scholarly journals Computations of Discrete-Hole Film Cooling Over Flat and Convex Surfaces

1998 ◽  
Author(s):  
Y.-L. Lin ◽  
T. I-P. Shih
Keyword(s):  
Film Cooling ◽  
Convex Surface ◽  
Computational Study ◽  
Density Ratio ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Wall Functions ◽  
Film Cooling Effectiveness ◽  
Sst Turbulence Model ◽  
Film Cooling Holes

Computations were performed to investigate the three-dimensional flow and heat transfer about a flat surface and a convex surface cooled by jets, injected from a plenum through one row of film-cooling holes inclined at 35° with a density ratio of 1.6 and mass flux ratios of 0.5 and 1.0. The focus is on understanding how the mainflow distorts the jets issuing from the film-cooling holes and how the resulting interactions affect film cooling effectiveness and temperature distribution. Results are presented for the surface adiabatic effectiveness, normalized temperature, velocity vector field, and contours of the vorticity magnitude. The computed results for the surface effectiveness on a flat plate were compared with experimental data, and reasonably good agreements were obtained. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy closed by a low Reynolds number k-ω/SST turbulence model (i.e., wall functions were not used). Solutions were generated by a cell-centered finite-volume method that uses second-order accurate flux-difference splitting of Roe, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids. In the computations, the flow is resolved not just in the cooling-jet/mainflow interaction region, but also inside the film-cooling holes and in the plenum.

scholarly journals Heat Transfer on a Film-Cooled Rotating Blade

1999 ◽  
Author(s):  
Vijay K. Garg
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Three Dimensional ◽  
Leading Edge ◽  
Tip Clearance ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

A multi-block, three-dimensional Navier-Stokes code has been used to compute heat transfer coefficient on the blade, hub and shroud for a rotating high-pressure turbine blade with 172 film-cooling holes in eight rows. Film cooling effectiveness is also computed on the adiabatic blade. Wilcox’s k-ω model is used for modeling the turbulence. Of the eight rows of holes, three are staggered on the shower-head with compound-angled holes. With so many holes on the blade it was somewhat of a challenge to get a good quality grid on and around the blade and in the tip clearance region. The final multi-block grid consists of 4784 elementary blocks which were merged into 276 super blocks. The viscous grid has over 2.2 million cells. Each hole exit, in its true oval shape, has 80 cells within it so that coolant velocity, temperature, k and ω distributions can be specified at these hole exits. It is found that for the given parameters, heat transfer coefficient on the cooled, isothermal blade is highest in the leading edge region and in the tip region. Also, the effectiveness over the cooled, adiabatic blade is the lowest in these regions. Results for an uncooled blade are also shown, providing a direct comparison with those for the cooled blade. Also, the heat transfer coefficient is much higher on the shroud as compared to that on the hub for both the cooled and the uncooled cases.

Systematic Study on the Fluid Dynamical Behaviour of Streamwise and Laterally Inclined Jets in Crossflow

1997 ◽  
Author(s):  
R.-D. Baier ◽  
W. Koschel ◽  
K.-D. Broichhausen ◽  
G. Fritsch
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Large Scale ◽  
Computational Study ◽  
Dynamical Behaviour ◽  
Temperature Fields ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Film Cooling Holes

The design of discrete film cooling holes for gas turbine airfoil applications is governed by a number of parameters influencing both their aerodynamic and thermal behaviour. This numerical and experimental study focuses on the marked differences between film cooling holes with combined streamwise and lateral inclination and film cooling holes with streamwise inclination only. The variation in the blowing angle was chosen on a newly defined and physically motivated basis. High resolution low speed experiments on a large scale turbine airfoil gave insights particularly into the intensified mixing process with lateral ejection. The extensive computational study is performed with the aid of a 3D block-structured Navier-Stokes solver incorporating a low-Reynolds-number k-ε turbulence model. Special attention is paid to mesh generation as a precondition for accurate high-resolution results. The downstream temperature fields of the jets show reduced spanwise variations with increasing lateral blowing angle; these variations are quantified for a comprehensive variety of configurations in terms of adiabatic film cooling effectiveness.

scholarly journals Computations of Film Cooling From Holes With Struts

1999 ◽  
Author(s):  
T. I-P. Shih ◽  
Y.-L. Lin ◽  
M. K. Chyu ◽  
S. Gogineni
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Three Dimensional ◽  
Protective Layer ◽  
Navier Stokes ◽  
Time Stepping ◽  
Cooling Hole ◽  
A Cell ◽  
Volume Method ◽  
Film Cooling Holes

Computations were performed to study the three-dimensional flow and heat transfer on a flat plate cooled by jets, injected from a plenum through one row of film-cooling holes in which each hole is fitted with a strut in the form of a circular cylinder. Three different configurations of the film-cooling hole were investigated: without strut, with streamwise strut, and with spanwise strut. For all configurations, the film-cooling holes are inclined at 35°, and the coolant-to-mainflow density and mass-flux ratios are 1.6 and 0.5, respectively. The focus of this study is to understand how struts in holes affect film cooling jets and their interactions with the mainflow in forming a protective layer of cooler fluid over the plate. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence was modeled by a low Reynolds number k-ω closure known as the shear-stress-transport (SST) model. Solutions were generated by a cell-centered finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters, multigrid acceleration of a diagonalized ADI scheme with local time stepping, and patched/overlapped structured grids. In the computations, the flow is resolved not just in the cooling-jet/mainflow interaction region, but also inside the film-cooling holes and in the plenum. Computed results for adiabatic effectiveness for the case without struts were compared with experimental data, and reasonably good agreements were obtained.

