Dynamic characteristics of the multi-packet blade system excited by nozzle wake considering effect of blade rotation with complex operating conditions

Multi-packets whole bladed disks due to excellent functions are used in some turbo-machineries. The dynamic characteristics are more complicated of multi-packets bladed disk compared with general bladed disk systems without bladed packets. The aim of this paper is to investigate the dynamic behaviors of multi-packets system excited by nozzle wake excitation due to partial admission. In order to improve efficiency, an improved three-dimensional finite element model considering effect of blade rotation is developed based on the improved component mode synthesis and cyclic symmetrical properties of the multi-packets bladed disk. The developed method is validated by the whole model of the bladed disk. Influences of partial admission on the vibration characteristics excited by nozzle wake excitation are investigated. It is found that the maximum dynamic response due to partial admission increased by 21.62% compared with full admission. In order to investigate the beating phenomenon in the arc of non-admission, an experiment is applied to study the free damping vibration of bladed packet. The experimental results show that each mode of the free blade obtains split in several sub modes forming frequency clusters when the blades is connected through spring into a bladed packet. The linear superposition of free damping vibration of sub mode frequencies forms a beating vibration in the arc of non-admission.