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Film Cooling Performance of Multiple Arrays of Cylindrical and Fan-Shaped Holes
Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology.
Linköping University, Department of Management and Engineering, Applied Thermodynamics and Fluid Mechanics. Linköping University, The Institute of Technology. Linköping University, Center for Medical Image Science and Visualization (CMIV).ORCID iD: 0000-0001-5526-2399
Siemens Industrial Turbomachinery AB, Sweden.
Siemens Industrial Turbomachinery AB, Sweden.
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2015 (English)In: Journal of Propulsion and Power, ISSN 0748-4658, E-ISSN 1533-3876, Vol. 31, no 6, 1621-1630 p.Article in journal (Refereed) Published
Abstract [en]

Experimental investigations are performed on the suction side of a cooled turbineguide vane. Transient IR thermography is used to evaluate film cooling performanceof cylindrical and fan-shaped holes in a test facility representing engine conditions.Adiabatic film effectiveness (AFE) and net heat flux reduction (NHFR) results due tocoolant injection through double and multiple rows in the presence and absence of anupstream showerhead are presented. Two double staggered rows at different positionshave been cross-compared; one at a relatively high convex curvature region and theother close to the maximum throat velocity. A combination of the two double rowsis considered to be multiple rows. The tested blowing ratios are in the interval of[0.6 – 1.2] and [0.3 – 1.2] for double and multiple rows, respectively. The showerheadcooling is maintained at nominal blowing ratio. The findings suggest that the choice ofbest cooling hole shape for film cooling design can be highly influenced by the numberof cooling rows to be used and also the presence (or absence) of showerhead cooling.It is worth noting that the outcome may differ depending on the quantity of interest, i.e. AFE or NHFR.

Place, publisher, year, edition, pages
American Institute of Aeronautics and Astronautics, 2015. Vol. 31, no 6, 1621-1630 p.
Keyword [en]
Film Cooling, Gas Turbine, Film Effectiveness, Net Heat Flux Reduction, Cylindrical Holes, Fan-shaped Holes
National Category
Fluid Mechanics and Acoustics
Identifiers
URN: urn:nbn:se:liu:diva-117030DOI: 10.2514/1.B35618ISI: 000368248000011OAI: oai:DiVA.org:liu-117030DiVA: diva2:802171
Projects
Turbo Power Program
Note

Funding agencies: Swedish Energy Agency; Siemens Industrial Turbomachinery, AB; GKN Aerospace Sweden, AB; Royal Institute of Technology through the Swedish research program TURBO POWER

Vid tiden för disputationen förelåg publikationen endast som manuskript

Available from: 2015-04-11 Created: 2015-04-11 Last updated: 2017-12-04Bibliographically approved
In thesis
1. On Film Cooling of Turbine Guide Vanes: From Experiments and CFD-Simulations to Correlation Development
Open this publication in new window or tab >>On Film Cooling of Turbine Guide Vanes: From Experiments and CFD-Simulations to Correlation Development
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

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 in the future.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2015. 68 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1643
Keyword
Film Cooling, Gas Turbine, Correlation, CFD, Cylindrical holes, Fan-shaped Holes
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:liu:diva-117029 (URN)10.3384/diss.diva-117029 (DOI)978-91-7519-125-6 (ISBN)
Public defence
2015-06-05, ACAS, A huset, Campus Valla, Linkoping, 10:15 (English)
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Supervisors
Projects
Turbo Power Program
Available from: 2015-04-16 Created: 2015-04-11 Last updated: 2016-03-14Bibliographically approved

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Nadali Najafabadi, HosseinKarlsson, Matts

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