Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements: Part II — Turbulence Effects

2002 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Side ◽  
Thermal Fields ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
Average Distribution ◽  
Adiabatic Effectiveness

This study focused on the film cooling performance on the pressure side of a turbine vane subjected to high mainstream turbulence levels, with and without showerhead blowing. Whereas previous studies have measured the adiabatic effectiveness and heat transfer at the surface of the airfoil, the goal of this study was to examine the flow and thermal fields above the surface. These measurements included flow visualization, thermal profiles, and laser Doppler velocimetry. For comparison, adiabatic effectiveness was also measured. A mainstream turbulence level of Tu∞ = 20%, with integral length scale of seven hole diameters, was used. Particularly insightful is the discovery that the large scale high mainstream turbulence causes a lateral oscillation of coolant jet resulting in a much wider time average distribution of coolant. Even with high mainstream turbulence, showerhead blowing was found to still cause a significantly increased dispersion of the pressure side coolant jets.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part II: Turbulence Effects

2002 ◽  
Vol 124 (4) ◽  
pp. 678-685 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Large Scale ◽  
Field Measurements ◽  
Pressure Side ◽  
Thermal Fields ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
Average Distribution ◽  
Adiabatic Effectiveness

This study focused on the film cooling performance on the pressure side of a turbine vane subjected to high mainstream turbulence levels, with and without showerhead blowing. Whereas previous studies have measured the adiabatic effectiveness and heat transfer at the surface of the airfoil, the goal of this study was to examine the flow and thermal fields above the surface. These measurements included flow visualization, thermal profiles, and laser Doppler velocimetry. For comparison, adiabatic effectiveness was also measured. A mainstream turbulence level of Tu∞=20%, with integral length scale of seven hole diameters, was used. Particularly insightful is the discovery that the large-scale high mainstream turbulence causes a lateral oscillation of coolant jet resulting in a much wider time average distribution of coolant. Even with high mainstream turbulence, showerhead blowing was found to still cause a significantly increased dispersion of the pressure side coolant jets.

Effects of Deposits on Film Cooling of a Vane Endwall Along the Pressure Side

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
N. Sundaram ◽  
M. D. Barringer ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Secondary Flows ◽  
Pressure Side ◽  
Surface Deposition ◽  
Hot Gas ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes ◽  
Effect Of Surface

Film cooling is influenced by surface roughness and depositions that occur from contaminants present in the hot gas path, whether that film cooling occurs on the vane itself or on the endwalls associated with the vanes. Secondary flows in the endwall region also affect the film-cooling performance along the endwall. An experimental investigation was conducted to study the effect of surface deposition on film cooling along the pressure side of a first-stage turbine vane endwall. A large-scale wind tunnel with a turbine vane cascade was used to perform the experiments. The vane endwall was cooled by an array of film-cooling holes along the pressure side of the airfoil. Deposits having a semielliptical shape were placed along the pressure side to simulate individual row and multiple row depositions. Results indicated that the deposits lowered the average adiabatic effectiveness levels downstream of the film-cooling rows by deflecting the coolant jets toward the vane endwall junction on the pressure side. Results also indicated that there was a steady decrease in adiabatic effectiveness levels with a sequential increase in the number of rows with the deposits.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements—Part I: Showerhead Effects

2002 ◽  
Vol 124 (4) ◽  
pp. 670-677 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Leading Edge ◽  
Field Measurements ◽  
Companion Paper ◽  
Hole Diameter ◽  
Pressure Side ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
High Turbulence

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e., flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

Evaluation of Pressure Side Film Cooling With Flow and Thermal Field Measurements: Part I — Showerhead Effects

2002 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Leading Edge ◽  
Field Measurements ◽  
Companion Paper ◽  
Hole Diameter ◽  
Pressure Side ◽  
Turbine Vane ◽  
Turbulence Effects ◽  
High Turbulence

