Adiabatic Film Cooling Effectiveness Measurements Throughout Multirow Film Cooling Arrays

2017 ◽  
Vol 139 (10) ◽  
Author(s):  
Greg Natsui ◽  
Zachary Little ◽  
Jayanta S. Kapat ◽  
Jason E. Dees
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
First Case ◽  
Lift Off

Adiabatic film cooling effectiveness measurements are obtained using pressure-sensitive paint (PSP) on a flat film cooled surface. The effects of blowing ratio and hole spacing are investigated for four multirow arrays comprised of eight rows containing 52 holes of 3.8 mm diameter with 20 deg inclination angles and hole length-to-diameter ratio of 11.2. The four arrays investigated have two different hole-to-hole spacings composed of cylindrical and diffuser holes. For the first case, lateral and streamwise pitches are 7.5 times the diameter. For the second case, pitch-to-diameter ratio is 14 in lateral direction and 10 in the streamwise direction. The holes are in a staggered arrangement. Adiabatic effectiveness measurements are taken for a blowing ratio range of 0.3–1.2 and a density ratio of 1.5, with CO2 injected as the coolant. A thorough boundary layer analysis is presented, and data were taken using hotwire anemometry with air injection, with boundary layer, and turbulence measurements taken at multiple locations in order to characterize the boundary layer. Local effectiveness, laterally averaged effectiveness, boundary layer thickness, momentum thickness, turbulence intensity, and turbulence length scale are presented. For the cylindrical holes, at the first row of injection, the film jets are still attached at a blowing ratio of 0.3. By a blowing ratio of 0.5, the jet is observed to lift off, and then impinge back onto the test surface. At a blowing ratio of 1.2, the jets lift off, but reattach much further downstream, spreading the coolant further along the test surface. A thorough uncertainty analysis has been conducted in order to fully understand the presented measurements and any shortcomings of the measurement technique. The maximum uncertainty of effectiveness and blowing ratio is 0.02 counts of effectiveness and 3%, respectively.

Adiabatic Film Cooling Effectiveness Measurements Throughout Multi-Row Film Cooling Arrays

2016 ◽  
Author(s):  
Greg Natsui ◽  
Zachary Little ◽  
Jay Kapat ◽  
Anthony Socotch ◽  
Anquan Wang ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Density Ratio ◽  
Diameter Ratio ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
First Case ◽  
Lift Off

Adiabatic film cooling effectiveness measurements are obtained using pressure-sensitive paint (PSP) on a flat film cooled surface. The effects of blowing ratio and hole spacing are investigated for four multi-row arrays comprised of 8 rows containing 52 holes of 3.8 mm diameter with 20° inclination angles and hole length-to-diameter ratio of 11.2. The four arrays investigated have two different hole-to-hole spacings composed of cylindrical and diffuser holes. For the first case, lateral and streamwise pitches are 7.5 times the diameter. For the second case, pitch-to-diameter ratio is 14 in lateral direction and 10 in the streamwise direction. The holes are in a staggered arrangement. Adiabatic effectiveness measurements are taken for a blowing ratio range of 0.3 to 1.2 and a density ratio of 1.5, with CO2 injected as the coolant. A thorough boundary layer analysis is presented, and data was taken using hotwire anemometry with air injection, with boundary layer and turbulence measurements taken at multiple locations in order to characterize the boundary layer. Local effectiveness, laterally averaged effectiveness, boundary layer thickness, momentum thickness, turbulence intensity and turbulence length scale are presented. For the cylindrical holes, at the first row of injection, the film jets are still attached at a blowing ratio of 0.3. By a blowing ratio of 0.5, the jet is observed to lift off, and then impinge back onto the test surface. At a blowing ratio of 1.2, the jets lift off, but reattach much further downstream, spreading the coolant further along the test surface. A thorough uncertainty analysis has been conducted in order to fully understand the presented measurements and any shortcomings of the measurement technique. The maximum uncertainty of effectiveness and blowing ratio is 0.02 counts of effectiveness and 3 percent respectively.

