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Impingement Jet Cooling in Gas Turbines

International Series on Developments in Heat Transfer

Objectives

The Developments in Heat Transfer book Series publishes state-of-the-art books and provides valuable contributions to the literature in the field of heat transfer, thermal and energy engineering. The overall aim of the Series is to bring to the attention of the international community recent advances in thermal sciences by authors in academic research and the engineering industry. Research and development in heat transfer is of significant importance to many branches of technology, not least in energy technology. Developments include new, efficient heat exchangers, novel heat transfer equipment as well as the introduction of systems of heat exchangers in industrial processes. Application areas include heat recovery in the chemical and process industries, and buildings and dwelling houses where heat transfer plays a major role. Heat exchange combined with heat storage is also a methodology for improving the energy efficiency in industry, while cooling in gas turbine systems and combustion engines is another important area of heat transfer research. Emerging technologies like fuel cells and batteries also involve significant heat transfer issues. To progress developments within the field both basic and applied research is needed. Advances in numerical solution methods of partial differential equations, turbulence modelling, high-speed, efficient and cheap computers, advanced experimental methods using LDV (laser-doppler-velocimetry), PIV (particle-image-velocimetry) and image processing of thermal pictures of liquid crystals, have all led to dramatic advances during recent years in the solution and investigation of complex problems within the field. The aims of the Series are achieved by contributions to the volumes from invited authors only. This is backed by an internationally recognised Editorial Board for the Series who represent much of the active research worldwide. Volumes planned for the series include the following topics: Compact Heat Exchangers, Engineering Heat Transfer Phenomena, Fins and Fin Systems, Condensation, Materials Processing, Gas Turbine Cooling, Electronics Cooling, Combustion-Related Heat Transfer, Heat Transfer in Gas-Solid Flows, Thermal Radiation, the Boundary Element Method in Heat Transfer, Phase Change Problems, Heat Transfer in Micro-Devices, Plate-and-Frame Heat Exchangers, Turbulent Convective Heat Transfer in Ducts, Enhancement of Heat Transfer, Transport Phenomena in Fires, Fuel Cells and Batteries as well as Thermal Issues in Future Vehicles and other selected topics.

Series EditorB. Sundén

Lund UniversityPO Box 118

SE-22100 LundSweden

Associate Editors

R. AmanoUniversity of Wisconsin, USA

C.A. BrebbiaWessex Institute of Technology, UK

G. CominiUniversity of Udine, Italy

R.M. CottaCOPPE/UFRJ, Brazil

S.K. DasIndia Institute of Technology, Madras, India

L. De BiaseUniversity of Milan, Italy

G. De MeyUniversity of Ghent, Belgium

S. del GuidiceUniversity of Udine, Italy

M. FaghriUniversity of Rhode Island, USA

C. Herman John Hopkins University, USA

Y. JaluriaRutgers University, USA

S. KabelacHelmut Schmidt University, Hamburg, Germany

D.B. MurrayTrinity College Dublin, Ireland

P.H. OosthuizenQueen’s University Kingston, Canada

P. PoskasLithuanian Energy Institute, Lithuania

B. SarlerNova Gorica Polytechnic, Slovenia

A.C.M. SousaUniversity of New Brunswick, Canada

D.B. SpaldingCHAM, UK

J. SzmydUniversity of Mining and Metallurgy, Poland

D. TaftiViginia Tech., USA

Q. WangXi’an Jiatong University, China

S. YanniotisAgricultural University of Athens, Greece

Impingement Jet Cooling in Gas Turbines

Editors

Ryoichi S. AmanoUniversity of Wisconsin-Milwaukee, USA

&Bengt Sundén

Lund University, Sweden

Published by

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Tel: 978 667 5841; Fax: 978 667 7582E-Mail: infousa@witpress.com

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British Library Cataloguing-in-Publication DataA Catalogue record for this book is available

from the British Library

ISBN: 978-1-84564-906-7eISBN: 978-1-84564-907-4

Library of Congress Catalog Card Number: 2014934346

No responsibility is assumed by the Publisher, the Editors and Authors for any injury and/or damage to persons or property as a matter of products liability,

negligence or otherwise, or from any use or operation of any methods, products, instructions or ideas contained in the material herein. The Publisher does not

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© WIT Press 2014

Printed by Lightning Source, UK.

All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written

permission of the Publisher.

Editors:

Ryoichi S. AmanoUniversity of Wisconsin-Milwaukee, USA

&

Bengt SundénLund University, Sweden

Preface

This book focuses on impingement jet cooling on gas turbine blades. The topic ranges fundamental to application of impingement jet usage for actual gas turbine blades.

