Simulated Land-Based Turbine Deposits Generated in an Accelerated Deposition Facility

[+] Author and Article Information
Jared W. Jensen

 Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602jwj5@email.byu.edu

Sean W. Squire

 Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602sws25@et.byu.edu

Jeffrey P. Bons

 Department of Mechanical Engineering, Brigham Young University, Provo, UT 84602jbons@byu.edu

Thomas H. Fletcher

 Department of Chemical Engineering, Brigham Young University, Provo, UT 84602tom̱fletcher@byu.edu

J. Turbomach 127(3), 462-470 (Mar 01, 2004) (9 pages) doi:10.1115/1.1860380 History: Received October 01, 2003; Revised March 01, 2004

This report presents a validation of the design and operation of an accelerated testing facility for the study of foreign deposit layers typical to the operation of land-based gas turbines. This facility was designed to produce turbine deposits in a 4-h test that would simulate 10000h of turbine operation. This is accomplished by matching the net foreign particulate throughput of an actual gas turbine. Flow Mach number, temperature and particulate impingement angle are also matched. Validation tests were conducted to model the ingestion of foreign particulate typically found in the urban environment. The majority of this particulate is ceramic in nature and smaller than 10microns in size, but varies up to 80microns. Deposits were formed for flow Mach number and temperature of 0.34 and 1150°C, respectively, using MCrAlY coated coupons donated from industry. Investigations over a range of impingement angles yielded samples with deposit thicknesses from 10to50microns in 4h, accelerated-service simulations. Deposit thickness increased substantially with temperature and was roughly constant with impingement angle when the deposit thickness was measured in the direction of the impinging flow. Test validation was achieved using direct comparison with deposits from service hardware. Deposit characteristics affecting blade heat transfer via convection and conduction were assessed. Surface topography analysis indicated that the surface structure of the generated deposits were similar to those found on actual turbine blades. Scanning electron microscope (SEM) and x-ray spectroscopy analyses indicated that the deposit microstructures and chemical compositions were comparable to turbine blade deposit samples obtained from industry.

Copyright © 2005 by American Society of Mechanical Engineers
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Figure 1

Accelerated deposition test facility

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Figure 2

Cut-away of target area (TC1 and TC2 show flow thermocouple placement)

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Figure 3

Seed particle size distribution by mass

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Figure 4

Surface map of deposits from (a) first stage turbine with 25000h and (b) accelerated deposit surface after 4h at 52ppmw. Both maps are 4mm×4mm with approximately the same vertical scale.

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Figure 5

23mm long average surface trace across accelerated deposit test coupon. Vertical scale (units are microns) exaggerated for clarity. 1mm on either end of trace is unexposed surface with no deposits.

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Figure 8

Normalized deposit thickness as a function of impingement angle for 4 accelerated tests. Open symbols denote deposit thickness in flow direction.

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Figure 6

SEM cross section of (a) a 16000h service blade with 50-μm metering bar at top left and (b) an accelerated deposit specimen with 100-μm metering bar at top left

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Figure 7

SEM cross section of (a) 25000-h service blade with 10-μm metering bar and (b) an accelerated sample with 30-μm metering bar



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