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Research Papers

Evolution of Surface Deposits on a High-Pressure Turbine Blade—Part II: Convective Heat Transfer

[+] Author and Article Information
Jeffrey P. Bons, James E. Wammack, Jared Crosby, Daniel Fletcher

Department of Mechanical Engineering,  Brigham Young University, Provo, UT 84602

Thomas H. Fletcher

Department of Chemical Engineering,  Brigham Young University, Provo, UT 84602

J. Turbomach 130(2), 021021 (Mar 25, 2008) (7 pages) doi:10.1115/1.2752183 History: Received September 08, 2006; Revised November 15, 2006; Published March 25, 2008

A thermal barrier coating (TBC)-coated turbine blade coupon was exposed to successive deposition in an accelerated deposition facility simulating flow conditions at the inlet to a first stage high pressure turbine (T=1150°C, M=0.31). The combustor exit flow was seeded with dust particulate that would typically be ingested by a large utility power plant. The turbine coupon was subjected to four successive 2h deposition tests. The particulate loading was scaled to simulate 0.02 parts per million weight (ppmw) of particulate over 3months of continuous gas turbine operation for each 2h laboratory simulation (for a cumulative 1year of operation). Three-dimensional maps of the deposit-roughened surfaces were created between each test, representing a total of four measurements evenly spaced through the lifecycle of a turbine blade surface. From these measurements, scaled models were produced for testing in a low-speed wind tunnel with a turbulent, zero pressure gradient boundary layer at Re=750,000. The average surface heat transfer coefficient was measured using a transient surface temperature measurement technique. Stanton number increases initially with deposition but then levels off as the surface becomes less peaked. Subsequent deposition exposure then produces a second increase in St. Surface maps of St highlight the local influence of deposit peaks with regard to heat transfer.

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Copyright © 2008 by American Society of Mechanical Engineers
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Figures

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Figure 1

Surface topologies of 3.3mm×4.2mm from surface deposit on TBC1 coupon after each burn. Vertical scale shows peak roughness height.

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Figure 2

Roughness statistics for the scaled model surface

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Figure 3

Wind Tunnel Facility

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Figure 4

Stanton number augmentation and roughness statistics for the scaled roughness models

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Figure 5

Comparison of experimental St augmentation with empirical prediction

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Figure 6

Heat transfer coefficient and surface height plots for a 67mm×83mm region on the Burn 1 and 2 roughness models. (Flow direction is from top to bottom as indicated.) Wake regions with elevated St values are circled: (a) Burn 1 surface height contour plot (mm); (b) Burn 1 St contour map; (c) Burn 2 surface height contour plot (mm); and (d) Burn 2 St contour map.

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