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.

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 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 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.

An Experimental Investigation of a New Hybrid Film Cooling Scheme

2010 ◽  
Author(s):  
M. Ghorab ◽  
I. Hassan ◽  
T. Lucas
Keyword(s):  
Experimental Investigation ◽  
Film Cooling ◽  
Hybrid Film ◽  
Density Ratio ◽  
Thermochromic Liquid Crystal ◽  
Hybrid Scheme ◽  
Cooling Performance ◽  
Average Heat ◽  
Bending Effect ◽  
Turbine Airfoils

This paper presents an experimental investigation of the film cooling performance of a New Hybrid Film Cooling Scheme using Thermochromic Liquid Crystal technique. The new scheme has been designed to improve the film cooling performance of gas turbine airfoils. The scheme includes two consecutive film hole configurations with interior bending. The cooling performance of the new scheme was analyzed across blowing ratios of 0.5, 1.0 and 1.5, at a density ratio of 0.94. The results showed that the new scheme enhanced the local and the laterally averaged film cooling performance in terms of effectiveness, and net heat flux reduction in compared to other film hole configurations. The bending effect of the new scheme throttled the secondary flow causing it to spread widely over the downstream surfaces, hence enhancing the film cooling performance at low and high blowing ratios. The hybrid scheme provided an average heat transfer ratio near unity over the downstream surfaces at low and high blowing ratios.

Scaling of Performance for Varying Density Ratio Coolants on an Airfoil With Strong Curvature and Pressure Gradient Effects

2000 ◽  
Author(s):  
Marcia I. Ethridge ◽  
J. Michael Cutbirth ◽  
David G. Bogard
Keyword(s):  
Pressure Gradient ◽  
Film Cooling ◽  
Density Ratio ◽  
Flux Ratio ◽  
Leading Edge ◽  
Suction Side ◽  
Cooling Performance ◽  
Injection Angle ◽  
Adiabatic Effectiveness ◽  
Strong Curvature

An experimental study was conducted to investigate the film cooling performance on the suction side of a first stage turbine vane. Tests were conducted on a nine times scale vane model at density ratios of DR = 1.1 and 1.6 over a range of blowing conditions, 0.2 ≤ M ≤ 1.5 and 0.05 ≤ I ≤ 1.2. Two different mainstream turbulence intensity levels, Tu∞ = 0.5% and 20%, were also investigated. The row of coolant holes studied was located in a position of both strong curvature and strong favorable pressure gradient. In addition, its performance was isolated by blocking the leading edge showerhead coolant holes. Adiabatic effectiveness measurements were made using an infrared camera to map the surface temperature distribution. The results indicate that film cooling performance was greatly enhanced over holes with a similar 50° injection angle on a flat plate. Overall, adiabatic effectiveness scaled with mass flux ratio for low blowing conditions and with momentum flux ratio for high blowing conditions. However, for M < 0.5 there was a higher rate of decay for the low density ratio data. High mainstream turbulence had little effect at low blowing ratios, but degraded performance at higher blowing ratios.

Investigation of Detailed Film Cooling Effectiveness and Heat Transfer Distributions on a Gas Turbine Airfoil

1998 ◽  
Author(s):  
U. Drost ◽  
A. Bölcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Lateral Spreading ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Acceleration ◽  
Single Compound

In the present study film cooling effectiveness and heat transfer were systematically investigated on a turbine NGV airfoil employing the transient liquid crystal technique and a multiple regression procedure. Tests were conducted in a linear cascade at exit Reynolds numbers of 0.52e6, 1.02e6 and 1.45e6 and exit Mach numbers of 0.33, 0.62 and 0.8, at two mainstream turbulence intensities of 5.5% and 10%. The film cooling geometry consisted of a single compound angle row on the pressure side (PS), and a single or a double row on the suction side (SS). Foreign gas injection was used to obtain a density ratio of approximately 1.65, while air injection yielded a density ratio of unity. Tests were conducted for blowing ratios of 0.25 to 2.3 on the SS, and 0.55 to 7.3 on the PS. In general film cooling injection into a laminar BL showed considerably higher effectiveness in the near hole region, as compared to a turbulent BL. While mainstream turbulence had only a weak influence on SS cooling, higher effectiveness was noted on the PS at high turbulence due to increased lateral spreading of the coolant. Effects of mainstream Mach and Reynolds number were attributed to changes of the BL thickness and flow acceleration. Higher density coolant yielded higher effectiveness on both SS and PS, whereas heat transfer ratios were increased on the SS and decreased on the PS. Comparison of the single and double row cooling configurations on the SS revealed a better film cooling performance of the double row due to an improved film coverage and delayed jet separation.

