Abstract

Although modern turbomachinery design relies on the tuned blades assumption, mistuning (blade-to-blade variations within each blade row) is known to affect significantly the aeroelastic performance. The structural (frequency) mistuning has been studied extensively in the past, while the aerodynamic mistuning starts to attract more attention recently. The question of the present interest is: if/how may the structural and the aerodynamic mistuning interact? The present work uses the fully-coupled fluid-structure simulation method to analyse and elucidate the physical vibration mechanisms of the concurrent structural-aerodynamic mistuned cascade. Three variation patterns, namely alternating, sinusoidal, and random, are used to ensure the generality of the observations. Both the self-excited (flutter) and the forced response vibrations of the mistuned cascade are investigated. The results show that the aerodynamic mistuning has considerable effects on the blade aeroelasticity. More remarkably, it is revealed for the first time that the intentional phasing between the structural and the aerodynamic mistuning may result in significantly different aeroelastic performances. This distinctive behaviour is consistently observed for all studied mistuning patterns of both the flutter and the forced response vibrations. Consequently, the structural-aerodynamic mistuning phasing may be potentially exploited as an extra design variable to leverage the blade aeroelastic performance. In addition, whilst the interaction between the structural and the aerodynamic mistuning exhibits some nonlinearities, a further comparative study also demonstrates that a simple linear superposition can still provide qualitatively consistent results in capturing the trend of mistuned vibratory amplitudes at all possible phase angles. Thus, a simple postprocessing by superimposing two separate aerodynamic and structural mistuned solutions can be very effectively utilized as a starting point for determining the optimum phasing.

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