scholarly journals Effect of In-Hole Roughness on Film Cooling From a Shaped Hole

2016 ◽  
Vol 139 (3) ◽  
Author(s):  
Robert P. Schroeder ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Core Flow ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Flow Through ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Cool Gas ◽  
Interior Walls

While much is known about how macrogeometry of shaped holes affects their ability to successfully cool gas turbine components, little is known about the influence of surface roughness on cooling hole interior walls. For this study, a baseline-shaped hole was tested with various configurations of in-hole roughness. Adiabatic effectiveness measurements at blowing ratios up to 3 showed that the in-hole roughness caused decreased adiabatic effectiveness relative to smooth holes. Decreases in area-averaged effectiveness grew more severe with larger roughness size and with higher blowing ratios for a given roughness. Decreases of more than 60% were measured at a blowing ratio of 3 for the largest roughness values. Thermal field and flowfield measurements showed that in-hole roughness caused increased velocity of core flow through the hole, which increased the jet penetration height and turbulence intensity resulting in an increased mixing between the coolant and the mainstream. Effectiveness reductions due to roughness were also observed when roughness was isolated to only the diffused outlet of holes, and when the mainstream was highly turbulent.

Effect of In-Hole Roughness on Film Cooling From a Shaped Hole

2016 ◽  
Author(s):  
Robert P. Schroeder ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Core Flow ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Flow Through ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Cool Gas ◽  
Interior Walls

While much is known about how macro-geometry of shaped holes affects their ability to successfully cool gas turbine components, little is known about the influence of surface roughness on cooling hole interior walls. For this study a baseline shaped hole was tested with various configurations of in-hole roughness. Adiabatic effectiveness measurements at blowing ratios up to three showed that in-hole roughness caused decreased adiabatic effectiveness relative to smooth holes. Decreases in area-averaged effectiveness grew more severe with larger roughness size and with higher blowing ratios for a given roughness. Decreases of more than 60% were measured at a blowing ratio of three for the largest roughness values. Thermal field and flowfield measurements showed that in-hole roughness caused increased velocity of core flow through the hole, which increased the jet penetration height and turbulence intensity resulting in increased mixing between coolant and the mainstream. Effectiveness reductions due to roughness were also observed when roughness was isolated to only the diffused outlet of holes, and when the mainstream was highly turbulent.

Adiabatic Effectiveness Measurements for a Baseline Shaped Film Cooling Hole

2014 ◽  
Author(s):  
Robert P. Schroeder ◽  
Karen A. Thole
Keyword(s):  
Film Cooling ◽  
Freestream Turbulence ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Cylindrical Holes ◽  
Shaped Hole ◽  
Adiabatic Effectiveness ◽  
Improved Performance ◽  
Density Ratios ◽  
Film Cooling Holes

Film cooling on airfoils is a crucial cooling method as the gas turbine industry seeks higher turbine inlet temperatures. Shaped film cooling holes are widely used in many designs given the improved performance over that of cylindrical holes. Although there have been numerous studies of shaped holes, there is no established baseline shaped hole to which new cooling hole designs can be compared. The goal of this study is to offer the community a shaped hole design, representative of proprietary and open literature holes that serves as a baseline for comparison purposes. The baseline shaped cooling hole design includes the following features: hole inclination angle of 30° with a 7° expansion in the forward and lateral directions; hole length of 6 diameters; hole exit-to-inlet area ratio of 2.5; and lateral hole spacing of 6 diameters. Adiabatic effectiveness was measured with this new shaped hole and was found to peak near a blowing ratio of 1.5 at density ratios of 1.2 and 1.5 as well as at both low and moderate freestream turbulence of 5%. Reductions in area-averaged effectiveness due to freestream turbulence at low blowing ratios were as high as 10%.