Combined Effects of Freestream Pressure Gradient and Density Ratio on the Film Cooling Effectiveness of Round and Shaped Holes on a Flat Plate

2016 ◽  
Author(s):  
Kyle R. Vinton ◽  
Travis B. Watson ◽  
Lesley M. Wright ◽  
Daniel C. Crites ◽  
Mark C. Morris ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Round Hole ◽  
Combined Effects ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

The combined effects of a favorable, mainstream pressure gradient and coolant-to-mainstream density ratio have been investigated. Detailed film cooling effectiveness distributions have been obtained on a flat plate with either cylindrical (θ = 30°) or laidback, fan-shaped holes (θ = 30°, β = γ = 10°) using the pressure sensitive paint (PSP) technique. In a low speed wind tunnel, both non-accelerating and accelerating flows were considered while the density ratio varied from 1–4. In addition, the effect of blowing ratio was considered, with this ratio varying from 0.5 to 1.5. The film produced by the shaped hole outperformed the round hole under the presence of a favorable pressure gradient for all blowing and density ratios. At the lowest blowing ratio, in the absence of freestream acceleration, the round holes outperformed the shaped holes. However, as the blowing ratio increases, the shaped holes prevent lift-off of the coolant and offer enhanced protection. The effectiveness afforded by both the cylindrical and shaped holes, with and without freestream acceleration, increased with density ratio.

Film-Cooling Performance of Anti-Vortex Hole on a Flat Plate

2011 ◽  
Author(s):  
Diganta P. Narzary ◽  
Christopher LeBlanc ◽  
Srinath Ekkad
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Poor Performance ◽  
Diameter Ratio ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Density Ratios

Film cooling performance of two hole geometries is evaluated on a flat plate surface with steady-state IR (infrared thermography) technique. The base geometry is a simple cylindrical hole design inclined at 30° from the surface with pitch-to-diameter ratio of 3.0. The second geometry is an anti-vortex design where the two side holes, also of the same diameter, branch out from the root at 15° angle. The pitch-to-diameter ratio is 6.0 between the main holes. The mainstream Reynolds number is 3110 based on the coolant hole diameter. Two secondary fluids — air and carbon-dioxide — were used to study the effects of coolant-to-mainstream density ratio (DR = 0.95 and 1.45) on film cooling effectiveness. Several blowing ratios in the range 0.5 –4.0 were investigated independently at the two density ratios. Results indicate significant improvement in effectiveness with anti-vortex holes compared to cylindrical holes at all the blowing ratios studied. At any given blowing ratio, the anti-vortex hole design uses 50% less coolant and provides at least 30–40% higher cooling effectiveness. The use of relatively dense secondary fluid improves effectiveness immediately downstream of the anti-vortex holes but leads to poor performance downstream.

The Flow and Film Cooling Effectiveness Following Injection through a Row of Holes

1980 ◽  
Vol 102 (3) ◽  
pp. 584-588 ◽  
Author(s):  
N. W. Foster ◽  
D. Lampard
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Boundary Layer Thickness ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Injection Angle ◽  
Blowing Ratio ◽  
Large Injection ◽  
Lateral Mixing ◽  
Lift Off

Using a mass transfer technique, detailed studies have been made of the effectiveness and flow downstream of a row of holes in the flat floor of a wind tunnel. The effects of variation of injection angle, upstream boundary layer, and hole spacing are described, and an assessment of the relative aerodynamic penalties is made. A small injection angle is shown to give the best cooling effectiveness at low blowing ratio while large injection angles are best at high blowing rates. Increasing the upstream boundary layer thickness reduces the effectiveness due to enhanced lateral mixing and film dilution. Small hole spacings give improved lateral coverage and alleviate jet lift-off effects.

A Three-Regime Based Method for Correlating Film Cooling Effectiveness for Cylindrical and Shaped Holes

2015 ◽  
Author(s):  
Lieke Wang ◽  
Mats Kinell ◽  
Hossein N. Najafabadi ◽  
Matts Karlsson
Keyword(s):  
Experimental Data ◽  
Film Cooling ◽  
Gas Turbines ◽  
Density Ratio ◽  
Transition Regime ◽  
Cooling Effectiveness ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

