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.

Experimental Investigations of the Effect of Scheme Exit Height and Double Row Injection on the Film Cooling Performance of a Micro Tangential Jet Scheme: Part I — Pressure Side

2015 ◽  
Author(s):  
O. Hassan ◽  
I. Hassan
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Average Density ◽  
Hole Diameter ◽  
Experimental Investigations ◽  
Pressure Side ◽  
Thermochromic Liquid Crystal ◽  
Double Row ◽  
Cooling Performance

This paper presents experimental investigations of the effect of scheme exit height and double jet injection on the film cooling performance of a Micro-Tangential-Jet (MTJ) scheme. The investigations were conducted over a gas turbine vane pressure side using the transient Thermochromic Liquid Crystal technique. The suction side investigations are presented in Part II of the present paper. The MTJ scheme is a micro-shaped scheme designed so that the micro-sized secondary jet is supplied tangentially to the vane surface. The scheme combines the benefits of micro jets and tangential injection. In order to investigate the effect of scheme exit height, one row of the MTJ scheme with 1.0 hole diameter exit height and another row with 1.5 hole diameter exit height were investigated. Meanwhile, to investigate the effect of double injection, one row of the MTJ scheme in staggered arrangement with one row of fan-shaped scheme was investigated. The investigations were conducted at various blowing ratios, calculated based on the scheme exit area. The average density ratio, turbulence intensity and Reynolds number were 0.93, 8.5, and 1.4E+5, respectively. The investigations showed that the smaller the exit height, the better the film cooling performance. Meanwhile, double injecting the secondary stream from MTJ and shaped schemes did not result in significant film cooling enhancement due to the enhanced turbulence over the vane surface.

Experimental Investigation of Louver Cooling Scheme on Gas Turbine Vane Suction Side

2011 ◽  
Author(s):  
T. Elnady ◽  
O. Hassan ◽  
I. Hassan ◽  
L. Kadem ◽  
T. Lucas
Keyword(s):  
Experimental Investigation ◽  
Gas Turbine ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Thermochromic Liquid Crystal ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cylindrical Holes

An experimental investigation has been performed to measure the film cooling performance of louver scheme over a scaled vane of high-pressure gas turbine using a two-dimensional cascade. Two rows of axially oriented louver scheme are used to cool the suction side and their performance is compared with two similar rows of standard cylindrical holes. The effect of hole location on the cooling performance is investigated for each row individually, then the row interaction is investigated for both rows at four different blowing ratios ranging from 1 to 2 with a 0.9 density ratio. The exit Reynolds number based on the true chord is 1.5E5 and exit Mach number is 0.23. The temperature distribution on the vane is mapped using a transient Thermochromic Liquid Crystal (TLC) technique to obtain the local distributions of the heat transfer coefficient and film cooling effectiveness. The louver scheme shows a superior cooling effectiveness than that of the cylindrical holes at all blowing ratios in terms of protection and lateral coverage. The row location highly affects the cooling performance for both the louver and cylindrical scheme.

The Effects of Obstructions on Film Cooling Effectiveness on the Suction Side of a Gas Turbine Vane

2006 ◽  
Author(s):  
Patricia Demling ◽  
David G. Bogard
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Suction Side ◽  
Temperature Profiles ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Turbine Vane ◽  
Cooling Hole ◽  
Adiabatic Effectiveness

The effects of obstructions on film cooling performance on a scaled-up 1st stage turbine vane will be discussed. Experimental results show that obstructions located upstream or inside of a film cooling hole will degrade adiabatic effectiveness up to 80% of the levels found with no obstructions. Downstream obstructions had little effect on performance. The location where the upstream obstructions ceased to degrade adiabatic effectiveness was determined and temperature profiles were constructed to determine how the upstream obstructions were affecting the mainstream and coolant flow.

Experimental Investigations of the Effect of Scheme Exit Height and Double Row Injection on the Film Cooling Performance of a Micro Tangential Jet Scheme: Part II — Suction Side

2015 ◽  
Author(s):  
O. Hassan ◽  
I. Hassan
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Average Density ◽  
Experimental Investigations ◽  
Stream Velocity ◽  
Thermochromic Liquid Crystal ◽  
Double Row ◽  
Cooling Performance ◽  
Staggered Arrangement

This paper presents experimental investigations of the effect of scheme exit height and double jet injection on the film cooling performance of a Micro-Tangential-Jet (MTJ) scheme on the suction side of a gas turbine vane using the transient Thermochromic Liquid Crystal (TLC) technique. In part I of the present paper the investigations over the pressure side are presented. The MTJ scheme is a micro-shaped scheme designed so that the micro-sized secondary jet is supplied tangentially to the vane surface. In order to investigate the effect of scheme exit height, one row of the MTJ scheme with exit height of 1.5 hole diameters was investigated and compared with the case of 1.0 hole diameter scheme exit height. Meanwhile, to investigate the effect of double injection, one row of the MTJ scheme in staggered arrangement with one row of fan-shaped scheme was investigated. The investigations were conducted at a blowing ratio, calculated based on the scheme exit area, ranging from 0.25 to 0.625. 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 6.5, and the turbulence intensity during all investigations was 8.5%. The increase in the MTJ scheme exit height did not result in significant change in the Mach number distribution. Moreover, increasing the scheme exit height resulted in enhanced effectiveness performance. The enhanced effectiveness was accompanied with Heat Transfer Coefficient (HTC) ratio augmentation as well. As a result, a reduction in the Net Heat Flux Reduction (NHFR) accompanied increasing the scheme exit height from 1.0 to 1.5 hole diameters. Besides, adding a row of shaped schemes in front of the MTJ scheme result in significant effectiveness reduction, compared to the case of single row injection. The latter was attributed to the presence of the shaped scheme inclination angle that result in enhanced secondary stream loss due to the perpendicular momentum component to the vane surface accompanying the shaped scheme secondary jet.

