Multilobe Journal Bearings Research Articles

Stability analysis of electrorheological (ER) lubricant operated multilobe hydrodynamic journal bearing

Purpose An electrorheological (ER) fluid consists of dielectric particles blended in a nonconducting oil. ER lubricants are often considered smart lubricants. This paper aims to examine the steady state and dynamic response of multilobe journal bearings using an ER lubricant. Design/methodology/approach Reynold’s equation has been used to describe the lubricant flow in the journal-bearing clearance space. The Bingham model is used to characterize the nonlinear behavior of the lubricant. The solution of the Reynolds equation is obtained using the Newton–Raphson method, with gaseous cavitation in the fluid film numerically addressed by applying a mass-conserving algorithm. The effects of lobe geometry and the applied electric field are investigated on film pressure profile, fluid film thickness, direct stiffness and damping parameters. The equation of motion for journal center coordinates is solved using the fourth-order Runge–Kutta method, to predict journal center motion trajectories. Findings Using ER lubricant combined with two-lobe journal bearing significantly improved the minimum film thickness by 49.75%, the direct stiffness parameter by 132.18% and the damping parameter by 206.3%. However, the multilobe configuration was found to negatively impact the frictional powerloss of the bearing system. In the case of multilobe configurations of journal bearings using ER lubricant, linear motion journal trajectories are observed to be reduced and exhibit increased stability. Originality/value This study presents the effect of an ER lubricant and multilobe configuration on the rotor-dynamic performance and stability analysis of hydrodynamic journal bearings. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-06-2024-0201/

Performance of rough surface hydrodynamic circular and multi-lobe journal bearings in turbulent regimes

This article deals with the steady and dynamic performance analysis of rough surface circular and multi-lobe journal bearings operating with non-Newtonian lubricant in turbulent regimes. The numerical solution of Reynold's equation was obtained using the finite element method. To account for surface roughness, the Patir and Cheng model was used, and fluid turbulent behavior was modeled using the turbulent theory as proposed by Ng and Pan. The non-Newtonian behavior of the lubricant is presented by the Rabinowitsch fluid model, and JFO boundary conditions are used to solve Reynold's equation, considering gaseous cavitation. The bearing with micro-roughness has been considered in numerical analysis and transverse roughness has been reported to improve bearing performance indices. Among the different bearing design configurations, the two-lobe bearing configuration provides significantly improves the minimum film thickness, hydrodynamic pressure, and dynamic parameters. The presence of turbulent flow and transverse surface roughness produces a synergistic effect that enhances the minimum film thickness, stiffness, and damping parameters of journal bearings. This study provides a detailed comparison between various bearing designs and recommends the use of two-lobe bearings for high-speed applications.

Static and stability analysis of partial slip texture multi-lobe journal bearings

This paper presents one-dimensional analysis of modified dynamic Reynolds equation derived for partial slip texture multi-lobe journal bearings. The novelty included in this study is the configuration of partial slip texture region on the bottom bearing lobe surface of a multi-lobe journal bearing under a constant vertical load. The nondimensional pressure and shear stress for steady-state and nondimensional pressure gradients for dynamic coefficients for each lobe with partial slip texture configuration are derived based on narrow groove theory. Linearized stability analysis is evaluated using infinitesimal perturbation method. Results of static and stability characteristics of partial slip texture multi-lobe (two-axial groove, elliptical, three-lobe and offset) journal bearings are presented. Partial slip texture configuration significantly enhances load capacity, coefficient of friction, and stability of two-lobe journal bearing.

Inertia Effects in a Multilobe Conical Bearing Lubricated with a Couple Stress Fluid

In this paper, a multilobe conical bearing is analyzed. A lubricant modelled by a couple stress fluid flows in the bearing clearance. The Galerkin method is used to determine the mechanical parameters of multilobe journal bearings. An example of a two-lobe conical bearing is discussed in detail. The inertia of the flowing lubricant is taken into account in the analysis. It has been found that the increase of the couple stress generates an increase the pressure in the clearance.

Non Linear Analysis on Multi Lobe Journal Bearings

Multi lobe journal bearings are used in machines which operate at high speeds and high loads. In this paper the multi lobe bearing are analyzed to determine the effect of surface roughness during non linear loading. A non-linear time transient analysis is performed using the fourth order Runge Kutta method. The finite difference method is used to predict the pressure distribution over the bearing surface. The effect of eccentric ratio is studied and the variation of attitude angle is discussed. The journal center trajectories were calculated and plotted.

Analysis of the Stability of Elliptical Journal Bearings under Vapor Cavitation Erosion

The phenomenon of lubricant cavitation in hydrodynamic bearings and its effect on the stability has been rigorously studied and reported in the literatures. In certain cases, cavitation has significant effect on the dynamic and stability characteristics of the rotor-bearing system. With a proper control of the cavitation condition and groove location, stability can be achieved over a wide range of operating speed, in the case of elliptical journal bearings. On the other hand, the stability is not affected by the presence of vapor cavitation, in the case of multi-lobe journal bearings with the oil supplied at atmospheric pressure. For the unstable, submerged, circular bearings, vapor cavitation phenomena results in a distinctive vibration response observable on the vibration plots. The stability of the elliptical journal bearings under the influence of vapor cavitation erosion was analyzed. It is found that vapor cavitation erosion on elliptical bearings results in instability of the whirling shaft. Collapse of the vapor cavitation bubbles causes erosion wear that falls within the pressure zone of the elliptical bearing, thus causing the instability.

