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Research Papers

A Detailed Uncertainty Analysis of Adiabatic Film Cooling Effectiveness Measurements Using Pressure-Sensitive Paint

[+] Author and Article Information
Greg Natsui

Department of Mechanical
and Aerospace Engineering,
University of Central Florida,
Orlando, FL 32816
e-mail: gnatsui@knights.ucf.edu

Zachary Little

Department of Mechanical
and Aerospace Engineering,
University of Central Florida,
Orlando, FL 32816
e-mail: Zachary.Little@ucf.edu

Jayanta S. Kapat

Department of Mechanical and Aerospace
Engineering,
University of Central Florida,
Orlando, FL 32816
e-mail: Jayanta.Kapat@ucf.edu

Jason E. Dees

GE Global Research,
Niskayuna, NY 12309
e-mail: DeesJ@ge.com

Gregory Laskowski

GE Aviation,
Lynn, MA 01905
e-mail: Laskowsk@ge.com

Contributed by the International Gas Turbine Institute (IGTI) of ASME for publication in the JOURNAL OF TURBOMACHINERY. Manuscript received January 12, 2016; final manuscript received January 27, 2016; published online March 30, 2016. Editor: Kenneth C. Hall.

J. Turbomach 138(8), 081007 (Mar 30, 2016) (12 pages) Paper No: TURBO-16-1011; doi: 10.1115/1.4032674 History: Received January 12, 2016; Revised January 27, 2016

Pressure-sensitive paint (PSP) can be a powerful tool in measuring the adiabatic film cooling effectiveness. There are two distinct sources of error for this measurement technique: the ability to experimentally obtain the data and the validity of the heat and mass transfer analogy for the problem being studied. This paper will assess the experimental aspect of this PSP measurement specifically for film cooling applications. Experiments are conducted in an effort to quantifiably bound expected errors associated with temperature nonuniformities in testing and photodegradation effects. Results show that if careful experimental procedures are put in place, both of these effects can be maintained to have less than 0.022 impact on effectiveness. Through accurate semi in situ calibration down to 4% atmospheric pressure, the near-hole distribution of effectiveness is measured with high accuracy. PSP calibrations are performed for multiple coupons, over multiple days. In addition, to reach a partial pressure of zero the calibration vessel was purged of all air by flowing CO2. The primary contribution of this paper lies in the uncertainty analysis performed on the PSP measurement technique. A thorough uncertainty analysis is conducted and described, in order to completely understand the presented measurements and any shortcomings of the PSP technique. This quantification results in larger, albeit more realistic, values of uncertainty and helps provide a better understanding of film cooling effectiveness measurements taken using the PSP technique. The presented uncertainty analysis takes into account all random error sources associated with sampling and calibration, from intensities to effectiveness. Adiabatic film cooling effectiveness measurements are obtained for a single row of film cooling holes inclined at 20 deg, with CO2 used as coolant. Data are obtained for six blowing ratios. Maps of uncertainty corresponding to each effectiveness profile are available for each test case. These maps show that the uncertainty varies spatially over the test surface and high effectiveness corresponds to low uncertainty. The noise floors can be as high as 0.04 at effectiveness levels of 0. Day-to-day repeatability is presented for each blowing ratio and shows that laterally averaged effectiveness data are repeatable within 0.02 effectiveness.

Copyright © 2016 by ASME
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References

Figures

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Fig. 1

Relation between pressure ratio and adiabatic film cooling effectiveness for different molecular weight ratios (MW = 1.5192 corresponds to injection of pure CO2)

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Fig. 2

Convergence of the mean for a series of images, each series represents a pixel

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Fig. 3

N = 87, calibrations from three surfaces over 3 days to 6 runs total, up and down calibrations

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Fig. 4

PSP calibrations at different temperatures

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Fig. 5

The collapse of the T dependence, α = 2.492

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Fig. 6

Film effectiveness uncertainty, uη, as a function of temperature shift and η

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Fig. 7

Temporal variation of PSP with constant excitation while maintaining operating conditions (STP)

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Fig. 8

Uncertainty in effectiveness as a function of effectiveness for a fixed value of uncertainty in PR (uPR = 0.03 in this example)

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Fig. 9

Model of wind tunnel

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Fig. 10

Typical static pressures of the tunnel while the wind tunnel is running

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Fig. 11

Spatially resolved adiabatic film cooling effectiveness profiles of near-hole performance following a single row for M = 0.3–1.2

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Fig. 18

Diagram of sources of error for film cooling effectiveness calculation

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Fig. 19

Maps of uncertainty, calculated according to Ref. [12], for M = 0.3 and 1.2

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Fig. 20

Day-to-day lateral average repeatability, M = 0.3

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Fig. 21

Day-to-day lateral average repeatability, M = 0.5

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Fig. 22

Day-to-day lateral average repeatability, M = 0.6

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Fig. 23

Day-to-day lateral average repeatability, M = 0.8

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Fig. 24

Day-to-day lateral average repeatability, M = 0.9

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Fig. 25

Day-to-day lateral average repeatability, M = 1.2

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Fig. 26

Day-to-day repeatability of centerline results, M = 0.3

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Fig. 27

Lateral uniformity of centerline results, M = 0.3

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Fig. 28

Centerline effectiveness for different blowing ratios

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Fig. 29

Validation of PSP results with other experimental results downstream of a range of different inclination angle geometries. Other results are scaled by pitch to the current pitch of 7.5d.

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