A Computational Study on Turbulent Flow and Heat Transfer in a Strongly Curved RC/D = 0.65 Turbine Blade Cooling Passage

2007 ◽  
Author(s):  
Jose Martinez Lucci ◽  
R. S. Amano ◽  
Krishna S. Guntur
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Low Reynolds Number ◽  
Turbulence Models ◽  
Higher Order ◽  
Gas Turbine Blade ◽  
Cooling Performance ◽  
Flow And Heat Transfer

It has been a common practice that serpentine cooling passages are used in gas turbine blade to enhance the cooling performance. Insufficient cooled blades are subject to oxidation, to cause creep rupture, and even to cause melting of the material. To control and improve temperature of the blade, we have to have a better understanding of flow behavior and heat transfer inside strongly curved U-bends. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Previous studies have shown that the flow and heat transfer features through curved bends, even with moderate curvature, cannot be accurately simulated. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method for achieving accurate computations. The three-dimensional turbulent flows and heat transfer inside a sharp U-bend are numerically studied by using a non-linear low-Reynolds number (low-Re) k-ω model in which the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume difference method incorporated with the higher-order bounded interpolation scheme has been employed in the present study. For the purpose of comparison, the predictions with the linear low-Reynolds number k-ω model were also performed. The success of the present prediction indicates that the model can be applied to the flow and heat transfer through a coolant passage in an actual gas turbine blade. It is shown that the present non-linear model produces satisfactory predictions of the flow development inside the sharp U-bend comparing with linear Launder-Sharma model. In the present study, three turbulence models are used to predict Nysselt number distribution as well.

A Computational Study of Turbulent Flow and Heat Transfer Through RC/D =3.357 U-Bend Cooling Passage of Gas Turbine Blade

2007 ◽  
Author(s):  
Krishna S. Guntur ◽  
Jose Martinez Lucci ◽  
R. S. Amano
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Low Reynolds Number ◽  
Higher Order ◽  
Gas Turbine Blade ◽  
Cooling Performance ◽  
Flow And Heat Transfer ◽  
Low Reynolds

It has been a common practice that serpentine cooling passages are used in gas turbine blade to enhance the cooling performance. Insufficient cooled blades are subject to oxidation, to cause creep rupture, and even to cause melting of the material. To control and improve temperature of blade, we have to have a better understanding of flow behavior and heat transfer inside strongly curved U-bends. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Previous studies have shown that the flow and heat transfer features through curved bends, even with moderate curvature, cannot be accurately simulated. It is the conventional belief and practice that the usage of a proper turbulence model and a reliable numerical method for achieving accurate computations. The three-dimensional turbulent flows and heat transfer inside a sharp U-bend are numerically studied by using a non-linear low-Reynolds number (low-Re) k-ω model in which the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume difference method incorporated with the higher-order bounded interpolation scheme has been employed in the present study. For the purpose of comparison, the predictions with the linear low-Reynolds number k-ω model were also performed. The success of the present prediction indicates that the model can be applied to the flow and heat transfer through a coolant passage in an actual gas turbine blade.

Computational Study of Gas Turbine Blade Cooling Channel

2010 ◽  
Author(s):  
R. S. Amano ◽  
Krishna Guntur ◽  
Jose Martinez Lucci
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Gas Turbine ◽  
Turbulence Models ◽  
Flow Patterns ◽  
Higher Order ◽  
Secondary Flows ◽  
Complex Flow ◽  
Cooling Performance ◽  
Cooling Channels

It has been a common practice to use cooling passages in gas turbine blade in order to keep the blade temperatures within the operating range. Insufficiently cooled blades are subject to oxidation, to cause creep rupture, and even to cause melting of the material. To design better cooling passages, better understanding of the flow patterns within the complicated flow channels is essential. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. Power output and the efficiency of turbine are completely related to gas firing temperature from chamber. The increment of gas firing temperature is limited by the blade material properties. Advancements in the cooling technology resulted in high firing temperatures with acceptable material temperatures. To better design the cooling channels and to improve the heat transfer, many researchers are studying the flow patterns inside the cooling channels both experimentally and computationally. In this paper, the authors present the performance of three turbulence models using TEACH software code in comparison with the experimental values. To test the performance, a square duct with rectangular ribs oriented at 90° and 45° degree and placed at regular intervals. The channel also has bleed holes. The normalized Nusselt number obtained from simulation are validated with that of experiment. The Reynolds number is set at 10,000 for both the simulation and experiment. The interactions between secondary flows and separation lead to very complex flow patterns. To accurately simulate these flows and heat transfer, both refined turbulence models and higher-order numerical schemes are indispensable for turbine designers to improve the cooling performance. The three-dimensional turbulent flows and heat transfer are numerically studied by using several different turbulence models, such as non-linear low-Reynolds number k-omega and Reynolds Stress (RSM) models. In k-omega model the cubic terms are included to represent the effects of extra strain-rates such as streamline curvature and three-dimensionality on both turbulence normal and shear stresses. The finite volume difference method incorporated with the higher-order bounded interpolation scheme has been employed in the present study. The outcome of this study will help determine the best suitable turbulence model for future studies.