Numerical Investigation of Scoop Effect on Film Cooling for Cylindrical Inclined Hole

2017 ◽  
Author(s):  
Yongbin Ji ◽  
Prashant Singh ◽  
Srinath V. Ekkad ◽  
Shusheng Zhang
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Sst Turbulence Model ◽  
Cooling Behavior ◽  
Length To Diameter Ratio

Film cooling behavior of a single cylindrical hole inclined at an angle of 35° with respect to a flat surface is numerically predicted in this study. Adiabatic film cooling effectiveness has been presented to evaluate the influence of the scoop placed on the coolant entry side. The effect of blowing ratio (0.65, 1, 1.5 and 2) and the length-to-diameter ratio (1.7 and 4.4) are examined. Three-dimensional Reynolds-averaged Navier-Stokes analysis with SST turbulence model is used for the computations. It has been found that both centerline and laterally averaged adiabatic film cooling effectiveness are enhanced by the scoop and the enhancement increases with the blowing ratio in the investigated range of variables. The scoop was more effective for the higher length-to-diameter ratio cases (L/D = 4.4) because of better velocity distribution at the film hole exit, which makes coolant reattach at a more upstream location after blowing off from the wall.

Improved Film Cooling Effectiveness by Placing a Vortex Generator Downstream of Each Hole

2008 ◽  
Author(s):  
David L. Rigby ◽  
James D. Heidmann
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Vortex Generator ◽  
Vortex Pair ◽  
Navier Stokes ◽  
Dramatic Improvement ◽  
Freestream Velocity ◽  
Film Cooling Effectiveness ◽  
Cooling Hole

Calculations are presented demonstrating the effect of placing a delta vortex generator downstream of a film cooling hole. The effects of blowing ratio, density ratio, and spanwise pitch are included in the study. Flow over a flat plate with film cooling holes oriented at a 30 degree angle was investigated. The Reynolds numbers based on the freestream velocity and the hole diameter was 11,300. The simulation was performed using the Glenn-HT code, a full three-dimensional Navier-Stokes solver using the Wilcox k-ω turbulence model. A structured multi-block grid was used with approximately one million cells, and average y+ values on the order of unity. Local and span averaged effectiveness are presented. Analysis and visualization of the flow are presented as well as a discussion on the mechanisms which contribute to the dramatic improvement in effectiveness. The results demonstrate that the delta vortex generator was able to annihilate the up-wash vortex pair produced by the film hole and produce a down-wash pair downstream.

A Comparative Study of Film Cooling Effectiveness on a Flat Plate With Adiabatic and Conjugate Conditions for Different Hole Shapes

2012 ◽  
Author(s):  
P. M. Dileep Chandran ◽  
Paresh Halder ◽  
Rajesh Kumar Panda ◽  
B. V. S. S. S. Prasad
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Density Ratio ◽  
Cross Flow ◽  
Complex Flow ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Significant Difference ◽  
Sst Turbulence Model ◽  
Lift Off

A computational study is carried out for comparison of the effectiveness of film cooling through holes of different shapes: cylindrical, shaped, trenched cylindrical and trenched shaped hole. Both adiabatic and conjugate wall thermal condition with various blowing ratios (0.6 to 1.4) are considered for the investigation. The coolant-to-mainstream density ratio and temperature ratio are maintained at 1.6 and 0.625 respectively. The κ-ω SST turbulence model is used for computation. The complex flow structures within the film hole, the exit and in the interaction zone of jet with cross flow are reported. Among the configurations studied, the shaped and trenched shaped holes have shown smaller jet lift off and uniform coolant coverage in both lateral and streamwise directions. Further, the results showed a significant difference in the indicated values of centerline surface temperature and effectiveness with the adiabatic and the conjugate conditions; the conjugate values being much lower but more uniform.

Control of Secondary Flows in a Turbine Nozzle Guide Vane by Endwall Contouring

2000 ◽  
Author(s):  
T. I-P. Shih ◽  
Y.-L. Lin ◽  
T. W. Simon
Keyword(s):  
Film Cooling ◽  
Computational Study ◽  
Guide Vane ◽  
Three Dimensional ◽  
Secondary Flows ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Nozzle Guide Vane ◽  
A Cell ◽  
Nozzle Guide

