scholarly journals Dynamical Behavior Analysis of Rubbing Rotor System under Asymmetric Oil Film Force

2019 ◽  
Vol 2019 ◽  
pp. 1-16 ◽  
Author(s):  
Youfu Tang ◽  
Feng Lin ◽  
Qian Zou
Keyword(s):  
Dynamic Behavior ◽  
Dynamic Models ◽  
Journal Bearing ◽  
Dynamic Theory ◽  
Dynamical Behavior ◽  
Rotor System ◽  
System Response ◽  
Oil Film ◽  
Rotor Structure ◽  
Rotor Dynamic

Rubbing is one of the most common and significant faults that exist in the rotor system. It exhibits extremely complicated dynamic behavior. Existing dynamic models are primarily based on the symmetrical rotor structure, in which the oil film forces at both ends of support are considered identical. However, in practice, the oil film force may be differently affected by multiple factors (e.g., viscosity of lubricants, the thickness of oil film, and clearance of journal bearing). In this study, a novel dynamic model of the rubbing rotor system under asymmetric oil film force was developed. Furthermore, based on the nonlinear rotor dynamic theory, its dynamic behavior with different parameters was analyzed, and the corresponding chaotic features were extracted. The results indicated that the evolution law of chaotic motion was more complicated, and the chaotic region of system response was obviously wider under the asymmetric oil film force than the symmetrical oil film force.

Dynamic Behavior Analysis of Three-Span Rotor-Bearing System with Rub-Impact Fault

2012 ◽  
Vol 460 ◽  
pp. 160-164 ◽  
Author(s):  
Song He Zhang ◽  
Yue Gang Luo ◽  
Bin Wu ◽  
Bang Chun Wen
Keyword(s):  
Nonlinear Dynamics ◽  
Behavior Analysis ◽  
Dynamic Model ◽  
Dynamic Behavior ◽  
Rotor System ◽  
System Response ◽  
Rotor Bearing ◽  
Set Up ◽  
Bearing System ◽  
Main Influence

The dynamic model of the three-span rotor-bearing system with rub-impact fault was set up. The influence to nonlinear dynamics behaviors of the rotor-bearing system that induced by rub-impact of one disc, two discs and three discs were numerically studied. The main influence of the rotor system response by the rub-impact faults are in the supercritical rotate speed. There are mutations of amplitudes in the responses of second and third spans in supercritical rotate speed when rub-impact with one disc, and there are chaotic windows in the response of first span, and jumping changes in second and third spans when rub-impact with two or three discs.

Nonlinear Dynamic of a Geared Rotor System With Nonlinear Oil Film Force and Nonlinear Mesh Force

2012 ◽  
Vol 134 (4) ◽  
Author(s):  
Yahui Cui ◽  
Zhansheng Liu ◽  
Yongliang Wang ◽  
Jianhuai Ye
Keyword(s):  
Numerical Integration ◽  
Dynamic Model ◽  
Rotational Speed ◽  
Nonlinear Dynamic ◽  
Journal Bearing ◽  
Rotational Frequency ◽  
Rotor System ◽  
Dynamic Responses ◽  
Oil Film ◽  
Gear Mesh

To investigate the effect of oil film force on a geared rotor system, a short journal bearing model was applied to represent nonlinear oil film force. A dynamic model of the geared rotor oil journal bearing system was presented. The nonlinear gear mesh force and nonlinear oil film force were considered in the model. The nonlinear dynamic responses of the system were investigated by numerical integration method. This article shows that when the rotational speed is relatively low, the vibration of the system is mainly affected by nonlinear mesh force. With the increase of rotational speed, the influence of nonlinear oil film force also increases gradually, and the subsynchronous forward precession phenomena appear. When the speed increases to a certain value, the amplitude of the subsynchronous forward precession exceeds the amplitude of the rotational frequency, and the nonlinear mesh force is greatly affected by the nonlinear oil film force. However, the linear oil film force does not affect the nonlinear mesh force. The subsynchronous forward precession is difficult to be predicted by linear oil film force which was previously applied. This experiment is performed to validate the correctness of the dynamic model presented, and the numerical integration results of low speeds are validated by the experimental data.

