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The purpose of this work is to examine the effects of wear severity on the static and dynamic characteristics of journal bearings, and on the vibration response of a rigid rotor supported by journal bearings. Numerical simulations using MATLAB was conducted for three different operating regimes, namely low loaded operating regime ( ϵ 0 = 0.15 ), moderately loaded operating regime ( ϵ 0 = 0.45 ) and highly loaded operating regime ( ϵ 0 = 0.75 ) with wear depth parameter ratio ( δ ) varied from 0 to 0.5 at increments of 0.1. Numerical results showed that the vibration response of the rotor generally increases with the increase of the wear depth for all cases of low, moderately and highly loaded operating regimes of the bearings. For the values of parameters considered in this work, it was shown that the vibration response amplitude of the rotor in worn journal bearings may be six times larger compared to the response amplitude of the rotor in non-worn bearings.

The use of planetary gear stages intends to increase power density in drive trains of rotating machinery. Due to lightweight requirements on this type of machine elements, structures are comparably flexible while mechanical loads are high. This study investigates the impact of structure deformation on sliding planet gear bearings applied in the planetary stages of wind turbine gearboxes with helical gears. It focuses on three main objectives: (i) development of a procedure for the time-efficient thermo-elasto-hydrodynamic (TEHD) analysis of sliding planet gear bearing; (ii) understanding of the specific deformation characteristics of this application; (iii) investigation of the planet gear bearing’s modified operating behavior, caused by the deformation of the sliding surfaces. Generally, results indicate an improvement of predicted operating conditions by consideration of structure deformation in the bearing analysis for this application. Peak load in the bearing decreases because the loaded proportion of the sliding surface increases. Moreover, tendencies of single design measures, determined for rigid geometries, keep valid but exhibit significantly different magnitudes under consideration of structure deformation. Results show that consideration of structure flexibility is essential for sliding planet gear bearing analysis if quantitative assertions on load distributions, wear phenomena, and interaction of the bearing with other components are required.

High-pressure pump rotors are critical components in a wide range of industrial and mechanical systems, including turbomachinery, hydraulic systems, and aviation engines. This study presents a dynamic model for a single-stage high-speed high-pressure centrifugal pump supported by hydrodynamic journal and thrust bearings. The model is based on a rigid rotor framework and incorporates the coupling effects between the journal and thrust bearings. The influence of key bearing parameters is systematically investigated, with particular attention given to the impact of introducing a central groove in the left bearing. Furthermore, the analysis explores the effects of integrating a third central journal into the system which acts also as rear wear ring. The study also examines the role of bearing boundary conditions, which can be regulated through auxiliary lines, and evaluates the influence of unbalance forces on system performance. The results demonstrate that boundary conditions significantly affect the load-carrying capacity and stability of the bearings, potentially leading to bearing failure if not properly managed. Additionally, while a coupling effect between the journal and thrust bearings is observed, its influence is found to be relatively minor in the context of the rigid rotor model employed in this analysis. The findings of this study provide valuable insights for the design and optimization of high-speed centrifugal pumps, offering a deeper understanding of the dynamic interactions and operational constraints inherent in such systems.

Influence of turbulence on the stability characteristics of a water lubricated journal bearing is analyzed. Locus of the journal centre is plotted using the non – linear transient analysis method for different flow regimes of the bearing subjected to three different types of loading. The bearing groove angles of 18 o and 36 o is considered for the analysis. Turbulent coefficients are incorporated in the modified form of Reynolds equation which is solved using the 4th order Runge-Kutta method. The path traversed by journal centre is generated for different loading conditions and the stability of the bearing is examined. For periodic and fluctuating rotating loads, the journal centre traversed shorter path and reached stable position when the flow regime changed from laminar to turbulent.

One of the outstanding advantages of aerostatic bearing is high speed, which is the basic component for various ultra-precision machining. Compared with thrust bearing, journal bearing is less studied and more complex. Structural parameters have great influences on the static properties of the bearing. However, due to the strong coupling, the study of the structural parameters on the bearing dynamic properties at high speed is insufficient. The fluid–structure interaction model of the bearing is formed by directly combining the pressure distribution equations of the gas film, the spindle motion equation, and the flow balance equations. The coupled equations are numerically solved using the two-way alternating implicit scheme method, the Newton iteration method, the Thomas algorithm, and the Newmark method. The influences of orifice diameter, bearing clearance, recess length, and recess height on the dynamic properties of the system are investigated. The results show that the structural parameters play a prominent influence on the bearing flow field and the spindle motion. With the change of the structural parameters, the system appears as T-periodic motion, multiple T-periodic motion, and quasi-periodic motion. The research contributes to the structural optimization and performance enhancement of aerostatic journal bearing.

