Effects of Showerhead Cooling on Turbine Vane Suction Side Film Cooling Effectiveness

2000 ◽  
Author(s):  
Marcia I. Ethridge ◽  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Density Ratio ◽  
Infrared Camera ◽  
Suction Side ◽  
Strong Impact ◽  
Film Cooling Effectiveness ◽  
Spatially Resolved ◽  
Turbine Vane ◽  
Adiabatic Effectiveness

Abstract The process of film cooling is known to severely disturb the boundary layer around a turbine airfoil. Since most film-cooled airfoils have more than one injection station, the flow field approaching a row of film cooling holes could be altered by the presence of an upstream cooling station. To investigate this possibility, an experimental investigation was conducted on the suction side of a scaled-up turbine vane. Adiabatic effectiveness measurements were made downstream of a single row of cooling holes both with and without the upstream showerhead holes operating. A range of suction side blowing ratios, 0.3 ≤ M ≤ 1.3, were investigated with large-scale mainstream turbulence intensities of Tu∞ = 0.5% and Tu∞ = 21%. The effects of the showerhead coolant were evaluated at an engine-typical showerhead blowing ratio of Msh = 1.6, with three of the six rows of cooling holes in the showerhead directed towards the suction side of the airfoil. Experiments were conducted with a coolant-to-mainstream density ratio of DR = 1.6. An infrared camera was used to obtain spatially-resolved surface temperature measurements, which were corrected for conduction effects and converted to adiabatic effectiveness. The results showed that showerhead coolant had a strong impact on suction side adiabatic effectiveness levels under low mainstream turbulence. Although effectiveness levels increased with the showerhead operating, the suction side coolant jets increased dispersion of the showerhead coolant. Under high mainstream turbulence conditions, there was very little interaction between the showerhead coolant and the suction side coolant jets. Adiabatic effectiveness levels were considerably lower than those for the low turbulence case, which was partially due to increased dispersion of the showerhead coolant upstream of the suction side holes. The superposition model over-predicted adiabatic effectiveness levels under low mainstream turbulence conditions, but was very effective in predicting the combined performance of the showerhead and the suction side cooling holes under high mainstream turbulence conditions.

High Resolution Film Cooling Effectiveness Comparison of Axial and Compound Angle Holes on the Suction Side of a Turbine Vane

2006 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Film cooling adiabatic effectiveness for axial and compound angle holes on the suction side of a simulated turbine vane was investigated to determine the relative performance of these configurations. The effect of the surface curvature was also evaluated by comparing to previous curvature studies and flat plate film cooling results. Experiments were conducted for varying coolant density ratio, mainstream turbulence levels, and hole spacing. Results from these measurements showed that for mild curvature, 2r/d ≈ 160, flat plate results are sufficient to predict the cooling effectiveness. Furthermore, the compound angle injection improves adiabatic effectiveness for higher blowing ratios, similar to previous studies using flat plate facilities.

High-Resolution Film Cooling Effectiveness Comparison of Axial and Compound Angle Holes on the Suction Side of a Turbine Vane

2006 ◽  
Vol 129 (2) ◽  
pp. 202-211 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Adiabatic Effectiveness ◽  
Compound Angle

Film cooling adiabatic effectiveness for axial and compound angle holes on the suction side of a simulated turbine vane was investigated to determine the relative performance of these configurations. The effect of the surface curvature was also evaluated by comparing to previous curvature studies and flat plate film cooling results. Experiments were conducted for varying coolant density ratio, mainstream turbulence levels, and hole spacing. Results from these measurements showed that for mild curvature, 2r∕d≈160, flat plate results are sufficient to predict the cooling effectiveness. Furthermore, the compound angle injection improves adiabatic effectiveness for higher blowing ratios, similar to previous studies using flat plate facilities.

