Heat Transfer Investigation of an Aggressive Intermediate Turbine Duct: Part 1—Experimental Investigation

2010 ◽  
Author(s):  
Carlos Arroyo Osso ◽  
T. Gunnar Johansson ◽  
Fredrik Wallin
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Computational Study ◽  
Convective Heat Transfer Coefficient ◽  
Low Pressure ◽  
Flow Measurements ◽  
Pressure Losses ◽  
Turbofan Engines ◽  
Intermediate Turbine Duct ◽  
Inlet Conditions

In most designs of two-spool turbofan engines, intermediate turbine duct (ITD’s) are used to connect the high-pressure turbine (HPT) with the low-pressure turbine (LPT). Demands for more efficient engines with reduced emissions require more “aggressive ducts”, ducts which provide both a higher radial offset and a larger area ratio in the shortest possible length, while maintaining low pressure losses and avoiding non-uniformities in the outlet flow that might affect the performance of the downstream LPT. The work presented in this paper is part of a more comprehensive experimental and computational study of the flowfield and the heat transfer in an aggressive ITD. The main objectives of the study were to obtain an understanding of the mechanisms governing the heat transfer in ITD’s and to obtain high quality experimental data for the improvement of the CFD-based design tools. This paper consists of two parts. The first one, this one, presents and discusses the results of the experimental study. In the second part, a comparison between the experimental results and a numerical analysis is presented. The duct studied was a state-of-the-art “aggressive” design with nine thick non-turning structural struts. It was tested in a large-scale low-speed experimental facility with a single-stage HPT. In this paper measurements of the steady convective heat transfer coefficient (HTC) distribution on both endwalls and on the strut for the duct design inlet conditions are presented. The heat transfer measurement technique used is based on infrared-thermography. Part of the results of the flow measurements is also included.

Experimental Heat Transfer Investigation of an Aggressive Intermediate Turbine Duct

2012 ◽  
Vol 134 (5) ◽  
Author(s):  
Carlos Arroyo Osso ◽  
T. Gunnar Johansson ◽  
Fredrik Wallin
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Computational Study ◽  
Convective Heat Transfer Coefficient ◽  
Low Pressure ◽  
Flow Measurements ◽  
Pressure Losses ◽  
Intermediate Turbine Duct ◽  
Experimental Heat ◽  
Inlet Conditions

In most designs of two-spool turbofan engines, intermediate turbine ducts (ITDs) are used to connect the high-pressure turbine (HPT) with the low-pressure turbine (LPT). Demands for more efficient engines with reduced emissions require more “aggressive ducts,” ducts which provide both a higher radial offset and a larger area ratio in the shortest possible length, while maintaining low pressure losses and avoiding nonuniformities in the outlet flow that might affect the performance of the downstream LPT. The work presented in this paper is part of a more comprehensive experimental and computational study of the flowfield and the heat transfer in an aggressive ITD. The main objectives of the study were to obtain an understanding of the mechanisms governing the heat transfer in ITDs and to obtain high quality experimental data for the improvement of the CFD-based design tools. This paper presents and discusses the results of the experimental study. The duct studied was a state-of-the-art “aggressive” design with nine thick nonturning structural struts. It was tested in a large-scale low-speed experimental facility with a single-stage HPT. In this paper measurements of the steady convective heat transfer coefficient (HTC) distribution on both endwalls and on the strut for the duct design inlet conditions are presented. The heat transfer measurement technique used is based on infrared thermography. Part of the results of the flow measurements is also included.

Heat Transfer Investigation of an Aggressive Intermediate Turbine Duct: Part 2—Numerical Analysis

2010 ◽  
Author(s):  
Fredrik Wallin ◽  
Carlos Arroyo Osso
Keyword(s):  
Heat Transfer ◽  
High Pressure ◽  
Numerical Analysis ◽  
Aspect Ratio ◽  
Low Pressure ◽  
Area Ratio ◽  
Pressure System ◽  
Intermediate Turbine Duct ◽  
Numerical Predictions ◽  
Inlet Conditions

