Elevated freestream turbulence effects on heat transfer for a gas turbine vane

Thole, Karen A.; Radomsky, R. W.; Kang, M. B.; Kohli, Atul

doi:10.1016/s0142-727x(01)00145-x

Cited by 29 publications

(10 citation statements)

References 18 publications

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“…Moreover, of particular interest to the gas turbine applications is the stagnation point flow and heat transfer with turbulence present in a transonic free-stream, but experimentally this has proven very challenging and few measurements are available. Difficulties also arise when the correlations developed using simplified geometry are to fit the heat transfer data in a turbine blade leading edge region (Yeh et al, 1993;Thole et al, 2002). On one hand.…”

Section: Experimental Studiesmentioning

confidence: 99%

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Zhang¹,

Lele²

2004

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Public reporting burden for this collection of information is estinuted to awrage 1 hour per response, including the time for reviewing in maintaining the data needed, and completing and reviewing tWs ooHedion of infbrmatian. SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTKppi'oved fcv PMV.1 1 c rclsnsa, distribution unlikiiLoLl SUPPLEMENTARY NOTES 03914. ABSTRACT Stagnation point flow and heat transfer in the presence of free-stream turbulence is investigated through both numerical simulation and theoretical analysis. Large eddy simulations (LES) results for different free-stream turbulent intensity, length scale, and Mach number are reported. The Reynolds stress statistics and budgets are obtained and presented. The numerical results show good agreement with experimental measurements on elevated heat transfer coefficient, and reveals the characteristic vortical flow structures responsible for the observed heat transfer enhancement.The theoretical analysis shows that the vorticity amplification, and hence the heat transfer enhancement, increases with decreasing length scale and reaches a maximum value at about five times the boundary layer thickness. A new correlation for heat transfer enhancement which incorporates turbulence intensity, integral length scale and mean flow Reynolds number is derived and shown to reasonably collapse the recent experimental data. Abstract Stagnation point flow and heat transfer in the presence of free-stream turbulence is investigated through both numerical simulation and theoretical analysis. Large eddy simulations (LES), using fourth order finite difference in curvilinear coordinates and an efficient dual time linearized sub-iteration scheme, are performed to investigate free-stream turbulence impingement upon an elliptical leading edge and the resulting heat transfer enhancement. A new blending procedure is developed through which independent, statistically identical realizations of homogeneous isotropic turbulence are combined to provide realistic representations of free-stream turbulence.Results for diflTerent free-stream turbulent intensity, length scale, and Mach number are reported. Strong anisotropy of the turbulence due to the mean flow strain is observed as the stagnation point is approached. The Reynolds stress statistics and budgets are obtained and presented. These results are expected to provide unique data for turbulence modelling of strain dominated flows. The numerical results show good agreement with the experimental measurements on elevated heat transfer coefficient. It also reveals that small scale, intense vortical flow structures generated at the leading edge by vortex stretching induces significant changes in local thermal boundary layer, causing the observed heat transfer enhancement.In the theoretical study, the distortion of three dimensional unsteady disturbance in an incompressible Hiemenz boundary layer and its effect on the wall heat transfer is analyzed based on linear vortex dynamics. An asymptotic solution for disturbanc...

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Section: Experimental Studiesmentioning

confidence: 99%

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Zhang¹,

Lele²

2004

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“…Mayhew et al [2] expected that real gas-turbine engines were frequently operated under Tu at about 10%-20%. The effects of Tu on the film cooling performance and heat transfer coefficient of turbine airfoils, cylindrical leading edge and flat plate models have been experimentally and numerically investigated by previous researches [3][4][5][6][7][8]. To prolong and give good service to the turbine airfoils, TBC has been widely utilized in gas turbine designs as a thermal insulator between hot mainstream and metal surfaces.…”

Section: Introductionmentioning

confidence: 99%

Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane

Prapamonthon

Yang

et al. 2017

Energies

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This work presents a numerical investigation of the combined effects of thermal barrier coating (TBC) with mainstream turbulence intensity (Tu) on a modified vane of the real film-cooled nozzle guide vane (NGV) reported by Timko (NASA CR-168289). Using a 3D conjugate heat transfer (CHT) analysis, the NGVs with and without TBC are simulated at three Tus (Tu = 3.3%, 10% and 20%). The overall cooling effectiveness, TBC effectiveness and heat transfer coefficient are analyzed and discussed. The results indicate the following three interesting phenomena: (1) TBC on the pressure side (PS) is more effective than that on the suction side (SS) due to a fewer number of film holes on the SS; (2) for all three Tus, the variation trends of the overall cooling effectiveness are similar, and TBC plays the positive and negative roles in heat flux at the same time, and significantly increases the overall cooling effectiveness in regions cooled ineffectively by cooling air; (3) when Tu increases, the TBC effect is more significant, for example, at the highest Tu (Tu = 20%) the overall cooling effectiveness can increase as much as 24% in the film cooling ineffective regions, but near the trailing edge (TE) and the exits and downstream of film holes on the SS, this phenomenon is slight.

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“…Their computational results showed a decrease in boundary layer thickness as distance from the stagnation point increased. Thole et al [20] investigated the effects of freestream turbulence on a gas turbine vane. The authors discovered that the peak level of velocity fluctuations was toward the suction side of the vane and not at the stagnation point.…”

Section: Previous Studiesmentioning

confidence: 99%

Heat Transfer Measurements of Oblong Pins

Kirsch

Thole

2015

Journal of Turbomachinery

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Pin fin arrays are employed as an effective means for heat transfer enhancement in the internal passages of a gas turbine blade, specifically in the blade's trailing edge. Various shapes of the pin itself have been used in such arrays. In this study, oblong pin fins are investigated whereby their long axis is perpendicular to the flow direction. Heat transfer measurements were taken at the pin midspan with unheated endwalls to isolate the pin heat transfer. Results show important differences in the heat transfer patterns between a pin in the first row and a pin in the third row. In the third row, wider spanwise spacing allows for two peaks in heat transfer over the pin surface. Additionally, closer streamwise spacing leads to consistently higher heat transfer for the same spanwise spacing. Due to the blunt orientation of the pins, the peak in heat transfer occurs off the stagnation point.

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Elevated freestream turbulence effects on heat transfer for a gas turbine vane

Cited by 29 publications

References 18 publications

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Stagnation Point Flow and Heat Transfer Under Free-Stream Turbulence

Numerical Study of the Effects of Thermal Barrier Coating and Turbulence Intensity on Cooling Performances of a Nozzle Guide Vane

Heat Transfer Measurements of Oblong Pins

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