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Ground resonance is an aero-mechanical instability that occurs in soft in-plane rotors where there is a coalescence of low frequency lead-lag motions of the blade with that of the frequencies of the fuselage, when on ground. Such a coalescence results in violent oscillations of the fuselage and can prove catastrophic to the helicopter if not reduced in time. The present work focuses on a nonlinear...
A novel and universal computational method is proposed to obtain the dynamic stiffness and damping coefficients of the fixed-tilting pad mixture bearing. The dynamic analysis is carried out on the performance of the mixture bearing used in some F type heavy-duty gas turbine, and the influence of bearing parameters such as eccentricity and perturbation frequencies on those dynamic coefficients is studied.
The flywheel energy storage technology is a new type of conversion and storage for electric energy, and it is also a research hotspot of energy field in the world. There are a large number of studies on dynamic characteristics of energy storage flywheel in recent years. The flexible support with a single point has small load-carrying ability but very low friction loss, which is appropriate to be used...
According to structure characteristics of tilting pad bearing and direct lubricating technology, a new three-pad Leading Edge Groove (LEG) tilting pad bearings was developed. In order to investigate performance of the tilting pad bearing dynamic properties, A test rig was developed to test 8 stiffness and damping coefficients for the tilting pad bearing. The finite difference algorithm is adopted...
Undesired vibrations due to mechanical imbalance is an inevitable phenomenon related to high speed rotating systems. In the absence of radial asymmetry, the steady state response of the rotor can be represented as a synchronous forward circular whirling motion. In this motion, the mass elements of the rotor do not carry relative accelerations since they all orbit in a circular motion of a constant...
In this paper, the unbalanced magnetic pull and eccentric mass force which caused vibration of the rotor are introduced. The virtual displacement method is employed to solve the two kinds of force. The inherent characteristics of rotor are analyzed through finite element method and experiment. The dynamic response and axis locus of rotor under the action of unbalanced magnetic pull and eccentric mass...
For a given structure, rotor's natural frequencies are closely related with the supporting stiffness of the rotor. To some extend, the supporting stiffness determines whether the rotor can avoid resonance phenomenon. Using the ANSYS, this paper studied the rotor's vibration characteristics and the characteristics of bearing instability by changing the LP rotor supporting stiffness of an ultra-supercritical...
The problems existing in the traditional absorber can be solved better by adopting clearance control magnetic dynamic absorber to control the imbalance vibration of rotors. For the special structure of conical electromagnet, stiffness and damping formulas of the electromagnetic dynamic absorber are derived when the current source is taken as the power of the electromagnet, and the law of influence...
During line or converter operation dynamic torques in the air gap of asynchronous machines may occur, caused by e.g. faults or by switching operations. The dynamic torques cause dynamic foundation forces, which load the foundation. Therefore the foundation of the machine has to resist these dynamic foundation forces, but also influences the dynamic foundation forces. In this paper a theoretical method...
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