Demands on improved efficiency, reduced emissions and lowered noise levels result in higher by-pass ratio turbofan engines. The design of the intermediate turbine duct, connecting the high-pressure and low-pressure turbines in a two-spool engine, becomes thus more critical. The radial offset between the high-pressure core and the low-pressure system will increase, which leads to a higher aspect ratio (Δr/L) of the turbine duct. In order to improve the low-pressure turbine performance the turbine duct exit axial velocity could be reduced by increasing the duct area ratio (Aout/Ain). In order to keep the turbine frame weight as low as possible, it is also desirable to keep the duct short, i. e. keep the non-dimensional length (L/hin) as low as possible. Therefore, there is a need to improve the knowledge about the flowfield and heat transfer in aggressive (high aspect ratio/high area ratio) turbine ducts. The work presented here has been performed within the EU FP6 project AITEB-2, focusing on heat transfer in turbines. In a two-part paper the aerothermal behavior of a fairly aggressive intermediate turbine duct with nine non-lifting vanes has been studied. The flowfield and heat transfer data was acquired in the Chalmers Turbine Facility. The first part of the paper focuses on the experimental investigation and results. In this second part of the paper comparisons between experimental data and numerical results are made. The work highlights the challenges associated with numerical predictions of flowfield induced heat transfer in turbine ducts. The numerical analysis was performed using Chalmers in-house compressible flow solver. The experimental results are compared to CFD analyzes using two different turbulence models; k-ε with wall functions and low-Re k-ω SST, and using the measured inlet conditions to the duct as boundary conditions. Previously presented flowfield comparisons showed good agreement between experiments and CFD. The main flow features, such as vorticity and pressure gradients, are reasonably well reproduced by the CFD. The heat transfer results show reasonable agreement on the hub and on the downstream part of the shroud. The heat transfer agreement is, however, poor on the shroud in the region between the duct inlet and the leading edge of the vane.

Numerical Modeling of Heat Transfer and Pressure Losses for Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2007 ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. CFD predictions of blade tip heat transfer are compared to test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; they are flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25, 2.0, and 2.75% of blade span. The tip heat transfer results of the numerical models agree fairly well with the data and are comparable to other CFD predictions in the open literature.

Design of an Intermediate Turbine Duct Downstream of a High Pressure Turbine

2016 ◽  
Author(s):  
Chaoshan Hou ◽  
Hu Wu
Keyword(s):  
High Pressure ◽  
Three Dimensional ◽  
Low Pressure ◽  
Aerodynamic Load ◽  
Duct Flow ◽  
Original Design ◽  
High Pressure Turbine ◽  
Intermediate Turbine Duct ◽  
Low Pressure Turbine ◽  
Inlet Conditions

The flow leaving the high pressure turbine should be guided to the low pressure turbine by an annular diffuser, which is called as the intermediate turbine duct. Flow separation, which would result in secondary flow and cause great flow loss, is easily induced by the negative pressure gradient inside the duct. And such non-uniform flow field would also affect the inlet conditions of the low pressure turbine, resulting in efficiency reduction of low pressure turbine. Highly efficient intermediate turbine duct cannot be designed without considering the effects of the rotating row of the high pressure turbine. A typical turbine model is simulated by commercial computational fluid dynamics method. This model is used to validate the accuracy and reliability of the selected numerical method by comparing the numerical results with the experimental results. An intermediate turbine duct with eight struts has been designed initially downstream of an existing high pressure turbine. On the basis of the original design, the main purpose of this paper is to reduce the net aerodynamic load on the strut surface and thus minimize the overall duct loss. Full three-dimensional inverse method is applied to the redesign of the struts. It is revealed that the duct with new struts after inverse design has an improved performance as compared with the original one.

Numerical Modeling of Heat Transfer and Pressure Losses for an Uncooled Gas Turbine Blade Tip: Effect of Tip Clearance and Tip Geometry

2009 ◽  
Vol 1 (2) ◽  
Author(s):  
Lamyaa A. El-Gabry
Keyword(s):  
Heat Transfer ◽  
Mach Number ◽  
Gas Turbine ◽  
Computational Study ◽  
Numerical Models ◽  
Pressure Ratio ◽  
Tip Clearance ◽  
Pressure Losses ◽  
Blade Tip ◽  
Exit Mach Number

