1. Uncertainties in the Measurement of Convective Heat Transfer Co-efficient for internal cooling passages using Infrared Thermography in Gas Turbine Engines
Presenters : Sowmya Raghu, Christopher Axten
Faculty Advisor: Dr. Cengiz Camci
The Pennsylvania State University, University Park
AIAA Student Conference Region I, April 23,2016, Worcester Polytechnic Institute (WPI)

2. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

3. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

4. Introduction
Increasing the efficiency of the gas turbine engine by operating at the highest possible turbine inlet temperature.
Problem : Designing turbine blades for the high thermal stresses due to very high combustor exit temperature. (1700°- 2400°C)
Solution : Cooling using different pin fin geometries within the blades vary the convective heat transfer while minimizing the resultant pressure losses
End goal
Nickel Alloys
Fuel burn- avgas
Requirement of cooling

5. Applications and Advantages of IR Imaging
Infrared Imaging to analyze
Impinging jets
Airfoil transition/separation
Rotating surfaces
180°-turn channels and ribs
Hypersonic flows
Advantages
Non-intrusive
Has a high sensitivity (down to 20 mK)
Has a low response time (down to 20 μ s)
The camera is fully two-dimensional
Heating flow in a channel with symmetric ribs

6. Analysis Methodology Experimental Procedure
Infrared Imaging – FLIR T620
Low – Speed Wind tunnel
Image Analysis
FLIR Quick Report –v1.2
Experimental Corrections of emissivity
Results
Heat transfer co-efficient
Adiabatic Wall Temperature
Reynolds number and Velocity
Emissivity and Transmissivity corrections
Along the line and box

7. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

8. Measurement of Heat Transfer Co-efficient
DC Voltage Supply as Heating Source
Minco Thermofoil Heater
Applied Voltage :0-75 V
Temperature Operating Range : 32F – 150F
Conduction Loss through the back plate
Negligible radiation losses

9. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

10. Experimental Set- Up Overview

11. Characterization of the Wind Tunnel and Thermocouple Locations
Purpose
On the Heating Filament
Calibration of the IR Window
Back Wall
Measurement of Conduction Losses
Flow Field
Temperature in the flow
Ambient Temp.
For computation of Taw

12. Infrared Camera – FLIR T 620

13. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

14. IR Images of the Heated Wall without/with IR Window

15. Temperature Comparison at different Power Setting
55 V at 30 m/s
65 V at 30 m/s

16. HTC Measurement Profiles

17. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

18. Calibration of the IR Window
Calibration for the angle of viewing
9 point matrix
To compute for variations due to shading effects
Emissivity and transmissivity Correction
Choice of value for IR material and Plexi glass
Matching the temperature on IR camera with Thermocouple
Corrections for reflections and Temperature range setting
Elimination of possible Reflective surfaces from FOV
Appropriate Temperature range Set – F

19. Calibration of the IR Window based on thermocouple
Location of thermocouple

20. Heat Flux Measurement at different Velocities

21. HTC ‘h’ Measurements at different velocities
Velocity = 30m/s
Voltage (V)
Conduction Loss % h
h(no loss)
Taw
Taw (no Loss) 65
-0.05
195.22
195.13
321.60
323.17 55
-0.17
174.99
174.69
316.61
318.27
Velocity = 20m/s
(no
Loss)
0.32
160.44
160.96
326.10
327.56
-0.20
151.29
150.98
321.00
322.59

22. HTC ‘h’ Measurements around the Thermocouple Location

23. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

24. Uncertainty Derivation

25. Uncertainty Derivation

26. Uncertainty Derivation

27. Sample Uncertainty Calculation
Terms of Uncertainty
Assigned Variable
Baseline Experiment Value
Estimated Differential Measurement Value
Voltage 𝑉
65.0𝑉
±0.1𝑉
Resistance 𝑅
17.6𝛺
±0.1𝛺
Heater Area
𝐴 ℎ
𝑚 2
±1∗ 10 −6 𝑚 2
Conduction Heat Flux
𝑞 𝑐𝑜𝑛𝑑
8.3 𝑊 𝑚 2
±0.1 𝑊 𝑚 2
Infrared Temperature
𝑇 𝐼𝑅
317.4𝐾
±0.2𝐾
Adiabatic Wall Temperature
𝑇 𝑎𝑤
304.0𝐾
20m/s and 65V
Produced a baseline uncertainty of 1.71%

28. Experimental Uncertainty
Uncertainty decreases with increasing voltage
Uncertainty decreases with decreasing tunnel velocity
Calculations are only an estimate of the measurement devices accuracies
Uncertainties more likely in the 5-10% range

29. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

30. Conclusions
Infrared thermography provides quality temperature measurements, even with a flow
Infrared thermography can be used to determine convective heat transfer characteristics
Higher heat fluxes and lower velocities provide lower experimental uncertainties
This calibration would form the basis for the study of convective heat transfer using pin fins

31. Outline Introduction Convective Heat Transfer Study
Experimental Set-up
Infrared Thermography
Image Processing and heat transfer co-efficient measurement
Uncertainty Analysis
Conclusion
Future Studies

32. Future Studies
Analyze the convective heat transfer characteristics of different geometries
Compare to computational and analytical methods
Design new pin fin geometries based on convective heat transfer and pressure losses

33. Thank You !

34. Acknowledgements
We would like to thank our advisor Dr. Cengiz Camci, for giving us the opportunity to work with him and for his guidance during this study.
We also thank all the Dr. Jason Town and Veerendra for their help during the initial stages of the project.

35. References
[1] Meola C. and CARLOMAGNO G.M., “Recent Advances in the Use of Infrared Thermography,” Measurement Science and Technology, Vol. 15, No. 1, Jul. 23, 2004, pp
[2] Carlomagno, G.M., “Some Thermographic Measurements in Complex Fluid Flows,”. Journal of Flow Visualization & Image Processing, Vol. 17, No. 1, 2010, pp
[3] Uzol, O., “Novel Concepts and Geometries as Alternatives to Conventional Circular Pin Fins For Gas Turbine Blade Cooling Applications,” Ph.D. Dissertation, Aerospace Engineering Dept., The Pennsylvania State University., University Park, PA, 2000.
[4] Özgür Gökçe, Z., “Endwall Shape Modification Using Vortex Generators and Fences to Improve Gas Turbine Cooling and Effectiveness,” Ph.D. Dissertation, Aerospace Engineering Dept., The Pennsylvania State University., University Park, PA, 2012.
[5] “10 Things You Need To Know About Infrared Windows,” IRISS, inc., URL: [cited 4 March 2016].