Simulation of Film Cooling Heat Transfer and Simulation Improvement With a Modified DES Turbulence Model

2018 ◽  
Author(s):  
Feiyan Yu ◽  
Savas Yavuzkurt
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Cooling System ◽  
Near Field ◽  
Density Ratio ◽  
Computational Cost ◽  
Computational Time ◽  
Spanwise Direction ◽  
Des Model

Modeling the heat transfer characteristics of the highly turbulent flow in gas turbine film cooling is important for better engineering solutions to the film cooling system design. URANS, LES, DES and modified DES models capability in simulating film cooling with a density ratio of 2.0 and blowing ratio of 1.0 are studied in this work. Detailed comparisons of simulation results with experimental data regarding the near-field and far-fields are made. For near field predictions, DES gives decent prediction with a 21.4 % deviation of centerline effectiveness, while LES and URANS have deviation of 33.6% and 51.2% compared to the experimental data. Despite good predictions for near field, DES under predicts the spanwise spreading of counter rotating vortex pair and temperature field, therefore it over predicts the centerline effectiveness in the far field. To compensate for this shortcoming of DES, the eddy viscosity in the spanwise direction is increased to enhance spanwise-diffusion of the cooling jets. The modified DES prediction of overall centerline effectiveness deviates 12.4% from experimental data, while LES, unmodified DES and URANS predictions deviate 10.8%, 31.9% and 46.9%. The modified DES model has adequate predictions of vortices evolutions which URANS modeling lacks and consumes significant less computational time than LES. It can be said that the modified DES model results in satisfactory film cooling modeling with a moderate computational cost and time.

Simulations of Film Cooling Flow Structure and Heat Transfer in the Near Field of Cooling Jets With a Modified DES Model

2019 ◽  
Author(s):  
Feiyan Yu ◽  
Savas Yavuzkurt
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Near Field ◽  
Density Ratio ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Hole ◽  
Film Cooling Holes ◽  
Des Model

Abstract Simulations of film cooling in the near field (x/D < 15) of coolant jets on a flat plate are carried out with detached eddy simulation (DES) and modified DES models. The time-averaged unsteady film cooling effectiveness is compared with experimental data. Both models use two-layer zonal model for near-wall treatment. The near field critical turbulent flow behaviors such as mainstream entrainment, spanwise spreading of counter rotating vortex pair (CRVP), and vortical structure evolutions are predicted and analyzed by DES and modified DES in this study. Modified DES model differs from the DES by implementing an increased eddy viscosity in the spanwise direction to enhance spanwise-diffusion of film cooling jets. Detailed comparisons of DES and modified DES modeling results are made under density ratios of 2.0, 1.6, 1.2 and blowing ratio of 1.0 for a single hole. Modified DES model predicts a wider spanwise spreading of temperature field and film cooling effectiveness. In a comparison of spanwise-averaged film cooling effectiveness with experimental data, DES and modified DES models predict 14.8% and 10.4% deviations under density ratio of 2.0. For density ratio of 1.2, the DES and modified DES results deviate from data 24.5% and 14.7% respectively. Then simulation of film cooling with a three hole domain is also carried out. Instantaneous effectiveness results show that the jets from nearby film cooling holes start to interact with each other before x/D < 10. When the interactions of flow from film cooling holes next to each other are strong, simulations using several cooling holes are meaningful and the current study shows the difference of multi hole and single hole simulations.

Radiative Effectiveness on the Aero- and Thermodynamics in a Highly Thermally Loaded Film Cooling System

2011 ◽  
Author(s):  
Wenping Wang ◽  
Peng Sun ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Heat Transfer ◽  
High Temperature ◽  
Gas Turbine ◽  
Film Cooling ◽  
Cooling System ◽  
Numerical Study ◽  
Discrete Ordinates ◽  
Spanwise Direction ◽  
Inlet Temperature ◽  
Gas Channel

With the increasing of the gas turbine inlet temperature, the radiative heat transfer plays a more important role in the total heat transfer. In this paper, a high temperature test rig has been built to research the radiative effect in high temperature film cooling. The test section is made up of a high temperature hot gas channel and a middle temperature coolant air channel which are separated by a flat plate with a row of film cooling holes. The goal is to analyze the effects of radiation and its interaction between conduction and convection in the internal and film cooling which consider the heat transfer in both gas and solid. Meanwhile, the numerical study on the test cases are also carried out by combining conjugate heat transfer with radiative models. The fluid and solid regions were solved simultaneously. The Discrete Ordinates (DO) model and the Weighted Sum of Gray Gases Model (WSGGM) has been used to solve the radiative transfer equation for the radiation modeling. The results show that the temperature of the plate increase greatly when the radiation is taken into account and the temperature gradient through the plate becomes much larger. The temperature distribution has been changed and become smoother in spanwise direction. The results also indicate that the internal emissivity of the inlet has an influence mainly on the whole temperature of the plate, which suggests that the control of inlet emissivity is a good way for prevent over-high temperature on the first stage gas turbine vane.

