Pneumatic hammer instability in the aerostatic journal bearing–rotor system: A theoretical and experimental analyses

2020 ◽  
pp. 135065012090810
Author(s):  
Abdurrahim Dal ◽  
Tuncay Karaçay
Keyword(s):  
Dynamic Response ◽  
Journal Bearing ◽  
Instability Region ◽  
Rotor System ◽  
Pneumatic Hammer ◽  
Nonlinear Dynamic Response ◽  
System A ◽  
Differential Transform ◽  
Hole Configuration ◽  
Aerostatic Bearings

In this study, the pneumatic hammer instability phenomena in the aerostatic journal bearing–rotor system is analysed and discussed for different feeding hole configurations theoretically and experimentally. The influences of the configuration of the feeding holes on the nonlinear dynamics of the system are also investigated. The air flow between the surfaces is modelled with Reynold’s equation and it is numerically solved with differential transform and finite difference hybrid method. Three different aerostatic bearings are modelled and simulated to investigate the ınfluences of the configuration of the holes for different angular speeds. An experimental test rig is designed and tested for different rotor speeds to validate the obtained numerical results. The dynamic response of the system is analysed using waterfall plots, bifurcation diagrams, orbit plots, phase portrait and Poincaré map, which are drawn to determine the pneumatic hammer instability region of the modelled system. The results reveal a nonlinear dynamic response of the rotor centre. In addition, the analysis shows that the feeding hole configuration affects the rotor dynamics and the pneumatic hammer instability region.

scholarly journals Influence of roundness error screw on running characteristics of sliding bearing based on SDT

2022 ◽  
Vol 355 ◽  
pp. 01021
Author(s):  
Zhenyu Chen ◽  
Wubin Xu ◽  
Bing Li
Keyword(s):  
Critical Speed ◽  
Journal Bearing ◽  
Rotor System ◽  
Small Displacement ◽  
Promoting Effect ◽  
Sliding Bearing ◽  
Roundness Error ◽  
System A ◽  
Film Characteristics ◽  
Generalized Roundness

In order to study the influence of roundness error on the oil film characteristics of journal bearing rotor system, a dynamic model of journal bearing rotor system with roundness error was established, and a new generalized roundness error equation is derived based on the small displacement screw (SDT) theory. And the influence of roundness error screw parameter dx represented by SDT on critical speed and stability of sliding bearing is analyzed emphatically. The results show that the existence of journal roundness error is beneficial to the bearing capacity and stability of sliding bearing rotor system to a certain extent, and with the increase of roundness error screw parameter, its promoting effect is more obvious; At the same time, the critical speed of the system will increase with the increase of screw parameter, especially when eccentricity ε>0.6; And when Sommerfeld number S>0.6, the roundness error of journal has little influence on stability.

Nonlinear dynamic response and bifurcation of asymmetric rotor system supported in axial-grooved gas-lubricated bearings

2021 ◽  
pp. 146134842110527
Author(s):  
Sha Li ◽  
Yanjun Lu ◽  
Yongfang Zhang ◽  
Hongbo Luo ◽  
Song Wang ◽  
...  
Keyword(s):  
Numerical Model ◽  
Dynamic Response ◽  
Rational Function ◽  
Nonlinear Dynamic ◽  
Rotor System ◽  
Dynamic Responses ◽  
Function Model ◽  
Nonlinear Dynamic Response ◽  
Asymmetric Rotor ◽  
The Rational Function Model

Dynamic characteristics of the asymmetric rotor system supported in axial-grooved gas-lubricated bearings are studied. In order to solve nonlinear dynamic response of rotor system effectively, a hybrid numerical model is established by coupling the motion equation of rotor with the rational function model of the gas film forces. The rational function model of the gas film forces of gas-lubricated bearing is established based on vector fitting theory. By using the hybrid numerical model, the repeated calculations of the unsteady Reynolds equation and gas film forces are avoided; the continuous rotor trajectory and the dynamic gas film forces can be calculated simultaneously; and for the rotor system supported in the same bearings, the computing cost can be saved effectively. The nonlinear dynamic responses of asymmetric rotor system supported in axial-grooved gas-lubricated bearings are investigated by trajectory diagrams, frequency spectrum, Poincaré maps, and time series. The bifurcations are analyzed by the bifurcation diagrams with different rotating speeds and mass eccentricities. The dynamic behaviors of the asymmetric rotor system appear complex nonlinear dynamic phenomenon and specific bifurcation characteristics.

scholarly journals Frequency Enhancement of Oil Whip and Oil Whirl in a Ferrofluid–Lubricated Hydrodynamic Bearing–Rotor System by Magnetic Field with Permanent Magnets

2018 ◽  
Vol 8 (9) ◽  
pp. 1687
Author(s):  
Liao-Yong Luo ◽  
Yi-Hua Fan ◽  
Jyh-Haw Tang ◽  
Ting-Yu Chen ◽  
Nai-Rong Zhong ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Permanent Magnets ◽  
Journal Bearing ◽  
Rotor System ◽  
Hydrodynamic Bearing ◽  
System A ◽  
Oil Whip ◽  
Oil Whirl ◽  
Hydrodynamic Journal Bearing ◽  
Whirl Speed

The article describes the effect of a magnetic field applied to a ferrofluid–lubricated hydrodynamic journal bearing–rotor system. A rotor with a single journal bearing in one end was built to be the test rig. The experimental results showed that 3 to 8 permanent magnets, arranged by different methods, can all increase the instability threshold of the oil bearing. Especially, the magnetic field formed by eight magnets has the optimal effect. The whirl speed and the whip speed can be increased from 3024 rpm to 4480 rpm, and from 3184 rpm to 5268 rpm.

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