A Review of Shaped Hole Turbine Film-Cooling Technology

Bunker, Ronald S.

doi:10.1115/1.1860562

Cited by 712 publications

(193 citation statements)

References 40 publications

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“…11 in Paper I). Injecting coolant through this row in the presence of showerhead cooling will disturb the state of a fresh boundary layer development with high kinetic energy content due to the showerhead and consequently it will enhance the HTC to a greater extent, which is consistent with the explanation given by Bunker [61]. In this case, both cooling hole types react in the same way to the state of approaching flow.…”

Section: Illustrated Insupporting

confidence: 78%

“…Note that injection through a showerhead will make a thicker boundary layer while at the same time it will enhance the HTC. This figure thus suggests that fan-shaped holes may reduce the kinetic energy within a thick and well-developed turbulent boundary layer and hence reduce the HTC, see Bunker [61], while cylindrical holes will elevate the turbulence level further and enhance the HTC under the same circumstance. Figure 15 indicates that general findings concerning row #1, such as a higher level of HTC for fan-shaped holes compared to cylindrical holes and also elevated HTC when M is increased, can be extended to row #3.…”

Section: Illustrated Inmentioning

confidence: 99%

“…In "A review of shaped hole turbine film-cooling technology", Bunker [61] reviewed some of the relevant parameters that affect AFE of the shaped holes.…”

Section: Influencing Parametersmentioning

confidence: 99%

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On Film Cooling of Turbine Guide Vanes : From Experiments and CFD-Simulations to Correlation Development

Najafabadi¹

2015

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To achieve high thermal efficiency in modern gas turbines, the turbine-inlet temperature has to be increased. In response to such requisites and to prevent thermal failure of the components exposed to hot gas streams, the use of different cooling techniques, including film cooling, is essential. Finding an optimum film cooling design has become a challenge as it is influenced by a large number of flow and geometrical parameters. This study is dedicated to some important aspects of film cooling of a turbine guide vane and consists of three parts. The first part is associated with an experimental investigation of the suction and pressure side cooling by means of a transient IR-Thermography technique under engine representative conditions. It is shown that the overall film cooling performance of the suction side can be improved by adding showerhead cooling if fan-shaped holes are used, while cylindrical holes may not necessarily benefit from a showerhead. According to the findings, investigation of an optimum cooling design for the suction side is not only a function of hole shape, blowing ratio, state of approaching flow, etc., but is also highly dependent on the presence/absence of showerhead cooling as well as the number of cooling rows. In this regard, it is also discussed that the combined effect of the adiabatic film effectiveness (AFE) and the heat transfer coefficient (HTC) should be considered in such study. As for the pressure side cooling, it is found that either the showerhead or a single row of cylindrical cooling holes can enhance the HTC substantially, whereas a combination of the two or using fan-shaped holes indicates considerably lower HTC. An important conclusion is that adding more than one cooling row will not augment the HTC and will even decrease it under certain circumstances. In the second part, computational fluid dynamics (CFD) investigations have shown that film cooling holes subjected to higher flow acceleration will maintain a higher level of AFE. Although this was found to be valid for both suction and pressure side, due to an overall lower acceleration for the pressure side, a lower AFE was achieved. Moreover, the CFD results indicate that fan-shaped holes with low area ratio (dictated by design constraints for medium-size gas turbines), suffer from cooling jet separation and hence reduction in AFE for blowing ratios above unity. Verification of these conclusions by experiments suggests that CFD can be used more extensively, e.g. for parametric studies. The last part deals with method development for deriving correlations based on experimental data to support engineers in the design stage. The proposed method and the ultimate correlation model could successfully correlate the laterally averaged AFE to the downstream distance, the blowing ratio and the local pressure coefficient representing the effect of approaching flow. The applicability of the method has been examined and the high level of predictability of the final model demonstrates its suitability to be used for design purposes...

