Effect of High Freestream Turbulence on Flowfields of Shaped Film Cooling Holes

Schroeder, Robert P.; Thole, Karen A.

doi:10.1115/1.4032736

Cited by 58 publications

(24 citation statements)

References 19 publications

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“…A trip wire at x/D ¼ À33 caused transition to a turbulent boundary layer. Per boundary layer profiles previously reported by Schroeder and Thole [11], the boundary layer was fully turbulent at x/D ¼ À2. Table 1 provides characterization of the mainstream approach boundary layer.…”

Section: Experimental Facility and Methodssupporting

confidence: 56%

“…Absence of the delayed liftoff was due to strong dilution of coolant caused by freestream turbulence, rather than due to a significant change in dynamics of the flowfield. Schroeder and Thole [11] previously showed that there were no significant differences in mean velocities between the low and high freestream turbulence cases. The CRVP was of similar size and had similar velocities between the Tu 1 ¼ 0.5% and 13.2% cases.…”

Section: Resultsmentioning

confidence: 90%

“…3(a)-3(b). Note that PIV measurements were made in the same manner as previously reported [11]. For both setups in the present study, mainstream and coolant were equally seeded with di-ethylhexyl-sebacate (DEHS) droplets that followed the flow due to their low Stokes number (maximum Stk ¼ 0.010).…”

Section: Experimental Facility and Methodsmentioning

confidence: 99%

“…Measurements were performed at high blowing ratios up to M ¼ 3 and were performed at both low and high freestream turbulence intensities. To provide a comprehensive understanding, thermal field data are complemented by previously measured flow field data [11] at the same conditions. Besides adding to our understanding of shaped hole performance, data of the present study are useful for benchmarking of computational fluid dynamics simulations and qualification of new film cooling experimental facilities.…”

Section: Previous Studiesmentioning

confidence: 99%

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Thermal Field Measurements for a Shaped Hole at Low and High Freestream Turbulence Intensity

Schroeder

Thole

2016

Journal of Turbomachinery

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Shaped holes are increasingly selected for airfoil cooling in gas turbines due to their superior performance over that of cylindrical holes, especially at high blowing ratios. The performance of shaped holes is regarded to be the result of the diffused outlet, which slows and laterally spreads coolant, causing coolant to remain close to the wall. However, few thermal field measurements exist to verify this behavior at high blowing ratio or to evaluate how high freestream turbulence alters the coolant distribution in jets from shaped holes. The present study reports measured thermal fields, along with measured flowfields, for a shaped hole at blowing ratios up to three at both low and high freestream turbulence intensities of 0.5% and 13.2%. Thermal fields at low freestream turbulence intensity showed that the coolant jet was initially attached, but far downstream of the hole the jet lifted away from the surface due to the counter-rotating vortex pair. Elevated freestream turbulence intensity was found to cause strong dilution of the coolant jet and also increased dispersion, almost exclusively in the lateral as opposed to the vertical direction. Dominance of lateral dispersion was due to the influence of the wall on freestream eddies, as indicated from changes in turbulent shear stress between the low and high freestream turbulence cases.

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Section: Experimental Facility and Methodssupporting

confidence: 56%

Section: Resultsmentioning

confidence: 90%

Section: Experimental Facility and Methodsmentioning

confidence: 99%

Section: Previous Studiesmentioning

confidence: 99%

See 2 more Smart Citations

Thermal Field Measurements for a Shaped Hole at Low and High Freestream Turbulence Intensity

Schroeder

Thole

2016

Journal of Turbomachinery

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“…Uncertainty in the PIV measurements was calculated for a previous study in this facility with the same setup [22], and the uncertainty in the through-plane velocity component was found to be 64.8%, and the in-plane uncertainty was a maximum of 68%. These uncertainties were based on a conservative estimate of 60.15 pixel instantaneous displacement uncertainty.…”

Section: Uncertainty Analysismentioning

confidence: 99%

The Effect of Area Ratio Change Via Increased Hole Length for Shaped Film Cooling Holes With Constant Expansion Angles

Haydt

Lynch

Lewis

2018

Journal of Turbomachinery

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Shaped film cooling holes are used as a cooling technology in gas turbines to reduce metal temperatures and improve durability, and they generally consist of a small metering section connected to a diffuser that expands in one or more directions. The area ratio (AR) of these holes is defined as the area at the exit of the diffuser, divided by the area at the metering section. A larger AR increases the diffusion of the coolant momentum, leading to lower average momentum of the coolant jet at the exit of the hole and generally better cooling performance. Cooling holes with larger ARs are also more tolerant of high blowing ratio conditions, and the increased coolant diffusion typically better prevents jet lift-off from occurring. Higher ARs have traditionally been accomplished by increasing the expansion angle of the diffuser while keeping the overall length of the hole constant. The present study maintains the diffuser expansion angles and instead increases the length of the diffuser, which results in longer holes. Various ARs have been examined for two shaped holes: one with forward and lateral expansion angles of 7 deg (7-7-7 hole) and one with forward and lateral expansion angles of 12 deg (12-12-12 hole). Each hole shape was tested at numerous blowing ratios to capture trends across various flow rates. Adiabatic effectiveness measurements indicate that for the baseline 7-7-7 hole, a larger AR provides higher effectiveness, especially at higher blowing ratios. Measurements also indicate that for the 12-12-12 hole, a larger AR performs better at high blowing ratios but the hole experiences ingestion at low blowing ratios. Steady Reynolds-averaged Navier–Stokes simulations did not accurately predict the levels of adiabatic effectiveness, but did predict the trend of improving effectiveness with increasing AR for both hole shapes. Flowfield measurements with particle image velocimetry (PIV) were also performed at one downstream plane for a low and high AR case, and the results indicate an expected decrease in jet velocity due to a larger diffuser.

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Time-Resolved Analysis of Film Cooling Effects Under Pulsating Inflow Conditions

Heinrich

Herbig

Peitsch

2021

Notes on Numerical Fluid Mechanics and Multidisciplinary Design

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Effect of High Freestream Turbulence on Flowfields of Shaped Film Cooling Holes

Cited by 58 publications

References 19 publications

Thermal Field Measurements for a Shaped Hole at Low and High Freestream Turbulence Intensity

Thermal Field Measurements for a Shaped Hole at Low and High Freestream Turbulence Intensity

The Effect of Area Ratio Change Via Increased Hole Length for Shaped Film Cooling Holes With Constant Expansion Angles

Time-Resolved Analysis of Film Cooling Effects Under Pulsating Inflow Conditions

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