Three-Dimensional Aero-Thermal Optimization of Film Cooling in a High Pressure Turbine Carole ...

226 Pages·2014·5.82 MB·English

Three-Dimensional Aero-Thermal Optimization of Film Cooling in a High Pressure Turbine

Carole El Ayoubi

A Thesis
In the Department of
Mechanical and Industrial Engineering

Presented in Partial Fulfillment of the Requirements
For the Degree of
Doctor of Philosophy
Concordia University
Montreal, Quebec, Canada

May 2014
© Carole El Ayoubi, 2014
CONCORDIA UNIVERSITY

School of Graduate Studies
This is to certify that the thesis prepared
By: Carole El Ayoubi
Entitled: Three-Dimensional Aero-Thermal Optimization of Film Cooling in a High
Pressure Turbine
and submitted in partial fulfilment of the requirements for the degree of
Doctorate of Philosophy
complies with the regulations of the University and meets the accepted standards with respect to
originality and quality.
Signed by the final examining committee:
_________________________________ Dr. Fariborz Haghighat (Chair)
_________________________________ Dr. Marius Paraschivoiu (Examiner)
_________________________________ Dr. Nabil Esmail (Examiner)
_________________________________ Dr. Christopher Trueman (Examiner)
_________________________________ Dr. Jean-Yves Trepanier (Examiner)
_________________________________ Dr. Wahid S. Ghaly (Supervisor)
_________________________________ Dr. Ibrahim G. Hassan (Supervisor)
Approved by ____________________________________________________
MIE Department Chair or Graduate Program Director
________2014 __________________________________________________
Dean, Faculty of Engineering and Computer Science
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ABSTRACT

Three Dimensional Aero-Thermal Optimization of Film Cooling in a High Pressure
Turbine

Carole El Ayoubi, Ph.D.
Concordia University, 2014

Development of effective discrete film cooling is recognized as an essential task in gas turbine
design since it has been shown necessary to ensure an acceptable turbine component life-time.
Traditional design of film cooling schemes is driven by a single objective, maximizing the
cooling performance. The aerodynamic penalty resulting from the coolant injection is generally
neglected. Achieving an aero-thermal design of film cooling is a challenging task as it is based
on two competing objectives; attaining a high thermal protection of the airfoil from the hot
mainstream gas usually results in deteriorating the aerodynamic efficiency.
The present research addresses this challenge and investigates the complex flow underlying the
aero-thermal interaction on a film cooled airfoil. The simultaneous effects of film coolant flow
parameters and film hole geometric variables on the aerodynamic loss and the cooling
effectiveness are examined. Trends in design variations to minimize the aerodynamic penalty,
while maintaining a high cooling performance are established.
The research objective is achieved by implementing an automated optimization procedure that
consists of a non-dominated sorting genetic algorithm coupled with an artificial neural network.
The latter is used to provide prediction of the objective function at every optimization iteration
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and reduces computation time. It is constructed based on numerical flow simulations where the
three dimensional Reynolds-Averaged Navier-Stokes equations are solved.
The optimization methodology is applied on a typical high-pressure turbine with two staggered
rows of discrete film cooling on the suction side. The Pareto front of optimal solutions is
generated. The thermal, aero-thermal, and aerodynamic optimums are identified and investigated
numerically. A subsonic wind-tunnel facility available in Concordia University is used to re-
create experimentally the optimum design points. Measured experimental data allowed
verification of the CFD model, and substantiated the optimization methodology as a reliable
design tool for film cooling in turbomachinery applications.
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ACKNOWLEDGMENTS

I would like to thank my supervisors Dr. Ibrahim Hassan and Dr. Wahid Ghaly for the
opportunity they have given me to conduct research under their supervision at Concordia
University. They have both provided me with great guidance and insight that was invaluable to
the completion of this work.
I would also like to thank my colleagues, especially Dr. Othman Hassan who has given support
with experimental manipulations and has always been generous with advice. I would also like to
thank Haoming Li whose experience with CFD software was valuable. Many thanks go to Amen
Younes, Fan Yan Feng, Kristina Cook, Yingjie Zheng, and Qian You for always providing
support and advice. Big thanks go to Hamza Assi for his solid technical support with engineering
drawings, his work is greatly appreciated.
Finally, this work is dedicated to my family whose unconditional love and support has carried
me through this journey.

