Completed Projects

N&R has investigated the impact of structural mistuning of centrifugal compressors on high cycle fatigue life.  A physics-based approach to accurately capture structural mistuning effects on blade stresses was developed and applied to the design process of two baseline Honeywell impellers – one splittered and the other unsplittered.  A design-of-experiments technique in conjunction with response surface methodology was used to efficiently explore a 4-variable design space consisting of  back plate thickness, backward curvature angle, airfoil thickness, and blade root radius. Blade stress was selected as the optimization criterion as a proxy for high-cycle fatigue life. Probabilistic stresses were calculated using a reduced order finite-element modeling mistuning code (Turbo-REDUCE) in combination with the ANSYS computer-aided design code and the FPI fast probabilistic integration code.  Results for typical mistuning assumptions show that a subset of the total blade set are subjected to peak stresses 60 percent greater than those without structural mistuning. This result is in agreement with experimental tests and leads to the conclusion that an entirely (or nearly so) analytic design/analysis methodology can replace the traditional design practice of requiring a lengthy and expensive experimental test program to accompany the design process. The multi-code solution methodology is generic and can be applied to a broad category of mistuning problems.

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