The coupled vibration in a shaft‐disk‐blades system

Abstract

The coupling vibrations among support‐longitudinal, shaft‐torsion and blade‐bending vibrations in a shaft‐disk‐blades unit are investigated. The equations of the shaft‐disk‐blades unit are derived from the energy approach in conjunction with the assumed modes method. The present research focuses on the influence of blade number, longitudinal flexibility (K_a ) and stagger angle (β) on coupling behavior. Free vibration is then studied and the results indicate that there exist two types, longitudinal‐shaft‐blade (LSB) and blade‐blade (BB) coupling modes. Nevertheless, the LSB modes shift to SB (shaft‐blade) modes at β=0° and to LB (longitudinal‐blade) modes at β=90°. In between, the LSB mode is observed to evolve from the original SB mode in a previously studied no longitudinal case. Increasing the number of blades results in the increase or decrease of frequencies depending on which interval the frequencies lying in a frequencies axis divided by all the components frequencies fall into. This phenomenon exists as well in changing stagger angle. As to rotation effects, the frequency loci expelling or veering depends on Ka, but the critical speed is irrelevant to β.

Key words:

• shaft‐disk‐blades
• longitudinal mode
• coupling vibration
• stagger angle

Notes

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