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Table of Contents
List of Figures .............................................................................................................................x
List of Tables ............................................................................................................................ xv
List of Acronyms .....................................................................................................................xvi
Introduction ................................................................................................................................1
1. Literature Review.................................................................................................................6
1.1. Review of film cooling hole technology ........................................................................6
1.1.1. Summary ............................................................................................................. 13
1.2. Numerical modeling of film cooling ............................................................................ 14
1.2.1. The computational domain and grid ..................................................................... 16
1.2.2. Turbulence modeling and cooling effectiveness prediction ................................... 19
1.2.3. Summary ............................................................................................................. 26
1.3. Effect of film cooling on aerodynamic loss ................................................................. 28
1.3.1. Summary ............................................................................................................. 31
1.4. Numerical optimization ............................................................................................... 32
1.4.1. Aerodynamic shape optimization ......................................................................... 32
1.4.2. Film cooling optimization .................................................................................... 35
1.4.3. Summary ............................................................................................................. 38
1.5. Motivations and objectives of the present work ........................................................... 39
2. Numerical Methodology .................................................................................................... 43
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2.1. Governing equations ................................................................................................... 43
2.2. Turbulence modeling .................................................................................................. 44
2.3. Wall Treatment ........................................................................................................... 50
2.4. Heat Transfer Calculations in CFX.............................................................................. 53
2.5. Genetic Algorithm ...................................................................................................... 55
2.5.1. Selection .............................................................................................................. 55
2.5.2. Crossover ............................................................................................................. 56
2.5.3. Mutation .............................................................................................................. 56
2.5.4. Elitism and convergence ...................................................................................... 57
2.6. Artificial neural network ............................................................................................. 57
2.7. Optimization algorithm ............................................................................................... 60
2.8. Optimization objectives and design variables .............................................................. 63
2.9. Uncertainty calculations .............................................................................................. 66
3. Film Cooling Optimization on the VKI Blade Suction Surface ........................................... 68
3.1. Heat transfer to the non-cooled VKI blade .................................................................. 68
3.1.1. CFD model .......................................................................................................... 69
3.1.2. CFD predictions ................................................................................................... 71
3.2. Heat transfer to the film cooled VKI blade .................................................................. 77
3.2.1. CFD model .......................................................................................................... 77
3.2.2. CFD predictions ................................................................................................... 79
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3.3. Film cooling optimization for the VKI blade ............................................................... 86
3.3.1. Single objective optimization results .................................................................... 86
3.3.2. Multiple objective optimization results ............................................................... 102
3.4. Conclusion ................................................................................................................ 103
4. Experimental Verification of the Film Cooling Optimization on a Vane Suction Surface.. 106
4.1. Experimental methodology ....................................................................................... 107
4.1.1. Mechanical system ............................................................................................. 108
4.1.2. Thermography system ........................................................................................ 108
4.1.3. Electronic system ............................................................................................... 109
4.1.4. Test section ........................................................................................................ 109
4.1.5. TLC calibration .................................................................................................. 110
4.1.6. Data reduction.................................................................................................... 111
4.1.7. Test facility validation ....................................................................................... 112
4.2. CFD model ............................................................................................................... 114
4.3. Multiple objective optimization on the vane suction side ........................................... 135
4.4. Single objective optimization on the vane suction side .............................................. 139
4.5. Conclusion ................................................................................................................ 156
5. Film Cooling Shape Optimization on a Vane Suction Surface .......................................... 158
5.1. CFD model ............................................................................................................... 158
5.2. Multiple objective shape optimization of film cooling on the vane side ..................... 159
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5.3. Single objective shape optimization of film cooling on the vane suction side ............ 163
5.4. Discrete film cooling aero-thermal design guidelines ................................................ 184
5.5. Conclusion ................................................................................................................ 189
6. Conclusion ....................................................................................................................... 191
6.1. Summary of the present findings ............................................................................... 191
6.2. Validity of the optimization results............................................................................ 193
6.3. Contributions of the present research and future work ............................................... 195
Bibliography ........................................................................................................................... 198

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List of Figures
Figure 1-1: The cylindrical hole and the geometric variations of a shaped cooling hole; Bunker
(2005) .........................................................................................................................................7
Figure 2-1: Schematic of an artificial neuron ............................................................................. 62
Figure 2-2: Flowchart of the optimization algorithm.................................................................. 62
Figure 3-1: The 3D CFD domain of the non-cooled VKI blade.................................................. 74
Figure 3-2: 2D profile of the CFD domain of the non-cooled VKI blade ................................... 74
Figure 3-3: Isentropic Mach number distribution at the mid-span of the VKI blade ................... 75
Figure 3-4: Surface heat transfer coefficient distribution at the mid-span of the non-cooled VKI
blade ......................................................................................................................................... 76
Figure 3-5: 2D profile of the CFD domain of the film-cooled VKI blade ................................... 82
Figure 3-6: 2D details of the cooling hole configuration on the VKI blade suction surface ........ 82
Figure 3-7: Details of the computational grid around the cooled VKI blade ............................... 83
Figure 3-8: Details of the computational grid inside the coolant plenum and at the blade wall ... 83
Figure 3-9: Sensitivity of the laterally averaged wall heat transfer coefficient distribution to
turbulence modeling at BR = 0.43 ............................................................................................. 84
Figure 3-10: Sensitivity of the laterally averaged wall heat transfer coefficient distribution to
mesh refinement at BR = 0.43 ................................................................................................... 85
Figure 3-11: Evolution of ANN training and testing RMS errors ............................................... 94
Figure 3-12: Evolution of F , η , and AL with database enrichment cycles ............................ 95
obj surf
Figure 3-13: Effect of database enrichment cycles on the ANN accuracy .................................. 95
Figure 3-14: Sensitivity of the CFD predictions of AL, η , and F to the design variables ...... 96
surf obj
x