Effects of Cylindrical-Hole Shape and Fillet on Flow and Temperature Fields in Vane Cascade With Endwall Film-Cooling

Volume 7B: Heat Transfer ◽

10.1115/gt2020-14099 ◽

2020 ◽

Author(s):

B. B. Huyssen ◽

G. I. Mahmood

Keyword(s):

Flow Field ◽

Film Cooling ◽

Total Pressure ◽

Cylindrical Hole ◽

Coolant Flow ◽

Cooling Flow ◽

Aerodynamic Performances ◽

Hole Geometry ◽

Endwall Film Cooling ◽

Geometric Variation

Abstract The aerodynamic performances of the cascade can be improved using the filleted blade profile. The non-uniform distributions of the endwall film-cooling flow from the cylindrical coolant holes have prompted the investigations of cascade flow-field employing several variations of the cylindrical coolant hole geometry. While some variants of the cylindrical hole show potential of improved film-cooling effectiveness on the endwall, the aerodynamic performances of the cascade on the other hand suffer. This paper presents results from the measurements of the flow-field and air temperature along a cascade passage that employs filleted vanes and endwall film-cooling using a diffused shape of the cylindrical coolant holes. The experimental results are also presented in the same vane cascade with the endwall film-cooling using the regular cylindrical coolant holes and without the fillet at the vane endwall junction. The diffused coolant hole is a smooth geometric variation of diffused area of the cylindrical hole and diffuses the coolant flow smoothly along the hole axis. The objectives are to investigate the effects of the fillet and new diffused cylindrical hole on the cascade aerodynamic performances. The effects are illuminated through the interactions of the coolant streams with the mainstream. The measurements are obtained in a linear atmospheric cascade employing a two-dimensional vane profile and an inlet Reynolds number of 2.0E+06. The axis of the coolant holes are oriented at 30° to the endwall at inlet from the coolant plenum. The coolant holes are employed both at upstream and inside of the cascade passage. The fillet extends from the leading edge region to half-way of the vane profile. The time-averaged local velocities, total pressures, and air temperatures are measured at different pitchwise planes in the cascade for the different cases at the endwall. The density ratio of the coolant flow to mainstream is about 1.0 for the flow-field measurements and about 0.94 for the temperature measurements. The overall blowing ratio of the film-cooling flow varies between 1.0 and 2.8. The results of the yaw angle deviations of endwall region flow, total pressure loss coefficients, and non-dimensional temperatures are then presented to provide the effects of the fillet and film-cooling hole geometry. The results show the desirable performances of the local distributions and concentrations of the coolant streams, the low flow turning near endwall, and the reduction of total pressure losses are better when the diffused holes are employed without the presence of fillet. With the fillet and diffused cylindrical holes, the aforementioned aerodynamic performances are improved further compared to those for the regular cylindrical coolant holes.

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Effect of Endwall Film Cooling Upstream of an Airfoil/Endwall Junction to Suppress the Formation of Horseshoe Vortex in a Symmetric Airfoil

Volume 3B: Heat Transfer ◽

10.1115/gt2013-95385 ◽

2013 ◽

Cited By ~ 8

Author(s):

Kenichiro Takeishi ◽

Yutaka Oda ◽

Junichi Seguchi ◽

Shintaro Kozono

Keyword(s):

Film Cooling ◽

Leading Edge ◽

Horseshoe Vortex ◽

Temperature Fields ◽

Film Cooling Effectiveness ◽

Eddy Simulation ◽

Coolant Injection ◽

Image Velocimetry ◽

Endwall Film Cooling ◽

Cooling Air

The effects of film cooling air injection at an endwall on the endwall film cooling and the formation of a horseshoe vortex were investigated experimentally and numerically in the leading edge region of a symmetric vane. The film cooling jet was applied upstream of the airfoil/endwall junction to give counter-momentum to the horseshoe vortex, and the temperature fields and flow fields were investigated using laser-induced fluorescence (LIF) and particle image velocimetry (PIV), respectively, in comparison with a large eddy simulation (LES). A comparison of the film cooling effectiveness values found using LES showed good agreement with those found in wind tunnel tests with pressure-sensitive paint (PSP). It was found that an insufficient injection of film coolant could not suppress the formation of the horseshoe vortex, but reinforced its growth. In addition, the effect of the film coolant injection on the endwall heat transfer was examined. The results suggested that film coolant injection upstream of the leading edge has the potential to simultaneously cool the endwall and suppress the formation of the horseshoe vortex.

