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.

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.

Film Cooling From Novel Sister Shaped Single-Holes

2014 ◽  
Author(s):  
Siavash Khajehhasani ◽  
Bassam Jubran
Keyword(s):  
Film Cooling ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
Navier Stokes ◽  
The Novel ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Shaped Hole ◽  
Lift Off

A numerical investigation of the film cooling performance from novel sister shaped single-holes (SSSH) is presented in this paper and the obtained results are compared with a single cylindrical hole, a forward diffused shaped hole, as well as discrete sister holes. Three types of the novel sister shaped single-hole schemes namely downstream, upstream and up/downstream SSSH, are designed based on merging the discrete sister holes to the primary hole in order to reduce the jet lift-off effect and increase the lateral spreading of the coolant on the blade surface as well as a reduction in the amount of coolant in comparison with discrete sister holes. The simulations are performed using three-dimensional Reynolds-Averaged Navier Stokes analysis with the realizable k–ε model combined with the standard wall function. The upstream SSSH demonstrates similar film cooling performance to that of the forward diffused shaped hole for the low blowing ratio of 0.5. While it performs more efficiently at M = 1, where the centerline and laterally averaged effectiveness results improved by 70% and 17%, respectively. On the other hand, the downstream and up/downstream SSSH schemes show a considerable improvement in film cooling performance in terms of obtaining higher film cooling effectiveness and less jet lift-off effect as compared with the single cylindrical and forward diffused shaped holes for both blowing ratios of M = 0.5 and 1. For example, the laterally averaged effectiveness for the downstream SSSH configuration shows an improvement of approximately 57% and 110% on average as compared to the forward diffused shaped hole for blowing ratios of 0.5 and 1, respectively.

Leading Edge Film Cooling: Computations and Experiments Including Density Effects

1996 ◽  
Author(s):  
Pingfan He ◽  
Dragos Licu ◽  
Martha Salcudean ◽  
Ian S. Gartshore
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Leading Edge ◽  
Variable Density ◽  
Navier Stokes ◽  
Cooling Effectiveness ◽  
Stagnation Line ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio

The effect of varying coolant density on film cooling effectiveness for a turbine blade-model was numerically investigated and compared with experimental data. This model had a semi-circular leading edge with four rows of laterally-inclined film cooling orifices positioned symmetrically about the stagnation line. A curvilinear coordinate-based CFD code was developed and used for the numerical investigation. The code used a domain segmentation strategy in conjunction with general curvilinear grids to model the complex blade configuration. A multigrid method was used to accelerate the convergence rate. The time-averaged, variable-density, Navier-Stokes equations together with the energy or scalar equation were solved. Turbulence closure was attained by the standard k–ε model with a near-wall k model. Either air or CO2 was used as coolant in three cases of injection through single rows and alternatively staggered double raws of holes. Two different blowing rates were investigated in each case and compared with experimental data. The experimental results were obtained using a wind tunnel model, and the mass/heat analogy was used to determine the film cooling effectiveness. The higher density of the carbon dioxide coolant (approximately 1.5 times the density of air) in the isothermal mass injection experiments, was used to simulate the effects of injection of a colder air in the corresponding adiabatic heat transfer situation. Good agreement between calculated and measured film cooling effectiveness was found for low blowing ratio M ≤ 0.5 and the effect of density was not significant. At higher blowing ratio M > 1 the calculations consistently overpredict the measured values of film cooling effectiveness.

Computational Investigation of Film Cooling from Cylindrical and Row Trenched Cooling Holes near the Combustor End Wall

2014 ◽  
Vol 554 ◽  
pp. 225-229 ◽  
Author(s):  
Nor Azwadi Che Sidik ◽  
Kianpour Ehsan
Keyword(s):  
Film Cooling ◽  
Surface Film ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Internal Cooling ◽  
Cooling Performance ◽  
Turbine Engine ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Three Dimensional Representation

This study was accomplished in order to investigate the effects of cylindrical and row trenched cooling holes with alignment angle of 0 degree and 90 degree at blowing ratio, BR = 3.18 on the film cooling performance adjacent to the endwall surface of a combustor simulator. In this research a three dimensional representation of Pratt and Whitney gas turbine engine was simulated and analyzed with a commercial finite volume package FLUENT 6.2. The current study has been performed with Reynolds-averaged Navier-Stokes turbulence model (RANS) on internal cooling passages. This combustor simulator combined the interaction of two rows of dilution jets, which were staggered in the stream wise direction and aligned in the span wise direction, with that of film cooling along the combustor liner walls. The findings of the study declared that with using the row trenched holes near the endwall surface, film cooling effectiveness is doubled compared to the cooling performance of baseline case.

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.

Heat Transfer in Film-Cooled Turbine Blades

1993 ◽  
Author(s):  
Vijay K. Garg ◽  
Raymond E. Gaugler
Keyword(s):  
Heat Transfer ◽  
Experimental Data ◽  
Film Cooling ◽  
Stokes Equations ◽  
Turbine Blades ◽  
Three Dimensional ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Explicit Finite Difference ◽  
Control Volumes

In order to study the effect of film cooling on the flow and heat transfer characteristics of actual turbine blades, a three-dimensional Navier-Stokes code has been developed. An existing code (Chima and Yokota, 1990) has been modified for the purpose. The code is an explicit finite difference code with an algebraic turbulence model. The thin-layer Navier-Stokes equations are solved using a general body-fitted coordinate system. The effects of film cooling have been incorporated into the code in the form of appropriate boundary conditions at the hole locations on the blade surface. Each hole exit is represented by several control volumes, thus providing an ability to study the effect of hole shape on the film-cooling characteristics. Comparison with experimental data is fair. Further validation of the code is required, however, and in this respect, there is an urgent need for detailed experimental data on actual turbine blades.

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.

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.

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.

Curvature Effects on Discrete-Hole Film Cooling

1999 ◽  
Vol 121 (4) ◽  
pp. 781-791 ◽  
Author(s):  
M. K. Berhe ◽  
S. V. Patankar
Keyword(s):  
Film Cooling ◽  
Stokes Equations ◽  
Convex Surface ◽  
Numerical Study ◽  
Turbulent Viscosity ◽  
Density Ratio ◽  
Three Dimensional ◽  
Cooling Effectiveness ◽  
Streamline Curvature ◽  
Curvature Effects

A numerical study has been conducted to investigate the effects of surface curvature on cooling effectiveness using three-dimensional film cooling geometries that included the mainflow, injection hole, and supply plenum regions. Three surfaces were considered in this study, namely, convex, concave, and flat surfaces. The fully elliptic, three-dimensional Navier–Stokes equations were solved over a body-fitted grid. The effects of streamline curvature were taken into account by using algebraic relations for the turbulent viscosity and the turbulent Prandtl number in a modified k–ε turbulence model. Computations were performed for blowing ratios of 0.5, 1.0, and 1.5 at a density ratio of 2.0. The computed and experimental cooling effectiveness results were compared. For the most part, the cooling effectiveness was predicted quite well. A comparison of the cooling performances over the three surfaces reveals that the effect of streamline curvature on cooling effectiveness is very significant. For the low blowing ratios considered, the convex surface resulted in a higher cooling effectiveness than both the flat and concave surfaces. The flow structures over the three surfaces also exhibited important differences. On the concave surface, the flow involved a stronger vorticity and greater mixing of the coolant jet with the mainstream gases. On the convex surface, the counterrotating vortices were suppressed and the coolant jet pressed to the surface by a strong cross-stream pressure gradient.

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