Calculation of Film-Cooling Effectiveness and Aerodynamic Losses Using DES/SAS and RANS Methods and Compared With Experimental Results

2016 ◽  
Author(s):  
Xiao-Chun Lin ◽  
Jian-Jun Liu ◽  
Bai-Tao An
Keyword(s):  
Film Cooling ◽  
Numerical Models ◽  
Experimental Results ◽  
Mixing Process ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Rans Models ◽  
Les Model ◽  
Aerodynamic Losses

When used to simulate the film-cooling internal flow, RANS models generally over predicted the mixing process of the coolant and the mainstream in streamwise, and under predicted the distribution of the coolant in spanwise. Compared with an anisotropic amendment of the RANS model, the transient LES model was shown to be universally effective to obtain more accurate prediction on mixing process. Considering the giant computing resources consumption of the LES model, this paper employs DES (Detached Eddy Simulation) SAS (Scale-Adaptive Simulation) and RANS models to study the film cooling mixing process between the coolant and the mainstream. Vortex shedding phenomenon and the detailed structure were studied, and the mechanism of shedding was exposed. Film cooling effectiveness and aerodynamic losses of simulation results were compared with those of experimental results. Result discrepancies between numerical models and experiment were discussed. It showed that DES and SAS model was more accurate than RANS on the prediction of mixing process in the spanwise and in the height directions.

A Brief Review on Numerical Studies on Film Cooling Effectiveness

2016 ◽  
Vol 852 ◽  
pp. 699-706
Author(s):  
Prakhar Jindal ◽  
Shubham Agarwal ◽  
R.P. Sharma
Keyword(s):  
Film Cooling ◽  
Complex Analysis ◽  
Numerical Models ◽  
The Body ◽  
Coolant Fluid ◽  
Future Research ◽  
Cooling Systems ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Trade Offs

Film cooling is employed for effective cooling in nozzles and combustion chambers using a spray of coolant fluid in the mainstream flow to cool the body. Experimental analysis was performed elaborately in the past years to get an exact analysis of film cooling effectiveness with different parameters. This approach was however discouraged due to its high cost and time consumption. Recently, researchers switched to the use of numerical platforms for investigation of complex film cooling systems. The paper discusses in detail the numerical analysis of the film cooling systems done so far and the numerical models employed for such a complex analysis along with the advantages and trade-offs of such a numerical approach. This study was carried out to extend database knowledge about the numerical film cooling for its various applications. Therefore, an appropriate cooling technique should be designed to protect these parts. Film cooling is one of the most effective external cooling methods. Various numerical film cooling techniques presented in the literature have been investigated. Moreover, challenges and future directions of numerical film cooling techniques have been reviewed and presented in this paper. The aim of this review is to summarize recent development in research on film cooling techniques and attempt to identify some challenging issues that need to be solved for future research.

Geometrical Optimization and Experimental Validation of a Tripod Film Cooling Hole With Asymmetric Side Holes

2014 ◽  
Author(s):  
Zhongran Chi ◽  
Chang Han ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Experimental Results ◽  
Geometrical Parameters ◽  
Vortex System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Optimum Configuration ◽  
Optimization Study ◽  
Cooling Hole

A tripod cylindrical film hole with asymmetric side holes is studied numerically and experimentally on a flat plate for higher film cooling effectiveness. Firstly, the influences of geometrical parameters are studied and the optimum configurations of the asymmetric tripod hole are found in a DoE optimization study based on an improved numerical model for film cooling prediction, in which more than one hundred 3D CFD simulations are carried out. Then one optimum configuration of the asymmetric tripod hole is examined experimentally using pressure-sensitive paint (PSP) measurements, and compared against the experimental results of the simple cylindrical film hole and a well-designed shaped film hole. The flow and heat transfer characteristics of the asymmetric tripod holes were explored from the DoE results. The side holes can form a shear vortex system or an anti-kidney vortex system when proper spanwise distances of them are adopted, which laterally transports the coolant and form a favorable coolant coverage. According to the experimental results, the cooling performance of the optimized asymmetric tripod hole is significantly better than that of the simple cylindrical hole, especially at high blowing ratios. And the optimized asymmetric tripod hole can provide almost the same or even higher film cooling effectiveness on the flat plate compared with the shaped hole in the same flow conditions.

