Begell House Inc.
Heat Transfer Research
HTR
1064-2285
41
8
2010
Preface: Gas Turbine Heat Transfer
801-802
10.1615/HeatTransRes.v41.i8.20
This issue has papers selected by the Scientific Committee from the symposium Turbine-09 sponsored by the International Center for Heat and Mass Transfer (ICHMT). Turbine-09 was held in Antalya, Turkey, August 9−14, 2009. It was the third symposium related to heat transfer in high-performance gas turbines sponsored by the ICHMT. The first, held in Marathon, Greece, in August 1992, resulted in the book Heat Transfer in Turbomachinery. The second, Turbine 2000, conducted in Cesme, Turkey, in August 2000, was published in the book Heat Transfer in Gas Turbine Systems. The three symposia offered invited keynote lectures and contributed papers by some of the world’s best-known authorities on gas turbine heat transfer. Each of the two proceedings volumes and these special issues (Vol. 41, Nos. 6−8, 2010 and Vol. 42, Nos. 1 and 2, 2011) contain a wealth of information from key industrial, academic, and nonprofit laboratories.
The objective of the symposium and of these special issues is to provide an opportunity to present and review the most recent developments in heat transfer and thermal control applied to modern, high-temperature gas turbine systems. Presented are: experimental results and techniques, computational studies and methods, and design recommendations. Aspects of heat transfer in rotating machinery include:
combustor and transition section heat transfer,
heat exchange to turbine airfoil and endwall surfaces within the gas path,
stator internal heat transfer,
disk cavity and blade internal flow and heat transfer,
innovative cooling techniques, and
heat exchange in turbines with combined cycles.
The results published in these issues should be valuable to researchers in heat transfer as well as to designers of gas turbine systems.
Recent Studies in Turbine Blade Internal Cooling
803-828
10.1615/HeatTransRes.v41.i8.30
Michael
Huh
Department of Mechanical Engineering, The University of Texas at Tyler, Tyler, Texas 75799, USA
Je-Chin
Han
Turbine Heat Transfer Laboratory, Department of Mechanical Engineering, Texas A&M University College Sation, TX 77843-3123, USA
gas turbines
blade cooling
totating effect
Gas turbines are used extensively for aircraft propulsion, land-based power generation, and industrial applications. The turbine inlet temperatures are far above the permissible metal temperatures. Therefore, there is a need to cool the blades for safe operation. Modern developments in turbine cooling technology play a critical role in increasing the thermal efficiency and power output of advanced gas turbine designs. Turbine blades and vanes are cooled internally and externally. This paper focuses on turbine blade internal cooling. Internal cooling is typically achieved by passing the coolant through several rib-enhanced serpentine passages inside the blades. Impinging jets and pin fins are also used for internal cooling. In the past 10 years there has been considerable progress in turbine blade internal cooling research and this paper is limited to reviewing a few selected publications to reflect recent developments in this area. In particular, this paper focuses on the effects of channel inlet geometry, sharp 180° turning, and channel cross-section aspect ratio on the coolant passages heat transfer at high rotation number conditions. Rotation effects on the blade leading-edge triangular-shaped channel and trailing-edge wedge-shaped channel with coolant ejection are included.
Heat Transfer and Flow Testing in Engine HP Turbine Cooling System Development
829-847
10.1615/HeatTransRes.v41.i8.40
Peter T.
Ireland
Department of Engineering Science and St. Anne's College, University of Oxford, England.
Vikram
Mittal
Vehicles and Robotics Group, C.S. Draper Laboratory, 550 Technology Sq, MS20, Cambridge, MA 02139 USA
Dougal
Jackson
Turbines SCU, Rolls-Royce plc, Moor Lane, PO box 32, Derby. DE24 8BJ, UK
turbine cooling
rapid prototyping
SLA
liquid crystal
heat transfer
turbine heat transfer
The speed with which a new aircraft engine is developed prevents extensive experimental testing of key turbine components. For this reason, design engineers rely increasingly on computer simulations to develop and perfect components before committing to final designs. CFD predictions can fail to accurately predict some key features of turbomachinery flows, and design engineers often seek to calibrate their designs and CFD predictions against test data. This paper addresses the use of flow and heat transfer experiments in the context of turbine cooling system development. It reviews how experiments can be used to support both research activity and the engine development program (EDP). The paper describes the state of the art in Perspex model test technology and the introduction of rapid prototyping (RP). This paper reports applications of these models to aerothermal testing of turbine component and reviews the advantages and the shortcomings of such testing. The paper focuses on the stereo-lithography (SL) technique as this remains the most popular method for producing test models for aero-thermal tests. The paper also explains how judicious use of RP test data can be used in cooling system development to arrive at optimal systems.
Trailing Edge Film Cooling of Gas Turbine Airfoils — Effects of Ejection Lip Geometry on Film Cooling Effectiveness and Heat Transfer
849-865
10.1615/HeatTransRes.v41.i8.50
Tim
Horbach
Institut fuer Thermische Stroemungsmaschinen (ITS), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
Achmed
Schulz
Institut fuer Thermische Stroemungsmaschinen (ITS), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
Hans-Jorg
Bauer
Institut fuer Thermische Stroemungsmaschinen (ITS), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
rib array
heat transfer coefficients
discharge coefficients
blade cooling
flow interaction
internal turbulators
cooling design
slot
blowing ratio
The present paper concentrates on trailing edge film cooling of modern high-pressure turbine blades using cooling ejection through planar slots with a pressure side cutback. The experimental test section consists of a generic scaled-up trailing edge model. The effects of different geometric configurations on the structure and the performance of the cooling film are investigated in terms of film cooling effectiveness, heat transfer coefficients, and discharge behavior. The interaction between an internal turbulator array of ribs with the ejection slot lip is of major interest. Different designs of the cooling ejection lip are applied. Four different ratios of lip thickness to ejection slot height (t/H = 0.2, 0.5, 1.0, 1.5) are investigated, as well as three different lip contours representing typical manufacturing imperfections and wear. The experiments are performed at engine-realistic density ratios. The blowing ratios are varied between 0.2 < M < 1.25. The results show a strong dependency on ejection lip thickness and only marginal changes when the lip shape is varied.
