Analysis of film cooling performance of advanced tripod hole geometries with and without manufacturing features

Heat transfer experiments were done on a flat plate to study the effect of internal counter-flow backside cooling on adiabatic film cooling effectiveness and heat transfer coefficient. In addition, the effects of density ratio (DR), blowing ratio (BR), diagonal length over diameter (L/D) ratio, and Reynolds number were studied using this new configuration. The results are compared to a conventional plenum fed case. Data were collected up to X/D = 23 where X = 0 at the holes, an S/D = 1.65 and L/D = 1 and 2. Testing was done at low L/D ratios since short holes are normally found in double wall cooling applications in turbine components. A DR of 2 was used in order to simulate engine-like conditions and this was compared to a DR of 0.92 since relevant research is done at similar low DR. The BR range of 0.5 to 1.5 was chosen to simulate turbine conditions as well. In addition, previous research shows that peak effectiveness is found within this range. Infrared (IR) thermography was used to capture temperature contours on the surface of interest and the images were calibrated using a thermocouple and data analyzed through MATLAB software. A heated secondary fluid was used as ‘coolant’ in the present study. A steady state heat transfer model was used to perform the data reduction procedure. Results show that backside cooling configuration has a higher adiabatic film cooling effectiveness when compared to plenum fed configurations at the same conditions. In addition, the trend for effectiveness with varying BR is reversed when compared with traditional plenum fed cases. Yarn flow visualization tests show that flow exiting the holes in the backside cooling configuration is significantly different when compared to flow exiting the plenum fed holes. We hypothesize that backside cooling configuration has flow exiting the holes in various directions, including laterally, and behaving similar to slot film cooling, explaining the differences in trends. Increasing DR at constant BR shows an increase in adiabatic effectiveness and HTC in both backside cooling and plenum fed configurations due to the decreased momentum of the coolant, making film attachment to the surface more probable. The effects of L/D ratio in this study were negligible since both ratios used were small. This shows that the coolant flow is still underdeveloped at both L/D ratios. The study also showed that increasing turbulence through increasing Reynolds number decreased adiabatic effectiveness.

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“…Shaped holes create anti kidney vortices, counter-acting this effect. Ramesh et al [8] show a similar effect using tripod holes.…”

Section: Film Cooling Relevant Literaturementioning

confidence: 77%

“…In previous experiments, such as Ramesh et al [8], Rogers et al [12], Ligrani et al [13], among others, a 1D semi-infinite transient conduction model is used. Due to the low L/D ratios used in this study, coupled with backside cooling, this traditional method is no longer appropriate.…”

Section: Data Reduction Methodsmentioning

confidence: 99%

Effects on Heat Transfer Coefficient and Adiabatic Effectiveness in Combined Backside and Film Cooling With Short-Hole Geometry

Rosa

Pandit

et al. 2019

Volume 5B: Heat Transfer

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“…This performance is not observed for any other film cooing hole geometries, including the baseline shaped-hole geometry. The case of θ = 22:5 °with the largest distance between the primary and side holes is the typical tripod shape that is studied by other investigators [12][13][14][15]. In this geometry, the three cylindrical holes flow separately, and the cooling flows do not have many interactions.…”

Section: Resultsmentioning

confidence: 98%

“…They concluded that slot ejection gave the highest effectiveness amongst the three tested configurations and the tripod holes outperformed the cylindrical holes. Ramesh et al [14,15] reported the film cooling effectiveness values of tripod antivortex injection holes over the pressure and suction surfaces of a nozzle guide using infrared thermography. They examined cylindrical, shaped, tripod, and shaped-tripod holes for a blowing ratio range of 0.5 to 4.…”

Section: Introductionmentioning

confidence: 99%

Experimental Film Cooling Effectiveness of Three-Hole-Branch Circular Holes

Fan

Taslim

2021

International Journal of Rotating Machinery

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A three-hole-branch geometry for film cooling is proposed. Each branch is made up of a streamwise 30°-angled circular hole with a circular hole of the same diameter on each side of it. These three holes share the same inlet area on the coolant supply side. Three side hole inclination angles of 30°, 37.5°, and 45° and three branch angles (the angle between the main and side holes) generated nine configurations that were tested for four blowing ratios of 0.5, 1, 1.5, and 2. To their benefits, these straight-through circular holes could easily be laser drilled on the airfoils or other gas turbine hot section surfaces. For comparative evaluation of these film hole geometries, the commonly used 7°-7°-7° diffusion hole geometry with the same inlet hole diameter was tested as a baseline under otherwise identical conditions. The pressure-sensitive paint (PSP) technique was utilized to test these geometries for their film cooling effectiveness. Depending on the branch geometry, for the same amount of coolant, some configurations were found to be superior to the baseline case for stream- or spanwise film cooling distributions while for the steeper side hole angles, these branched holes did not perform as well as the baseline case. The main conclusion is that the three holes with the same inclination angle of 30° exhibited the best film cooling effectiveness performance including the baseline geometry.

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“…However, the processing space of the blade is extremely small, especially for the blade with double-wall cooling, to apply EDM, which makes the conical angle deviations still exist in the present blade. Sridharan et al [6] and Montomoli et al [7] studied the effect of the filleted edge on the film cooling performance using the advanced tripod hole and fanshaped hole, respectively, while their conclusions were a little different. In addition, Cerantola et al [8] also studied the effect of the fillet caused by AM on the cylindrical film hole.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty Quantification of the Effects of Small Manufacturing Deviations on Film Cooling: A Fan-Shaped Hole

Shi

Chen

et al. 2019

Aerospace

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The film cooling holes in the blade of modern gas turbines have commonly been manufactured by laser drilling, Electric Discharge Machining (EDM), and Additive Manufacturing (AM) in recent years. These manufacturing processes often result in small geometric deviations, such as conical angles, filleted edges, and diameter deviations of the hole, which can lead to deviations on the distribution of adiabatic cooling effectiveness (η) values, the value of the discharge coefficient (Cd), and the characteristic of the in-hole flow field. The current study employed flat plate fan-shaped film cooling holes with length-to-diameter values (L/D) equal to 3.5 and six to investigate the effects of these manufacturing deviations on the distribution of η values, the value of Cd, and the characteristic of in-hole flow field. An Uncertainty Quantification (UQ) analysis using the Polynomial Chaos Expansion (PCE) model was carried out to quantify the uncertainty in the values of η and Cd. The statistical characteristics (mean values, standard deviation (Std) values, and Probability Density Function (PDF) values) of η and Cd were also calculated. The results show that conical angle deviations exert no visible changes on the value of η. However, the Cd value decreases by 6.2% when the conical angle changes from 0–0.5°. The area averaged adiabatic cooling effectiveness ( η = ) decreases by 3.4%, while the Cd increases by 15.2% with the filleted edge deviation existing alone. However, the deviation value of η = is 7.6%, and that of Cd is 25.7% with the filleted edge deviation and the diameter deviation existing.

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Analysis of film cooling performance of advanced tripod hole geometries with and without manufacturing features

Cited by 36 publications

References 22 publications

Effects on Heat Transfer Coefficient and Adiabatic Effectiveness in Combined Backside and Film Cooling With Short-Hole Geometry

Effects on Heat Transfer Coefficient and Adiabatic Effectiveness in Combined Backside and Film Cooling With Short-Hole Geometry

Experimental Film Cooling Effectiveness of Three-Hole-Branch Circular Holes

Uncertainty Quantification of the Effects of Small Manufacturing Deviations on Film Cooling: A Fan-Shaped Hole

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