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Influence of hole shape on the performance of a turbine vane endwall film-cooling scheme

International Journal of Heat and Fluid Flow ◽

10.1016/j.ijheatfluidflow.2006.05.002 ◽

2007 ◽

Vol 28 (3) ◽

pp. 341-356 ◽

Cited By ~ 12

Author(s):

W. Colban ◽

K. Thole

Keyword(s):

Film Cooling ◽

Hole Shape ◽

Turbine Vane ◽

Endwall Film Cooling

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The Variation of Heat Transfer Coefficient, Adiabatic Effectiveness and Aerodynamic Loss with Film Cooling Hole Shape

Annals of the New York Academy of Sciences ◽

10.1111/j.1749-6632.2001.tb05871.x ◽

2006 ◽

Vol 934 (1) ◽

pp. 361-368 ◽

Cited By ~ 5

Author(s):

J.E. SARGISON ◽

S.M. GUO ◽

M.L.G. OLDFIELD ◽

A.J. RAWLINSON

Keyword(s):

Heat Transfer ◽

Heat Transfer Coefficient ◽

Transfer Coefficient ◽

Film Cooling ◽

Hole Shape ◽

Aerodynamic Loss ◽

Cooling Hole ◽

Adiabatic Effectiveness

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Assessment of a Double Hole Film Cooling Geometry Using S-PIV and PSP

Volume 3B: Heat Transfer ◽

10.1115/gt2013-94614 ◽

2013 ◽

Cited By ~ 7

Author(s):

Lesley M. Wright ◽

Stephen T. McClain ◽

Charles P. Brown ◽

Weston V. Harmon

Keyword(s):

Film Cooling ◽

Density Ratio ◽

Three Dimensional ◽

Field Measurements ◽

Secondary Flows ◽

Cylindrical Hole ◽

Cooling Effectiveness ◽

Film Cooling Effectiveness ◽

Hole Geometry ◽

Compound Angle

A novel, double hole film cooling configuration is investigated as an alternative to traditional cylindrical and fanshaped, laidback holes. This experimental investigation utilizes a Stereo-Particle Image Velocimetry (S-PIV) to quantitatively assess the ability of the proposed, double hole geometry to weaken or mitigate the counter-rotating vortices formed within the jet structure. The three-dimensional flow field measurements are combined with surface film cooling effectiveness measurements obtained using Pressure Sensitive Paint (PSP). The double hole geometry consists of two compound angle holes. The inclination of each hole is θ = 35°, and the compound angle of the holes is β = ± 45° (with the holes angled toward one another). The simple angle cylindrical and shaped holes both have an inclination angle of θ = 35°. The blowing ratio is varied from M = 0.5 to 1.5 for all three film cooling geometries while the density ratio is maintained at DR = 1.0. Time averaged velocity distributions are obtained for both the mainstream and coolant flows at five streamwise planes across the fluid domain (x/d = −4, 0, 1, 5, and 10). These transverse velocity distributions are combined with the detailed film cooling effectiveness distributions on the surface to evaluate the proposed double hole configuration (compared to the traditional hole designs). The fanshaped, laidback geometry effectively reduces the strength of the kidney-shaped vortices within the structure of the jet (over the entire range of blowing ratios considered). The three-dimensional velocity field measurements indicate the secondary flows formed from the double hole geometry strengthen in the plane perpendicular to the mainstream flow. At the exit of the double hole geometry, the streamwise momentum of the jets is reduced (compared to the single, cylindrical hole), and the geometry offers improved film cooling coverage. However, moving downstream in the steamwise direction, the two jets form a single jet, and the counter-rotating vortices are comparable to those formed within the jet from a single, cylindrical hole. These strong secondary flows lift the coolant off the surface, and the film cooling coverage offered by the double hole geometry is reduced.

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The Design of an Improved Endwall Film-Cooling Configuration

Volume 4: Heat Transfer; Electric Power; Industrial and Cogeneration ◽

10.1115/98-gt-483 ◽

1998 ◽

Cited By ~ 11

Author(s):

S. Friedrichs ◽

H. P. Hodson ◽

W. N. Dawes

Keyword(s):