Implicit LES for Shaped-Hole Film Cooling Flow

2017 ◽  
Author(s):  
Todd A. Oliver ◽  
Joshua B. Anderson ◽  
David G. Bogard ◽  
Robert D. Moser ◽  
Gregory Laskowski
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Vortex Pair ◽  
Cooling Flow ◽  
Blowing Ratio ◽  
Eddy Simulation ◽  
Mean Temperature ◽  
Cooling Hole ◽  
The Mean ◽  
Adiabatic Effectiveness

Results of a recent joint experimental and computational investigation of the flow through a plenum-fed 7-7-7 shaped film cooling hole are presented. In particular, we compare the measured adiabatic effectiveness and mean temperature against implicit large eddy simulation (iLES) for blowing ratio approximately 2, density ratio 1.6, and Reynolds number 6000. The results overall show reasonable agreement between the iLES and the experimental results for the adiabatic effectiveness and gross features of the mean temperature field. Notable discrepancies include the centerline adiabatic effectiveness near the hole, where the iLES under-predicts the measurements by Δη ≈ 0.05, and the near-wall temperature, where the simulation results show features not present in the measurements. After showing this comparison, the iLES results are used to examine features that were not measured in the experiments, including the in-hole flow and the dominant fluxes in the mean internal energy equation downstream of the hole. Key findings include that the flow near the entrance to the hole is highly turbulent and that there is a large region of backflow near the exit of the hole. Further, the well-known counter-rotating vortex pair downstream of the hole is observed. Finally, the typical gradient diffusion hypothesis for the Reynolds heat flux is evaluated and found to be incorrect.

Sweeping Jet Film Cooling at High Blowing Ratio on a Turbine Vane

2019 ◽  
Author(s):  
Mohammad A. Hossain ◽  
Ali Ameri ◽  
James W. Gregory ◽  
Jeffrey P. Bons
Keyword(s):  
Boundary Layer ◽  
Film Cooling ◽  
Thermal Field ◽  
Guide Vane ◽  
Freestream Turbulence ◽  
Suction Surface ◽  
Blowing Ratio ◽  
Shaped Hole ◽  
D 12 ◽  
Nozzle Guide

Abstract Experimental and numerical investigations were conducted to study the effects of high blowing ratios and high freestream turbulence on sweeping jet film cooling. Experiments were conducted on a nozzle guide vane suction surface in a low-speed linear cascade. Experiments were performed at blowing ratios of 0.5–3.5 and freestream turbulence of 0.6% and 14.3%. Infrared thermography was used to estimate the adiabatic cooling effectiveness. Thermal field and boundary layer measurement were conducted at a cross-plane (x/D = 12) downstream of the hole exit. Results were compared with a baseline 777-shaped hole and showed that sweeping jet hole has a better cooling performance at high blowing ratios. The Thermal field data revealed that the coolant separates from the surface at high blowing ratios for the 777-shaped hole while the coolant remains attached for the sweeping jet hole. Boundary layer measurement further confirmed that due to the sweeping action of the jet, the jet momentum of the sweeping jet hole is much lower than that of a 777-shaped hole. Thus the coolant remains closer to the wall even at high blowing ratios. Large Eddy Simulations (LES) were performed for both sweeping jet and the 777-shaped hole to evaluate the interaction between the coolant and the freestream at the near hole regions. Results showed that 777-shaped hole has a strong jetting action at high blowing ratio that originates inside the hole breakout edges thus causing the jet to blow off from the surface. In contrast, the sweeping jet hole does not show this behavior due to its internal geometry and the sweeping action of the jet.

Measurements in Film Cooling With Lateral Injection: Adiabatic Effectiveness Values and Temperature Fields

2000 ◽  
Author(s):  
Rohit A. Oke ◽  
Terrence W. Simon
Keyword(s):  
Film Cooling ◽  
Thermal Field ◽  
Additional Data ◽  
Field Measurements ◽  
Diameter Ratio ◽  
Temperature Fields ◽  
Near Surface ◽  
Blowing Ratio ◽  
Adiabatic Effectiveness ◽  
Lift Off

