scholarly journals Investigation of Spiral and Sweeping Holes

2016 ◽  
Vol 138 (9) ◽  
Author(s):  
Douglas Thurman ◽  
Philip Poinsatte ◽  
Ali Ameri ◽  
Dennis Culley ◽  
Surya Raghu ◽  
...  
Keyword(s):  
Infrared Thermography ◽  
Cross Sections ◽  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Navier Stokes ◽  
Freestream Velocity ◽  
Cooling Hole ◽  
Downstream Flow ◽  
Hotwire Anemometry

Surface infrared thermography, hotwire anemometry, and thermocouple surveys were performed on two new film cooling hole geometries: spiral/rifled holes and fluidic sweeping holes. The spiral holes attempt to induce large-scale vorticity to the film cooling jet as it exits the hole to prevent the formation of the kidney-shaped vortices commonly associated with film cooling jets. The fluidic sweeping hole uses a passive in-hole geometry to induce jet sweeping at frequencies that scale with blowing ratios. The spiral hole performance is compared to that of round holes with and without compound angles. The fluidic hole is of the diffusion class of holes and is therefore compared to a 777 hole and square holes. A patent-pending spiral hole design showed the highest potential of the nondiffusion-type hole configurations. Velocity contours and flow temperature were acquired at discreet cross sections of the downstream flow field. The passive fluidic sweeping hole shows the most uniform cooling distribution but suffers from low span-averaged effectiveness levels due to enhanced mixing. The data were taken at a Reynolds number of 11,000 based on hole diameter and freestream velocity. Infrared thermography was taken for blowing ratios of 1.0, 1.5, 2.0, and 2.5 at a density ratio of 1.05. The flow inside the fluidic sweeping hole was studied using 3D unsteady Reynolds-average Navier–Stokes (RANS).

scholarly journals Investigation of Spiral and Sweeping Holes

2015 ◽  
Author(s):  
Douglas Thurman ◽  
Philip Poinsatte ◽  
Ali Ameri ◽  
Dennis Culley ◽  
Surya Raghu ◽  
...  
Keyword(s):  
Infrared Thermography ◽  
Cross Sections ◽  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Diffusion Type ◽  
Freestream Velocity ◽  
Cooling Hole ◽  
Downstream Flow ◽  
Hotwire Anemometry

Surface infrared thermography, hotwire anemometry, and thermocouple surveys were performed on two new film cooling hole geometries: spiral/rifled holes and fluidic sweeping holes. The spiral holes attempt to induce large-scale vorticity to the film cooling jet as it exits the hole to prevent the formation of the kidney shaped vortices commonly associated with film cooling jets. The fluidic sweeping hole uses a passive in-hole geometry to induce jet sweeping at frequencies that scale with blowing ratios. The spiral hole performance is compared to that of round holes with and without compound angles. The fluidic hole is of the diffusion class of holes and is therefore compared to a 777 hole and Square holes. A patent-pending spiral hole design showed the highest potential of the non-diffusion type hole configurations. Velocity contours and flow temperature were acquired at discreet cross-sections of the downstream flow field. The passive fluidic sweeping hole shows the most uniform cooling distribution but suffers from low span-averaged effectiveness levels due to enhanced mixing. The data was taken at a Reynolds number of 11,000 based on hole diameter and freestream velocity. Infrared thermography was taken for blowing ratios of 1.0, 1.5, 2.0, and 2.5 at a density ratio of 1.05. The flow inside the fluidic sweeping hole was studied using 3D unsteady RANS.

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.

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.

Turbulence and Heat Transfer Measurements in an Inclined Large Scale Film Cooling Array: Part I—Velocity and Turbulence Measurements

2011 ◽  
Author(s):  
Lamyaa A. El-Gabry ◽  
Douglas R. Thurman ◽  
Philip E. Poinsatte ◽  
James D. Heidmann
Keyword(s):  
Heat Transfer ◽  
Flow Field ◽  
Film Cooling ◽  
Large Scale ◽  
Field Measurements ◽  
Scale Model ◽  
Liquid Crystal Thermography ◽  
Detailed Surface ◽  
Cooling Hole ◽  
Hotwire Anemometry

A large-scale model of an inclined row of film cooling holes is used to obtain detailed surface and flow field measurements that will enable future computational fluid dynamics code development and validation. The model consists of three holes of 1.9-cm diameter that are spaced 3 hole diameters apart and inclined 30° from the surface. The length to diameter ratio of the coolant holes is about 18. Measurements include film effectiveness using IR thermography and near wall thermocouples, heat transfer using liquid crystal thermography, flow field temperatures using a thermocouple, and velocity and turbulence quantities using hotwire anemometry. Results are obtained for blowing ratios of up to 2 in order to capture severe conditions in which the jet is lifted. This first part of the two-part paper presents the detailed velocity component and turbulence stresses along the centerline of the film-cooling hole and at various streamwise locations.

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.