The first chapter presents the basics of gas turbine impingement cooling design, the various applications within the engine, and the typical limitations imposed upon its use. Generic use and application examples for single impingement jets, in-line rows of jets, and arrays of jets are described for the hot gas flow path components of gas turbines, including the combustor system and high pressure turbine. Specific applications to airfoil aerodynamic leading and trailing edge regions, combustor liners, and rotating disks are provided, as well as emerging applications within confined channels, blade tips, and film cooling.

The second chapter deals with the experimental and numerical investigation of an impingement chamber and flow analysis for both single exit and double-exit cases. The chapter shows the dependency of local Nusselt number on the jet Reynolds number to the power of 0.78 for a Reynolds number higher than 12,000, which confirms the Reynolds number dependency for turbulent stagnation and boundary layer flows in higher ranges of the Reynolds number. The deviation of the dependence curve for a Re less than 8,000 indicated that the flow is partially mixed with a transitional turbulence condition with these Reynolds number ranges. This discovery proves useful information for the selection of the turbulence models for these heat transfer computations. The results provide useful suggestions to the gas turbine cooling technology developments.

For the single exit cases, it has been shown both experimentally and computationally that a minor reduction in the Nusselt number occurs on the even rows of the jets. This phenomenon was clarified through the extensive computational investigation that the reduction of the heat transfer was attributed to the vortex motion generated both by the surrounding jets and the side wall effects.

The third chapter presents recent development on impinging jet arrays with effects of Mach number, Reynolds number, temperature ratio, hole spacing, and jet-to-target plate distance. The experimentally obtained data cover wide-range range of those parameters. The materials presented are quite useful for understanding the effects of the factors that significantly enhance the heat transfer effectiveness, and therefore provide insight to engineers and academic community.

The fourth chapter describes an impingement application for combustor linear backside cooling technology. Jet impingement cooling is significant in gas turbine systems for cooling hot gas path components, primarily in vanes and combustor liners. In modern low NOx gas turbine combustors, cooling of the combustor liner is achieved from the backside through innovative enhanced heat transfer augmentation methods. In this chapter, an overview of jet impingement related heat transfer research and design background is presented. Additionally, some specific studies that focus on innovative cooling methods for combustor liners are presented with highlighted results. Additional comments on possible future research directions and topics under consideration are presented.

The fifth chapter focuses mainly on a combined cooling technique of impingement/effusion cooling; and with this arrangement it can be controlled by a number of factors, including the hole pattern, angle of the effusion holes, target surface configuration, and gap spacing. The classification of the principal variables affecting cooling performance are explained as well as how heat transfer and fluidic characteristics can be controlled by each variable based on thermo-physical aspects. In addition, various applied techniques involving surface modifications, such as curved surfaces and combined rib and pin-fin structures, are discussed in this chapter. The effects of the impingement/effusion cooling systems are reviewed, and a detailed account on experimental approaches as well as numerical analyses regarding heat and mass transfer are presented. The development process for an impingement/effusion cooling system is described, together with suggested directions for further advances in this field.

The sixth chapter presents flow control of impingement jets and wall jets. The main topic of this chapter is to provide useful information on the flow control technology of impingement jets in gas turbines and to discuss recent trends in the passive and active flow control of impingement jets based on recent advancements. The temperature level in a gas turbine field is so high that innovative developments in material and cooling technology are needed for usage in the hot sections. Therefore, innovative cooling systems will be employed in the future. Smart actuators for flow control of the jet impingement, which can be used under severe temperature and pressure conditions, will also be provided based on the progress in related technologies.

The seventh chapter presents a brief review of studies on swirling and non-

swirling impinging jets. Also a numerical investigation of heat transfer from impinging swirling jets is described. Various turbulence models are used. Comparison with experimental data is provided. Generally the V2f model was found to perform better than other models but for small nozzle to plate distances it was hard to maintain good or sufficient accuracy. The difference in performance, in terms of the Nusselt number distribution on the impingement wall, between swirling and non-swirling impinging jets was clearly identified. The magnitude of the swirling motion has great influence on the flow field and the formation of recirculating zones and accordingly the heat transfer process

The eighth chapter presents Impingement jet cooling heat transfer with a two-dimensional and a circular nozzle enhanced by a rib. This chapter presents the effect of a rib on heat transfer enhancement in the wall jet region of impinging jet by employing mass transfer experiments using a naphthalene sublimation technique and numerical simulations by RANS and LES. By comparing the computational results obtained through various models, the authors recommend LES for its superiority in its effectiveness in predicting Nusselt number in downstream region of the channel.

