Assessment of Various Film Cooling Configurations Including Shaped and Compound Angle Holes Based on Large Scale Experiments

Dittmar, J.; Schulz, A.; Wittig, S.

doi:10.1115/gt2002-30176

Cited by 41 publications

(36 citation statements)

References 14 publications

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“…14, which is consistent with the findings of Dittmar et al [72]. Since the latter cooling hole type has a wider jet footprint and the area of disturbed boundary layer is increased, a higher level of HTC is experienced by fan-shaped holes and this is more pronounced for the highest blowing ratio.…”

Section: Illustrated Insupporting

confidence: 82%

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: 82%

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

Najafabadi¹

2015

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“…Both holes have a diameter (d) of 8 mm, and the lateral diffusion angle of the fan-shaped hole is 12 degrees, which is the same as reported in [6][7]. Other different diffusion angles, for example in [15], are not investigated in this study. The length and width of the 3-D domain are kept the same as the slot hole case, and the depth of the domain is 4d, as shown in Fig.…”

Section: Numerical Modelmentioning

confidence: 48%

Simulation of Film Cooling Enhancement With Mist Injection

Wang

2005

Volume 3: Turbo Expo 2005, Parts a and B

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Cooling of gas turbine hot section components such as combustor liners, combustor transition pieces, turbine vanes (nozzles) and blades (buckets) is a critical task for improving the life and reliability of hotsection components. Conventional cooling techniques using air-film cooling, impingement jet cooling, and turbulators have significantly contributed to cooling enhancements in the past. However, the increased net benefits that can be continuously harnessed by using these conventional cooling techniques seem to be incremental and are about to approach their limit. Therefore, new cooling techniques are essential for surpassing these current limits. This paper investigates the potential of film cooling enhancement by injecting mist into the coolant. The computational results show that a small amount of injection (2% of the coolant flow rate) can enhance the cooling effectiveness about 30% ~ 50%. The cooling enhancement takes place more strongly in the downstream region, where the single-phase film cooling becomes less powerful. Three different holes are used in this study including a 2-D slot, a round hole, and a fan-shaped diffusion hole. A comprehensive study is performed on the effect of flue gas temperature, blowing angle, blowing ratio, mist injection rate, and droplet size on the cooling effectiveness with 2-D cases. Analysis on droplet history (trajectory and size) is undertaken to interpret the mechanism of droplet dynamics.

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“…Film cooling studies on a flat plate with cylindrical 1330 H. KANANI ET AL. holes have been carried out by Yuen and Martinez-Botas [1], Baldauf et al [2] and Goldstein et al [3]. Dittmar et al [4] as well as Bell et al [5] applied various film cooling configurations in order to study the film cooling effectiveness. Thole et al [6] and Gritsch et al [7] studied film cooling effectiveness for different geometries of hole.…”

Section: Introductionmentioning

confidence: 97%

Numerical simulation of film cooling effectiveness on a flat plate

Kanani

Shams

Ebrahimi

et al. 2008

Numerical Methods in Fluids

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SUMMARYNumerical simulation has been conducted to study film cooling effectiveness on a flat plate. Threedimensional geometry was generated and the effects of blowing ratio and geometrical shape were studied. The simulation results show that cooling hole shape affects film cooling effectiveness significantly. The LDSA hole decreases the momentum of jet flow at the exit area of the hole and avoids lift-off phenomenon. Counter-rotating vortex formed downstream of the hole is weaker for the LDSA hole and secondary flow is not powerful enough to disturb the jet flow structure next to the wall. Also the results show that the LDSA hole has a better lateral coverage due to the diffused shape of the hole and has a higher effectiveness value in a wider region on the wall.

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Assessment of Various Film Cooling Configurations Including Shaped and Compound Angle Holes Based on Large Scale Experiments

Cited by 41 publications

References 14 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

Simulation of Film Cooling Enhancement With Mist Injection

Numerical simulation of film cooling effectiveness on a flat plate

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