Massively-Parallel Compressible Discontinuous Galerkin Spectral Element LES of Film Cooling

2015 ◽  
Author(s):  
Joshua L. Camp ◽  
Andrew Duggleby
Keyword(s):  
Discontinuous Galerkin ◽  
Film Cooling ◽  
Stokes Equations ◽  
Density Ratio ◽  
Spectral Element ◽  
Navier Stokes ◽  
Navier Stokes Equations ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Lift Off

There are many gas turbine flows that are subsonic but still at speeds where gas compresses and the assumptions made in a low-Mach formulation are inadequate. In particular, a low-Mach spectral element solver, NEK5000, was used to perform a LES study of a film cooling hole at a blowing ratio and density ratio of 1.0 and 1.5, respectively. Due to a lack of real compressibility effects in the formulation, the simulation over-predicted the velocity in the hole, leading to large coolant lift-off and poorer film cooling performance than expected. Recently, the capabilities of NEK5000 have been extended to solve the compressible Navier-Stokes equations using the discontinuous Galerkin spectral element method (DGSEM). In this paper, details of the new algorithm are given, and results of the new simulation show vast improvements over the low-Mach code and compare well to previous experimental results.

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.

scholarly journals Scaling of Film Cooling Discharge Coefficient Measurements to Engine Conditions

1998 ◽  
Author(s):  
D. A. Rowbury ◽  
M. L. G. Oldfield ◽  
G. D. Lock ◽  
S. N. Dancer
Keyword(s):  
Reynolds Number ◽  
Film Cooling ◽  
Large Scale ◽  
Discharge Coefficient ◽  
Density Ratio ◽  
Elevated Pressure ◽  
Ambient Temperatures ◽  
Discharge Coefficients ◽  
Cooling Hole ◽  
Nozzle Guide

This paper discusses the need and the procedure for scaling discharge coefficient measurements made in an ambient temperature experiment to render them applicable to the engine situation. Among the dimensionless parameters affecting the discharge coefficients of film cooling holes are the Reynolds number and the coolant Mach number. Experiments have been conducted in a large scale annular blowdown cascade of film cooled nozzle guide vanes. The coolant system design, using a heavy ‘foreign gas’ (an SF6/Ar mixture) at ambient temperatures, allows the coolant-to-mainstream density ratio and blowing parameters to be matched to engine values. By using elevated pressure tests, the effect of varying the coolant Reynolds number without external flow is observed experimentally and these results are then used to correct the discharge coefficients measured on the vane with external crossflow. Data is presented and discussed for two cooling hole geometries, namely cylindrical and fanshaped holes.

Implicit LES for Shaped-Hole Film Cooling Flow

2017 ◽  
Author(s):  
Todd A. Oliver ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Robert D. Moser ◽  
Gregory Laskowski
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Vortex Pair ◽  
Cooling Flow ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Mean Temperature ◽  
Cooling Hole ◽  
The Mean ◽  
Adiabatic Effectiveness

Results of a recent joint experimental and computational investigation of the flow through a plenum-fed 7-7-7 shaped film cooling hole are presented. In particular, we compare the measured adiabatic effectiveness and mean temperature against implicit large eddy simulation (iLES) for blowing ratio approximately 2, density ratio 1.6, and Reynolds number 6000. The results overall show reasonable agreement between the iLES and the experimental results for the adiabatic effectiveness and gross features of the mean temperature field. Notable discrepancies include the centerline adiabatic effectiveness near the hole, where the iLES under-predicts the measurements by Δη ≈ 0.05, and the near-wall temperature, where the simulation results show features not present in the measurements. After showing this comparison, the iLES results are used to examine features that were not measured in the experiments, including the in-hole flow and the dominant fluxes in the mean internal energy equation downstream of the hole. Key findings include that the flow near the entrance to the hole is highly turbulent and that there is a large region of backflow near the exit of the hole. Further, the well-known counter-rotating vortex pair downstream of the hole is observed. Finally, the typical gradient diffusion hypothesis for the Reynolds heat flux is evaluated and found to be incorrect.

Interactions of Film Cooling Rows: Effects of Hole Geometry and Row Spacing on the Cooling Performance Downstream of the Second Row of Holes

2003 ◽  
Author(s):  
Christian Saumweber ◽  
Achmed Schulz
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Operating Conditions ◽  
Transfer Coefficients ◽  
Film Cooling Effectiveness ◽  
Heat Transfer Coefficients ◽  
Staggered Arrangement ◽  
Film Cooling Holes

A comprehensive set of generic experiments is conducted to investigate the interaction of film cooling rows. Five different film cooling configurations are considered on a large scale basis each consisting of two rows of film cooling holes in staggered arrangement. The hole pitch to diameter ratio within each row is kept constant at P/D = 4. The spacing between the rows is either x/D = 10, 20, or 30. Fanshaped holes or simple cylindrical holes with an inclination angle of 30 deg. and a hole length of 6 hole diameters are used. With a hot gas Mach number of Mam = 0.3, an engine like density ratio of ρc/ρm = 1.75, and a freestream turbulence intensity of Tu = 5.1% are established. Operating conditions are varied in terms of blowing ratio for the upstream and, independently, the downstream row in the range 0.5<M<2.0. The results illustrate the importance of considering ejection into an already film cooled boundary layer. Adiabatic film cooling effectiveness and heat transfer coefficients are significantly increased. The decay of effectiveness with streamwise distance is much less pronounced downstream of the second row primarily due to pre-cooling of the boundary layer by the first row of holes. Additionally, a comparison of measured effectiveness data with predictions according to the widely used superposition model of Sellers [11] is given for two rows of fanshaped holes.

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