All of the chapters follow a unified outline and presentation to aid accessibility and the book provides invaluable information to university professors, graduate researchers, and industrial research engineers/scientists.

We are grateful to the authors and reviewers for their excellent contributions. We also thank ceaseless help that were provided by the staff members of WIT Press, in particular Mrs. Elizabeth Cherry, for their strong encouragement in the production of this book. Finally our appreciation goes to Professor Carlos Brebbia who gave us strong support and encouragement to complete this project.

Ryoichi S. Amano and Bengt Sundén

About the Editors

Professor Ryoichi Amano is an internationally recognized scientist in thermal engineering, experimental fluid dynamics, turbulence research, and energy systems. For a number of years he has been engaged in research related to gas turbine performance, rotating machinery, power engineering, transport phenomena, heat/mass transfer, two-phase flow, and manufacturing material processes. Dr Amano has also contributed to the development of turbulence theories, jets, combustion, heat transfer, propulsion, aerodynamics, and applications to gas turbine and aerospace-related projects. In addition, he has engaged in gas turbine flow analyses of NASA space shuttle main engines and solid rocket motor research of US Air Force Research Labs, industrial gas turbines, steam turbines, and cooling technology using impinging gas jets.

Dr Amano has more than 500 publications, including books, refereed journal papers, invited review chapters, and conference proceedings. He has conducted numerous experimental and analytical research projects with extramural funding from US governmental agencies and many industries. Dr Amano is a technical committee member, editorial board member and international advisory committee member for ASME, AIAA, WIT Conferences, ISETS conferences (Japan) and an executive member of ASME International Gas Turbine Institute, AIAA Terrestrial Energy System, and ASME Energy Systems Committee. In addition, Dr Amano has received three Best Paper awards from ASME, the Sustained Service Award from AIAA, the AIAA Energy Systems Award, a UWM Excellence of Research Award. He is a Fellow of ASME and Associate Fellow of AIAA.

Professor Bengt Sundén received his MSc in 1973, PhD in thermodynamics and fluid mechanics in 1979, and Docent in applied thermodynamics and fluid mechanics in 1980, all from Chalmers University of Technology, Goteborg, Sweden. He became Professor of Heat Transfer in 1992 at Lund University. Since 1995 he serves as the head of the Department of Energy Sciences, Lund University, Sweden, and is also a guest professor at Northwestern Polytechnical University, Xi’an, China, and an honorary professor at Xi’an Jiatong University, Xi’an China.

His research topics include compact heat exchangers, enhancement of heat transfer, gas turbine heat transfer, combustion-related heat transfer including thermal radiation, CFD-methods for laminar and turbulent fluid flow and heat transfer, liquid crystal thermography, condensation and evaporation, nanofluids, transport phenomena in fuel cells, computational modeling and analysis of multiphysics and multiscale phenomena for fuel cells (SOFC, PEMFC).

Professor Sundén was the founding and first editor-in-chief of IJHEX (International Journal of Heat Exchangers), and was Associate Editor ASME Journal of Heat Transfer. In addition, he is currently an active editor for three journals. He is also editor-in-chief for a book series, Developments in Heat Transfer (also published by WIT Press), has published over 600 papers in journals, books and conference proceedings, and has supervised 170 MSc theses, 43 Licentiate of Engineering theses and 39 PhD theses. According to ISI knowledge Web of Science, the overall number of citations is 35 per year and the total number of citations is more than 2300. The h-index is 25.

He is a fellow of the ASME and a 2011 recipient of the ASME Heat Transfer Memorial Award, and a 2013 recipient of the ASME Heat Transfer Division 75th Anniversary Medal. He is a fellow of the Wessex Institute of Technology and a holder of the WIT Eminent Scientist Medal.

Contents

CHAPTER 1 Impingement Cooling in Gas Turbines: Design, Applications, and Limitations ................................................................................ 1 Ronald S. Bunker, Jason E. Dees & Pepe Palafox 1 Introduction ......................................................................................... 2 2 Applications ......................................................................................... 7

2.1 Single-jet impingement cooling ................................................ 7 2.2 Impingement from in-line jet rows ............................................ 8 2.3 Leading edge cooling ................................................................ 9 2.4 Trailing edge cooling ............................................................... 10 2.5 Surface jet array impingement ................................................. 11 2.6 Inner and outer flow path cooling ........................................... 12 2.7 Rotating disk impingement...................................................... 13 2.8 Impingement in rotating cooling passages .............................. 14 2.9 Confined channel impingement ............................................... 16 2.10 Impingement onto randomly rough and textured surfaces ...... 17 2.11 Blade tip internal cooling ........................................................ 18 2.12 Combustor cooling .................................................................. 20 2.13 Closed-circuit impingement cooling ....................................... 22 2.14 Impingement in film cooling ................................................... 23

