributions (including one wherein the flow is transonic), magnitudes of inlet turbulence intensity from 1.1% to 8.2%, and ks/cx surface roughness values of 0, 0.00108, and 0.00258. The associated second law aerodynamics losses are presented for two different measurement locations downstream of the vane trailing edge (one axial chord length and 0.25 axial chord length). The surface roughness, when present, simulates characteristics of the actual roughness which develops on operating turbine airfoils from a utility power engine, over long operating times, due to particulate deposition and to spallation of thermal barrier coatings. Quantitative surface roughness characteristics which are matched include equivalent sandgrain roughness size, as well as the irregularity, nonuniformity, and the three-dimensional irregular arrangement of the roughness. Relative to a smooth, symmetric airfoil with no film cooling at low Mach number and low freestream turbulence intensity, overall, the largest increases in exergy destruction occur with increasing Mach number, and increasing surface roughness. Important variations are also observed as airfoil camber changes. Progressively smaller mass-averaged exergy destruction increases are then observed with changes of freestream turbulence intensity, and different film cooling conditions. In addition, the dependences of overall exergy destruction magnitudes on mainstream turbulence intensity and freestream Mach number are vastly different as level of vane surface roughness changes. When film cooling is present, overall mass-averaged exergy destruction magnitudes are significantly less than values associated with increased airfoil surface roughness for both the cambered vane and the symmetric airfoil. Dimensional exergy destruction values (associated with wake aerodynamic losses) for the symmetric airfoil with film cooling are then significantly higher than data from the cambered vane with film cooling, when compared at a particular blowing ratio.

Copyright © 2013 by ASME
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References

Figures

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Fig. 1

Cambered vane test section

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Fig. 2

Film cooling hole configurations for cambered vane. (a) Round axial (RA), (b) Round radial (RR), (c) Shaped axial (SA), (d) Round compound (RC).

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Fig. 3

Film cooling hole locations for the cambered vane

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Fig. 4

Mach number distributions along the test vane

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Fig. 5

Three-dimensional Wyko profilometry traces of portions of the rough surfaces. (a) Simulated rough surface with small-sized roughness elements. (b) Rough surface from the pressure side of a turbine vane with particulate deposition from a utility power engine.

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Fig. 6

Dependence of the ratio of equivalent sandgrain roughness size to mean roughness height on the Sigal and Danberg [20] roughness parameter for the present study, and the Schlichting [18], Coleman et al. [19], and the van Rij et al. [22] investigations

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Fig. 7

Test section vanes with rough surfaces. (a) Vane with uniform roughness. (b) Vane with variable roughness on pressure side.

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Fig. 8

Entropy creation profiles downstream of the cambered vane at different exit Mach numbers Mex, measured at x/cx = 1.0 for Tu of 1.1 to 1.6% and ks/cx = 0

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Fig. 9

Entropy creation profiles downstream of the cambered vane with varying freestream turbulence intensity Tu for Mex = 0.35 and ks/cx = 0. (a) x/cx = 0.25, (b) x/cx = 1.0.

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Fig. 10

Entropy creation profiles downstream of the cambered vane with varying freestream turbulence intensity Tu for Mex = 0.71 and ks/cx = 0. (a) x/cx = 0.25, (b) x/cx = 1.0

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Fig. 11

Entropy creation profiles downstream of the cambered vane with varying surface roughness for Mex = 0.71 and Tu of 1.1%. (a) x/cx = 0.25, and (b) x/cx = 1.0

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Fig. 12

Entropy creation profiles downstream of the cambered vane with varying surface roughness for x/cx = 1.0. (a) Mex = 0.50 and Tu of 1.2%, (b) Mex = 0.35 and Tu of 1.6%.

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Fig. 13

Entropy creation profiles downstream of the cambered vane with film cooling from the first row of holes only for x/cx = 1.0, Mex = 0.35, Tu of 5.7%, and ks/cx = 0. (a) m = 0.6, (b) m = 1.2.

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Fig. 14

Entropy creation profiles downstream of the cambered vane with film cooling from both rows of holes for x/cx = 1.0, Mex = 0.35, Tu of 5.7%, and ks/cx = 0. (a) m = 0.6, (b) m = 1.2.

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Fig. 15

Normalized overall exergy destruction as it varies with surface roughness condition for different measurement locations downstream of the cambered vane and the symmetric airfoil with different exit Mach numbers, for freestream turbulence intensity values from 1.1 to 1.6%

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Fig. 16

Normalized overall exergy destruction as it varies with surface freestream turbulence intensity for different measurement locations downstream of the cambered vane and the symmetric airfoil with smooth surfaces (ks/cx = 0) with different exit Mach numbers

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Fig. 17

Normalized overall exergy destruction as it varies with film cooling blowing ratio as measured one axial chord length downstream of the cambered vane and the symmetric airfoil with different exit Mach numbers, and different film cooling configurations and conditions for x/cx = 1.0, Mex = 0.35, Tu of 5.7%, and ks/cx = 0

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