853 ガスタービン圧縮機翼の非定常振動

抄録

A cascade wind tunnel test was conducted to clarify the unsteady blade vibration characteristics near the stall condition. The vibrating stress of a blade and the pressure fluctuation on a blade surface were measured, and the damping ratio of a blade in a flow was measured using operational modal analysis and using sweep excitation. Moreover, the blade vibration caused by unsteady fluid force and the fluid damping ratio was calculated using three-dimensional computational fluid dynamics analysis and three-dimensional structural finite element analysis. As a result of the experiment, the natural frequency component excited by random fluid force was dominant in blade vibration, and discrete low frequency component appeared in pressure fluctuation. As a result of computation, we reproduced that a discrete low frequency component appeared in fluid force. The experimental result and calculation result of stress amplitude were generally in agreement. The measured damping ratio increased with the increase in a Mach number. The measured damping ratio by an operational modal analysis had smaller variation than that by sweep excitation. The calculated damping ratio was a little higher than an experimental result. As a result of flutter analysis, the damping ratio was positive and the vibration system was stable.