Investigation of Detailed Film Cooling Effectiveness and Heat Transfer Distributions on a Gas Turbine Airfoil

1999 ◽  
Vol 121 (2) ◽  
pp. 233-242 ◽  
Author(s):  
U. Drost ◽  
A. Bo¨lcs
Keyword(s):  
Heat Transfer ◽  
Film Cooling ◽  
Density Ratio ◽  
Suction Side ◽  
Lateral Spreading ◽  
Double Row ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Flow Acceleration ◽  
Single Compound

In the present study film cooling effectiveness and heat transfer were systematically investigated on a turbine NGV airfoil employing the transient liquid crystal technique and a multiple regression procedure. Tests were conducted in a linear cascade at exit Reynolds numbers of 0.52e6, 1.02e6 and 1.45e6 and exit Mach numbers of 0.33, 0.62 and 0.8, at two mainstream turbulence intensities of 5.5 and 10 percent. The film cooling geometry consisted of a single compound angle row on the pressure side (PS), and a single or a double row on the suction side (SS). Foreign gas injection was used to obtain a density ratio of approximately 1.65, while air injection yielded a density ratio of unity. Tests were conducted for blowing ratios of 0.25 to 2.3 on the SS, and 0.55 to 7.3 on the PS. In general film cooling injection into a laminar BL showed considerably higher effectiveness in the near-hole region, as compared to a turbulent BL. While mainstream turbulence had only a weak influence on SS cooling, higher effectiveness was noted on the PS at high turbulence due to increased lateral spreading of the coolant. Effects of mainstream Mach and Reynolds number were attributed to changes of the BL thickness and flow acceleration. Higher density coolant yielded higher effectiveness on both SS and PS, whereas heat transfer ratios were increased on the SS and decreased on the PS. Comparison of the single and double row cooling configurations on the SS revealed a better film cooling performance of the double row due to an improved film coverage and delayed jet separation.

On Film Cooling Performance of a Turbine Vane Pressure Side: The Effect of Showerhead and Hole Alignment

2017 ◽  
Author(s):  
Hossein N. Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell
Keyword(s):  
Film Cooling ◽  
Guide Vane ◽  
Superior Performance ◽  
Pressure Side ◽  
Double Row ◽  
Cooling Performance ◽  
Single Row ◽  
Staggered Arrangement ◽  
Cooling Hole ◽  
Cylindrical Holes

This study uses transient IR-thermography to evaluate the effect of showerhead cooling and hole position on the performance of single-row cooling hole on the pressure side of a guide vane under engine representative conditions. The investigation includes both cylindrical and fan-shaped holes at two blowing conditions: 0.6 and 1.8. The influence of cooling hole alignment for these hole shapes in the performance of multiple row configurations was also studied in the presence of showerhead. For this purpose, double- and triple-row cases in staggered and non-staggered arrangements were considered for two blowing conditions, similar to the single row. The results are presented in terms of both adiabatic film effectiveness, AFE, and net heat flux reduction, NHFR. The showerhead effect was shown to be profound with regard to both AFE and NHFR for the cooling hole close to it. This holds for both hole shapes and blowing ratios. The overall film cooling performance, NHFR, of the rows further downstream of the showerhead and close to the trailing edge were affected marginally by the showerhead. The later cooling row showed superior performance compared to the other rows for fan-shaped holes in both presence and absence of shower-head at a low blowing ratio. For multiple row configurations, in general fan-shaped holes can maintain higher AFE in staggered alignment, while cylindrical holes benefit from consequent jet interaction between rows of cooling in a non-staggered arrangement. This holds for both investigated blowing ratios and double- and triple-rows. When considering NHFR, the results indicate that fan-shaped holes are less affected by the hole alignment. Cylindrical holes, however, can maintain superior performance in non-staggered alignment for all investigated cases except triple row under low blowing condition. The results also suggest that a double-row configuration in the presence of showerhead will benefit from an additional row mainly at high blowing ratios.

