Coupled Blade-Disk-Shroud Flutter Instabilities in Turbojet Engine Rotors

1967 ◽  
Vol 89 (3) ◽  
pp. 419-426 ◽  
Author(s):  
F. O. Carta
Keyword(s):  
Energy Method ◽  
Empirical Data ◽  
Parametric Study ◽  
Vibration Modes ◽  
Coupled Vibration ◽  
Flutter Instability ◽  
Rotating Blade ◽  
Turbojet Engine ◽  
High Incidence ◽  
Engine Rotors

An energy method is used to investigate a flutter instability of turbojet engine rotors which is caused by the interactions between unsteady air loading and the coupled vibration modes of the rotating blade-disk-shroud system. It is shown, analytically, in this parametric study that under certain circumstances the coupling between blade modes permits the transfer of energy from the air to the blade-disk-shroud system, giving rise to a self-excited instability. Both unsteady potential flow theory and empirical data for oscillating airfoils at high incidence are used.

scholarly journals A Combined Energy Method for Flutter Instability Analysis of Weakly Damped Panels in Supersonic Airflow

Mathematics ◽  
2021 ◽  
Vol 9 (10) ◽  
pp. 1090
Author(s):  
Xiaochen Wang ◽  
Zhichun Yang ◽  
Guiwei Zhang ◽  
Xinwei Xu
Keyword(s):  
Energy Balance ◽  
Energy Method ◽  
Plate Theory ◽  
Dynamic Pressure ◽  
Physical Nature ◽  
Aeroelastic System ◽  
Dissipation Energy ◽  
Supersonic Airflow ◽  
Flutter Instability ◽  
Modal Damping

A combined energy method is proposed to investigate the flutter instability characteristics of weakly damped panels in the supersonic airflow. Based on the small damping assumption, the motion governing partial differential equation (PDE) of the panel aeroelastic system, is built by adopting the first-order piston theory and von Karman large deflection plate theory. Then by applying the Galerkin procedure, the PDE is discretized into a set of coupled ordinary differential equations, and the system reduced order model (ROM) with two degrees of freedom is obtained. Considering that the panel aeroelastic system is non-conservative in the physical nature, and assuming that the panel exhibits a single period oscillation on the flutter occurrence, the non-conservative energy balance principle is applied to the linearized ROM within one single oscillation period. The obtained result shows that the ROM modal coordinate amplitudes ratio is regulated by the modal damping coefficients ratio, though each modal damping coefficient is small. Furthermore, as the total damping dissipation energy can be eliminated due to its smallness, the He’s energy balance method is applied to the undamped ROM, therefore the critical non-dimensional dynamic pressure on the flutter instability occurrence, and the oscillation circular frequency amplitude relationship (linear and nonlinear form) are derived. In addition, the damping destabilization paradoxical influence on the system flutter instability is investigated. The accuracy and efficiency of the proposed method are validated by comparing the results with that obtained by using Routh Hurwitz criteria.

Coupled vibration modes

1975 ◽  
Vol 38 (1) ◽  
pp. 27-37 ◽  
Author(s):  
J.G.A. Croll
Keyword(s):  
Vibration Modes ◽  
Coupled Vibration

Analysis of coupled vibration modes by use of holographic interferometry and finite elements method

1995 ◽  
Author(s):  
Luigi Balis-Crema ◽  
Michele A. Caponero ◽  
Antonio Castellani ◽  
Alberto De Angelis ◽  
G. Ermio
Keyword(s):  
Finite Elements ◽  
Holographic Interferometry ◽  
Finite Elements Method ◽  
Vibration Modes ◽  
Coupled Vibration

scholarly journals Parametric Study of a Turbojet Engine with Auxiliary Bypass Combustion – The TurboAux Engine

2020 ◽  
Author(s):  
Kaleab Fetahi ◽  
Sharanabasaweshwara Asundi ◽  
Arthur Taylor ◽  
Syed F. Ali ◽  
Adem Ibrahim
Keyword(s):  
Parametric Study ◽  
Turbojet Engine

A Study on Coupled Bending and Torsional Vibrations of Wind Turbine Blades

2012 ◽  
Vol 622-623 ◽  
pp. 1236-1242 ◽  
Author(s):  
Mary V. Bastawrous ◽  
Ayman A. El-Badawy
Keyword(s):  
Wind Turbine ◽  
Parametric Study ◽  
Turbine Blades ◽  
Vibration Modes ◽  
Blade Design ◽  
Wind Turbine Blades ◽  
Analysis Techniques ◽  
Material Stiffness ◽  
Dimensional Parameters ◽  
Collective Influence

A parametric study is developed to investigate the effect of geometry, material stiffness and the rotational motion on the coupled flapwise bending and torsional vibration modes of a wind turbine blade. The assumed modes method is used to discretize the derived kinetic and potential energy terms. Lagrange’s equations are used to derive the modal equations from the discretized terms, which are solved for the vibration frequencies. The parametric study utilizes dimensional analysis techniques to study the collective influence of the investigated parameters by combining them into few non-dimensional parameters, thus providing deeper insight to the physics of the dynamic response. Results would be useful in providing rules and guidelines to be used in blade design.

Stability of Cracked Rotors in the Coupled Vibration Mode

1988 ◽  
Vol 110 (3) ◽  
pp. 356-359 ◽  
Author(s):  
C. A. Papadopoulos ◽  
A. D. Dimarogonas
Keyword(s):  
Harmonic Functions ◽  
Vibration Mode ◽  
Coupling Effect ◽  
Equations Of Motion ◽  
Vibration Modes ◽  
Coupled Vibration ◽  
Compliance Matrix ◽  
Stiffness Coefficients ◽  
Local Flexibility

A transverse surface crack is known to add to a shaft a local flexibility due to the stress-strain singularity in the vicinity of the crack tip. This flexibility can be represented, in the general case by way of a 6 × 6 compliance matrix describing the local flexibility in a short shaft element which includes the crack. This matrix has off-diagonal terms which cause coupling along the directions which are indicated by the off-diagonal terms. In addition, when the shaft rotates the crack opens and closes. Then the differential equations of motion have periodically varying stiffness coefficients and the solution can be expressed as a sum of harmonic functions of time. A method for the determination of the intervals of instability of the first and of second kind is developed. The results have been presented in stability charts in the frequency vs. depth of the crack domain. The coupling effect due to the crack leads to very interesting results such as new frequencies and vibration modes.

Real actuator effects and the aerodynamic energy method

1988 ◽  
Vol 92 (912) ◽  
pp. 77-83 ◽  
Author(s):  
A. Simpson
Keyword(s):  
Energy Method ◽  
Normal Vibration ◽  
Control Law ◽  
Vibration Modes ◽  
Aerodynamic Forces ◽  
Flutter Suppression ◽  
Active Controls

Summary The aerodynamic energy method provides a means of flutter-suppression control-law design based wholly on oscillatory aerodynamic forces on a notional structure with notional normal vibration modes. The method has been proposed as a means of flutter suppression regardless of structural considerations, other than those mentioned. As originally conceived, the method is based upon the assumption of totally irreversible active controls. In this paper, the effects of finite impedance of actuators on the implementation of the method are investigated analytically. The conclusions do not augur well for the method.

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