Assessment of low- and high-fidelity turbulence models for heat transfer predictions in low-prandlt number flows

Computational Fluid Dynamics is a fundamental tool to simulate the flow field and the multi-physics nature of the phenomena involved in gas turbine combustors, supporting their design since the very preliminary phases. Standard steady state RANS turbulence models provide a reasonable prediction, despite some well-known limitations in reproducing the turbulent mixing in highly unsteady flows. Their affordable cost is ideal in the preliminary design steps, whereas, in the detailed phase of the design process, turbulence scale-resolving methods (such as LES or similar approaches) can be preferred to significantly improve the accuracy. Despite that, in dealing with multi-physics and multi-scale problems, as for Conjugate Heat Transfer (CHT) in presence of radiation, transient approaches are not always affordable and appropriate numerical treatments are necessary to properly account for the huge range of characteristics scales in space and time that occur when turbulence is resolved and heat conduction is simulated contextually. The present work describes an innovative methodology to perform CHT simulations accounting for multi-physics and multi-scale problems. Such methodology, named U-THERM3D, is applied for the metal temperature prediction of an annular aeroengine lean burn combustor. The theoretical formulations of the tool are described, together with its numerical implementation in the commercial CFD code ANSYS Fluent. The proposed approach is based on a time de-synchronization of the involved time dependent physics permitting to significantly speed up the calculation with respect to fully coupled strategy, preserving at the same time the effect of unsteady heat transfer on the final time averaged predicted metal temperature. The results of some preliminary assessment tests of its consistency and accuracy are reported before showing its exploitation on the real combustor. The results are compared against steady-state calculations and experimental data obtained by full annular tests at real scale conditions. The work confirms the importance of high-fidelity CFD approaches for the aerothermal prediction of liner metal temperature.

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Results of 4-equation turbulence models in the prediction of heat transfer to supercritical pressure fluids

Nuclear Engineering and Design ◽

10.1016/j.nucengdes.2014.11.004 ◽

2015 ◽

Vol 281 ◽

pp. 5-14 ◽

Cited By ~ 22

Author(s):

Andrea Pucciarelli ◽

Irene Borroni ◽

Medhat Sharabi ◽

Walter Ambrosini

Keyword(s):

Heat Transfer ◽

Turbulence Models ◽

Supercritical Pressure

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Comparison of Two-Equation Turbulence Models for Prediction of Heat Transfer on Film-Cooled Turbine Blades

Volume 3: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/97-gt-024 ◽

1997 ◽

Author(s):

Vijay K. Garg ◽

Ali A. Ameri

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Film Cooling ◽

Turbine Blades ◽

Three Dimensional ◽

Turbulence Models ◽

Computer Time ◽

Suction Surface ◽

The Heat Transfer Coefficient

A three-dimensional Navier-Stokes code has been used to compute the heat transfer coefficient on two film-cooled turbine blades, namely the VKI rotor with six rows of cooling holes including three rows on the shower head, and the C3X vane with nine rows of holes including five rows on the shower head. Predictions of heat transfer coefficient at the blade surface using three two-equation turbulence models, specifically, Coakley’s q-ω model, Chien’s k-ε model and Wilcox’s k-ω model with Menter’s modifications, have been compared with the experimental data of Camci and Arts (1990) for the VKI rotor, and of Hylton et al. (1988) for the C3X vane along with predictions using the Baldwin-Lomax (B-L) model taken from Garg and Gaugler (1995). It is found that for the cases considered here the two-equation models predict the blade heat transfer somewhat better than the B-L model except immediately downstream of the film-cooling holes on the suction surface of the VKI rotor, and over most of the suction surface of the C3X vane. However, all two-equation models require 40% more computer core than the B-L model for solution, and while the q-ω and k-ε models need 40% more computer time than the B-L model, the k-ω model requires at least 65% more time due to slower rate of convergence. It is found that the heat transfer coefficient exhibits a strong spanwise as well as streamwise variation for both blades and all turbulence models.

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Numerical Simulation of Turbine Blade Boundary Layer and Heat Transfer and Assessment of Turbulence Models

Journal of Turbomachinery ◽

10.1115/1.2841190 ◽

1997 ◽

Vol 119 (4) ◽

pp. 794-801 ◽

Cited By ~ 7

Author(s):

J. Luo ◽

B. Lakshminarayana

Keyword(s):

Heat Transfer ◽

Boundary Layer ◽

Reynolds Number ◽

Low Reynolds Number ◽

Turbulence Models ◽

Navier Stokes ◽

Bypass Transition ◽

Boundary Layer Development ◽

Low Reynolds ◽

Layer Development

The boundary layer development and convective heat transfer on transonic turbine nozzle vanes are investigated using a compressible Navier–Stokes code with three low-Reynolds-number k–ε models. The mean-flow and turbulence transport equations are integrated by a four-stage Runge–Kutta scheme. Numerical predictions are compared with the experimental data acquired at Allison Engine Company. An assessment of the performance of various turbulence models is carried out. The two modes of transition, bypass transition and separation-induced transition, are studied comparatively. Effects of blade surface pressure gradients, free-stream turbulence level, and Reynolds number on the blade boundary layer development, particularly transition onset, are examined. Predictions from a parabolic boundary layer code are included for comparison with those from the elliptic Navier–Stokes code. The present study indicates that the turbine external heat transfer, under real engine conditions, can be predicted well by the Navier–Stokes procedure with the low-Reynolds-number k–ε models employed.