Numerical Investigation of Coolant-to-Mainstream Scaling Parameters With Film Cooling on Pressure and Suction Side of a Gas Turbine Blade

2017 ◽  
Author(s):  
Lingyu Zeng ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Gas Turbine ◽  
Film Cooling ◽  
Momentum Flux ◽  
Velocity Ratio ◽  
Density Ratio ◽  
Flux Ratio ◽  
Suction Side ◽  
Pressure Side ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness

Most experiments of blade film cooling are conducted with density ratio lower than that of turbine conditions. In order to accurately model the performance of film cooling under a high density ratio, choosing an appropriate coolant to mainstream scaling parameter is necessary. The effect of density ratio on film cooling effectiveness on the surface of a gas turbine twisted blade is investigated from a numerical point of view. One row of film holes are arranged in the pressure side and two rows in the suction side. All the film holes are cylindrical holes with a pitch to diameter ratio P/d = 8.4. The inclined angle is 30°on the pressure side and 34° on the suction side. The steady solutions are obtained by solving Reynolds-Averaged-Navier-Stokes equations with a finite volume method. The SST turbulence model coupled with γ-θ transition model is applied for the present simulations. A film cooling experiment of a turbine vane was done to validate the turbulence model. Four different density ratios (DR) from 0.97 to 2.5 are studied. To independently vary the blowing ratio (M), momentum flux ratio (I) and velocity ratio (VR) of the coolant to the mainstream, seven conditions (M varying from 0.25 to 1.6 on the pressure side and from 0.25 to 1.4 on the suction side) are simulated for each density ratio. The results indicate that the adiabatic effectiveness increases with the increase of density ratio for a certain blowing ratio or a certain momentum flux ratio. Both on the pressure side and suction side, none of the three parameters listed above can serve as a scaling parameter independent of density ratio in the full range. The velocity ratio provides a relative better collapse of the adiabatic effectiveness than M and I for larger VRs. A new parameter describing the performance of film cooling is introduced. The new parameter is found to be scaled with VR for nearly the whole range.

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.

Effects of Obstructions and Surface Roughness on Film Cooling Effectiveness With and Without a Transverse Trench

2008 ◽  
Vol 131 (1) ◽  
Author(s):  
Ruwan P. Somawardhana ◽  
David G. Bogard
Keyword(s):  
Surface Roughness ◽  
Film Cooling ◽  
Suction Side ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Surface Conditions ◽  
Turbine Vane ◽  
Cylindrical Holes ◽  
Better Than

Recent studies have shown that film cooling with holes embedded in a shallow trench significantly improves cooling performance. In this study, the performance of shallow trench configurations was investigated for simulated deteriorated surface conditions, i.e., increased surface roughness and near-hole obstructions. Experiments were conducted on the suction side of a scaled-up simulated turbine vane. Results from the study indicated that as much as 50% degradation occurred with upstream obstructions, but downstream obstructions actually enhanced film cooling effectiveness. However, the transverse trench configuration performed significantly better than the traditional cylindrical holes, both with and without obstructions and almost eliminated the effects of both surface roughness and obstructions.

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.

Film Cooling Jet Injection Effect in Heat Transfer Coefficient Augmentation for the Pressure Side Cooling of Turbine Vane

2014 ◽  
Author(s):  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell ◽  
Esa Utriainen
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Film Cooling ◽  
Density Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Pressure Side ◽  
Time Resolved ◽  
Turbine Vane

Improving film cooling performance of turbine vanes and blades is often achieved through application of multiple arrays of cooling holes on the suction side, the showerhead region and the pressure side. This study investigates the pressure side cooling under the influence of single and multiple rows of cooling in the presence of a showerhead from a heat transfer coefficient augmentation perspective. Experiments are conducted on a prototype turbine vane working at engine representative conditions. Transient IR thermography is used to measure time-resolved surface temperature and the semi-infinite method is utilized to calculate the heat transfer coefficient on a low conductive material. Investigations are performed for cylindrical and fan-shaped holes covering blowing ratio 0.6 and 1.8 at density ratio of about unity. The freestream turbulence is approximately 5% close to the leading edge. The resulting heat transfer coefficient enhancement, the ratio of HTC with to that without film cooling, from different case scenarios have been compared to showerhead cooling only. Findings of the study highlight the importance of showerhead cooling to be used with additional row of cooling on the pressure side in order to reduce heat transfer coefficient enhancement. In addition, it is shown that extra rows of cooling will not significantly influence heat transfer augmentation, regardless of the cooling hole shape.

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