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MECHANICAL SYSTEMS AND SIGNAL PROCESSING, 120, 1 April 2019, Pages 117-132
School of Mechanical Engineering, Pusan National University
Department of Mechanical Engineering, University of Michigan
Turbine engine compressors consist of many stages. Each stage consists of rotating blades and stationary vanes. Interactions between the rotating blades and the stationary vanes create traveling periodic excitations. The structure is also periodic because its construction has the form of spatially repeated units. Tuned bladed disks are spatially repetitive structures, and their geometry is fully described by that of a sector. The dynamic characteristics of a sector determine the dynamic behavior of the entire tuned structure. Hence, modern structural analysis of bladed disks takes advantage of the assumption of cyclic symmetry. In general, however, vanes consist of several packets; each packet having multiple sectors interconnected with a platform and a casting. The vane system is partially periodic but not cyclic symmetric since the packets are not strongly connected with each other. Due to this fact, the methodologies to understand the dynamic responses of cyclically symmetric structures are not applicable to a vane system. Therefore, a new approach to investigate vane responses under traveling wave excitations and the effect of mistuning between the blades of vanes is presented. A mode-based methodology is used to identify the most responding mode under a traveling wave excitation. Also, a reduced order model (ROM) for calculating the effect of a damping mistuning combined with a stiffness mistuning on a vane packet is presented. A novel methodology for statistical analyses to investigate the effect of damping mistuning in a vane is presented also. The developed ROMs are validated by comparing ROM-predicted steady state harmonic responses to full-order analyses in ANSYS. It is observed that the maximum error of the ROM-predicted amplitude is under 1%. Based on the developed ROMs, a simple algebraic equation is derived for predicting amplification factors by introducing the concept of unit damping mistuning. Amplification factors for all engine order excitations are examined to verify the performance of the proposed methodology. The effects of damping mistuning are studied statistically through Monte Carlo simulations.
- Turbine engine
- traveling wave
- symmetric structures