Discrete-Jet Film Cooling: A Comparison of Computational Results With Experiments

1993 ◽  
Author(s):  
J. H. Leylek ◽  
R. D. Zerkle
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Turbulence Modeling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Navier Stokes ◽  
Complex Flow ◽  
Coupled Flow ◽  
Injection Angle

Large scale computational analyses have been conducted and results compared with experiments to understand coolant jet and crossflow interaction in discrete–jet film cooling. Detailed three–dimensional elliptic Navier–Stokes solutions, with high order turbulence modeling, are presented for film cooling using a new model enabling simultaneous solution of fully coupled flow in plenum, film–hole, and cross–stream regions. Computations are carried out for the following range of film cooling parameters typically found in gas turbine airfoil applications: single row of jets with a film–hole length–to–diameter ratio of 1.75 and 3.5; blowing ratio from 0.5 up to 2; coolant–to–crossflow density ratio of 2; streamwise injection angle of 35 degrees; and pitch–to–diameter ratio of 3. Comparison of computational solutions with experimental data are in good agreement Moreover, the current results complement experiments and support previous interpretations of measured data and flow visualization. The results also explain important aspects of film cooling, such as the development of complex flow within the film–hole in addition to the well known counterrotating vortex structure in the cross–stream.

Discrete-Jet Film Cooling: A Comparison of Computational Results With Experiments

1994 ◽  
Vol 116 (3) ◽  
pp. 358-368 ◽  
Author(s):  
J. H. Leylek ◽  
R. D. Zerkle
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Three Dimensional ◽  
Diameter Ratio ◽  
Navier Stokes ◽  
Complex Flow ◽  
Coupled Flow ◽  
Injection Angle ◽  
Computational Analyses

Large-scale computational analyses have been conducted and results compared with experiments to understand coolant jet and crossflow interaction in discrete-jet film cooling. Detailed three-dimensional elliptic Navier–Stokes solutions, with high-order turbuence modeling, are presented for film cooling using a new model enabling simultaneous solution of fully coupled flow in plenum, film-hole, and cross-stream regions. Computations are carried out for the following range of film cooling parameters typically found in gas turbine airfoil applications: single row of jets with a film-hole length-to-diameter ratio of 1.75 and 3.5; blowing ratio from 0.5 up to 2; coolant-to-crossflow density ratio of 2; streamwise injection angle of 35 deg; and pitch-to-diameter ratio of 3. Comparison of computational solutions with experimental data give good agreement. Moreover, the current results complement experiments and support previous interpretations of measured data and flow visualization. The results also explain important aspects of film cooling, such as the development of complex flow within the film-hole in addition to the well-known counterrotating vortex structure in the cross-stream.

A Systematic Computational Methodology Applied to a Three-Dimensional Film-Cooling Flowfield

1997 ◽  
Vol 119 (4) ◽  
pp. 777-785 ◽  
Author(s):  
D. K. Walters ◽  
J. H. Leylek
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Turbulence Modeling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Elliptic Solution ◽  
Injection Angle ◽  
Free Stream Turbulence ◽  
Acceleration Techniques ◽  
Computational Methodology

Numerical results are presented for a three-dimensional discrete-jet in crossflow problem typical of a realistic film-cooling application in gas turbines. Key aspects of the study include: (1) application of a systematic computational methodology that stresses accurate computational model of the physical problem, including simultaneous, fully elliptic solution of the crossflow, film-hole, and plenum regions; high-quality three-dimensional unstructured grid generation techniques, which have yet to be documented for this class of problems; the use of a high-order discretization scheme to reduce numerical errors significantly; and effective turbulence modeling; (2) a three-way comparison of results to both code validation quality experimental data and a previously documented structured grid simulation; and (3) identification of sources of discrepancy between predicted and measured results, as well as recommendations to alleviate these discrepancies. Solutions were obtained with a multiblock, unstructured/adaptive grid, fully explicit, time-marching, Reynolds-averaged Navier–Stokes code with multigrid, local time stepping, and residual smoothing type acceleration techniques. The computational methodology was applied to the validation test case of a row of discrete jets on a flat plate with a streamwise injection angle of 35 deg, and two film-hole length-to-diameter ratios of 3.5 and 1.75. The density ratio for all cases was 2.0, blowing ratio was varied from 0.5 to 2.0, and free-stream turbulence intensity was 2 percent. The results demonstrate that the prescribed computational methodology yields consistently more accurate solutions for this class of problems than previous attempts published in the open literature. Sources of disagreement between measured and computed results have been identified, and recommendations made for future prediction of film-cooling problems.