Temperature fields were taken in a film cooling lateral injection configuration with pitch-to-hole-diameter of 3.0. These measurements were done with a traversing thermocouple. Momentum flux ratios of 0.25, 1.0 and 2.25 were used. Results are presented as fields of dimensionless temperatures, given by θ=Tprobe-T∞Tc-T∞. Near-surface values of this quantity over an unheated surface are adiabatic effectiveness values. Streamwise evolutions of these temperature fields are documented. It is seen how with higher blowing ratio the film cooling jets tend to lift off the surface. Comparisons are made to previous data and computational results. It is verified that lateral injection yields a more uniform distribution of effectiveness immediately downstream of injection. It is shown also how interaction of adjacent film cooling jets leads to such improved uniformity. This interaction depends on the pitch to diameter ratio, P/D. In order to study the effect of this parameter, additional data with P/D = 6.0 are presented. The present thermal field data complement previous velocity field measurements taken in the same flow.

Theoretical Film Cooling Performance of Multi Trench Configurations on Flat Plate

2013 ◽  
Author(s):  
Antar M. M. Abdala ◽  
Qun Zheng ◽  
Fifi N. M. Elwekeel
Keyword(s):  
Film Cooling ◽  
Additional Benefit ◽  
The Other ◽  
Low Flow ◽  
Computational Simulations ◽  
Cooling Performance ◽  
Blowing Ratio ◽  
Ansys Cfx ◽  
Shaped Hole ◽  
Adiabatic Effectiveness

In the present work, computational simulations was made using ANSYS CFX to predict the improvements in film cooling performance with multi trench. Multi-trench configuration consists of two trenches together, one wider trench and the other is narrow trench that extruded from the wider one. Several blowing ratios in the range (0.5:5) were investigated. By using the multi trench configuration, the coolant jet impacted the trench wall two times allowing increasing the spreading of coolant laterally in the trench, reducing jet velocity and jet completely covered on the surface. The results indicate that this configuration increased adiabatic effectiveness as blowing ratio increased. No observed film blow-off at all blowing ratios. The adiabatic film effectiveness of multi trench case outperformed the narrow trench case, laidback fan-shaped hole, fan-shaped hole and cylinder hole at different blowing ratios. An additional benefit is the low flow rate will provide the same cooling effect by using multi trench configuration.

scholarly journals Effect of Mainstream Velocity on the Optimization of a Fan-Shaped Film-Cooling Hole on a Flat Plate

Energies ◽  
2021 ◽  
Vol 14 (12) ◽  
pp. 3573
Author(s):  
Soo-In Lee ◽  
Jin-Young Jung ◽  
Yu-Jin Song ◽  
Jae-Su Kwak
Keyword(s):  
Flat Plate ◽  
Film Cooling ◽  
Density Ratio ◽  
Cooling Effectiveness ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Pressure Sensitive ◽  
Expansion Angle ◽  
Cooling Hole ◽  
Shaped Hole

In this study, the effect of mainstream velocity on the optimization of a fan-shaped hole on a flat plate was experimentally investigated. The experiment was conducted by changing the forward expansion angle (βfwd), lateral expansion angle (βlat), and metering length ratio (Lm/D) of the film-cooling hole. A total of 13 cases extracted using the Box–Behnken method were considered to examine the effect of the shape parameters of the film-cooling hole under a 90 m/s mainstream velocity condition, and the results were compared with the results derived under a mainstream velocity of 20 m/s. One density ratio (DR = 2.0) and a blowing ratio (M) ranging from 1.0 to 2.5 were considered, and the pressure-sensitive paint (PSP) technique was applied for the film-cooling effectiveness (FCE). As a result of the experiment, the optimized hole showed a 49.3% improvement in the overall averaged FCE compared to the reference hole with DR = 2.0 and M = 2.0. As the blowing ratio increased, the hole exit area tended to increase, and this tendency was the same as that in the 20 m/s mainstream condition.