To cope with high temperature of the gas from combustor, cooling is often used in the hot gas components in gas turbines. Film cooling is one of the effective methods used in this application. Both cylindrical and fan-shaped holes are used in film cooling. There have been a number of correlations published for both cylindrical and fan-shaped holes regarding film cooling effectiveness. Unfortunately there are no definitive correlations for either cylindrical or fan-shaped holes. This is due to the nature of the complexity of film cooling where many factors influence its performance, e.g., blowing ratio, density ratio, surface angle, downstream distance, expansion angle, hole length, turbulence level, etc. A test rig using infrared camera was built to test the film cooling performance for a scaled geometry from a real nozzle guide vane. Both cylindrical and fan-shaped holes were tested. To correlate the experimental data, a three-regime based method was developed for predicting the film cooling effectiveness. Based on the blowing ratio, the proposed method divides the film cooling performance in three regimes: fully attached (or no jet lift-off), fully jet lift-off, and the transition regime in between. Two separate correlations are developed for fully attached and full jet lift-off regimes, respectively. The method of interpolation from these two regimes is used to predict the film cooling effectiveness for the transition regime, based on the blowing ratio. It has been found this method can give a good correlation to match the experimental data, for both cylindrical and fan-shaped holes. A comparison with literature was also carried out, and it showed a good agreement.

Combined Effects of Freestream Pressure Gradient and Density Ratio on the Film Cooling Effectiveness of Round and Shaped Holes on a Flat Plate

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Kyle R. Vinton ◽  
Travis B. Watson ◽  
Lesley M. Wright ◽  
Daniel C. Crites ◽  
Mark C. Morris ◽  
...  
Keyword(s):  
Pressure Gradient ◽  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Round Hole ◽  
Combined Effects ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

The combined effects of a favorable, mainstream pressure gradient and coolant-to-mainstream density ratio have been investigated. Detailed film cooling effectiveness distributions have been obtained on a flat plate with either cylindrical (θ = 30 deg) or laidback, fan-shaped holes (θ = 30 deg and β = γ = 10 deg) using the pressure-sensitive paint (PSP) technique. In a low-speed wind tunnel, both nonaccelerating and accelerating flows were considered, while the density ratio varied from 1 to 4. In addition, the effect of blowing ratio was considered, with this ratio varying from 0.5 to 1.5. The film produced by the shaped hole outperformed the round hole under the presence of a favorable pressure gradient for all the blowing and density ratios. At the lowest blowing ratio, in the absence of freestream acceleration, the round holes outperformed the shaped holes. However, as the blowing ratio increases, the shaped holes prevent lift-off of the coolant and offer enhanced protection. The effectiveness afforded by both the cylindrical and shaped holes, with and without freestream acceleration, increased with density ratio.

Full Coverage Film Cooling Performance for Combustor Cooling Manufactured Using DMLS

2016 ◽  
Author(s):  
Kyle R. Vinton ◽  
Sara Nahang-Toudeshki ◽  
Lesley M. Wright ◽  
Andrew Carter
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Substantial Impact ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Full Coverage ◽  
The Matrix ◽  
Film Cooling Holes

An experimental investigation of effusion film cooling has been completed for cylindrical, simple angle holes (θ = 20°), using a steady state, pressure sensitive paint (PSP) technique. The surface effectiveness measurements were obtained in a low speed wind tunnel where the average blowing ratio (M) was varied from 0.5 to 6. For all cases, the coolant–to–mainstream density ratio was fixed at DR = 1.0. The test surface was manufactured using direct metal laser sintering (DMLS), and was made to replicate full coverage film cooling typically seen for combustor cooling applications. The plate contained 10 staggered rows of film cooling holes, with P/D = 9.8 and S/D = 8.5. At blowing ratios greater than M = 1.0, the downstream film cooling effectiveness is greatly improved by the protection provided from the high momentum jets in the upstream rows. Within the latter-half of the matrix, the effectiveness measured on the surface gradually increased with each passing row. The combination of the holes made a substantial impact downstream, and the effect continued to grow all the way through the end of the plate. With the accumulation of the coolant above the surface, the coolant liftoff was mitigated and enhanced protection was observed on the surface. The DMLS manufacturing technique created surface and hole interior roughness. The hole interior roughness reduced the lateral average film cooling effectiveness by at least 50% when compared to previous investigations.

Evaluation of Massively-Parallel Spectral Element Algorithm for LES of Film-Cooling

2013 ◽  
Author(s):  
Andrew Duggleby ◽  
Josh L. Camp ◽  
Greg Laskowski
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Density Ratio ◽  
Time Integration ◽  
Spectral Element ◽  
Ideal Gas ◽  
Massively Parallel ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Lift Off