Experimental study of pressure fields in a multilobe journal bearing

An experimental pressure field in operating clearance and flowrate parameters analysis for different eccentricities, inlet oil pressures, and journal rotating velocities are presented for a radial multilobe journal bearing. Lubricating film breakdown zones in bearing oil ducts caused by complicated construction and journal rotation are observed.

S1160202 製作誤差が多円弧軸受の力学的静特性に及ぼす影響 : パッドの位置に製作誤差を有する場合

S1160202 製作誤差が多円弧軸受の力学的静特性に及ぼす影響 : パッドの位置に製作誤差を有する場合

Pressure distribution for multi-lobe bearings using Fourier analysis

During the past decades, researchers have focused a great deal of attention on the lobe bearings because of their superior stability. In this paper, a comprehensive methodology for determining the performances of bearings is developed based on the Fourier analysis. The advantage of this method is no longer to treat each lobe as an individual partial bearing like before, but to take into account the inherent relevance and coupling effects among lobes, etc. This article firstly puts forward universal frameworks of mathematical procedure, within which two multi-lobe journal bearings, namely, three- and four-lobe bearing are investigated. For the bearings with similar topology structure, the results show that the Fourier expansions of oil-film thickness are composed of the same family of harmonic basis functions. And those functions are merely related to the number of bearing lobes N. The results also show that both the oil-film profile and pressure field of the whole bearing completely inherit the periodicity from the periodic bearing structure and own the same period 2 π/ N commonly. Again, the simulated results construct the corresponding relationship between the expanded terms of oil-film thickness and pressure field. Further, quantitatively analyzing the variations of the pressure component indicates that as the order increases, the maximum of the pressure component decreases gradually. That provides a more convenient approach to obtain a satisfied prediction of the performance of the bearings just by using finite Fourier harmonic terms.

Rotordynamic characteristics of a multilobe hybrid journal bearing in turbulent lubrication

This paper presents an investigation of the rotordynamic behaviour of a four-lobe orifice compensated hybrid bearing. It aims to show that multilobe hybrid journal bearings prove to be a better alternative for high-speed turbo pump applications.

A Methodology for Dynamic Coefficients and Nonlinear Response of Multi-Lobe Journal Bearings

A methodology for prediction of dynamic coefficients and nonlinear simulation of multi lobe bearings is developed. This simple formulation that is an extension of Reason and Narang (1982) approach. An easy to implement finite perturbation method is used to evaluate stiffness and damping coefficients. In order to obtain the fluid film forces, the oil film pressure generated in the bearing is solved using a semi analytical pressure model. Four multi lobe journal bearings, namely: two-axial groove, elliptical, three-lobe and offset bearings are studied in terms of non dimensional stiffness and damping coefficients. The parameters are: L/D ratios of 0.5 and 1.0, pre-load factor of 0.5 and offset factor of 0.5; except for the offset bearing, for which the offset factor is 1.0. The results are provided in graphical form and compared with existing numerical techniques. All the coefficients show the influence of Sommerfeld (long) bearing solution at high eccentricity ratios. Results also indicate the applicable range of reciprocal relationship combining the Ocvirk (short) and Sommerfeld bearing solutions for all multi lobe bearing configurations. The journal center trajectories obtained are compared with numerical results and the effect of stability on rotor bearing system is studied for both balanced and unbalanced rotor. It is concluded that the approximate bearing solutions which are predominantly applied to cylindrical bearing configuration, can also be successfully implemented for noncircular profiles.

An Approximate Solution Technique for Multilobe Journal Bearings Including Thermal Effects, with Comparison to Experiment

An approximate solution method for multilobe journal bearings that includes thermal effect is presented. The method is based on the assumption of an axial pressure distribution in the form of a polynomial, which allows the solution of Reynolds' equation by a one-dimensional finite element routine with little loss in accuracy from two-dimensional methods. A first order form of the energy equation for an adiabatic film is used to predict temperatures within the bearing, and the viscosity is determined as an exponential function of temperature. Comparison of solutions obtained by the variable viscosity method to effective viscosity solutions after Lund and Thomsen illustrates discrepancies in operating eccentricity and stiffness coefficients between the two approaches. Good correlation was obtained between the variable viscosity solutions and experimental measurements reported by Tonnesen and Hansen of eccentricity, pressures, and temperatures in a two-axial groove bearing.

Stability and Transient Characteristics of Four Multilobe Journal Bearing Configurations

Multilobe journal bearings are often used to improve the stability response of rotating machinery. Such machines operate near the stability threshold of the bearing-rotor system. This work determines the linearized stability threshold of four multilobe journal bearings: elliptical, offset elliptical, three lobe, and four lobe. A nonlinear transient analysis of a rigid rotor in each of these bearings is carried out above and below the threshold speed. Shaft orbits and bearing forces are calculated. A numerical fast Fourier transform analysis is used to obtain the frequency content of the nonlinear orbit.

Transient Unbalance Response of Four Multilobe Journal Bearings

This work carries out an analysis of the transient response of four multilobe journal bearings (elliptical, offset, three-lobe, and four-lobe) subject to unbalance both below and above the linearized stability thresholds for the bearings. It extends the work of a previous paper on a balanced rotor in the same four bearing types. Transient orbits, bearing forces, and a numerical fast Fourier transform analysis of the orbits are presented. A comparison of bearing forces above the stability threshold for each bearing indicates that the elliptical bearing has the most violent whirl vibration amplitudes, while the offset bearing exhibits the least amount of subsynchronous vibration.