亜音速失速領域近傍におけるガスタービン圧縮機翼の非定常振動

概要

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A cascade wind tunnel test was conducted to evaluate an unsteady blade vibration at near stall condition quantitatively. Blade vibration stress and pressure fluctuation on the blade were measured, and damping ratio of the blade vibration in a flow was measured using the sweep excitation method and operational modal analysis. Moreover, flow excited blade vibration and aerodynamic damping ratio were calculated using three-dimensional computational fluid dynamics and three-dimensional structural finite element method. The experiments showed that discrete low frequency components are dominant in a pressure fluctuation, and a natural frequency component excited by a random fluid force is dominant in the blade vibration. The calculations showed those phenomena occur in the calculation results. The calculation error of pressure amplitude was 18%, and the calculated stress amplitudes were from half to twice of measured. On the other hand, the experiments showed that the damping ratio increases as the Mach number increases, and the damping ratio measured using operational modal analysis is equivalent to that using sweep excitation. The calculated damping ratios were about 1.7 times larger than the measured. The flutter calculations showed that the damping ratio of a bending vibration mode is positive and the vibration system is stable.
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