Assessment of URANS and DES for Prediction of Leading Edge Film Cooling

2011 ◽  
Vol 134 (3) ◽  
Author(s):  
Toshihiko Takahashi ◽  
Ken-ichi Funazaki ◽  
Hamidon Bin Salleh ◽  
Eiji Sakai ◽  
Kazunori Watanabe
Keyword(s):  
Turbulence Model ◽  
Film Cooling ◽  
Turbulence Modeling ◽  
Turbine Blades ◽  
Leading Edge ◽  
Vortex Structures ◽  
Temperature Fields ◽  
Detached Eddy Simulation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness

This paper describes the assessment of CFD simulations for the film cooling on the blade leading edge with circular cooling holes in order to contribute durability assessment of the turbine blades. Unsteady RANS applying a k-ε-v2-f turbulence model and the Spalart and Allmaras turbulence model and detached-eddy simulation (DES) based on the Spalart and Allmaras turbulence model are addressed to solve thermal convection. The CFD calculations were conducted by simulating a semicircular model in the wind tunnel experiments. The DES and also the k-ε-v2-f model evaluate explicitly the unsteady fluctuation of local temperature by the vortex structures, so that the predicted film cooling effectiveness is comparatively in agreement with the measurements. On the other hand, the predicted temperature fields by the Spalart and Allmaras model are less diffusive than the DES and the k-ε-v2-f model. In the present turbulence modeling, the DES only predicts the penetration of main flow into the film cooling hole but the Spalart and Allmaras model is not able to evaluate the unsteadiness and the vortex structures clearly, and overpredict film cooling effectiveness on the partial surface.

Film Cooling From Circular and Elliptical Exit Shaped Holes With Sister Hole Influence

2013 ◽  
Author(s):  
Siavash Khajehhasani ◽  
B. A. Jubran
Keyword(s):  
Film Cooling ◽  
Experimental Results ◽  
Considerable Decrease ◽  
Cylindrical Pipe ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
The Common ◽  
Shaped Hole ◽  
Lift Off ◽  
Inclined Angle

In traditional film cooling configuration, coolant is injected through a cylindrical pipe with an inclined angle (0<α<90), which results in an elliptical exit shaped hole (EESH) at the blade surface. The present study makes use of an elliptical injection coolant pipe that leads to a circular exit shaped hole (CESH). The film cooling effectiveness and the associated flow for both cases of circular and elliptical shaped holes are numerically investigated. A comparison between the predicted results and the available experimental results from the literature for blowing ratios of M = 0.5 and 1, clearly indicated a better agreement with the experimental results when the realizable k-ε model was used. Further, the results indicate that the circular exit shaped hole improves the centerline and laterally averaged adiabatic effectiveness, particularly, at a higher bowing ratio of 1. The analysis of the vortex generation downstream of the jet for both exit shaped holes, shows a considerable decrease in the jet lift-off where the coolant flow tends to adhere more to the surface and hence, provides a better film cooling protection for the circular exit shaped hole, in comparison with the common elliptical exit shaped hole. The influence of sister holes on film cooling performance tends to be more effective with circular exit shaped hole than that with elliptical exit shaped hole.

Showerhead Film Cooling Performance of a Transonic Turbine Vane at High Freestream Turbulence (Tu = 16%): 3-D CFD and Comparison With Experiment

2008 ◽  
Author(s):  
Hong Wu ◽  
S. Nasir ◽  
W. F. Ng ◽  
H. K. Moon
Keyword(s):  
Nusselt Number ◽  
Mach Number ◽  
Film Cooling ◽  
Experimental Results ◽  
Suction Surface ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Favorable Pressure Gradient ◽  
Turbine Vane

The main objective of the study reported here is to use 3-D CFD to calculate and explain adiabatic film cooling effectiveness and Nusselt number distributions downstream of the showerhead film cooling rows of a turbine vane at high freestream turbulence and realistic exit Reynolds number/Mach number condition. The paper discusses a three-simulations technique to calculate vane surface recovery temperature, adiabatic wall temperature, and surface Nusselt number to completely characterize film cooling performance in a high speed flow. The RANS based ν2-f turbulence model, originally suggested by Durbin [1], is used in all numerical predictions. The vane midspan numerical calculations are compared with the experimental results obtained with the showerhead film cooled vane instrumented with single-sided platinum thin film gauges at the midspan and arranged in a two-dimensional, linear cascade in a heated, transonic, blow-down wind tunnel. Exit Mach number of Mex = 0.76—corresponding to exit Reynolds numbers based on vane chord of 1.1 × 106—was tested with an inlet free stream turbulence intensity (Tu) of 16% and an integral length scale normalized by vane pitch (Λx/P) of 0.23. A showerhead cooling scheme with five rows of cooling holes was tested at blowing ratios of BR = 0 and 1.5, and a density ratio of DR = 1.3. CFD predictions performed with experiment-matched boundary conditions show an overall good trend agreement with experimental adiabatic film cooling effectiveness and Nusselt number distributions downstream of the showerhead film cooling rows of the vane. For the experimental data, the primary effects of coolant injection are to augment Nusselt number and reduce adiabatic wall temperature downstream of the injection on the vane surface as compared to no film injection case (BR = 0) at Mex = 0.76. Similar to experimental results, the adiabatic film cooling effectiveness prediction on the suction surface at BR = 1.5 is found to be influenced by favorable pressure gradient due to Mach number through changes in local adiabatic wall and recovery temperature. The Nusselt number prediction on the suction surface shows a peak and a valley downstream of the film cooling rows in a favorable pressure gradient region for both tested blowing ratio conditions. This trend is also observed in the experimental results.

