scholarly journals Nonlinear dynamic analysis of a hybrid squeeze-film damper-mounted rigid rotor lubricated with couple stress fluid and active control

2010 ◽  
Vol 34 (9) ◽  
pp. 2493-2507 ◽  
Author(s):  
Cai-Wan Chang-Jian ◽  
Her-Terng Yau ◽  
Jiann-Lin Chen
Keyword(s):  
Dynamic Analysis ◽  
Active Control ◽  
Nonlinear Dynamic ◽  
Couple Stress ◽  
Nonlinear Dynamic Analysis ◽  
Couple Stress Fluid ◽  
Squeeze Film ◽  
Rigid Rotor ◽  
Squeeze Film Damper

Subharmonic and Chaotic Motions of a Hybrid Squeeze-Film Damper-Mounted Rigid Rotor With Active Control

2002 ◽  
Vol 124 (2) ◽  
pp. 198-208 ◽  
Author(s):  
Chieh-Li Chen ◽  
Her-Terng Yau ◽  
Yunhua Li
Keyword(s):  
Lyapunov Exponent ◽  
Active Control ◽  
Chaotic Motion ◽  
Numerical Results ◽  
Operating Conditions ◽  
Squeeze Film ◽  
Speed Ratio ◽  
Maximum Lyapunov Exponent ◽  
Rigid Rotor ◽  
Squeeze Film Damper

The hybrid squeeze-film damper bearing with active control is proposed in this paper. The pressure distribution and the dynamics of a rigid rotor supported by such bearing are studied. A PD (proportional-plus-derivative) controller is used to stabilize the rotor-bearing system. Numerical results show that, due to the nonlinear factors of oil film force, the trajectory of the rotor demonstrates a complex dynamics with rotational speed ratio s. Poincare´ maps, bifurcation diagrams, and power spectra are used to analyze the behavior of the rotor trajectory in the horizontal and vertical directions under different operating conditions. The maximum Lyapunov exponent and fractal dimension concepts are used to determine if the system is in a state of chaotic motion. Numerical results show that the maximum Lyapunov exponent of this system is positive and the dimension of the rotor trajectory is fractal at the nondimensional speed ratio s=3.0, which indicate that the rotor trajectory is chaotic under such operation condition. In order to avoid the nonsynchronous chaotic vibrations, an increased proportional gain is applied to control this system. It is shown that the rotor trajectory will leave chaotic motion to periodic motion in the steady state under control action.

scholarly journals Dynamic Analysis of Squeeze Film Damper Supported Rotors Using Equivalent Linearization

1993 ◽  
Author(s):  
A. El-Shafei ◽  
R. V. Eranki
Keyword(s):  
Dynamic Analysis ◽  
Numerical Integration ◽  
Dynamic Characteristics ◽  
Nonlinear Dynamic Analysis ◽  
Least Square ◽  
Squeeze Film ◽  
Equivalent Linearization ◽  
Squeeze Film Damper ◽  
Elliptic Orbits ◽  
Rotor Dynamic

The technique of equivalent linearization is presented in this paper as a powerful technique to perform nonlinear dynamic analysis of squeeze film damper (SFD) supported rotors using linear rotordynamic methods. Historically, it is customary to design squeeze film dampers (SFDs) for rotordynamic analysis by assuming circular centered orbits, which is convenient in making the nonlinear damper coefficients time independent and thus can be used in an iterative approach to determine the rotor dynamic characteristics. However, the general synchronous orbit is elliptic in nature due to possible asymmetry in the rotor support. This renders the nonlinear damper coefficients time dependent which would require extensive numerical computation using numerical integration to determine the rotor dynamic characteristics. Alternatively, it is shown that the equivalent linearization, which is based on a least square squares approach, can be used to obtain time independent damper coefficients for SFDs executing eccentric elliptic orbits which are nonlinear in the orbit parameters. The resulting equivalent linear forces are then used in an iterative procedure to obtain the unbalance response of a rigid rotor-SFD system. Huge savings over numerical integration are reported for this simple rotor. The technique can be extended to be used in conjunction with currently available linear rotordynamic programs to determine the rotor dynamic characteristics through iteration. It is expected that for multi-rotor multi-bearing systems this technique will result in even more economical computation.

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