A computational study has been performed to predict the heat transfer distribution on the blade tip surface for a representative gas turbine first stage blade. Computational fluid dynamics (CFD) predictions of blade tip heat transfer are compared with test measurements taken in a linear cascade, when available. The blade geometry has an inlet Mach number of 0.3 and an exit Mach number of 0.75, pressure ratio of 1.5, exit Reynolds number based on axial chord of 2.57×106, and total turning of 110 deg. Three blade tip configurations were considered; a flat tip, a full perimeter squealer, and an offset squealer where the rim is offset to the interior of the tip perimeter. These three tip geometries were modeled at three tip clearances of 1.25%, 2.0%, and 2.75% of the blade span. The tip heat transfer results of the numerical models agree well with data. For the case in which side-by-side comparison with test measurements in the open literature is possible, the magnitude of the heat transfer coefficient in the “sweet spot” matches data exactly and shows 20–50% better agreement with experiment than prior CFD predictions of this same case.

scholarly journals Endwall Heat Transfer Measurements in a Transonic Turbine Cascade

1998 ◽  
Vol 120 (2) ◽  
pp. 305-313 ◽  
Author(s):  
P. W. Giel ◽  
D. R. Thurman ◽  
G. J. Van Fossen ◽  
S. A. Hippensteele ◽  
R. J. Boyle
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Turbine Blade ◽  
Large Scale ◽  
Model Verification ◽  
Quality Data ◽  
Free Stream Turbulence ◽  
Transonic Turbine ◽  
Mach Numbers ◽  
Inlet Conditions

Turbine blade endwall heat transfer measurements are presented for a range of Reynolds and Mach numbers. Data were obtained for Reynolds numbers based on inlet conditions of 0.5 and 1.0 × 106, for isentropic exit Mach numbers of 1.0 and 1.3, and for free-stream turbulence intensities of 0.25 and 7.0 percent. Tests were conducted in a linear cascade at the NASA Lewis Transonic Turbine Blade Cascade Facility. The test article was a turbine rotor with 136 deg of turning and an axial chord of 12.7 cm. The large scale allowed for very detailed measurements of both flow field and surface phenomena. The intent of the work is to provide benchmark quality data for CFD code and model verification. The flow field in the cascade is highly three dimensional as a result of thick boundary layers at the test section inlet. Endwall heat transfer data were obtained using a steady-state liquid crystal technique.

Shorten the Intermediate Turbine Duct Length by Applying an Integrated Concept

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
A. Marn ◽  
E. Göttlich ◽  
D. Cadrecha ◽  
H. P. Pirker
Keyword(s):  
High Pressure ◽  
Flow Distribution ◽  
Low Pressure ◽  
Secondary Flows ◽  
Base Line ◽  
Flow Angle ◽  
Intermediate Turbine Duct ◽  
Integrated Concept ◽  
Inlet Conditions ◽  
Base Design

The demand of further increased bypass ratio of aero engines will lead to low pressure turbines with larger diameters, which rotate at lower speed. Therefore, it is necessary to guide the flow leaving the high pressure turbine to the low pressure turbine at larger diameters minimizing the losses and providing an adequate flow at the low pressure (LP)-turbine inlet. Due to costs and weight, this intermediate turbine duct has to be as short as possible. This would lead to an aggressive (high diffusion) s-shaped duct geometry. It is possible to shorten the duct simply by reducing the length but the risk of separation is rising and losses increase. Another approach to shorten the duct and thus the engine length is to apply a so called integrated concept. These are novel concepts where the struts, mounted in the transition duct, replace the usually following LP-vane row. This configuration should replace the first LP-vane row from a front bearing engine architecture where the vane needs a big area to hold bearing services. That means the rotor is located directly downstream of the strut. This means that the struts have to provide the downstream blade row with undisturbed inflow with suitable flow angle and Mach number. Therefore, the (lifting) strut has a distinct three-dimensional design in the more downstream part, while in the more upstream part, it has to be cylindrical to be able to lead through supply lines. In spite of the longer chord compared with the base design, this struts have a thickness to chord ratio of 18%. To apply this concept, a compromise must be found between the number of struts (weight), vibration, noise, and occurring flow disturbances due to the secondary flows and losses. The struts and the outer duct wall have been designed by Industria de Turbopropulsores. The inner duct was kept the same as for the base line configuration (designed by Motoren und Turbinen Union). The aim of the design was to have similar duct outflow conditions (exit flow angle and radial mass flow distribution) as the base design with which it is compared in this paper. This base design consists of a single transonic high pressure (HP)-turbine stage, an aggressive s-shaped intermediate turbine duct, and a LP-vane row. Both designs used the same HP-turbine and were run in the continuously operating Transonic Test Turbine Facility at Graz University of Technology under the same engine representative inlet conditions. The flow field upstream and downstream the LP-vane and the strut, respectively, has been investigated by means of five hole probes. A rough estimation of the overall duct loss is given as well as the upper and lower weight reduction limit for the integrated concept.