Study on Subsynchronous Vibration With Tilting Pad Journal Bearing Under Starved Lubrication

2018 ◽  
Author(s):  
Rimpei Kawashita ◽  
Tadasuke Nishioka ◽  
Shimpei Yokoyama ◽  
Makoto Iwasaki ◽  
Shuichi Isayama ◽  
...  
Keyword(s):  
Flow Rate ◽  
Journal Bearing ◽  
Damping Ratio ◽  
Leading Edge ◽  
Rotor System ◽  
Experimental Results ◽  
Oil Film ◽  
Tilting Pad ◽  
Oil Flow ◽  
Starved Lubrication

Industrial machines such as gas and steam turbines require high efficiency and reliability. Direct lubricated bearings have been developed and installed to reduce mechanical losses. In recent years, it has been reported in the literature that subsynchronous vibration can occur to rotor shafts with direct lubricated tilting pad journal bearings under reduced oil flow rate conditions. In this study, a test rig with a 200 mm diameter and 3.5 meter long rotor supported by a direct lubricated tilting two pad journal bearing was constructed. The primary critical speed is 2100rpm and rotational speed is 3600rpm. The oil-starved area, the non-oil film layer region at the leading edge of the bearing pads, was measured by observing oil film pressure in the bearing clearance with pressure transducers on the rotor surface. A sine sweep excitation test was carried out by using an inertial shaker installed on the bearing housing and the damping ratio of the rotor system was measured. Measured data showed that a larger starved area at the leading edge of the bearing pads due to reduced oil feeding results in a smaller damping ratio, and an increase in the natural frequency of the rotor. Experimental results of two types of oil feeding nozzles were compared with respect to the correlation between starved area and damping ratio of the rotor system, and a relationship between oil flow rate and starved area was discussed. A method for modeling bearing coefficients under starved lubrication has been proposed based on thermo-hydrodynamic lubrication (THL) analysis. A numerical analysis of a finite element-transfer matrix model of the test rotor with the bearing coefficients calculated by the proposed method is carried out, and it is found that the analytical results are in broad agreement with the experimental results.

Influence of Fluid Film Boundary Migration on Dynamic Coefficients of Journal Bearings and Behavior of Rotor System

2020 ◽  
Vol 142 (10) ◽  
Author(s):  
Changmin Chen ◽  
Jianping Jing ◽  
Jiqing Cong ◽  
Zezeng Dai ◽  
Jianhua Cheng
Keyword(s):  
Journal Bearing ◽  
Boundary Migration ◽  
Dynamical Behavior ◽  
Journal Bearings ◽  
Rotor System ◽  
Fluid Film ◽  
Dynamic Coefficients ◽  
Film Boundary ◽  
Rotor Bearing ◽  
Stiffness And Damping

Abstract The position of fluid film in journal bearing will change while the journal moving in bearing, which can be named fluid film boundary migration (FFBM). It is usually ignored in the calculation of linear dynamic coefficients. While, the errors brought by this neglection was not ever investigated in detail. In this paper, the influence of FFBM on bearing dynamic coefficients and rotor system dynamic behaviors are investigated. A new perturbation-based model is proposed to take the FFBM into account by modifying the boundary conditions of governing equations. It is then verified by the experimental results and analytical results from previous research. Furthermore, the effects of FFBM on stiffness and damping in two typical journal bearings are investigated. The result indicates that the FFBM has a significant influence on dynamic coefficients of full circular journal bearing but little impact on journal bearing with axial grooves. Moreover, it affects the stiffness and damping more significantly in the cases of large length-to-diameter ratios or small eccentricity ratios in full circle bearing. Finally, the dynamical behavior of a rotor-bearing system with considering the FFBM is also investigated. The result shows that the FFBM of oil film has remarkable influences on the instability threshold and imbalance responses of the rotor system, which should not be ignored. The conclusions obtained in this research are expected to be helpful for the design of full circular journal bearings or rotor-bearing systems.