Film Cooling Effectiveness of Transonic Turbine Vane Suction Side With Compound-Angle Shaped Hole Configuration

2015 ◽  
Author(s):  
Shang-Feng Yang ◽  
Je-Chin Han ◽  
Alexander MirzaMoghadam ◽  
Ardeshir Riahi
Keyword(s):  
Transonic Flow ◽  
Film Cooling ◽  
Surface Film ◽  
Density Ratio ◽  
Suction Side ◽  
Flow Loop ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Compound Angle

This paper studies the effect of transonic flow velocity on local film cooling effectiveness distribution of turbine vane suction side, experimentally. A conduction-free Pressure Sensitive Paint (PSP) method is used to determine the local film cooling effectiveness. Tests were performed in a five-vane annular cascade at Texas A&M Turbomachinery laboratory blow-down flow loop facility. The exit Mach numbers are controlled to be 0.7, 0.9, and 1.1, from subsonic to transonic flow conditions. Three foreign gases N2, CO2 and Argon/SF6 mixture are selected to study the effects of three coolant-to-mainstream density ratios, 1.0, 1.5, and 2.0 on film cooling. Four averaged coolant blowing ratios in the range, 0.7, 1.0, 1.3 and 1.6 are investigated. The test vane features 3 rows of radial-angle cylindrical holes around the leading edge, and 2 rows of compound-angle shaped holes on the suction side. Results suggest that the PSP technique is capable of producing clear and detailed film cooling effectiveness contours at transonic condition. The effects of coolant to mainstream blowing ratio, density ratio, and exit Mach number on the vane suction-surface film cooling distribution are obtained, and the consequence results are presented and explained in this investigation.

Mean and Turbulent Velocity Profile Measurements on the Suction Side of a Film Cooled Turbine Vane

2013 ◽  
Author(s):  
John W. McClintic ◽  
Thomas E. Dyson ◽  
David G. Bogard ◽  
Sean D. Bradshaw
Keyword(s):  
Boundary Layer ◽  
Velocity Profile ◽  
Film Cooling ◽  
Large Scale ◽  
Suction Side ◽  
Profile Data ◽  
Downstream Location ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Layer Velocity

Boundary layer velocity and turbulence profiles were measured on the suction side of a scaled up, film-cooled turbine vane airfoil. There have been a number of previous studies of the velocity profile on a turbine vane, but few have taken velocity profile data with film cooling, and none have taken such data on the suction side of the vane. Velocity and turbulence profile data were taken at two locations on the suction side of the vane — one at a high curvature region and one further downstream in a low curvature region. Data were collected for high (20%) and low (0.5%) mainstream turbulence conditions. For the upstream, high curvature location, velocity and turbulence profiles were found with and without the showerhead blowing and within and outside of the merged showerhead coolant jet. The data for the low curvature, downstream location was taken with injection from the showerhead alone, a second upstream row of holes alone, and the combination of the two cases. It was found that the presence of an active upstream row of holes thickens the boundary layer and increases urms both within and beyond the extent of the boundary layer. Span-wise variations showed that these effects are strongest within the core of the coolant jets. At the downstream location, the boundary layer velocity profile was most strongly influenced by the row of holes immediately upstream of that location. Finally, turbulence integral length scale data showed the effect of large scale mainstream turbulence penetrating the boundary layer. The increase in turbulence, thickening of the boundary layer, and large scale turbulence all play important roles in row to row coolant interactions and affect the film cooling effectiveness.

High-Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations

2006 ◽  
Vol 129 (2) ◽  
pp. 294-302 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Density Ratio ◽  
Field Measurements ◽  
Suction Side ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