An Experimental Study of Airfoil and Endwall Heat Transfer on a Linear Turbine Blade Cascade — Secondary Flow and Surface Roughness Effects
867-887
10.1615/HeatTransRes.v41.i8.60
Marco
Lorenz
Institut fuer Thermische Stroemungsmaschinen, Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
Achmed
Schulz
Institut fuer Thermische Stroemungsmaschinen (ITS), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
Hans-Jorg
Bauer
Institut fuer Thermische Stroemungsmaschinen (ITS), Karlsruhe Institute of Technology (KIT), 76131 Karlsruhe, Germany
turbine airfoil
platform
horseshoe vortex
turbulence
surface roughness
The present study is part of a comprehensive heat transfer analysis on a highly loaded turbine blade and endwall with varying surface roughness. In this paper, a smooth airfoil with an endwall of varying surface roughness is considered in order to investigate secondary flow and surface roughness effects on airfoil and endwall heat transfer. The measurements have been conducted in a linear cascade with low pressure blades at several freestream turbulence levels (Tu1 = 1.4% to 10.1%) and varying inlet Reynolds numbers (Re1,c = 50,000 to 250,000). Aerodynamic measurements have been carried out on the airfoil at midspan and complemented by oil paint visualization on airfoil and platform. Heat transfer on both the full-span suction and pressure surfaces of the airfoil and endwall is shown for smooth surfaces. Moreover, rough endwall surfaces are compared to the smooth reference case showing a maximum increase of local heat transfer of up to 240% due to surface roughness.
Experimental Study of Heat Transfer from Impinging Jet with Upstream and Downstream Crossflow
889-900
10.1615/HeatTransRes.v41.i8.70
Daniel
Thibault
Laboratoire d'Etudes Thermiques - UMR CNRS 6608 ENSMA - University of Poitiers, BP 40109 - 86961 Chasseneuil Cedex France
Matthieu
Fenot
Institut Pprime, Departement Fluides, Thermique et Combustion. Laboratoire d'Etudes Thermiques - UMR CNRS 6608 ENSMA - University of Poitiers, BP 40109 - 86961 Chasseneuil Cedex France
Gildas
Lalizel
Institut Pprime, Departement Fluides, Thermique et Combustion. Laboratoire d'Etudes Thermiques - UMR CNRS 6608 ENSMA - University of Poitiers, BP 40109 - 86961 Chasseneuil Cedex France
Eva
Dorignac
Institut Pprime, Departement Fluides, Thermique et Combustion. Axe COST. ENSMA - Universite de Poitiers - BP 40109. 1, avenue Clement ADER. 86961 Futuroscope CHASSENEUIL cedex
forced convection
impingement
upstream crossflow
downstream crossflow
infrared thermography
particle imaging velocity
heat transfer coefficient
velocity distribution
turbulent intensity distribution
Numerous geometrical and flow parameters can affect the heat transfer in the impinging jet cooling methods. In this study, a configuration close to a real case of vane cooling was adopted. It consists of a main crossflow flowing into an injection hole of diameter D perpendicular to the main flow through a thin plate of thickness t equal to D and the Reynolds number of the injection is fixed to 23,000. A secondary crossflow with a Reynolds number of 1000 is fixed between the exit of the jet and the impingement region, to simulate the flow stream evacuation from the leading edge to the trailing edge of the vane. This geometry is very different from a jet issued from a long pipe as described in many previous studies. The flow field of the jet in the present case has a three-dimensional behavior due to its complex geometry. High levels of turbulence at the exit of the nozzle are observed with Particle Image Velocimetry measurements. The fields of the reference temperature and convective heat transfer coefficient on the impingement surface are calculated from infrared thermography measurements. The results show a significant drop of the heat transfer in such geometry.
Experimental and Theoretical Analysis of Heat Transfer Characteristics in a Rectangular Duct with Jet Impingement
901-913
10.1615/HeatTransRes.v41.i8.80
Unal
UYSAL
Sakarya University
F.
Sahin
General Directorate of Highways, 07000 Antalya, TURKEY
MinKing K.
Chyu
Department of Mechanical Engineering and Materials Science University of Pittsburgh, Pittsburgh, PA 15261, USA
impingement jets
thermochromic liquid crystals
forced convection in ducts
gas turbines cooling
The heat transfer characteristics are analyzed in a rectangular cross section duct where impingement jet technique is applied for the purpose of heating and cooling. Heat transfer characteristics on surfaces are calculated using commercial CFD software, Fluent. Numerical results are compared with the experimental results obtained through a transient liquid crystal technique. To better present the heat transfer results, different cross-sectional size geometric models are used. The geometric models are of six in-line circular jets housed in a confined rectangular channel. As the jet temperature varies with time during a transient test, a time-depended solution method was selected in Fluent. One of the primary varying parameters in the present study is the magnitude of spacing between the jet exit and target plate. The jet Reynolds numbers range from 14,000 to 40,000 for every geometry. The effects of crossflow on the overall flow characteristics in the housed channel and heat transfer distributions on both target surface and jet-issuing plate are investigated. Comparison was made between the present numerical results and experimental data obtained earlier by the lead author, Uysal et al. [1]. The companion experimental study was based on the transient thermochromic liquid crystal (TLC) measurements on detailed local heat transfer distributions on both the target surface and jet-issuing surface.