3 Limitations ........................................................................................ 24 4 Summary ........................................................................................... 27 Nomenclature .......................................................................................... 28 References ............................................................................................... 28

CHAPTER 2 Impingement Jet Cooling with Different Stand-Off Distances for Single- and Double-Exit Flows ............................................................. 33 R.S. Amano, M. Keenan & S. Ou  1 Introduction ....................................................................................... 33 2 Cooling Jet Array .............................................................................. 34 3 Turbulence Models ............................................................................ 37

3.1 SST model ................................................................................ 37 3.2 V2F model ................................................................................ 38

4 Presentation and Discussion of Results ............................................. 38 4.1 Single-exit flow cases ............................................................... 38

4.1.1 Prediction using different turbulence models ................ 38 4.1.2 y+ distribution ............................................................... 38 4.1.3 Large eddy simulation (LES) ........................................ 40 4.1.4 V2F computations ......................................................... 43 4.1.5 Reynolds number effect ................................................. 50

4.2 Double-exit flow cases ............................................................. 50 4.2.1 Reynolds number dependence on heat transfer rate ...... 56

4.3 Non-circular holes .................................................................... 58 4.4 Staggered array ........................................................................ 58

5 Summary ........................................................................................... 59 Acknowledgements ................................................................................. 59 References ............................................................................................... 60

CHAPTER 3 Recent Developments in Impingement Array Cooling, Including Consideration of the Separate Effects of Mach Number, Reynolds Number, Temperature Ratio, Hole Spacing, and Jet-to-Target-Plate Distance .................................................................................................. 63 Phillip M. Ligrani 1 Introduction ....................................................................................... 64 2 Experimental Apparatus and Procedures .......................................... 67

2.1 Impingement flow facility and impingement array plates ........ 67 2.2 Discharge coefficient measurement and determination ............ 70 2.3 Local recovery factor measurement ......................................... 71 2.4 Local Nusselt number measurement ....................................... 71

3 Experimental Results and Discussion .............................................. 73 3.1 Crossflow mass velocity-to-jet mass velocity ratio and

discharge coefficients ............................................................... 74 3.2 Separate effects of Reynolds number and Mach number on

impingement array heat transfer ............................................... 75 3.2.1 Determination of spatially averaged adiabatic surface

temperature, Toj* ........................................................... 75 3.2.2 Nusselt number variations with Mach number and

Reynolds number .......................................................... 75 3.2.3 Comparisons of spatially averaged Nusselt numbers

with existing correlations, and a new correlation to account for Mach number effects ................................. 77

3.2.4 Recovery factor data ..................................................... 79 3.2.5 Nusselt number data corrected using local recovery

factors ............................................................................ 79 3.3 Effects of temperature ratio on impingement array

heat transfer .............................................................................. 82

3.3.1 Local surface Nusselt number variations with temperature ratio ........................................................... 82

3.3.2 Spatially averaged Nusselt number variations with temperature ratio ........................................................... 82

3.3.3 Spatially averaged Nusselt numbers and the temperature ratio correlation equation .......................... 85

3.4 Effects of hole spacing on impingement array heat transfer .................................................................................... 85 3.4.1 Line-averaged Nusselt numbers .................................... 87 3.4.2 Spatially averaged Nusselt numbers ............................. 89 3.4.3 Correlations to account for compressibility on

spatially averaged Nusselt numbers with different hole spacings ................................................................. 90

3.5 Effects of jet-to-target-plate distance on impingement array heat transfer ............................................................................. 92 3.5.1 Spatially resolved local Nusselt numbers ..................... 92 3.5.2 Spatially averaged Nusselt numbers ............................. 93

4 Summary and Conclusions ............................................................... 94 Acknowledgments ................................................................................... 96 Nomenclature .......................................................................................... 97 Greek symbols ......................................................................................... 98 References ............................................................................................... 98

CHAPTER 4 Impingement Cooling for Combustor Liner Backside Cooling ...... 103 Srinath V. Ekkad 1 Introduction .................................................................................... 103 2 Background .................................................................................... 104 3 Jet Impingement Cooling ............................................................... 106

3.1 Effect of initial crossflow ...................................................... 111 3.2 Impingement cooling for combustor liners ............................ 113

4 Conclusions ................................................................................... 122 References ............................................................................................. 123