scholarly journals Experimental Evaluation of the Density Ratio Effects on the Cooling Performance of a Combined Slot/Effusion Combustor Cooling System

2013 ◽  
Vol 2013 ◽  
pp. 1-14 ◽  
Author(s):  
Antonio Andreini ◽  
Gianluca Caciolli ◽  
Bruno Facchini ◽  
Lorenzo Tarchi
Keyword(s):  
Heat Transfer ◽  
Working Conditions ◽  
Film Cooling ◽  
Cooling System ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Cooling Performance ◽  
Engine Cooling ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

The purpose of this study is to investigate the effects of coolant-to-mainstream density ratio on a real engine cooling scheme of a combustor liner composed of a slot injection and an effusion array with a central dilution hole. Measurements of heat transfer coefficient and adiabatic effectiveness were performed by means of steady-state thermochromic liquid crystals technique; experimental results were used to estimate, through a 1D thermal procedure, the Net Heat Flux Reduction and the overall effectiveness in realistic engine working conditions. To reproduce a representative value of combustor coolant-to-mainstream density ratio, tests were carried out feeding the cooling system with carbon dioxide, while air was used in the main channel; to highlight the effects of density ratio, tests were replicated using air both as coolant and as mainstream and results were compared. Experiments were carried out imposing values of effusion blowing and velocity ratios within a range of typical modern engine working conditions. Results point out the influence of density ratio on film cooling performance, suggesting that velocity ratio is the driving parameter for the heat transfer phenomena; on the other hand, the adiabatic effectiveness is less sensitive to the cooling flow parameters, especially at the higher blowing/velocity ratios.

Investigation on the Leading Edge Film Cooling of Counter-Inclined Cylindrical and Laid-Back Holes With and Without Impingement: Part I — Film Cooling Effectiveness

2018 ◽  
Author(s):  
Qi-ling Guo ◽  
Cun-liang Liu ◽  
Hui-ren Zhu ◽  
Hai-yong Liu ◽  
Rui-dong Wang ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Cylindrical Hole ◽  
Spanwise Direction ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Turbine Vane

Experimental investigation has been performed to study the film cooling characteristics of counter-inclined structures on the turbine vane leading edge. In this paper, four counter-inclined models are measured including cylindrical film holes with and without impingement holes, laid-back film holes with and without impingement holes. A semi-cylinder model is used to model the turbine vane leading edge. Two rows of film holes are located at ±15° on either side of the leading edge model, inclined 90° to the flow direction and 45° to the spanwise direction. Film cooling effectiveness and heat transfer coefficient have been obtained using a transient heat transfer measurement technique with double thermochromic liquid crystals with four blowing ratios ranging from 0.5 to 2 at a 1.0 density ratio. The results show that the film cooling effectiveness decreases with the increase of blowing ratio. No matter cylindrical hole or laid-back hole, the addition of impingement enhances the film cooling effectiveness. Compared with cylindrical hole, laid-back hole produces a better film cooling performance mainly because of stronger lateral momentum. Moreover, the benefits of both adding impingement and exit shaping are more obvious under a large blowing ratio.

scholarly journals Near-Field Simulations of Film Cooling with a Modified DES Model

Inventions ◽  
2020 ◽  
Vol 5 (1) ◽  
pp. 13
Author(s):  
Feiyan Yu ◽  
Savas Yavuzkurt
Keyword(s):  
Film Cooling ◽  
Eddy Viscosity ◽  
Near Field ◽  
Computational Cost ◽  
Vortex Pair ◽  
Anisotropy Ratio ◽  
Detached Eddy Simulation ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Des Model