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Turbulent Transport in Pin Fin Arrays: Experimental Data and Predictions

Volume 3: Turbo Expo 2005, Parts A and B ◽

10.1115/gt2005-68180 ◽

2005 ◽

Cited By ~ 4

Author(s):

F. E. Ames ◽

L. A. Dvorak

Keyword(s):

Heat Transfer ◽

Fluid Dynamics ◽

Boundary Layers ◽

Fluid Dynamic ◽

Turbulent Transport ◽

Turbulence Models ◽

Reynolds Numbers ◽

Velocity Profiles ◽

Pin Fin ◽

Pin Fin Arrays

The objective of this research has been to experimentally investigate the fluid dynamics of pin fin arrays in order to clarify the physics of heat transfer enhancement and uncover problems in conventional turbulence models. The fluid dynamics of a staggered pin fin array have been studied using hot wire anemometry with both single and x-wire probes at array Reynolds numbers of 3000; 10,000; and 30,000. Velocity distributions off the endwall and pin surface have been acquired and analyzed to investigate turbulent transport in pin fin arrays. Well resolved 3-D calculations have been performed using a commercial code with conventional two-equation turbulence models. Predictive comparisons have been made with fluid dynamic data. In early rows where turbulence is low, the strength of shedding increases dramatically with increasing in Reynolds numbers. The laminar velocity profiles off the surface of pins show evidence of unsteady separation in early rows. In row three and beyond laminar boundary layers off pins are quite similar. Velocity profiles off endwalls are strongly affected by the proximity of pins and turbulent transport. At the low Reynolds numbers, the turbulent transport and acceleration keep boundary layers thin. Endwall boundary layers at higher Reynolds numbers exhibit very high levels of skin friction enhancement. Well resolved 3-D steady calculations were made with several two-equation turbulence models and compared with experimental fluid mechanic and heat transfer data. The quality of the predictive comparison was substantially affected by the turbulence model and near wall methodology.

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Investigation of Leakage Flow and Heat Transfer in a Gas Turbine Blade Tip With Emphasis on the Effect of Rotation

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2008-51215 ◽

2008 ◽

Cited By ~ 2

Author(s):

Dianliang Yang ◽

Xiaobing Yu ◽

Zhenping Feng

Keyword(s):

Heat Transfer ◽

Relative Motion ◽

Turbulence Models ◽

Leakage Flow ◽

Tip Leakage Flow ◽

Blade Height ◽

Tip Leakage ◽

Flow And Heat Transfer ◽

Blade Rotation ◽

Blade Tip

In this paper, numerical methods have been applied to the investigation of the effect of rotation on the blade tip leakage flow and heat transfer. Using the first stage rotor blade of GE-E3 engine high pressure turbine, both flat tip and squealer tip have been studied. The tip gap height is 1% of the blade height, and the groove depth of the squealer tip is 2% of the blade height. Heat transfer coefficient on tip surface obtained by using different turbulence models was compared with experimental results. And the grid independence study was carried out by using the Richardson extrapolation method. The effect of the blade rotation was studied in the following cases: 1) blade domain is rotating and shroud is stationary; 2) blade domain is stationary and shroud is rotating; and 3) both blade domain and shroud are stationary. In this approach, the effects of the relative motion of the endwall, the centrifugal force and the Coriolis force can be investigated respectively. By comparing the results of the three cases discussed, the effects of the blade rotation on tip leakage flow and heat transfer are revealed. It indicated that the main effect of the rotation on the tip leakage flow and heat transfer is resulted from the relative motion of the shroud, especially for the squealer tip blade.

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Improving predictions of heat transfer in indoor environments with eddy viscosity turbulence models

Building Simulation ◽

10.1007/s12273-015-0260-5 ◽

2015 ◽

Vol 9 (2) ◽

pp. 213-220 ◽

Cited By ~ 2

Author(s):

Christian Heschl ◽

Yao Tao ◽

Kiao Inthavong ◽

Jiyuan Tu

Keyword(s):

Heat Transfer ◽

Eddy Viscosity ◽

Turbulence Models ◽

Indoor Environments

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IMPROVING THE FILM COOLING PERFORMANCE OF A TURBINE ENDWALL WITH MULTI-FIDELITY MODELING CONSIDERING CONJUGATE HEAT TRANSFER

Journal of Turbomachinery ◽

10.1115/1.4052018 ◽

2021 ◽

pp. 1-20

Author(s):

Hongyan Bu ◽

Yufeng Yang ◽

Liming Song ◽

Jun Li

Keyword(s):

Heat Transfer ◽

Design Optimization ◽

Film Cooling ◽

Conjugate Heat Transfer ◽

Inlet Temperature ◽

High Fidelity ◽

Cooling Performance ◽

Fine Mesh ◽

Film Cooling Holes ◽

Component Temperature

Abstract The gas turbine endwall is bearing extreme thermal loads with the rapid increase of turbine inlet temperature. Therefore, the effective cooling of turbine endwalls is of vital importance for the safe operation of turbines. In the design of endwall cooling layouts, numerical simulations based on conjugate heat transfer (CHT) are drawing more attention as the component temperature can be predicted directly. However, the computation cost of high-fidelity CHT analysis can be high and even prohibitive especially when there are many cases to evaluate such as in the design optimization of cooling layout. In this study, we established a multi-fidelity framework in which the data of low-fidelity CHT analysis was incorporated to help the building of a model that predicts the result of high-fidelity simulation. Based upon this framework, multi-fidelity design optimization of a validated numerical turbine endwall model was carried out. The high and low fidelity data were obtained from the computation of fine mesh and coarse mesh respectively. In the optimization, the positions of the film cooling holes were parameterized and controlled by a shape function. With the help of multi-fidelity modeling and sequentially evaluated designs, the cooling performance of the model endwall was improved efficiently.

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