The goal of this study was to determine how showerhead blowing on a turbine vane leading edge affects of the performance of film cooling jets farther downstream. An emphasis was placed on measurements above the surface, i.e. flow visualization, thermal field, and velocity field measurements. The film cooling performance on the pressure side of a simulated turbine vane, with and without showerhead blowing, was examined. Results presented in this paper are for low mainstream turbulence; high mainstream turbulence effects are presented in the companion paper. At the location of the pressure side row of holes, the showerhead coolant extended a distance of about 3d from the surface (d is the coolant hole diameter). The pressure side was found to be subjected to high turbulence levels caused by the showerhead injection. Results indicate a greater dispersion of the pressure side coolant jets with showerhead flow due to the elevated turbulence levels.

Effects of Deposits on Film Cooling of a Vane Endwall Along the Pressure Side

2007 ◽  
Author(s):  
N. Sundaram ◽  
M. D. Barringer ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Secondary Flows ◽  
Pressure Side ◽  
Surface Deposition ◽  
Hot Gas ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes ◽  
Effect Of Surface

Film-cooling is influenced by surface roughness and depositions that occur from contaminants present in the hot gas path, whether that film-cooling occurs on the vane itself or on the endwalls associated with the vanes. Secondary flows in the endwall region also affect the film-cooling performance along the endwall. An experimental investigation was conducted to study the effect of surface deposition on film-cooling along the pressure side of a first-stage turbine vane endwall. A large-scale wind tunnel with a turbine vane cascade was used to perform the experiments. The vane endwall was cooled by an array of film-cooling holes along the pressure side of the airfoil. Deposits having a semi-elliptical shape were placed along the pressure side to simulate individual row and multiple row depositions. Results indicated that the deposits lowered the average adiabatic effectiveness levels downstream of the film-cooling rows by deflecting the coolant jets towards the vane endwall junction on the pressure side. Results also indicated that there was a steady decrease in adiabatic effectiveness with a sequential increase in the number of rows with the deposits.

Evaluation of Superposition Predictions for Showerhead Film Cooling on a Vane

2014 ◽  
Author(s):  
Joshua B. Anderson ◽  
James R. Winka ◽  
David G. Bogard ◽  
Michael E. Crawford
Keyword(s):  
Film Cooling ◽  
Momentum Flux ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Edge Region ◽  
Current Investigation ◽  
Engine Design ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

The leading edge of a turbine vane is subject to some of the highest temperature loading within an engine, and an accurate understanding of leading edge film coolant behavior is essential for modern engine design. Although there have been many investigations of the adiabatic effectiveness for showerhead film cooling of a vane leading edge region, there have been no previous studies in which individual rows of the showerhead were tested with the explicit intent of validating superposition models. For the current investigation, a series of adiabatic effectiveness experiments were performed with a five-row and three-row showerhead. The experiments were repeated separately with each individual row of holes active. This allowed evaluation of superposition methods on both the suction side of the vane, which was moderately convex, and the pressure side of the vane, which was mildly concave. Superposition was found to accurately predict performance on the suction side of the vane at lower momentum flux ratios, but not at higher momentum flux ratios. On the pressure side of the vane the superposition predictions were consistently lower than measured values, with significant errors occurring at the higher momentum flux ratios. Reasons for the under-prediction by superposition analysis are presented.

Bump and Trench Modifications to Film-Cooling Holes at the Vane-Endwall Junction

2008 ◽  
Vol 130 (4) ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
High Heat ◽  
Junction Region ◽  
High Heat Transfer ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes

The endwall of a first-stage vane experiences high heat transfer and low adiabatic effectiveness levels because of high turbine operating temperatures and formation of leading edge vortices. These vortices lift the coolant off the endwall and pull the hot mainstream gases toward it. The region of focus for this study is the vane-endwall junction region near the stagnation location where cooling is very difficult. Two different film-cooling hole modifications, namely, trenches and bumps, were evaluated to improve the cooling in the leading edge region. This study uses a large-scale turbine vane cascade with a single row of axial film-cooling holes at the leading edge of the vane endwall. Individual hole trenches and row trenches were placed along the complete row of film-cooling holes. Two-dimensional semi-elliptically shaped bumps were also evaluated by placing the bumps upstream and downstream of the film-cooling row. Tests were carried out for different trench depths and bump heights under varying blowing ratios. The results indicated that a row trench placed along the row of film-cooling holes showed a greater enhancement in adiabatic effectiveness levels when compared to individual hole trenches and bumps. All geometries considered produced an overall improvement to adiabatic effectiveness levels.