Modeling the heat transfer characteristics of highly turbulent flow in gas turbine film cooling is important for providing better insights and engineering solutions to the film cooling problem. This study proposes a modified detached eddy simulation (DES) model for better film cooling simulations. First, spatially varying anisotropic eddy viscosity is found from the results of the large eddy simulation (LES) of film cooling. Then the correlation for eddy viscosity anisotropy ratio has been established based on the LES results and is proposed as the modification approach for the DES model. The modified DES model has been tested for the near-field film cooling simulations under different blowing ratios. Detailed comparisons of the centerline and 2D film cooling effectiveness indicate that the modified DES model enhances the spanwise spreading of the temperature field. The DES model leads to deviations of 62.4%, 39.8%, and 33.5% from the experimental centerline effectiveness under blowing ratios of 0.5, 1.0, and 1.5, respectively, while the modified DES reduces the deviations to 51.5%, 26.7%, and 28.9%. The modified DES model provides a promising approach for film cooling numerical simulations. It embraces the advantage of LES in resolving detailed vortical structure dynamics with a moderate computational cost. It also significantly improves the original DES model on the spanwise counter rotating vortex pair (CRVP) spreading, mixing, and effectiveness prediction.

Conjugate Heat Transfer Predictions of Effusion Cooling: The Influence of the Coolant Jet-Flow Direction on the Cooling Effectiveness

2012 ◽  
Author(s):  
H. I. Oguntade ◽  
G. E. Andrews ◽  
A. D. Burns ◽  
D. B. Ingham ◽  
M. Pourkashanian
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Mass Flow ◽  
Film Cooling ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Unexpected Result ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hot Gas

Effusion cooling of a flat wall was investigated using conjugate heat transfer CFD. The main variable investigated was the angle of the coolant jets relative to the crossflow. Experimental data for the overall cooling effectiveness using a metal effusion cooled wall was modelled for an X/D of 4.65, coolant to crossflow density ratio of 2.56, ten rows of holes in the crossflow direction and a blowing ratio M of 0.2–3.27 or mass flow per surface area, G, of 0.088–1.47 kg/sm2. The experimental data for 90° normal injection was modelled and then the influence of injecting each effusion hole 30° downstream and 150° downstream (or 30° upstream) was predicted. The coupled thermal mixing between the hot-gas and coolant jets and the heat transfer within the effusion walls were modelled using the ANSYS FLUENT code. The computational results of the overall cooling effectiveness of the validation case was of the order of about 8–12% less than the experimental data but the trend of the results was well predicted. A methane tracer gas was added to the coolant air and this enabled the adiabatic cooling effectiveness to be predicted as well as the overall cooling effectiveness. At high blowing ratios, the co-flow inclined and normal jets were characterised with kidney-shaped pair vortices which degrade the adiabatic film cooling effectiveness. The counteraction of the fluid dynamics between the oppose-flow jets and hot-gas momentum prevents the formation of the kidney-shaped pair vortices with the usage of opposed-flow wall. The oppose-flow jet was shown to be the best effusion cooling design with the greatest transverse spread of the film cooling at high blowing ratios. This was an unexpected result that has very few previous studies. The results show that significant reductions in coolant mass flow rate for the same wall temperature could be achieved or lower wall temperatures for the same coolant mass flow.

Conjugate Heat Transfer and Film Cooling of a Multi-Stage Cooling Scheme

2008 ◽  
Author(s):  
M. Ghorab ◽  
S. I. Kim ◽  
I. Hassan
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Gas Turbines ◽  
Conjugate Heat Transfer ◽  
Density Ratio ◽  
Design Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Multi Stage ◽  
Internal Gap

Cooling techniques play a key role in improving efficiency and power output of modern gas turbines. The conjugate technique of film and impingement cooling schemes is considered in this study. The Multi-Stage Cooling Scheme (MSCS) involves coolant passing from inside to outside turbine blade through two stages. The first stage; the coolant passes through first hole to internal gap where the impinging jet cools the external layer of the blade. Finally, the coolant passes through the internal gap to the second hole which has specific designed geometry for external film cooling. The effect of design parameters, such as, offset distance between two-stage holes, gap height, and inclination angle of the first hole, on upstream conjugate heat transfer rate and downstream film cooling effectiveness performance are investigated computationally. An Inconel 617 alloy with variable properties is selected for the solid material. The conjugate heat transfer and film cooling characteristics of MSCS are analyzed across blowing ratios of Br = 1 and 2 for density ratio, 2. This study presents upstream wall temperature distributions due to conjugate heat transfer for different gap design parameters. The maximum film cooling effectiveness with upstream conjugate heat transfer is less than adiabatic film cooling effectiveness by 24–34%. However, the full coverage of cooling effectiveness in spanwise direction can be obtained using internal cooling with conjugate heat transfer, whereas adiabatic film cooling effectiveness has narrow distribution.