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Section: Illustrated Insupporting

confidence: 78%

Section: Illustrated Inmentioning

confidence: 99%

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On Film Cooling of Turbine Guide Vanes : From Experiments and CFD-Simulations to Correlation Development

Najafabadi¹

2015

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“…Bunker [2] in his comprehensive review paper on film cooling from shaped holes has pointed out that no single shaping of film hole stands as an optimal geometry for all applications. He also concluded that hole shape maintains the cooling jets closer to surface, enhances film coverage and reduces mixing.…”

Section: Introductionmentioning

confidence: 99%

Effect of Hole Shapes, Orientation And Hole Arrangements On Film Cooling Effectiveness

Jindal¹,

Roy²,

Sharma³

2016

International Journal of Aeronautical and Space Sciences

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In this present work, the effect of hole shapes, orientation and hole arrangements on film cooling effectiveness has been carried out. For this work a flat plate has been considered for the computational model. Computational analysis of film cooling effectiveness using different hole shapes with no streamwise inclination has been carried out. Initially, the model with an inclination of 30° has been verified with the experimental data. The validation results are well in agreement with the results taken from literature. Five different hole shapes viz. Cylindrical, Elliptic, Triangular, Semi-Cylindrical and Semi-Elliptic have been compared and validated over a wide range of blowing ratios. The blowing ratios ranged from 0.67 to 1.67. Later, orientation of holes have also been varied along with the number of rows and hole arrangements in rows. The performance of film cooling scheme has been given in terms of centerline and laterally averaged adiabatic effectiveness. Semi-elliptic hole utilizes half of the mass flow as in other hole shapes and gives nominal values of effectiveness. The triangular hole geometry shows higher values of effectiveness than other hole geometries. But when compared on the basis of effectiveness and coolant mass consumption, Semi-elliptic hole came out to give best results.

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“…From measurements on a range of the L/D ratio of 1.75 to 18, Lutum and Johnson [5] reported that film-cooling effectiveness generally decreased with decreasing L/D when the ratio was less than 5.0 but showed no significant change for L/D that exceeded 5.0. Bunker [6] examined the origins of the shaped film-cooling hole and summarized the extensive literature regarding the performance of such film holes. In order to evaluate the performance and characteristics of various holeshapes, many numerical studies have been conducted, e.g., Bohn and Moritz [7], Hyams and Leylek [8], Azzi and Jubran [9], Leedom and Acharya [10] and Mahmood et al [11].…”

Section: Introductionmentioning

confidence: 99%

Multi-objective Optimization of a Laidback Fan Shaped Film-Cooling Hole Using Evolutionary Algorithm

Lee

Husain

Kim

2010

International Journal of Fluid Machinery and Systems

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Laidback fan shaped film-cooling hole is formulated numerically and optimized with the help of three-dimensional numerical analysis, surrogate methods, and the multi-objective evolutionary algorithm. As Pareto optimal front produces a set of optimal solutions, the trends of objective functions with design variables are predicted by hybrid multi-objective evolutionary algorithm. The problem is defined by four geometric design variables, the injection angle of the hole, the lateral expansion angle of the diffuser, the forward expansion angle of the hole, and the ratio of the length to the diameter of the hole, to maximize the film-cooling effectiveness compromising with the aerodynamic loss. The objective function values are numerically evaluated through Reynolds-averaged Navier-Stokes analysis at the designs that are selected through the Latin hypercube sampling method. Using these numerical simulation results, the Response Surface Approximation model are constructed for each objective function and a hybrid multi-objective evolutionary algorithm is applied to obtain the Pareto optimal front. The clustered points from Pareto optimal front were evaluated by flow analysis. These designs give enhanced objective function values in comparison with the experimental designs.

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A Review of Shaped Hole Turbine Film-Cooling Technology

Cited by 712 publications

References 40 publications

On Film Cooling of Turbine Guide Vanes : From Experiments and CFD-Simulations to Correlation Development

On Film Cooling of Turbine Guide Vanes : From Experiments and CFD-Simulations to Correlation Development

Effect of Hole Shapes, Orientation And Hole Arrangements On Film Cooling Effectiveness

Multi-objective Optimization of a Laidback Fan Shaped Film-Cooling Hole Using Evolutionary Algorithm

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