A blind Large-Eddy Simulation (LES) of film-cooling heat transfer is performed on a canonical cylindrical cooling hole geometry using a massively-parallel, geometrically-flexible, open-source spectral element solver NEK5000. The simulation is for a blowing-ratio of 1.0, density-ratio of 1.5, and Reynolds-number Reθ = 4,300 based on boundary layer momentum thickness and ReD = 32,000 based on hole diameter. A low-Mach ideal gas formulation is used to match the density ratio. A spectral-damping LES subgrid model is used which does not restrict time-stepping, allowing CFL numbers of 5–10 through characteristics time-integration. The numerical mesh resolves the boundary layer and coarsens to acceptable LES sizing in the free stream, resulting in 88 million grid points (410,464 elements at 5th order polynomial). For this blowing ratio, the coolant hole Mach number is too large for the low-Mach formulation (> 0.3). This results in faster hole velocities as opposed to fluid compression, effectively changing the momentum ratio leading to coolant lift-off as compared to experiment. The film-cooling effectiveness along centerline and spanwise locations of x/D = 2 and 8 are lower than experiment. Ideal parallel scaling is shown up to 256 processors and estimated to continue at ideal scaling to 2048 processors.

Numerical Simulation on the Effect of Cooling Hole Configuration on the Film Cooling Effectiveness in TBC Coated Turbine Vanes

2018 ◽  
Vol 0 (0) ◽  
Author(s):  
K. Parthiban ◽  
Muthukannan Duraiselvam ◽  
Shashank Kumar Jain ◽  
Saad Riaz ◽  
S. V. Aditya
Keyword(s):  
Numerical Simulation ◽  
Film Cooling ◽  
Coolant Flow ◽  
Test Surface ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Hole Configuration ◽  
Curved Hole ◽  
Lift Off

AbstractNumerical simulation was performed to investigate adiabatic film cooling effectiveness of cooling holes over thermal barrier coated superalloy substrate. Divergent, convergent-divergent and curved configuration of cooling holes were compared with the inclined cylindrical hole configuration. The coolant flow was strongly attached with the surface for 35º inclination. The film cooling effectiveness at different blowing ratios of 0.4, 0.8 and 1.2 was analysed. The study was carried out using realizable k-ϵ (RKE) model. The curved hole configuration provided enhanced cooling effectiveness even at 0.8 blowing ratio in comparison with other cases. The presence of curvature reduced the coolant velocity thereby preventing the detachment of jet from the surface and forming a very strong longitudinal film. The coolant jet starts detaching from the surface for blowing ratio higher than 1.2; the high momentum of the film cooling jet causes a lift off the surface. At 1.2 blowing ratio, a greater spread of coolant flow along the test surface was observed. Better film cooling effectiveness was evident at 0.8 and 1.2 blowing ratios. At 0.8, the enhancement in the overall film cooling effectiveness of divergent, convergent-divergent and curved hole configuration was about 14 %, 50 % and 59 %, respectively.

Influence of Coolant Density on Turbine Platform Film-Cooling With Stator–Rotor Purge Flow and Compound-Angle Holes

2014 ◽  
Vol 6 (4) ◽  
Author(s):  
Kevin Liu ◽  
Shang-Feng Yang ◽  
Je-Chin Han
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Fundamental Parameters ◽  
Blowing Ratio ◽  
Purge Flow ◽  
Cylindrical Holes ◽  
Exit Mach Number ◽  
Compound Angle

A detailed parametric study of film-cooling effectiveness was carried out on a turbine blade platform. The platform was cooled by purge flow from a simulated stator–rotor seal combined with discrete hole film-cooling. The cylindrical holes and laidback fan-shaped holes were accessed in terms of film-cooling effectiveness. This paper focuses on the effect of coolant-to-mainstream density ratio on platform film-cooling (DR = 1 to 2). Other fundamental parameters were also examined in this study—a fixed purge flow of 0.5%, three discrete-hole film-cooling blowing ratios between 1.0 and 2.0, and two freestream turbulence intensities of 4.2% and 10.5%. Experiments were done in a five-blade linear cascade with inlet and exit Mach number of 0.27 and 0.44, respectively. Reynolds number of the mainstream flow was 750,000 and was based on the exit velocity and chord length of the blade. The measurement technique adopted was the conduction-free pressure sensitive paint (PSP) technique. Results indicated that with the same density ratio, shaped holes present higher film-cooling effectiveness and wider film coverage than the cylindrical holes, particularly at higher blowing ratios. The optimum blowing ratio of 1.5 exists for the cylindrical holes, whereas the effectiveness for the shaped holes increases with an increase of blowing ratio. Results also indicate that the platform film-cooling effectiveness increases with density ratio but decreases with turbulence intensity.

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