Research Papers: Gas Turbines: Combustion, Fuels, and Emissions

Effects of Temperature and Particle Size on Deposition in Land Based Turbines

[+] Author and Article Information
Jared M. Crosby, Scott Lewis, Jeffrey P. Bons

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

Weiguo Ai, Thomas H. Fletcher

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

J. Eng. Gas Turbines Power 130(5), 051503 (Jun 13, 2008) (9 pages) doi:10.1115/1.2903901 History: Received September 10, 2007; Revised December 13, 2007; Published June 13, 2008

Four series of tests were performed in an accelerated deposition test facility to study the independent effects of particle size, gas temperature, and metal temperature on ash deposits from two candidate power turbine synfuels (coal and petcoke). The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes while accelerating the deposition process. Particle size was found to have a significant effect on capture efficiency with larger particles causing significant thermal barrier coating (TBC) spallation during a 4 h accelerated test. In the second series of tests, particle deposition rate was found to decrease with decreasing gas temperature. The threshold gas temperature for deposition was approximately 960°C. In the third and fourth test series, impingement cooling was applied to the back side of the target coupon to simulate internal vane cooling. Capture efficiency was reduced with increasing mass flow of coolant air; however, at low levels of cooling, the deposits attached more tenaciously to the TBC layer. Postexposure analyses of the third test series (scanning electron microscopy and X-ray spectroscopy) show decreasing TBC damage with increased cooling levels.

Copyright © 2008 by American Society of Mechanical Engineers
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Figure 1

BYU Turbine Accelerated Deposition Facility schematic

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Figure 2

Equilibration tube exit temperature profile for standard testing conditions (M=0.25 and T=1183°C)

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Figure 3

Fixture designed to allow impingement cooling of turbine blade sample

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Figure 4

Measured front side and back side temperatures as a function of cooling

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Figure 5

Coal particle size distribution for four sizes tested

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Figure 6

ESEM images of smallest (top) and largest (bottom) size coal particles

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Figure 7

Post-test images of coupon subjected to 13μm particle size

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Figure 8

Micrograph image taken of turbine blade pressure surface deposits (flow direction is bottom to top)

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Figure 9

Effect of particle size on net capture efficiency

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Figure 10

Effect of gas temperature on net capture efficiency

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Figure 11

Digital images of postburn coupons at (from left to right) 1183°C, 1074°C, and 966°C

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Figure 12

Effect of gas temperature on deposit roughness

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Figure 13

Effect of cooling on net capture efficiency

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Figure 14

Remaining deposit thickness versus cooling level

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Figure 15

Typical image series of bottom (left), middle, and top (right) portions of 5.81g∕s coolant test sample

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Figure 16

Effect of cooling on deposit surface roughness

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Figure 17

Elemental comparison of ash, deposit, and penetration for coal impingement cooling series




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