The Effects of Manufacturing Tolerances on Gas Turbine Cooling

This study presents a summary of the effects of manufacturing methods and processing steps upon the resulting thermal boundary conditions for typical highly cooled turbine airfoils. Specific emphasis is placed on the conservatism that must be "designed into" the component for survival due to realistic manufacturing tolerances. Using the features of a typical blade design, the main geometric factors that can influence the blade heat transfer capability through manufacturing variability are enumerated. The tolerances on those geometric factors are provided, and the approximate quantitative impact on thermal boundary conditions is summarized. A simple example of airfoil cooling for a representative wall section is used to tabulate the variations with the resulting changes in the most affected thermal boundary conditions. Each of the main geometric factors is then evaluated in terms of its possible effect on maximum metal temperature. Paretos of the effects of manufacturing factors exhibit which factors are key and where tighter tolerances may help. Monte Carlo analysis results show the probability distributions associated with overall cooling changes tied to the tolerances.