The fabrication of primary surface recuperators for gas turbines and microturbines is a complex process involving a multitude of variables, which are highly interactive. After over 25 years of improvements to recuperator manufacture at Solar Turbines Incorporated, fabrication of the recuperator primary sheet is still prone to scatter of output measures within drawing requirements caused by variations in raw foil properties and changes in environmental conditions. This paper outlines a systematic analysis and improvement of the primary sheet fin folding process using Taguchi methodology. The approach was to break the overall system into subsystems, analyze each subsystem using computer simulation for fin folding and then to analyze the complete system in actual use. The goal was to improve the fabrication process so that multiple drawing requirements for primary recuperator sheet are consistently met with minimum variation and the time needed for subsequent manufacturing steps is reduced. An improved system is more robust, meaning total variability in the primary sheet is minimized and outputs are more insensitive to noise (inputs that are not controllable or are very expensive to control). Improvement is measured by calculating the ratio of desired output to undesired output (noise), i.e. the signal to noise (S/N) ratio. More consistent primary sheet will improve overall recuperator system performance and reduce the cost of this critical gas turbine system component. A secondary objective was to increase the durability of the fin-folding blades, which are subject to wear and breakage. As this paper goes to press, analysis of the final design of experiment on the actual system is in progress.

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