Development of a Set of Equations for Incorporating Disk Flexibility Effects in Rotordynamic Analyses

1993 ◽  
Vol 115 (2) ◽  
pp. 227-233 ◽  
Author(s):  
G. T. Flowers ◽  
S. G. Ryan
Keyword(s):  
Dynamic Behavior ◽  
Equations Of Motion ◽  
Rotor System ◽  
Rotor Speed ◽  
Disk System ◽  
Rigid Disk ◽  
First Order ◽  
Transverse Vibrations ◽  
Rotor Dynamic ◽  
Sample System

Rotordynamic equations that account for disk flexibility are developed. These equations employ free-free rotor modes to model the rotor system. Only transverse vibrations of the disks are considered, with the shaft/disk system considered to be torsionally rigid. Second-order elastic foreshortening effects that couple with the rotor speed to produce first-order terms in the equations of motion are included. The approach developed in this study is readily adaptable for usage in many of the codes that are currently used in rotordynamic simulations. The equations are similar to those used in standard rigid disk analyses but with additional terms that include the effects of disk flexibility. An example case is presented to demonstrate the use of the equations and to show the influence of disk flexibility on the rotor dynamic behavior of a sample system.

scholarly journals Dynamic Behavior Analysis of Intermediate Bearing-Squeeze Film Dampers-Rotor System under Constant Maneuvering Overload

2021 ◽  
Vol 2021 ◽  
pp. 1-24
Author(s):  
Nan Zheng ◽  
Mo-li Chen ◽  
Gui-Huo Luo ◽  
Zhi-Feng Ye
Keyword(s):  
Dynamic Behavior ◽  
Dynamic Characteristics ◽  
Rotor System ◽  
Squeeze Film ◽  
Nonlinear Dynamic Model ◽  
Maneuvering Flight ◽  
Squeeze Film Dampers ◽  
Frequency Components ◽  
Simulation Results ◽  
Rotor Dynamic

Under the flight maneuvering of an aircraft, the maneuvering load on the rotor is generated, which may induce the change of dynamic behavior of aeroengine rotor system. To study the influence on the rotor dynamic behavior of constant maneuvering overload, a nonlinear dynamic model of bearing-rotor system under arbitrary maneuver flight conditions is presented by finite element method. The numerical integral method is used to investigate the dynamic characteristics of the rotor model under constant maneuvering overload, and the simulation results are verified by experimental works. Based on this, the dynamic characteristics of a complex intermediate bearing-squeeze film dampers- (SFD-) rotor system during maneuvering flight are analyzed. The simulation results indicate that the subharmonic components are amplified under constant maneuvering overload. The amplitude of the combined frequency components induced by the coupling of the inner and outer rotors is weakened. The static displacements of the rotor caused by the additional excitation force are observed. Besides, the period stability of the movement of the rotor deteriorates during maneuver flight. The design of counterrotation of the inner and outer rotors can effectively reduce the amplitude of subharmonic under constant maneuvering overload.

Study on Coupling Fault Dynamics of Sliding Bearing-Rotor System

2019 ◽  
Vol 14 (4) ◽  
Author(s):  
Yang Liu ◽  
Xicheng Xin ◽  
Yulai Zhao ◽  
Shuaishuai Ming ◽  
Yaxin Ma ◽  
...  
Keyword(s):  
Dynamic Behavior ◽  
Frequency Band ◽  
Rotor System ◽  
Sliding Bearing ◽  
Oil Film ◽  
Film Instability ◽  
Augmented Lagrange Method ◽  
Main Fault ◽  
Fault Dynamics ◽  
Coupling Fault

The phenomenon of oil film oscillation and frequency locked may occur in a healthy rotor system which is supported by sliding bearing. The dynamic behavior of the rotor system with misalignment and rubbing coupling fault supported by sliding bearing is also very complex. To solve the problem of fault diagnosis in this case, a dynamical model of rotor system is proposed in this paper. The short bearing oil film force, the equivalent misalignment moment, and Hertz contact theory are applied to establish the model. For rubbing faults, the Augmented Lagrange method is used to deal with the contact constraints to ensure that the boundary penetration depth is within the specified tolerance range. Furthermore, the dynamic behavior of the faulty rotor system under different rubbing stiffness conditions is analyzed in this paper. Meanwhile, the fault signal is divided into equal-band by the wavelet basis functions to find out the fault frequency band of the rotor system. Finally, the accuracy of the simulation study is verified by measurements obtained from the faulty rotor test platform. The following findings are made in this paper. The rubbing fault is dominant in the coupling fault. With the increasing of the speed, the frequency components of the system are dominated by high frequency. The double frequency is the main fault feature frequency band. It can be seen that the rotor system moves gradually from a quasi-periodic state into chaos due to the Lyapunov exponent. At the same time, due to the effects of misalignment moment and friction force, the phenomenon of oil film instability is partially suppressed. The lagging of the first and second-order oil film oscillations occurs.

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