Hydrodynamic journal bearings are used in many applications which involve high speeds and loads. However, they are susceptible to oil whirl instability, which may cause bearing failure. In this work, a flexible Jeffcott rotor supported by two identical journal bearings is used to investigate the stability and bifurcations of rotor bearing system. Since a closed form for the finite bearing forces is not exist, nonlinear bearing stiffness and damping coefficients are used to represent the bearing forces. The bearing forces are approximated to the third order using Taylor expansion, and infinitesimal perturbation method is used to evaluate the nonlinear bearing coefficients. The mesh sensitivity on the bearing coefficients is investigated. Then, the equations of motion based on bearing coefficients are used to investigate the dynamics and stability of the rotor-bearing system. The effect of rotor stiffness ratio and applied load on the Hopf bifurcation stability and limit cycle continuation of the system are investigated. The results of this work show that evaluating the bearing forces using Taylor’s expansion up to the third-order bearing coefficients can be used to profoundly investigate the rich dynamics of rotor-bearing systems.

This paper presents the performance analysis for plain and elliptical journal bearing operating with industrial lubricants. Titanium dioxide nanoparticle of size 40 nm is used as a lubricant additive to examine the performance of the bearing. Comparative analysis is carried out for three different lubricants with titanium dioxide (0.5% wt) nanoparticles. Performance of bearing is measured at speeds ranging from 500 r.p.m. to 1000 r.p.m. and at 1000 N load. The study of antiwear and antifriction properties for lubricants is carried out on four ball Tribo-tester for operating conditions specified by ASTM standards. An influence of titanium dioxide as an additive on the performance characteristics of the journal bearing such as pressure distribution, load carrying capacity, attitude angle, power loss, oil flow rate, side leakage, frictional force and temperature rise in a film is examined in this paper. The elliptical journal bearing improves the performance of a system over plain bearing operating with the same lubricant.

A novel shallow oil chamber hybrid journal bearing with adjustable oil chamber depth was designed based on piezoelectric ceramics, inspired by conventional shallow oil chamber bearing structures. The computational fluid dynamics method is used to analyze the bearing characteristics of shallow oil chamber bearings, including the volume flow, the seal oil pressure, load capacity and stiffness. An experimental platform equipped with signal acquisition device and piezoelectric ceramic control device was developed. The eddy current sensors collected the displacement signal at the shaft end. The required voltage was calculated by the displacement signal. The piezoelectric ceramics elongated or shortened, causing a displacement of the same magnitude in the depth of the oil chamber, thereby controlling the radial displacement of the shaft. The adjustment effect of this bearing was verified by experiment for no-load and 500 N load at 200–1000 rpm, with a baseline initial oil chamber depth of 20 and an oil supply pressure of 2 MPa. The results showed that compared with the case without adjustment, the accuracy in Y direction has increased from 8.9 μm to 1.9 μm (max. 78.4%) after adjustment. Under the above load conditions, the displacement can be controlled below 2 μm, indicating a significant improvement in shaft vibration resistance.

Journal misalignment and cavitation effects can significantly affect the dynamic performance of bearings. In this study, the Reynolds equation considering mass conservation is adopted to consider the cavitation effect, and the effects of different misalignment angles on the bearing lubrication performance are investigated, including BLC (bearing load-carrying capacity), MOP (maximum oil film pressure), FC (friction coefficients), SAA (stabilized attitude angle), SC (stiffness coefficient), DC (damping coefficient), and stability margin. The model’s precision is validated through a comparison between experimental findings and published studies. The results demonstrate that journal misalignment significantly increases the dynamic performance of the bearings and improves the stability. While cavitation effect reduces the BLC and adversely affects the stability. The obtained results are crucial for the optimal design of bearing structures and the enhancement of their stability.

The spiral-grooved structure has been proposed for promoting the load capacity and stiffness of hybrid air journal bearings. In this paper, the dynamic characteristics of spiral-grooved hybrid bearings are first calculated. The stability criteria of the bearings are proposed and analyzed with different groove structure parameters using frequency domain analysis. It is found that the length of the spiral-groove has significant influence on the stability of the spindle system. Finally, the critical speed of the spiral-grooved hybrid bearing and rotor system is analyzed, and an experiment is carried out to validate the proposed model, finding that groove structure can promote the stability of the air bearing systems.