Secondary Flow ◽

Film Cooling ◽

Large Scale ◽

Three Dimensional ◽

Secondary Flows ◽

Aerodynamic Loss ◽

Cooling Flow ◽

High Static Pressure ◽

Endwall Film Cooling ◽

Aerodynamic Losses

The endwall film-cooling cooling configuration investigated by Friedrichs et al. (1996, 1997) had in principle sufficient cooling flow for the endwall, but in practice, the redistribution of this coolant by secondary flows left large endwall areas uncooled. This paper describes the attempt to improve upon this datum cooling configuration by redistributing the available coolant to provide a better coolant coverage on the endwall surface, whilst keeping the associated aerodynamic losses small. The design of the new, improved cooling configuration was based on the understanding of endwall film-cooling described by Friedrichs et al. (1996, 1997). Computational fluid dynamics were used to predict the basic flow and pressure field without coolant ejection. Using this as a basis, the above described understanding was used to place cooling holes so that they would provide the necessary cooling coverage at minimal aerodynamic penalty. The simple analytical modelling developed in Friedrichs et al. (1997) was then used to check that the coolant consumption and the increase in aerodynamic loss lay within the limits of the design goal. The improved cooling configuration was tested experimentally in a large scale, low speed linear cascade. An analysis of the results shows that the redesign of the cooling configuration has been successful in achieving an improved coolant coverage with lower aerodynamic losses, whilst using the same amount of coolant as in the datum cooling configuration. The improved cooling configuration has reconfirmed conclusions from Friedrichs et al. (1996, 1997); firstly, coolant ejection downstream of the three-dimensional separation lines on the endwall does not change the secondary flow structures; secondly, placement of holes in regions of high static pressure helps reduce the aerodynamic penalties of platform coolant ejection; finally, taking account of secondary flow can improve the design of endwall film-cooling configurations.

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Effects of Film Hole Shape and Turbulence Intensity on the Thermal Field Downstream of Single Row Film Holes

Volume 7B: Heat Transfer ◽

10.1115/gt2020-16113 ◽

2020 ◽

Author(s):

Zheng Zhang ◽

Hui-ren Zhu ◽

Wei-jiang Xu ◽

Cun-liang Liu ◽

Zhuang Wu

Keyword(s):

Secondary Flow ◽

Inclination Angle ◽

Water Drop ◽

Lateral Diffusion ◽

Cylindrical Hole ◽

Normal Velocity ◽

Hole Shape ◽

Blowing Ratio ◽

Nylon Mesh ◽

Shaped Hole

Abstract A nylon mesh coated with broadband thermochromic liquid crystal was set in different planes perpendicular to the mainstream direction at various locations downstream of the film hole. By the temperature visualization technique, the colorful non-dimensional temperature images on the nylon mesh of cylindrical hole, water-drop hole and dustpan shaped hole at different blowing ratios and turbulence at angle of 30° and 60° were visualized. The visualization experiment visually studied the effects of hole shape, hole inclination angle, blowing ratio and mainstream turbulence on the distribution of the film. The results show that stream-wise diffusion of water-drop hole reduces kidney vortex intensity, making higher attachment of the film of water-drop than that of cylindrical hole, consequently the lateral coverage range of water-drop hole film is wider than that of cylindrical hole film. The lateral diffusion of dustpan shaped hole further reduces the kidney vortex intensity. This obviously increases the film coverage and strengthens the adhesion of film of dustpan shaped hole. Increasing the inclination angle of the hole and the blowing ratio will increase the normal velocity of the jet and increase the thickness of the film. however, increasing inclination angle and blowing ratio will enhance kidney vortex intensity and decrease the film cooling effectiveness. The high turbulent intensity of mainstream will enhance the lateral diffusion of the film and enhance the mixing of the secondary flow and mainstream, so the continuity and uniformity of film are better. However, the intense mix of secondary flow and mainstream results in the non-dimensional temperature of the film drops sharply and the film coverage reduced accordingly.

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Computational Predictions of Endwall Film Cooling for a Turbine Nozzle Vane With an Asymmetric Contoured Passage

Volume 4: Heat Transfer, Parts A and B ◽

10.1115/gt2008-50878 ◽

2008 ◽

Cited By ~ 5

Author(s):

Yoji Okita ◽

Chiyuki Nakamata

Keyword(s):

Film Cooling ◽

Computational Study ◽

Suction Side ◽

Geometrical Parameters ◽

Passage Vortex ◽

Rear Part ◽

Cooling Hole ◽

Secondary Vortices ◽

Endwall Film Cooling ◽

Film Cooling Holes

This paper presents results of a computational study for the endwall film cooling of an annular nozzle cascade employing a circumferentially asymmetric contoured passage. The investigated geometrical parameters and the flow conditions are set consistent with a generic modern HP-turbine nozzle. Rows of cylindrical film cooling holes on the contoured endwall are arranged with a design practice for the ordinary axisymmetric endwall. The solution domain, which includes the mainflow, cooling hole paths, and the coolant plenum, is discretized in the RANS equations with the realizable k-epsilon model. The calculated flow field shows that the pressure gradients across the passage between the pressure and the suction side are reduced with the asymmetric endwall, and consequently, the rolling up of the inlet boundary layer into the passage vortex is delayed and the separation line has moved further downstream. With the asymmetric endwall, because of the effective suppression of the secondary flow, more uniform film coverage is achieved especially in the rear part of the passage and the laterally averaged effectiveness is also significantly improved in this region. The closer inspection of the calculated thermal field reveals that, with the asymmetric passage, the coolant ejected from the holes are less deflected by the secondary vortices, and it attaches better to the endwall in this rear part.

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