Model identification and order response prediction for bladed wheels

A method is proposed in this paper for model identification and order response prediction for bladed wheels. This method makes use of measured blade tip-to-blade tip frequency response functions of a mistuned wheel and assumes responses of the wheel subject to order excitations to be a weighted sum of a number, which is equal to the number of the blades, of modes of the corresponding tuned wheel. The model for the mistuned wheel is identified in terms of the scale-reduced mass and stiffness matrices from which an expression for order responses is derived. The method is validated by comparing order responses calculated using this method with those from the original equation for two wheel models, a lumped parameter model and a finite element paddle wheel model. It can be concluded that, using this method, resonance responses of a mistuned wheel to order excitations at and around the natural frequencies of the first family can be accurately predicted, even mistuning is large. From the order responses the strain levels in the blades can be evaluated and the suitability for the wheel to be released for field use can be assessed.