Film-Cooling Performance of a Turbine Vane Suction Side: The Showerhead Effect on Film-Cooling Hole Placement for Cylindrical and Fan-Shaped Holes

2015 ◽  
Vol 137 (9) ◽  
Author(s):  
Hossein Nadali Najafabadi ◽  
Matts Karlsson ◽  
Mats Kinell ◽  
Esa Utriainen
Keyword(s):  
Film Cooling ◽  
Gas Turbines ◽  
Convex Surface ◽  
Guide Vane ◽  
Suction Side ◽  
Surface Curvature ◽  
Medium Size ◽  
Double Row ◽  
Cooling Performance ◽  
Cooling Hole

In this paper, the transient IR-thermography method is used to investigate the effect of showerhead cooling on the film-cooling performance of the suction side of a turbine guide vane working under engine-representative conditions. The resulting adiabatic film effectiveness, heat transfer coefficient (HTC) augmentation, and net heat flux reduction (NHFR) due to insertion of rows of cooling holes at two different locations in the presence and absence of the showerhead cooling are presented. One row of cooling holes is located in the relatively high convex surface curvature region, while the other is situated closer to the maximum throat velocity. In the latter case, a double staggered row of fan-shaped cooling holes has been considered for cross-comparison with the single row at the same position. Both cylindrical and fan-shaped holes have been examined, where the characteristics of fan-shaped holes are based on design constraints for medium size gas turbines. The blowing rates tested are 0.6, 0.9, and 1.2 for single and double cooling rows, whereas the showerhead blowing is maintained at constant nominal blowing rate. The adiabatic film effectiveness results indicate that most noticable effects from the showerhead can be seen for the cooling row located on the higher convex surface curvature. This observation holds for both cylindrical and fan-shaped holes. These findings suggest that while the showerhead blowing does not have much impact on this cooling row from HTC enhancement perspective, it is influential in determination of the HTC augmentation for the cooling row close to the maximum throat velocity. The double-row fan-shaped cooling seems to be less affected by an upstream showerhead blowing when considering HTC enhancement, but it makes a major contribution in defining adiabatic film effectiveness. The NHFR results highlight the fact that cylindrical holes are not significantly affected by the showerhead cooling regardless of their position, but showerhead blowing can play an important role in determining the overall film-cooling performance of fan-shaped holes (for both the cooling row located on the higher convex surface curvature and the cooling row close to the maximum throat velocity), for both the single and the double row cases.

An Experimental Investigation of Film Cooling Performance of Louver Scheme

2010 ◽  
Author(s):  
M. Ghorab ◽  
I. Hassan ◽  
T. Lucas
Keyword(s):  
Experimental Investigation ◽  
Outer Surface ◽  
Film Cooling ◽  
Density Ratio ◽  
Life Time ◽  
Thermochromic Liquid Crystal ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Cooling Hole ◽  
Pass Through

The experimental investigation of the film cooling performance of louver schemes using Thermochromic Liquid Crystal technique is presented in this paper. The louver scheme allows the cooling flow to pass through a bend and impinges with the blade material, which then exits to the outer surface of the aerofoil through the film cooling hole. The cooling performance for the louver scheme was analyzed across blowing ratios of 0.5 to 1.5 at a density ratio of 0.94. The results showed that the louver scheme enhances the local and the average film cooling performances in terms of film cooling effectiveness, and net heat flux reduction better than other published film hole configurations. As well, it provides a widely spread of the secondary flow extensively over the downstream surface, thus, it enhances the lateral film cooling performance. Moreover, the louver scheme produces a lower heat transfer coefficient ratio than other film hole geometries at low and high blowing ratios. As a result, the louver scheme is expected to reduce the gas turbine airfoil’s outer surface temperature and provides superior cooling performance which increases airfoil life time.

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