Flow Characteristics in a Three-Dimensional Rectangular Channel With a Pair of Ribs Placed Symmetrically at the Channel Walls

2000 ◽  
Author(s):  
M. Singh ◽  
P. K. Panigrahi ◽  
G. Biswas
Keyword(s):  
Heat Transfer ◽  
Large Scale ◽  
Numerical Study ◽  
Rectangular Channel ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Flow Characteristics ◽  
Navier Stokes ◽  
Complex Flow ◽  
Energy Equations

Abstract A numerical study of rib augmented cooling of turbine blades is reported in this paper. The time-dependent velocity field around a pair of symmetrically placed ribs on the walls of a three-dimensional rectangular channel was studied by use of a modified version of Marker-And-Cell algorithm to solve the unsteady incompressible Navier-Stokes and energy equations. The flow structures are presented with the help of instantaneous velocity vector and vorticity fields, FFT and time averaged and rms values of components of velocity. The spanwise averaged Nusselt number is found to increase at the locations of reattachment. The numerical results are compared with available numerical and experimental results. The presence of ribs leads to complex flow fields with regions of flow separation before and after the ribs. Each interruption in the flow field due to the surface mounted rib enables the velocity distribution to be more homogeneous and a new boundary layer starts developing downstream of the rib. The heat transfer is primarily enhanced due to the decrease in the thermal resistance owing to the thinner boundary layers on the interrupted surfaces. Another reason for heat transfer enhancement can be attributed to the mixing induced by large-scale structures present downstream of the separation point.

Investigation of Discrete-Hole Film Cooling Parameters Using Curved-Plate Models

1999 ◽  
Vol 121 (4) ◽  
pp. 792-803 ◽  
Author(s):  
M. K. Berthe ◽  
S. V. Patankar
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Grid Turbulence ◽  
Injection Angle ◽  
Flat Surfaces ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Computations have been conducted on curved, three-dimensional discrete-hole film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Both convex and concave film cooling geometries were studied. The effects of several film cooling parameters have been investigated, including the effects of blowing ratio, injection angle, hole length, hole spacing, and hole staggering. The blowing ratio was varied from 0.5 to 1.5, the injection angle from 35 to 65 deg, the hole length from 1.75D to 6.0D, and the hole spacing from 2D to 3D. The staggered-hole arrangement considered included two rows. The computations were performed by solving the fully elliptic, three-dimensional Navier–Stokes equations over a body-fitted grid. Turbulence closure was achieved using a modified k–ε model in which algebraic relations were used for the turbulent viscosity and the turbulent Prandtl number. The results presented and discussed include plots of adiabatic effectiveness as well as plots of velocity contours and velocity vectors in cross-stream planes. The present study reveals that the blowing ratio, hole spacing, and hole staggering are among the most significant film cooling parameters. Furthermore: (1) The optimum blowing ratios for curved surfaces are higher than those for flat surfaces, (2) a reduction of hole spacing from 3D to 2D resulted in a very significant increase in adiabatic effectiveness, especially on the concave surface, (3) the increase in cooling effectiveness with decreasing hole spacing was found to be due to not only the increased coolant mass per unit area, but also the smaller jet penetration and the weaker counterrotating vortices, (4) for all practical purposes, the hole length was found to be a much less significant film cooling parameter.

Effect of Various Injection Hole Shapes on Film Cooling of Turbine Blade

2003 ◽  
Author(s):  
S.-M. Kim ◽  
Youn J. Kim
Keyword(s):  
Turbine Blade ◽  
Film Cooling ◽  
Three Dimensional ◽  
Cylindrical Body ◽  
Navier Stokes ◽  
Cylinder Surface ◽  
Injection Hole ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Cooling Flow

Dispersion of coolant jets in a film cooling flow field is the result of a highly complex interaction between the film cooling jets and the mainstream. In order to investigate the effects of injection hole shapes and injection angle on the film cooling of turbine blade, four models having cylindrical and laterally-diffused holes were used. Three-dimensional Navier-Stokes code with k – ε model was used to compute the film cooling coefficient on the turbine blade. A multi-block grid system was generated that was nearly orthogonal to the various surfaces. Mainstream Reynolds number based on the cylinder diameter was 7.1 × 104. The turbulence intensity kept at 5.0% for all inlets. The effect of coolant flow rates was studied for blowing ratios of 0.9, 1.3 and 1.6, respectively. The temperature distribution of the cylindrical body surface is visualized by infrared thermography (IRT) and compared with computational results. Results show that the effects of injection hole shape and injection angle increase as the blowing ratio increases. As lateral injection angle increases, the adiabatic film cooling effectiveness is more broadly distributed and the area protected by coolant increases. The mass flow rate of the coolant through the first-row holes is less than that through the second-row holes due to the pressure distribution around the cylinder surface.

