This paper explores the effects of random blade mistuning on the dynamics of an advanced industrial compressor rotor, using a component-mode-based reduced-order model formulation for tuned and mistuned bladed disks. The technique uses modal data obtained from finite element models to create computationally inexpensive models of mistuned bladed disks in a systematic manner. Both free and forced responses of the rotor are considered, and the obtained results are compared with “benchmark” finite element solutions. A brief statistical study is presented, in which Weibull distributions are shown to yield reliable estimates of forced response statistics. Moreover, a simple method is presented for computing natural frequencies of noninteger harmonics, using conventional cyclic symmetry finite element analysis. This procedure enables quantification of frequency veering data relevant to the assessment of mistuning sensitivity (e.g., veering curvatures), and it may provide a tool for quantifying structural interblade coupling in finite element rotor models of arbitrary complexity and size. The mistuned forced response amplitudes and stresses are found to vary considerably with mistuning strength and the degree of structural coupling between the blades. In general, this work demonstrates how reduced order modeling and Weibull estimates of the forced response statistics combine to facilitate thorough investigations of the mistuning sensitivity of industrial turbomachinery rotors.

A reduced-order model formulation is presented for examining the forced response of tuned and mistuned bladed disks. The technique developed uses modal information obtained from highly detailed FEM models to create, in a systematic manner, much simpler and computationally inexpensive models of bladed disks. The small size of the reduced-order model and associated computational savings enable analysts to examine the effect of mistuning strength and pattern, interblade coupling, and localized modes on forced response amplitudes. Previously, this was a formidable task with finite element modeling for even a single mistuning pattern.

The results of an experimental investigation on the effects of random blade mistuning on the forced dynamic response of bladed disks are reported. Two experimental specimens are considered: a nominally periodic twelve-bladed disk with equal blade lengths, and the corresponding mistuned bladed disk, which features slightly different blades of random lengths. Both specimens are subject to traveling-wave excitations delivered by piezo-electric actuators. The primary aim of the experiment is to demonstrate the occurrence of an increase in forced response blade amplitudes due to mistuning, and to verify analytical predictions about the magnitude of these increases. In particular, the impact of localized mode shapes, engine order excitation, and disk structural coupling on the sensitivity of forced response amplitudes to blade mistuning is reported. This work reports one of the first systematic experiments carried out to demonstrate and quantify the effect of mistuning on the forced response of bladed disks.

The results of an experimental investigation of the effects of random blade mistuning on the free dynamic response of bladed disks are reported. Two experimental specimens are considered: a nominally periodic twelve-bladed disk with equal blade lengths, and the corresponding mistuned bladed disk, which features slightly different, random blade lengths. In the experiment, both the spatially extended modes of the tuned system and the localized modes of the mistuned system are identified. Particular emphasis is placed on the transition to localized mode shapes as the modal density in various frequency regions increases. Excellent qualitative and quantitative agreement is obtained between experimental measurements and results obtained by finite element analysis. Experimental results are additionally used to validate a component mode-based, reduced-order modeling technique for bladed disks. This work reports the first systematic experiment carried out to demonstrate the occurrence of vibration localization in bladed disks.

This paper investigates the effects of random blade mistiming on the dynamics of an advanced gas turbine rotor. Both free and forced responses of the rotor are examined using the finite element method, and a computationally inexpensive reduced-order modeling technique based on component mode synthesis. The spatially extended free modes of vibration of the tuned rotor are found to undergo severe localization upon the introduction of blade mistuning. In turn, this results in dramatic displacement and stress amplitude increases in the forced response of individual blades. The mistuned forced response amplitude is found to vary considerably with mistuning strength and the degree of aerodynamic and disk structural coupling between the blades. The paper concludes with a statistical study in which Weibull distributions are used to calculate approximate forced response statistics.predicted by a tuned analysis. 4 ' 5 Mistuning effects must be included in the analysis if accurate predictions of vibratory response amplitudes are to be made. However, analyzing a finite element model of a full blade assembly, such as that shown in Figure 2, is an enormously costly, if not impossible, computational task. The purpose of this paper is to demonstrate, through the case study of an industrial rotor, that mistuned response amplitudes can be accurately and efficiently predicted, hi a statistical fashion, by using a novel reduced-order modeling technique. This technique, recently developed by Ottarsson et a/. 6 and Kruse and Pierre, 7 produces reduced-order models (ROM) of turbomachinery rotors directly from their finite element models. The procedure involves a component mode analysis of the rotor, with a truncated number of modal amplitudes describing the response of the assembly. The key idea introduced by Ottarsson et a/. 6 is that the motion of an individual blade consists of both cantilever blade elastic motion and diskinduced static motion. The principal advantage of the reduced-order modeling technique is the considerable computational savings associated with solving for the dynamic response of an entire mistuned rotor