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In order to analyze the blade vibration caused by flutter, it is necessary to understand both the aerodynamic damping and structural damping of the high vibration stress. Flutter Vibration mode occurring in the rated speed is non-synchronous mode. To measure non-synchronous mode damping, high frequency excitation magnet was developed. Damping characteristics of the non-synchronous mode of nodal diameter 12 and 4 were measured in the rotation test. For comparison, synchronous mode of nodal diameter 4 was measured. From these results, it was concluded as follows. (1) It is possible to excite non-synchronous mode by high frequency excitation magnet and measure the damping ratio. (2) According to the measurement results of non-synchronous mode of nodal diameter 12 and 4, damping ratio is increased if the excitation force become large. Synchronous mode of nodal diameter 4 is also a similar trend. (3) Nodal diameter 4 damping ratio of non-synchronous mode(Resonance speed:100%) was lower than synchronous mode(Resonance speed:75%). (4) When evaluating flutter which occurs at rated speed, it is necessary to measure structural damping ratio at rated speed. 1. 緒 言 近年,蒸気タービン,ガスタービンの後段翼は効率向上のため長翼化される傾向にあり,翼固有振動数の低下 に伴って,フラッタ現象が発生しやすい傾向となっている.フラッタ現象は,流体・構造の連成によって発生す る自励振動の一種であり,流体が翼に及ぼす空力仕事が,翼-ディスク系の構造減衰によるエネルギー散逸を上 回った時に不安定現象となって発生する.発生周波数は翼-ディスク系の固有振動数であり,ロータ回転数とは 同期しない非同期振動である.フラッタが発生すると,振動応力は高応力まで成長し,翼の破損に至る可能性が ある.フラッタによる翼振動が高応力まで成長することを評価するためには,高振幅・高応力場における空力仕 事,及び構造減衰を同時に把握する必要がある.フラッタに関しては多くの研究がなされており,翼列風洞試験 による空力減衰の実測(花村,山口,1986),非定常空気力の実測値と CFD の比較(鈴木他,2009)があり,流体が 翼に及ぼす空力仕事の研究より,流体の翼への流入角や隣接翼間の振動位相差などに空力仕事は影響され,概ね

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Development of excitation test method for non-synchronous vibration of rotating turbine blade (Measurement of damping of non-synchronous vibration mode)