Film Cooling of Compound Angle Upstream Sister Holes

2019 ◽  
Author(s):  
Sana Abd Alsalam ◽  
Bassam Jubran
Keyword(s):  
Film Cooling ◽  
Turbulence Modeling ◽  
Stokes Equations ◽  
Density Ratio ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Simple Strategy ◽  
Compound Angle

Abstract This study introduces a novel and simple strategy; compound angle upstream sister holes (CAUSH) to increase film cooling performance of the cylindrical hole by combining two techniques: Sister holes; (two small round holes placed upstream the primary hole) and compound angle hole. Whereas the upstream sister holes were injected at several compound angles β = 0°, 45°, 75°, and 90°, while the main hole was injected to the streamwise direction at 35° on a flat plate. FLUENT-ANSYS code was used to perform the simulation by solving the 3D Reynolds Averaged Navier-Stokes Equations. The capability of three types of k-ε turbulence modeling combined with the enhanced wall treatment is investigated to predict the film cooling performance of sister holes. A detailed computational analysis of the cooling performance of the (CAUSH) and the flow field was done at a density ratio equal to two (D.R = 2) and four blowing ratios M = 0.25, 0.5, 1.0 and 1.5 to predict the centerline and laterally averaged film cooling performance. The centerline effectiveness results showed that the highest cooling performance from the examined (CAUSH) was obtained at β = 0°, 45°, and 90° for low and high blowing ratio, the highest laterally averaged film cooling performance was captured at β = 0° and 90° for all tested blowing ratios. Also, the results indicated that the upstream sister hole with 90° compound angle holes has the best overall film cooling effectiveness while the worst performance is attained at β = 75°.

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.

scholarly journals Investigation of Discrete-Hole Film Cooling Parameters Using Curved-Plate Models

1998 ◽  
Author(s):  
Mulugeta K. Berhe ◽  
Suhas V. Patankar
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Turbulent Viscosity ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Grid Turbulence ◽  
Injection Angle ◽  
Flat Surfaces ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Computations have been conducted on curved, three-dimensional discrete-hole film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Both convex and concave film cooling geometries were studied. The effects of several film cooling parameters have been investigated, including the effects of blowing ratio, injection angle, hole length, hole spacing, and hole staggering. The blowing ratio was varied from 0.5 to 1.5, the injection angle from 35° to 65°, the hole length from 1.75D to 6.0D, and the hole spacing from 2D to 3D. The staggered-hole arrangement considered included two rows. The computations were performed by solving the fully elliptic, three dimensional Navier-Stokes equations over a body fitted grid. Turbulence closure was achieved using a modified k-ε model in which algebraic relations were used for the turbulent viscosity and the turbulent Prandtl number. The results presented and discussed include plots of adiabatic effectiveness as well as plots of velocity contours and velocity vectors in cross-stream planes. The present study reveals that the blowing ratio, hole spacing, and hole staggering are among the most significant film cooling parameters. Furthermore: (1) the optimum blowing ratios for curved surfaces are higher than those for flat surfaces, (2) a reduction of hole spacing from 3D to 2D resulted in a very significant increase in adiabatic effectiveness, especially on the concave surface, (3) the increase in cooling effectiveness with decreasing hole spacing was found due to not only the increased coolant mass per unit area, but also the smaller jet penetration and the weaker counter-rotating vortices, (4) for all practical purposes, the hole length was found to be a much less significant film cooling parameter.

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.

Effects of Curvature on the Film Cooling Effectiveness of Double-Jet Film Cooling

2014 ◽  
Author(s):  
Gaoliang Liao ◽  
Xinjun Wang ◽  
Jun Li ◽  
Feng Zhang
Keyword(s):  
Film Cooling ◽  
Flat Surface ◽  
Three Dimensional ◽  
Curved Surface ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Sst Model ◽  
Selection Of

The effect of curvature on the film cooling characteristics of Double-Jet Film Cooling (DJFC) was numerically investigated using three-dimensional Reynolds-Averaged Navier-Stokes (RANS). The low-Reynolds number shear stress transport (SST) model was employed as the turbulence closure model. Six different curved surfaces and a flat surface were tested numerically. The blowing ratios were from 0.66 to 1.99, and the compound injection angle with respect to the cooled surface was 30 degree. The blowing ratios and the curvature of cooled surface have crucial effects on the film cooling effectiveness. The numerical results show that there are two peek value of the averaged film cooling effectiveness along the mainstream direction. The results also indicate that the film cooling effectiveness of a specified curved surface depends on the reasonable selection of the slope of curved surface and blowing ratios.

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