Computations were performed to study the three-dimensional flow and temperature distribution in a nozzle guide vane that has one flat and one contoured endwall with and without film cooling injected from two slots, one on each endwall located just upstream of the airfoil. For the contoured endwall, two locations of the same contouring were investigated, one with all contouring upstream of the airfoil and another with the contouring starting upstream of the airfoil and continuing through the airfoil passage. Results obtained show that when the contouring is all upstream of the airfoil, secondary flows on both the flat and the contoured endwalls are similar in magnitude. When the contouring starts upstream of the airfoil and continues through the airfoil passage, secondary flows on the contoured endwall are markedly weaker than those on the flat endwall. With weaker secondary flows on the contoured endwall, film-cooling effectiveness there is greatly improved. This computational study is based on the ensemble-averaged conservation equations of mass, momentum (compressible Navier-Stokes), and energy. Effects of turbulence were modeled by the low Reynolds number shear-stress transport k-ω model. Solutions were generated by a cell-centered, finite-volume method that uses third-order accurate flux-difference splitting of Roe with limiters and multigrid acceleration of a diagonalized ADI scheme with local time stepping on patched/embedded structured grids.

The Effect of a Meter-Diffuser Offset on Shaped Film Cooling Hole Adiabatic Effectiveness

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Shane Haydt ◽  
Stephen Lynch ◽  
Scott Lewis
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Electrical Discharge Machining ◽  
Density Ratio ◽  
Navier Stokes ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Film Cooling Holes

Shaped film cooling holes are used extensively in gas turbines to reduce component temperatures. These holes generally consist of a metering section through the material and a diffuser to spread coolant over the surface. These two hole features are created separately using electrical discharge machining (EDM), and occasionally, an offset can occur between the meter and diffuser due to misalignment. The current study examines the potential impact of this manufacturing defect to the film cooling effectiveness for a well-characterized shaped hole known as the 7-7-7 hole. Five meter-diffuser offset directions and two offset sizes were examined, both computationally and experimentally. Adiabatic effectiveness measurements were obtained at a density ratio of 1.2 and blowing ratios ranging from 0.5 to 3. The detriment in cooling relative to the baseline 7-7-7 hole was worst when the diffuser was shifted upstream (aft meter-diffuser offset), and least when the diffuser was shifted downstream (fore meter-diffuser offset). At some blowing ratios and offset sizes, the fore meter-diffuser offset resulted in slightly higher adiabatic effectiveness than the baseline hole, due to a reduction in the high-momentum region of the coolant jet caused by a separation region created inside the hole by the fore meter-diffuser offset. Steady Reynolds-averaging Navier–Stokes (RANS) predictions did not accurately capture the levels of adiabatic effectiveness or the trend in the offsets, but it did predict the fore offset's improved performance.

scholarly journals Film-Cooling From Holes With Expanded Exits: A Comparison of Computational Results With Experiments

1997 ◽  
Author(s):  
D. Giebert ◽  
M. Gritsch ◽  
A. Schulz ◽  
S. Wittig
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Numerical Code ◽  
Navier Stokes ◽  
Mean Velocity ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Jet In Crossflow ◽  
Film Cooling Holes

A 3D Navier-Stokes code, together with the standard k-ϵ model with wall function approach, was used to investigate the flowfield in the vicinity of three different single scaled-up film-cooling holes. The hole geometries include a cylindrical hole, a hole with laterally expanded exit, and a hole with forward-laterally expanded exit. Comparisons of numerical results with detailed flowfield measurements of mean velocity and turbulent quantities are presented for a blowing ratio and density ratio of unity. Additionally, experimental data for different blowing ratios and a density ratio of about two are taken to perform validation of the code for adiabatic film-cooling effectiveness prediction. Results show that for both the round and the expanded hole geometries the code is able to capture all dominating flow structures of this jet in crossflow problem. However, discrepancies are found when comparing the flowfield inside the hole and at the hole exit. In particular, jet location at the hole exit differs significantly from measurement for the expanded hole geometries. For the adiabatic film-cooling effectiveness, it is shown that for round and expanded hole exits the intensity of the shear regions and the source of turbulence, respectively, have a strong influence on the predictive capability of the numerical code.

Assessment of a Double Hole Film Cooling Geometry Using S-PIV and PSP

2013 ◽  
Author(s):  
Lesley M. Wright ◽  
Stephen T. McClain ◽  
Charles P. Brown ◽  
Weston V. Harmon
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Field Measurements ◽  
Secondary Flows ◽  
Cylindrical Hole ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Hole Geometry ◽  
Compound Angle

A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is θ = 35°, and the compound angle of the holes is β = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of θ = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = −4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposed double hole configuration (compared to the traditional hole designs). The fanshaped, laidback geometry effectively reduces the strength of the kidney-shaped vortices within the structure of the jet (over the entire range of blowing ratios considered). The three-dimensional velocity field measurements indicate the secondary flows formed from the double hole geometry strengthen in the plane perpendicular to the mainstream flow. At the exit of the double hole geometry, the streamwise momentum of the jets is reduced (compared to the single, cylindrical hole), and the geometry offers improved film cooling coverage. However, moving downstream in the steamwise direction, the two jets form a single jet, and the counter-rotating vortices are comparable to those formed within the jet from a single, cylindrical hole. These strong secondary flows lift the coolant off the surface, and the film cooling coverage offered by the double hole geometry is reduced.

Sign in / Sign up

Export Citation Format

Share Document