Probabilistic analysis of turbine blade durability

Abstract

The effect of variability on turbine blade durability was assessed for seven design/operating parameters in three blade designs. The parameters included gas path and cooling convective parameters, metal and coating thermal conductivity and coating thickness. The durability life was modelled as limited by thermo-mechanical low cycle fatigue and creep. A nominal blade design as well as two additional variants were examined using deterministic and probabilistic approaches. External thermal and pressure boundary conditions were generated by three-dimensional CFD calculations. The location of expected failure was the bottom of the trailing edge cooling slot and was the same for all three designs examined. The nominal design had higher life and less variability for the ranges of design parameters examined. For the temperature range studied fatigue was the primary damage mechanism. The variation in cooling air bulk temperature was most important in setting the variation in blade durability life. This life variation was also affected by main gas bulk temperature and heat transfer coefficient, and cooling heat transfer coefficient, but to a lesser extent.