Unsteady CFD Analysis of Turbulent Flow and Heat Transfer in a Gas Turbine Blade Trailing Edge Subjected to Rotation

2012 ◽  
Author(s):  
Domenico Borello ◽  
Giovanni Delibra ◽  
Cosimo Bianchini ◽  
Antonio Andreini
Keyword(s):  
Heat Transfer ◽  
Turbulent Flow ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Heated Surface ◽  
Heat Removal ◽  
Gas Turbine Blade ◽  
Trailing Edge ◽  
Flow And Heat Transfer ◽  
The Impact

Internal cooling of gas turbine blade represents a challenging task involving several different phenomena as, among others, highly three-dimensional unsteady fluid flow, efficient heat transfer and structural design. This paper focuses on the analysis of the turbulent flow and heat transfer inside a typical wedge–shaped trailing edge cooling duct of a gas turbine blade. In the configuration under scrutiny the coolant flows inside the duct in radial direction and it leaves the blade through the trailing edge after a 90 deg turning. At first an analysis of the flow and thermal fields in stationary conditions was carried out. Then the effects of rotational motion were investigated for a rotation number of 0.275. The rotation axis here considered is normal to the inflow and outflow bulk velocity, representing schematically a highly loaded blade configuration. The work aimed to i) analyse the dynamic of the vortical structures under the influence of strong body forces and the constraints induced by the internal geometry and ii) to study the impact of such motions on the mechanisms of heat removal. The final aim was to verify the design of the equipment and to detect the possible presence of regions subjected to high thermal loads. The analysis is carried out using the well assessed open source code OpenFOAM written in C++ and widely validated by several scientists and researchers around the world. The unsteadiness of the flow inside the trailing edge required to adopt models that accurately reconstructed the flow field. As the computational costs associated to LES (especially in the near wall regions) largely exceed the available resources, we chose for the simulation the SAS model of Menter, that was validated in a series of benchmark and industrially relevant test cases and allowed to reconstruct a part of the turbulence spectra through a scale-adaptive mechanism. Assessment of the obtained results with steady-state k-ω SST computations and available experimental results was carried out. The present analysis demonstrated that a strong unsteadiness develops inside the trailing edge and that the rotation generated strong secondary motions that enhanced the dynamic of heat removal, leading to a less severe temperature distribution on the heated surface w.r.t the non rotating case.

scholarly journals Numerical Analysis of Two-Dimensional Compressible Viscous Flow in Turbomachinery Cascades Using an Improved k-ε Turbulence Model

1997 ◽  
Author(s):  
Debasish Biswas ◽  
Hideo Iwasaki ◽  
Masaru Ishizuka
Keyword(s):  
Boundary Layer ◽  
Reynolds Number ◽  
Viscous Flow ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Turbulence Model ◽  
Higher Order ◽  
Tvd Scheme ◽  
Two Dimensional ◽  
Gas Turbine Blade

In the present work two-dimensional viscous flows through compressor and gas turbine blade cascades at low subsonic and transonic speed are analyzed by solving compressible N-S equations in the generalized co-ordinate system, so that sufficient number of grid points could be distributed in the boundary layer and wake regions. An efficient Implicit Approximate Factorization (IAF) finite difference scheme, originally developed by Beam-Warming, is used together with a higher order Total Variation Diminishing (TVD) scheme based on the MUSCL-type approach with the Roe’s approximate Rieman solver for shock capturing. In order to predict the boundary layer turbulence characteristics, shock boundary layer interaction, transition from laminar to turbulent flow, etc. with sufficient accuracy, an improved low Reynolds number k-ε turbulence model developed by the authors is used. In this k-ε model, the low Reynolds number damping factors are defined as a function of turbulence Reynolds number which is only a rather general indicator of the degree of turbulence activity at any location in the flow rather than a specific function of the location itself. Computations are carried out for different flow conditions of compressor and gas turbine blade cascades for which detailed and reliable information about shock location, shock losses, viscous losses, blade surface pressure distribution and overall performance are available. Comparison of computed results with the experimental data showed a very good agreement. The results demonstrated that the Navier-Stokes approach using the present k-ε turbulence model and higher order TVD scheme would lead to improved prediction of viscous flow phenomena in turbomachinery cascades.

Study On Flow and Heat Transfer Characteristics of a New-Proposed Alternating Elliptical U-Channel in the Mid-Chord Region of Gas Turbine Blade

2021 ◽  
Author(s):  
Kun Xiao ◽  
Juan He ◽  
Zhenping Feng
Keyword(s):  
Heat Transfer ◽  
Aspect Ratio ◽  
Gas Turbine ◽  
Turbine Blade ◽  
Thermal Performance ◽  
Cooling Channel ◽  
Gas Turbine Blade ◽  
Heat Transfer Characteristics ◽  
Flow And Heat Transfer ◽  
Bend Channel

Abstract This paper proposed an alternating elliptical U-bend cooling channel which can be applied in the mid-chord region of gas turbine blade and manufactured by precision casting, based on the optimal flow field structure deduced from the Field Synergy Principle, and investigated the flow and heat transfer characteristics in this alternating elliptical U-bend cooling channel thoroughly. Numerical simulations were performed by using 3D steady solver of Reynolds-averaged Navier-Stokes equations (RANS) with the standard k-e turbulence model. The influence of alternating of cross section on heat transfer and pressure drop of the channel was studied by comparing with the smooth elliptical U-bend channel. On this basis, the effect of aspect ratio (length ratio of the major axis to the minor axis) and alternating angle were further investigated. The results showed that, in the first pass of the alternating elliptical U-bend channel, for different Re, four or eight longitudinal vortices were generated. In the second pass, the alternating elliptical channel restrained the flow separation to a certain extent and a double-vortex structure was formed. The average Nusselt number of the alternating elliptical U-bend channel was significantly higher than that of the straight channel, but the pressure loss only increased slightly. With the increase of aspect ratio, the thermal performance of the channel increased, and when the alternating angle is between 40° and 90°, the thermal performance nearly kept constant and also the best.

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