LES Study of the Effects of Oscillations in the Main Flow on Film Cooling

2020 ◽  
Author(s):  
Seung Il Baek ◽  
Joon Ahn
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Velocity Profiles ◽  
Main Flow ◽  
Experimental Results ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Eddy Simulation ◽  
Sinusoidal Oscillations

Abstract The effects of sinusoidal oscillations in the main flow on film cooling in the gas turbine were investigated by Large Eddy Simulation (LES). The film cooling flow fields for the sinusoidal oscillation of 32 Hz in the mainstream from a cylindrical hole inclined by 35° to a flat plate at average blowing ratio of M = 0.5 were numerically simulated. The LES results were compared to the experimental data from Seo, Lee and Ligrani (1998), Jung, Lee and Ligrani (2001) and Reynolds-Averaged Navier-Stokes (RANS) results. The experimental results showed that if the oscillation frequency in the main flow was increased, the adiabatic film cooling effectiveness was decreased. The credibility of the LES results relative to the experimental data was demonstrated by the comparison of time-averaged adiabatic film cooling effectiveness, time and phase-averaged temperature contours, contours of Q-criterion, time-averaged velocity profiles, and time and phase-averaged Urms profiles with the RANS results. The adiabatic film cooling effectiveness by LES model showed a good match to the experimental data, while RANS results highly over-predict the centerline effectiveness. Also, the LES results showed more consistent with the experimental data for the time-averaged and phase-averaged temperature contours, time-averaged velocity profiles and time and phase-averaged Urms profiles than the RANS results. RANS did not predict the peak generated by the jet penetration exactly and Urms profiles obtained by RANS approach was much smaller compared to the experimental results. Paper will discuss these results in detail.

Geometrical Optimization and Experimental Validation of a Tripod Film Cooling Hole With Asymmetric Side Holes

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Zhongran Chi ◽  
Jing Ren ◽  
Hongde Jiang ◽  
Shusheng Zang
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Experimental Results ◽  
Geometrical Parameters ◽  
Vortex System ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Optimum Configuration ◽  
Optimization Study ◽  
Cooling Hole

A tripod cylindrical film hole with asymmetric side holes is studied numerically and experimentally on a flat plate for higher film cooling effectiveness. First, the influences of geometrical parameters are studied and the optimum configurations of the asymmetric tripod hole are found in a design of experiments (DoE) optimization study based on an improved numerical model for film cooling prediction, in which more than 100 3D computational fluid dynamics (CFD) simulations are carried out. Then, one optimum configuration of the asymmetric tripod hole is examined experimentally using pressure-sensitive paint (PSP) measurements and compared to the experimental results of the simple cylindrical film hole and a well-designed shaped film hole. The flow and heat transferring characteristics of the asymmetric tripod holes were explored from the DoE results. The side holes can form a shear vortex system or an antikidney vortex system when proper spanwise distances between them are adopted, which laterally transports the coolant and form a favorable coolant coverage. According to the experimental results on flat plate, the optimal configuration of the asymmetric tripod hole is significantly better than cylindrical hole, especially at high blowing ratios. Furthermore, it can provide equivalent or even higher film cooling effectiveness than a well-designed shaped hole.

Passive Shroud Cooling Concepts for HP Turbines: CFD Based Design Approach

2006 ◽  
Author(s):  
E. Janke ◽  
F. Haselbach ◽  
C. Whitney ◽  
V. Kanjirakkad ◽  
R. Thomas ◽  
...  
Keyword(s):  
Film Cooling ◽  
High Speed ◽  
Flow Region ◽  
Design Approach ◽  
Inlet Temperature ◽  
Operational Parameters ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Secondary Air ◽  
Aerodynamic Losses

