Dynamical Simulations of a Flexible Rotor in Cylindrical Uncavitated and Cavitated Lubricated Journal Bearings

Abstract

Due to requirements of their operating conditions, such as high speed, high flexibility and high efficiency, rotating machines are designed to obtain larger operating ranges. These operating conditions can increase the risk of fluid-induced instability. In fact, the presence of non-linear fluid forces when the threshold speed is overcome by the rotational speed, can generate rotor lateral self-excited vibrations known as "oil whirl" or "oil whip". These instabilities derive from the interaction between the rotor and the sliding bearing and they are typically sub-synchronous and they contribute to eventual rubbing between rotor and stator with consequent damage to the rotating machines. For these reasons, the aim of this paper is to numerically investigate the differences in the dynamic behaviour of a flexible rotor supported by cylindrical lubricated journal bearings. The study considers two different cases, uncavitated and cavitated lubricated films, in order to develop an original Matlab-Simulink algorithm for the numerical solution of the differential non-linear equations of motion of the unbalanced flexible rotor supported on hydrodynamic journal bearings. The bearings were modelled as uncavitated and cavitated (π-Film) short bearings derived from classical Reynolds' theory. Dynamic simulation allowed prediction of the shape and size of the orbit performed by the system and evaluation of the vibrating phenomena exerted by the rotor during the motion. The results show that cavitation completely modifies the behaviour of the system in every aspect. The analysis of the diagrams obtained showed that the proposed algorithm provides consistent results and represents a valuable instrument for dynamic analysis of rotating systems.

CFD Analysis of the Eccentricity Ratio on Journal Bearing due to Differences in Lubrication Type

“…The research method used is to use CFD Fluent in ANSYS. The geometry parameters refer to the previous study in table 1, using secondary data from the previous study. The material Babbit alloy uses in bearings [16].…”

“…Journal bearings work only under limited conditions (metal-to-metal contact) during engine start-up and shutdown. Because there is often contact between the two, the lubrication must be good to minimize the occurrence of friction between the journal and the bearing, which results in damage to the journal bearing [1]- [4] Figure 1 shows the basic geometry of the journal bearing in a steady-state configuration. The hydrodynamic movement of the journal bearing causes pressure in the lubrication.…”

The Dynamic Characteristic of a Faulted Rotor System with Multi-Objective Optimization Designed SFD

“…2019, 9, x FOR PEER REVIEW 2 of 15 successfully, the vibration amplitude of the system was reduced by 60%. Considering the effect of the cavitation, Ruggiero et al [4] found the "oil whirl" produced by the non-linear fluid forces. Wang [5] studied a controllable SFD for a rotor system and revealed its effect mechanism.…”

“…Meanwhile, the obtained results were in agreement with the experimental results; when Coorper [3] presented the experimental study on SFD, and applied it to the Conway engine successfully, the vibration amplitude of the system was reduced by 60%. Considering the effect of the cavitation, Ruggiero et al [4] found the "oil whirl" produced by the non-linear fluid forces.…”

Nanofluids for Performance Improvement of Heavy Machinery Journal Bearings: A Simulation Study

“…Hydrodynamic journal bearings have been extensively used in heavy industry machines and turbomachinery [1] to support rotating shafts due to their superior durability, low maintenance cost, and excellent load carrying capacity [2][3][4][5][6]. Journal Bearings are critical components of the tools operating downhole, such as directional drilling (DD) tools that are used in oil and gas exploration and drilling applications.…”