蒸気タービン翼の振動 : 第1報, 有限翼群の接線方向屈曲固有振動の共振応答特性

概要

論文の詳細を見る
In designing steam turbine blades and analyzing blade failures, it is not reasonable to consider every possible resonance to be equally harmful, and we must find out which is harmful under giving condition among all possible resonances. In this report, the coefficients of normal mode of tangential flexural vibration of a group of several blades are obtained by the Rayleigh method, and it is proved that resonant response characteristics depend on 1). number of blades per group, 2).'blade pitch'/'pitch of pulsating steam force', viz. D'/D, and 3). normal mode ; and resonant response characteristics are represented quantitatively in the form of dimensionless function named by the author as "timing factor". As the result, it is found that when D'/D is not close to zero or integers, a remarkable "effect of decreasing amplitude by grouping" is produced on the resonance of fixed free type mode, and on the contrary, an "effect of increasing amplitude by grouping" is produced on the resonance of fixed supported type mode ; and also it is found that an analogy is applicable to axial flexural vibration and torsional vibration. Hence, it is found that the failures of short blades which we experienced are attributable to the resonance between nozzle wake and "tangential flexural first order fixed supported type vibration "or" axial flexural first order vibration having many nodes on shroud".
1960-10-25