Adiabatic film cooling effectiveness of axial holes embedded within a transverse trench on the suction side of a turbine vane was investigated. High-resolution two-dimensional data obtained from infrared thermography and corrected for local conduction provided spatial adiabatic effectiveness data. Flow parameters of blowing ratio, density ratio, and turbulence intensity were independently varied. In addition to a baseline geometry, nine trench configurations were tested, all with a depth of 1∕2 hole diameter, with varying widths, and with perpendicular and inclined trench walls. A perpendicular trench wall at the very downstream edge of the coolant hole was found to be the key trench characteristic that yielded much improved adiabatic effectiveness performance. This configuration increased adiabatic effectiveness up to 100% near the hole and 40% downstream. All other trench configurations had little effect on the adiabatic effectiveness. Thermal field measurements confirmed that the improved adiabatic effectiveness that occurred for a narrow trench with perpendicular walls was due to a lateral spreading of the coolant and reduced coolant jet separation. The cooling levels exhibited by these particular geometries are comparable to shaped holes, but much easier and cheaper to manufacture.

Experimental Investigations of the Film Cooling Performance of a Micro-Tangential-Jet Scheme on a Gas Turbine Vane: Part 1 — Effectiveness

2012 ◽  
Author(s):  
O. Hassan ◽  
I. Hassan
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Experimental Investigations ◽  
Stream Velocity ◽  
Pressure Side ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Vane

This paper presents experimental investigations of the film cooling effectiveness performance of a Micro-Tangential-Jet (MTJ) Film cooling scheme on a gas turbine vane using transient Thermochromic Liquid Crystal (TLC) technique. The MTJ scheme is a micro-shaped scheme designed so that the secondary jet is supplied tangentially to the vane surface. The scheme combines the benefits of micro jets and tangential injection. The film cooling performance of one row of holes on both pressure and suction sides were investigated at a blowing ratio ranging from 0.5 to 1.5 on the pressure side and 0.25 to 0.625 on the suction side. The average density ratio during the investigations was 0.93, and the Reynolds Number was 1.4E+5, based on the free stream velocity and the main duct hydraulic diameter. The pitch to diameter ratio of the cooling holes is 5 on the pressure side and 6.5 on the suction side. The turbulence intensity during all investigations was 8.5%. Minor changes in the Mach number distribution around the airfoil surface were observed due to the presence of the MTJ scheme, compared with the case with no MTJ scheme. The investigations showed great film cooling performance for the MTJ scheme, high effectiveness values, and excellent lateral jet spreading. A 2-D coolant film was observed in the results, which is a characteristic of the continuous slot schemes only. The presence of this 2-D film layer helps minimize the rate of mixing between the main and coolant streams and provides uniform thermal loads on the surface. Furthermore, it was noticed that the rate of effectiveness decay on the suction side was less than that on the pressure side, while the lateral jet spreading on the pressure side was better than that of the suction side. The main disadvantage of the MTJ scheme is the increased pressure drop.

Effect of Midpassage Gap, Endwall Misalignment, and Roughness on Endwall Film-Cooling

2005 ◽  
Vol 128 (1) ◽  
pp. 62-70 ◽  
Author(s):  
N. D. Cardwell ◽  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Suction Side ◽  
Engine Operation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Severe Reduction ◽  
Turbine Vane ◽  
Endwall Film Cooling ◽  
High Pressure Coolant

To maintain acceptable turbine airfoil temperatures, film cooling is typically used whereby coolant, extracted from the compressor, is injected through component surfaces. In manufacturing a turbine, the first stage vanes are cast in either single airfoils or double airfoils. As the engine is assembled, these singlets or doublets are placed in a turbine disk in which there are inherent gaps between the airfoils. The turbine is designed to allow outflow of high-pressure coolant rather than hot gas ingestion. Moreover, it is quite possible that the singlets or doublets become misaligned during engine operation. It has also become of interest to the turbine community as to the effect of corrosion and deposition of particles on component heat transfer. This study uses a large-scale turbine vane in which the following two effects are investigated: the effect of a midpassage gap on endwall film cooling and the effect of roughness on endwall film cooling. The results indicate that the midpassage gap was found to have a significant effect on the coolant exiting from the combustor-turbine interface slot. When the gap is misaligned, the results indicate a severe reduction in the film-cooling effectiveness in the case where the pressure side endwall is below the endwall associated with the suction side of the adjacent vane.

