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)

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

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

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

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

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

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

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

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

Experimental Set- Up Overview

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

Infrared Camera – FLIR T 620  

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

IR Images of the Heated Wall without/with IR Window

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

HTC Measurement Profiles

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

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 – 32-150F

Calibration of the IR Window based on thermocouple Location of thermocouple

Heat Flux Measurement at different Velocities

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

HTC ‘h’ Measurements around the Thermocouple Location

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

Uncertainty Derivation  

Uncertainty Derivation  

Uncertainty Derivation  

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 0.09375 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%

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

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

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

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

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

Thank You !

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.

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. 27-58. [2] Carlomagno, G.M., “Some Thermographic Measurements in Complex Fluid Flows,”. Journal of Flow Visualization & Image Processing, Vol. 17, No. 1, 2010, pp. 15-40. [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: http://www.datacentir.com/downloads/files/10_Things_You_Need_to_Know_About_Infrared_Windows.pdf [cited 4 March 2016].