The objective of this paper is to critically review the cooling design for the MS6001 first stage buckets and examine alternate designs for improved cooling. Several basic designs were considered to improve cooling performance, extend service life, and improve the reliability of the first stage bucket. Of the designs being considered and compared with existing and past designs, two options containing 13 and 13M (modified) cooling holes were investigated. The target for the design which was met by the 13M design, was to reduce bucket bulk metal temperature by an average of 13.9°C (25°F), while maintaining current unit performance and bucket integrity. Finite element analysis was performed to evaluate the aerofoil thermal gradients and the results demonstrate that a cooler core and an overall reduction in bulk metal temperature was obtained with the modified designs. In addition to the design analysis, bucket alloys were reviewed and IN-738 was chosen for its reliability and predictable performance.

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