High Resolution Film Cooling Effectiveness Measurements of Axial Holes Embedded in a Transverse Trench With Various Trench Configurations

2006 ◽  
Author(s):  
Scot K. Waye ◽  
David G. Bogard
Keyword(s):  
High Resolution ◽  
Film Cooling ◽  
Density Ratio ◽  
Field Measurements ◽  
Suction Side ◽  
Lateral Spreading ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Parameters ◽  
Adiabatic Effectiveness

Adiabatic film cooling effectiveness of axial holes embedded within a transverse trench on the suction side of a turbine vane was investigated. High resolution two dimensional data obtained from IR thermography and corrected for local conduction provided spatial adiabatic effectiveness data. Flow parameters of blowing ratio, density ratio, and turbulence intensity were independently varied. In addition to a baseline geometry, nine trench configurations were tested, all with a depth of 1/2 hole diameter, with varying widths, and with perpendicular and inclined trench walls. A perpendicular trench wall at the very downstream edge of the coolant hole was found to be the key trench characteristic that yielded much improved adiabatic effectiveness performance. This configuration increased adiabatic effectiveness up to 100% near the hole and 40% downstream. All other trench configurations had little effect on the adiabatic effectiveness. Thermal field measurements confirmed that the improved adiabatic effectiveness that occurred for a narrow trench with perpendicular walls was due a lateral spreading of the coolant and reduced coolant jet separation. The cooling levels exhibited by these particular geometries are comparable to shaped holes, but much easier and cheaper to manufacture.

Effects of Mid-Passage Gap, Endwall Misalignment and Roughness on Endwall Film-Cooling

2005 ◽  
Author(s):  
N. D. Cardwell ◽  
N. Sundaram ◽  
K. A. Thole
Keyword(s):  
Film Cooling ◽  
Large Scale ◽  
Suction Side ◽  
Engine Operation ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Severe Reduction ◽  
Turbine Vane ◽  
Endwall Film Cooling ◽  
High Pressure Coolant

To maintain acceptable turbine airfoil temperatures, film-cooling is typically used whereby coolant, extracted from the compressor, is injected through component surfaces. In manufacturing a turbine, the first stage vanes are cast in either single airfoils or double airfoils. As the engine is assembled, these singlets or doublets are placed in a turbine disk in which there are inherent gaps between the airfoils. The turbine is designed to allow outflow of high pressure coolant rather than hot gas ingestion. Moreover, it is quite possible that the singlets or doublets become misaligned during engine operation. It has also become of interest to the turbine community as to the effect of corrosion and deposition of particles on component heat transfer. This study uses a large scale turbine vane in which the following two effects are investigated: the effect of a mid-passage gap on endwall film-cooling and the effect of roughness on endwall film-cooling. The results indicate that the mid-passage gap was found to have a significant effect on the coolant exiting from the combustor-turbine interface slot. When the gap is misaligned, the results indicate a severe reduction in the film-cooling effectiveness in the case where the pressure side endwall is below the endwall associated with the suction side of the adjacent vane.

Effects of Surface Roughness and Near Hole Obstructions on Film Cooling Effectiveness

2007 ◽  
Author(s):  
Ruwan P. Somawardhana ◽  
David G. Bogard
Keyword(s):  
Surface Roughness ◽  
Film Cooling ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Single Row ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

For a film cooled turbine airfoil, significant degradation of adiabatic effectiveness can be caused by near-hole obstructions formed from deposition of contaminants. Since obstructions are a randomly occurring event, there are many variables to consider, namely shape, width, length, height, and position in relation to a film cooling hole. In addition to this, the level of overall surface roughness also must be considered. An investigation was conducted on obstruction characteristics for a single row of holes on the suction side of a simulated turbine vane. It was found that degradation due to near-hole obstructions only occurred when upstream obstructions were present. When directly upstream, degradation levels around 40% were observed and obstruction height was the dominating characteristic.

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