The literature on reduced-order modeling, simulation, and analysis of the vibration of bladed disks found in gas-turbine engines is reviewed. Applications to system identification and design are also considered. In selectively surveying the literature, an emphasis is placed on key developments in the last decade that have enabled better prediction and understanding of the forced response of mistuned bladed disks, especially with respect to assessing and mitigating the harmful impact of mistuning on blade vibration, stress increases, and attendant high cycle fatigue. Important developments and emerging directions in this research area are highlighted.

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Modeling and Analysis of Mistuned Bladed Disk Vibration: Status and Emerging Directions

Vehicle system dynamics integration encompasses interdisciplinary challenges innovations in various aspects related to vehicle system/subsystems/components dynamic characteristics, modeling and validation, vehicle dynamics state measurement and estimation, vehicle/chassis control systems, coordination of power management and dynamics/stability control, etc [1-4]. These are becoming more critical due to the increasing concern and rapid development in electric and hybrid vehicles, which tend to exhibit different vehicle dynamics/stability and control characteristics when compared to conventional vehicles.

Mechanical systems and signal processing

The task of condition monitoring and fault diagnosis of rolling element bearing is often cumbersome and labour intensive. Various techniques have been proposed for rolling bearing fault detection and diagnosis. The challenge however, is to efficiently and accurately extract features from signals acquired from these elements, particularly in the time–frequency domain. A new time–frequency technique, known as basis pursuit, was recently developed. This paper presents an application of this new basis pursuit method in the extraction of features from signals collected from faulty rolling bearings with inner race and outer race faults. Results obtained using this new technique were compared with discrete wavelet packet analysis (DWPA) and the matching pursuit technique. Basis pursuit represents features with very fine resolution and sparsity in the time–frequency domain thus rendering easier interpretation of the analysed results. The technique also improves the signal to noise ratio so that subsequent fault detection and identification can be conducted with confidence.

Fault diagnosis of rolling element bearings using basis pursuit

The maximum blade forced response amplitudes for mistuned turbomachinery rotors are generally much greater than those of their tuned counterparts However, it is known that the ratio of mistuned to tuned maximum vibration amplitudes, the amplitude magnification, is often largest at a relatively small level of mistuning Increasing the level of mistuning beyond this critical value actually leads to a decrease in the amplitude magnification This suggests that it might be beneficial to introduce some level of mistuning into the nominal design of the system intentionally In this study, the effectiveness of this intentional mistuning strategy is investigated Intentional mistuning is introduced into the rotor design by varying the nominal blade stiffnesses in harmonic and square-wave patterns In addition, the unavoidable, random mistuning of the blades is included in the model as usual The statistics of the forced response are examined for lumped parameter models, as well as for a finite element based reduced-order model of an industrial rotor For the cases considered, it is found that intentional mistuning can greatly reduce a rotor's sensitivity to random mistuning

Using Intentional Mistuning in the Design of Turbomachinery Rotors

A new method for the dynamic analysis of mistuned bladed disks is presented. The method is based on exact calculation of the response of a mistimed system using response levels for the tuned assembly togeher with a modification matrix constructed from the frequency response function (FRF) matrix of the tamed system and a matrix describing the mistuning. The train advantages of the method are its efficiency and accuracy, which allow the use of large finite element models of practical bladed disk assemblies in parametric studies of mistuning effects on vibration amplitudes. A new method of calculating the FRF matrix of the tuned system using a sector model is also developed so as to improve the efficiency of the method even further, making the proposed method a very attractive tool for mistuning steadies. various numerical aspects of the proposed method are addressed and its accuracy and efficiency are demonstrated using representative test cases

A new method for dynamic analysis of mistuned bladed disks based on the exact relationship between tuned and mistuned systems

Fluid film thickness in a compliant foil bearing is greatly influenced by the deflection of the bearing structure. Therefore, in order to properly model performance of a foil bearing, it is mandatory that the deflection of the compliant bearing structure due to the generated hydrodynamic pressure is determined accurately. This article proposes an easy-to-use two-dimensional model, which takes into account detailed geometry of the bump foil-top foil assembly and the interaction between bumps and which can predict the bearing deflection and stresses due to an arbitrary pressure load. The proposed model is first validated using a finite element analysis and the results available in the literature and then used to conduct a parametric study investigating the influence of bump foil geometry, the coefficient of friction between the bearing components, and the type of loading on the structural properties of the bearing. The most important parameters are also identified. The proposed analytical model is completel...

Romuald Rzadkowski

Papers

Structural Properties of Foil Bearings: A Closed-Form Solution Validated with Finite Element Analysis

Analysis of middle bearing failure in rotor jet engine using tip-timing and tip-clearance techniques

A numerical modelling of stator–rotor interaction in a turbine stage with oscillating blades

The General Model of Free Vibrations of Mistuned Bladed Discs, Part I: Theory

Transient Nozzle Excitation of Mistuned Bladed Discs