CHAPTER 5 Impingement/Effusion Cooling Methods in Gas Turbine ................ 125 Hyung Hee Cho & Beom Seok Kim 1 Introduction ................................................................................... 126 2 Heat Transfer of Impingement/Effusion Cooling .......................... 128

2.1 Fundamentals of impingement/effusion cooling ................... 128 2.1.1 Basic concepts of impingement/effusion cooling ....... 128 2.1.2 Heat transfer characteristics of array jet impingement .............................................................. 128

2.2 Comparison of impingement jet and impingement/ effusion cooling .................................................................... 130

3 Major Variables for Impingement/Effusion Cooling ..................... 131 3.1 Effect of hole pattern and arrangement ................................. 131 3.2 Effect of plate spacing ........................................................... 135 3.3 Effect of Reynolds number ................................................... 136 3.4 Effect of surface curvature .................................................... 140 3.5 Effect of crossflow ................................................................ 143 3.6 Effect of surface modification ............................................... 146

3.6.1 Rib turbulators ........................................................... 147 3.6.2 Pin-fins ....................................................................... 149

References ............................................................................................. 153

CHAPTER 6 Flow Control of Impingement Jets and Wall Jets ............................ 157 S. Honami 1 Introduction to Flow Control of Impinging Jet .............................. 157 2 Passive Control of Jet Impingement .............................................. 158

2.1 Passive control at nozzle ....................................................... 159 2.1.1 Flow at nozzle exit ..................................................... 159 2.1.2 Nozzle geometry ........................................................ 167

2.2 Passive control at target surface ............................................ 169 2.2.1 Protrusion .................................................................. 169 2.2.2 Dimple ...................................................................... 171 2.2.3 Surface curvature ...................................................... 172 2.2.4 Impingement on rotating disk ................................... 173 2.2.5 Inclined jet impingement .......................................... 174

3 Active Control of Jet Impingement ................................................ 174 3.1 Active flow control at nozzle ................................................ 174

3.1.1 Pulsation of jet .......................................................... 174 3.1.2 Shear layer excitation ............................................... 176

3.2 Active flow control at target surface .................................... 177 4 Summary ....................................................................................... 178 References ............................................................................................. 178

CHAPTER 7 Numerical Simulation of Heat Transfer from Impinging Swirling Jets ......................................................................................... 185 B. Sunden, J. Larocque & Z. Wu 1 Introduction .................................................................................... 185 2 Governing Equations ..................................................................... 189 3 Numerical Approach ...................................................................... 191

3.1 Turbulence and turbulence modeling ................................... 191 3.1.1 The RNG k– model ................................................. 191

3.1.2 The SST k– model ................................................. 192 3.1.3 The RSM model ....................................................... 192 3.1.4 The V2f model ......................................................... 192 3.1.5 Near wall treatment .................................................. 192

4 Results and Discussion .................................................................. 192 4.1 Basic test case – reveal of physical influence of swirl ......... 192 4.2 Turbulent swirling impinging jet .......................................... 194 4.3 Calculations vs. experiments by Bilen et al. [33] ................. 195 4.4 Calculations vs. experiments by Huang and El-Genk [35] ... 196

5 Conclusions ................................................................................... 198 Acknowledgement................................................................................. 198 Nomenclature ........................................................................................ 199 Greek symbols ....................................................................................... 199 Subscripts .............................................................................................. 199 References ............................................................................................. 200

CHAPTER 8 Experimental and Numerical Study on Heat Transfer Enhancement of Impingement Jet Cooling by Adding Ribs on Target Surface ................................................................................ 203 K. Takeishi & Y. Oda 1 Introduction ................................................................................... 203 2 Experimental Study ....................................................................... 204

2.1 Heat transfer test with two-dimensional impinging jet nozzle .............................................................................. 204 2.2 Heat transfer test with circular impinging jet nozzle ............ 206 2.3 Naphthalene sublimation method ......................................... 207 2.4 Results and discussion .......................................................... 208

2.4.1 Two-dimensional impinging jet nozzle .................... 208 2.4.2 Circular impingement jet nozzle .............................. 213

3 Numerical Study ............................................................................ 216 3.1 Rib-enhanced two-dimensional jet impingement

heat transfer ......................................................................... 216 3.1.1 Numerical method for RANS ................................... 216 3.1.2 Numerical method for LES ...................................... 217 3.1.3 Results and discussion .............................................. 219

3.2 Round jet impingement heat transfer enhanced by circular rib ........................................................................... 225 3.2.1 Numerical setup ....................................................... 225 3.2.2 Results and discussion ............................................. 226

4 Summary ....................................................................................... 229 References ............................................................................................. 229