The film cooling performance of the hybrid scheme over a flat plate was presented in terms of film cooling effectiveness, heat transfer coefficient ratio, Frossling number and NHFR, at low and high blowing ratios. Subsequently, the film cooling performances of the hybrid scheme were compared with other traditional and advanced published film hole geometries. The film cooling performance of the hybrid scheme was investigated for blowing ratios ranging from 0.5 to 1.5 and for a density ratio equal to 0.94. The results showed that the hybrid scheme augmented the centerline and laterally averaged film cooling effectiveness compared to other film holes at different blowing ratios. Also, the film cooling effectiveness was enhanced with the blowing ratio. The centerline and laterally averaged heat transfer coefficient ratio of the hybrid scheme demonstrated an average near unity over the downstream surface and was not significantly influenced by increasing the blowing ratio. The hybrid scheme provided similar results of heat transfer coefficient ratio as circular and fanshaped holes at high blowing ratio. The proposed scheme also produced values of Frossling number lower than those obtained with circular holes and those were unaffected by the blowing ratio. The net heat flux reduction was presented to illustrate the overall film cooling performance by combining the film cooling effectiveness and heat transfer coefficient ratio. The dimensionless reference temperature, theta = 1.5, was used to calculate the NHFR. The hybrid scheme provided a high film cooling effectiveness with heat transfer coefficient ratio near unity. Therefore, it produced the highest NHFR in the streamwise and laterally averaged directions compared to those obtained with circular and fanshaped holes. As a result, the hybrid scheme is able to increase the airfoil's life time. A hybrid scheme could sustain increasing the inlet temperature to the turbine, hence, improving the overall gas turbine efficiency while avoiding the occurrence of hot spots on the downstream surfaces. The current results for the hybrid scheme were based on the film cooling performance. However, the proposed scheme was designed as a second film hole configuration of a multi-stage cooling scheme which includes conjugate heat transfer (CHT) and film cooling. Therefore, further experimental and numerical work, including the conjugate effects as well as film cooling effects, over an airfoil are needed to study the effect of upstream and downstream CHT on film cooling performance.


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    Titel :

    An experimental investigation of a new hybrid film cooling scheme


    Weitere Titelangaben:

    Experimentelle Untersuchung eines neuen hybriden Filmkühlungsschemas


    Beteiligte:
    Ghorab, M.G. (Autor:in) / Hassan, I.G. (Autor:in)

    Erschienen in:

    Erscheinungsdatum :

    2010


    Format / Umfang :

    14 Seiten, 13 Bilder, 26 Quellen




    Medientyp :

    Aufsatz (Zeitschrift)


    Format :

    Print


    Sprache :

    Englisch