ARTICLE:

• INFLUENCE OF HOLE IMPERFECTION ON ADIABATIC FILM COOLING EFFECTIVENESS  download article

M. B. Jovanovic
Technische Universiteit Eindhoven, Eindhoven, The Netherlands

H. C. de Lange
Technische Universiteit Eindhoven, Eindhoven, The Netherlands

Anton A. van Steenhoven
Department of Biomedical Engineering, Eindhoven University of Technology, PO Box 513, Eindhoven, The Netherlands

ABSTRACT

Film cooling, created by the jet cross-flow interaction, is studied experimentally. The influence of a discrete hole imperfection inside the film cooling hole on the adiabatic effectiveness is examined. The discrete imperfection, which originates from the production process, is simulated with a regular geometric body. The effect of the imperfection shape, asymmetry and size on the film cooling effectiveness is measured by means of thermochromic liquid crystals. Besides different imperfections, the velocity ratio is varied. Data are presented as two-dimensional contour plots and qualitatively analysed. For a quantitative analysis integral values are calculated. It is found that the influence of the imperfection, placed 1.2 diameter inside the hole, depends on the velocity ratio and geometry of the imperfection. Imperfections which form a large blockage decrease the effectiveness strongly at low velocity ratios but its influence decreases by increasing the velocity ratio. The cross-sectional shape does not have a strong influence on film cooling if the blockage is constant. The symmetrical imperfection decreases the film cooling effectiveness but an asymmetrical imperfection can even increase the effectiveness in comparison with the perfect hole. When the velocity ratio exceeds 0.50, the best cooling is achieved with the asymmetrical imperfection, which crescent is located windward.

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