https://vcel.tamu.edu/Other%20Contents/Publications/Long%20duration%20blade%20loss%20simulations%20including%20thermal%20growths%20for%20dual-rotor%20gas%20turbine%20engine.pdf

Long duration blade loss simulations including thermal growths for dual-rotor gas turbine engine

The rotor–stator rubbing in rotating machinery generated as a consequence of rotor imbalance, shaft misalignment, and casing deformation is a potential threat to the machinery that seriously affects its performance. Timely prediction and correction of the rubbing are essential for the prolonged life of the machinery and its overall performance. A complete understanding of the system behavior during interaction is a great challenge for researchers working in the field of rotor dynamics. Rubbing phenomena involve complex contact nonlinearities and associated thermal effects, which makes the analysis very difficult. Research works in this field are started with the analysis of simple two degree-of-freedom models and now dealing with extensive three-dimensional finite element models. This paper provides a comprehensive review of different numerical models of rotor–stator rubbing with respect to their ability in simulating the actual response characteristics. A detailed description of contact modeling is also presented with the advantages and disadvantages of each model. Different methods for solving the numerical models are briefly explained. In addition, a commentary on different emerging techniques of rub identification is also reported. Finally, some informed recommendations on future directions are made by stating what lacks in the current research activities.

The numerical modeling of rotor–stator rubbing in rotating machinery: a comprehensive review

Les rotors sont excites non seulement par le balourd tournant mais aussi par les differents mouvements de leur support : turbocompresseurs de vehicules, turbomoteurs aeronautiques, pompes a vide portees en sont des exemples industriels. Ainsi la conception de rotors robustes capables de bien fonctionner sous de telles conditions (excitations extremes) est necessaire pour eviter des instabilites, source de defaillance catastrophique. Le present travail a pour objectif de prevoir le comportement dynamique d’un rotor embarque monte sur des paliers rigides ou elastiques hydrodynamiques et soumis a des excitations du support rigide. Les energies cinetiques et de deformation ainsi que le travail virtuel des composants d’un rotor flexible tournant sont calcules. Le modele propose de rotor embarque est base sur les elements finis de poutre de TIMOSHENKO. Il contient les effets relatifs a l’inertie de rotation des sections droites, a l’inertie gyroscopique, a la deformation de cisaillement d’arbre et a la dissymetrie geometrique de l’arbre et/ou du disque rigide et considere six types de mouvements deterministes (rotations et translations) du support. Suivant le type d’analyse utilise pour le palier, les forces de rappel hydrodynamiques agissant sur l’arbre et calculees avec l’equation de REYNOLDS sont lineaires/non lineaires. L’utilisation des equations de LAGRANGE fournit les equations differentielles lineaires/non lineaires du mouvement du rotor embarque en flexion par rapport au support mobile suppose rigide, qui represente un systeme de coordonnees non inertiel. Les equations du mouvement contiennent des termes parametriques periodiques en raison de la dissymetrie geometrique du rotor et des termes parametrique variables dans le temps en raison des rotations du support. Ces termes parametriques sont consideres comme des sources d’excitation interieure et conduisent a une instabilite dynamique laterale. Dans les applications numeriques proposees, trois configurations de rotor embarque sont analysees. Tout d’abord, un rotor symetrique monte sur des paliers rigides est soumis a un balourd combine avec des mouvements de rotation constante et de translation sinusoidale du support. Ensuite, un rotor avec une dissymetrie geometrique du disque monte sur des paliers rigides est excite par l’effet de balourd et par des mouvements combines de rotation constante et de translation sinusoidale du support. Enfin, un rotor symetrique monte sur des paliers hydrodynamiques est soumis au balourd et aux excitations sinusoidales de rotation ou de translation du support.

https://tel.archives-ouvertes.fr/tel-01082878/document

Stabilité et dynamique non linéaire de rotors embarqués

A hybrid foil-magnetic bearing (HFMB) was successfully studied as a vibration isolator by introducing a sudden imbalance or an unexpected disturbance during turbine/rotor operation. This HFMB is used to achieve stability during transient vibration behavior. The HFMB consists of two oil-free bearing technologies: an active magnetic bearing (AMB) and air foil bearing (AFB). Using both technologies takes advantage of the strengths of each bearing while compensating for their inherent weaknesses. In addition, the HFMB has good dynamic characteristics, and the damping can be adjusted using the appropriate gain selection for the AMB controller. Based on these unique features, dynamic stability can be enhanced, even if a sudden imbalance occurs while the rotor is operating. In this study, a rigid rotor was operated at up to 12,000 rpm and tested using a control algorithm to reduce the sudden imbalance vibration amplitudes. The experiment was conducted under the situation that the mass dropped out at 6,000 rpm. I...

Vibration control of high-speed rotor supported by hybrid foil-magnetic bearing with sudden imbalance

Study on vibration characteristics of fan shaft of geared turbofan engine with sudden imbalance caused by blade off

A shock spectrum procedure is developed to estimate the peak displacement response of linear flexible rotor-bearing systems sugjected to a step change in unbalance (i.e., a blade loss). A progressive and a retrograde response spectrum are established. These blade loss response spectra are expressed in a unique non-dimensional form and are functions of the modal damping ratio and the ratio of rotor spin speed to modal damped whirl speed. Modal decomposition using complex modes is utilized to make use of the unique feature of the spectra for the calculation of the peak blade loss displacement response of the rotor system. The procedure is applied to three example systems using several modal superposition strategies. The results of each are compared to true peak displacement obtained by a separate transient response program.

M. Alam

Papers

A Blade Loss Response Spectrum for Flexible Rotor Systems