One option to improve the cycle efficiency of current state-of-the-art aero engines is to increase the turbine inlet temperature. Since this temperature is above the melting temperature for the alloys utilised in the turbine component already today, efficient cooling methods must be developed that consider both aerodynamic and aerothermal aspects of cooling. Here, the goal is to extract as little as possible secondary air from the main hot gas cycle for cooling and to use this coolant then aerodynamically and aerothermally as efficient as possible. The paper to be presented documents a CFD based design approach that lead to a new passive shroud cooling concept and the definition of its operational parameters. By using a simple one dimensional method [10] for predicting the aerodynamic losses resulting from such a cooling configuration in connection with 3d Navier-Stokes solvers (RANS) for predicting film cooling effectiveness contours on the rotor shroud surfaces, the new cooling configuration was developed. The concept was then tested and confirmed experimentally as documented in more detail in Part 2 of this paper. It is noted that only 70% of the coolant mass flow required for the current configuration was used for the new concept whereas the aerodynamic efficiency measured remained nearly constant. Improving upon existing passive shroud cooling systems where the coolant is injected directly into the labyrinth of the shroud, the new approach comprises cooling holes that inject the coolant upstream of the labyrinth and through the stator platform into the main passage flow. Here, it is important that the bulk of the coolant is placed below the dividing streamlines between main passage flow and labyrinth flow. Thereby, it can be achieved that the major part of the coolant indeed reaches the thermally loaded target surfaces on the shroud bottom at various axial gaps due to different operating points of the turbine. Besides the improved film-cooling effectiveness measured, the second important aspect of the new concept is the achievement of as small as possible additional aerodynamic losses due to coolant ejection into a high speed flow region. It will be shown that both goals can be achieved by the new concept. Furthermore, CFD results on film-cooling performance and aerodynamic losses will be shown and compared with experimental data.

Detached Eddy Simulation of Film Cooling Performance on the Trailing Edge Cut-Back of Gas Turbine Airfoils

2005 ◽  
Author(s):  
P. Martini ◽  
A. Schulz ◽  
H.-J. Bauer ◽  
C. F. Whitney
Keyword(s):  
Film Cooling ◽  
Back Surface ◽  
Pressure Side ◽  
Mixing Process ◽  
Transfer Coefficients ◽  
Trailing Edge ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Turbine Airfoils

The present study deals with the unsteady flow simulation of trailing edge film cooling on the pressure side cut-back of gas turbine airfoils. Before being ejected tangentially on the inclined cut-back surface, the coolant air passes a partly converging passage that is equipped with turbulators such as pin fins and ribs. The film mixing process on the cut-back is complicated. In the near slot region, due to the turbulators and the blunt pressure side lip, turbulence is expected to be anisotropic. Furthermore, unsteady flow phenomena like vortex shedding from the pressure side lip might influence the mixing process (i.e. the film cooling effectiveness on the cut-back surface). In the current study, three different internal cooling designs are numerically investigated starting from the steady RaNS solution, and ending with unsteady detached eddy simulations (DES). Blowing ratios M = 0.5; 0.8; 1.1 are considered. To obtain both, film cooling effectiveness as well as heat transfer coefficients on the cut-back surface, the simulations are performed using adiabatic and diabatic wall boundary conditions. The DES simulations give a detailed insight into the unsteady film mixing process on the trailing edge cut-back, which is indeed influenced by vortex shedding from the pressure side lip. Furthermore, the time averaged DES results show very good agreement with the experimental data in terms of film cooling effectiveness and heat transfer coefficients.

scholarly journals Kajian Numerik Efektifitas Film Cooling pada Sudu Turbin Gas

ROTASI ◽  
2019 ◽  
Vol 21 (1) ◽  
pp. 10
Author(s):  
Agus Jamaldi ◽  
Marwan Effendy
Keyword(s):  
Film Cooling ◽  
Discharge Coefficient ◽  
Detached Eddy Simulation ◽  
Trailing Edge ◽  
Adiabatic Wall ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Pin Fin ◽  
Eddy Simulation ◽  
Shedding Frequency

Penelitian ini bertujuan untuk mengevaluasi penggunaan model turbulensi Detached Eddy Simulation Spallart-Almaras (DES-SA) pada studi numerik tentang sistem pendinginan trailing edge (TE) pada sudu turbin gas. Sebuah desain TE cutback cooling dengan susunan staggered pin-fin dipilih sebagai spesimen pengujian berbasis simulasi. Tiga parameter penting seperti discharge coefficient (CD), adiabatic film cooling effectiveness (ηaw), dan shedding frequency (fs) menjadi fokus utama dalam penyelidikan kinerja sistem pendinginan TE sudu turbin gas. Penelitian dilakukan pada variasi tiga blowing ratios (M) yaitu 0,5; 0,8; dan 1,1. Hasil riset menunjukkan bahwa nilai CD yang diperoleh dari hasil simulasi memiliki kesesuaian trend jika dibandingkan dengan data peneliti terdahulu, dimana nilai CD sedikit meningkat seiring dengan M yang semakin besar. Penyelidikan terkait ηaw yang terjadi pada permukaan adiabatic wall menunjukkan bahwa nilainya konsisten dengan data penelitian yang terdahulu, baik secara eksperimen maupun simulasi. Frekuensi aliran vorteks (fs) berturut-turut 2043, 2323, dan 1976 Hz untuk masing-masing blowing ratios  0,5; 0,8; dan 1,1.

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