Thermal Field and Flow Visualization Within the Stagnation Region of a Film Cooled Turbine Vane

2001 ◽  
Author(s):  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Flow Visualization ◽  
Film Cooling ◽  
Laser Doppler Velocimetry ◽  
Thermal Field ◽  
Velocity Fields ◽  
Stagnation Region ◽  
Physical Mechanisms ◽  
Mainstream Flow ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

To develop quality computational codes for the film cooling of a turbine vane, a detailed understanding is needed of the physical mechanisms of the mainstream-coolant interactions. In this study flow visualization, thermal profiles, and laser Doppler velocimetry measurements were used to define the thermal and velocity fields of the film cooled showerhead region of a turbine vane. The showerhead consisted of six rows of spanwise oriented coolant holes, and blowing ratios ranged from 0.8 to 2.5. Performances with low and high mainstream turbulence levels were tested. Coolant jets from the showerhead were completely separated from the surface even at relatively low blowing ratios. However, the interaction of the coolant jets from laterally adjacent holes created a barrier to the mainstream flow, resulting in relatively high adiabatic effectiveness.

Bump and Trench Modifications to Film-Cooling Holes at the Vane Endwall Junction

2007 ◽  
Author(s):  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Leading Edge ◽  
High Heat ◽  
Junction Region ◽  
High Heat Transfer ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness ◽  
Film Cooling Holes

The endwall of a first stage vane experiences high heat transfer and low adiabatic effectiveness levels because of high turbine operating temperatures and formation of leading edge vortices. These vortices lift the coolant off the endwall and pull the hot mainstream gases towards it. The region of focus for this study is the vane-endwall junction region near the stagnation location where cooling is very difficult. Two different film-cooling hole modifications, namely trenches and bumps, were evaluated to improve the cooling in the leading edge region. This study uses a large-scale turbine vane cascade with a single row of axial film-cooling holes at the leading edge of the vane endwall. Individual hole trenches and row trenches were placed along the complete row of film-cooling holes. Two-dimensional semi-elliptically shaped bumps were also evaluated by placing the bumps upstream and downstream of the film-cooling row. Tests were carried out for different trench depths and bump heights under varying blowing ratios. The results indicated that a row trench placed along the row of film-cooling holes showed a greater enhancement in adiabatic effectiveness levels when compared to individual hole trenches and bumps. All geometries considered produced an overall improvement to adiabatic effectiveness levels.

Effects of Hot Streaks on Adiabatic Effectiveness for a Film Cooled Turbine Vane

2004 ◽  
Author(s):  
Krishnakumar Varadarajan ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Field Measurements ◽  
Suction Side ◽  
Experimental Program ◽  
Turbine Engines ◽  
Gas Turbine Engines ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Hot Streak ◽  
Effectiveness Data

Turbine guide vanes in gas turbine engines are typically subjected to localized “hot streaks” emanating from the combustor. This experimental program examined how these hot streaks affect the film cooling performance for these vanes. Adiabatic effectiveness tests were conducted on the showerhead and suction side regions of the vane. Particular attention was placed on how to scale that adiabatic effectiveness data obtained with a hot streak to correctly predict the adiabatic effectiveness. Thermal field measurements were made to determine the temperature gradients for the hot streak near the wall. These experiments showed that the effect of the hot streak on the adiabatic effectiveness could be accounted for by using an “adjusted” mainstream temperature equal to the hot streak temperature at the wall of the vane.

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