Effect of Row Spacing on the Accuracy of Film Cooling Superposition Method

2018 ◽  
Author(s):  
Lang Wang ◽  
Xueying Li ◽  
Jing Ren ◽  
Hongde Jiang
Keyword(s):  
Film Cooling ◽  
Row Spacing ◽  
Superposition Method ◽  
Round Hole ◽  
Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Shaped Hole ◽  
The Difference ◽  
Density Ratios

Film cooling technique is widely used in a modern gas turbine. Many applications in hot sections require multiple film cooling rows to get better cooled. In most situation, the additive effect is computed using Sellers superposition method, but it is not accurate when the hole rows are close to each other. In this paper, row spacing between two rows of cooling hole was investigated by numerical method, which was validated by PSP results. The validation experiments are performed on flat test bench and the freestream is maintained at 25m/s. The inlet boundary conditions of numerical simulations were same with the experiment. Both round hole and shaped hole were investigated at blowing ratio M = 0.5, density ratios DR = 1.5 and row spacing S/D = 6, 10, 15, 20. It is found that the round hole results by Sellers method are similar to experiment results only at large row spacing, and the results of Sellers are always higher than experimental results. The boundary layer has a big effect on cooling effectiveness for round hole, but very little effect on shaped hole. When the row spacing increase, the difference between experiment and prediction become smaller. The vortex is the major factor to effect the accuracy of superposition method.

Performance Evaluation of a Novel Film-Cooling Hole

2012 ◽  
Vol 134 (10) ◽  
Author(s):  
Ki-Don Lee ◽  
Kwang-Yong Kim
Keyword(s):  
Film Cooling ◽  
Density Ratio ◽  
Three Dimensional ◽  
Lateral Spreading ◽  
The Novel ◽  
Cooling Performance ◽  
Film Cooling Effectiveness ◽  
Blowing Ratio ◽  
Cooling Hole ◽  
Shaped Hole

This paper presents a numerical investigation of the film-cooling performance of a novel film-cooling hole in comparison with a fan-shaped hole. The novel shaped hole is designed to increase the lateral spreading of coolant on the cooling surface. The film-cooling performance of the novel shaped hole is evaluated at a density ratio of 1.75 and the range of the blowing ratio of 0.5–2.5. The simulations were performed using three-dimensional Reynolds-averaged Navier–Stokes analysis with the SST k-ω model. The numerical results for the fan-shaped hole show very good agreement with the experimental data. For the blowing ratio of 0.5, the novel shaped film-cooling hole shows a similar cooling performance as the fan-shaped hole. However, as the blowing ratio increases, the novel shaped hole shows greatly improved lateral spreading of the coolant and the cooling performance in terms of the film-cooling effectiveness in comparison with the fan-shaped hole.

Pitfalls of Fan-Shaped Hole Design: Insights From Experimental Measurement of In-Hole Flow Through MRV

2017 ◽  
Author(s):  
Emin Issakhanian ◽  
Christopher J. Elkins ◽  
John K. Eaton
Keyword(s):  
Film Cooling ◽  
Vortex Pair ◽  
Cooling Effectiveness ◽  
Cooling Flow ◽  
Magnetic Resonance Velocimetry ◽  
Cooling Hole ◽  
Good Improvement ◽  
Flow Through ◽  
Shaped Hole ◽  
Lift Off

Film cooling jets from discrete round holes are very susceptible to jet lift-off which reduces surface effectiveness. Since the experiments of Goldstein et al. (1974), shaped holes have become prominent for improved coolant coverage. Fan-shaped holes are the most common design and have shown good improvement over round holes. However, fan-shaped holes introduce additional parameters to the already complex task of modeling cooling effectiveness. This study presents velocity and vorticity fields measured using high-resolution magnetic resonance velocimetry (MRV) to study three different fan-shaped hole geome tries at two blowing ratios. Because MRV does not require line of sight, it provides otherwise hard to obtain experimental data of the flow within the film cooling hole in addition to the mainflow measurements. By allowing measurement within the cooling hole, MRV shows how poor choice of diffuser start point and angle can be detrimental to film cooling if overall hole length and cooling flow velocity are not properly accounted for in the design. The downstream effect of these choices on the jet height and counter-rotating vortex pair is also observed.

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