Combined Experimental and CFD Study of a HP Blade Multi-Pass Cooling System

2009 ◽  
Author(s):  
D. Jackson ◽  
P. Ireland ◽  
B. Cheong
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Cooling System ◽  
Detailed Comparison ◽  
Bulk Temperature ◽  
Internal Cooling ◽  
3 Dimensional ◽  
Turbine Cooling ◽  
Cooling Hole ◽  
The Difference

Progress in the computing power available for CFD predictions now means that full geometry, 3 dimensional predictions are now routinely used in internal cooling system design. This paper reports recent work at Rolls-Royce which has compared the flow and htc predictions in a modern HP turbine cooling system to experiments. The triple pass cooling system includes film cooling vents and inclined ribs. The high resolution heat transfer experiments show that different cooling performance features are predicted with different levels of fidelity by the CFD. The research also revealed the sensitivity of the prediction to accurate modelling of the film cooling hole discharge coefficients and a detailed comparison of the authors’ computer predictions to data available in the literature is reported. Mixed bulk temperature is frequently used in the determination of heat transfer coefficient from experimental data. The current CFD data is used to compare the mixed bulk temperature to the duct centreline temperature. The latter is measured experimentally and the effect of the difference between mixed bulk and centreline temperature is considered in detail.

A Technique for Processing Transient Heat Transfer, Liquid Crystal Experiments in the Presence of Lateral Conduction

2004 ◽  
Vol 126 (2) ◽  
pp. 247-258 ◽  
Author(s):  
John P. C. W. Ling ◽  
Peter T. Ireland ◽  
Lynne Turner
Keyword(s):  
Heat Transfer ◽  
Liquid Crystal ◽  
Film Cooling ◽  
Cooling System ◽  
Local Heat Transfer ◽  
Local Heat ◽  
Three Dimensions ◽  
Transient Heat Transfer ◽  
Adiabatic Wall ◽  
Full Intensity

New techniques for processing transient liquid crystal heat transfer experiment have been developed. The methods are able to measure detailed local heat transfer coefficient and adiabatic wall temperature in a three temperature system from a single transient test using the full intensity history recorded. Transient liquid crystal processing methods invariably assume that lateral conduction is negligible and so the heat conduction process can be considered one-dimensional into the substrate. However, in regions with high temperature variation such as immediately downstream of a film-cooling hole, it is found that lateral conduction can become significant. For this reason, a procedure which allows for conduction in three dimensions was developed by the authors. The paper is the first report of a means of correcting data from the transient heat transfer liquid crystal experiments for the effects of significant lateral conduction. The technique was applied to a film cooling system as an example and a detailed uncertainty analysis performed.

Endwall Heat Transfer and Cooling Performance of a Transonic Turbine Vane with Upstream Injection Flow

2021 ◽  
pp. 1-24
Author(s):  
Zhigang LI ◽  
Bo Bai ◽  
Jun Li ◽  
Shuo Mao ◽  
Wing Ng ◽  
...  
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Gas Temperature ◽  
Blow Down ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Injection Flow ◽  
Coolant Injection ◽  
Exit Mach Number

Abstract Detailed experimental and numerical studies on endwall heat transfer and cooling performance with coolant injection flow through upstream discrete holes is presented in this paper. High resolution heat transfer coefficient (HTC) and adiabatic film cooling effectiveness values were measured using a transient infrared thermography technique on an axisymmetric contoured endwall. The tests were performed in a transonic linear cascade blow-down wind tunnel facility. Conditions were representative of a land-based power generation turbine with exit Mach number of 0.85 corresponding to exit Reynolds number of 1.5 × 106, based on exit condition and axial chord length. A high turbulence level of 16% with an integral length scale of 3.6%P was generated using inlet turbulence grid to reproduce the typical turbulence conditions in real turbine. Low temperature air was used to simulate the typical coolant-to-mainstream condition by controlling two parameters of the upstream coolant injection flow: mass flow rate to determine the coolant-to-mainstream blowing ratio (BR = 2.5, 3.5), and gas temperature to determine the density ratio (DR = 1.2). To highlight the interactions between the upstream coolant flow and the passage secondary flow combined with the influence on the endwall heat transfer and cooling performance, a comparison of CFD predictions to experimental results was performed by solving steady-state Reynolds-Averaged Navier-Stokes (RANS) using the commercial CFD solver ANSYS Fluent V.15.

Sign in / Sign up

Export Citation Format

Share Document