Experimental Investigation of the Time-Averaged Flow in an Intermediate Turbine Duct

2008 ◽  
Author(s):  
Lars-Uno Axelsson ◽  
T. Gunnar Johansson
Keyword(s):  
Experimental Investigation ◽  
High Pressure ◽  
Low Pressure ◽  
Jet Engines ◽  
Mean Flow ◽  
Complex Flow ◽  
Turbofan Engines ◽  
Intermediate Turbine Duct ◽  
Static Pressure Distribution ◽  
Complex Flow Structure

Intermediate turbine ducts are used in modern multi-spool jet engines to connect the high pressure turbine with the low-pressure turbine. The trend towards turbofan engines with larger by-pass ratios requires the radial off-set between the high-pressure and low-pressure turbines to increase with a corresponding increase in radial off-set for the intermediate turbine ducts. Other improvements of the ducts is to make them shorter and more diffusing but this strive towards more aggressive design increases the risk for separation. This paper deals with an experimental investigation of the time-averaged mean flow field and turbulence development in an aggressive intermediate turbine duct (downstream a rotating turbine stage) using a 5-hole probe and 2-component hot-wire anemometry. In addition the duct endwall static pressure distribution is discussed. The investigation revealed the complex flow structure development within the duct, where co-rotating vortices emanating from the break-up of the tip gap shear-layer dominates the flow pattern.

An Experimental Study of Heat Transfer and Film Cooling on Large-Scale Turbine Endwalls

1974 ◽  
Vol 96 (4) ◽  
pp. 524-529 ◽  
Author(s):  
M. F. Blair
Keyword(s):  
Heat Transfer ◽  
Thermal Conductivity ◽  
Film Cooling ◽  
Large Scale ◽  
Convective Heat Transfer Coefficient ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Test Models ◽  
Turbine Vane ◽  
Flow Vortex

Experiments were conducted to determine the film cooling effectiveness and convective heat transfer coefficient distributions on the endwall of a large-scale turbine vane passage. The vane test models employed simulated the passage geometry and upstream cooling slot geometry of a typical first stage turbine. The test models were constructed of low thermal conductivity foam and foil heaters. The tests were conducted at a typical engine Reynolds number but at lower than typical Mach numbers. The film cooling effectiveness distribution for the entire endwall and the heat transfer distribution for the downstream one-half of the endwall were characterized by large gapwise variations which were attributed to a secondary flow vortex.

Investigation of Innovative Trailing Edge Cooling Configurations With Enlarged Pedestals and Square or Semicircular Ribs: Part II—Numerical Results

2008 ◽  
Author(s):  
Emiliano Di Carmine ◽  
Bruno Facchini ◽  
Luca Mangani
Keyword(s):  
Heat Transfer ◽  
Cooling System ◽  
Convective Heat Transfer Coefficient ◽  
Turbulence Models ◽  
Internal Cooling ◽  
Trailing Edge ◽  
Pressure Losses ◽  
Structural Resistance ◽  
Pin Fins ◽  
Rib Turbulators

Trailing edge is a critical region for turbine airfoils since this part of the blade has to match aerodynamic, cooling and structural requirements at the same time. In fact aerodynamic losses are strictly related to trailing edge thickness which, on the contrary, tends to be increased to implement an internal cooling system, in order to face high thermal loads. At the moment the most employed devices consist of pin fins of various shapes, which contribute to both heat transfer enhancement and structural resistance improvement. Enlarged pedestals decrease pressure losses in comparison with multirow pin fins, even if the heat transfer increase is limited. This work deals with the investigation of the usage of enlarged pedestals, inserted in a wedge shaped duct, in conjunction with square or semicircular rib turbulators. The aim of the analysis is the evaluation of the convective Heat Transfer Coefficient (HTC) distribution over the endwall surface and the pressure drop of the converging duct. Numerical analysis used 3D RANS calculations. An in-house modified object-oriented CFD code and a commercial one were used. Several turbulence models and mesh types were tested. Numerical calculations were compared with experimental results obtained on the same geometries using a transient Thermochromic Liquid Crystals (TLC) based technique. Goals of this comparison are both the evaluation of the accuracy of CFD packages with standard two equation turbulence models in heat transfer problems with complex geometries and the analysis of flow details to complete and support experimental activity.

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